Effects of different fresh-keeping transportation modes on quality of litchi fruit

Abstract: Litchi is special fruit in China. It is important and difficult to keep fresh for litchi during transportation after harvest because it matures in hot seasons and will deteriorate rapidly while stored and transported in normal atmospheric temperature. Foam box with ice, refrigeration, and controlled atmosphere are three main fresh-keeping transportation modes for litchi at present. In order to obtain the effects of different fresh-keeping transportation modes on the quality of litchi fruit, the experiments of these three fresh-keeping transportation modes for "Feizixiao" litchi were carried out based on fresh-keeping transportation platform for fruits and vegetables. The developed fresh-keeping transportation platform can adjust temperature, relative humidity and oxygen volume fraction automatically and intelligently according to initial parameters setting and real time feedback from container to create a suitable fresh-keeping environment for litchi. The main processing of the three experiments is conducted as follows. For the experiment of ice-added transportation in foam box, litchi was packaged with polyethylene bags and then put into foam boxes with appropriate crushed ice (mass proportion of ice to fruit was about 0.30) to maintain low temperature. While for the refrigerated transportation experiment, litchi was packaged with perforated polyethylene bags (aperture ratio was 5%) and then put into plastic baskets, keeping the container environment temperature of 3-5℃ and relative humidity of 90%-95%. The package type of the controlled atmosphere transportation experiment was the same as that of the refrigerated transportation experiment and the two experiments were at the same temperature and relative humidity in container, but the oxygen volume fraction should be set to 3%-5%. On this basis, the foam boxes or plastic baskets with packaged litchi were fixed on the vibration device workbench located in the container of fresh-keeping transportation platform, and set the vibration acceleration of 0.25 g (gravitational acceleration) corresponding to the vibration level of 70-80 km/h running on highway. The main fresh-keeping quality parameters of litchi were tested per 24 hours, mainly including mass loss rate, good fruit rate, browning index, total soluble solide content, titrable acidity, firmness of pulp, relative conductivity of pericarp and shelf life quality. Results indicated that the effects of three fresh-keeping transportation modes on the quality of litchi within 1 day of transportation time had no significant difference (p>0.05). However, the refrigerated transportation and controlled atmosphere transportation could effectively delay the quality decline of litchi along with the extension of the transportation time. The controlled atmosphere transportation could significantly delay the decline of pulp firmness, total soluble solids content, pericarp relative conductivity and shelf life quality (p<0.05) after 4 days of transportation compared with the other two transportation modes. It could be concluded that the three transportation modes were all suitable for the litchi quality keeping within 1 day of transportation period; and the refrigerated or controlled atmosphere transportation would be better for the litchi transportation lasting for 2-4 days; however, the controlled atmosphere transportation mode would be the most appropriate selection for the litchi transportation for more than 4 days. The research can provide a reference for the selection of fresh-keeping transportation mode for litchi fruit.