Unlocking Potentials of Microwaves for Food Safety and Quality

Effects of thermal processing on natural antioxidants in fruits and vegetables

Research on the content of polyphenolic compounds in fruits and vegetables, the extraction of bioactive compounds, and the study of their impact on the human body has received growing attention in recent years. This is due to the great interest in bioactive compounds and their health benefits, resulting in increased market demand for natural foods. Bioactive compounds from plants are generally categorized as natural antioxidants with health benefits such as anti-inflammatory, antioxidant, anti-diabetic, anti-carcinogenic, etc. Thermal processing has been used in the food sector for a long history. Implementing different thermal processing methods could be essential in retaining the quality of the natural antioxidant compounds in plant-based foods. A comprehensive review is presented on the effects of thermal blanching (i.e., hot water, steam, superheated steam impingement, ohmic and microwave blanching), pasteurization, and sterilization and drying technologies on natural antioxidants in fruits and vegetables.

Extraction of polyphenols and essential oils from herbs with green extraction methods - An insightful review

The demand for polyphenols and essential oils (EOs) on the food market is high and grows every year. Its partially the result of the fact that these compounds can be used in formulation of clean label foods, a fast growing food sector. A significant share of polyphenols and EOs are extracted from herbs. The quality of the extracts is determined mainly by the extraction method. Conventional extraction techniques of phytochemicals are time-consuming, operate at high temperatures, and require usage of organic solvents and energy in large quantities. According to the United Nations Sustainability Development Plan, chemical processes should be replaced by green alternatives that would reduce the use of solvents and energy. Ultrasound-Assisted Extraction (UAE), Microwave-Assisted Extraction (MAE) and Cold Plasma-Assisted Extraction (CPAE) meets these criteria. The review shows that each of these techniques seems to be a great alternative for conventional extraction methods ensuring higher yields of bioactive compounds.

Analysis of the Effects of Microwave Combined Induction Heating on Steamed Pork with Rice Powder

This study investigates the application of microwave combined induction heating (MCIH) to steam ready-to-eat pork with rice powder, emphasizing the advantages of rapid and uniform heating. The experimental setup included a mixture of 180 g pork strips, 30 g rice powder, and 10 g water in a CPET tray using MCIH with 1080 W microwave (MW) and 130 °C induction heating (IH) for 150 s. The results showed a quick temperature increase rate of 0.56 °C/s that achieved pasteurization against a variety of pathogenic bacteria, such as Listeria monocytogenes, but not Clostridium botulinum, by lethality calculation. Compared to typical electric cooker steaming, MCIH significantly shortened cooking time (8.6 times faster). To address rice starch gelatinization, two-stage heating techniques to steam pork with rice powder were MCIH: 150 s, and then IH: 60 s (MW1), and MCIH: 180 s, and then IH: 30 s (MW2), with no significant differences seen in color or the nine-point taste scale between treatment groups. MCIH groups had smaller shear forces than control. After MCIH cooking, no microbial counts were detected in the MW1 and MW2 groups initially, and the pork with rice powder had a shelf life of 14 days at 4 °C based on aerobic plate count assay.

Sensory Perception and Food-Evoked Emotions of Older Adults Assessing Microwave-Processed Meals with Different Salt Concentrations

This study employed a home-use test to explore the sensory perception and evoked emotions of older adults in the assessment of chicken pasta meals with different salt concentrations. Ready-to-eat (RTE) meals with three salt levels (100%, 75%, and 50%) and two treatments-with and without added herbs-were tested. Multiple sensory attributes and overall meal liking were evaluated by participants (n = 54; 60-86 years of age) with hedonic and just-about-right scores. Twenty-five food-evoked emotions were also tested. Sensory results suggested a 50% salt reduction is possible with minimal impact on the overall liking, while a 25% salt reduction did not affect the saltiness and flavor liking of the meals. Herb addition positively impacted the aroma, flavor, and spiciness liking of the meals. The emotions that differed (p < 0.05) among meals were active, aggressive, bored, calm, happy, and wild, with the meals with herbs added eliciting more positive emotions. A questionnaire elicited information about participants' interest in healthy eating, food technology neophobia, and picky behaviors to determine the influence of these factors on participants' salt consumption habits. Sensory acceptance data combined with questionnaires explored what influenced this group of older adults in their acceptance of and interest in RTE meals.

