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.

Recent developments in applications of physical fields for microbial decontamination and enhancing nutritional properties of germinated edible seeds and sprouts: a review.

Germinated edible seeds and sprouts have attracted consumers because of their nutritional values and health benefits. To ensure the microbial safety of the seed and sprout, emerging processing methods involving physical fields (PFs), having the characteristics of high efficiency and environmental safety, are increasingly proposed as effective decontamination processing technologies. This review summarizes recent progress on the application of PFs to germinating edible seeds, including their impact on microbial decontamination and nutritional quality and the associated influencing mechanisms in germination. The effectiveness, application scope, and limitation of the various physical techniques, including ultrasound, microwave, radio frequency, infrared heating, irradiation, pulsed light, plasma, and high-pressure processing, are symmetrically reviewed. Good application potential for improving seed germination and sprout growth is also described for promoting the accumulation of bioactive compounds in sprouts, and subsequently enhancing the antioxidant capacity under favorable PFs processing conditions. Moreover, the challenges and future directions of PFs in the application to germinated edible seeds are finally proposed. This review also attempts to provide an in-depth understanding of the effects of PFs on microbial safety and changes in nutritional properties of germinating edible seeds and a theoretical reference for the future development of PFs in processing safe sprouted seeds.

Guidelines on reporting treatment conditions for emerging technologies in food processing.

In the last decades, different non-thermal and thermal technologies have been developed for food processing. However, in many cases, it is not clear which experimental parameters must be reported to guarantee the experiments' reproducibility and provide the food industry a straightforward way to scale-up these technologies. Since reproducibility is one of the most important science features, the current work aims to improve the reproducibility of studies on emerging technologies for food processing by providing guidelines on reporting treatment conditions of thermal and non-thermal technologies. Infrared heating, microwave heating, ohmic heating and radiofrequency heating are addressed as advanced thermal technologies and isostatic high pressure, ultra-high-pressure homogenization sterilization, high-pressure homogenization, microfluidization, irradiation, plasma technologies, power ultrasound, pressure change technology, pulsed electric fields, pulsed light and supercritical CO2 are approached as non-thermal technologies. Finally, growing points and perspectives are highlighted.

Inactivation mechanism of slightly acidic electrolyzed water on Bacillus cereus spores.

This study aimed to investigate the inactivation mechanism of Bacillus cereus spores by slightly acidic electrolyzed water (SAEW). Spore inactivation efficacy of SAEW at different available chlorine concentrations (ACC, 20, 60 and 100 mg/L), as well as spore structures change, coat damage, mutagenesis, and inner membrane (IM) properties were examined. The viability of treated spores with lysozyme addition and spore germination induced by germinant was also examined. The results showed that SAEW could reach maximal 5.81 CFU/mL log reduction with ACC of 100 mg/L for 20 min treatment. Scanning and transmission electron photomicrographs indicated that SAEW treatment rendered spore surface ruptured, IM damage and core contents loss. No mutants were generated in survivors of SAEW treated-spores. SAEW significantly weakened spore viability in high salt medium, losing its ability to retain pyridine-2,6-dicarboxylic acid (DPA) at 85 °C. SAEW-treated spores germinated with l-alanine or inosine induction were mostly stained with propidium iodide (PI) but could not recover via lysozyme addition. Furthermore, SAEW treatment inhibited spore germination in the induction of germinant (mixture of l-alanine and inosine or dodecylamine). These findings indicated that SAEW inactivated spore primarily by damaging the spore IM.

A comprehensive review on recent developments of radio frequency treatment for pasteurizing agricultural products.

