Microwave processing: Effects and impacts on food components

The current state of knowledge about thermal processing of edible seeds; a special emphasis on their bioactive constituents and antioxidant activity

Thermal processing can alter the biological activity of seed phytochemicals in various ways, thus improving shelf life, bioavailability, oxidative stability, and oil yield; it can also decrease the content of antinutritional compounds, reduce cytotoxic activity and increase the total phenolic content of the seeds. However, this treatment can also inactivate beneficial compounds, including phenolics. This review describes the effect of different thermal processing methods on the content, activity, and bioavailability of chemical compounds from different edible seeds. The outcome is dependent on the method, temperature, time of processing, and type of seeds. Although thermal processing has many benefits, its precise effect on different species requires further clarification to determine how it influences their phytochemical content and biological activity, and identify the optimal conditions for processing.

Exploring the remarkable effects of microwave treatment on starch modification: From structural evolution to changed physicochemical and digestive properties

As one of the crucial components of the food system, starch can be hydrolyzed into glucose after gastrointestinal digestion, so regulating its digestive properties is vital for maintaining health. Microwaves can promote the rearrangement of intramolecular structure of starch, thus improving its physicochemical properties, enhancing its slowly digestible features, and expanding its scope of application. This review zooms in describing recent research results concerning the effects of microwave treatment on the multi-scale structure and physicochemical properties of starch and summarizing the patterns of these changes. Furthermore, the changes in starch structure, resistant starch content, and glycemic index after digestion are pointed out to gain an insight into the enhancement of starch slowly digestible properties by microwave treatment. The resistance of starch to enzymatic digestion may largely hinge on the specific structures formed during microwave treatment. The multi-level structural evolutions of starch during digestion endow it with the power to resist digestion and lower the glycemic index. The properties of starch dictate its application, and these properties are highly associated with its structure. Consequently, understanding the structural changes of microwave-modified starch helps to prepare modified starch with diversified varieties and functional composites.

Microwave freeze-drying characteristics and crosslinking behavior of wheat starch-laurel acid complex

This article investigates the effect of different microwave powers on the crosslinking behavior and microwave freeze-drying characteristics of wheat starch-lauroyl arginate complex during the microwave freeze-drying process. During microwave freeze-drying, as microwave power increased from 0.1 W/g to 0.9 W/g, the freeze-drying time of WS-LA was reduced by 50 %, while the uniformity of freeze-drying was not affected by its composition. In the research results obtained from DSC, Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), XRD, and SEM analyses, with the microwave power increased from 0.1 W/g to 0.9 W/g, the enthalpy value of the melting peak of the WS-LA (wheat starch-lauric acid) composite decreased from 1.15 J/g to 0.62 J/g. The full width at half maximum (FWHM) value increased from 25.6 to 30.79. The ratio of absorbance at 1022/995 cm-1 increased from 1.0111 to 1.0707. The recrystallization (RC) value decreased from 8.77 % to 0.07 %. Additionally, in the microstructure, the size of WS-LA composite particles decreased accordingly. The above findings indicated that the increase in microwave power during microwave freeze-drying had a negative impact on the formation of the WS-LA complex and the ordering of its structure in the sample.

Effect of microwave energy combined with hot air on the functional properties and antioxidant activity and pasting properties of Samh (Mesembryanthemum forsskalei Hochst) seeds

The study aimed to investigate the effect of microwave heating combined with hot air (70 °C) at different application times (0, 90 &180 s,) on the colour, digestible a soluble protein, functional and pasting properties, antioxidant capacity of Samh seeds (8, 12 & 16 % moisture content). The results indicated that microwave heating caused a significant change in Samh seed's colour and enhanced the protein solubility of the seeds, and the functional properties and viscosities of the Samh seeds. Moreover, the results showed that the moisture content of the Samh seeds and application time significantly impact the seeds' quality parameters. However, the partial least square (PLS) model validated that the microwave treatments of the samh seed with (16 %, 180 s) were treated with microwave energy combined with hot air circulation Accordingly, microwaves may offer the potential of being an effective emerging technology for improving the quality and functional characteristics of Samh seeds.

Review on microwave immobilization of soil heavy metals: Processes and mechanisms

Soil contamination with heavy metals (HMs) is still a global issue. The maintenance of long-term stability of HMs in soil during immobilization remediation is a challenge. Microwave (MW) technology can promote the immobilization of HMs in the form of crystals and minerals, thus enhancing their resistance of corrosion. This review provides a comprehensive introduction to the basics of MW irradiation through 177 papers, and reviews the research progress of MW involvement in the immobilization of soil HMs in 10 years. The effects of MW parameter settings, absorber/fixative types and soil physicochemical properties on immobilized HMs are investigated. The immobilization mechanisms of HMs are discussed, high-temperature physical encapsulation and chemical stabilization are the two basic mechanisms in the immobilization process. MW has a unique heating method to achieve efficient remediation by shortening remediation time, reducing the activation energy of reactions and promoting the transformation of stabilization products. Finally, the current limitations of MW in the remediation of HMs contaminated soils are systematically discussed and the corresponding proposed solutions are presented which may provide directions for further laboratory studies. There are still serious problems in taking the results obtained in the laboratory to the full scale. Thus, process optimization, scale-up, design and demonstration are strongly desired. In summary, this review may help new researchers to seize the research frontier in MW and can serve as a reference for future development of MW technology in soil remediation.