Heating performance of dual-source microwave heating using different frequency shifting strategies in a solid-state system

Solid-state microwave heating holds potential in mitigating the issue of nonuniform heating commonly observed in magnetron-based microwave ovens. Previous work on solid-state application primarily focused on single-source microwave heating and modeling of dual-source heating with fixed frequency combinations. This study experimentally investigated the port interactions and heating performance of four different frequency shifting approaches (in range of 2.4 and 2.5 GHz, at an interval of 0.01 GHz), i.e., Fixed-frequency without shifting, Synchronized-shifting, Inverse-shifting and Distinct-shifting, in a dual-source microwave system under both stationary and rotatory conditions. Results showed that port interactions were dependent on the microwave frequency and load position, both of which significantly affected the microwave power efficiency. All three shifting strategies significantly improved heating performance compared to the Fixed-frequency heating. Additionally, the use of a turntable in our dual-source microwave configuration did not improve the heating uniformity in the context of various frequency shifting processes, suggesting that the inclusion of a turntable might be dispensable in solid-state microwave systems if proper multi-port frequency shifting strategy could deliver more uniform heating.

Unlocking the Potential of Microwave Sterilization Technology in Ready-to-Eat Imitation Crab Meat Production

Microwave sterilization is a novel potential sterilization technology to improve food quality. An industrial microwave sterilization system was used to sterilize imitation crab meat under thermal processing intensity F0 = 1, 2, 3. The characteristics of the microwave process, such as heating rate, processing time, and C100, were calculated. In addition, the quality of processed imitation crab meat was investigated. Compared with the conventional retort method, microwave sterilization significantly shortened the processing time of imitation crab meat by 63.71% to 72.45%. Under the same thermal processing intensity, microwave sterilization has demonstrated better results than retort sterilization in terms of water-holding capacity, color, and texture. Furthermore, microwave-treated imitation crab meat ingredients had a greater capacity to bind water molecules and obtained a more appropriate secondary protein structure. In addition, microwave technology can better preserve the unsaturated fatty acids (UFA) of imitation crab meat, which are 9.14%, 1.19%, and 0.32% higher than the traditional method at F0 = 1, 2, 3. The results would provide useful data for the subsequent research and development of ready-to-eat surimi products.

Theoretical reasons for rapid heating of vegetable oils by microwaves

Water and high-moisture foods are readily heated in microwaves due to their relatively high dielectric loss factors. Vegetable oil, on the other hand, has a much smaller loss factor (about 1/100th that of water), and is generally believed to be unsuitable for microwave heating. In this study, we conducted experiments to compare heating rates between vegetable oil and pure water in a 2450 MHz microwave oven. We found that the vegetable oil samples were heated rapidly in microwaves, and even faster (1.4-2.0 times) than the water samples. To provide a theoretical explanation, we developed a 3-D computer simulation model. The simulation revealed an approximately 10-fold stronger electric field in oil compared to water, resulting in a similar amount of microwave power being absorbed by the oil and water samples. As the absorbed microwave power was converted into thermal energy, the oil samples were heated faster due to their smaller specific heat (1/2 that of water). But we also found that when the dimensions of oil are smaller than half the microwave wavelength, oil is heated slower than water due to the absence of hot spot areas. This study provides a theoretical explanation for microwave heating of vegetable oils and demonstrates opportunities for utilizing microwave energy to electrify industrial heating of vegetable oils.

