Microwave Pasteurization Research Articles

Designing and developing a programmable in vitro gastrointestinal model to assess the impact of pasteurization on the bioaccessibility of lycopene nanoparticles

To evaluate potential health impact of engineered nanoparticles, evaluation of digestion effect is necessary. Digestion requires micro-management and sequential execution of complex enzymatic mechanisms with controlled human digestion environment. The objective of this study was to develop an automated in-vitro digestive system to assess bio-accessibility of encapsulated lycopene nanoparticles in model fruit juice. Lycopene was encapsulated in polylactic acid (PLA-LNP) and polylactic co-glycolic acid (PLGA-LNP) and evaluated the bio-accessibility in a programmable in-vitro human digestive system operated with high sensitivity (25–30μs) and volume accuracy (97.37–100%). Pasteurized Model juice containing PLA-LNP, revealing higher bio-accessibility (100%) compared to PLGA-LNP (73%) counterparts. Absorption profile of both types of nanoparticles followed Korsmeyer-Peppas diffusion model at R2 value of 0.98. All types of nanoparticles with different treatments followed non-Fickian types of diffusion except PLGA-PLA with microwave pasteurization. This automated in-vitro digestive system holds significant potential for advancing drug discovery and delivery studies in the future.

Application of an Electromagnetic Field for Extending the Shelf-Life of Not from Concentrate (NFC) Apple Juice

The research material consisted of not from concentrate (NFC) apple juice, which underwent innovative processes of spray deaeration and flow microwave pasteurization. Traditional commercially available pasteurization was the control. Deaeration was conducted at two different temperatures (25 °C and 50 °C) and three rotational speeds of the spray disc (150 rpm, 450 rpm, 750 rpm). Flow microwave pasteurization was carried out at 90 °C with a flow rate of 5.8 L/min. Deaeration at a temperature of 25 °C and a rotation speed of 150 rpm resulted in a significant reduction in oxygen levels in the juice to 0.9 mg/L. Microwave pasteurization led to an almost 100% reduction in oxidoreductases activity (PPO, POD). Immediately after the process, microwave-pasteurized juice exhibited better stability of the total polyphenol content, with a TPC of 73.8 mg/100 mL. Microwave pasteurization caused a threefold increase in antioxidant capacity (176.8 µM/100 mL) compared to fresh juice. The color of microwave-pasteurized juice was more appealing than that of traditionally pasteurized juice.

Investigation of Dielectric Properties of Potato, Tomato and Onion Juices at Microwave Frequencies

The dielectric properties of fresh juices of Solanum tuberosum (potato), Solanum lycopersicum (tomato) and Allium cepa (onion) were measured in terms of the dielectric constant and dielectric loss factor, over a frequency range from 1 to 50 GHz and at temperatures ranging from 30 to 60 °C, by using the PNA network analyzer model E8364C and open-ended coaxial probe 85070E. A prediction of relaxation frequencies of molecules for the three different juices was done and their molecular behavior was then studied by plotting dielectric constant vs. frequency and dielectric loss factor vs. frequency curves in the frequency range from 1 to 50 GHz at four different temperatures from 30 to 60 °C. The dielectric properties of food products play a crucial role in determining their heating behavior when subjected to an electromagnetic field. Understanding these properties is essential for the development of microwave pasteurization and sterilization processes tailored to various food products.

Continuous flow microwave processing of liquid whole egg: Pasteurization and functional characteristics evaluation

The objective of this study was to assess the impact of continuous flow microwave processing on the pasteurization efficiency and quality attributes of liquid whole egg (LWE). The heating section was accomplished using microwave, while the holding section utilized a water bath, and the process parameters were determined by a developed numerical model. The inactivation kinetics of Escherichia coli, Staphylococcus aureus, and Salmonella Enteritidis were evaluated at three temperatures (56, 60 and 64 °C) and two power-density (8 and 16 W/mL with different flow rates). A 5-log10 reduction was achieved and the Weibull model fitting the survival data well, which contributed to the optimization of microwave pasteurization process. Additionally, microwave promoted the transitions of secondary structures from β-sheet to α-helix and stabilised the system by enhancing the zeta potential value, further improving the emulsifying and foaming properties. The major proteins in LWE were not found to undergo degradation according to the results obtained from SDS-PAGE analysis. The results of this study suggested that continuous flow microwave pasteurization of LWE exhibits potential as a viable alternative to conventional pasteurization methods. Industrial relevanceThe adoption of high-efficiency physical processing methods is imperative for the sustainable and low-carbon advancement of the food industry. This study confirmed the feasibility of continuous flow microwave pasteurization as an alternative to conventional methods for liquid whole egg, addressing key limitations encountered in traditional pasteurization approaches, and the findings offer practical insights for industrial-scale production. Additionally, the development and application of a continuous flow microwave heating system for pasteurizing liquid whole egg provide valuable knowledge for the utilization of microwave treatment in processing high-viscosity and heat-sensitive fluid foods.

