Study On Enzymatic Browning Control Technology To Fresh-cut Sand Pears

Fresh-cut fruit and vegetable, characterized by fresh, nutritional and ready-to-eat, is a rising and popular product. But the mechanical processing browns the cutting surface which resulted in quality deterioration. In this paper, Chinese sand pear (Huanghua, Jinqiu) and Japanese sand pear (Niitaka, Shinseiki), represent-tative strains of sand pear(Pyrus pyrifolia)were used as experimental materials, to analyse the physiological situation difference in varieties of fresh-cut sand pears and the effect of different processing method on the color of pears.Based on those obtained results, optimum compound inhibitors for controlling browning was screened out then made an effect evaluation to provide theoretical basis and practical guidance for reducing browning of fresh-cut fruit sand pears.The main results showed as followings:1. Niitaka pear, Huanghua pear, Jinqiu pear and Shinseiki pear were used as experimental materials, to analyse the physiological situation difference in varieties of fresh-cut sand pears. The result indicated that browning of sand pear were affected by different complex factors. PPO and POD were the key enzymes resulting in browning. BD (browning degree) of four varieties of fresh-cut sand pears ranked from high to low as following:Shinseiki ranked first,and the Niitaka were second, Jinqiu and Huanghua ranked third and fourth respectively.2. Shinseiki were used as experimental materials, to study on the affected factors such as cutting way, storage temperature, chitosan concentration,fresh fixative composition, ect of BD. The result indicated that the effects of cross cut on BD was superior to slitting; the effects of cryopreservation (0℃to 10℃)on keeping the color of fresh-cut sand pear were superior to room temperature (25℃); in the chitosan concentration of 0.5%,1.0%,1.5% and 2%, the inhibitory effect of 1.5% chitosan concentration on BD was significant higher than others; the effect of fresh fixative on pears ranked from high to low as following:0.3% citric acid>0.5% ascorbic acid>0.1% mannitol.3. In multiple factors test of compound fresh fixative on inhibition of bro-wning, the effect of different compound on controlling browning of Shinseiki pear ranked from high to low as following:citric acid> mannitol>ascorbic acid> ascorbic acid X citric acid> citric acid X mannitol> ascorbic acid X mannitol; and obtaining the best formula of inhibition (0.3% citric acid+0.5% ascor bic acid+ 0.1% mannitol).4. Niitaka pear, Huanghua pear, Jinqiu pear and Shinseiki pear were used as experimental materials, to evaluate the effect of the optimum formula of inhibi-tion. During storage period, the index of BD value, respiratory intensity, activity of PPO and POD, isozyme of PPO, POD and SOD of optimum formula of inhibition of four varieties of fresh-cut sand pears were measure. The result indicated that compound inhibitors had small effect on respiratory intensity of varieties of fresh-cut sand pears;the compound inhibitor could keep sand pear cutting of the 4 varieties fresh within 6 day-stortage. The compound inhibitors could reduce the activity of PPO and POD, and enhance the activity of SOD on all varieties of sand pear; isozyme of PPO, POD and SOD showed that differ-rences existed among control and treated materials mainly in the number of zone, but the difference was not significant.