A review on the frying process: Methods, models and their mechanism and application in the food industry

Frying is one of the most popular and traditional processes used in the food industry and food services to manufacture products that are high in quality and with unique sensory characteristics. The most common method of frying is deep-fat frying, used worldwide due to its distinct flavor profile and sensory aspects, which leads to physio-chemical changes at both macro and micro levels. One of the major concerns with deep-fried foods is their high oil content, and a variety of metabolic disorders can be caused by overconsumption of these foods, including heart disease, obesity, and high cholesterol. Due to their enticing organoleptic properties with their delicious flavor, pleasing mouthfeel, and unique taste, making them irresistible, it is also responsible for undesirable and unacceptable characteristics for consumers. Oil absorption can be reduced by developing novel frying methods that limit the amount of oil in products, producing products with fewer calories and oil while maintaining similar quality, flavor, and edibility. In addition, different pretreatments and post-frying treatments are applied to achieve a synergistic effect. The transfer of mass and heat occurs simultaneously during frying, which helps to understand the mechanism of oil absorption in fried food. Researchers have discovered that prolonged heating of oils results in polar compounds such as polymers, dimers, free fatty acids, and acrylamide, which can alter metabolism and cause cancer. To reduce the oil content in fried food, innovative frying methods have been developed without compromising its quality which also has improved their effect on human health, product quality, and energy efficiency. The aim is to replace the conventional frying process with novel frying methods that offer fried food-like properties, higher nutritional value, and ease of use by replacing the conventional frying process. In the future, it might be possible to optimize frying technologies to substantially reduce fried foods' oil content. This review focuses on a detailed understanding of different frying techniques and attempts to focus on innovative frying techniques such as vacuum frying, microwave cooking, and hot-air frying that have shown a better potential to be used as an alternative to traditional frying.

Physicochemical Quality Retention during Cold Storage of Prepackaged Barramundi Meat Processed with a New Microwave-Assisted Induction Heating Technology

Microwave-assisted induction heating (MAIH) is a composite microwave and induction heating to supply rapid and uniform heating of food. A recent study showed that the optimum MAIH heating condition for barramundi meat was 90 °C/110 s or 70 °C/130 s. This study examines whether the microwave-assisted induction heating (MAIH) technology (at 70 °C for 130 s or 90 °C for 110 s) can more effectively slow down the quality loss of barramundi meat during cold storage than the traditional boiling method (at 90 °C for 150 s). The results show that no microbial growth was observed in the three groups of heated barramundi meat samples during the 60 days of cold storage. However, the MAIH technology slowed down the increase in the total volatile basic nitrogen (TVBN) content more significantly than the boiling method. As the cold storage time increased, though, the L* (lightness), a* (redness), and W (whiteness) values decreased, while the b* (yellowness) and color difference (ΔE) values increased in the three treatment groups. However, the MAIH technology slowed down the decrease in the L*, a*, and W values more significantly, and produced a ΔE value smaller than the boiling method. Moreover, the MAIH technology ensured higher hardness and chewiness of the barramundi meat than the boiling method. Overall, the MAIH technology slowed down the quality loss of the barramundi meat and maintained better color and texture during cold storage.

Synergistic effects of 915 MHz microwave heating and essential oils on inactivation of foodborne pathogen in hot-chili sauce

Essential oil is a food additive with antimicrobial properties but with limitations due to strong organoleptic properties. However, thermal treatments can be applied to reduce essential oil content while ensuring antimicrobial activities in food matrices. In this study, the inactivation efficiency of essential oils on E. coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in buffered peptone water (BPW) and hot-chili sauce was evaluated when coupled with 915 MHz microwave heating. Essential oils used in this study did not affect the dielectric properties and further heating rate of BPW and hot-chili sauce. The dielectric constant of BPW was 76.3 and dielectric loss factor was 30.9. In addition, it took 85 s to reach 100 °C for all samples. Among essential oils, synergistic microbial inactivation with microwave heating was observed from carvacrol (CL) and citral (CI), but not from eugenol (EU) and Carvone (CN). Specifically, CL and microwave heating (M) for 45 s showed the most effective inactivation (ca. 6 log reduction) for the pathogens in BPW. Similar trends were shown in hot-chili sauce. However, M + CI inactivation did not show synergistic effects in hot-chili sauce. Microwave heating time for hot-chilis sauce was 40 s. In propidium iodide uptake study, M + CL was found to cause most severe damage to cell membrane (758.5 of PI value for E. coli O157:H7) while M + CU and M + CN had little impact. In DiBAC₄(3) test, CL resulted in the largest value (2.09 for E. coli O157:H7). These observations highlight that CL induces synergistic effects as it caused severe membrane damage along with destruction of membrane potential. The combined treatment did not show any significant difference in quality change compared to untreated hot-chili sauce (p > 0.05). The result indicates the potential application of CL and M combination for hot-chili sauce processes to ensure microbiological safety with acceptable quality.