Electromagnetic wave-based technology for ready-to-eat foods preservation: a review of applications, challenges and prospects

In recent years, the ready-to-eat foods market has grown significantly due to its high nutritional value and convenience. However, these foods are also at risk of microbial contamination, which poses food safety hazards. Additionally, traditional high-temperature sterilization methods can cause food safety and nutritional health problems such as protein denaturation and lipid oxidation. Therefore, exploring and developing effective sterilization technologies is imperative to ensure food safety and nutritional properties, and protect consumers from potential foodborne diseases. This paper focuses on electromagnetic wave-based pasteurization technologies, including thermal processing technologies such as microwave, radio frequency, and infrared, as well as non-thermal processing technologies like ultraviolet, irradiation, pulsed light, and photodynamic inactivation. Furthermore, it also reviews the antibacterial mechanisms, advantages, disadvantages, and recent applications of these technologies in ready-to-eat foods, and summarizes their limitations and prospects. By comparing the limitations of traditional high-temperature sterilization methods, this paper highlights the significant advantages of these pasteurization techniques in effectively inhibiting microbial growth, slowing lipid oxidation, and preserving food nutrition and flavor. This review may contribute to the industrial application and process optimization of these pasteurization technologies, providing an optimal choice for preserving various types of ready-to-eat foods.

Application of radio frequency energy in processing of fruit and vegetable products

Thermal processing is commonly employed to ensure the quality and extend the shelf-life of fruits and vegetables. Radio frequency (RF) heating has been used as a promising alternative treatment to replace conventional thermal processing methods with advantages of rapid, volumetric, and deep penetration heating characteristics. This article provides comprehensive information regarding RF heating uniformity and applications in processing of fruit and vegetable products, including disinfestation, blanching, drying, and pasteurization. The dielectric properties of fruits and vegetables and their products have also been summarized. In addition, recommendations for future research on RF heating are proposed to enhance practical applications for fruits and vegetables processing in future.

Effect of microwave-assisted treatment on proximate, techno-functional, thermal, structural, and storage properties of TGN (Cyperus esculentus L.) flour

BACKGROUND

The use of the emerging technique of microwave-assisted roasting on TGN (TGN) flour was investigated. Tiger nuts were subjected to microwave irradiation at 450, 600, and 900 W each at 5, 10, and 15 min, and milled to flour. The flours were analyzed for proximate, bioactive, techno-functional, morphological, thermal, and storage effects on their composition. An untreated sample was the control.

RESULTS

The results revealed that microwave treatment significantly (P < 0.05) elicited various modifications in the proximate composition and techno-functional properties. The treatment improved the bioactive composition of phenolic content together with the antioxidant activity of the flour. Progressive microwave treatment of TGNs resulted in flours with darker colors and reduced pasting parameters. Structural modification of starch granules, protein denaturation, and starch-protein complexes occasioned by microwave treatment were evidenced in the functional group analysis, including morphological agglomeration, increased particle size, and thermal properties. Treatment also enhanced the microbiological qualities of flour after 8 weeks of storage.

CONCLUSION

This study shows that microwave treatment produces excellent physical modifications that lead to improvements in the nutritional, functional, sensory, and color properties, and safety attributes of TGN flour for food application. This is a development that could present opportunities for novel food formulation by the food industry and related industries. © 2024 Society of Chemical Industry.

Novel strategies for enhancing quality stability of edible flower during processing using efficient physical fields: A review

Edible flowers are an exotic part of the human diet due to their distinct sensorial properties and health benefits. Due to consumers demand edible flowers and their products with natural freshness and high nutritional value, there is increasing research on the application of green and efficient edible flower processing technologies. This paper reviews the application of a number of physical fields including ultrasound, microwave, infrared, ultraviolet, ionizing radiation, pulse electric field, high hydrostatic pressure, and reduced pressure aiming to improve the processing and product quality of edible flowers. The mechanism of action, influencing factors, and status on application of each physical energy field are critically evaluated. In addition, the advantages and disadvantages of each of these energy fields are evaluated, and trends on their future prospects are highlighted. Future research is expected to focus on gaining greater understanding of the mechanism action of physical field-based technologies when applied to processing of edible flowers and to provide the basis for broaden the application of physical field-based technologies in industrial realm.