Recent pathogen incidents have forced food industry to seek for alternative processes in postharvest pasteurization of agricultural commodities. Radio frequency (RF) heating has been used as one alternative treatment to replace chemical fumigation and other conventional thermal methods since it is relatively easy to apply and leaves no chemical residues. RF technology transfers electromagnetic energy into large bulk volume of the products to provide a fast and volumetric heating. There are two types of RF technology commonly applied in lab and industry to generate the heat energy: free running oscillator and 50-Ω systems. Several reviews have been published to introduce the application of RF heating in food processing. However, few reviews have a comprehensive summary of RF treatment for pasteurizing agricultural products. The objective of this review was to introduce the developments in the RF pasteurization of agricultural commodities and to present future directions of the RF heating applications. While the recent developments in the RF pasteurization were presented, thermal death kinetics of targeted pathogens as influenced by water activity, pathogen species and heating rates, non-thermal effects of RF heating, combining RF heating with other technologies for pasteurization, RF heating uniformity improvements using computer simulation and development of practical RF pasteurization processes were also focused. This review is expected to provide a comprehensive understanding of RF pasteurization for agricultural products and promote the industrial-scale applications of RF technology with possible process protocol optimization purposes.

Computational modelling of survival of Aspergillus flavus in peanut kernels during hot air-assisted radio frequency pasteurization.

In recent years, radio frequency (RF) heating is getting popular as an alternative pasteurization method for agricultural commodities and low moisture foods. Computer simulation is an effective way to help understand RF interactions with food components and predict temperature distributions among food samples after RF treatments. In this study, a computer model based on Joule heating and thermal inactivation kinetic of A. flavus was established to predict both temperature distribution and microbial reduction among peanut kernels after RF processing. For the process validation, three 2-g peanut samples inoculated with 40 µL A. flavus were placed at three representative locations among 2.17 kg peanut kernels and subjected to various processing conditions in a 27.12 MHz, 6 kW RF heating unit together with hot air system. Results showed that the average difference of the sample temperature and microbial reduction between simulation and experiment was small with RMSE values of 0.009 °C and 0.012 °C, and 0.31 log CFU/g and 0.42 log CFU/g for peanut moisture contents of 7.56% and 12.02% w. b., respectively. Nonuniform RF heating resulted in the least lethality of A. flavus at the cold spot. The validated computer model was further used to estimate microbial reduction distributions at other target temperatures based on predicted temperature profiles. This computer model may help design the RF pasteurization protocols for peanut kernels without extensive experiments in food industry.

Recent developments in applications of radio frequency heating for improving safety and quality of food grains and their products: A review.

Food grains constitute a vital part of the daily diet of the population worldwide, and are generally considered as safe products with high storage stability due to their low moisture contents. However, post-harvest losses (PHL) caused by insects, fungi, food-borne pathogens, and undesirable enzymes remain a major concern for the grain industry. Thermal treatments are commonly used to reduce the PHL of grains and their products without any chemical residues. Among which, radio frequency (RF) technology has been regarded as a promising alternative to traditional heating methods for improving safety and quality of food grains due to its fast, volumetric, and deep penetration heating characteristics. This review provided comprehensive information about principles of RF technology and its main applications including disinfestation, pasteurization, enzyme inactivation, drying, and roasting for processing food grains and their products. The methods to improve the RF heating uniformity and effects of RF heating on product quality were also reviewed. Finally, the current problems and recommendations for future work related to RF processing of grains and their products were discussed. This review would improve the understanding of RF heating for food grains and their products and promote the application of RF technology in the food grain industry.

Radio frequency pasteurization and disinfestation techniques applied on low-moisture foods.

The shelf life of foods is usually limited due to the frequent contamination by pests and microorganisms. Although low risk of pathogen contamination and no growth potential compared to those in high water activity animal- or vegetal-derived products, the low-moisture food has still significantly contributed to the total number of foodborne infections and outbreaks. Radio frequency (RF) treatments can be classified as a dielectric heating, which is a promising technology for achieving effective food pasteurization and disinfestations because of the associated rapid and volumetric heating with large penetration depth. The RF technique could be applied at low-moisture food as both the dipole dispersion and ionic conductivity may play effective roles. It can selectively heat and kill the microorganisms/pests without damaging the agricultural product because of the large difference of dielectric loss factors between target microorganisms/pests and host foods. In this article, the low-moisture foods sterilized and disinfested by RF energy are reviewed through basic theories, dielectric properties, heating effect, and uniformity. The potential research directions for further RF heating applications are finally recommended in low-moisture foods.

