Heat Treatments of Milled Rice and Properties of the Flours

Abstract

Cereal Chem. 82(2):228-232The effects of autoclave and oven treatments on the gelatinization of rice flour and on the rheological characteristics of its pastes were studied by differential scanning calorimetry (DSC), rapid viscoanalysis (RVA), and rotational viscometry. Flours from autoclave-treated rice (ATR) and oven-treated rice (OTR) were prepared, respectively, by heating at 120°C for 60 min and 160°C for 60 min followed by drying (ATR sample), and grinding at 2.2-12.9% moisture content. The rice flour dispersions were adjusted between pH 6.3 and 2.8 using 0.2M citrate buffer. The retort processing of rice flour in water pastes were done at 120°C for 20 min either once or twice. The gelatinization peak temperature (PT and T o ) and the peak temperature corresponding to the amylose-lipid complexes (T p3 ) of ATR increased at pH 6.3 and 2.8 compared with OTR and UTR flour. This indicates that the internal structures of the starch granules in ATR became more stable to heat and acid, even though the damaged starch content of ATR was 23% compared with 16 and 7%, respectively, for untreated rice flour (UTR) and OTR. The OTR flour pastes showed a gellike behavior at pH 4.5 after retort processing in water at 120°C for 20 min; however, the ATR mixture behaved more like a liquid paste. Decreases in the reducing sugar content of OTR and ATR pastes suggested that enzymes in the heat-treated rice were denatured, which retarded the hydrolysis of glucose chains and the rupture of starch granules during pasting.

Microwave absorption capacity of rice flour. Impact of the radiation on rice flour microstructure, thermal and viscometric properties

“…The subsequent magnification revealed that primarily rough and frayed particle shapes in native flour become more rounded and ovoid (Fig. 3-A2-B2-C2) in treated samples which was also confirmed previously by Takahashi et al (2005) for short grain rice autoclaved at 20% of moisture content. The particles' surface ( Fig.3-A3-B3-C3) appears to be smoother and aligned similar as reported by other researchers for short rice grain flour (Majzoobi et al, 2016) and foxtail millet flour (Amadou et al, 2014) when were submitted to convectional hydrothermal treatments.…”

Characterization of modified pearl millet (Pennisetum typhoides) starch

“…This may be attributed to the change in colour caused by Maillard reaction between reducing sugar from the heated starch and the amino group in the proteins during modification (Lorlowhakarn and Naivikul 2006). Increased a and b colour values have been reported for japonica milled heat moisture treated rice flour (Takahashi et al 2005).…”

The effects of heat-moisture treatment on avocado starch granules

“…The starch that is present in cereal, root and tuber crops has been extensively characterised; however, there has been little study of the characterisation of starch from avocado seeds, regarding its physicochemical properties [20][21][22][23][24][25][26].…”