Age related histological and cooking characteristics of rice

Abstract

Experiments were conducted to study the effect of degree of polishing (under polished, well polished and over polished) and aging (0 to 180 days, at an interval of 30 days) on quality aspects of Pusa basmati variety of aromatic rice. An attempt has been made to investigate the histological and cooking quality changes occurring in rice, when stored for a period of six months. The cooking quality attributes considered were volume expansion ratio, kernel elongation ratio, solids loss, insoluble amylose content, alkali digestion value, gel consistency and aroma. Effect of degree of polishing on cooking quality changes was significant up to 8% of degree of polishing. With the progress of aging period, the kernel elongation ratio (24%) and volume expansion ratio (22%) increased while there was a reduction in solids loss (55%), alkali digestion score (32%) and gel consistency values (21%). The hot water insoluble fraction of amylose was found to be increased (33%) in aged rice which could be correlated with the desirable changes in cooking properties. The improvement in the cooking properties was faster during the initial three to four months of aging, thereafter the properties changed at a reduced rate. The changes were reflected more in well polished rice than that in under polished rice. A degree of milling more than 8% (over polished) did not influence these results to a great extent. The study concluded that hot water insoluble amylose content may be a major determinant of cooked rice properties as the structural changes show the increased number of large granules indicating decreased solubility.