Raw Material Selection And Color Protection Conditions Of Dried Caozhou Chaenomeles Sinensis

Using Caozhou Chaenomeles sinensis (Thouin) koehne as the material, the content of polyphenols, flavonoids, total sugars, organic acids and oleanolic acids in Caozhou Chaenomeles sinensis of different harvest periods and different species were compared. On this basis, the most appropriate harvest time and the best varieties for dried Caozhou Chaenomeles sinensis were determined. The characteristics of the key enzymes that involved in the enzymatic browning of Caozhou Chaenomeles sinensis-polyphenol oxidase (PPO) and peroxidase (POD) were studied. The influences of citric acid, sodium hydrogen sulfite, ascorbic acid and L-cysteine on the color of dried Caozhou Chaenomeles sinensis were evaluated and the optimum conditions for color protection were investigated by single factor test and orthogonal test. The main results were as follows:1. The best variety for the production of dried Caozhou Chaenomeles sinensis was Fomian, and the optimum harvest time was between September 26 to October 1.2. The PPO had an optimum pH of 5.0 and optimum temperature of 30?. The PPO was almost inactivated when it was incubated in 90? for 5 min or 100? for 1 min. The kinetics of enzyme-catalyzed reaction of PPO was in accord with Michaelis-Menten equation, and the Km, Vmax of kinetic equation were 6.92 mmol/L and 769.23 U respectively, using catechol as substrate. Five inhibitors demonstrated different effects on PPO and the order of inhibitor effectiveness was:NaHSO3>ascorbic acid>L-cys>citric acid>EDTA-2Na. Na+ and K had no effect on PPO activity. The PPO showed increased activity in presence of Al3+, Ba2+ and Cu2+ Mg2+, Mn2+ and Ca2+ activated PPO at lower concentration (1 mmol/L) while inhibited at higher concentration (10 mmol/L).3. The POD had an optimum pH of 5.8 and optimum temperature of 45?. However, the POD was inactivated when it was incubated in 90? for 75 s or 100? for 30 s. The kinetics of enzyme-catalyzed reaction of POD was in accord with Michaelis-Menten equation, and the Km, Vmax of kinetic equation were 18.17 mmol/L and 1666.67 U respectively, using guaiacol as substrate. Five inhibitors demonstrated different effects on POD and the order of inhibition effect was as follows:ascorbic acid>L-cys>NaHSO3>citric acid>EDTA-2Na. The POD showed increased activity in presence of Na+, K+, Mg2T, Mn2+ and Ca2+. Zn2+, Ba2+ and Cu2+ activated peroxidase at lower concentration (1 mmol/L) while inhibited at higher concentration (10 mmol/L).4. All of the four kinds of color fixatives-citric acid, sodium hydrogen sulfite, ascorbic acid and L-cys, had an positive role in preserving the color of dried Caozhou Chaenomeles sinensis and the optimum conditions were L-cys (1.0 g/L), Vc (4 g/L), NaHSO3 (0.3 g/L), citric acid (4 g/L).