“Foam container + ice pack” is a common packaging form for e-commerce logistics of litchis. However, there are numerous factors affecting the temperature variation under this logistics mode, making it difficult to control the packaging temperature and litchi quality during the e-commerce logistics process. In order to explore the impact of the packaging scheme on the packaging environment temperature and the quality variation in litchis during the “foam container + ice pack” logistics process, this paper takes the number of ice packs, the terminal pre-cooling temperature of litchis, the weight of litchis, and whether to use aluminum foil insulating film as variable factors to study the impact rules of these factors on the EPS (Expanded Polystyrene) foam container environment temperature, the total number of fruit pericarp, and the marketable fruit rate. The experimental results show the following trends: the terminal pre-cooling temperature has a significant impact on the daily average temperature of the fruit layer; the packaging environment temperature of the 15 °C pre-cooling group on the first day and the second day is 5.00 °C and 2.78 °C higher than that of the 5 °C pre-cooling experimental group, respectively. Moreover, under this treatment, the growth rate of fruit pericarp fungi is relatively fast, which could reach 3.87 Lg (CFU/g) on the second day. Increasing the amount of litchis could maintain a lower temperature environment, but it will cause the relative conductivity increasing 4.12% compared with the groups with no weight increasing. Increasing the number of ice packs could significantly reduce the decline rate of fruit soluble solids in the first two days. The research results of this paper are expected to provide a certain reference for the quality assurance logistics and the formulation of long-distance transportation strategies for perishable agricultural products.

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.

To enhance the precision of Discrete Element Method (DEM) simulation parameters for the grading of mechanically harvested fresh tea leaves, this study systematically measured the intrinsic physical and basic contact parameters of the Yinghong No. 9 cultivar. Addressing the distinction between primary and secondary contact interfaces during roller screening, the extreme boundary validation method was first employed to determine simplified fixed values for the contact parameters of the secondary component. Based on the measured physical angle of repose of 36.3°, Plackett–Burman screening, steepest ascent, and Box–Behnken tests were conducted sequentially to construct and optimize a second-order regression model relating significant parameters to the angle of repose. The results indicated that the static friction coefficient between tea leaves (0.723), the rolling friction coefficient between tea leaves (0.031), and the static friction coefficient between tea leaves and the PVC roller (0.547) were the key parameters affecting the angle of repose. Verification tests demonstrated that the simulated static angle of repose was 36.9° against the measured 36.3°, yielding a relative error of 1.65%. The simulated dynamic angle of repose in the rotating drum was 39.8° compared to the physical 38.3°, representing a relative error of 3.92%, and the errors in screening efficiency on the grading bench were all less than 5%. These results indicate that the calibrated parameters accurately characterize the material properties of mechanically harvested tea leaves, providing a reliable theoretical foundation for the structural optimization of grading equipment.