Abstract
The most frequent microbial contamination found in cereal were mainly caused by moulds which cell metabolic activities were closely related to catalase and lactate dehydrogenase. Here, we studied the effects of Low-Dose Microwave Radiation (LDMR; 2450 Hz, 2.4 W/g) on physicochemical characteristics of catalase and lactate dehydrogenase and compared them to the effects of conventional heating treatment (water bath), to provide a theoretical basis for using LDMR for moulds control in cereal. When catalase or lactate dehydrogenase was subjected to LDMR, the enzyme’s sulfydryl content, hydrophobic value and decreasing rate of enzyme activity were universally higher than when the enzyme was subjected to conductive heating. The activity of catalase and lactate dehydrogenase decreased with the rise in temperature. After LDMR exposure or heat conduction treatment, the secondary structure of catalase and lactate dehydrogenase were changed. Moreover, the heat inactivation temperature and conformation transition temperature of catalase were higher than those of lactate dehydrogenase.
Highlights
Mould contamination in cereal grains, which can occur before or after harvest as well as during transportation or storage, decreases their nutritional value and constitutes health hazards (Paolesse et al, 2006; Conkova et al, 2006)
Research has revealed that the microwave can inhibit or destroy the activity of the enzyme related to biological oxidation, breathing metabolism and energy generation in the cell leading to microbial death (Fu et al, 2003)
Sulfydryl content of catalase and lactate dehydrogenase: The effect of LDMR and conventional heating on the sulfydryl content of catalase is illustrated in Fig. 1 (I)
Summary
Mould contamination in cereal grains, which can occur before or after harvest as well as during transportation or storage, decreases their nutritional value and constitutes health hazards (Paolesse et al, 2006; Conkova et al, 2006). Low-Dose (about 2.0 kW/kg) Microwave Radiation (LDMR) is claimed to have better effect on maintaining food quality and can kill pests and molds in comparison with high-dose microwave (Fang et al, 2011; Lu et al, 2010). Catalase and lactate dehydrogenase play a very important role in some physiological activities such as biological oxidation, detoxification and participating in active oxygen metabolism (Zamocky and Koller, 1999; Chelikani et al, 2004; Legrand et al, 1992). Both enzymes are closely related to the growth and metabolism of moulds. Research has revealed that the microwave can inhibit or destroy the activity of the enzyme related to biological oxidation, breathing metabolism and energy generation in the cell leading to microbial death (Fu et al, 2003)
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