Inactivation of lipoxygenase in soybean by radio frequency treatment

Abstract

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.

Legume lipoxygenase: Strategies for application in food industry

“…However, owing to the low molar absorptivity of the reaction products, the determination of low specific activity preparations is still susceptible to interference by protein absorption. This method has been widely used in recent studies of legume LOX including pea (Akyol, Alpas, & Bayındırlı, 2006;Leone et al, 2001;Szymanowska et al, 2009), mung bean seeds (Aanangi et al, 2016), and soybean and soy product (Jiang et al, 2018;Manassero, Vaudagna, Sancho, Añón, & Speroni, 2016;Tedjo, Eshtiaghi, & Knorr, 2000).…”

“…This is because RF treatment has a shorter heating time and faster thermal transmission rate. Different from traditional heating technology, RF heats the sample inside and outside simultaneously (Jiang et al, 2018 however, the same duration of conventional thermal treatment (110 C) reached only 3.08%. Moreover, the functional properties of RF-treated soybean protein isolate (SPI) were much higher than the conventional thermal-treated SPI samples.…”

“…Moreover, the functional properties of RF-treated soybean protein isolate (SPI) were much higher than the conventional thermal-treated SPI samples. RF could better improve the sensory quality by reducing the content of hexanal and 1-hexanol, which are responsible for the unpleasant aroma production (Jiang et al, 2018). However, nonuniformity heating might happen especially in heterogeneous food material with irregular shape (Jiao, Tang, Wang, & Koral, 2018).…”

Highly effective inactivation of anti‐nutritional factors (lipoxygenase, urease and trypsin inhibitor) in soybean by radio frequency treatment

“…The determination of urease and trypsin inhibitor activity of soybean samples was carried out following the procedures reported by Yalcin & Basman (2015) and Li et al (2018), respectively. The LOX activity of samples was determined according to the method of Jiang et al (2018). LOX activity assay required 0.1 mL of 1:5 diluted crude enzyme solution and 3 mL of 0.2 M borate buffer at pH 9.0 containing 0.02% (v/ v) of linoleic acid and Tween 20.…”

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

“…92 RF can replace traditional hot-water blanching to inactivate LOX and PPO while maintaining the quality of a treated product. 93 Jiang et al, 94 for example, proposed that RF could be used to rapidly inactivate LOX while maintaining the quality and functional properties of soybean products. The results showed that the inactivation of LOX was 94% after 210 s of RF treatment; such an inactivation in the case of conventional heat treatment (at 110°C) was only 3%.…”