Studies On The Physiological And Biochemical Characteristics Of Korla Fragrant Pear During The Periods Of Development And Storage

Korla pear was used as the research object to study the characteristics of physiological and biochemical changes during the fruit developmental period and storage period, for doing deeply research on the physiological and biochemical mechanism of fruit ripening and senescence of Korla pear and improving fruit quality to provide research basis for the product development of related antistaling agent. The main results were as follows:1. The growth period of Korla pear was about 135 days, and the changes of its fruit development displayed an “S” shape, exhibiting the pattern “slow-quick-slow”. 60 to 120 days after the fruit setting were the rapid growth period of pear fruit. In maturity, fruit firmness decreased to 6.03 kg/cm2; Both the soluble solids content and the total sugar content showed the rising trends and SSC went up to 13.7%; The total sugar content increased significantly in the late development stage; The total acid content decreased rapidly in the early stage of fruit development, and went down to 0.05% or so when the fruit was ripe; The content of Vc in the fruit went up to the highest level of 16.14 mg/100 g at about 45 days after the fruit setting, and then showed a decreasing trend with the maturity of fruit; The protein content rapidly rose in the early stage of fruit development, and fell a little when the fruit stepped into the rapid growth period, subsequently experienced a trend of gradual rising with the maturity of fruit.2. The respiratory intensity of Korla pear decreased, and Korla pear fruit had no breathing bounce during the fruit developmental period; The cell membrane permeability increased gradually; During the fruit developmental period, rises of SOD, POD and CAT activity had positive effects against membrane damage, and the activity of SOD was the most important.3. During the fruit developmental period, the content of cell wall decreased to 1/5 of the original content; The water soluble pectin content and ionic pectin content increased, while the covalent pectin content increased first, then showed a downward trend when the fruit was close to maturity; The contents of cellulose and hemicellulose firstly rose and then fell, reducing to almost 1/3 of the maximum value when the fruit was ripe; Pectinase activity showed a rising trend in the fruit developmental period, and in maturity, the activity increased 3.5 times more than the original, while cellulase showed a rising trend in the fruit developmental period.4. The increases of cell number and volume were important factors to determine the size of the pear; The changes of super microstructure in fruit development period showd: in fruit setting period, the cell wall had an integrated structure and an even thickness, and the organelle was also intact; With the development and maturity of the fruit pear, the cell walls became thinner and some even disappeared, and the bright-dark-bright structure of middle lamella disappeared as well.5. During storage, the fruit firmness of Korla pear gradually decreased, and its sugar, acid, Vc, protein, and other nutrient and flavor were consumed, resulting in the gradual deterioration of its quality; The pre-treatments had positive effects on maintaining fruit quality and delaying the aging.6. Korla pear belonged to this kind of fruit with a respiratory bounce, and had two respiratory peaks in storage period; the time of the respiratory peaks occurring was in consistent with the time of cell membrane permeability increasing and harmful substances accumulating, and the change rule of protective enzymes and the change rule of harmful substances accumulating were in conformity; the pre-treatments delayed the appearance of respiratory peaks, and reduced lipid peroxidation, which helped to delay the speed of fruit senescence.7. During storage, the content of cell wall substances of Korla pear showed a downward trend; With the rising of pectinase and cellulase activity, the water soluble pectin content and the ionic pectin content increased, while the covalent pectin content declined, and the cellulose and hemicellulose contents also decreased; The pre-treatments had inhibitory effect on the pectinase and cellulase activity, and delayed the decreasing of the content of cell wall substances.