Abstract

Food and fermentation processing must satisfy several competing objectives at the same time. A successful operation controls microorganisms and enzymes while retaining flavor, color, nutrients, protein functionality, emulsion stability, and the required rheology. Conventional plants therefore combine mixers, mills, homogenizers, heat exchangers, deaerators, fermenters, separators, and holding tubes. Hydrodynamic cavitation provides a process intensification option because one compact flow device can generate pressure oscillation, cavity growth and collapse, localized shear, microjets, turbulence, interfacial renewal, gas dispersion, particle disruption, and viscous heating within the same circulation loop [1 to 8].

12. Food and Fermentation Processing

12.1 Introduction

Food and fermentation processing must satisfy several competing objectives at the same time. A successful operation controls microorganisms and enzymes while retaining flavor, color, nutrients, protein functionality, emulsion stability, and the required rheology. Conventional plants therefore combine mixers, mills, homogenizers, heat exchangers, deaerators, fermenters, separators, and holding tubes. Hydrodynamic cavitation provides a process intensification option because one compact flow device can generate pressure oscillation, cavity growth and collapse, localized shear, microjets, turbulence, interfacial renewal, gas dispersion, particle disruption, and viscous heating within the same circulation loop [1 to 8].

The value of hydrodynamic cavitation does not arise from one universal mechanism. In beer and corn mash, the principal opportunities are particle disintegration, extraction, starch accessibility, and volumetric heating. In juice and milk, the critical responses may be cloud stability, fat globule or pulp particle size, enzyme activity, and microbial reduction. In liquid egg, ice cream, mayonnaise, and salad dressing, the key functions are controlled homogenization, powder hydration, emulsification, and protection of heat sensitive proteins. The acceptable process window is therefore product specific, and a pressure drop or rotor speed cannot be transferred directly between products or devices [3,6,7].

This chapter emphasizes engineering interpretation and validation. Every treatment should be described by device geometry, pressure reference locations, flow rate, number of passes, residence time distribution, inlet and outlet temperature, energy input, dissolved gas condition, solids loading, viscosity, and downstream holding or separation. Microbial control require challenge studies with defined target organisms and validation of the combined cavitation, temperature, gas, and holding history. Quality require complete distributions, mass balances, storage studies, and appropriate untreated and conventional process controls.

12.2 Food Specific Process Metrics and Kinetics

The common hydraulic descriptors, bubble dynamics relations, equipment families, and energy definitions are consolidated in Section 2.7 and Chapter 5. The relations retained here are those needed to interpret food specific microbial, enzymatic, extraction, texture, and quality responses.

12.2.1 Microbial, enzymatic, extraction, and quality kinetics

Microbial and enzyme responses are usually nonlinear because cavitation modifies temperature, aggregation state, membrane permeability, and mass transfer at the same time. A log reduction must therefore be tied to the complete time temperature pressure history and the initial population. Mild cavitation can disaggregate cell clusters and make microorganisms more accessible to heat or dissolved carbon dioxide, while high severity can directly damage cell walls and membranes. Conversely, entrained gas can cushion collapse and reduce mechanical lethality [19,20,25 to 27].

Extraction benefits arise from reduced particle size, broken cell walls, renewed liquid films, and rapid removal of solubilized material from the surface. The same mechanisms can release oxidative enzymes, cause excess fines, or increase downstream separation difficulty. Optimal treatment is therefore commonly observed before the maximum energy input. Orange juice, ice cream, dairy proteins, soy slurry, and corn mash all show evidence that additional passes or treatment time can eventually reduce quality or separation efficiency [21,28 to 31,35,40].

$$LR={\log }_{10}\left(\frac{N_0}{N}\right)$$

(12.1)

where LR is microbial log reduction, $N_0$ is the initial viable population, and N is the population after treatment. The analytical detection limit must be stated.

$$\frac{N}{N_0}=\exp (-kt)$$

(12.2)

where k is an apparent first order inactivation constant. This model is convenient for screening, but shoulders, tails, subpopulation differences, and time varying temperature may require more advanced models.

$$k(T)=k_0\exp (-\frac{E_a}{RT})$$

(12.3)

where $k_0$ is the pre exponential factor, $E_a$ is apparent activation energy, R is the universal gas constant, and T is absolute temperature. A cavitation assisted treatment may change both the apparent kinetic constant and the effective thermal history.

$$C(t)=C_{\infty }[1-\exp (-k_{L}at)]$$

(12.4)

where C(t) is the extracted or dissolved concentration, $C_{\infty }$ is the asymptotic concentration, and $k_{L}a$ is an overall mass transfer coefficient times specific interfacial area. Cavitation can raise $k_{L}a$ by increasing turbulence and area.

12.2.2 Hydraulic, thermal, and residence time descriptors

Pressure alone is not a transferable measure of cavitation severity. Food applications should report the pressure reference locations, local velocity, vapor pressure, flow rate, active volume, treatment time, number of passes, temperature history, and the energy boundary used for the calculation. These descriptors support comparison among Venturi, orifice, vortex, and rotor devices while recognizing that equal dimensionless numbers do not guarantee equal product response [6 to 8,63].

$$C_v=\frac{P_2-P_v}{0.5\rho V_t^2}$$

(12.5)

where Cᵥ is cavitation number, P₂ is the fully recovered downstream pressure, Pᵥ is liquid vapor pressure at the measured temperature, ρ is density, and Vₜ is mean velocity at the active restriction. The exact pressure locations must be stated.

$$P_h=Q\mathrm{\Delta }P$$

(12.6)

where Pₕ is hydraulic power delivered across the active pressure drop, Q is volumetric flow rate, and ΔP is the measured pressure difference. Pump input power is larger than Pₕ because pump and drive efficiencies are below unity.

$$E_s=\frac{P_{h}t}{m}=\frac{\mathrm{\Delta }PQt}{m}$$

(12.7)

where Eₛ is specific hydraulic energy, t is treatment time, and m is treated product mass. For a continuous single pass process, m is the mass that crosses the device during the selected accounting interval.

$$n_p=\frac{Qt}{V_L}$$

(12.8)

where nₚ is nominal pass count and Vₗ is the liquid inventory in the recirculation loop. This relation does not replace residence time distribution measurement when short circuiting, dead zones, or broad mixing times are possible.

$$\bar{\tau }=\frac{V_a}{Q}$$

(12.9)

where τ̄ is mean nominal residence time in the active device and Vₐ is active internal volume. The local bubble lifetime and high stress exposure are normally much shorter than the bulk residence time.

$$\mathrm{\Delta }{T}_{ad}=\frac{E_s}{c_p}$$

(12.10)

where ΔTₐd is the ideal adiabatic temperature rise and cₚ is product specific heat capacity. The measured temperature rise will differ because of vessel heat loss, cooling, phase change, and energy dissipated outside the product.

$$We=\frac{\rho u_{rel}^{2}d}{\gamma }$$

(12.11)

where We is Weber number, uᵣₑₗ is a representative relative velocity, d is a droplet, bubble, or particle length scale, and γ is interfacial tension. Values above the applicable breakup threshold favor deformation and fragmentation, but concentrated food systems require formulation specific validation.

For microbial or enzyme claims, hydraulic descriptors must be paired with the complete temperature and holding history. For emulsification and particle processing, they must be paired with the complete distribution, not only a mean size. For fermentation, they must be paired with viable cell response, substrate conversion, gas transfer, and product formation.

Figure 12.2. Relative importance of cavitation functions across the applications.

12.3 Beer Brewing

12.3.1 Process context and opportunities for intensification

Beer production converts grain starch into fermentable sugars and then uses yeast to convert those sugars into ethanol, carbon dioxide, flavor compounds, and biomass. The main brewhouse stages are malt milling, mashing, saccharification, solids separation, hopping and wort boiling, clarification, cooling, and transfer to fermentation. Conventional mashing relies on carefully controlled temperature rests to balance proteolysis, starch gelatinization, and alpha- and beta amylase activity. Wort boiling extracts and isomerizes hop alpha acids, removes volatile sulfur compounds, inactivates enzymes, precipitates proteins, and provides microbial control [15 to 17].

Hydrodynamic cavitation can combine several of these duties. Grain and malt particles are fractured, liquid films are renewed, soluble starch and enzymes are released, the wort is mixed intensely, hops are dispersed, and mechanical energy is converted into heat. This combination permits process sequences that are not direct one for one replacements for conventional vessels. The strongest evidence is from 230 L real scale experiments with a recirculating Venturi system and from a smaller rotor pulsation apparatus [9,10].

$${\eta }_{ext}=\frac{m_{s,\mathrm{wort}}}{m_{s,\max }}\times 100\%$$

(12.12)

where ${\eta }_{ext}$ is brewhouse extraction efficiency, $m_{s,\mathrm{wort}}$ is the mass of soluble extract recovered in wort, and $m_{s,\max }$ is the theoretical extract available from the grist. The same definition and moisture basis must be used for conventional and cavitation assisted trials.

$$Y_{P/S}=\frac{\mathrm{\Delta }P}{-\mathrm{\Delta }S}$$

(12.13)

where $Y_{P/S}$ is fermentation product yield, ΔP is the increase in ethanol or another product, and -ΔS is substrate consumption over the same interval.

$$r_P=\frac{\mathrm{\Delta }P}{\mathrm{\Delta }t}$$

(12.14)

where $r_P$ is volumetric or mass specific productivity and Δt is the selected fermentation interval.

