| Grape berries are soft, juicy and full of such various nutrients as sugar, organic acid, protein, minerals, vitamins and so on, which is of high value of nutrition and diet therapy. Therefore, grapes are widely used for not only fresh eating but also processing. However, the seasonality of grape harvest is intensive in the country, the fresh-keeping technology should be developed to supply table grapes to the market all the year around. The fruit is among the berries which is most unendurable of storing, for the percentage of its water content is high, which tends to cause dry stems, threshing, shrivel, browning, dehiscent fruit, decay during the storage period of postharvest, and the quality would be terribly influenced. For this reason, it is significant to study the change of each quality of grapes during the period of fresh-keeping storage.The materials in the test are Purple and Fragrant Seedless, Centennial Seedless, Red Globe, all of which are mainly cultivated table grape varieties in Shihezi area of Xinjiang. Based on the study of the grape storage parameters, the test of fresh-keeping are experimented with SO2under the condition of temperature of1℃below zero and90m～95%relative humidity in the cold storage. The change rules of each quality index in three grape varieties during the postharvest storage are studied, and the freezing point is determined. The main quality index in different grape varieties is tested from the grape warehousing, including the titratable acid, soluble solids, fruit hardness, fruit of Vc, the weightlessness rate, SO2residues, decay rate, the grain percentage, fruit browning index, respiratory rate, fruit chlorophyll, malondialdehyde content in pulp, comprehensive sensory score, etc. The results are as follows:1.The freezing point of three grape varieties are-2℃in Red Globe and-3℃in Centennial Seedless and-3℃Purple and Fragrant Seedless in order.2. The soluble solids, titratable acid, Vitamin C, fruit hardness and comprehensive sensory scores of three grape varieties are on a declining curve during storage. The decline of soluble solids, titratable acid, comprehensive sensory score are relatively small, and Vitamin C and fruit hardness are large. Each index of Red Globe is decreased significantly lower than the other two varieties. The comprehensive sensory in Red Globe is best.3. The respiration of three grape varieties show an the declined trend in the earlier stage during storage, respiratory intensity is smoothly from20to60days, but it gradually began to rise after60days. Respiratory intensity is highest in Centennial Seedless, the second in Purple and Fragrant Seedless, lowest in the middle in Red Globe.4. The phenomenon of SO2damage is showed in Red Globe first during storage stage. The sensitivity on SO2in Centennial Seedless is stronger than Purple and Fragrant Seedless and is weaker than Red Globe.5. Stem browning index in three grape varieties show a rising trend during storage stage. That is consistent with the result of the decline trend on stem chlorophyll content. The stem browning is easier in Purple and Fragrant Seedless than Centennial Seedless, and not easy in Red Globe.6. Centennial Seedless shatter a lot, but Purple and Fragrant Seedless and Red Globe are rarely shattered during the period of storage.7. Cluster weightlessness rate show a rising trend during the storage stage, it is highest in Red Globe, it is minimum in Purple and Fragrant Seedless.The experimental results show that the nutrients of three grape varieties are gradually consumed as the extension of storage time, causing a decline on fruit quality. Meanwhile, storability also exists certain differences among three varieties. The variety of best storability is Red Globe. The amount of SO2must be applied in control during the period of storage. Centennial Seedless is very difficult to store, the main problem is that the berries are easy to shatter during postharvest storage... |
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