Cooked rice safety: A review of status and potential of radiative pasteurization

AbstractMicrobial contamination in cooked rice‐based foods poses a global concern due to rice's widespread consumption. This review aims to consolidate information on harmful microorganisms associated with such foods from various countries and their adverse effects on consumers. Additionally, it explores the reported causes of microbial contamination in cooked rice‐based dishes and proposes an intervention strategy for safer consumption. The findings highlight that ready‐to‐eat cooked rice‐based foods may harbor unsafe levels of microorganisms like Bacillus cereus, Staphylococcus aureus, and Aspergillus spp. A recommended solution is the application of microwave pasteurization. This method involves cooking rice in pasteurized packaging, minimizing human contact, and effectively controlling harmful microorganisms. Microwave pasteurization emerges as a promising approach to ensure the safe consumption of cooked rice‐based foods by reducing microbial contamination levels.

Effect of clarification on some characteristics of pomegranate juice processed by two different methods during storage

This study aimed to assess the effectiveness of two clarifying procedures and their effects on some properties in thermally or microwave-pasteurized pomegranate juices. The experiment consisted in combining pectinase and protease as well as chitosan and gelatin once they were being stored in the refrigerator. The experiment consisted in three parts, being the first one a fresh juice without any clarification treatment, whereas, the second one was the fresh juice treated with clarifying agent consisted of pectinase and protease mixture ratio (2:1) at 0.75 v/v,and 50 °C for 20 min. Finally, the third one was fresh juice treated with chitosan and gelatin mixture at 0.4 and 0.8) g/L, respectively, at 50 °C for (20) min. The pasteurization of all three experiments was done by using two techniques, i.e., one with thermal water bath at 85 °C for two min and the microwave at 400 Watts for two min. All pomegranate juice bottles were stored at 4 °C for three months. The results showed a significant effect of the clarification method variable on the properties studied, especially turbidity, polyphenol and anthocyanin values. Moreover, the juice clarified with the enzymatic clarification method had better characteristics than the traditional ones during storage, what has therefore a better commercial appeal. The area of significance was founded with the use of traditional clarification with concentration at (0.4 and 0.8) g/l, and microwave pasteurization with 400 watts and zero month of storage at 4 °C, respectively, which is provided a minimum turbidity value.

Effects of Microwave Pasteurization on the Quality and Shelf-Life of Low-Sodium and Intermediate-Moisture Pacific Saury (Cololabis saira).

The objective of this study was to investigate the effects of microwave pasteurization on the quality and shelf-life of low-sodium and intermediate-moisture Pacific saury. Microwave pasteurization was used to process low-sodium (1.07% ± 0.06%) and intermediate-moisture saury (moisture content 30% ± 2%, water activity 0.810 ± 0.010) to produce high-quality ready-to-eat food stored at room temperature. Retort pasteurization with the same thermal processing level of F90 = 10 min was used for comparison. Results showed that microwave pasteurization had significantly (p < 0.001) shorter processing times (9.23 ± 0.19 min) compared with traditional retort pasteurization (17.43 ± 0.32 min). The cook value (C) and thiobarbituric acid (TBARS) content of microwave-pasteurized saury were significantly lower than that of retort-pasteurized saury (p < 0.05). With more microbial inactivation, microwave pasteurization brought better overall texture than retort processing. After 7 days of storage at 37 °C, the total plate count (TPC) and TBARS of microwave pasteurized saury still met the edible standard, while the TPC of retort pasteurized saury no longer did. These results showed that the combined processing of microwave pasteurization and mild drying (Aw < 0.85) could produce high-quality ready-to-eat saury products. These results indicate a new methodology for producing high-quality products stored at room temperature.