12.3.2 Cavitation brewing equipment

The principal real scale brewing unit reported by Albanese and coworkers was a closed stainless steel hydraulic loop with a total volume near 230 L, a 7.5 kW centrifugal pump, an open impeller approximately 0.174 m in diameter, and operation near 2900 rpm. A circular Venturi generated cavitation, while a pressure release valve controlled downstream pressure. A secondary pump and plate heat exchanger enabled isothermal rests, cooling, and transfer. The Venturi was preferred to an orifice plate because circulating malt and hop solids could obstruct small holes [9].

The equipment was configured either for direct circulation of malt particles or with a stainless steel brew in the bag cage that retained solids while wort circulated through the cavitation loop. Fermentation was normally performed in separate 200 L cylinder conical vessels, although some trials used the main unit as a fermenter. The basic loop architecture is readily scaled by larger pumps and reactors or by parallel trains, but similarity in cavitation number alone is insufficient. Pass frequency, solids loading, heat loss, pressure recovery, and separation equipment must also be scaled [9,13,14].

Figure 12.3. Simplified 230 L hydrodynamic cavitation brewing loop with centrifugal pump, Venturi reactor, main vessel, pressure control, heat exchanger, circulation pump, and malt cage. Source: Albanese et al. [9].

Figure 12.4. Pilot and industrial grade cavitation assisted brewing installations. Source: Meneguzzo and Albanese workshop presentation [14].

12.3.3 Mashing, starch extraction, and solids handling

Cavitation assisted mashing modifies both the raw material and the liquid side transport resistance. Direct circulation of malt can eliminate a separate dry milling step because repeated collapse and impeller action progressively reduce the particle structure. Microscopy and photographs from the real scale study show substantially more disintegrated spent malt after cavitation than after conventional brewing. The larger accessible surface and thinner boundary layer increase release of starch, soluble proteins, minerals, and endogenous enzymes [9].

In the reported real scale experiments, peak starch extraction was accelerated and, in selected comparisons, increased by as much as 30% while using approximately 12% less energy. The effective saccharification temperature could be reduced by as much as 35 °C relative to the conventional temperature program. These values describe a specific recipe, installation, and analytical method; they should be treated as proof of process opportunity rather than universal design values [9].

The rotor pulsation study used a 1.12 L apparatus with rotor speed up to 4000 rpm, narrow rotor stator clearances, and a cooling jacket. At selected conditions near 2000 rpm, complete saccharification was reported after approximately 10-15 min at 70-80 °C. The same study reported that short treatment of brewing yeast in nutrient media could reduce fermentation time by about 1.5 d while preserving acceptable organoleptic quality. The results show the sensitivity of yeast response to mechanical intensity and the protective role of wort or whey, but they require broader replication and scale up validation [10].

Solids separation remains a decisive design issue. Directly cavitated malt produces fine particles that may overload traditional lautering. A retained malt cage, decanter centrifuge, rotary screen, or hydrocyclone may be required. The value of intensified extraction must therefore be assessed together with filtration rate, clarity, yield loss in the solids phase, and cleaning demand.

Figure 12.5. Conceptual comparison of coarse spent malt after conventional mashing and the more fragmented structure expected after cavitation assisted circulation.

12.3.4 Hopping, volatile removal, and wort boiling

Hop processing involves extraction of alpha acids and aromatic compounds, isomerization of alpha acids to soluble iso alpha acids, and control of dimethyl sulfide and other volatiles. Conventional boiling provides the required mixing and gas stripping but also consumes substantial thermal energy and can degrade hop compounds. Cavitation renews the hop liquid interface and produces intense local turbulence, so extraction and isomerization can proceed rapidly during bulk heating [9,17].

The real scale study reported useful hop alpha acid extraction before full boiling and concluded that the wort could be transferred to fermentation after heating to approximately 100 °C without the conventional long boil. Reported hop utilization was higher than in the conventional comparison, and later analysis found increased retention of xanthohumol and other prenylflavonoids under selected time temperature histories [9,12]. The process still requires validated removal of dimethyl sulfide and other recipe specific volatiles, because cavitation is not equivalent to open vessel evaporation.

Hydrodynamic cavitation was also reported to reduce measurable gluten in barley malt beers under selected operating regimes [11]. This result does not establish suitability for people with celiac disease. In the United States, a food bearing a gluten free claim must contain less than 20 ppm unavoidable gluten, and FDA has a separate compliance framework for fermented or hydrolyzed foods, including FDA regulated beer. Ingredient control, analytical evidence before fermentation, process records, cross contact prevention, and the applicable labeling jurisdiction must therefore be addressed independently [62].

Figure 12.6. Comparison of conventional and hydrodynamic cavitation assisted beer production routes

12.3.5 Fermentation, gas transfer, and yeast management

Cavitation can assist fermentation indirectly through rapid wort aeration, carbon dioxide removal, nutrient dispersion, and reduced mass transfer resistance. Manufacturer literature describes rotor cavitators for dispersing oxygen before yeast pitching and for producing fine carbon dioxide or nitrogen bubbles before filling [32]. Low power cavitation studies cited in the brewing literature reported faster sugar and free amino nitrogen utilization, but response peaks at intermediate severity. Excess treatment can rupture cells, inactivate enzymes, oxidize wort, or alter aroma precursors [9,10].

The preferred engineering strategy is therefore to separate objectives. Strong treatment is applied before inoculation for extraction, homogenization, heating, and microbial control. Yeast contact treatment, when used, is short and conducted in a protective nutrient medium under controlled temperature. Post fermentation cavitation is limited to gas dispersion, texture adjustment, or specially validated product treatment. Viable count, budding rate, membrane integrity, dissolved oxygen, fermentation rate, attenuation, ester profile, higher alcohols, and sensory quality should be measured together.

12.3.6 Energy, quality, sanitation, and scale up

The 230 L cavitation assisted process consumed approximately 24 kWh per hectoliter from equipment start up through wort transfer in one reported trial. The study compared this with a literature benchmark near 32 kWh/hL for conventional medium to large breweries and approximately 44 kWh/hL measured in a conventional 50 L brewer. The cavitation system was not fully insulated, and separate energy for dry milling was avoided. These comparisons suggest a strong opportunity for energy reduction, but they combine different scales and system boundaries and should be verified by plant specific metering [9].

Finished beers from the study showed acceptable physicochemical and sensory characteristics, and one illustrated sample retained visible foam stability after 124 d. Industrial implementation requires recipe by recipe validation of bitterness, color, haze, foam, volatile profile, ethanol, microbiological stability, and packaging behavior. Cleaning in place must account for grain fines, proteins, hop resins, seals, and dead legs. The sanitary design should allow complete drainability and inspection of the Venturi throat or rotor passages [9,13,14].

Figure 12.7. Specific energy reported for one cavitation assisted microbrewery trial, a conventional literature benchmark, and a 50 L conventional comparison. Source: [9].

Table 12.2. Representative beer brewing evidence and engineering interpretation.

Study or source	Scale and device	Reported result	Engineering interpretation
Albanese et al. [9]	230 L loop; 7.5 kW pump; circular Venturi	Faster extraction; selected peak extraction up to 30% higher; lower saccharification temperature; approximately 24 kWh/hL in one trial	Strong proof of integrated mashing, heating, and hopping; solids separation and recipe validation remain essential
Safonova et al. [10]	1.12 L rotor pulsation apparatus	Mashing reported in 10-15 min; fermentation shortened by about 1.5 d after yeast activation	Promising mechanistic and laboratory evidence; high mechanical intensity and scale up need validation
Gluten study [11]	Same HC brewing platform	Very low measured gluten under selected regimes	Specialty application; cannot substitute for full allergen and labeling validation
Prenylflavonoid study [12]	HC assisted hopping and brewing	Higher retention of xanthohumol and related compounds	Time temperature severity optimization can preserve or extract bioactives
Patent and workshop [13,14]	Pilot and industrial plant concepts	Integrated apparatus and process sequence	Useful equipment disclosure; performance claims should be verified independently

12.4 Juice and Milk

12.4.1 Fruit and vegetable juices, purees, and whole food suspensions

Juice and puree processing must balance microbial control, enzyme control, cloud stability, viscosity, color, flavor, and retention of labile compounds. Cavitation can disrupt fruit tissue, reduce pulp particle size, release intracellular compounds, and produce uniform volumetric heating. The same treatment can also accelerate oxidation, alter aroma, or increase sedimentation if severity is excessive. The process endpoint should therefore be set by the slowest required control or stability response rather than by cavitation intensity alone.

Hydrothermodynamic processing of whole blueberries provides an example of a strongly integrated process. A pilot recirculation unit used a 2.2 kW motor, centrifugal pump, pressure near 1.41 MPa, and a cavitating mixer that focused turbulent side streams in the center of the main flow. Crushing occurred rapidly, while continued circulation converted mechanical energy to heat until the product reached approximately 95 °C. The reported product contained 13% solids, had viscosity of 1.45-2.76 Pa s, exhibited low sedimentation, and reached a microbial load below 10 CFU/g [18].

