Effect Of Pre-temperature Treatments On Cell Wall Degradation In Strawberry Fruit

As a typical berry, strawberry (Fragaria spp.) fruit is easily suffered from decay after harvest, which reduces its nutrient and commercial values. The improvement of preservation effect in post-harvest strawberry storage is a major issue for urgent solution in its production. As a innocuity, non-pollyted and easy manipulate metord, pre-tempreture treatment is a physices treatment which could accord with standard of green fruit. Recent years, the industry of strawberry at Chongqing, Sichuan and other places picked up strawberry in advance in order to delay the shelf life and decreace the cost of it. Some studies showed that picking up strawberry at appropriate maturity could improve the quality of it during storage and shelf. The influences of pre-temperature treatments on the cell wall degradation, the activity of cell wall catabolic enzyme and the preservation effect were investigated in the thesis, based on the 'darselect' strawberries of different ripening degrees as research materials. Also the quality index and physiologic and biochemical properties, such as changes of cellulose, pectin, cellulase, pectincase and polysaccharide hydrolase in strawberry fruit with pre-temperature treatments were also studied in this paper.After being harvested, strawberries (30%, 50%, 80%, and 100% in red) were primarily and respectively subjected to 15min heat-treated at 45℃and 30min cool-treated at 5℃in an air oven. After those treatments, the fruit were refrigerated at 5℃for 20 days. Decay rates, quality properties, contents of cell wall components and activity of related enzymes were all under the influences of the cool and heat treatments.The effects of pre-temperature treatments on the fresh preservation of strawberry fruit were studied. The results showed that the decay rate of the low maturity fruit (30% and 50% in red) was lower than the high maturity fruit(80% and 100% in red). The storage time of the low maturity fruit could be delayed because the pre-heat treatments could obviously inhibit the increase of decay rate. The results of the water loss rate analysis showed that the difference of water loss rate between the fruit with pre-cool treatment were not significant, but it was obviously that the water loss rate of the low maturity fruit with pre-heat treatments is high than others. The water loss rate of low maturity fruit with pre-heat treatments was lower than which with pre-cool treatments. The pre-heat treatment promoted the decrease of ascorbic acid content during the earlier stage of cool storage, however, ascorbic acid content in all of the fruit with pre-cool treatment was higher than others. Both pre-heat and pre-cool treatments could inhibit the decrease of soluble sugar and titrable acidity contents, and both of the results were not significant difference. Pre-heat treatments could be conduced to improve the flavor of fruit at the bigining of storage. However, the quality of the 100% maturity fruit with pre-cool treatment is the best during the whole process of storage.Cellulose contents decreased gradually with the maturity of strawberry fruit, but the total pectin contents was not changed obviously. Pre-heat treatment could obviously inhibit the degradation of cellulose in the low maturity fruit. Pre-heat treatment could inhibit the increase of the water-soluble pectin, especially to the high maturity fruit. The pre-heat treatment could obviously decrease cellulose activity in high maturity fruit at the early stage of fruit storage. It was not different between the effect of pre-heat treatment and pre-cool treatment to pectin methylesterase, which was correlated to increase of water-soluble pectin but not the determinants of it. Polygalacruronase activity was significant inhibited under pre-cool treatments.β-galactosidase andα-mannosidase activities were strongly inhibited after pre-heat treatment. The result indicated that there was a significantly positive correlation existed between them and the fruit decay. They play important roles during the stage of fruit decay. For that, pre-heat treatment decreases the decay of fruit.