Purification and Properties of the Pectinesterases from Guava(Psidium guajava L.)

• Main Authors: Ou, Yi-Der, 歐翼德
• Other Authors: 陳雪娥
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/38891469724511814386

碩士 === 輔仁大學 === 食品營養學系 === 84 === 　　Pectinesterase(PE) plays an important role in fruit softening du ing ripening and in juice processing. In this study, the extraction andpurification of pectinesterases from cv. Chung-sun guava were investigated, and some properties of the pectinesterases were studied as well. 　　Results showed a maximum activity was obtained with 0.75 M NaCl solution, 4% polyvinypolypyrrolidone (PVPP) added, pH 10.5, and four hours for extraction. Under the high alkali conditon, some cell wall bound pectinesterases were solubilized and the viscosity of crude extract was decreased so that subsequent concentration by ultrafiltration could be carried out more efficiently. With PVPP added the colored materials formed during incubation and polyphenols were adsorpted. And adjusting the pH of crude extract to 7 could maintain more residual pectinesterase activity and remove more pectin after centrifugation following 24 hrs set. It was also found that the activity of pectinesterase in guava peel is higher than that in the pulp. 　　Application of Q-cartridge strong anion exchange chromatography enabled the separation of two forms of the enzyme, PE I and PE II. PE I was purified about 24 folds, while PE II was purified about 22 folds. By the analysis of chromatography it was supposed that the pI of PE I was higher than or equal to 9.5 and the pI of PE II was slightly lower than 9.5. Besides PE I and PE II, there were some pectinesterases detected in the fractions eluted with higher salt concentration. Therefore it was suggested that two isozymes at least existed. PE I exhibited an optimum pH at 7 and an optimum temperature at 55℃. PEI was more heat-stable with D70℃ of 2367.8 sec, D80℃ o f112.1 sec, D85℃ of 22 sec, and Z value of 7.4℃. PE II was less heat-stable with D65℃ of 363.4 sec, D70℃ of 82.7 sec, D75℃ of 30.1 sec, and Z value of 9.3℃. However, crude enzyme extract or the enzyme in juice was more heat-resistant.