Preserving Ready-to-Eat Meals Using Microwave Technologies for Future Space Programs

The crewed suborbital and space flights launched by private companies over the past three years have rejuvenated public interest in space travel, including space tourism. Ready-to-eat meals (MREs) are the main source of nutrients and energy for space travelers. It is critical that those meals are free of bacterial and viral pathogens and have adequate shelf life. The participation of private companies in space programs will create new opportunities and demand for high-quality and microbiologically safe MREs for future space travels. In this article, we provide a brief review of nutrition and energy requirements for human activities in space. We discuss the general thermal processing requirements for control of bacterial and viral pathogens in MREs and introduce advanced thermal preservation technologies based on microwaves for production of MREs with different shelf-lives under various storage conditions. We also present the latest advancements in the development of polymer packaging materials for quality preservation of thermally stabilized MREs over extended storage. Finally, we recommend future research on issues related to the sensory quality of specially formulated MREs, microbial safety of dried foods that complement high moisture MREs, and food package waste management in future space missions.

Continuous-Flow Microwave Milk Sterilisation System Based on a Coaxial Slot Radiator

Microwave continuous-flow liquid food sterilisation, in which the liquid is mainly heated by microwaves, has the advantages of fast sterilisation speed, energy saving, comprehensive elimination, and less nutrient loss. Circular pipes are commonly used in microwave continuous-flow liquid heating processing. However, with circular pipes, which are widely used in the industry, the heating is uneven owing to the phenomenon of tube focusing when adopting external radiation. In this study, a novel microwave continuous-flow milk sterilisation system based on a coaxial slot radiator is proposed. First, the coaxial slot radiator was designed to realise efficient radiation through the establishment of multi-physics model. The structure of the system was then optimised by comparing the heating efficiency and uniformity of simulation results. The effect of microwave coaxial slot radiator rotation on heating uniformity was simulated and the results show that the heating uniformity is improved obviously. Experimental equipment was set up to verify the results of the simulation. The experimental results are consistent with the simulation results. Finally, the sensitivity analysis of the system is performed to confirm that, when the dielectric properties and types of liquid food change, the heating of the proposed microwave continuous-flow system remains efficient and uniform.

Recent Insights on the Role of Various Food Processing Operations Towards the Development of Sustainable Food Systems

Chronic hunger and malnutrition will eventually result from the population's rapid growth. It is unlikely to succeed in tackling the rising challenges of delivering sustainable food for all people unless high attention is paid on the function of food processing to ensure the supply of stable food. It is impossible to overstate the importance of developing food processing and preservation technologies that can reduce food losses and wastage during surplus seasons. Therefore, sustainable food systems must be developed to provide healthy diets without damaging our world and its resources. The goal is to use various perspectives to confirm why food processing is crucial to future food supply. It is important to show the appropriate utilization of sustainability factors and effect assessments to construct for feeding the globe while staying within planetary limits. There has never been a better time to assure a plentiful food supply to feed the people than right now, when the population is expanding at a worrying rate. The sustainable food project seeks to move the food systems in a long-term, more equitable direction. Food processing, or the conversion of raw materials into functional, edible, and consumer acceptable food, is a critical link in the food value chain between consumption and production. This review looked at various existing and emerging food processing followed by preservation techniques. Food systems must also attempt to reduce food waste and losses, as well as the current and future impacts on the environment and society, to be sustainable.