Microwave irradiation of guar seed flour: Effect on anti-nutritional factors, phytochemicals, in vitro protein digestibility, thermo-pasting, structural, and functional attributes

Guar seed flour (GSF) has a high amount of carbohydrates, proteins, phytochemicals, and anti-nutritional factors (ANFs), which limits its use. To address this issue, the current study was undertaken to understand the effect of microwave (MW) irradiation on ANFs, phytochemicals, in vitro protein digestibility (IVPD), and functional attributes of GSF at varying power density (Pd: 1-3 W/g) and duration (3-9 min). The ANFs were determined using a colorimetric assay and a Fourier transform infrared spectrum. At 3 Pd-9 min, the maximum reduction in ANFs (tannin, phytic acid, saponin, and trypsin inhibitor activity) was observed. Higher Pd and treatment duration increased antioxidant activity and total phenolic content, except for total flavonoid content. Furthermore, compared to the control sample (78.38%), the IVPD of the GSF samples increased to 3.28% (3 Pd-9 min). An increase in Pd and duration of MW treatment improved the thermal and pasting properties of GSF samples up to 2 Pd-9 min. Due to inter- and intramolecular hydrogen bonding degradation, the relative crystallinity of the 3 Pd-9 min treated GSF sample was 30.58%, which was lower than that of the control (40.08%). In MW-treated samples, SEM images revealed smaller clusters with rough and porous structures. However, no noticeable color (ΔE) changes were observed in MW-treated samples. Aside from water absorption capacity and water solubility index, MW treatment reduced oil absorption capacity, foaming capacity, and emulsifying capacity. As demonstrated by principal component analysis, MW irradiation with moderate Pd (2-3) was more effective in reducing ANFs, retaining nutritional contents, and improving the digestible properties of GSF, which could be a potential ingredient for developing gluten-free products.

Solid-State Microwave Drying for Medical Cannabis Inflorescences: A Rapid and Controlled Alternative to Traditional Drying

Introduction: As the medical use of Cannabis is evolving there is a greater demand for high-quality products for patients. One of the main steps in the manufacturing process of medical Cannabis is drying. Most current drying methods in the Cannabis industry are relatively slow and inefficient processes. Materials and Methods: This article presents a drying method based on solid-state microwave (MW) that provides fast and uniform drying, and examines its efficiency for drying Cannabis inflorescences compared with the traditional drying method. We assessed 67 cannabinoids and 36 terpenoids in the plant in a range of drying temperatures (40°C, 50°C, 60°C, and 80°C). The identification and quantification of these secondary metabolites were done by chromatography methods. Results: This method resulted in a considerable reduction of drying time, from several days to a few hours. The multiple frequency-phase combination states of the system allowed control and prediction of moisture levels during drying, thus preventing overdrying. A drying temperature of 50°C provided the most effective results in terms of both short drying time and preservation of the composition of the secondary metabolites compared with traditional drying. At 50°C, the chemical profile of phytocannabinoids and terpenoids was best kept to that of the original plant before drying, suggesting less degradation by chemical reactions such as decarboxylation. The fast-drying time also reduced the susceptibility of the plant to microbial contamination. Conclusion: Our results support solid-state MW drying as an effective postharvest step to quickly dry the plant material for improved downstream processing with a minimal negative impact on product quality.

Insights into application progress of seafood processing technologies and their implications on flavor: a review

Seafood tends to be highly vulnerable to spoilage and deterioration due to biochemical reactions and microbial contaminations, which requires appropriate processing technologies to improve or maintain its quality. Flavor, as an indispensable aspect reflecting the quality profile of seafood and influencing the final choice of consumers, is closely related to the processing technologies adopted. This review gives updated information on traditional and emerging processing technologies used in seafood processing and their implications on flavor. Traditional processing technologies, especially thermal treatment, effectively deactivate microorganisms to enhance seafood safety and prolong its shelf life. Nonetheless, these methods come with limitations, including reduced processing efficiency, increased energy consumption, and alterations in flavor, color, and texture due to overheating. Emerging processing technologies like microwave heating, infrared heating, high pressure processing, cold plasma, pulsed electric field, and ultrasound show alternative effects to traditional technologies. In addition to deactivating microorganisms and extending shelf life, these technologies can also safeguard the sensory quality of seafood. This review discusses emerging processing technologies in seafood and covers their principles, applications, developments, advantages, and limitations. In addition, this review examines the potential synergies that can arise from combining certain processing technologies in seafood processing.

A review of natural plant extracts in beverages: Extraction process, nutritional function, and safety evaluation

The demand for foods and beverages with therapeutic and functional features has increased as a result of rising consumer awareness of health and wellness. In natural, plants are abundant, widespread, and inexpensive, in addition to being rich in bioactive components that are beneficial to health. The bioactive substances contained in plants include polyphenols, polysaccharides, flavonoids, aromatics, aliphatics, terpenoids, etc., which have rich active functions and application potential for plant-based beverages. In this review, various existing extraction processes and their advantages and disadvantages are introduced. The antioxidant, anti-inflammatory, intestinal flora regulation, metabolism regulation, and nerve protection effects of plant beverages are described. The biotoxicity and sensory properties of plant-based beverages are also summarized. With the diversification of the food industry and commerce, plant-based beverages may become a promising new category of health functional foods in our daily lives.

