| Mulberry is sweet and tasty,with wealth nutritional and medicinal value,and is a fruit welcomed by consumers.However,mulberry is a delicate tissue fruit without skin wrapped and picked up in late spring and early summer harvest season,so it is vulnerable to external mechanical damage and infestation during picking and shipping process.The current study was limited in the changes of underlying quality and physiological indicators,and fruit softening autolysis mechanism was more from enzymatic angle,but from the perspective of non-enzymatic to study autolysis mulberry fruits influence has not been reported.In this experiment,the ‘big ten’mulberry fruits were selected as material,studied the effects of reactive oxygen species on postharvest mulberry fruit softening and cell wall autolysis,the main results were as follows:1.The effect of temperature on quality,cell wall degradation enzymes of mulberry during storage.10 ℃ storage temperature advanced appearance of activity peak,increased activities of cell wall hydrolase of mulberry fruit,and promoted autolysis of fruit cell walls,thus accelerating the mulberry fruit softening autolysis.Low storage temperature(0 ℃)maintained quality better such as soluble solids(TSS),titratable acidity(TA),color(L*,a*,b*),and delayed fruit hardness and weight decrease,while inhibited fruit autolysis and reduced the cell wall degrading enzymes activeties,like poly-galacturonic acid enzyme(PG),pectin esterase(PE),pectin lyase(PL),cellulase(Cx),etc.2.The effect of temperature on cell wall ultrastructure and cell wall polysaccharide composition and content of mulberry during storage.During storage,electron microscope showed that mulberry fruit cell deformated,cell contents becomed less or even disappeared,cell wall thinned,etc.0℃ storage temperature kept the shape and content of mulberrt fruit cell best compared of 5 ℃ and 10 ℃.0 ℃ storage temperature can significantly inhibit reduce of cell wall material,hemicellulose and cellulose content.Hemicellulose and water-soluble pectin respectively showed a significant positive correlation and negative correlation with autolyzed index.3.The effect of reactive oxygen species on the degradation of mulberry fruit cell wall polysaccharides in vitro.With total sugar and uronic acid as indicator,O2-.,H2O2 and.OH three active oxygen treatment were used in cell wall in vitro,the findings show that.OH significantly accelerated the the release of total sugar and uronic acid of the fruit cell walls in the 0.5mmol/L concentration conditioning.In this condition,theextracted water-soluble,ionic type,covalent binding of pectin polysaccharides total sugar and uronic acid content were significantly higher than the control,then accelerating the degree of hydrolysis of pectin in the cell wall.4.Impact of.OH on quality,active oxygen metabolism during storage in vivo.Reactive oxygen 0.5mmol/L.OH was the factor that influences fruit autolysis during storage which accelerated the drop of hardness,color,TSS and quality declined..OH accelerated hydrogen peroxide(H2O2),hydroxyl radical(.OH)and superoxide anion(O2-.)during storage,and inncreased levels of inhibition of antioxidant enzyme superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities.The conclusions showed that exogenous.OH accelerated the accumulation of free radicals,suppressed self-protection and repair of fruit,thus accelerating the destruction of cells.5.Impact of.OH on cell ultrastructure,cell wall polysaccharides and molecular weight during storage in vivo.Ultrastructure showed that 0.5mmol/L.OH accelerated the destruction of the cell structure of mulberry fruit,hollowed cells,stimulated cell vesicles and increased self-accelerating dissolution,while accelerating the degradation of cell wall and increasing the release amout of total sugar and uronic acid of watersoluble pectin.In addition,.OH accelerated the hydrolysis of pectin substances polysaccharide and degradation of macromolecules pectin into small molecules of monosaccharides or oligosaccharides. |
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