Low-Frequency Magnetic Field of Appropriate Strengths Changed Secondary Metabolite Production and Na+ Concentration of Intracellular and Extracellular Monascus purpureus.

Monascus purpureus is used to yield edible pigments accompanied by mycotoxin-citrinin. A low-frequency (<300 Hz) magnetic field (LF-MF) affects microbial metabolism. The link of LF-MF with secondary metabolites and intracellular and extracellular Na+ levels in M. purpureus was determined. The fermentation broth was exposed to LF-MF during the first 2 days of fermentation and continuously cultured at 30°C and 200 rpm until the 8th day of fermentation. Results showed that LF-MF treatments didn't affect the growth of M. purpureus in liquid-state fermentation. Compared with the control, citrinin production showed a decrease of 45.0%, while yellow, red, and orange pigment production showed an increase of 72.9, 73.9, and 40.1%, respectively, with LF-MF treatment of 1.6 mT. This was in agreement with downregulation of pksCT and ctnA, and upregulation of pksPT, pigR, veA, and laeA at the transcriptional level. Moreover, 1.6 mT LF-MF exposure caused the transfer of Na+ from extracellular to intracellular, which was validated through the upregulation of transmembrane sensor synthesis genes and the changes in the relative expression levels of the P-type ATPase and protein phosphatase genes. This study established that LF-MF could inhibit citrinin and stimulate pigment production and change intracellular and extracellular Na+ concentrations. Bioelectromagnetics. 2020;41:289-297 © 2020 Bioelectromagnetics Society.

Complete regression of pulmonary squamous carcinoma in IPF following gemcitabine plus cisplatin: a case report and literature review.

BACKGROUND: Lung cancer is one of the most common co-morbid conditions in patients with idiopathic pulmonary fibrosis (IPF) and negatively affects the prognosis of IPF; Current guidelines for the management of IPF do not give a clear statement on how to manage these patients, and traditional chemotherapy for lung cancer had a limited efficiency rate. Here, we present a rare case of primary lung squamous carcinoma in a patient with IPF whose tumor completely regressed following gemcitabine plus cisplatin therapy; the cancer was no longer detectable after 2 years upon follow-up. CASE PRESENTATION: Sixty-seven year-old male patient with IPF was admitted to hospital due to acute onset hemoptysis. In addition to a definite usual interstitial pneumonia (UIP) pattern, a chest CT scan showed a non-enhancing nodular opacity in the right upper lobe and an enhancing nodule in the right lower lobe. Bronchoscopic biopsy of the nodule in the right lower lobe revealed squamous lung cancer. After 2 cycles of chemotherapy with gemcitabine and cisplatin, the tumor in the right lower lobe was no longer detectable after 2 years of follow-up; however, the nodule in the right upper lobe had increased significantly. Finally, Mycobacterium tuberculosis (MTB) was cultured from the bronchoalveolar (BAL) sample submitted at the last evaluation, and the patient was confirmed to have active pulmonary TB. CONCLUSION: We report the first documented case of complete pulmonary squamous carcinoma regression in IPF following gemcitabine plus cisplatin. Traditional chemotherapy is considered inadequate to cause the resulting regression of the tumor. The concomitant active pulmonary tuberculosis possibly underlies the mechanism.

Down-regulation of long non-coding RNA SNHG14 protects against acute lung injury induced by lipopolysaccharide through microRNA-34c-3p-dependent inhibition of WISP1.

