The effect of heat-moisture treatment on the molecular changes of starch and protein in high- and low-amylose rice flours and its physicochemical properties

2024-07-08T11:57:48+07:00

Heat-moisture treatment (HMT) could alter the starch and protein structures of rice flour resulting in the change of physicochemical properties. The aim of the study was to investigate the effect of HMT (moisture content of 20%, at 110°C for 14 h) on the molecular changes of starch and protein, pasting properties, and textural characteristics of high-(PTT80 and KTH17) and low-(KDML105) amylose rice flours. The protein and fat contents of all HMT-modified rice flours (HPTT, HKTH and HKDML) were altered slightly and the resistant starch content of high-amylose rice flour increased. In addition, after HMT, the total relative crystallinity (RC) of all rice flour increased. For high-amylose rice flour, the RC of V-type complexes increased after HMT. The HMT-modified rice flours with high-amylose content (HPTT and HKTH) displayed starch molecular rearrangement. The HPTT exhibited increased short-range ordered structures; conversely, the HKDML, low-amylose content, had decreased short-range ordered structures. Furthermore, the FTIR results showed that the secondary protein structure was altered, β-turn and random coil to β-sheet structures, after HMT. The gelatinization temperatures of HPTT and HKTH were higher than their native rice flour. All HMT-modified rice flours have a higher pasting temperature, lower peak viscosity, and lower breakdown viscosity compared to their native rice flour. Additionally, after HMT, the high-amylose rice flour gel (both HPTT and HKTH) had greater hardness but lower cohesiveness than the low-amylose rice flour gel (HKDML). This study suggested that HMT not only affects the starch structural changes but the protein structure as well and their change is responsible for their pasting and textural properties. The HMT-modified rice flour will be utilized in gluten-free and other functional products.

The Extraction conditions for bioactive compounds from germinated Black Jasmine rice using aqueous two-phase system

2024-05-23T15:09:09+07:00

Black Jasmine rice is rich in bioactive compounds such as anthocyanins, phenolics, and flavonoids. It can be germinated to gain more bioactive compounds especially gamma-aminobutyric acid (GABA). Generally, bioactive substances can be extracted using several methods, and the aqueous two-phase system (ATPS) is one of the most environmentally friendly extraction methods. Therefore, this work focused on studying the conditions for extracting bioactive compounds from germinated black jasmine rice using the ATPS by studying ethanol concentrations of 32%, 34%, 36%, 38%, 40%, 42%, and 44%, and the sample-to-solvent ratio of 1:50, 1:40, 1:30, 1:20, and 1:10 using ammonium sulfate at 16%. The results showed that an ethanol concentration of 34% and a sample-to-solvent ratio of 1:40 were optimal for extracting a high amount of GABA. Ammonium sulfate concentration of 14%, 16%, 18%, 20%, and 22% were subsequently studied, using an ethanol concentration of 34% and a sample-to-solvent ratio of 1:40., It was found that GABA, phenolics, flavonoids, and Fe2+ chelating activity decreased as the concentration of ammonium sulfate increased., However, the amount of anthocyanin increased with the concentration of ammonium sulfate. This indicated that ATPS can be an alternative environmentally friendly extraction method for bioactive compounds from germinated rice.

Food and Applied Bioscience Journal

The effect of heat-moisture treatment on the molecular changes of starch and protein in high- and low-amylose rice flours and its physicochemical properties

The Extraction conditions for bioactive compounds from germinated Black Jasmine rice using aqueous two-phase system