Study on water loss control of postharvest ‘Sweetspring’ tangelo fruits

Abstract:【Objective】The quality of‘Sweetspring’tangelo (Citrus reticulata Blanco × C. grandis Osb.‘Sweetspring’) is good, but it is easy to lose water and then becomes granulation under conven-tional storage (packaging) conditions, which seriously affects the quality and economic benefits of‘Tianchun’tangelo. A comprehensive preservation method, which can effectively reduce the granula-tion of‘Sweetspring’tangelo and elongate its storage time, was established by controlling the water loss of‘Sweetspring’tangelo.【Methods】‘Sweetspring’tangelo was soaked in 2% sodium bicarbonate solution for 3 minutes as pretreatment after it was picked, then removed and dried naturally. The follow-ing 4 treatments were set up. (1) The tangelos were soaked respectively in 0 ℃ ice water mixture for 5,10, 15 and 20 min, and stored at room temperature after natural air drying. (2) The fruits were soaked in 0.1%, 0.2%, 0.4% and 1% aqueous solution of chitin for 20 min, and stored at room temperature after natural air drying. (3) The fruits were individually packaged in the foil-type plastic bag with a thickness of 0.007, 0.01, 0.02 and 0.04 mm. (4) The fruits were stored at different temperatures of 6, 8, 10 ℃ and room temperature for 120 days. The weight loss rate in each treatment was determined regularly. The appearance evaluation, juice cell granulation index and weight loss rate were used as the indexes to evaluate the effect on water loss control. On the basis of single factor experiment, a L18(35) orthogonal test was conducted to control the occurrence of water loss and reduce the degree of juice cell granulation.【Results】The fruits were sterilized with 2% sodium bicarbonate solution after harvested. The weigh  loss rate of the fruit was significantly lower than that of the control. Fresh weight loss rate of the fruit was recorded on 30th, 60th, 90th and 120th days. The results showed that the weight loss rate of the treated fruit was significantly lower than that of the control (p < 0.05). The fruits were chilled in 0 ℃ ice water mixture for 5 min, 10 min, 15 min or 20 min and the weight loss rate was kept within 10% during storage; When fruits were coated with chitin at concentrations of 0.1%, 0.2%, 0.4% or 1%, the higher the concentration of chitin, the better the effect on controlling water loss. The average weight loss rate was 6.23% and the weight loss rate of the control group was 14.6%, which was 53.3% lower than that of the control. The results showed that water evaporation of‘Sweetspring’tangelo fruit could be inhibited by water solution containing chitin for 10 min, 20 min and 30 min, but there was no signifi-cant difference in water loss rate among three treatments; when fruits were packed in foil-type plastic bags at a thickness of 0.007 mm, 0.01 mm, 0.02 mm or 0.04 mm, it can effectively inhibit water transpi- ration, and the average weight loss rate of each treatment was 8.4%; When fruits were stored at low tem-peratures of 6 ℃, 8 ℃ or 10 ℃, it can also control the water loss and freshness of‘Sweetspring’tange-lo. However, during the whole storage period, the weight loss rate of‘Sweetspring’tangelo fruits in-creased slowly, and could be controlled within 10% by 120 days.【Conclusion】Cold shocking, chitin coating, packaging and cold storing can effectively reduce the weight loss rate of‘Tianchun’tangelo.Based on the results of the single factor experiment, the L18(35) orthogonal test was carried out. The bestscheme to control the occurrence of water loss and reduce the degree of juice granulation was cold-shocking the tangelo fruits for 15 min, coating them with 0.4% chitin solution (10 min), packaging them with 0.04 mm foil-type plastic bags and storing below 10 ℃. This method is not only efficient and convenient, but also low-cost, safe and environment-friendly. Therefore, it is a promising preservation method.