Research On The Degradation Characteristic Of Cell Wall Polysaccharides During Peach Fruit Softening

Peach fruits [Prumus persica (L.) Batsch, cv. Yuhuasanhao] were used as materials to study the degradation character of cell wall polysaccharides during on-tree ripening and postharvest storage, the effects of endogenetic ethylene and cell wall degradation enzymes on peach fruit softening.(1) The modifications of ethylene production, firmness and TSS content were determined in present study. The results showed that, the maximal ethylene productions of peach fruit were posterior to the rapidly change of fruit texture, both during on-tree ripening and postharvest 20℃storage. But the changes of texture were not showed when ethylene production was inhibited during 5℃storage. These suggested that ethylene might have significant effort on peach fruit softening, but it was not the factor of start-up of softening, just a factor of promotion of softening.(2) The results of the analysis of cell wall polysaccharides showed an increase of CDTA-1 pectin, decreases of CDTA-2, Na₂CO₃-1, Na₂CO₃-2 pectic and CWM-residue hemicellulosic polysaccharides. The decreases of KOH-1 and KOH-2 hemicellulosic polysaccharides were showed during peach fruit on-tree ripening, and programmed fruit softening, but the decreases of the content of hemicellulosic polysaccharides were not important factors of fruit softening during postharvest storage.(3) The results of the analysis of sugar compositions of cell wall polysaccharides determined by gas chromatogram showed that, pectic polysaccharides depolymerized, the pectic main chains that riched in galacturonic acid took rupture along with the degradation of galacturonic acid residues and the loss of arabinosyl and galactosyl residues from pectic side chains. The loss of arabinosyl and galactosyl residues also showed in cellulosic polysaccharide. But the loss of neutral sugars in hemicellulosic polysaccharides had significant effect on peach fruit softening during on-tree ripening, but seemed to have nothing with flesh softening during postharvest storage.(4) The analysis of the changes of the activities of polygalacturonase, pectin...