Hydrodynamic cavitation coupled with thermal treatment for reducing counts of B. coagulans in skim milk concentrate

Investigation on the cavitation characteristic of a novel cylindrical rotational hydrodynamic cavitation reactor

Hydrodynamic cavitation reactors are of great promise for the applications of chemical process intensification and water treatment. In this work, a novel cylindrical rotational hydrodynamic cavitation reactor (CRHCR) with rectangular grooves and oblique tooth protrusions on the rotor surface was studied. The three-dimensional characterization of cavitation within the CRHCR was observed from the front and left views by the high-speed camera experiments. Interestingly, a new phenomenon of simultaneous formation of the attached cavitation and shear cavitation was found in the CRHCR. The synergistic effect of attached cavitation and shear cavitation contributes to the enhancement of the cavitation performance of CRHCR. In addition, the evolution of attached cavitation is explored. It is found that attached cavitation forms a trapezoidal-shaped cavitation cloud in the groove, which undergoes three various stages: incipient, development, and collapse. Finally, the pulsation frequency and cavitation intensity of shear cavitation in the chamber were investigated. The results show that the cavitation pulsation frequency is the same at the same rotational speed in the chamber near diverse oblique teeth. As the rotational speed increases, the cavitation pulsation frequency increases linearly. These findings in this paper are of great benefit to understanding the mechanism of the cavitation effect of CRHCR.

The innovative technology of dough preparation for bread by the accelerated ion-ozone cavitation method

Due to the fact that bakery, pasta and flour confectionery products are produced mainly from premium or first-grade flour, which is poor in the content of nutrients and fiber, the issue of developing technology for new types of flour products based on whole-ground flour of different fineness is very relevant and in demand. In the production of wholemeal flour, all parts of the whole grain are used-germ, grain shells, and endosperm. Also, recently the shortage of quality wheat has been growing. Therefore, the use of whole-milled flour from low-class wheat varieties will solve the problem of meeting the needs of the population. Using ion-ozone technology for preparing bread, high-quality bakery products from third-class flour with high nutritional and biological value were obtained. Using the obtained system of equations and constraints, the optimal modes of ion-ozone cavitation processing of dough were determined by a nonlinear programming method, which, subject to all the constraints (limitations) on the dough quality, provided the maximum dough strength of y2 = 181.0% and the dough parameter values of C × 10-4 = 25 units/mg, P = 1 atm, and τ = 5 min, which, in compliance with all constraints (restrictions) on the bread quality, provided a maximum volume of z11 = 232.1 cm3. A new innovative technology was created to increase productivity, efficiency and shorten the preparation time of bread. The method of making bread with the effect of ion-ozone cavitation of dough is very important for the bread industry, which affects the effectiveness of whole wheat flour obtained from the lower class of wheat, increases the quality of bread, shortens the technological processes of production, and increases labor productivity indicators. This method increases the economic efficiency of bread-making industries and the productivity of bread.

Non-thermal, energy efficient hydrodynamic cavitation for food processing, process intensification and extraction of natural bioactives: A review

Hydrodynamic cavitation (HC) is the process of bubbles formation, expansion, and violent collapse, which results in the generation of high pressures in the order of 100-5000 bar and temperatures in the range of 727-9727 °C for just a fraction of seconds. Increasing consumer demand for high-quality foods with higher nutritive values and fresh-like sensory attributes, food processors, scientists, and process engineers are pushed to develop innovative and effective non-thermal methods as an alternative to conventional heat treatments. Hydrodynamic cavitation can play a significant role in non-thermal food processing as it has the potential to destroy microbes and reduce enzyme activity while retaining essential nutritional and physicochemical properties. As hydrodynamic cavitation occurs in a flowing liquid, there is a decrease in local pressure followed by its recovery; hence it can be used for liquid foods. It can also be used to create stable emulsions and homogenize food constituents. Moreover, this technology can extract food constituents such as polyphenols, essential oils, pigments, etc., via biomass pretreatment, cell disruption for selective enzyme release, waste valorization, and beer brewing. Other applications related to food production include water treatment, biodiesel, and biogas production. The present review discusses the application of HC in the preservation, processing, and quality improvement of food and other related applications. The reviewed examples in this paper demonstrate the potential of hydrodynamic cavitation with further expansion toward the scaling up, which looks at commercialization as a driving force.

