Study On Cell Wall Polysaccharide Microstructure And Degradation Mode Of Postharvest Drupe Fruits

Drupe fruits(such as peach,apricot,plum and cherry) are rich in many nutrients which arenecessary for eople’s daily life and favored by consumers. Because the durpe fruits have highrespiration rate, they are easy to develop ripening and softening. The texture is not onlyrelated to the quality of the fruits, but also post-harvest storage and transportation. Softeningof fruit texture is related with cell wall polysaccharide composition and morphology, whilepectinase, temperature, storage time, and cultivars are likely to affect the composition andstructure of the polysaccharides. In order to elucidate the relationship among these affectingfactors and final texture properties, the evolution and the general degradation pattern of cellwall polysaccharide microscale morphology of postharvest peach and apricot fruits. Theresults will provide a theoretical basis for exploring the microscopic reasons of the texturechanges of drupe fruits.Firmness is one of the most important quality attributes of apricot fruits and is associatedwith chelate-soluble pectin (CSP). To elucidate the evolution of CSP during postharvest, invitro investigation of pectinase on CSP of apricot fruits was applied to simulate the in vivoevolution of CSP fraction during postharvest. Relative frequency of widths less than31.25nmwas3.6%for control group while it was16.2%,52.0%and65.5%, respectively for1:10000(pectinase: CSP),1:1000and1:100pectinase groups. Most of the CSP lengths were0.5μm-1.0μm while it was0μm-1μm for pectinase treated groups. It was found that effects ofpectinase treatment were similar to those of storage time on CSP nanostructures.The resultsindicated that changes of CSP during storage might be due to the reaction between pectinaseand CSP fraction.Effects of temperature and time on microstructure changes of cellulose andhemicellulose of two peach cultivars(‘Cangfang’and ‘Songsen’) were investigated. Theresults revealed that the two peaches had different structures and concents of cellulose andhemicellulose. Compared to fresh peaches, peaches storaged at18d and41d had less chainsof cellulose and hemicellulose with big width values, which showed that the cellulose and hemicellulose in peaches degraded during storage. For both cultivars, most of the chainwidths were between70.31nm to156.25nm for fresh peaches,70.31nm to101.56nm forpeaches storaged at middle stage, while for peaches storaged at last stage they were less than70.31nm. In contrast with8oC and15oC,2oC extended the degradation of cellulose andhemicellulose in peaches. The AFM analyzed that the CE chain widths of peaches werecomposed by23.44nm and35.16nm, and that of the HC chain widths were by17.58nm,23.44nm,31.25nm and35.16nm. The other values of widths could be obtained by addingthese basic units.