The single unit blueberry process reduces transfers and air exposure, which can help protect anthocyanins despite the final pasteurization temperature. The reported apparatus accumulated heat with each circulation cycle and achieved a heating efficiency of approximately 0.69-0.81 over the tested batch. The result illustrates why hydrodynamic cavitation should not automatically be labeled nonthermal: in many practical food processes, the controlled conversion of work into heat is an intended function [18].

Figure 12.8. Hydrothermodynamic cavitation principle and TEK 1 pilot processor used for berry puree processing. Source: Martynenko and Chen conference paper [64].

Apple juice experiments at modest pressure reported a reduction in mean particle scale from approximately 8.9 µm to 1.1 µm, sedimentation near 7% compared with 10% for a thermal treatment and 39% for untreated juice, approximately 13% polyphenol oxidase inactivation, and a 0.9 log microbial reduction at the selected 15 psi condition [22]. These results demonstrate excellent physical stabilization but insufficient stand alone lethality for many commercial shelf stable applications.

Orange juice treatment at 4 bar and temperatures near 42 °C improved viscosity and physical stability, but only about 34.7% of pectin methylesterase was inactivated. Vitamin C and phenolics declined at long treatment times, making the optimum treatment much shorter than the maximum tested 90 min [21]. Tomato juice studies similarly reported an optimized short treatment near 10 psi and 10 min, with storage life improvement under refrigeration but limited log reduction [23].

A new study of surplus fruit and vegetable purees reported higher vitamin C and antioxidant retention after hydrodynamic cavitation than after conventional thermal treatment. Purple carrot puree retained 6.8 ± 0.6 mg vitamin C per 100 g compared with 0.6 ± 0.0 mg/100 g after thermal processing, and FRAP values reached 2580 ± 126 µmol Trolox equivalents per 100 g. The cavitated products were, however, more granular and fibrous, illustrating the need to optimize sensory texture as well as nutrient retention [24].

Physical stabilization, enzyme reduction, or a sublethal microbial response is not equivalent to a validated commercial pathogen control. Under the United States Juice HACCP regulation, the process must achieve at least a 5 log reduction of the pertinent microorganism, meaning the most resistant microorganism of public health significance likely to occur in the juice. The complete treatment must be validated for the specific juice and process by an appropriate process authority [60].

Figure 12.9. Reported particle settling after untreated, thermally processed, and hydrodynamic cavitation treated apple juice. Source. [22].

Figure 12.10. Selected quality retention indicators reported for cavitation treated juice systems. Source: [21 - 24].

The sedimentation velocity $V_s$ can be determined using equation 12.15.

$$v_s=\frac{({\rho }_p-{\rho }_f)g{d}^2}{18\mu }$$

(12.15)

where $v_s$ is the Stokes settling or creaming velocity, ${\rho }_p$ and ${\rho }_f$ are dispersed particle and continuous phase densities, d is particle or droplet diameter, and μ is continuous phase viscosity. Reducing d strongly suppresses separation because velocity scales with d².

$$\tau =K{\dot{\gamma }}^n$$

(12.16)

where τ is shear stress, K is the consistency coefficient, γ̇ is shear rate, and n is the flow behavior index. Many juice, dairy, and sauce systems are shear thinning with $n<1$.

$$\tau ={\tau }_0+K{\dot{\gamma }}^n$$

(12.17)

where ${\tau }_0$ is yield stress in the Herschel Bulkley model. Yield stress can support suspended pulp or droplets against gravitational separation but may impair pumping and heat transfer.

Table 12.3. Selected hydrodynamic cavitation studies on juice and puree processing.

Product and source	Device and condition	Main reported responses	Limitation or design implication
Whole blueberry [18]	5.5 L batch loop; central turbulent mixer; heated to 95 °C	13% solids; 1.45-2.76 Pa s; <10 CFU/g; stable suspension	Thermal cavitation process, not nonthermal; batch energy and oxidation must be balanced
Orange juice [21]	4 bar; up to 90 min; about 42 °C	Physical modification; only 34.7% PME inactivation; quality loss at long time	Short optimum; enzyme inactivation may require a hurdle or thermal step
Apple juice [22]	Low pressure HC; selected 15 psi condition	Particle size about 8.9 to 1.1 µm; 7% settling; 0.9 log reduction	Excellent cloud stabilization but limited stand alone lethality
Tomato juice [23]	Optimized short low pressure treatment	Improved refrigerated stability and quality retention	Product and refrigeration dependent
Mixed fruit and vegetable purees [24]	Nonthermal HC compared with thermal treatment	Higher vitamin C, polyphenols, and antioxidant activity	Grumosity and fibrosity reduced sensory acceptance

12.4.2 Milk, dairy beverages, powders, and fermented dairy products

Milk is a sensitive oil in water emulsion containing fat globules, casein micelles, whey proteins, lactose, salts, enzymes, and microorganisms. Conventional homogenization uses high pressure to reduce fat globule size, while pasteurization provides microbial control. Hydrodynamic cavitation can combine partial homogenization and heating, but the relative contributions of mechanical collapse and temperature must be separated experimentally [25 to 27].

In a fresh milk loop study, hydrodynamic cavitation at 6 bar in a carbon dioxide atmosphere for 30 min produced up to 88% microbial inactivation and rapid homogenization. The authors attributed part of the effect to breakup of microbial aggregates and improved carbon dioxide transfer [25]. Because 88% reduction is less than 1 log, this result is process intensification evidence rather than complete pasteurization validation.

A later raw milk study evaluated outlet temperatures of 40, 50, 60, and 72 °C. Mean fat globule size decreased from approximately 3.29 to 1.40 µm as treatment severity increased, while whey protein denaturation and acid gel behavior changed little. Total bacterial count fell by more than 1 log, but comparison with matched heat treatments indicated that most lethality was attributable to temperature [26]. This finding is important because it shows that useful simultaneous heating and homogenization can occur without claiming a purely nonthermal mechanism.

Orifice plate experiments with inoculated milk compared single- and multi hole plates at 3, 5, and 7 bar for 5-40 min. A five hole, 2 mm plate produced the highest reported reductions, approximately 3.5 log for Escherichia coli and 2.83 log for Staphylococcus aureus, within cavitation numbers of about 0.21-0.66 [27]. The different response of Gram negative and Gram positive organisms reinforces the need for target specific validation.

For Grade A milk and milk products in the United States, hydrodynamic cavitation must be integrated into a process that satisfies the current Grade A Pasteurized Milk Ordinance and the acceptance requirements of the responsible regulatory authority. A research log reduction or an outlet temperature by itself does not establish legal pasteurization. Flow diversion, minimum holding, temperature recording, equipment acceptance, sanitary construction, and post process protection remain part of the validated system [61].

Figure 12.11. Fresh milk cavitation pilot unit and recirculating process schematic with gas injection. Source: Crudo et al. [25].

Dairy protein processing exploits a different response: controlled disaggregation and unfolding. A 2026 study treated milk protein concentrate at 6 MPa for up to 30 min. Mean particle size decreased from 4.82 to 1.35 µm, and protein solubility increased from 88.2% to 98.8%. Emulsifying and foaming properties improved, while SDS PAGE showed no new low molecular weight bands, indicating conformational modification rather than extensive peptide bond cleavage [28]. The best functional response occurred at intermediate combinations of pressure and time; prolonged or excessive treatment reduced some foaming metrics.

For high solids MPC80, rotor cavitation reduced viscosity by approximately 20% at 25 Hz and 56% at 50 Hz, enabling higher solids before spray drying while maintaining average powder solubility near 97.5% after reconstitution [29]. A semi industrial rehydration study at 20% dry matter and 50 °C reported D90 of 0.45 µm and D[4,3] of 0.19 µm after cavitation, compared with 21.17 and 5.62 µm, respectively, after conventional high shear mixing [30]. These data show that wetting, immersion, dissolution, and deagglomeration can occur in one in line step.

Post fermentation rotor cavitation has also been used to smooth formulated Greek style yogurt. Increasing rotor speed from 0 to 60 Hz reduced the consistency coefficient and the number of visible grains, while retaining water holding capacity [31]. This is a product structuring operation rather than a microbial treatment and must be applied after considering starter culture viability and post process contamination control.

Figure 12.12. Particle size reduction and protein solubility increase reported for milk protein concentrate treated by hydrodynamic cavitation at 6 MPa. Source:. [28].

Figure 12.13. Commercial pilot rotor cavitator skids are used for dairy product development. Source: SPX Flow Technology [33].

Table 12.4. Representative milk and dairy applications.