BACKGROUND: Accumulating evidence has shown the important roles of long non-coding RNAs (lncRNAs) in acute lung injury (ALI). This study aimed to investigate the potential role of lncRNA small nucleolar RNA host gene 14 (SNHG14) in lipopolysaccharides (LPS)-induced ALI. METHODS: Expression of SNHG14, microRNA-34c-3p (miR-34c-3p) and Wnt1 inducible signaling pathway protein 1 (WISP1) in LPS-exposed mouse alveolar macrophages (MH-S) and lung tissues from mice with LPS-induced ALI was determined by reverse transcription quantitative polymerase chain reaction. The interactions among SNHG14, miR-34c-3p and WISP1 were analyzed by dual-luciferase reporter and RIP assays. Using gain-of-function or loss-of-function approaches, the contents of proinflammatory proteins were determined and MH-S cell viability was assessed to evaluate the in vitro functions of SNHG14, miR-34c-3p and WISP1, and wet/dry weight ratio and proinflammatory proteins in lung tissues were determined to assess their in vivo effects. RESULTS: SNHG14 and WISP1 expression was increased, while miR-34c-3p was decreased in ALI models. SNHG14 bound to miR-34c-3p, resulting in impaired miR-34c-3p-dependent down-regulation of WISP1. Both SNHG14 silencing and miR-34c-3p over-expression reduced the levels of proinflammatory proteins IL-18, IL-1ß, TNF-α and IL-6 and inhibited MH-S cell viability. SNHG14 silencing or miR-34c-3p over-expression decreased the wet/dry weight ratio in lung tissues from ALI mice. The reductions induced by SNHG14 silencing or miR-34c-3p over-expression were rescued by WISP1 over-expression. CONCLUSION: This study demonstrated that lncRNA SNHG14 silencing alleviated inflammation in LPS-induced ALI through miR-34c-3p-mediated inhibition of WISP1. Our findings suggest that lncRNA SNHG14 may serve as a therapeutic target for ALI.

3D food printing: main components selection by considering rheological properties.

3D printing, also referred to as additive manufacturing, offers a wide range of new processing possibilities to the food industry. This technology allows a layer by layer (bottom to top) printing of predefined slices of designed and desired objects. 3D printing potentially allows rapid manufacturing of complex objects, which are unhindered by design complexity, thus providing substantial liberty to create new and untested geometric shapes. In terms of food manufacturing, the potential that 3D food printing technologies can bring may revolutionize certain aspects of food manufacturing, providing the convenience of low-cost customized fabrication and even tailored nutrition control. The most common materials suitable for 3D food printing are carbohydrate, fat, protein, fiber and functional components. In the present study, the characteristics of raw materials or additives used during 3D printing, and requirements for estimating and improving their printing performance and self-supporting ability in extrusion-based printing regarding rheological characteristics of 3D food printing materials are reviewed. As an innovative process, 3D food printing may induce a revolution in certain areas of food manufacturing.

Microwave processing: Effects and impacts on food components.

As an efficient heating method, microwave processing has attracted attention both in academic research and industry. However, the mechanism of dielectric heating is quite distinct from that of the traditional conduction heating, and is widely applied as polar molecules and charged ions interaction with the alternative electromagnetic fields, resulting in fast and volumetric heating through their friction losses. Such a heating pattern would cause a certain change in microwave treatment, which is an unarguable reality. In this review, we made a retrospect of the essential knowledge about dielectric properties and summarized the concept of microwave heating, and the impact of microwave application on the main components of foods and agricultural products, which are classified as carbohydrates, lipids, proteins, chromatic/flavor substances, and vitamins. Finally, we offered a way to resolve the drawbacks of relevant microwave treatment and outlined the directions for future research.

Computer simulation for improving radio frequency (RF) heating uniformity of food products: A review.

Radio frequency (RF) heating has great potential for achieving rapid and volumetric heating in foods, providing safe and high-quality food products due to deep penetration depth, moisture self-balance effects, and leaving no chemical residues. However, the nonuniform heating problem (usually resulting in hot and cold spots in the heated product) needs to be resolved. The inhomogeneous temperature distribution not only affects the quality of the food but also raises the issue of food safety when the microorganisms or insects may not be controlled in the cold spots. The mathematical modeling for RF heating processes has been extensively studied in a wide variety of agricultural products recently. This paper presents a comprehensive review of recent progresses in computer simulation for RF heating uniformity improvement and the offered solutions to reduce the heating nonuniformity. It provides a brief introduction on the basic principle of RF heating technology, analyzes the applications of numerical simulation, and discusses the factors influencing the RF heating uniformity and the possible methods to improve heating uniformity. Mathematical modeling improves the understanding of RF heating of food and is essential to optimize the RF treatment protocol for pasteurization and disinfestation applications. Recommendations for future research have been proposed to further improve the accuracy of numerical models, by covering both heat and mass transfers in the model, validating these models with sample movement and mixing, and identifying the important model parameters by sensitivity analysis.

