Study On The Effect Of The Epidermal Enzymatic Browning To Carrot By Antibrowning Agents

The effects of antibrowning agents of different concentrations on the commercial quality, browning related enzymes and other physiological and biochemical indexes of carrot under room temperature were studies and the optimal antibrowning agent was determined. In addition, the effect of the optimal antibrowning agents on enzymatic browning of carrot and its browning mechanism were further explored. The results showed that:1. The effect of antibrowning agents of different concentrations (0.1%,0.3%,0.5%) on the related postharvest physiological and biochemical indexes of carrot under room temperature(20℃) were studied. The experimental results showed that:all the antibrowning agents could kept carrots good appearance and commercial value, inhibited the increase of browning substrates-phenolic compounds and browning enzymes-PPO, delayed the formation of brown spots, The best concentration was 0.5%.2. The effect of the optimal antibrowning agents on postharvest quality, enzymatic browning substrates, related enzymes of carrot under room temperature were studied. The experimental results showed that:antibrowning agents can effectively inhibited the rise of the browning index, color index, soluble solids and the decline of carotenoid, through observing ultrastructure changes, it was found that antibrowning agents could more effectively maintain the integrity of cell membrane, epidermal damage was minor, thus can kept good appearance and quality. In addition, the main browning substrate of carrot was chlorogenic acid, antibrowning agents could effectively inhibit the accumulation of phenolic acids, the increase of the activity of polyphenol oxidase(PPO), peroxidase(POD) and phenylalanine ammonialyase(PAL), comparing different parts of carrot, it was found that the change degree of PPO, POD activity of the lower part was always higher than that of the upper.3. The influence of the optimal antibrowning agents on membrane lipid peroxidation of carrot under room temperature were studied. The experimental results showed that: antibrowning agents could effectively inhibit the increase of cell membrane permeability, the activity of lipoxygenase(LOX), the change of malondialdehyde(MDA), thereby inhibiting membrane lipid peroxidation, reducing intracellular substances to leak, delaying the browning degree of carrot, comparing different parts, it was found that the change degree of LOX, MDA of the lower part was always higher than that of the upper, the difference of cell membrane permeability was not obvious.4. The effect of the optimal antibrowning agents on epidermal active oxygen scavenging enzymes of carrot under the room temperature were studied. The experimental results showed that:antibrowning agents could effectively delayed the change of catalase(CAT), ascorbate peroxidase(APX), inhibited the decrease of glutathione reductase(GR) activity, reduced the accumulation of active oxygen, thereby delayed the browning and made the carrot maintaining better value and appearance.5. The effect of the optimal antibrowning agents on epidermal endogenous antioxidant substances of carrot under room temperature were studied. The experimental results showed that:antibrowning agents could effectively inhibit the decline of ascorbic acid(Vc), increaced the flavonoids, maintained the relatively stable of glutathione(GSH). Comparing different parts of carrot, it was found that the change of epidermal endogenous antioxidant substances of carrot in lower part was more obvious.6. The protein changes of carrot during storage was studied. The results showed that the number and the content of protein changed during storage, there were more proteins in the carrot by using antibrowning agents than that in the control, besides, protein spots were mainly in the pH3-10 region, relative molecular weight was mainly concentrated in the 35-116KD. Significant differences was found in 31 proteins, the content of 15 proteins increased and 16 proteins decreased during storage, they could be further used in cutting gels and mass spectrometry analysis.