Ultrasound-Assisted Cavitation Effect on the Biofilm-Forming Ability of Common Dairy Sporeformers

Thermoduric sporeformers survive heat treatment and can form biofilm on contact food surfaces that is difficult to clean and may cause cross contamination to milk products. It was hypothesized that cavitation would influence sporeformers’ ability to attach to contact surfaces and form biofilm. Common dairy sporeformers of Geobacillus stearothermophilus, Bacillus licheniformis, and Bacillus sporothermodurans were individually inoculated in sterile skim milk at the levels of 6.0 log CFU/mL. Inoculated samples were treated by cavitation at 80% amplitudes for 10 min each. Pre and post samples were used to develop biofilms on stainless steel coupons under static conditions. Scanning electron micrograph was used to observe the developed biofilms. All the experiments were conducted in triplicate and were statistically analyzed using a t test. The average counts of spiked milk samples were 7.2, 8.0, and 7.7 logs CFU/mL, respectively, for the three sporeformers. Post-cavitation counts were reduced significantly to 3.4, 4.2, and 3.7 logs CFU/mL, respectively. Pre-cavitation biofilm counts of the three sporeformers were 5.35, 6.42, and 6.5 logs CFU/ cm2, respectively in 72 h. The three sporeformers’ biofilm showed significantly (p < 0.05) lower counts after cavitation of 4.39, 5.44, and lower counts of 4.39 logs CFU/cm2, respectively, for the three organisms. The result showed that G. stearothermophilus formed the least biofilms among others after cavitation. Although the ultrasonication treatment reduced the number of sporeformer bacteria, the survivors still retained the ability to attach to the stainless-steel food contact surfaces.

Removal of antibiotics from milk via ozonation in a vortex reactor

Antibiotics (ABX) residues occur frequently in milk, causing considerable wastage of medicated milk and serious economic losses, and making the issue a burden for the dairy industry. Improper disposal of medicated milk harms dairy production, animal welfare, and the environment. This work studies the use of ozonation in a vortex reactor for removing ceftiofur hydrochloride (CEF), sulfamonomethoxine sodium (SMM), marbofloxacin (MAR) and oxytetracycline (OTC) from milk. In terms of residual concentration, O₃ efficiency and the degradation kinetics of the various O₃-involving processes in the vortex reactor, ABX removal via ozonation is better using stronger vortexing, which induces hydrodynamic cavitation. CEF undergoes the fastest degradation, followed by SMM, MAR, and OTC. High ABX hydrophobicity favors ABX degradation via ozonation, O₃/H₂O₂, and O₃/Na₂S₂O₈. ABX oxidation by ^•OH at the O₃ gas-bubble/milk interface is the principle degradation pathway, except for MAR. ABX degradation follows pseudo-first-order kinetics and is affected by initial ABX concentration, O₃ concentration/flow rate, reaction temperature, and milk components to varying degrees. Under optimal ozonation conditions, ABX residues meet the maximum limits as set by the European Commission and no antimicrobial activity was observed. The decontaminated milk was therefore suggested to be reused as calf food, animal feed, organic fertilizer, etc.

Multi-objective optimization of the cavitation generation unit structure of an advanced rotational hydrodynamic cavitation reactor

Hydrodynamic cavitation (HC) has been widely considered a promising technique for industrial-scale process intensifications. The effectiveness of HC is determined by the performance of hydrodynamic cavitation reactors (HCRs). The advanced rotational HCRs (ARHCRs) proposed recently have shown superior performance in various applications, while the research on the structural optimization is still absent. The present study, for the first time, identifies optimal structures of the cavitation generation units of a representative ARHCR by combining genetic algorithm (GA) and computational fluid dynamics, with the objectives of maximizing the total vapor volume, V_vapor , and minimizing the total torque of the rotor wall, M→_z . Four important geometrical factors, namely, diameter (D), interaction distance (s), height (h), and inclination angle (θ), were specified as the design variables. Two high-performance fitness functions for V_vapor and M→_z were established from a central composite design with 25 cases. After performing 10,001 simulations of GA, a Pareto front with 1630 non-dominated points was obtained. The results reveal that the values of s and θ of the Pareto front concentrated on their lower (i.e., 1.5 mm) and upper limits (i.e., 18.75°), respectively, while the values of D and h were scattered in their variation regions. In comparison to the original model, a representative global optimal point increased the V_vapor by 156% and decreased the M→_z by 14%. The corresponding improved mechanism was revealed by analyzing the flow field. The findings of this work can strongly support the fundamental understanding, design, and application of ARHCRs for process intensifications.