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Between internal browning and the changes of TNG17 pineapple fruit under low temperature storage

2019-11-22

Author: Yuan-Kai Tu, Taiwan Agricultural Research Institute, Council of Agriculture, Executive Yuan

The shelf life of pineapple can be extended by low temperature storage. However, the occurrence of fruit internal browning due to low temperature storage may lead to loss of market value. The subject of this study is to analysis the variation in physiological properties and internal browning of pineapple after low-temperature storage, and the important variables (physiological index) were selected by multiple regression analysis. The result showed that the internal browning rate of pineapple fruit was 0 % in the control group and those stored at room temperature for 5 days. The internal browning rate of fruit that stored at 7.5℃ for 3 weeks or 4 weeks were 13.6% or 26.8%, respectively. After stored at 7.5℃ for 3 weeks or 4 weeks, fruits were storage at room temperature for another 5 days and the internal browning rate of fruits increased to 34.9% or 46.7%, respectively. The results revealed the longer time of storage at low temperature, then more severe internal browning will be observed.

Fig. 1. Estimation of the internal browning percentage by ImageJ software.Fig. 1. Estimation of the internal browning percentage by ImageJ software.

The relationship between the changes of fruit quality and enzyme activities was modeled by multiple regression analysis. The result showed that sucrose and ascorbic acid content in the juice decreased significantly after low temperature storage, while the titratable acid and glucose content increased significantly. The respiration and biological metabolism of fruit could promote the degradation of sucrose and ascorbic acid. The result showed that the changes of sucrose and glucose content after 3 weeks at 7.5℃+5 days at room temperature and 4 weeks at 7.5℃+5 days at room temperature were more servere than after 3 weeks at 7.5℃ and 4 weeks at 7.5℃. The internal browning symptom of chilling injury was less obvious during low temperature storage and turned to be dramatically apparent after stored for another 5 days at room temperature. The activity of polyphenol oxidase increased during the progress of low temperature storage. Similar to the changes of glucose content, the changes of enzyme activity was more significant at 3 weeks at 7.5℃+5 days at room temperature and 4 weeks at 7.5℃+5 days at room temperature than after 3 weeks at 7.5℃ and 4 weeks at 7.5℃. In conclusion, sucrose, glucose, ascorbic acid content and polyphenol oxidase activity could be used as potential physiological index of internal browning for pineapple fruit.

Table 1. Results of the MLR (multiple regression) analysis by utilizing physiological parameters and extent of internal browning as explanatory and response variables, respectively.Table 1. Results of the MLR (multiple regression) analysis by utilizing physiological parameters and extent of internal browning as explanatory and response variables, respectively.
Fig. 2. Scatter plot of the fruit physiological parameters under various storage condition.Fig. 2. Scatter plot of the fruit physiological parameters under various storage condition.
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