Application	Condition or equipment	Reported response	Evidence interpretation
Fresh milk [25]	Loop HC, 6 bar, CO2, 30 min	Up to 88% microbial inactivation; rapid homogenization	Mild disinfection and gas transfer evidence; not full pasteurization
Raw milk [26]	Rotor HC with outlet 40-72 °C	Fat globules 3.29-1.40 µm; >1 log count reduction mainly thermal	Combined heating and homogenization with limited whey protein damage
Inoculated milk [27]	Multi hole orifices; 3-7 bar; 5-40 min	Up to 3.5 log E. coli and 2.83 log S. aureus reduction	Geometry and organism strongly affect response
Milk protein concentrate [28]	6 MPa; 0-30 min	4.82 to 1.35 µm; solubility 88.2% to 98.8%	Controlled disaggregation and unfolding; overprocessing possible
High solids MPC80 [29]	Rotor at 25 and 50 Hz	Viscosity reduced 20% and 56%; powder solubility about 97.5%	Potential evaporator and spray dryer capacity increase
MPC80 rehydration [30]	20% DM, 50 °C, semi industrial in line HC	D90 0.45 µm versus 21.17 µm conventional	Strong powder hydration and deagglomeration evidence
Greek style yogurt [31]	Post fermentation rotor treatment, 0-60 Hz	Lower consistency coefficient and fewer grains	Texture finishing operation; culture viability and contamination must be controlled

12.5 Egg Processing

12.5.1 Product sensitivity and process objectives

Liquid egg is a heat sensitive, protein rich fluid whose functionality depends on the integrity and dispersion of yolk lipoproteins, albumen proteins, and the natural emulsifying system. Pasteurization must control the relevant microorganisms without excessive coagulation, gelation, loss of foaming, or loss of emulsifying performance. Conventional plate heat exchangers are susceptible to protein fouling, which lowers heat transfer coefficient, increases pressure drop, and shortens production runs.

A rotor cavitator offers two potential advantages. First, microscopic mixing produces a more uniform whole egg dispersion before the holding tube, reducing local compositional differences. Second, conversion of shaft work to bulk heat occurs within the liquid rather than across a high temperature metal surface, reducing the hot wall driving force for fouling. These are plausible and useful engineering functions, but the supplied quantitative operating data come from a manufacturer application sheet and should be treated as manufacturer reported until independently validated [34].

Figure 12.14. Rotor cavitator package and cutaway of the cavitation chamber used in egg processing applications. Source: SPX Flow Technology [34].

12.5.2 Representative hybrid homogenization and pasteurization sequence

The supplied application sheet describes a whole liquid egg stored near 3 °C, preheated in a plate heat exchanger to approximately 56-58 °C, and then passed through the rotor cavitator at about 4 bar. The cavitator raises the product temperature by roughly 10 °C to approximately 66-68 °C while homogenizing the stream. A representative holding time of 3.5 min is followed by cooling to about 3 °C and hygienic packing [34].

The manufacturer reports that the absence of a conventional heat transfer surface in the cavitator extends run time to approximately 8-12 h between cleaning cycles, about 4 h longer than a conventional process, while protecting egg functionality. The same source states that yolk and white can also be treated with egg white requiring a product specific temperature adjustment. These values define a useful pilot starting point, not a regulatory process schedule. A commercial process must validate minimum residence time, worst case temperature, target organism lethality, post process contamination control, and functional performance for each formulation [34].

Figure 12.15. Representative hybrid process for liquid whole egg with plate preheating, cavitation assisted homogenization and heating, holding, cooling, and packing. Source: [34].

The time equivalent to the lethal effect F can be determined from Equation 12.18.

$$F={\int }_0^t{10}^{[T(t)-T_{ref}]/z}dt$$

(12.18)

where F is equivalent lethality time at reference temperature $T_{ref}$, T(t) is the measured product temperature history, and z is the temperature change required for a tenfold change in decimal reduction time. The correct target organism and kinetic constants must be established for the specific egg product.

12.5.3 Fouling, function retention, and hygienic design

Fouling mitigation should be verified by direct plant measurements rather than inferred only from appearance. The relevant indicators are heat transfer coefficient, pressure drop, wall temperature, run length, deposited mass, cleaning chemical demand, rinse conductivity, and microbiological verification after cleaning. Rotor power and bulk temperature rise should also be trended because viscosity and solids content affect disc friction.

Functional quality should include whole egg viscosity, yolk emulsion stability, albumen foaming capacity and stability, gel strength, color, and sensory behavior in the intended end product. Excess cavitation can denature or aggregate proteins even when no visible coagulation occurs. The preferred operating window is therefore the lowest severity that provides uniformity and validated lethality after the holding step.

Sanitary design requires fully drainable product contact surfaces, cleanable rotor holes, appropriate elastomers, sealed bearings outside the product zone, validated clean in place velocity, and inspection for protein accumulation behind shields or near the shaft. The equipment should be integrated with divert logic, so product is not released unless both temperature and minimum holding time are met.

Figure 12.16. Illustrative reconstruction of the manufacturer reported difference between a conventional heating surface and a cavitator without a product contact heat transfer surface. Source. [34].

Table 12.5. Egg processing design and validation checklist. All quantitative conditions are manufacturer reported [34].

Item	Representative manufacturer condition	Independent validation required
Feed and preheat	Whole egg near 3 °C; preheat to 56-58 °C	Composition, viscosity, starting microbiology, preheater fouling
Cavitator	Approximately 4 bar; temperature rise to 66-68 °C	Rotor speed, flow, energy, residence time distribution, minimum outlet temperature
Holding	Typically, 3.5 min	Minimum residence time, target organism kinetics, and verified holding time basis
Cooling and packing	Cool to about 3 °C	Cooling rate, hygienic zone, package integrity, post process contamination
Run length	Manufacturer reports 8-12 h between CIP	Heat transfer trend, deposits, ATP or microbiological verification, cleaning repeatability
Product function	Manufacturer reports protected functionality	Foaming, emulsification, gelation, viscosity, color, sensory performance

12.6 Ice Cream

12.6.1 Structure of ice cream mix and cavitation functions

Ice cream is a multiphase food containing ice crystals and air cells dispersed within a concentrated serum phase and a partially destabilized fat network. Before freezing, the mix must provide complete hydration of milk proteins, emulsifiers, stabilizers, sugars, and salts; controlled fat globule size; appropriate viscosity; and a protein emulsifier interface that will partially destabilize during ageing and freezing. Insufficient hydration produces clumps and weak body, whereas excessive homogenization can inhibit the fat destabilization needed for dryness and shape retention.

Hydrodynamic cavitation can be used at several points: powder hydration, whey protein microparticulation, pre emulsification of fat, scale free heating, and final dispersion. The equipment literature proposes a hybrid sequence in which the cavitator is used before preheating for hydration and again near pasteurization temperature for dispersion. Because product structure depends on both breakup and subsequent controlled aggregation, the optimum cavitation condition is not necessarily the condition that produces the smallest measured particle [35,36].

Figure 12.17. Representative integration of hydrodynamic cavitation into ice cream mix preparation. Source: [36].

12.6.2 Process concept and pilot research

The SPX Flow Technology application sheet describes vacuum powder mixing and pre emulsification, cavitation assisted hydration and functionalization, preheating at approximately 65-75 °C, optional valve homogenization below about 150 bar, cavitation assisted pasteurization and dispersion at approximately 75-85 °C, cooling to 5 °C, ageing for about 4 h, and continuous freezing and hardening. The manufacturer reports comparable pre agglomeration with approximately 1 µm particles after conventional homogenization and 2-3 µm after cavitation, together with potential reduction in homogenizing pressure and longer run time between cleaning cycles [36].

An independent pilot study Sim, et al. evaluated rotor speeds of 2400-3600 rpm and flow rates of 100-200 L/h. Cavitated mixes had a larger mean particle size than the two stage homogenized control, 3.52 ± 0.28 µm compared with 0.34 ± 0.02 µm. At 3600 rpm and 100 L/h, apparent viscosity in the 30-50 s⁻¹ range was about 2.2 times that of the control, and the viscoelastic behavior changed. Melting and meltdown behavior were also altered, indicating that hydrodynamic cavitation generated a different structural state rather than simply reproducing valve homogenization [35].

These results are technically important. A larger particle scale can reflect protein fat aggregates and structured clusters rather than poor processing. The appropriate endpoint is therefore the complete frozen dessert performance: overrun, extrusion pressure, air cell distribution, fat destabilization, ice crystal size, first drip time, meltdown rate, hardness, iciness, creaminess, and storage stability.

Figure 12.18. Microscopic appearance of ice cream premix after conventional homogenization and controlled cavitation. Source: SPX Flow Technology [36].

Figure 12.19. Relative apparent viscosity increase reported for a selected cavitated ice cream mix compared with two stage homogenization. Source: Sim et al. [35].

The overrun can be determined from Equation 12.19:

$$\mathrm{Overrun}=\frac{V_{\mathrm{i}\mathrm{c}\mathrm{e}\mathrm{c}\mathrm{r}\mathrm{e}\mathrm{a}\mathrm{m}}-V_{\mathrm{mix}}}{V_{\mathrm{mix}}}\times 100\%$$

(12.19)

where overrun is the percentage volume increase caused by incorporated air, $V_{\mathrm{i}\mathrm{c}\mathrm{e}\mathrm{c}\mathrm{r}\mathrm{e}\mathrm{a}\mathrm{m}}$ is the volume of frozen aerated product, and $V_{\mathrm{mix}}$ is the volume of unfrozen mix of the same mass basis.

