Effect of Harvest Time on the Protein Composition (Glutelin, Prolamin, Albumin) and Amylose Content in Paddy Rice Cultivated by Aigamo Duck Farming System.

Abstract

Previously, we suggested that cultivation of paddy rice by Aigamo duck farming system, delayed the harvest time by about 10 days and improved the taste of rice due to the increased grain yield accompanied with the decrease in the number of green-kernel rice and protein content in brown rice. In this study, we examined the content and composition of protein and amylose content in the grain samples used in our previous report. The total protein content in brown and milled rice tended to decrease with the delay of the harvest time, irrespective of the cultivar(Koshihikari or Kinuhikari)by both the standard and Aigamo duck cultivation methods. The protein in the brown rice harvested either at maturity, 10 days earlier or 10 days later, consisted of 66.0-67.7% glutelin, 18.8%-20.8% albumin+globulin and 12.5-14.5% prolamin. The composition of protein varied slightly with the cultivar and the method of cultivation, but scarcely with the harvest time. The same was also the case for the protein in milled rice. Thus, the 10-days later harvest time did not affect the protein composition markedly even in the rice cultivated by Aigamo duck farming system. Amylose content in milled rice tended to decrease with the delay of harvest time in both cultivars and cultivation methods examined. These results suggest that late harvest in Aigamo duck farming system improved the rice taste to the decrease in the number of green-kerneled rice and the contents of protein and amylose.