Study On Processing Of Pomelo Browning

The content of total sugars, polyphenols, ascorbic acid, soluble protein and otheringredients in peel and pulp of three kinds of pomelos were measured in this paper; and theenzymatic characteristics of polyphenol oxidase (PPO) and peroxiadase (POD) in siji pomelopeel and pulp were also studied. Then the content changes of reducing sugars, amino acidsand ascorbic acid before and after browning in pomelo pulp were measured respectively, andthe type of browning reaction was to determine, the effective measures to protect the colour ofpomelo juice were choose.It was found that the optimum reaction pH of PPO in pomelo peel and pulp were6.0-6.6;the optimum reaction temperature for peel PPO was40-70℃, pulp PPO was50-70℃; thePPO from peel and pulp both were inactivation above80℃. The results showed that, the basiccharacteristics of PPO from siji pomelo peel and pulp were similar to the PPOs from othersources.It was found that the optimum reaction pH of POD in pomelo peel and pulp wererespectively5.0-6.0and6.6-7.0, the optimum reaction temperature for peel POD was40-60℃,pulp POD was30-80℃. The enzyme activity of peel POD began to denature after60℃for30min, and pulp POD began to denature above80℃for30min, so the pulp POD hadstronger thermal stability.It was also found that the browning of pomelo juice was mainly caused by pulp paste,and enzymatic browning was significantly inhibited by blanching. By full wavelength scaning,the results showed that the Maillard reaction and ascorbic browning occurred simultaneouslyin pomelo pulp paste. After storage in55℃for7days, the content change of reducing sugarsand amino acids of the pomelo pulp paste were not significantly, and ascorbic acid contentwas decreased by94.8%, so it was concluded that the ascorbic acid plays a major role in thebrowning. According to the above conclusions, some measures were designed to protect thecolour of pomelo juice which used during the actual processing, and the result was effectively.