12.6.3 Formulation and process design implications

Cavitation severity interacts strongly with stabilizer type, protein concentration, fat source, emulsifier, total solids, inlet temperature, ageing time, and freezer conditions. A reduction in stabilizer is only beneficial if meltdown resistance, heat shock stability, and sensory smoothness remain acceptable. Similarly, whey protein microparticulation can produce a creamy low fat texture, but excessive heating or shear may aggregate protein and raise viscosity beyond the capacity of the downstream freezer.

Pilot design should therefore use a response surface or sequential design of experiments. Independent variables should include rotor speed, flow, passes, inlet temperature, solids, stabilizer dose, and homogenizer pressure. Responses should include energy per kilogram, temperature rise, D10/D50/D90, d32, rheology, protein solubility, fat destabilization, overrun, first drip, complete meltdown, and sensory texture. Product temperature should be controlled independently when separating mechanical cavitation effects from heating.

Table 12.6. Critical quality attributes for cavitation assisted ice cream processing.

Stage	Primary cavitation function	Measurements required
Powder incorporation	Wetting, dissolution, gum hydration, deagglomeration	Undissolved particles, viscosity development, hydration time, protein solubility
Pre emulsification	Fat breakup and rapid emulsifier adsorption	Droplet size distribution, free fat, emulsion stability
Pasteurization and heating	Bulk heating without a high temperature wall	Temperature uniformity, lethality, fouling, flavor and protein changes
Ageing	Controlled crystallization and interface rearrangement	Viscoelasticity, fat crystallization, partial coalescence potential
Freezing and aeration	Air incorporation and fat network formation	Overrun, air cell size, extrusion pressure, fat destabilization
Frozen storage	Resistance to heat shock and structural collapse	Ice crystal growth, hardness, iciness, meltdown, sensory acceptance

12.7 Mayonnaise and Salad Dressing

12.7.1 Emulsion structure and processing objectives

Mayonnaise and many salad dressings are concentrated oil in water emulsions stabilized by egg yolk components, milk or whey proteins, mustard, hydrocolloids, starch, and other surface active ingredients. Traditional mayonnaise may contain 50-80% vegetable oil, while reduced fat products replace part of the dispersed phase with structured aqueous material. Product viscosity and shelf stability depend on droplet volume fraction, droplet size distribution, interfacial coverage, continuous phase rheology, and the absence of entrained oxygen [37].

Cavitation can complete several duties in one in line step: hydrate powders, pre emulsify oil, reduce droplet size, distribute emulsifier over the newly generated interface, disperse flavor oils, and optionally introduce nitrogen for a whipped texture. The enclosed housing can limit uncontrolled air pickup, but the feed premix must be uniform and delivered at constant flow. Otherwise, transient oil rich slugs can overload the available emulsifier and cause irreversible coalescence.

Figure 12.20. Rotor cavitator drive, cutaway of the cavitation chamber, and finished emulsion examples. Source: SPX Flow Technology [37].

12.7.2 Process sequence and droplet size control

A representative process begins by hydrating starch, whey protein, stabilizers, and hydrocolloids in the aqueous phase. Oil, egg yolk, vinegar, salt, sugar, mustard, spices, and flavors are metered into a batch premixer or continuous pre emulsifier. The cavitator then provides final microscopic mixing and droplet breakup. A second pass or dedicated finishing stage may adjust viscosity, gloss, color, and optional gas content [37].

The manufacturer states that droplet sizes of approximately 3-5 µm can be obtained readily and that the distribution shifts to smaller sizes as rotor frequency increases from 40 to 60 Hz. The same source proposes whey protein microparticulation for creamy mouthfeel in reduced fat formulations and nitrogen dispersion for whipped mayonnaise. These are useful process development targets, but the actual droplet distribution depends on formulation, interfacial tension, emulsifier kinetics, temperature, flow, and pass count [37].

Figure 12.21. Continuous or batch process sequence for cavitation assisted mayonnaise and salad dressing manufacture. Source: [37].

Figure 12.22. Schematic reconstruction of the SPX Flow Technology reported shift in oil droplet distribution with increasing rotor frequency. Source: [37].

The Sauter mean diameter $d_{32}$ and maximum stable $d_{max}$ of the droplets can be determined from Equation 12.20 and 12.2:

$$d_{32}=\frac{\sum n_i{d}_i^3}{\sum n_i{d}_i^2}$$

(12.20)

where $d_{32}$ is the Sauter mean diameter, $n_i$ is the number of droplets in size class i, and $d_i$ is the representative class diameter. $d_{32}$ is proportional to dispersed phase volume divided by interfacial area and is therefore useful for emulsification energy comparisons.

$$d_{max}=C{\left(\frac{\gamma }{\rho }\right)}^{3/5}{\epsilon }^{-2/5}$$

(12.21)

where $d_{max}$ is the maximum stable droplet scale in the inertial breakup regime, C is a system dependent constant, ε is local turbulent energy dissipation rate per unit mass, γ is interfacial tension, and ρ is continuous phase density. The Hinze relation is a scaling guide rather than a complete model for concentrated mayonnaise.

12.7.3 Recent vortex cavitation emulsification studies

Vortex based cavitation devices provide a stationary alternative to rotor equipment. A Thaker, et al. study compared machined and 3D printed 316L vortex diodes at about 1 L/min, and 250 kPa pressure drop. After repeated passes, both devices produced similar droplet size distributions and Sauter diameters; the study reported d32 values near the micrometer scale and little penalty from the rougher additively manufactured surface [38]. The result supports rapid fabrication of complex sanitary prototypes, although food contact qualification and cleanability of printed surfaces remain necessary.

A continuous emulsification study Gode, et al. examined chamber geometry, vortex stabilizers, multiple inlets, geometric scale up from 1min and min, and scale out using parallel devices. Multi inlet designs improved cavitation activity and droplet breakup at low pressure drop. Scale up caused a slight increase in d32 and lower energy efficiency, whereas scale out preserved the final droplet size distribution more closely. These findings favor modular parallel trains when tight emulsion quality is more important than minimum equipment count [39].

The recent vortex literature also emphasizes that final distribution is governed by cumulative energy and number of passes. A recirculating laboratory result cannot be converted directly to single pass production without sufficient active zone exposure. For mayonnaise, where viscosity increases sharply as the emulsion tightens, the pump and device must be sized for the final rather than initial rheology.

Table 12.7. Design variables for cavitation assisted mayonnaise and salad dressing.

Variable	Effect on product	Control strategy
Oil volume fraction	Raises crowding, viscosity, and collision frequency	Accurate mass flow; prevent oil rich slugs
Emulsifier type and concentration	Controls interfacial coverage and coalescence resistance	Ensure hydration and availability before intense breakup
Rotor speed or pressure drop	Changes local dissipation, droplet breakup, and temperature rise	Closed loop control using power, flow, temperature, and DSD
Pass count or residence time	Narrows DSD until a limiting size; excessive exposure may heat or aggregate proteins	Define endpoint from DSD and viscosity, not time alone
Temperature	Changes viscosity, interfacial tension, protein state, and flavor volatility	Condition phases and cool as needed
Hydrocolloid hydration	Determines continuous phase viscosity and syneresis resistance	Hydrate before final emulsification; verify fish eye elimination
Particulates and spices	Can add flavor and homemade appearance but may obstruct close clearance devices	Confirm passage size and distribution without damage
Gas content	Affects density, oxidation, color, and whipped texture	Vacuum deaeration or controlled N2/CO2 addition

12.8 Food Proteins and Bioproduct Recovery

12.8.1 Protein extraction and functional modification

Cavitation can increase protein recovery by disrupting cell walls, reducing particle size, increasing solubility, and accelerating liquid penetration. It can also alter the structure of already extracted proteins, changing emulsifying, foaming, gelation, and hydration behavior. These two objectives require different severity. Extraction often benefits from strong disruption, whereas functionalization requires sufficient unfolding without irreversible aggregation or peptide degradation [28 to 31,41].

A soy processing study by Preece, et al. used a two stage high pressure homogenizer at 50-125 MPa to treat soy slurry and diluted okara. A single pass at 100 MPa increased total protein extraction from soy slurry to approximately 82%. Repeated passes did not continue to improve yield because viscosity, swelling, particle interactions, and reduced centrifuge separation efficiency offset the greater protein availability. Okara extraction reached a plateau after one pass [41]. The study demonstrates the need to optimize extraction and separation as a coupled system.

Milk protein data reviewed in Section 12.4 show a milder functionalization pathway. At 6 MPa, prolonged treatment reduced aggregate size and raised solubility without new low molecular weight bands on SDS PAGE [28]. Rotor cavitation at lower pressure but high pass frequency reduced viscosity in high solids MPC80 and accelerated powder rehydration [29,30]. The choice of device must therefore reflect whether the target is cell disruption, powder deagglomeration, or controlled molecular reorganization.

$$Y_p=\frac{S{x}_{p,s}}{S{x}_{p,s}+O{x}_{p,o}}\times 100\%$$

(12.22)

where $Y_p$ is protein extraction yield to the soluble soy base stream, S and O are the masses of soy base and okara streams, and $x_{p,s}$ and $x_{p,o}$ are their protein mass fractions [41].