A comparative study of high-pressure processing and microwave pasteurisation on the formation of hydroxymethylfurfural in stingless bee (Heterotrigona itama) honey

A comparative study of high-pressure processing and microwave pasteurisation on the formation of hydroxymethylfurfural in stingless bee (Heterotrigona itama) honey

The Effect of Microwave Radiation on the Green Color Loss of Green Tea Powder.

Microwave radiation is one of the main heating methods for food processing, especially affecting the color quality of colorful foods. This work presents the effect of microwave radiation on the green color loss of green tea powder (GTP) by the color description (L*, a*, b*, and Ha of green tea powder, L*:whiteness/darkness, a*: redness/greenness, and b*: yellowness/blueness; Ha derived from Hunter a and b could visually describe the color space) of the Hunter color system. First, the L*, a*, and b* were determined from the GTP samples treated with various microwave powers with the change of time to investigate the kinetic of color loss. Then, the L*, a*, and b*and temperature of GTP samples with serious thickness treated with constant microwave power (700 W) for a different time were determined to study the effect of sample thickness on the color loss. Finally, the chemicals that contributed to color change in the GTP samples treated with mild, moderate, and severe radiation were analyzed. The results showed that L*, |a*| (|a*|was the absolute value of a*), b*, and Ha decreased with the power increase in microwave radiation, and their changes conformed to the first-order kinetics. The activation energies (Ea) of different thickness GTP for change of L*, a*, b*, and Ha values could be predicted with the fitting models, and Ea for 20 mm-thick GTP were approximately 1/5, 1/8, 1/8, and 1/13 of those for 4 mm-thick GTP. The color loss was mainly caused by the Mg2+ loss of chlorophylls and the formation of derivates under mild radiation, the degradation of chlorophylls and the formation of theaflavin from catechins under moderate radiation, and the degradation of chlorophylls and their derivates accompanied by Maillard reaction between reducing sugar and amino acids under severe radiation. The results indicate that sample thickness and radiation time are two key parameters to keeping the color of GTP in food processing and microwave pasteurization.

Pasteurization of egg white by integrating ultrasound and microwave: Effect on structure and functional properties

Microwave (MW) pasteurization is an efficient and energy saving technology, but it has the disadvantage of thermal inhomogeneity. This study reduced the inhomogeneity of pasteurization by integrating ultrasound and microwave (IUM) treatment, and decreased adverse effect on the functional properties of liquid egg white (LEW) while ensuring the pasteurization effect. The particle size increased by 48.5 nm after IUM treatment, indicating egg white protein was slightly denatured and aggregated. However, the secondary structure changed little. Compared with traditional pasteurized LEW, lower apparent viscosity, higher zeta potential value and hydrophobicity of LEW treated by IUM (IUM-LEW) made the functional properties maintained or improved. Emulsification capacity (EC), emulsification stability (ES) and gel strength of IUM-LEW were increased by 6.83%, 7.41% and 77 g, respectively. This study provided an alternative to traditional pasteurization for LEW.

Critical assessment of methods for measurement of temperature profiles and heat load history in microwave heating processes-A review.

Limitations of microwave processing due to inhomogeneities of power input and energy absorption have been widely described. Over- and underheated product areas influence reproducibility, product quality, and possibly safety. Although a broad range of methods is available for temperature measurement and evaluation of time/temperature effects, none of them is sufficiently able to detect temperature differences and thermally induced effects within the product caused by inhomogeneous heating. The purpose of this review is to critically assess different methods of temperature measurement for their suitability for different microwave applications, namely metallic temperature sensors, thermal imaging, pyrometer measurement, fiber optic sensors, microwave radiometry, magnetic resonance imaging, liquid crystal thermography, thermal paper, and biological and chemical time-temperature indicators. These methods are evaluated according to their advantages and limitations, method characteristics, and potential interference with the electric field. Special attention is given to spatial resolution, accuracy, handling, and purpose of measurement, that is, development work or online production control. Differences of methods and examples of practical application and failure in microwave-assisted food processing are discussed with a special focus on microwave pasteurization and microwave-assisted drying. Based on this assessment, it is suggested that infrared cameras for measuring temperature distribution at the product surface and partially inside the product in combination with a chemical time/temperature indicator (e.g., Maillard reaction, generating heat-induced color variations, depending on local energy absorption) appear to be the most appropriate system for future practical application in microwave food process control, microwave system development, and product design. Reliable detection of inhomogeneous heating is a prerequisite to counteracte inhomogeneity by a targeted adjustment of process and product parameters in microwave applications.

