Studies on the nature of carbohydrate moiety in high yielding varieties of rice

The impact of germination on the characteristics of brown rice flour and starch

BACKGROUND

In recent years, germinated brown rice as a functional food has received great attention with its improved sensory and nutritional properties. Particularly of interest are the high levels of γ-amino butyric acid (GABA) which can be obtained during germination. However, more studies are needed to fully understand the effect of germination on the physicochemical properties of brown rice.

RESULT

Germination altered the chemical composition of brown rice, resulting in an increase in reducing sugar and ash content, and a reduction in amylose. Solubility, paste viscosity, transition temperatures (T(o) , T(p) and T(c) ) and percentage of retrogradation (%Retrogradation) were decreased, while swelling power and turbidity were significantly increased. Scanning electron micrographs indicated that starch granules from germinated brown rice became smaller and less homogeneous. Moreover, germination shortened the chain length of amylopectin and amylose molecules.

CONCLUSION

This investigation provides information on changes in the characteristics of rice flour and rice starch during germination, leading to a better understanding on the chemistry of brown rice germination.

Soluble amylose cornstarch is more digestible than soluble amylopectin potato starch in rats

In liquid enteral formulations, high molecular weight soluble starches may be able to replace glucose and low molecular weight glucose polymers that have high glycemic indices. Male rats were fed either commercial cornstarch, dextrose, modified soluble potato (70-75% amylopectin) starch, or modified soluble amylomaize-7 (70% amylose) starch for 4 wk. Body weights did not differ among the groups. Food consumption was significantly higher in the two modified starch-fed groups than in the two control groups. Commercial cornstarch, dextrose, modified potato starch and modified amylomaize-7 starch were 100 +/- 0, 100 +/- 0, 69.0 +/- 1.0 and 91.5 +/- 0.8% digestible, respectively (n = 9, mean +/- SEM). The modified potato starch-fed group deposited the least fat, protein and energy. In both modified starch-fed groups, liver weights were significantly greater than in the two control groups. In food-deprived rats, serum free fatty acid concentrations in the modified potato starch-fed group were significantly higher than in the two control groups, and serum glucose concentrations were significantly higher in the two modified starch-fed groups than in the controls. The insulin to glucagon ratios were significantly lower in the modified potato starch-fed and amylomaize-7 starch-fed groups than in the dextrose-fed control group. Serum protein concentrations, measured after food deprivation, were significantly lower in the modified potato starch-fed group than in the other three groups. Gluconeogenesis from fermentation products might account for the high serum glucose concentrations in the two experimental groups. These data indicate that only the modified amylomaize-7 starch may be useful in the development of food products for liquid nutritional supplements because of the high digestibility and the low resultant insulin levels.