Changes in the Contents of Carbohydrates and Organic Acids in FruitBodies of Hiratake-Mushroom [Pleurotus ostreatus (Fr.) Quel] during Development and Post-Harvest Storage

Abstract

Changes in the contents of low molecular weight carbohydrates, polysaccharides and organic acids in pilei, stipes and bases of stipes of fruit-bodies of Hiratake mushroom (Pleurotus ostreatus) during development and post-harvest storage at 20°C were investigated. (1) The total free sugar content in the mushroom during development was found in the range of 6.8-15.6% in pilei, 10.1-27.2% in stipes, and 9.3-24.9% in bases of stipes on the dry weight basis, respectively, while the total sugar alcohol content was 3.0-3.8% in pilei, 3.2-3.6% in stipes, and 1.0-2.9% in bases stipes, respectively. In this mushroom, trehalose, mannitol, glucose, fructose and arabitol were identified, and trehalose and mannitol were found to be major among them. The content, of each element varied individually during the development, and there was remarkable difference among pilei, stipes and bases of stipes. During post-harvest storage, the contents of each element, except mannitol, decreased. Especially the decrease of trehalose was marked. The content of mannitol during post-harvest storage increased for the first three days, but it decreased from then on. (2) The polysaccharide content in the mushroom during development was found in the range of 40.3-44.3% in pilei, 47.3-50.2% in stipes, and 54.2-55.8% in bases of stipes respectively. The contents of five polysacchride fractions-formic acid-soluble fraction (R-glucan), alkali-soluble, acid-soluble fraction, hot alkli-soluble fraction, alkali-soluble, acid-insoluble fraction (S-glucan) and chitin-showed no change during development and post-harvest storage, but the content of acetic acid-soluble fraction decreased during storage. (3) The organic acid content in the mushroom during development was found in the range of 3.6-4.4% in pilei, 4.5-5.1% in stipes, and 6.0-7.4% in bases of stipes. In this mushroom, eleven kinds of organic acids were identified. Malic, pyroglutamic, fumaric, succinic and citric acids were found to be major among them. There were remarkable differences in the distribution patterns of their organic acid among pilei, stipes and bases of stipes. During post-harvest storage, the contents of each element increased without exception.