Temperature and Moisture Dependent Dielectric and Thermal Properties of Walnut Components Associated with Radio Frequency and Microwave Pasteurization.

To provide necessary information for further pasteurization experiments and computer simulations based on radio frequency (RF) and microwave (MW) energy, dielectric and thermal properties of walnut components were measured at frequencies between 10 and 3000 MHz, temperatures between 20 and 80 °C, and moisture contents of whole walnuts between 8.04% and 20.01% on a dry basis (d.b.). Results demonstrated that dielectric constants and loss factors of walnut kernels and shells decreased dramatically with raised frequency within the RF range from 10 to 300 MHz, but then reduced slightly within the MW range from 300 to 3000 MHz. Dielectric constant, loss factor, specific heat capacity, and thermal conductivity increased with raised temperature and moisture content. Dielectric loss factors of kernels were greater than those of shells, leading to a higher RF or MW heating rate. Penetration depth of electromagnetic waves in walnut components was found to be greater at lower frequencies, temperatures, and moisture contents. The established regression models with experimental results could predict both dielectric and thermal properties with large coefficients of determination (R2 > 0.966). Therefore, this study offered essential data and effective guidance in developing and optimizing RF and MW pasteurization techniques for walnuts using both experiments and mathematical simulations.

Optimisation of heating uniformity for milk pasteurisation using microwave coaxial slot applicator system

Microwave heating is a novel solution for milk pasteurisation but the non-uniformity of thermal distribution is still a significant problem that hampers its application especially for milk pasteurisation. This paper reports on the isotherm heating of a coaxial slot antenna applicator with a microwave signal generation using a fabricated mono-mode microwave system designed to improve the temperature uniformity of batch milk pasteurisation. In this paper, applicator simulation, design, characterisation, and fabrication are described in detail. The fabricated microwave pasteurisation system was implemented using a digitally controlled water-cooled magnetron with a waveguide circulator, a three-screw waveguide tuner, a water-based waveguide terminator, and a rectangular to coaxial adapter to channel the output. The impedance matching and power calibration routines of the fabricated microwave pasteurisation system are explained and analysed in detail. Three microwave powers, namely 100 W, 125 W and 150 W were used to test and characterise the pasteurisation performance of the system. For each microwave power the thermal profile and the temperature distribution of the 100 ml milk samples in a glass beaker were simulated and measured. The pasteurisation process was evaluated based on the aerobic plate count (APC) test. Results showed 90% improvement in the temperature uniformity as compared with an existing batch microwave pasteurisation method. The APC test showed pasteurisation efficiency was 99.999% and total microbial elimination occurred after 7 min, 6 min, and 5 min of heating using 100 W, 125 W, and 150 W power respectively. • Microwave pasteurisation will preserve the taste, colour, and nutrition of cow's milk. • Mono-mode microwave heating saves energy costs and reduces heating time. • Uniformity in heating will guarantee the quality of milk pasteurization. • Dielectric loss factor determines heating efficiency of microwave heating technique. • Dielectric loss factor is a temperature and frequency dependent parameter.

Computational study for microwave pasteurization of beer and hypothetical continuous flow system design

Beer pasteurization is carried out in conventional systems where low temperature and long time process (56 min process with 13 min pre-heating, 14 min heating, 6 min holding time and 23 min cooling time) is applied for bottled or canned products. Longer process times lead to losses in the sensory properties. Another approach is flash pasteurization where the beer is first pasteurized and then filled into bottles or cans. For flash pasteurization, microwave (MW) process with rapid heating feature might be an innovative alternative. Therefore, the objective of this study was to explore the MW processing for beer pasteurization. For this purpose, a computational mathematical model was developed to determine the temperature change of beer during MW process and experimentally validated in a 2450 MHz lab-scale system. Following the validation, process design studies for a continuous flow system were carried out. These studies demonstrated the MW application as a rapid process (e.g. 60 s of total MW heating time at 5000 W with a short holding time of 27 s) to achieve the required pasteurization unit at a flow rate of 50.4 kg/h. This confirmed the MW process as a possible industrial application. Using these results, continuous flow process optimization studies for industrial process considerations might be planned.

