Studies on effect of temperature and time on textural and rheological properties of starch isolated from traditional rice cultivars of Kashmir (India).

Unlabelled: In the present study, the effect of storage temperature and time on the textural and rheological properties of starch gels from seven different rice cultivars having higher amylose content than the hybrid rice varieties were evaluated. Water solubility and swelling power increased with every 10C increase in temperature due to granule swelling and solubilization of starch wherein the maximum solubility was found in starch of Koshkari rice cultivar (0.721 to 13.50) and swelling power in starch of Zag rice cultivar (3.688 to 10.806). However, syneresis in the analyzed rice starch gels had shown a fluctuating trend for each individual cultivar at different storage periods in which the cultivars Zag had shown the highest values of syneresis during storage (4.123 to 4.957%). In the texture profile analysis of starch gel of these cultivars, Mushki Budgi had the highest value of hardness (0.723N), gumminess (36.262) and chewiness (31.056). The turbidity values of gelatinized starch suspensions from different rice cultivars increased progressively during the first 4 days of storage followed by a decrease in the 5th day coupled with slight increase in the 6th day. The highest turbidity was found in Zag ranging from 1.47 to 1.67 during refrigerated storage after 6 days. The rheological analysis revealed that Zag indicated the highest value of TG' (76.96C) whereas cultivars Koshkari and Mushki Kandi had shown the lowest value of TG' (74.34C) upon heating cycle.

Practical Applications: Rheological properties of starch are affected by amylose contents, lipid contents, branch chain length distribution of amylopectin. The starch from different varieties depicted variable textural and rheological properties at various time: temperature combinations. No research has been reported to explore the effect of time and temperature on the textural and rheological properties of starch isolated from these traditional rice cultivars. The starches from traditional rice cultivars (native or indigenous rice cultivars of a region) indicated novel characteristic as compared to other cultivars in terms of their higher amylose content, starch yield, purity, clarity, solubility, syneresis, turbidity, and rheology. The novelty of this research was to exploit the desirable properties of starch obtained from traditional rice cultivars that had better characteristics than the hybrid varieties. This in turn led the various agencies to motivate the farmers to encourage their cultivation, provide an essential platform to scientists to inherit their valuable characteristics.