Study On Browning Inhibition Techniques Of Fresh-cut Yam

Fresh-cut fruits and vegetables have characteristics of freshness, nutrition cleanness, health, safety and convenience and so on, which have been sold on the market in a higher proportion in developed countries. In China, develop- ment of these kinds of product will be a good trend for providing fresh fruits and vegetables obviously. Although development of fresh-cut fruits and vege -tables started later in China, there must be a great market in the future. Browning after cutting is the main issue affecting quality of some fresh-cut fruits and vegetables. This thesis studied the controlling techniques of fresh -cut yams and discussed the browning mechanism. The results showed that:1. Two respiration peaks occurred during storage of fresh-cut yams. Yam cultivar obviously influenced browning. Foshou yam is frangible, its respiration rate and PPO activity were higher than other three cultivars,"Hua","Niutui"and"Mao"yams. It obviously browned earlier.2. Post-cutting heat shock in hot water can obviously retard browning, decrease decay, and significantly improve visual quality of fresh-cut yams, but had no effect on inhibiting water loss. 45℃-10min was the suitable condition for heat shock treatment of fresh-cut yam. Fresh-cut Niutui yam treated with this condition browned later more than one time at 4℃and still had good quality after storage for 9days.3. Ethanol fuming can effectively control browning of fresh-cut yams; its efficacy was good enough for its being applied commercially. Fresh-cut Niutui yam fumed with 200ul/l ethanol still had good sensory quality after storage for 12 days and was better than control yams stored for only 6 days.4. After cutting, removing effluent juice was beneficial to reduce surface browning, water loss, and become mucous and improve total sensory quality. It also decreased the PAL activity. So, it is speculated that effluent juice con- tains signal which can change enzyme activity related to browning.5. Based on the fact that after fresh-cut yam was treated with heat shock, ethanol fuming and the effluent juice being removed, the browning extent was obviously decreased, increases of PAL activity was inhibited or delayed and the changes of PPO activity didn't show regular mode, it was concluded that PAL but not PPO plays important role in browning of fresh-cut yams..