Microwave-assisted extraction in closed vessel in food analysis

Microwave-assisted extraction (MAE) is an important technique in analytical chemistry. It offers several advantages over traditional extraction methods, such as improved extraction efficiency, shorter extraction times, reduced solvent consumption, and enhanced analyte recovery. Using microwaves, heat is directly applied to the sample, leading to rapid and efficient extraction of target compounds by enhancing the solubility and diffusion of the target compounds, thus requiring lower solvent volume. Therefore, MAE can be considered a more environmentally friendly and cost-effective option facilitating the transition toward greener and more sustainable analytical chemistry workflows. This contribution systematically reviews the application of MAE to a selection of target compounds/compounds classes of relevance for food quality and safety assessment. As inclusion criteria, MAE active temperature control and molecularly-resolved characterization of the extracts were considered. Contents include a brief introduction of the principles of operation, available systems characteristics, and key parameters influencing extraction efficiency and selectivity. The application section covers functional food components (e.g., phenols, diterpenes, and carotenoids), lipids, contaminants (e.g., polycyclic aromatic hydrocarbons and mineral oil hydrocarbons), pesticides, veterinary drug residues, and a selection of process contaminants and xenobiotics of relevance for food safety.

Legume protein/polysaccharide food hydrogels: Preparation methods, improvement strategies and applications

For the development of innovative foods and nutritional fortification, research into food gel is essential. As two types of rich natural gel material, both legume proteins and polysaccharides have high nutritional value and excellent application potential, attracting wide attention worldwide. Research has focused on combining legume proteins with polysaccharides to form hybrid hydrogels as their combinations show improved texture and water retention compared to single legume protein or single polysaccharide gels, and these properties can be tailored for specific applications. This article reviews hydrogels of common legume proteins and discusses heat induction, pH induction, salt ion induction, and enzyme-induced assembly of legume protein/polysaccharide mixtures. The applications of these hydrogels in fat replacement, satiety enhancement, and delivery of bioactive ingredients are discussed. Challenges for future work are also highlighted.

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.

Recent and novel processing technologies coupled with enzymatic hydrolysis to enhance the production of antioxidant peptides from food proteins: A review

Antioxidant peptides obtained through enzymatic hydrolysis of food proteins exhibit a broad range of bioactivities both in vitro and in vivo models. The antioxidant peptides showed the potential to fight against the reactive oxygen species, free radicals and other pro-oxidative substances which are considered the source of various chronic diseases for humans. Both animals and plants have been recognized as natural protein sources and attracted much research interest over the synthetic ones in terms of safety. However, the main challenge remains to increase the antioxidant peptides yield, reduce the enzyme quantity and the reaction time. Consequently, different efficient and innovative food processing technologies such as thermal, ultrasound, microwave, high hydrostatic pressure, pulsed electric field, etc. have been developed and currently used to treat food proteins before (pretreatment) or during the enzymatic hydrolysis (assisted). Those technologies were found to significantly enhance the degree of hydrolysis and the production of substantial antioxidant peptides. These emerging technologies enhance the enzymatic hydrolysis by inducing protein denaturation/unfolding, and the enzymatic activation without altering their functional and nutritional properties. This review discusses the state of the art of thermal, ultrasound, high hydrostatic pressure, microwave, and pulsed electric field techniques, their applications while coupled with enzymatic hydrolysis, their comparison and potential challenges for the production of antioxidant peptides from food proteins.

Application of microwave treatment for reduction of microbial load in jaggery cubes

In present study, fresh jaggery cubes were used and treated with microwave heating. Two treatment time has been selected to treat the jaggery such as 30 s and 45 s. Physiochemical and microbial parameters were analysed before and after treatment of microwave. Moisture content of treated jaggery sample was 3.98 ± 0.59 and 3.86 ± 0.63 for 30 s and 45 s microwave treatment respectively. Similarly, this treatment maintains the water activity at 0.6, which is considered as a safe for consumption. The content of iron retains in this microwave treatment; it doesn't affect much on the iron content present in fresh Jaggery sample. Most substantial result has been observed in case of total plate count and yeast and mold count when treated with microwave heating. In this case microwave process at 45 s was found to be the best since it reduced the total plate count (TPC) load to 13 ± 4 from 194 ± 48 cfu/g. Also, in case on yeast and mold count, 45 s microwave treatment showed reduction of load to 28 ± 7 cfu/g from 25,498 ± 2809 cfu/g. Present investigation showed that microwave treatment for 45 s was found to be the best to treat the jaggery.