Continuous flow microwave heating and sterilization for liquid food

Continuous flow microwave sterilization for liquid food has advantages of a short time and high retention rate of nutrients. However, uneven microwave heating is the critical factor restricting the industrialization of microwave sterilization. This paper reviews the up-to-date research on the continuous flow microwave heating and the continuous flow microwave sterilization system for liquid food. The causes of the non-uniformity of continuous flow microwave heating are thoroughly discussed and the methods of improving the uniformity are proposed. Finally, the recommendations for future research of continuous flow microwave sterilization for liquid food are presented.

Design of a simple radio frequency circuit for implementing the open-ended coaxial probe method for permittivity measurement

The development of electromagnetic (EM)-based therapeutic and diagnostic tools, as well as safety assessment of EM interactions with the human body, requires adequate measurement of the complex permittivity of different biological tissues. Such measurement techniques must be low-cost, readily available, and easy to implement. In this study, a simple circuit with basic radio frequency electronics was used to implement the open-ended coaxial probe method for permittivity measurement, as opposed to the widely used vector network analyzers. The non-ideal behavior of the circuit due to spurious reflections and ohmic losses was accounted for by a scattering matrix (SM) that relates the measured reflection coefficient to the true reflection coefficient at the probe tip. Parameters of SM were obtained using three calibration standards, and the circuit was used to measure the complex permittivity of a standard, tissue-equivalent, American Society of Testing Materials (ASTM) polymer gel. A more intuitive approach to circuit analysis is also introduced. For both methods, the dielectric constant and electrical conductivity of the gel were found to agree with the recommended uncertainties of the ASTM standard and validate the utility of the circuit at the test frequency.

Heat-induced formation of advanced glycation end-products in ground pork as affected by the addition of acetic acid or citric acid and the storage duration prior to the heat treatments

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Organic acids affected advanced glycation end-product (AGE) levels in heated pork.

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Heat-induced AGEs in pork with citric acid (ca 0.5–1%) were reduced by 30–54%.

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Adding acetic acid at the same level led to 14–48% reduction of AGEs.

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The reduction of AGEs corresponded to decreased levels of TBARS and Schiff bases.

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Marinating time (pork & acid) did not affect the acid’s inhibiting effect for AGEs.

The heat-induced (121 °C, 10 or 30 min) formation of two potentially hazardous advanced glycation end-products (AGEs), protein-bound N^ɛ-carboxymethyllysine (CML) and N^ɛ-carboxyethyllysine (CEL), in pork as affected by citric or acetic acid (0.5, 1 g/100 pork) and the storage duration (0 °C, 0 – 8 d) prior to the heating was investigated. A longer storage time of raw pork resulted in higher levels of AGEs produced during the later heating, likely due to the accumulation of some AGE precursors during the storage. Depending on the acid level and heating time, adding acid in pork led to 30 – 54% (citric acid) or 14 – 48% (acetic acid) average reduction of heat-induced production of CML/CEL, which corresponded to the reduction of thiobarbituric acid reactive substances and Schiff bases. The marinating time of raw pork with an acid did not significantly affect (P = 0.959 – 0.998) the acid’s inhibition effect on heat-induced formation of CML/CEL.

Gel performance of surimi induced by various thermal technologies: A review

Heating is a vital step in the gelation of surimi. Conventional water bath heating (WB) has the advantages of easy operation and low equipment requirements. However, the slow heat penetration during WB may lead to poor gel formation or gels prone to deterioration, especially with one-step heating. The two-step WB is time-consuming, and a large amount of water used tends to cause environmental problems. This review focuses on key factors affecting the quality of surimi gels in various heating technologies, such as surimi protein structure, chemical forces, or the activity of endogenous enzymes. In addition, the relationships between these factors and the gel performance of surimi under various heating modes are discussed by analyzing the heating temperature and heating rate. Compared with WB, the gel performance can be improved by controlling the heating conditions of microwave heating and ohmic heating, which are mainly achieved by changing the molecular structure of myofibrillar proteins or the activity of endogenous enzymes in surimi. Nevertheless, the novel thermal technologies still face several limitations and further research is needed to realize large-scale industrial production. This review provides ideas and directions for developing heat-induced surimi products with excellent gel properties.

