Effect of Superheated Steam Treatment on Enzymes Related to Lipid Oxidation of Brown Rice

Abstract

When brown rice is preserved for a long period of time, a stale flavor (komai-shu) develops as a result of lipid oxidation by enzymes. In order to inactivate the enzymes, brown rice was treated with superheated steam. Superheated steam treatment for about 1 min, at all temperatures, caused a decrease in the enzymatic activity related lipid oxidation. On the other hand, the degree of starch damage did not increase during superheated steam treatment below 150℃. These results show that superheated steam treatment at a low temperature and for a short time is enough to inactivate the enzyme in brown rice, and does not influence starch quality. It was expected that enzyme inactivation by superheated steam treatment would be effective in suppressing the generation of stale flavor during long preservation periods.

Selective peroxidase inactivation of lightly milled rice by superheated steam

“…Therefore, low temperature and short time SS treatments (110 C, 3.5 min and 120 C, 2.5 min) were enough to suppress the peroxidase activity in LMR and the treatment time required to inactivate peroxidase in LMR was shorter than that of synthermal HA. These results are in agreement with that of Satou et al (2010), who observed that a short time (1 min) SS treatment at low temperature (125 C) was enough to inactivate lipolytic enzymes of brown rice. Head et al (2010) also reported that low temperature SS (110e160 C) was effective to inactivate peroxidase in oat groats, and the SS processed oat groats has good storage stability (Head et al, 2010(Head et al, , 2011.…”

“…In contrast, the moisture content in SS treated LMR was increased slightly at the initial stage, and then decreased at rates much lower than those of synthermal HA treated LMR. Satou et al (2010) also found a slight increase in moisture content at the initial stage when brown rice was subjected to low temperature SS (125 and 150 C). This phenomenon was probably due to the high relative humidity of superheated steam reducing the drying effect.…”

“…The oat groats processed by SS have acceptable storage stability due to the inactivation of peroxidase (Head et al, 2011(Head et al, , 2010. Satou et al (2010) suggested that SS treatment is enough to inactivate lipolytic enzymes in brown rice at a low temperature (above 125 C) within a short time. However, little research has been conducted to investigate the effects of SS on physicochemical properties such as appearance (fissures, whiteness and translucency), cooking quality (optimum cooking time, water absorption, volume expansion ratio and total solids loss), texture profile (hardness, adhesiveness, chewiness and cohesiveness), and micro-mechanical behavior of LMR.…”

“…Lipase is more stable than lipoxygenase in rice (Satou et al, 2010;Zhong et al, 2013), while peroxidases present higher heat-resistance than lipases (da Silva et al, 2006;Head et al, 2010). Accordingly, the peroxidase activity test was used for monitoring the adequate heating for stabilizing LMR in this study.…”

Recent Developments in Superheated Steam Processing of Foods—A Review

“…The extensive literature survey carried out in this work indicated that the majority of these reports are on drying of food products (Li et al, 1999;Tang et al, 2000;Tang and Cenkowski, 2000;Caixeta et al, 2002;Markowski et al, 2003;Huang et al, 2004;Nathakaranakule et al, 2007;Nimmol et al, 2007;Suvarnakuta et al, 2011). The other applications reported are enzyme inactivation (Pronyk et al, 2005;Sotome et al, 2009;Satou et al, 2010;Head et al, 2011), decontamination Cenkowski et al, 2007;Kondijoyan and Portanguen, 2008) and microbial load reduction (Shull and Ernst, 1962;Nygaard and Hostmark, 2008;Head et al, 2008) of foods. Recently, process improvisations such as superheated steam processing under low pressure, fluidized bed heating, in combination with infrared radiation and with water droplets have been attempted by researchers to improve product quality and energy efficiency.…”