The Use of Ozone Technology to Control Microorganism Growth, Enhance Food Safety and Extend Shelf Life: A Promising Food Decontamination Technology

The need for microorganism control in the food industry has promoted research in food processing technologies. Ozone is considered to be a promising food preserving technique and has gained great interest due to its strong oxidative properties and significant antimicrobial efficiency, and because its decomposition leaves no residues in foods. In this ozone technology review, the properties and the oxidation potential of ozone, and the intrinsic and extrinsic factors that affect the microorganism inactivation efficiency of both gaseous and aqueous ozone, are explained, as well as the mechanisms of ozone inactivation of foodborne pathogenic bacteria, fungi, mould, and biofilms. This review focuses on the latest scientific studies on the effects of ozone in controlling microorganism growth, maintaining food appearance and sensorial organoleptic qualities, assuring nutrient contents, enhancing the quality of food, and extending food shelf life, e.g., vegetables, fruits, meat, and grain products. The multifunctionality effects of ozone in food processing, in both gaseous and aqueous form, have promoted its use in the food industries to meet the increased consumer preference for a healthy diet and ready-to-eat products, although ozone may present undesirable effects on physicochemical characteristics on certain food products at high concentrations. The combined uses of ozone and other techniques (hurdle technology) have shown a promotive future in food processing. It can be concluded from this review that the application of ozone technology upon food requires increased research; specifically, the use of treatment conditions such as concentration and humidity for food and surface decontamination.

Cooking at home to retain nutritional quality and minimise nutrient losses: A focus on vegetables, potatoes and pulses

Cooking at home has experienced a decline in many countries since the mid-20th century. As rates of obesity have increased, there has been an emphasis on more frequent home cooking, including its incorporation into several food-based dietary guidelines around the world as a strategy to improve dietary quality. With the recent trend towards the adoption of diets richer in plant-based foods, many consumers cooking at home may now be cooking plant foods such as vegetables, potatoes and pulses more often. It is, therefore, timely to explore the impact that different home cooking methods have on the range of nutrients (e.g. vitamin C and folate) and bioactive phytochemicals (e.g. carotenoids and polyphenols) that such plant foods provide, and this paper will explore this and whether advice can be tailored to minimise such losses. The impact of cooking on nutritional quality can be both desirable and/or undesirable and can vary according to the cooking method and the nutrient or phytochemical of interest. Cooking methods that expose plant foods to high temperatures and/or water for long periods of time (e.g. boiling) may be the most detrimental to nutrient content, whereas other cooking methods such as steaming or microwaving may help to retain nutrients, particularly those that are water-soluble. Dishes that use cooking liquids may retain nutrients that would have been lost through leaching. It may be helpful to provide the public with more information about better methods to prepare and cook plant foods to minimise any nutrient losses. However, for some nutrients/phytochemicals the insufficient and inconsistent research findings make clear messages around the optimal cooking method difficult, and factors such as bioaccessibility rather than just quantity may also be important to consider.

Food preservation by cold plasma from dielectric barrier discharges in agri-food industries

BACKGROUND

Cold plasma (CP) can be defined as partially or wholly ionized gas carrying myriads of highly reactive products, such as electrons, negative ions, positive ions, free radicals, excited or non-excited atoms, and photons at ambient temperature. It is generated at 30-60°C under atmospheric or reduced pressure (vacuum). In contrast to thermal plasma, it requires less power, exhibits electron temperatures much higher than the corresponding gas (macroscopic temperature), and does not present a local thermodynamic equilibrium. Dielectric barrier discharges (DBD) are one of the most convenient and efficient methods to produce CP.

SCOPE AND APPROACH

Cold plasma technology has the potential to replace traditional agri-food processing purification methods because of its low energy requirements and flexible system design. CP technology works by reducing bacteria levels and removing pests and mycotoxins from your produce at harvest. It can also catalyze physiological and biochemical reactions and modify materials. It can meet microbial food safety standards, improve the physical, nutritional, and sensory characteristics of the products, preserve unstable bioactive compounds, and modulate enzyme activities. This manuscript also discusses the quality characteristics of food components before/after CP treatment.

KEY FINDINGS AND CONCLUSION

In the past decade, CP treatments of food products have experienced increased popularity due to their potential contributions to non-thermal food processing. There is no doubt that CP treatment is a flexible approach with demonstrated efficacy for controlling many risks across food and agricultural sustainability sectors. In addition, CP technologies also can be applied in food-related areas, including modification of chemical structures and desensitization treatments. There is a need to fully assess the benefits and risks of stand-alone CP unit processes or their integration as a processing chain as soon as the economic, ecological, and consumer benefits and acceptability are considered.

Impact of Thermal Processing on the Composition of Secondary Metabolites of Ginger Rhizome-A Review

Ginger (Zingiber officinale Rosc.) is both a commonly used spice, and an ingredient of various dietary supplements and medications. Its diverse applications result from the range of health benefits that this plant brings thanks to the presence of active compounds (secondary metabolites) in the matrix. Even if several studies underline a stronger pharmacological activity of fresh ginger rhizomes, the unprocessed plant is relatively rarely used. Ginger rhizomes are subjected to thermal processing, such as boiling, blanching, steam drying and others, at different temperature and time settings. Additionally, freeze-drying of the rhizomes is used as the first step in the preparation of raw material. It was proved that the composition of secondary metabolites of the Zingiber officinale rhizome changes upon the influence of temperature. Therefore, the aim of the review was to put together scientific results on the impact of traditional and unconventional methods of heat treatment on ginger rhizomes and to show the compositional differences that they induce in the plant matrix. Variations in the content and the transformation of some compounds into other metabolites will be also discussed, with particular attention paid to two major groups of secondary metabolites present in the plant, namely, phenolics and terpenes.

