Study On Quality Changes And Firmness Prediction Model Of Loquat Fruit After Harvest

Loquat fruit (Eriobotrya japonica Lindl), native to Southern of china, is famous for its soft, juicy taste and popular with consumers. Loquat includes two kinds:red and white, red ones, such as "Jiefangzhong", "Zaozhong", "Dawuxing", etc; white ones, such as "Guanyu", "Baiyu", "Qingzhong", etc. The white loquat is thinner and sweeter than the red one, but prone to be injured. The harvest season is hot and rainy, unsuitable for storage and transportation. And they are susceptible to decay, mechanical damage and nutritional loss. Low temperature storage is commonly used to inhibit fruit decay and extend postharvest life, but it increases the flesh leatheriness, such as firmness increase, juiceless pulp and adhesion of peel to the flesh. With rapid development in south of china, the quality monitoring of loquat fruit has become more important. In this paper, we studied the antioxidant activity of "Jiefangzhong" loquat at different temperature after harvest, also with flesh leatheriness of "Jiefangzhong" loquat at different temperatures. Based on the main quality (firmness, ethanol content) changes, the prediction models of "Jiefangzhong" loquat were built. The results were as follows:(1) The antioxidant activity of "Jiefangzhong" loquat fruit includes non-enzymatic one and enzymatic one. DPPH scavenging and reducing power which pretended the total antioxidant activity were high, all of them declined during storage, especially at high temperature. About non-enzymatic one, loquat fruit contained more antioxidant substances, appearing in total phenol and total flavonoids. At enzymatic one, SOD, CAT and APX cooperated with cleaning up O2- and H2O2. The activity of SOD, CAT and APX declined, low temperature put off the speed. O2- and H2O2 contents increased during storage, and did faster at higher temperature.(2) "Jiefangzhong" loquat fruit appeared flesh leatheriness at different temperatures, showing in firmness increasing and juice rate dropping. PAL and POD activity are important lignin synthesis-related enzymes, this experiment also showed that:PAL, POD activity was related to lignin content. Low temperature 2℃, subjected to chilling injury, there were disorders of reactive oxygen species metabolism and strong cell membrane fatty acid metabolism, undermining the integrity of the cell membrane. PAL, POD and PPO helpt the lignin content and firmness increase. Experiments also showed that at room temperature 22℃, maybe due to a shorter storage, tissue senescence, dehydration and firmness grew fast, and the mechanism is not clear now; in middle temperature 12℃, it increased slowly. PG activity of loquat fruit grew firstly, and then dropped. Water soluble pectin content declined, and protopectin content increased during storage, which partly made for firmness growing. About physiology, the respiratory rate dropped during storage, especially in low temperature 2℃. ADH activity reflected the ability to produce ethanol content of loquat fruit. ADH activity grew gradually, which helpt ethanol content increasing.(3) With the development of nondestructive testing technology of agricultural products, kinetics and model forecasts of agricultural products during storage are putting on the agenda, now the research of loquat fruit is little, so we studied the main quality changes of loquat fruit to establish the predictive models, and it was convenient for quality monitoring. "Jiefangzhong" loquat fruit were the materials which were stored at different temperatures. We analyzed the datas of quality changes, did regression fitting and model validation, and concluded results as follows:in the firmness model about time and temperature, R2=0.961, RE=0.0418, it showed that the forecasting accuracy reached a very significant level;In ethanol model about time and temperature, R2=0.96, RE=0.0485. And in the firmness model about ethanol content and temperature, R2=0.931, RE=0.102, it had a certain prediction significance. The relative error of shelf-life prediction model of loquat fruit at 293.15K-298.15K (20-25℃) were less than 10%, so the shelf-life prediction model could predict the quality of loquat fruit reliably and quickly. In all, the study had provided a theoretical basis for the non-destructive detection of loquat fruit during storage and transportation.