Inactivation kinetics of food-borne pathogens subjected to thermal treatments: a review.

Thermal processing technologies are safe and easy to control methods without leaving residues, and could be used to inactivate food-borne pathogens, ensure food quality and provide the food with sufficient stability during storage. Establishing inactivation kinetics of food-borne pathogens is essential in developing effective pasteurisation protocols without damaging food quality. This study presents a comprehensive review of recent progresses in inactivation kinetics of food-borne pathogens. It covers theoretical bases and experimental methods for developing thermal inactivation kinetics of food-borne pathogens and making comparisons and applications of the common thermal death kinetic models. Finally, it proposes possible recommendations on the future research directions of establishing inactivation kinetic models for food-borne pathogens in thermal processing.

Thermal inactivation of Aspergillus flavus in peanut kernels as influenced by temperature, water activity and heating rate.

Infection of Aspergillus flavus, which can produce aflatoxin, is a major problem for peanut safe storage. Thermal inactivation kinetics of Aspergillus flavus is essential to design an effective heat treatment process. In this study, thermal inactivation kinetics of Aspergillus flavus in peanut kernel flour at four water activity (aw) levels (0.720, 0.783, 0.846, and 0.921) with three temperatures for each aw was studied using a thermal-death-time heating block system and fitted with first-order kinetic and Weibull models. The influence of heating rates on thermotolerance of Aspergillus flavus was also investigated. The results showed that the Weibull distribution model had better coefficient of determination from 0.954 to 0.996, as compared to that (from 0.866 to 0.980) of the first-order kinetic model. An upward concavity was found with the inactivation curve, indicating a tailing effect. Model parameters (D, δ, and p) were estimated with the modified Bigelow equations to predict survival curves of Aspergillus flavus at any temperature and aw. The reduced heat resistance of Aspergillus flavus at high heating rates above 1 °C/min suggests that developing fast thermal processes is preferred for pasteurizing peanuts in food industry. A case study was presented for applying the cumulated lethal time model to design the industrial heating process based on the thermal kinetics of Aspergillus flavus.

Influence of controlled atmosphere on thermal inactivation of Escherichia coli ATCC 25922 in almond powder.

Heat controlled atmosphere (CA) treatments hold potential to pasteurize Salmonella enteritidis PT 30 in almonds. Nonpathogenic Escherichia coli ATCC 25922 was used as a surrogate species of pathogenic Salmonella for validation of thermal pasteurization to meet critical safety requirements. A controlled atmosphere/heating block system (CA-HBS) was used to rapidly determine thermal inactivation of E. coli ATCC 25922. D- and z-values of E. coli ATCC 25922 inoculated in almond powder were determined at four temperatures between 65 °C and 80 °C under different gas concentrations and heating rates. The results showed that D- and z-values of E. coli under CA treatment were significantly (P < 0.05) lower than those under regular atmosphere (RA) treatment at 4 given temperatures. Relatively higher CO2 concentrations (20%) and lower O2 concentrations (2%) were more effective to reduce thermal inactivation time. There were no significant differences in D-values of E. coli when heating rates were above 1 °C/min both in RA and CA treatments. But D-values significantly (P < 0.05) increased under RA treatment and decreased under CA treatment at lower heating rates. Combination of rapid heat and CA treatments could be a promising method for thermal inactivation of S. enteritidis PT 30 in almond powder.

Classification of Kiwifruit Grades Based on Fruit Shape Using a Single Camera.