Effects of Reheating Methods on Rheological and Textural Characteristics of Rice Starch with Different Gelatinization Degrees

Pregelatinized starch (PGS) is often used to improve the processing quality of foodstuffs, but little attention has been paid to the effects of different reheating methods and degree of starch gelatinization (DSG) on their rheological and textural properties. In this study, pregelatinized rice starches (RS) with gelatinization degrees ranging from 58% to 100% were prepared via different Rapid Visco Analyser (RVA) heating procedures and reheated in various methods, including high-power microwave (HM), low-power microwave (LM), and water bath. The rheological behavior and textural properties were explored, and the results demonstrated that the consistency, gel strength, hardness, and springiness of PGS in all tested samples decreased significantly after reheating. The storage modulus (G') of PGS increased dramatically while the thermal stability decreased. Interestingly, the reheating methods possessed various effects on the starch of different DSG.

Physical, Chemical and Biochemical Modification Approaches of Potato (Peel) Constituents for Bio-Based Food Packaging Concepts: A Review

Potatoes are grown in large quantities and are mainly used as food or animal feed. Potato processing generates a large amount of side streams, which are currently low value by-products of the potato processing industry. The utilization of the potato peel side stream and other potato residues is also becoming increasingly important from a sustainability point of view. Individual constituents of potato peel or complete potato tubers can for instance be used for application in other products such as bio-based food packaging. Prior using constituents for specific applications, their properties and characteristics need to be known and understood. This article extensively reviews the scientific literature about physical, chemical, and biochemical modification of potato constituents. Besides short explanations about the modification techniques, extensive summaries of the results from scientific articles are outlined focusing on the main constituents of potatoes, namely potato starch and potato protein. The effects of the different modification techniques are qualitatively interpreted in tables to obtain a condensed overview about the influence of different modification techniques on the potato constituents. Overall, this article provides an up-to-date and comprehensive overview of the possibilities and implications of modifying potato components for potential further valorization in, e.g., bio-based food packaging.

Identification of Fibre Content in Edible Flours Using Microwave Dielectric Cell: Concise Review and Experimental Insights

The quality of edible intake decides the health of the human body and is also responsible for building a healthy immune system in the body. A healthy immune system can protect the body even from invisible attacks of viral or bacterial infections. The assessment of the quality of edible items is not well defined and standardized in many developing countries due to quality assessment difficulties in practice. An alternative well-defined quality assessment approach for edible flours is presented in this paper. Every edible substance has dielectric properties, and it varies from material to material in nature. Edible flours and liquid have different microwave absorption capabilities, based on their natural molecular structure. Based on the microwave energy absorption characteristics of materials, the attenuation constant of edible flours is derived by the waveguide method in this work. In this approach, microwave energy absorption of the edible samples of different types of wheat, rice and millets are observed, and the attenuation constant factors of the samples are then calculated from the tabulated values. The work focuses on the identification of fibre content present in the edible flours. Inferences are made based on the attenuation and its variations with the number of samples, dielectric loss and dielectric constant of the samples. A systematic and concise review of the topic is also included for the benefit of future researchers.

Gel Property of Soy Protein Emulsion Gel: Impact of Combined Microwave Pretreatment and Covalent Binding of Polyphenols by Alkaline Method

This study investigated the effects of microwave modification, alkali polyphenol (ferulic acid) covalently combined modification, and microwave-alkali polyphenol covalently combined modification on the gel properties of soy protein emulsions. The results showed that the properties of soy protein emulsions were improved significantly by the three modification methods. After three kinds of modification, the viscoelasticity of soy protein emulsion gel increased, and a gel system with stronger elasticity was formed. The texture, water-holding, and hydration properties of the emulsion gel increased significantly. The SEM and ClSM results showed that the modified soy protein emulsion gel had a more compact and uniform porous structure, and the oil droplets could be better embedded in the network structure of the gel. Among the three modification methods, the microwave-alkali method polyphenol covalently combining the compound modification effect was best, and the microwave modification effect was least effective compared to the other two methods. Our obtained results suggested that for gel property modification of soy protein emulsion gels, microwave pretreatment combined with the covalent binding of polyphenols by an alkaline method is an effective method.

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.

Decontamination technologies for medicinal and aromatic plants: A review

Microbial quality assurance has always been an important subject in the production, trade, and consumption of medicinal and aromatic plants (MAPs). Most MAPs have therapeutic and nutritional properties due to the presence of active substances such as essential oils, flavonoids, alkaloids, etc. However, MAPs can become infected with microorganisms due to poor hygienic conditions during cultivation and postharvest processes. This problem reduces the shelf life and effective ingredients of the product. To overcome these problems, several technologies such as using ethylene oxide gas, gamma irradiation, and steam heating have been used. However, these technologies have disadvantages such as the formation of toxic by-products, low consumer acceptance, or may have a negative effect on the quality of MAPs. This requires a need for novel decontamination technology which can effectively reduce the biological contamination and minimize the food quality losses. In recent years, new technologies such as ozonation, cold plasma, ultraviolet, infrared, microwave, radiofrequency and combination of these technologies have been developed. In this review, biological contamination of MAPs and technologies used for their decontamination were studied. Also, the mechanism of inactivation of microorganisms and the efficacy of decontamination techniques on the qualitative and microbial characteristics of MAPs were investigated.

