Studies On The Quality Changes Of Huanghua Pears During Transport And Storage

A complete logistic process of postharvest fruit includes transport, storage and sale. Reducing postharvest fruit loss during the process of logistics is one of main issues concerned by the agricultural trade in the world. China is one of the largest fruit producers, but the processing technology for postharvest fruit lagged behind, so that fruit loss is very serious in the process of logistics. Transport vibration is one of the main reasons for fruit loss in the process of logistics. In this study, based on Huanghua pears which are widely planted in our country, the research was focused on exigent problems about discoloration, softening, and water loss, and investigating the influences of transport vibration on the quality of Huanghua pears. Different kinds of packing were also used to alleviate vibration damage to Huanghua pears. Meanwhile, effects of different kinds of coating on post-harvest quality characteristics of Huanghua pears during storage were analyzed to seek after the rule of using edible coating to preserving pears. The postharvest quality of Huanghua pears were detected using MRI, and establishing a mathematical model for testing the firmness of Huanghua pears during storage, which contributed to improve the quality control of Huanghua pears during the process of logistics. In this paper, the main aspects of our researches are as follows:(1) Testing the vibration during the transport of Huanghua pears and the mechanical damage to the pears; studying the mechanism of effects of transport vibration on the quality of Huanghua pears on sale.The peak of power density spectrum of a truck with leaf-spring suspensions were in the range 2.5-4Hz, and a second but lower peak between 15 and 40 Hz, which is independent of the speed of the truck, the road conditions and the stacked positions in the truck.The current research showed that the vibration levels of the truck floor were different, and levels of the rear position were higher than levels of the front floor along the entire route which resulted in heavier damage to Huanghua pears loaded in the rear top RPC than damage to the fruit in the front top RPC (p < 0.05). Additionally, different levels of mechanical damage to pears caused by different levels of transport vibration affected the leakage of skin cells and cell wall decomposition in tissue, which further influenced changes in appearance and firmness of the fruit and subsequent commercialization after transport. Given these data, we recommend the use of shock absorption treatments to reduce mechanical damage to pears loaded at the rear position of the truck floor during transport and distribution.(2) Comparing the effects of protection of different packages on Huanghua pears during transport; and comparing the influences of different packages on the quality of Huanghua pears during room temperature storage after transportation to select a more appropriate package for these fruit.Different cushioning materials have different protection effects for Huanghua pears. The current study demonstrated that foam-net packages reduced the transport vibration levels of pears more effectively than paper-wrap packages (p < 0.05). The use of foam-net packages also reduced the mechanical damage to individual pears during transport, compared with paper-wrap packages (p < 0.05). Different levels of vibration damage to pears influenced enzymatic activity, which further affected the changes in pear firmness and subsequent commercialization after transport. Given these data, we recommend the use of foam-net cushioning materials to maintain Huanghua pears quality during transport and distribution. Paper-wrap packages also played a good job for protection during transport. However, Poor ventilation of paper-wrap packages made it easier for pears to soften during storage. Moreover, the methods used in this experiment can be used to compare the effects of different packaging materials on a kind of particular fruit.(3) Different edible packaging films were used for coating Huanghua pears. Compare the protective effects on pears of reducing friction injury (The main form of damage to fruit during transport). And study the law of different edible packaging films influencing pear quality during low temperature storage after transport.During the transport and storage process, Huanghua pears are easily damaged by friction. In this study, the edible packaging films can reduce the pear discoloration caused by friction, but there are differences between the effects of the three coatings. Compared to other coating materials, shellac coating can reduce friction damage more effectively, and followed by caboxymethyl chitosan coating. Because of the relatively smaller water loss, as well as lower polyphenol oxidase activity and polyphenol content, and maintaining a relatively higher peroxidase activity and stabilization of the membrane of epidermal cells, as well as higher anthocyanin and flavonoids, in the same external friction conditions, shellac packaging films can more effectively reduce the friction discoloration. At the same time, shellac coating has good characteristics of water keeping and retarding the decomposition of chlorophyll, maintaining better pear brightness and delaying the color changes of stored pears.Compared with the uncoated Huanghua pears, all the coated pears showed significantly reduced respiration rates and weight loss (p < 0.05) and delayed changes in the ripening parameters such as permeability of the cell membrane, TPA, SSC, TA and ascorbic acid levels, and taste (p < 0.05), restraining the changes in the activities of PE, PG, POD and cellulase. However, Semperfresh coating was less effective in reducing the changes in cell membrane permeability than shellac coating, and CMC coating was less effective in decreasing weight loss than shellac coating. In comparison with Semperfresh coating and CMC coating, shellac coating was more effective in inhibiting metabolism and maintaining the quality of Huanghua pears during storage, which was also supported by the MR images. On the basis of these data, we recommend the use of shellac coating to maintain the quality of Huanghua pears during long-term cold storage.(4) Magnetic resonance imaging was used to detect pear quality at the end of the cold storage period. Based on texture analysis of magnetic resonance images and artificial neural network (ANN), we established the model which can detect the firmness changes in Huanghua pears in the conditions of low temperature storage and controlled atmospheric conditions.This study used magnetic resonance imaging to detect the pears treated with different kinds of edible packaging films, finding that shellac coating and carboxymethyl chitosan are more effective in reducing free water content in pears at the end of the cold storage period. In the present study, texture analysis (TA) of magnetic resonance images was applied to predict the firmness of Huanghua pears during storage using an ANN. Seven co-occurrence matrix-derived TA parameters and one run-length matrix TA parameter significantly correlated with firmness were considered as inputs to the ANN. Several ANN models were evaluated when developing the optimal topology. The optimal ANN model consisted of one hidden layer with 17 neurons in the hidden layer. This model was able to detect the firmness of the pears with a mean absolute error (MAE) of 0.539 N and R =0.969. Our data showed the potential of TA parameters of MR images combined with ANN for investigating the internal quality characteristics of fruits during storage. Further, the successful application of ANN combined with TA parameters in determining the firmness of pears provides MRI more insight into the development of physiological changes in fruit and vegetables.