Effect of Different Pre-Cooling Methods on the Quality of Litchi During Cold Storage

Pre-cooling can rapidly reduce the respiration intensity of fruit, helping extend its preservation period. This study investigates the effects of forced-air cooling with package treatment on fruit cooling and subsequent quality during storage. Moreover, a comparison was made between forced-air cooling and hydro-cooling in terms of fruit quality. Specifically, ‘Guiwei’ litchi fruit was treated with forced-air cooling at air velocities of 3, 6, and 10 m/s and hydro-cooling (5 °C), followed by storage at 3–5 °C for 18 days. Changes in cooling efficiency, pericarp moisture content, color, fruit firmness, weight loss, total soluble solids (TSS), and titratable acidity (TA) were monitored. The temperature of the forced-air-treated fruit first decreases faster and then slows down as the air velocity increases from 3 m/s to 10 m/s. Compared to forced-air cooling, hydro-cooling-treated fruit maintained better pericarp color, higher cooling rate, pericarp moisture content, and fruit firmness, but presented a lower total soluble solids (TSS) content, with no significant difference in titratable acidity (TA). The weight loss and aerobic respiratory depletion positively correlate with total soluble solid content and texture softening of litchi. The results provide a comprehensive reference for the selection of pre-cooling methods and the improvement of the postharvest industry.