Study Of Polyphenols Correlation With Non-enzymatic Browing In Apple Juices

Browning is a major technical problem in apple juice industry and it seriously affects the quality of apple juice during the production and storage process. The browning of apple juice is closely related with polyphenols. Apple polyphenol interacts with polyphenol oxidase(PPO) and oxygen, resulting in enzymatic browning in apples. Meanwhile, the high activity of o-quinone can induce further polymerization, prompting juice non-enzymatic browning in the absence of PPO. While a great deal of research has focused on the enzymatic browning of apple polyphenols, there are fewer studies on the non-enzymatic browning originated from apple polyphenols. Accordingly, the object of the present paper mainly studied about PPO enzymatic inducing non-enzymatic browning of apple polyphenols by employing chlorogenic acid, catechin, epicatechin, and phlorizin as reaction subjects.(1)Browning occurred in apple system with catechin epicatechin, chlorogenic acid and phlorizin without added PPO. The results indicated that the model juice systems containing catechin, epicatechin and chlorogenic acid, respectively, had the consistent change trend of L*, b*, △E* value with reduced L* value, whiteness, brightness, and increased b*, △E* value as well. The color of the systems became yellow. The a* value increased in the systems with the addition of catechin and chlorogenic acid, respectively. The negative a* value increased in the model juice with added epicatechin. Meanwhile, the color of the system was green. Compared with catechin, epicatechin and chlorogenic acid, the degree of browning was weak in the model juice containing phlorizin.(2)The correlation of apple polyphenols with non-enzymatic browning was first investigated. The results showed that much was made of the discrepancies amonge the effects of inducing systems on the non-enzymatic browning in the model juice. The enzymatic inducing temperature had no significant influence on the non-enzymatic browning properties of the model apple juice containing catechin. However, p H, and PPO activity had significantly affected on non-enzymatic browning, A high degree of browning was developed in the model juice at p H4.0; In the epicatechin system, longer inducing time, higher inducing temperatures, higher p H increasing enzymatic activities can accelerate browning reaction. In the model juice containing chlorogenic acid and phlorizin, respectively, the inducing temperature, time, p H and enzyme activity also affect the non-enzymatic browning. It was also evidenced in the work that polyphenols has close relationship with the haze of apple juice.(3)The non-enzymatic browning of catechin, epicatechin and phlorizin induced by chlorogenic acid o-quinone was also researched. It was shown that the rates of non-enzymatic browing of catechin and epicatechin induced by the chlorogenic acid quinone were lower than that their own alone. The chemical properties of phlorizin was very stable, and it could not occur own polymerization reaction. Meanwhile, it could not be induced by chlorogenic acid o-quinone. However, PPO could induce it resulting in further non-enzymatic polymerization and browning.