Changes in Chemical Structure of Cell Wall Polysaccharides in Flesh Tissue of Rosaceae fruits in Concerning with the Mealy Texture.

果实软化一般随果实成熟而发生，但软化果实的质地因品种不同而不同。苹果、梨和草莓等蔷薇科果实的成熟后也表现出不同的质地。(1)苹果果实软化(过熟)的质地可分为粉状和软肉两种类型。在对苹果果肉的研究中，根据果肉中观察到的细胞间黏附松动和细胞分离的事实，对四种方法进行了比较，以量化果肉的粉化程度。在本研究中，肉盘在蔗糖溶液中摇动，测量摇动前后圆盘的重量，以粉化程度表示减少的百分比。比较9个成熟苹果品种的粉化程度，‘岩井’、‘乔纳金’和‘红星’的果肉相对较易降解，‘津格鲁’和‘金冠’的果肉降解较小。将‘S…MORE TARKING CALISE(SD)’和‘GD(金冠)’果肉中的果胶物质分成三个组分(H20、EDTA和HCl可溶性)，并测定了各组分中糖醛酸和中性糖的含量。在‘SD’粉状果肉中，EDTA组分的戊糖含量显著低于非粉状果肉和‘GD’。由于EDTA组分中的果胶物质所含的中性糖比其他组分少，因此认为该组分中的多糖存在于细胞间的中层中。用气相色谱对果胶组分的糖组成进行了比较，发现粉状果肉中EDTA组分的阿拉伯糖含量明显低于非粉状果肉。通过对糖链的甲基化分析发现，在‘SD’中，果胶类物质的鼠李糖醛酸链上的中性糖侧链上的末端阿拉伯糖残基随着糊化程度的增加而减少。而三元半乳糖则随粉化程度的增加而增加。结果表明，苹果果实成熟过程中，果肉细胞间中层果胶物质的鼠李糖半乳糖侧链主链上的半乳糖残基释放出末端阿拉伯糖，引起果实糊化。(2)7个苹果品种果实生长过程中细胞壁多糖结构的变化，4个苹果品种果实细胞壁木葡聚糖的结构分析，3个苹果品种果实生长过程中苹果细胞膜透性的变化，梨树的年龄、活力、形状和套袋对果实品质的影响。并对辣椒草莓与日本草莓的细胞壁多糖进行了比较分析。较少

Softening of fruit occur generaly along with maturation, but the texture of the softened fruit differd by species. Ripened fruits of Rosaseae, such as apple, pear and strawberry also demonstrate different texture.(1) In apple, the texture of softened (over-ripened) fruit can be classified into two types, mealy and soft flesh. In the study of apple flesh, based on the fact that in mealy flesh adhesion between cells loosened and cell separation was observed, to quantify the degree of mealines, four methods were compared. In this study, flesh disks were shaken in sucrose solution, the weights of the disks before and after shaking were maesured, and the percentage decrease was expressed as the degree of mealiness. In comparison of the degree of mealiness of 9 cultivars of ripened apple fruits, the flesh of 'Iwai', 'Jonagold' and 'Starking Delicious' were comparatively easy to be degraded and that of 'Tsugaru' and 'Golden Delicious' were degraded little. Pectic substances in the flesh of 'S … More tarking Delicious(SD)'and 'Golden Delicious(GD)' was fractionated into three fractions (H20, EDTA and HCl soluble), and uronic acid and neutral sugar contents in each fraction were determined. In the mealy flesh of 'SD', pentose content in EDTA fraction was remarkably less than the not mealy flesh and 'GD' . As the pectic substances in EDTA fraction include less neutral sugars as compared with the other pectic fractions, it is considered that this fraction is considered to be the polysaccharides exist in middle lamella between cells. Sugar composition of pectic fractions were compared using gas chromatography, and it was found that the arabinose content of EDTA fraction in mealy flesh was rekarkably low compared with not mealy flesh. By the methylation analysis of the the linkage of sugars, it was found that in 'SD', the terminal arabinose residue on the neutral sugar side chain on the rhamnogaracturonan of pectic substances decreased with the progress of mealiness. In contast, terninal galactose increased with the degree of mealiness. From thse results, during the apple fruit ripening, it was suposed that the mealiness can beinduced by the release of terminal arabinose from the galactose residue on the neutral sugar side chain on the rhamnogalacturonan main chain of the pectic substances of middle lamella between flesh cells.(2) Structural changes in cell wall polysaccharides during fruit growth of seven apple cultivars, structural analysis of xyloglucans isolated from the fruit cell walls of four apple cultivars, changes in permeability of apple cell membrane during fruit growth of three apple cultivars, effects of age, vigor and shape of pear trees and bagging of fruit on the fruit quality, and characterization of cell wall poly-saccharides of Chili strawbwrry in comparison with Japanese strawberry, were investigated. Less