A Study on the enzymatic browning in relation to polyphenol oxidase and polyphenol contents in different vegetable sponge(Luffa acgyptiaca Mill) and angled luffa(Luffa acutangula) cultivars

• Main Authors: Chun-Chi Su, 蘇群棋
• Other Authors: Kai-Ts''ung Yang Ph.D.
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/34567347126849209671

碩士 === 中國文化大學 === 生活應用科學研究所 === 87 === The objectives of this research are focused on two aspects. The first one is to study the enzyme characteristics of polyphenol oxidase of the samples chosen. The second one is to study the relationship among the polyphenol composition, the contents, and tissue browning in various cultivars of vegetable sponge and angled luffa. Summer-harvested of vegetable sponges and angled luffas, including Dong Guang, Dong Guang No. 2, Dong Guang No. 3, Chi Shi, Chi Shing, Chi Mei No. 2, F85-568, Mei Ling, and San Shi were used for this study. Crude enzyme extracts were obtained through extraction and centrifugation. When L-DOPA is used as the substrate for the determination of polyphenol oxidase, it is found that the optimum temperature for the reaction is between 30-35℃, and the optimum pH value is between 3.0-6.0. Among the tested cultivars, Chi Shi has the highest enzyme activity, followed by Dong Guang No. 3, Chi Mei No. 2, F85-568, Chi Shing, Dong Guang No.2, Mei Ling, San Shi, and Dong Guang. Chi Mei No.2 is the most unstable one in thermal stability tests by heating to 50℃. When temperature is raised above 50℃ thermal stabilities of all samples become stable between 70-90℃. In terms of inhibitors, the research results show that the inhibition of ascorbic acid is more effective than cysteine, sodium metabisulfide, and benzoic acid. The enzymatic browning of each cultivar was tested by using both slice samples and liquid samples, both incubated in 30℃ oven for 0, 10, 30, 60, 180 minutes. Differences were noted when the L, a, and b values were examined by the color difference meter. For slice samples the degrees of browning are in the descending order are: Dong Guang, Chi Mei No. 2, Dong Guang No. 2, F85-568, Mei Ling, Chi Shing, Chi Shi, Dong Guang No. 3, and San Shi, while in liquid samples the order are:Chi Mei No. 2, Chi Shing, Chi Shi, Dong Guang, San Shi, Mei Ling, Dong Guang No. 2, Dong Guang No. 3, and F85-568 in descent. The differences between slice samples and liquid samples should be attributed to different destroyed methods applied to vegetable sponge and angled luffa texture, different contact areas exposed to oxygen and substrates for polyphenol oxidase. Experiment results fail to show a significant correlation between the tendencies of L, a, b values and enzyme activities. It is proposed that the enzymatic browning of vegetable sponge and angled luffa could also be affected by the contents and composition of polyphenols. Results from the analyses of nine different vegetable sponge and angled luffa cultivars on HPLC indicate that chlorogenic acid is the most aboundent one, catechol is the second, and then epicatechin. Cultivars of vegetable sponge and angled luffa were incubated for 0, 10, 30, 60, 180 minutes in a 30℃ oven to see if there were difference in polyphenol contents by HPLC analysis it was shown that the content of chlorogenic acid, epicatechin and catechin were stable in Dong Guang No. 3 and F85-568, decreasing along with time in Dong Guang and Chi Mei No. 2, and nonsignificant changes in Dong Guang No. 2, Chi Shi, Chi Shing, Mei Ling, and San Shi. From this study, it is suggested that the changes in the magnitudes of chlorogenic acid, epicatechin and catechin contained should be the major factors attributing to the enzymatic browning of vegetable sponge and angled luffa, while total contents of phenolic compounds do not play a significant role.