Impact of different microwave treatments on food texture

Electromagnetic waves are frequently used for food processing with commercial or domestic type microwave ovens at present. Microwaves cause molecular movement by the migration of ionic particles or rotation of dipolar particles. Considering the potential applications of microwave technique in food industry, it is seen that microwaves have many advantages such as saving time, better final product quality (more taste, color, and nutritional value), and rapid heat generation. Although microwave treatment used for food processing with developing technologies have a positive effect in terms of time, energy, or nutrient value, it is also very important to what extent they affect the textural properties of the food that they apply to. For this purpose, in this study, it has been investigated that the effects of commonly used microwave treatments such as drying, heating, baking, cooking, thawing, toasting, blanching, frying, and sterilization on the textural properties of food. In addition, this study has also covered the challenges of microwave treatments and future work. In conclusion, microwave treatments cause energy saving due to a short processing time. Therefore, it can be said that it affects the textural properties positively. However, it is important that the microwave processing conditions used are chosen appropriately for each food material.

Microwave and Roasting Impact on Pumpkin Seed Oil and Its Application in Full-Fat Mayonnaise Formula

In this study, ‘Béjaoui’ Cucurbita maxima seeds variety were exposed to both microwave and roasting prior to oil cold press extraction. In addition, full-fat mayonnaise formula from untreated and treated pumpkin seed oils was prepared and assessed for their physical stabilities and bioactive properties in 28-day storage at 25 ± 1 °C. A mayonnaise sample prepared with unrefined sunflower seed oil served as a control. The results showed that the microwave pretreatment of seeds greatly enhanced the oxidative stability of the pumpkin seed oil, which increased from 3 h 46 min ± 10 min in the untreated sample to 4 h 32 min ± 14 min in the microwave cold press pumpkin seed oil. The sterol content increased from 4735 ± 236.75 mg/kg oil in the untreated cold press pumpkin seed oil to 5989 ± 299.45 mg/kg oil and 7156 ± 357.8 mg/kg in the microwave cold press pumpkin seed oil and the roasted cold press pumpkin seed oil, respectively. The mayonnaise prepared with microwave cold press pumpkin seed oil exhibited the lowest creaming index and was more stable to droplet growth when compared to the other mayonnaise samples. All mayonnaise samples prepared with pumpkin seed oils exhibited higher total phenolic contents and antioxidant activities during storage when compared to the mayonnaise sample prepared with unrefined sunflower seed oil. Among pumpkin seed oil mayonnaise samples, the highest values were, however, observed in the one prepared with microwave cold press pumpkin seed oil. Thanks to its high nutraceuticals, the latter could be confidently regarded as a natural fat substitute for commercial stable vegetable oils mayonnaise type emulsions.

Effect of Hurdle Approaches Using Conventional and Moderate Thermal Processing Technologies for Microbial Inactivation in Fruit and Vegetable Products

Thermal processing of packaged fruit and vegetable products is targeted at eliminating microbial contaminants (related to spoilage or pathogenicity) and extending shelf life using microbial inactivation or/and by reducing enzymatic activity in the food. The conventional process of thermal processing involves sterilization (canning and retorting) and pasteurization. The parameters used to design the thermal processing regime depend on the time (minutes) required to eliminate a known population of bacteria in a given food matrix under specified conditions. However, due to the effect of thermal exposure on the sensitive nutrients such as vitamins or bioactive compounds present in fruits and vegetables, alternative technologies and their combinations are required to minimize nutrient loss. The novel moderate thermal regimes aim to eliminate bacterial contaminants while retaining nutritional quality. This review focuses on the “thermal” processing regimes for fruit and vegetable products, including conventional sterilization and pasteurization as well as mild to moderate thermal techniques such as pressure-assisted thermal sterilization (PATS), microwave-assisted thermal sterilization (MATS) and pulsed electric field (PEF) in combination with thermal treatment as a hurdle approach or a combined regime.