12.8.2 Intracellular polymer recovery

Hydrodynamic cavitation has been evaluated for recovery of intracellular polyhydroxyalkanoates from mixed microbial culture. A Yilmaz, et al. study used a 3 L stainless steel loop with exchangeable orifices and short treatment. Under the selected optimum, approximately 71.7% recovery efficiency and 71.4% polymer purity were reported, compared with higher recovery and purity for conventional chloroform extraction [42].

The cavitation route provides rapid mechanical cell disruption and can reduce chemical and thermal requirements, but it does not eliminate downstream separation. Polymer molecular weight, thermal stability, residual biomass, solvent use, energy, and equipment wear must be included in the comparison. The study recommends investigation of vortex and rotor stator devices for scale up, reflecting the broader advantage of locating the active cavitation away from erosion sensitive surfaces [42].

12.8.3 Controlled manufacture of protein microbubbles

Not every cavitation application seeks to destroy bubbles. A Bhattacharjee, et al. study used a vortex based hydrodynamic cavitation platform to manufacture albumin microbubbles for therapeutic delivery. The device generated microbubbles near 7 µm under mild conditions and loaded them with curcumin. Ultrasound triggered delivery produced substantially greater release or uptake than the no sonicated condition in the reported system [43].

This application illustrates a broader principle: hydrodynamic cavitation can be designed as a controlled bubble manufacturing platform when gas introduction, protein adsorption, pressure history, and collection are tuned to stabilize rather than immediately collapse the bubbles. Food analogues include aerated dairy products, beverage nitrogenation, foams, and encapsulated flavors, although food grade formulations require independent development.

Table 12.8. Protein and bioproduct applications of hydrodynamic cavitation.

Application	Device or severity	Reported result	Primary scale up constraint
Soy protein extraction [41]	High pressure homogenizer; one pass at 100 MPa	Protein extraction up to approximately 82%	Centrifuge separation efficiency and viscosity after repeated passes
Milk protein concentrate [28]	6 MPa, up to 30 min	4.82 to 1.35 µm; solubility 88.2% to 98.8%	Avoid excessive aggregation and functional property reversal
MPC80 viscosity reduction [29]	Rotor at 25-50 Hz	Viscosity reduced 20-56%	Energy, temperature rise, and evaporation or dryer integration
MPC80 rehydration [30]	Semi industrial in line HC	D90 0.45 µm versus 21.17 µm conventional	Powder feed consistency and sanitary powder induction
PHA recovery [42]	3 L loop; orifice; short treatment	71.7% recovery and 71.4% purity	Cell disruption versus polymer preservation and downstream separation
Albumin microbubbles [43]	Vortex cavitation with gas and protein	Approximately 7 µm microbubbles and triggered delivery	Bubble stability, gas control, sterile or hygienic manufacture

12.8.4 Adjacent high shear micron and nano formulation methods

Impinging jet and Microfluidizer processors are hydrodynamic cavitation devices. They are, however, useful benchmarks because they combine controlled high pressure flow, intense micromixing, cavitation and short residence time to produce functional food dispersions. A study reported fish oil emulsions containing 12 to 14 wt.% oil with median droplet sizes of 119 to 163 nm and no particles larger than 1 µm. The same platform reduced a vitamin C liposome formulation from a median scale near 5 µm to approximately 200 nm at the best four pass condition [65].

The study also produced soy fiber dispersions in which 99% of particles were below 15 µm and curcumin particles in the approximate 300 to 500 nm range. These results show why a technology comparison should be based on final size distribution, oxidation, temperature history, pass count, energy per unit mass, cleanability, and stability in the final food matrix. A cavitation process may be preferred for scale, lower pressure, combined heating, or extraction, while an impinging jet higher pressure system may be preferred when a narrowly controlled nano formulation is the primary objective [65].

12.9 Dry Mill Corn Ethanol and Fermentation

12.9.1 Process rationale and pilot system

Dry mill corn ethanol production includes milling, slurry preparation, cooking or pretreatment, liquefaction, saccharification, simultaneous saccharification and fermentation, distillation, and recovery of distillers grains. Residual starch remains in distillers dried grains with solubles because some granules are inaccessible, incompletely gelatinized, trapped in cellular structure, or converted to poorly fermentable products during severe heating. Finer dry milling can improve accessibility but increases electrical demand and capital cost [44 to 50].

The Ramirez-Cadavid, et al. study evaluated controlled flow hydrodynamic cavitation at energy densities representative of commercial processing. A 379 L heated vessel and 74.6 kW centrifugal pump delivered corn slurry through a patented multi orifice device formed by two flow channels separated by a perforated diaphragm. The active restriction created a bubble rich zone, and pressure recovery collapsed the bubbles during exposure on the order of 0.5 s. The system was configured for pressure, differential pressure, flow, and temperature and could either recirculate or discharge to the next process stage [44,56 to 59].

Figure 12.23. Controlled flow cavitation device used in grain slurry pretreatment. Source: n [56,57].

Figure 12.24. Pilot and commercial controlled flow cavitation equipment used for corn slurry treatment. [58,].

Figure 12.25. Pilot process configurations used to compare untreated slurry, hydrodynamic cavitation, jet cooking, and combined treatment. Source: Wrenn [58].

12.9.2 Experimental conditions and analytical basis

The starch release experiment treated mash near 80 °C at specific energy inputs of 627, 940, 1254, and 1567 J/kg slurry. The ethanol yield experiments compared hydrodynamic cavitation treatments of 313, 940, and 1567 J/kg with an untreated control and jet cooking at approximately 106 °C. Corn slurry contained approximately 30.9% solids. Alpha amylase was evaluated at 40%, 70%, and 100% of the conventional total dose, corresponding to 0.016%, 0.028%, and 0.040% by dry corn mass [44,58,59].

After pretreatment, samples underwent liquefaction and simultaneous saccharification and fermentation. Ethanol, glucose, oligosaccharides, lactic acid, glycerol, acetic acid, and carbon dioxide were quantified. Unfermented total glucose converted DP4+, maltotriose, maltose, and glucose to a common glucose equivalent basis. This prevents an apparent improvement caused only by shifting carbohydrate from one oligomer fraction to another [44,58,59].

$$\mathrm{UFTG}=1.11DP{4}^{+}+1.07DP3+1.05DP2+G$$

(12.23)

where UFTG is unfermented total glucose equivalent, DP4+ is the concentration of oligomers containing four or more glucose units, DP3 is maltotriose, DP2 is maltose, and G is glucose. Coefficients correct for water addition during hydrolysis to monomers [44,59].

Table 12.9. Pilot dry mill corn cavitation conditions.

Treatment	Specific energy, J/kg slurry	Representative pump flow, L/min	Temperature rise across treatment	Purpose
Cav2A	313	26.1 ± 0.7	Approximately 3.2 °C	Low severity ethanol yield treatment
Cav2B	940	40.5 ± 2.6	Approximately 6.2 °C	Intermediate treatment and cavitation plus jet comparison
Cav2C	1567	51.5 ± 0.4	Approximately 8.4 °C	High severity ethanol yield treatment
Starch release series	627, 940, 1254, 1567	Condition dependent	Measured at each setting	Particle size and soluble starch response
Jet cooking	Not expressed as HC energy density	Process dependent	Slurry held near 106 °C under pressure	Conventional thermal comparator

12.9.3 Particle size, starch accessibility, fermentation, and enzyme dose

Hydrodynamic cavitation preferentially reduced the coarse portion of the corn particle distribution and increased soluble starch and saccharides. The highest starch release treatment increased soluble starch by approximately 11% relative to the untreated mash. Because collapse acts most strongly at weak points, pores, and interfaces, large particles are fragmented disproportionately while fine particles approach a limiting size [44,58,59].

Pooled ethanol results increased with cavitation energy density. Ethanol concentrations were approximately 35.10% for the control, 35.04% for 313 J/kg, 35.73% for 940 J/kg, 36.01% for 1567 J/kg, and 34.86% for jet cooking, expressed on the study's dry corn basis. The intermediate and high cavitation treatments produced statistically higher pooled ethanol than the control and jet cooked samples. Unfermented total glucose declined modestly, and carbon dioxide production tracked ethanol closely [44,59].

Alpha amylase dose from 40% to 100% of the conventional dose did not produce a significant pooled difference in ethanol yield under the tested conditions. This indicates that improved starch accessibility permitted reduction from 0.040% to 0.016% alpha amylase by dry corn mass without a significant yield penalty. Enzyme economics should nevertheless be rechecked with the plant's corn quality, solids, pH, enzyme formulation, and recycle streams [44,58,59].

A separate comparison using 940 J/kg found approximately 35.8% ethanol for cavitation alone, 35.3% for cavitation followed by jet cooking, and 35.0% for the untreated control. The lower result for the combined treatment suggests that severe heating after cavitation can offset accessibility benefits through formation of unfermentable products or other thermal effects. This is consistent with the earlier commercial scale study, where controlled flow cavitation alone outperformed cavitation followed by jet cooking [44,45,58,59].

