Comparison of different preharvest technologies to regulate and control storage quality of Dimocarpus longan fruit

Objective  To investigate the influence of fruit maturity at harvest, tree vigour and preharvest regulation on the storage performance and shelf life of Dimocarpus longan fruit.

Method  D. longan Lour. cv. Shixia fruits were used as experimental material. Three groups of single factor experiments were designed with fruit maturity, tree vigour and preharvest regulation as the experimental factors, and each factor had three levels. The harvested fruits were treated using SO₂-released paper and were stored at (5±1) ℃ for 50 days. We observed the good fruit rate after storage (STGFR), and the good fruit rate during shelf life (SFGFR) at (25±1) ℃. The storage performances of fruits with different preharvest treatments were compared.

Result  Fruits harvested at appropriate maturity (80%−85% maturity degree) had higher STGFR and SFGFR than those at full maturity (95%−100% maturity degree, CK) and over maturity, and the over matured fruits performed the worst. Both preharvest disease control and nutrition regulation treatments resulted in fruits with higher STGFR and SFGFR compared to CK with significant differences (P<0.01). Among them, disease control treatment performed the best with 93.26% STGFR, followed by nutrition regulation treatment (84.23%), and the worst was CK (67.71%). Among three types of trees with different vigor, fruits from strong tree had the best storability, followed by weak tree, and CK(medium tree) was the worst. Among all treatments, the fruit storability of disease control treatment was the best, with a SFGFR of 84.86% after four days on shelf, followed by strong tree, nutrition regulation and week tree treatments, with SFGFR of 63.23%, 56.14% and 51.12% respectively, and the worst was the over matured fruit (26.91%). The results of correlation analysis indicated that the content of total soluble solids in fruit pulp at harvest was significantly negatively correlated with the amount of SO₂ residue in pulp and mass loss rate during shelf life, but not correlated with storability.

Conclusion  During the fruit growth period of D. longan, performing disease control and nutrition regulation, keeping reasonable tree vigour with suitable fruit setting rate, and harvesting at appropriate maturity can help the fruit obtain better storability and longer shelf life.