Potential use of microwave technology in dermatology

BACKGROUND

Microwaves are used in medicine for diagnostics, and treatment of cancer. Recently, novel microwave devices (Swift^®, Emblation Ltd, UK and miraDry^®, Miramar Labs Inc., CA) have been cleared by the FDA and Health Canada for various dermatological conditions.

OBJECTIVE AND METHODS

To review the dermatological use of microwave-based treatments (plantar warts, corns, actinic keratosis, dermatophytosis, axillary hyperhidrosis, osmidrosis, and hidradenitis suppurativa). Clinical trials, case reports, or in vitro studies for each condition are summarized.

RESULTS AND CONCLUSION

Microwaves are a promising alternative therapy for cutaneous warts, actinic keratosis, axillary hyperhidrosis, and osmidrosis, with favorable safety profiles. However, patients with hidradenitis suppurativa have had negative clinical outcomes. Limited treatment of corns showed good pain reduction but did not resolve hyperkeratosis. A preliminary in vitro study indicated that microwave treatment inhibits the growth of T. rubrum. We present the first case of toenail onychomycosis successfully treated with microwaves. Despite the advancements in the use of microwaves, the mechanism of action in non-ablative treatment is not well understood; further research is needed. More high-quality randomized clinical trials with larger groups and long follow-up periods are also required to evaluate the clinical benefits and possible adverse effects of microwaves in treating dermatological conditions.

Creating foods for older adults: Emotional responses and liking of microwave-assisted thermal sterilization processed meals

The purpose of this study was to examine emotional and liking responses to foods designed for older adults and made using microwave-assisted thermal sterilization technology (MATS). Six chicken pasta meals (three each with and without herbs) were formulated with three concentrations of salt at 100%, 75%, and 50%. Seventy-six community-dwelling older adults conducted sensory and emotional evaluations. Sensory testing involved measuring liking of various sensory attributes using a 9-point hedonic scale, Just-about-right scales to measure appropriateness of the intensity of the attributes, and check-all-that-apply questions to identify perceived flavor and texture attributes. EsSense25 methodology was used for capturing food-evoked emotional responses. Significant differences existed in all measured sensory attributes and in 14 out of the 25 tested emotions across the six meals. Liking scores for all pastas with herbs and high salt pasta with no herbs were not significantly different for all tested attributes and fell between neither like nor dislike and like slightly on the 9-point hedonic scale. These samples were also associated with positive emotions related to energy and activation. Low-salt pastas with no herbs were consistently the least liked samples and evoked negative emotions. Results show that sodium content can be reduced by up to half when herbs are added to microwave-processed pasta meals without compromising liking. PRACTICAL APPLICATION: Chicken pasta meals manufactured using microwave-assisted thermal sterilization technology are acceptable to community living individuals 60 years and older. Emotional responses to the meal are positive. When formulating these meals, herbs can be added to lower sodium content formulations to improve liking and increase the number of positive emotions associated with the meal. Microwave-assisted thermal sterilization, sodium reduction, emotional responses, consumer liking, older adults.

Conventional and Novel Technologies in the Production of Dairy Bioactive Peptides

Background

In recent years, researchers have focused on functional ingredients, functional foods, and nutraceuticals due to the rapidly increasing interest in bioactive components, especially in bioactive peptides. Dairy proteins are a rich and balanced source of amino acids and their derived bioactive peptides, which possess biological and physiological properties. In the dairy industry, microbial fermentation and enzymatic hydrolysis are promising methods for producing bioactive peptides because of their rapid efficiency, and mild reaction conditions. However, these methods utilize less raw material, take long reaction time, result in low yields, and low activity products when used alone, which pose industry to seek for novel methods as pretreatments to increase the yield of bioactive peptides.

Scope and Approach

This review emphasizes the production of peptides from the dairy proteins and discusses the potential use of novel technologies as pretreatments to conventional methods of bioactive peptides production from dairy proteins, including the mechanisms of novel technologies along with respective examples of use, advantages, limitations, and challenges to each technology.

