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Summary: Radio frequency (RF) treatment at 27.12 MHz was employed to inactivate the anti‐nutritional factors (ANFs), including lipoxygenase (LOX), urease and trypsin inhibitor to minimise deleterious effects caused by conventional hot‐air heating. The effects of RF heating on the ANF activities, physicochemical properties and processing quality of intact soybean were investigated. The results revealed that ANF activities were effectively inactivated within 300 s by RF heating and inactivation rates of LOX, urease and trypsin inhibitor were 95.2% (270 s), 93.4% (285 s) and 89.4% (300 s), respectively. In addition, RF heating improved physicochemical properties and processing quality of soybean products when the trypsin inhibitor was inactivated. On the contrast, conventional thermal treatment significantly decreased functional properties and led to the formation of greater aggregates. Our results may provide a novel method to inactivate endogenous enzyme in crops without negative impact on processing quality. [ABSTRACT FROM AUTHOR]

Summary: Polyunsaturated fatty acids are oxidised to generate beany flavour under catalysis of lipoxygenase (LOX). Using conventional thermal treatment to inactivate LOX lead to a serious nutritional and functional loss in soybean products due to the prolonged exposure to the high‐temperature environment. Radio frequency (RF) is a different type of heating technology that sample is heated inside and outside at the same time with deep penetration. RF treatment was proposed to process soybean to rapidly inactivate LOX while remaining the quality and functional properties of soybean product. The results showed that the inactivation rate of LOX subjected to RF treatment for 210 s was 94.30%, as compared with 3.08% under conventional thermal treatment (110 °C) for the same duration. Functional properties of soybean protein isolate (SPI) after RF treatment were much higher than that of SPI with conventional thermal treatment. Analysis of the volatile compounds of soy milk indicated that the relative concentration of hexanal decreased from 521 to 116 μg L−1 and that of 1‐hexanol decreased from 271 to 6.99 μg L−1. Therefore, RF treatment could better improve the sensory properties of soy milk. This study mainly indicated the difference in inactivation rate of lipoxygenase of intact soybean by comparing two approaches (RF treatment and conventional thermal treatment). After that, we evaluated the shifts in the functional properties of soybean protein isolates under previous methods and the changes in the quality associated with lipoxygenase. [ABSTRACT FROM AUTHOR]

Summary: Radio frequency (RF) preprocessing combined with pulsed electric field (PEF) processing was employed to inactivate polyphenol oxidase (PPO) in apple juice. PPO enzyme levels, loss of total phenolic content (TPC), colours and volatile components in the apple juice were subsequently determined and compared with conventional processing methods (60 °C for 10 min and 70 °C for 10 min). Results indicated that, when the apple tissue was preprocessed using RF for 10 min, the residual activity of PPO decreased to 13.57%; when the squeezed juice was processed by PEF, the residual activity decreased to about 5% at 15–35 kV cm−1 for 400 μs. RF treatment caused no significant loss in TPC. Compared with the conventionally processed samples, the apple juice that was RF‐treated for 10 min and PEF‐treated at 15 kV cm−1 for 400 μs increased its lightness and maintained its fresh‐like flavour. [ABSTRACT FROM AUTHOR]

BACKGROUND Pulsed electric field ( PEF) processing is progressing towards application for liquid egg to ensure microbial safety. However, it usually causes protein aggregation, and the mechanism is still unclear. In this study, egg white protein was applied to investigate the changes in protein structure and mechanism of aggregates formation and a comparison was made with thermal treatment. RESULTS Soluble protein content decreased with the increase of turbidity after both treatments. Fluorescence intensity and free sulfhydryl content were increased after being treated at 70 °C for 4 min. Less-remarkable changes of hydrophobicity were observed after PEF treatments (30 kV cm−1, 800 µs). Soluble and insoluble aggregates were observed by thermal treatment, and disulfide bonds were the main binding forces. The main components of insoluble aggregates formed by thermal treatment were ovotransferrin (30.58%), lysozyme (18.47%) and ovalbumin (14.20%). While only insoluble aggregates were detected during PEF processes, which consists of ovotransferrin (11.86%), lysozyme (21.11%) and ovalbumin (31.07%). Electrostatic interaction played a very important role in the aggregates formation. CONCLUSION PEF had a minor impact on the structure of egg white protein. PEF had insignificant influence on heat-sensitive protein, indicating that PEF has potential in processing food with high biological activity and heat sensitive properties. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Radio frequency (RF) processing was proposed to inactivate polyphenol oxidase (PPO) in apple tissue for improved juice quality. PPO in apple tissue exists as membrane‐bound PPO (mPPO) and soluble PPO (sPPO); mPPO is bound in chloroplast membranes and separated from phenolic substrates, preventing catalytic reaction, whereas sPPO is soluble in lumen. When cells break down, mPPO is released and comes in contact with phenolic substrates, contributing to browning and discoloration in juice. Research indicates that after RF treatment, inactivation of mPPO and sPPO in apple tissue was easier to achieve than extracted PPO. In addition, mPPO exhibited a lower thermal stability than that of sPPO. Treatment with RF for 10 min in apple tissue could effectively inactivate PPO and maintain a higher quality of squeezed apple juice than that of freshly squeezed juice treated by conventional thermal methods (65 °C for 10 min and 75 °C for 10 min). Practical applications: In fruit and vegetable processing industry, enzymatic browning is a difficult issue that leads to the deterioration of product quality. RF treatment can inactivate PPO rapidly in food and agricultural products to inhibit browning without heat conduction and overheated food surfaces, keeping high quality of the products. Results in this study could provide references for the application of RF technology on fruit and vegetable processing industry to inactivate endogenous enzyme. [ABSTRACT FROM AUTHOR]