Influence of Storage Conditions on Physico-Chemical and Biochemical of Two Tangerine Cultivars

The influences of on-tree, off-tree and cold storage on physico-chemical and biochemical were studied and quite similar between thetwo tangerine cultivars, ‘Sai Num Phueng’ and ‘See Thong’. In both cultivars, the percentage of weight loss increased and the moisture content of the peel (%) decreased at higher temperature and longer duration. Low temperature storage at 5°C reduced the losses of fruit weight and moisture content of the peel and preserved the external quality better than 25°C storage. During on-tree and off-tree storage at 25 and 5°C, peel chlorophyll content decreased and peel carotenoid content increased. Titratable acidity (TA), citric acid, isocitric acid and vitamin C contents decreased and juice pH increased. Malic acid content stayed relatively constant. Total soluble solids (TSS), TSS/TA ratio and sucrose content continually increased. Glucose and fructose contents slightly increased. The peel chlorophyll content, TA and citric acid content decreased faster during storage on-tree than at 25°C. The peel carotenoid, TSS and sucrose contents increased greater during storage on-tree than at 25°C. The delayed declining of peel chlorophyll, TA, and citric acid contents and the slow increases of the peel carotenoid, TSS and sucrose contents were observed at 5°C storage in comparison to 25°C. The activities of mitochondrial citrate synthase, cytosolic aconitase and cytosolic NADP-isocitrate dehydrogenase (NADP-IDH) were lower and decreased faster during storage at 25°C in comparison to storage on-tree. The activities of these enzymes, which related to citric acid metabolism, were slowed down which resulted in delaying the decrease of citric acid content during storage at 5°C in comparison to 25°C.