Figure 12.26. Effects of cavitation energy density on corn slurry particle size distribution and glucose related responses. Source. [59].

Figure 12.27. Pooled ethanol and unfermented total glucose responses in the pilot dry mill study. Source: Author generated from Ramirez Cadavid et al. [59].

Table 12.10. Pooled fermentation results from the pilot pretreatment comparison.

Treatment	Ethanol	UFTG	Lactic acid	Glycerol	Acetic acid	CO2
Control	35.10 ± 0.70	2.40 ± 0.06	0.12 ± 0.01	2.54 ± 0.06	0.13 ± 0.01	36.00 ± 0.50
Cav2A, 313 J/kg	35.04 ± 0.38	2.32 ± 0.13	0.12 ± 0.01	2.60 ± 0.07	0.14 ± 0.00	35.93 ± 0.47
Cav2B, 940 J/kg	35.73 ± 0.16	2.33 ± 0.02	0.10 ± 0.01	2.57 ± 0.03	0.14 ± 0.00	36.87 ± 0.11
Cav2C, 1567 J/kg	36.01 ± 0.25	2.30 ± 0.14	0.10 ± 0.01	2.42 ± 0.03	0.14 ± 0.00	37.17 ± 0.09
Jet cooking	34.86 ± 0.44	2.17 ± 0.19	0.11 ± 0.02	2.61 ± 0.09	0.14 ± 0.01	35.64 ± 0.74

.

12.9.4 Energy return and commercial interpretation

The incremental energy return $R_E$ can be determined from Equation 12.24:

$$R_E=\frac{m_{\mathrm{E}\mathrm{t}\mathrm{O}\mathrm{H},\mathrm{a}\mathrm{d}\mathrm{d}}LH{V}_{\mathrm{EtOH}}}{{\int }_0^t{P}_{el}(t)dt}$$

(12.24)

where $R_E$ is net incremental energy return, $m_{\mathrm{E}\mathrm{t}\mathrm{O}\mathrm{H},\mathrm{a}\mathrm{d}\mathrm{d}}$ is additional ethanol produced relative to the control, $LH{V}_{\mathrm{EtOH}}$ has ethanol lower heating value, and the denominator is additional electrical energy used by cavitation.

The pilot study reported approximately 47 kJ of additional ethanol energy for each kilojoule used by hydrodynamic cavitation at the selected optimum. The earlier commercial scale study at a 379 million L/y plant reported an energy return near 16 and an average ethanol increase of about 2.2% [44,45,59]. The difference reflects system boundary, operating point, baseline, and statistical uncertainty; both results indicate that a small specific mechanical input can unlock a much larger chemical energy value when it improves conversion of existing carbohydrate.

Commercial evaluation should include the installed pressure drop, pump efficiency, maintenance, erosion inspection, enzyme savings, increased ethanol, DDGS composition, downstream evaporation, and any eliminated jet cooking steam. The cavitation device should be positioned where mash temperature, viscosity, and particle size permit reliable flow. Differential pressure, flow, and temperature should be interlocked to prevent operation outside the validated envelope.

12.9.5 Commercial scale evidence and patent integration

The controlled flow cavitation patents disclose several integration points in a grain to alcohol plant. The device may be installed in a slurry tank recirculation loop, between slurry preparation and cooking, after cooking and before liquefaction, or in a liquefaction loop. Localized flow restrictions generate the low pressure zone, while downstream pressure recovery and an optional resistance control bubble collapse. These patents establish apparatus and process options, but patent claims are not independent proof of yield, energy, or reliability [56,57].

The NCERC pilot report provides a controlled experimental comparison. At both 58 and 77 °C slurry preparation temperatures, treatment at 200 and 300 psig increased ethanol yield by approximately 2 to 3% relative to untreated slurry. At 77 °C, yield rose from 0.363 to 0.376 g ethanol per g dry corn at 300 psig. At 58 °C, yield rose from 0.358 to 0.366 g/g. No statistically significant increase was found for jet cooking or 100 psig cavitation under the tested conditions [58].

The Ohio State thesis extended the work to a commercial dry mill plant with annual production near 100 million gal. Cavitation alone increased ethanol production by 2.2% relative to uncavitated samples. Cellulase without cavitation increased production by about 2.5%, while the combination of cavitation and cellulase increased production by about 4.3%. The electrical energy used for cavitation was reported as approximately one sixteenth of the energy contained in the additional ethanol, and the value of the added ethanol exceeded the electricity cost by more than thirty times. These are study specific results and require confirmation with current feedstock, enzyme, energy, and coproduct economics [59].

Figure 12.28. Patent process context and commercial controlled flow cavitation equipment. Sources: [57,58].

Figure 12.29. NCERC pilot study ethanol yields at 300 psig compared with untreated controls at two slurry preparation temperatures. Source: [58].

Figure 12.30. Commercial scale reported incremental ethanol production from cavitation, cellulase without cavitation, and combined cavitation plus cellulase. Source: [59].

Table 12.11. Supplied corn ethanol evidence and engineering interpretation.

Source	Scale and treatment	Reported outcome	Engineering interpretation
Wrenn [58]	NCERC pilot slurry; 100, 200, and 300 psig	Approximately 2 to 3% yield increase at 200 and 300 psig; no significant increase at 100 psig or with jet cooking	Defines a pressure threshold for the tested corn, solids, temperature, enzyme, and fermentation protocol
Ramirez Cadavid [59]	Pilot dry mill treatment over a wider energy range	11.6% increase in total glucose released and 2.7% increase in ethanol at the maximum tested treatment	Shows that particle opening and liquefaction response must be evaluated together
Ramirez Cadavid [59]	Commercial plant near 100 million gal/y	2.2% cavitation only; 2.5% cellulase only; 4.3% combined	Supports plant scale opportunity, but economics depend on feedstock, enzymes, coproduct, and energy boundaries
Kozyuk patents [56,57]	Multiple possible insertion points and recirculation arrangements	Apparatus and integration claims	Useful configuration disclosure; not independent performance evidence

12.10 Cross Cutting Design, Scale Up, and Economics

12.10.1 Product first process development

A cavitation process should begin with critical quality attributes rather than with a preferred device. The product specification may be a microbial log reduction, D90, d32, viscosity at a defined shear rate, extraction yield, enzyme residual activity, overrun, bitterness, color, or shelf life endpoint. The device and operating condition are selected only after the required response and acceptable quality losses are defined [6,7].

A practical development sequence is characterize the untreated feed; screen device geometry and severity at controlled temperature; identify response plateaus and quality loss thresholds; optimize pass count or residence time; integrate heating, cooling, gas, separation, and holding; perform challenge and shelf life studies; and then scale by preserving the mechanisms that control the endpoint. At each stage, the energy boundary must include auxiliary pumping and cooling.

Figure 12.31. Illustrative first order microbial inactivation curves for mild cavitation, cavitation plus moderate heat, and an optimized hurdle process. Source: [19,20,25 to 27].

Figure 12.32. Product development and scale up sequence for food cavitation processes.

12.10.2 Scale up

Geometric scale up of a Venturi, orifice, vortex, or rotor changes the distribution of turbulence, cavity residence, wall proximity, and heat loss. Matching cavitation number, pressure drop, or tip speed individually cannot guarantee the same product response. At minimum, scale up should compare flow per active volume, pass frequency, specific energy, pressure recovery profile, maximum and mean temperature, residence time distribution, solids passage, and the local stress scale that controls breakup [5,7,8].

Scale out is attractive when a small device has a validated product window. Parallel identical modules preserve geometry and can provide redundancy, cleanability, and turndown. The 2026 vortex emulsification study found that parallel devices preserved droplet size distribution more closely than geometric scale up, although energy effectiveness still depended on manifold design and operating point [39]. Parallel trains require balanced flow, identical backpressure, and hygienic manifolds without stagnant branches.

Dynamic rotor equipment introduces additional similarity groups: tip speed, rotor diameter, hole geometry, frequency, clearance, torque, and mechanical power per volume. Large rotors may be limited by stress, seal speed, vibration, and bearing load. Multiple smaller rotors or stages may provide a more practical scale up path than a single geometrically enlarged machine.

12.10.3 Sanitary engineering, erosion, and maintenance

Food contact materials should resist product chemistry, cleaning chemicals, and cyclic mechanical load. Cavitation zones must be placed away from vulnerable surfaces when possible, and wear parts should be inspectable and replaceable. A gradual increase in pressure drop, metal particles, vibration, or loss of product response can indicate obstruction or erosion. Baseline thickness and surface finish measurements are useful for high severity service.

Clean in place validation should include turbulent cleaning flow through the same restrictions and rotor passages used in production. Gums, starch, egg protein, hop resins, fruit fibers, and dairy deposits require different alkaline, acidic, enzymatic, or oxidative cleaning sequences. The process should be fully drainable, and gas pockets should not prevent wetting of the active zone. Sanitary performance must be confirmed by rinse chemistry, visual inspection, ATP screening where appropriate, and microbiological verification.

