Effect of Pre-Harvest Calcium Treatment on Post-Harvest Fruit Quality of Nanfeng Tangerine

To investigate the effect of calcium (Ca) application on post-harvest fruit quality in Nanfeng tangerines, this study sprayed three calcium fertilizers (Calbit, Larry 8 Calcium, and Suspended Calcium) before harvesting. The fruit quality was assessed over a storage period of 0–60 d at a controlled room temperature of 20 ± 5 °C. The evaluation methods included principal component analysis (PCA) and linearly weighted summation. Pre-harvest calcium treatments increased the fruit calcium content and maintained higher firmness and shear. Compared to the control group, fruits treated with Calbit exhibited decreased levels of decay, weight loss, and respiration rates. Additionally, they demonstrated higher values of L*, b*, C*, and H° and lower values of a* and CCI. Moreover, the Larry 8 Calcium and Calbit treatments increased the levels of soluble solids, total soluble sugars, titratable acids, and VC content in the fruit. They accelerated the decomposition of tartaric, oxalic, and citric acids in the pulp, promoting the accumulation of sucrose and glucose. PCA and comprehensive evaluation scores indicated that the comprehensive scores assessing the storage quality of Nanfeng tangerine fruits treated with pre-harvest Larry 8 Calcium and Calbit were higher than those of the control group. The highest composite quality scores for Calbit-treated fruits were observed at 40 and 60 d, and the highest scores for Larry 8 Calcium were recorded at other intervals. These findings suggest that pre-harvest calcium application improved the post-harvest fruit quality of Nanfeng tangerines, with Larry 8 Calcium and Calbit emerging as favorable options.