This study aims to demonstrate the feasibility for classifying kiwifruit into shape grades by adding a single camera to current Chinese sorting lines equipped with weight sensors. Image processing methods are employed to calculate fruit length, maximum diameter of the equatorial section, and projected area. A stepwise multiple linear regression method is applied to select significant variables for predicting minimum diameter of the equatorial section and volume and to establish corresponding estimation models. Results show that length, maximum diameter of the equatorial section and weight are selected to predict the minimum diameter of the equatorial section, with the coefficient of determination of only 0.82 when compared to manual measurements. Weight and length are then selected to estimate the volume, which is in good agreement with the measured one with the coefficient of determination of 0.98. Fruit classification based on the estimated minimum diameter of the equatorial section achieves a low success rate of 84.6%, which is significantly improved using a linear combination of the length/maximum diameter of the equatorial section and projected area/length ratios, reaching 98.3%. Thus, it is possible for Chinese kiwifruit sorting lines to reach international standards of grading kiwifruit on fruit shape classification by adding a single camera.

Thermal Death Kinetics of Conogethes Punctiferalis (Lepidoptera: Pyralidae) as Influenced by Heating Rate and Life Stage.

Thermal death kinetics of Conogethes punctiferalis (Guenée) (Lepidoptera: Pyralidae) at different life stages, heating rate, and temperature is essential for developing postharvest treatments to control pests in chestnuts. Using a heating block system (HBS), the most heat-tolerant life stage of C. punctiferalis and the effects of heating rate (0.1, 0.5, 1, 5, and 10°C/min) on insect mortality were determined. The thermal death kinetic data of fifth-instar C. punctiferalis were obtained at temperatures between 44 and 50°C at a heating rate of 5°C/min. The results showed that the relative heat tolerance of C. punctiferalis was found to be fifth instars>pupae> third instars> eggs. To avoid the enhanced thermal tolerance of C. punctiferalis at low heating rates (0.1 or 0.5°C/min), a high heating rate of 5°C/min was selected to simulate the fast radio frequency heating in chestnuts and further determine the thermal death kinetic data. Thermal death curves of C. punctiferalis followed a 0th-order kinetic reaction model. The minimum exposure time to achieve 100% mortality was 55, 12, 6, and 3 min at 44, 46, 48, and 50°C, respectively. The activation energy for controlling C. punctiferalis was 482.15 kJ/mol with the z value of 4.09°C obtained from the thermal death-time curve. The information provided by thermal death kinetics for C. punctiferalis is useful in developing effective postharvest thermal treatment protocols for disinfesting chestnuts.

Role of histone H3K4 methyltransferase in regulating Monascus pigments production by red light-coupled magnetic field.

Light, magnetic field, and methylation affected the growth and secondary metabolism of fungi. The regulation effect of the three factors on the growth and Monascus pigments (MPs) synthesis of Monascus purpureus was investigated in this study. 5-azacytidine (5-AzaC), DNA methylation inhibitor, was used to treat M. purpureus (wild-type, WT). Twenty micromolar 5-AzaC significantly promoted the growth, development, and MPs yield. Moreover, 250 lux red light and red light coupled magnetic field (RLCMF) significantly promoted the biomass. For WT, red light, and RLCMF significantly promoted MPs yield. But compared with red light treatment, only 0.2 mT RLCMF promoted the alcohol-soluble MPs yield. For histone H3K4 methyltransferase complex subunit Ash2 gene knockout strain (ΔAsh2), only 0.2 mT RLCMF significantly promoted water-soluble MPs yield. Yet red light, 1.0 and 0.2 mT RLCMF significantly promoted alcohol-soluble MPs yield. This indicated that methylation affected the MPs biosynthesis. Red light and weaker MF had a synergistic effect on the growth and MPs synthesis of ΔAsh2. This result was further confirmed by the expression of related genes. Therefore, histone H3K4 methyltransferase was involved in the regulation of the growth, development, and MPs synthesis of M. purpureus by the RLCMF.