Microwave Cooking Enriches the Nanoscale and Short/Long-Range Orders of the Resulting indica Rice Starch Undergoing Storage

The chain reorganization of cooked starch during storage plays an important role in the performance of starchy products such as rice foods. Here, different analytical techniques (such as small-angle X-ray scattering) were used to reveal how microwave cooking influences the chain assembly of cooked indica rice starch undergoing storage for 0, 24, or 48 h. While stored, more short-range double helices, long-range crystallites, and nanoscale orders emerged for the microwave-cooked starch than for its conventionally cooked counterpart. For instance, after storage for 24 h, the microwave-cooked starch contained 46.8% of double helices, while its conventionally cooked counterpart possessed 34.3% of double helices. This could be related to the fact that the microwave field caused high-frequency movements of polar groups such as hydroxyls, which strengthened the interactions between starch chains and water molecules and eventually their assembly into double helices, crystallites, and nanoscale orders. This work provides further insights into the chain reassembly of microwave-cooked starch undergoing storage, which is closely related to the quality attributes of starch-based products.

Application of protein-polysaccharide Maillard conjugates as emulsifiers: Source, preparation and functional properties

The protein-polysaccharide conjugates formed by Maillard reaction can be used as novel emulsifiers in the food industry. Proteins and polysaccharides have extensive sources, and their emulsifying properties are highly dependent on their structural features. The Maillard conjugates can be prepared from conventional and novel methods, and these methods have different advantages and limitations in industrial applications. After an appropriate glycation, the conjugates show some modified or enhanced functional properties, including solubility, emulsifying property, thermal stability, foaming capacity, and gelation property. However, the research on the structure-function relationship of both proteins and polysaccharides is limited. It is necessary to well understand the characteristics of these biopolymers, and select appropriate conditions to control the process of Maillard reaction. Overall, the Maillard conjugates show great potential as the emulsifiers and stabilizers in the emulsion system. This review introduces the sources and structural characteristics of commonly used proteins and polysaccharides for Maillard reaction, outlines the methods (dry-heating, wet-heating, electrospinning, ultrasound, pulsed electric field, and microwave) for preparing Maillard conjugates and focuses on the improved functional properties (solubility, emulsifying, foaming and thermal properties) and the potential mechanisms.

Influence of fat content and water activity on the heating pattern of model systems submitted to microwave heating

This research analyzed the influence of fat content (1%, 3%, 5%, and 10%, w.b.) and of water activity (0.85, 0.90, 0.95, and 0.99) on the effectiveness of microwave heating within model systems (agar gel). Findings indicate that an increased fat content promotes more uniform heating in the model systems and results in longer heating times to reach the target temperature of 50°C. In the model systems with different a_w values, the warming of the central model zone was slower while in the corners, heating was accelerated. Additionally, in these models, heating times increased as the a_w was decreased. PRACTICAL APPLICATION: The study of model systems allows for a detailed assessment of food when subjected to microwaves; and how heating is influenced by food properties such as a_w and fat content. Findings indicate that changes in product formulation could improve the heating of ready-to-eat foods, either by increasing the fat content (better uniformity) or having high a_w (shorter heating time).

Recent developments in radio frequency drying for food and agricultural products using a multi-stage strategy: a review

Radio frequency (RF) drying is an emerging technology for food and agricultural products, holding features of rapid, uniform, stable, and volumetric heating, high energy efficiency, and moisture leveling. However, the RF drying with a single stage commonly has drawbacks of unexpected product quality, non-uniform moisture distribution, and prolonged drying time. The multi-stage drying approach could overcome the shortcomings of one-stage strategy accordingly by applying different drying methods or operating parameter values in each phase separately. This review describes the principle of RF heating, presents the typical systems and superiorities of RF drying, and provides a comprehensive overview on recent development in applications of both the one-stage and the multi-stage RF drying, and analysis of drying characteristics and merits for different types of the two-stage strategy. This review finally proposes recommendations for future studies in improving and optimizing the existing RF drying protocols and scaling up them to industrial applications.

