Chestnut Kernel Browning Factors And Control Methods

The factors that affect the chestnut kernel browning including tannin , moisture content ,PPO, POD, processing method and sterilization were studied in this article. Comparing the tannin content of different chestnut kernel parts and processing methods showed that higher tannin content led to deeper browning; Meanwhile three tannin extraction methods were compared and acetone-water (6:4) had the best effect. The tannin -reduction experiment proved that tannin did take part in the chestnut kernel browning. Tannin aggravated browning at alkali conditions. The determination of carbohydrate and free amino acid after and before processing showed that reducing sugar decreased markedly, while free amino acid, soluble sugars % sucrose, starch content changed a little. The relationship between water content and browning showed that drying chestnut at 50℃ for 60min would lead to deeper browning. In the enzyme browning, the PPO activity disappeared at 75℃,whereas POD activity at 100℃.The optimum pH of PPO was 7,while POD was 4. The sterilization temperature comparison showed that 115℃ had more browning effect than 100℃,especially for roasted chestnut, suggesting that high temperature had an important effect on chestnut browning. After sterilization, color-protecting and uncolor-protecting method resulted different color density, suggesting that appropriate browning inhibitors can inhibit the browning after high temperature sterilization. Finally, the design of "the five-factor quadratic regression orthogonal rotary method" was adopted to study the effect of five different browning inhibition factors: EDTA-2Na, NaHSO3, Vc, pH and dipping time. The dominant factor effect showed that Vc, pH were the main factors on the chestnut browning. NaHSOsand dipping time had the positive effect. The single factor effect showed that it was not evident for reducing chestnut browning to increase the concentration of EDTA-2Na and NaHSO3, while decreasing the concentration of Vc and pH had the evident positive effect. Interactive factor effect showed that the interactive effect between EDTA-2Na and dipping time was the most evident. The best control method was 0.15%EDTA-2Na, 0.4%NaHSO3, 0.1%Vc, pH 3.35, dipping time 5 hours, then sterilized at 115℃ for 30min.