12.10.4 Economic assessment

Economic benefit can arise from shorter batch time, higher extraction or ethanol yield, lower enzyme or stabilizer dose, reduced homogenizing pressure, eliminated milling or boiling, higher evaporator solids, longer production runs between cleaning cycles, lower wastewater generation, or new product functionality. These benefits must be separated from marketing claims and quantified with plant data.

A discounted cash flow assessment should include equipment, pump or motor, variable frequency drive, cooling, separators, installation, validation, cleaning, maintenance, wear parts, and downtime. The energy comparison should use matched system boundaries and production rates. A high process yield in the active device can be offset by inefficient recirculation or cooling, while modest direct energy saving may still be valuable if the process increases sellable yield or plant capacity.

Table 12.12. Scale up and validation checklist for industrial food cavitation.

Workstream	Required evidence before commercial release
Product specification	Defined microbial, enzymatic, physical, chemical, sensory, and shelf life acceptance limits
Feed characterization	Composition, pH, density, rheology, solids and particle size, interfacial tension, dissolved gas, temperature range
Hydraulic characterization	Device drawing, pressure reference locations, flow curve, pressure drop, cavitation regime, pass frequency, and RTD
Thermal and energy balance	Electrical, shaft, and hydraulic power; temperature history; cooling duty; heat loss; specific energy
Process robustness	Feed variability, start up, shutdown, turndown, blockage response, gas sensitivity, reproducibility
Microbiological validation	Target organism challenge, worst case residence and temperature, and microbiological stability
Product quality	DSD or PSD, rheology, separation stability, nutrient and flavor retention, intended end use performance
Sanitation and durability	CIP/SIP validation, drainability, fouling trend, erosion and wear inspection, spare parts strategy
Scale up strategy	Similarity criteria, pilot to commercial correlation, parallelization balance, manifold design
Economics	Capital, energy, maintenance, cleaning, consumables, yield, capacity, labor, wastewater, and sensitivity analysis

12.11 Conclusions

When these principles are followed, hydrodynamic cavitation can replace, combine, or reduce several conventional operations. Its strongest commercial case is not cavitation intensity by itself, but a validated improvement in sellable yield, product functionality, safety, energy use, or production capacity at acceptable maintenance and quality risk. Future work should emphasize continuous sanitary systems, standardized reporting, independent replication, long duration erosion studies, and predictive scale out methods for viscous and multiphase foods.

Hydrodynamic cavitation is a versatile platform for food and fermentation processing because it couples flow acceleration, cavity dynamics, turbulence, interfacial renewal, and energy dissipation. Beer and corn ethanol applications use extraction, particle opening, and increased starch accessibility. Juice and dairy applications use stabilization, homogenization, and combined thermal and mechanical treatment. Egg, ice cream, mayonnaise, and salad dressing applications use uniform heating, powder hydration, controlled protein modification, and emulsion structuring. Protein and bioproduct applications extend the same mechanisms to extraction, cell disruption, and controlled bubble formation.

The literature also establishes clear limits. Microbial reduction is often modest unless cavitation is combined with temperature, gas, pressure holding, or another validated hurdle. Enzyme inactivation can lag behind physical stabilization. Excess treatment can degrade vitamins, flavor, foaming behavior, fermentation performance, or separation efficiency. Research findings, patents, and manufacturer application sheets provide useful mechanisms and starting conditions, but they do not replace product specific regulatory validation, sanitary design review, or an independent plant trial [56 to 62].

The most reliable design philosophy is product first and measurement intensive. Device geometry, pressure, flow, pass frequency, residence time distribution, temperature, energy, rheology, gas content, and product response must be reported together. Scale up should preserve the mechanism that controls the endpoint and may favor parallel validated modules instead of one enlarged reactor. Commercial assessment must use matched system boundaries and include pumping, cooling, cleaning, wear, downstream separation, enzyme use, yield, product quality, and plant capacity.

Nomenclature

Unless otherwise stated, quantities are expressed in SI units. Product specific analytical units are retained where they are conventional in the cited literature.

Table 12.13. Symbols and abbreviations used in this chapter.

Symbol	Definition	SI unit or status
a	Specific interfacial area	m² m⁻³
C	Concentration or model constant, as defined locally	varies
C∞	Asymptotic extracted concentration	kg m⁻³ or equivalent
$c_p$	Specific heat capacity	J kg⁻¹ K⁻¹
d	Particle or droplet diameter	m
d32	Sauter mean diameter	m
D10, D50, D90	Particle or droplet diameters below which 10%, 50%, or 90% of volume lies	m
$D_h$	Hydraulic diameter	m
DP2, DP3, DP4+	Glucose oligomer fractions in HPLC analysis	concentration
$E_s$	Specific energy input, hydraulic or electrical as specified	J kg⁻¹
$E_a$	Apparent activation energy	J mol⁻¹
F	Equivalent process lethality at a reference temperature	time
$f_p$	Nominal pass or loop turnover frequency	s⁻¹
g	Gravitational acceleration	m s⁻²
G	Glucose concentration in the UFTG equation	mass concentration
$h_L$	Irreversible head loss	m of fluid
k	Apparent first order rate constant	s⁻¹
k0	Arrhenius pre exponential factor	s⁻¹
$k_{L}a$	Volumetric mass transfer coefficient	s⁻¹
K	Consistency coefficient in a rheological model	Pa sⁿ
LR	Microbial log reduction	dimensionless
m	Mass	kg
$m_{s,\max }$	Maximum theoretical soluble extract	kg
N, N0	Viable population after treatment and initially	CFU mL⁻¹ or CFU g⁻¹
n	Flow behavior index	dimensionless
$n_p$	Nominal cumulative number of passes	dimensionless
P	Product amount or power, as defined locally	varies
$P_{el}$	Electrical power	W
$P_h$	Hydraulic power	W
p	Pressure	Pa
$p_B$	Pressure inside a bubble	Pa
$p_h$	Perimeter of an orifice hole	m
$p_{mp}$	Internal perimeter of the downstream main pipe	m
$p_r$	Recovery or downstream pressure	Pa
$p_v$	Liquid vapor pressure	Pa
Q	Volumetric flow rate	m³ s⁻¹
R	Bubble radius or universal gas constant, as defined locally	m or J mol⁻¹ K⁻¹
R_E	Incremental ethanol energy return	dimensionless
Re	Reynolds number	dimensionless
$r_P$	Productivity	kg m⁻³ s⁻¹ or equivalent
S, O	Soy base and okara stream masses	kg
T	Absolute or Celsius temperature, as specified	K or °C
t	Time	s
u	Mean liquid velocity	m s⁻¹
$u_{rel}$	Relative velocity responsible for deformation or breakup	m s⁻¹
$u_t$	Throat or restriction velocity	m s⁻¹
UFTG	Unfermented total glucose equivalent	mass concentration
V	Process volume	m³
$V_L$	Total liquid holdup in a recirculating loop	m³
$v_s$	Settling or creaming velocity	m s⁻¹
We	Weber number	dimensionless
$x_p$	Protein mass fraction	kg kg⁻¹
Yp	Protein extraction yield	%
$Y_{P/S}$	Product yield on substrate	kg kg⁻¹
z	Temperature sensitivity parameter in thermal lethality modeling	K
$C_v$	Cavitation number defined from downstream pressure, vapor pressure, density, and restriction velocity	dimensionless
$V_a$	Active internal volume of the cavitation device	m³
τ̄	Mean nominal residence time in the active device	s
$\mathrm{\Delta }{T}_{ad}$	Ideal adiabatic temperature rise from the specified energy input	K

Abbreviations: AA, alpha amylase; CFU, colony forming units; CIP, cleaning in place; CO2, carbon dioxide; DDGS, distillers dried grains with solubles; DSD, droplet size distribution; HC, hydrodynamic cavitation; HPH, high pressure homogenization; HPLC, high performance liquid chromatography; HTD, hydrothermodynamic; MPC, milk protein concentrate; N2, nitrogen; O2, oxygen; PHE, plate heat exchanger; PME, pectin methylesterase; PPO, polyphenol oxidase; PSD, particle size distribution; SSF, simultaneous saccharification and fermentation; UFTG, unfermented total glucose; WPC, whey protein concentrate.

Greek Letters

Table 12.14. Greek letters used in the chapter.

Symbol	Letter name	Meaning
α	alpha	Orifice plate geometry parameter or alpha amylase designation, depending on context
β	beta	Orifice or area ratio parameter, where used in cited studies
γ	gamma	Surface or interfacial tension
Δ	delta	Difference between two states, such as pressure or temperature rise
ε	epsilon	Turbulent energy dissipation rate per unit mass
η	eta	Efficiency, extraction efficiency, or heating efficiency, as subscripted
μ	mu	Dynamic or apparent viscosity, also, the SI prefix micro when preceding a unit
ρ	rho	Density
σ	sigma	Cavitation number
${\sigma }_{mod}$	sigma modified	Geometry adjusted cavitation number for a multi hole plate
τ	tau	Shear stress
τ0	tau zero	Yield stress
τR	tau R	Mean residence time
γ̇	gamma dot	Shear rate

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