Inactivation of Zygosaccharomyces rouxii in organic intermediate moisture apricot and fig by microwave pasteurization

Zygosaccharomyces rouxii is an osmotolerant yeast that is responsible for the spoilage of high sugar content foods. Microwave heating technology is used as an alternative to conventional pasteurization. Main purpose of this research was to determine the thermal resistance of Z. rouxii in organic intermediate moisture content (IMC) fruits (apricot and fig) during the microwave pasteurization process and comparing the D, z and F values with the conventional method. F85 values were calculated both theoretically and experimentally. Additionally, the effects of the pasteurization methods on the quality properties (total soluble solid, pH, acidity, water activity, moisture content, rehydration capacity, weight loss, hydroxymethylfurfural (HMF) and color) of the samples were investigated. The results show that come up time (CUT) and D values were significantly reduced by microwave treatment. The yeast reached a five log10 reduction by the microwave heating method with the F8533.8 value of 3.6 min for apricot and F8532.15 value of 3.35 min for fig. Total soluble solids, weight loss, and color values were preserved better in microwave pasteurization than the conventional method in both samples. Hydroxymethylfurfural content of the microwave pasteurized samples was 23.5% and 32% less than the samples pasteurized conventionally for apricot and fig samples, respectively.

Sequential Microwave – Ultrasound assisted extraction of soymilk and optimization of extraction process

In the present study, a combination of microwave and thermosonication treatment was introduced in the soymilk extraction process, and the process was optimized to minimize the enzymatic activity of Soybean Trypsin Inhibitor (STI) and Lipoxygenase (LOX) enzymes. Protein content, fat content, TSS (Total Soluble Solids), and viscosity of soymilk increased upon thermosonication process and was most affected by microwave time followed by ultrasonification time. The inactivation rate constant for STI and LOX was 0.2034 min−1 and 0.3232 min−1, respectively, indicating LOX was more susceptible to inactivation under microwave treatment as compared to STI. The activation energy of STI and LOX decreased from 48.44 to 10.24 kJ/mol and 53.47 to 3.07 kJ/mol after 5 min of microwave pasteurization. FTIR analysis confirmed the conformational deformation of proteins and enhanced molecular interactions in the optimized soymilk. The optimized condition was obtained as 3 min of microwave pasteurization followed by 30 min of ultrasonication at 60 °C in an ultrasonic bath of 28 ± 2 kHz frequency. The optimized treatment produced the soymilk with enhanced nutritional quality and low enzymatic activities.

Influence of heating rate during microwave pasteurization of ground beef products: Experimental and numerical study

AbstractA finite element model coupling electromagnetism with standing‐wave propagation, heat transfer and microbial inactivation equations has been developed to study microwave food pasteurization with three heating rates (7, 10, and 13°C/min). Inactivation of a target microorganism was studied from a single temperature measurement at a given location. Electric fields, temperature distribution and inactivation kinetics were predicted as a function of time and space coordinates. Good agreement was found between experimental and predicted thermal and inactivation curves. The inactivation kinetics parameters (D and z‐value) identified under water bath heating remained valid during the microwave process. Thus, the E. coli inactivation is mainly due to the thermal effect under lethal conditions. The differences between logarithmic reductions between both heating processes was attributed to the non‐uniform temperature distribution.Practical ApplicationsFrom the industrial point of view, temperature heterogeneity is known to be the main barrier impeding the development of microwave food pasteurization technology. The use of a multiphysics model that takes into account the real geometry of the microwave cavity made it possible to optimize the process and achieve a more uniform temperature distribution within the product. Therefore, the simulation of the electric field distribution can provide relevant information on the amplitude and shape of the electromagnetic field. The degrees of freedom of the model led to the optimization of parameters, such as cavity size, microwave frequency shifting, product mass, the position of the sample in the cavity, and the optimization of the shape of the product containers and supports. The combination of microwaves (with or without modulated power input) with other energy sources (i.e., hot air injection, immersion of the product in water) also seemed promising for pasteurization applications.

