Study On The Enzymatic Browning Mechanism And The Control Of Fresh-cut Rfuits And Vegetables

Fresh-cut fruits and vegetables are the ready-to-eat products that processed by washing,peeling, cutting or slicing, trimming, grading and packaging. However, fresh-cut fruits andvegetables undergo substantial mechanical injuries caused by the minimal processing. Thesedamages can lead to the enzymatic browning very easily and induce a series of negativeeffects including appearance quality and nutrition component of the fresh-cut product.Moreover, enzymatic browning has become significant physiological factor of fresh-cut fruitsand vegetables. These enzymatic browning induced not only in the cutting surface, but alsofound in the distant cell tissue from cutting site. The research on the mechanism and controlof the enzymatic browning, metabolize at physio-biochemical, building the theory of stressdamage and biology has a important theoretical sense in the field of fresh-cut fruits andvegetables. Furthermore, these studies can make theoretical basis on the fresh-cut fruits andvegetables industry. There are two parts:1. In order to improve and perfect the theory of enzymatic browning and control of thetheoretical foundation on fresh-cut fruits and vegetables, the fresh-cut eggplant and sweetpotato were used to study the mechanism of enzymatic browning and physiological reactionin the distant tissue from cutting site. The results showed that enzymatic browning of eggplantand sweet potato occurred rapidly by fresh-cut treatment, enzymatic browning of sweet potatolagged behind eggplant. Two kinds of vegetable’s POD activity and MDA content graduallyincreased during storage, total phenol content and PAL activity first increased and thendecreased. The PPO activity of fresh-cut sweet potato gradually increased, but the PPOactivity of fresh-cut eggplant showed a descending trend. In addition, the browning reactionof wound induced not only in cutting surface of fresh-cut fruits and vegetables,physio-biochemical changes were induced away from cutting site. This is a result of defenceresponse of collaborative injury in entire tissue caused by stimulated signal transductionproduced by stress damage.2. The fresh-cut sweet potato was used as material to study the enzymatic browning to clarify the mechanism of enzymatic browning and control caused by injury stimulation duringstorage at10℃. Different concentration of D-sodium erythorbate, citric acid and calciumlactate were used in single factor experiment, and orthogonal test was conducted by browninginhibitory effect. The results showed that D-sodium erythorbate, citric acid and calciumlactate have different inhibitory effect on browning compared to the blank control. TheD-sodium erythorbate showed higher effect and calcium lactate followed. The most optimumconcentration were:1.0%D-sodium erythorbate,0.03%citric acid,1.0%calcium lactate. Themost optimum browining inhibitor could inhibit the PPO activity effectively, which composedof1.5%D-sodium erythorbate+0.03%citric acid+1.0%calcium lactate. Moreover, theinhibitory effect of combination was better than single, inhibiting the browning and extendingthe shelf-life.