Effect of annealing temperature on gelatinization of rice starch suspension as studied by rheological and thermal measurements

Mechanism of peptides from rice hydrolyzed proteins hindering starch digestion subjected to hydrothermal treatment

Clarifying the interactions between food components is critical in designing carbohydrate-based foods with low digestibility. To date, the hindering effect of starch-protein interactions on starch digestion has attracted extensive attention. In this study, rice proteins were further hydrolyzed, and rice peptides (RP) with different molecular weights were obtained by ultrafiltration. The effects and possible mechanisms of RP with different molecular weights on the structure, thermal properties, and in vitro digestibility of cooked rice starch were investigated. All peptides slowed the digestion of rice starch in a concentration-dependent manner. A concentration of 10% RP_>10 decreased the rapidly digestible starch content from 68.02 to 45.90 g/100 g, and increased the resistant starch content from 17.54 to 36.54 g/100 g. The addition of RP improved the thermal stability of the starch and reduced the amount of leached amylose. Infrared analysis shows that strong hydrogen bonds formed between RP (especially RP_>10) and starch during co-gelatinization. In addition, RP improved the compactness of aggregated structure and played an important role in hindering the enzymatic hydrolysis of starch. These results enrich the theory of starch-protein interactions and have important implications for the development of carbohydrate-based foods with low digestibility and protein functional foods.

Effects of soaking, acidity and temperature on cadmium and lead removal from rice

In this research, effect of soaking time, acidity and temperature on the removal of lead and cadmium from rice was investigated. Different rice treatments were involved i.e. three soaking times (0, 15, and 30 min), three temperatures (20, 25, and 30 °C) and four concentrations of glacial acetic acid (0.5%, 1%, 2%, and 3%). Results showed that few samples have shown lead concentrations above the maximum limit set by the World Health Organization (WHO) and the UN Food and Agriculture Organization (FAO) of 0.2 mg/kg, whereas, all cadmium concentrations were below the limit of 0.4 mg/kg. A decrease in lead and cadmium concentrations were observed with increasing time of soaking. Lead had the lowest concentration at 20 °C, while cadmium had the lowest concentration at 30 °C. Cadmium concentration decreased with increasing water acidity, while the lead concentration reached the lowest concentration with 1% acidity.