Comprehensive investigation into quality of pasteurized Oncorhynchus keta Walbaum fillets and non-thermal effects of microwave

Microwave processing is a novel technology in shortening food processing time and improving product quality. These advantages are achieved through the thermal and possible non-thermal effects of microwave. The main objective of the study was to explore the non-thermal effects of microwave electromagnetic (EM) fields on quality traits of pasteurized Oncorhynchus keta Walbaum fillets. A single-mode microwave processing system processed the fillets with a pasteurization thermal lethality value of F90 = 10 min. Corresponding pasteurization process with synchronous heating was designed to match the time-temperature profile of microwave processing. Retort pasteurization was used as a conventional process to compare the fillet quality performance with microwave pasteurization. With the pasteurization thermal treatment level, the proportion of six free amino acids was significantly different (P < 0.05) between the microwave pasteurized fillets and synchronous heating pasteurized fillets. The result could be attributed to the non-thermal effects of microwave EM fields. Compared with the retort pasteurization, the microwave process performed better in overall quality. Results suggested that microwave pasteurization exerted non-thermal effects in individual quality traits and caused less damage to fillet quality than the retort process in overall quality.

Effects of microwave pasteurization on the thermal resistance of Zygosaccharomyces rouxii and on the physicochemical properties of organic intermediate moisture raisin

In this study, organic intermediate moisture raisin was pasteurized with microwave and conventional pasteurization methods. The thermal resistance (D and z values) of the target yeast, Zygosaccharomyces rouxii, was determined for both methods at different temperatures 60°C, 70°C, and 80°C and at different time intervals. The effect of pasteurization methods on the quality properties of raisin samples was investigated. The D values of Z. rouxii were found as 6.50 ± 0.49, 2.96 ± 0.02, 1.91 ± 0.01 min for conventional treatment and 3.46 ± 0.31, 2.02 ± 0.14 and 1 ± 0.01 min for microwave treatment at 60℃, 70℃, and 80℃, respectively. F8537 values for 5-log reduction and come-up time significantly decreased after microwave pasteurization. Brix, acidity, and color values were preserved better by microwave treatment. Hydroxymethylfurfural content of the microwave pasteurized samples was found 42% less than the samples pasteurized conventionally. Microwave pasteurization can be alternatively used for the conventional method for raisin improving quality with less heating time. Practical applications Microwave heating needs less come-up time rather than conventional pasteurization. Decreasing process time provides advantageous via the costs and energy saving so organic intermediate moisture fruits that are perishable can be safely pasteurized by a microwave method for longer shelf life in the industry. Z. rouxii, which may be found in high sugar content foods, can be inactivated to the target log that provides the fruit safe by using this method. In addition, quality properties, such as color, which is effective on the consumer preference also, protected better by the effect of volumetric heating.

Neurotrophic Factors in Human Milk in Early Lactation and the Effect of Holder and Microwave Pasteurization on Their Concentrations.

The objective of this study was to determine the level of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) in human milk in the first 2 weeks of breast-feeding and compare the effects of Holder pasteurization (HoP, 62.5 °C, 30 minutes) and microwave pasteurization (MP) at constant temperature (62.5 °C) on the concentraion of both neurotrophic factors (NFs). Concentration of NFs in human milk was determined using a commercially available ELISA assay. The average concentration of BDNF and GDNF in milk was 11 ± 6 ng/mL and 336 ± 238 pg/mL, respectively. There was a positive correlation between the concentrations of BDNF and GDNF in human milk and day of lactation (r = 0.441, P < 0.05 and r = 0.482, P < 0.05, respectively). In addition, there was a significant correlation between the levels of BDNF and GDNF (r = 0.366, P < 0.05). HoP and MP for 10 minutes affected both NF levels similarly, causing degradation of BDNF by about 24% and 17%, and GDNF by 47% and 45%, respectively. Use of MP for 5 minutes resulted in preservation of nearly 91% BDNF and 79% GDNF in human milk. In the pasteurization processes carried out, results showed that GDNF is more susceptible to degradation under the influence of high temperature. To the authors' best knowledge, this is the first study evaluating the effects of HoP and MP at constant temperature on the concentration of NFs in human milk. It was found that the MP for 5 minutes is the optimal method.