Finite Element Method for Freezing and Thawing Industrial Food Processes

Freezing is a well-established preservation method used to maintain the freshness of perishable food products during storage, transportation and retail distribution; however, food freezing is a complex process involving simultaneous heat and mass transfer and a progression of physical and chemical changes. This could affect the quality of the frozen product and increase the percentage of drip loss (loss in flavor and sensory properties) during thawing. Numerical modeling can be used to monitor and control quality changes during the freezing and thawing processes. This technique provides accurate predictions and visual information that could greatly improve quality control and be used to develop advanced cold storage and transport technologies. Finite element modeling (FEM) has become a widely applied numerical tool in industrial food applications, particularly in freezing and thawing processes. We review the recent studies on applying FEM in the food industry, emphasizing the freezing and thawing processes. Challenges and problems in these two main parts of the food industry are also discussed. To control ice crystallization and avoid cellular structure damage during freezing, including physicochemical and microbiological changes occurring during thawing, both traditional and novel technologies applied to freezing and thawing need to be optimized. Mere experimental designs cannot elucidate the optimum freezing, frozen storage, and thawing conditions. Moreover, these experimental procedures can be expensive and time-consuming. This review demonstrates that the FEM technique helps solve mass and heat transfer equations for any geometry and boundary conditions. This study offers promising insight into the use of FEM for the accurate prediction of key information pertaining to food processes.

Effective pretreatment technologies for fresh foods aimed for use in central kitchen processing

The central kitchen concept is a new trend in the food industry, where centralized preparation and processing of fresh foods and the distribution of finished or semi-finished products to catering chains or related units take place. Fresh foods processed by a central kitchen mainly include fruit and vegetables, meat, aquatic products, and edible fungi; these foods have high water activities and thermal sensitivities and must be processed with care. Appropriate pretreatments are generally required for these food materials; typical pretreatment processes include cleaning, enzyme inactivation, and disinfection, as well as packaging and coating. To improve the working efficiency of a central kitchen, novel efficient pretreatment technologies are needed. This article systematically reviews various high-efficiency pretreatment technologies for fresh foods. These include ultrasonic cleaning technologies, physical-field enzyme inactivation technologies, non-thermal disinfection technologies, and modified-atmosphere packagings and coatings. Mechanisms, applications, influencing factors, and advantages and disadvantages of these technologies, which can be used in a central kitchen, are outlined and discussed. Possible solutions to problems related to central-kitchen food processing are addressed, including low cleaning efficiency and automation feasibility, high nutrition loss, high energy consumption, and short shelf life of products. These should lead us to the next step of fresh food processing for a highly demanding modern society. © 2020 Society of Chemical Industry.

Effects of microwave heat treatment on fungal growth, functional properties, total phenolic content, and antioxidant activity of sorghum (Sorghum bicolor L.) grain

Sorghum grains were subjected to microwave heating at different power levels 350 and 500 W for application times of 15, 30, and 45 s. The effect of microwave heating on fungal growth, protein content, in vitro digestibility, protein solubility, and functional and antioxidant properties of sorghum grain was investigated. The microwave heating at 350 and 500 W significantly reduced fungal incidence in the grain up to 26.2 and 33.4%. No significant changes were found in the crude protein and digestibility of protein, water holding capacity, and oil holding capacity of sorghum. However, application of microwave energy at 500 W for 30 & 45 s caused a sharp reduction on the protein solubility (8.2-7.6%), foaming capacity (6.47-0.98%), emulsion capacity (0.43-0.32 mL/g) and the emulsion stability (2.2-1.6%) of sorghum grain, respectively. Conversely, a significant increment of grain total phenolic content up to 47.1 and 50.8 mg GAE/g and the antioxidant activity up to 40.9 and 59.1% after microwave heat treatment at 350 and 500 W for 45 s, respectively, was observed. These findings revealed that sorghum grain should be treated with microwave at 350 and 500 W for 45 and 15 s, respectively, in order to maintained and enhanced its functional and nutritional properties. Accordingly, microwave heating, particularly at low power, may be an effective emerging method for improving the physicochemical and nutritional properties of sorghum grain.

Monitoring Thermal and Non-Thermal Treatments during Processing of Muscle Foods: A Comprehensive Review of Recent Technological Advances

Muscle food products play a vital role in human nutrition due to their sensory quality and high nutritional value. One well-known challenge of such products is the high perishability and limited shelf life unless suitable preservation or processing techniques are applied. Thermal processing is one of the well-established treatments that has been most commonly used in order to prepare food and ensure its safety. However, the application of inappropriate or severe thermal treatments may lead to undesirable changes in the sensory and nutritional quality of heat-processed products, and especially so for foods that are sensitive to thermal treatments, such as fish and meat and their products. In recent years, novel thermal treatments (e.g., ohmic heating, microwave) and non-thermal processing (e.g., high pressure, cold plasma) have emerged and proved to cause less damage to the quality of treated products than do conventional techniques. Several traditional assessment approaches have been extensively applied in order to evaluate and monitor changes in quality resulting from the use of thermal and non-thermal processing methods. Recent advances, nonetheless, have shown tremendous potential of various emerging analytical methods. Among these, spectroscopic techniques have received considerable attention due to many favorable features compared to conventional analysis methods. This review paper will provide an updated overview of both processing (thermal and non-thermal) and analytical techniques (traditional methods and spectroscopic ones). The opportunities and limitations will be discussed and possible directions for future research studies and applications will be suggested.