Key Findings and Conclusion

Noteworthily, hydrolysis of dairy proteins liberate wide-range of peptides that possess remarkable biological functions to maintain human health. Novel technologies in the dairy industry such as ultrasound-assisted processing (UAP), microwave-assisted processing (MAP), and high pressure processing (HPP) are innovative and environmentally friendly. Generally, novel technologies are less effectual compared to conventional methods, therefore used in combination with fermentation and enzymatic hydrolysis, and are promising pretreatments to modify peptides’ profile, improve the yields, and high liberation of bioactive peptides as compared to conventional technologies. UAP is an innovative and most efficient technology as its mechanical effects and cavitation change the protein conformation, increase the biological activities of enzymes, and enhance enzymatic hydrolysis reaction rate.

Polymer Processing under Microwaves

Over the last decades, microwave heating has experienced a great development and reached various domains of application, especially in material processing. In the field of polymers, this unusual source of energy showed important advantages arising from the direct microwave/matter interaction. Indeed, microwave heating allows regio-, chemio-, and stereo-selectivity, faster chemical reactions, and higher yields even in solvent-free processes. Thus, this heating mode provides a good alternative to the conventional heating by reducing time and energy consumption, hence reducing the costs and ecological impact of polymer chemistry and processing. This review states some achievements in the use of microwaves as energy source during the synthesis and transformation of polymers. Both in-solution and free-solvent processes are described at different scales, with comparison between microwave and conventional heating.

Effects of low-temperature microwave treatment of wheat germ

BACKGROUND

Wheat germ has a great potential byproduct in food formulations for its outstanding nutritional value. To allow valorization, there is a need to inactivate endogenous enzymes such as lipases to avoid lipid oxidation. In the present study, the effects of microwaves on enzyme activity, as well as on functional and physical properties of wheat germ, were evaluated. Microwave treatments were performed at 50, 60 and 70 °C for 5-20 min.

RESULTS

Lipase activity was severely affected at 60 and 70 °C in contrast to lipoxygenase. Microwave treatment did not cause changes in germ moisture content or color parameters. No significant changes were observed in equilibrium moisture content when comparing the adsorption and desorption processes of raw and microwave-treated wheat germ. The best model to describe sorption process was the Guggenheim-Anderson-De Boer equation. According to the dielectric properties of raw wheat germ, it could be considered as transparent to energy (ε' < 1.87 and ε'' < 0.35). Thermal analysis of proteins showed a low denaturation degree (below 35% to raw material). In addition, some functional properties were enhanced such as oil retention capacity. Conformational changes as a result of microwave treatment were associated with the slight decline observed on the monolayer moisture content.

CONCLUSION

Microwave treatments of wheat germ at 60 and 70 °C were effective for lipase inactivation. Physical properties did not change drastically after the treatments. Microwave-treated wheat germ could be a good source of high-protein ingredient in food product development. © 2021 Society of Chemical Industry.

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.

Packaging materials and technologies for microwave applications: a review1

Packaging materials for microwave application should be generally designed based on products properties and processing conditions such as microwavability, susceptibility, processing condition, barrier properties, mechanical properties, storage condition, sustainability, convenience, and so on. Ready-to-eat products are packed in materials that can sustain thermal processing in an industrial oven and warming process in a household oven. In this context, high barrier polymers are versatile microwave packaging materials due to the microwave transparency (unlike metalized film) and high barrier. Additionally, microwave packaging materials used for ready-to-cook are intended to facilitate the microwave heating of the products in a domestic oven. The introduction of a functional feather to microwave packaging tends to improve the microwaving efficiency such as susceptor and shielding in the household oven or self-venting microwave packaging to safely release the internal steam. Furthermore, microwave-assisted thermal processing intends to control microbial contamination, requiring materials with adequate stability during processing and storage. The features of these materials are addressed in this review along with details on the basic requirements and advanced technologies for microwave packaging, microwave processing of prepackaged food, and migration testing. The prospects of microwave packaging materials in the near future are also discussed.