THE RELATIONSHIP BETWEEN THE CONSTITUENTS OF CELL-WALL POLYSACCHARIDES AND HARDNESS OF BRINED UME FRUIT

The cell wall polysaccharides in fresh and brined ume fruits were fractionated, and the relation between their chemical composition and hardness was investigated. The main components of each cell wall polysaccharide were as follows:pectin fraction (PS) containing galacturonic acid (AGA), hemicellulose I fraction (HC-I) containing neutral sugars and proteins, hemicellulose II (HC-II) containing neutral sugars and ash, and cellulose fraction (CL) containing neutral sugars. In the Control (ume fruit brined with NaCl solution), there was a decrease in HC-I and CL in the cell wall, and an increase in PS, as well as a softening of texture. On the other hand, a decrease of PS and an increase of CL were observed in the Ca-added group (ume fruit brined with NaCl solution and Ca hydroxide), which maintained a hard texture. A decrease in the methoxyl group and an increase in ash and Ca content were observed in PS of the Ca-added group. A decrease of neutral sugar (especially, glucose composition) and an increase in ash, Ca and AGA content were observed in CL. CL contained AGA and neutral sugars such as arabinose and galactose, which were thought to be firmly bound to cellulose microfibrils. Therefore, it was assumed that the hardness in Umezuke may reflect a difference in the mechanism of bonding between CL existing in the secondary cell wall and other matrix polysaccharides.