摘要
鲜切甘薯中的酚类物质以游离酚(FP)为主,占总酚(TP)的90%左右。贮藏过程中FP和TP均呈先上升后下降的变化规律,且其比值(FP/TP)稍有增加。鲜切甘薯多酚氧化酶(PPO)活性在切分后有所增加至第3d达最大而后下降直到贮藏结束,与TP和FP的变化呈同步性,而过氧化物酶(POD)和过氧化氢酶(CAT)的活性则基本保持不变。鲜切甘薯PPO的最适反应温度为15.2℃,且在该温度下较为稳定,另在50℃处有一肩峰。PPO的最适pH值为4.4,pH4.0以下或者8.5以上PPO活性迅速下降。NaHSO3、CA、EDTA-2Na和VC对鲜切甘薯PPO均有不同程度的抑制效果。甘薯PPO对不同底物的酚类物质亲和力依次为儿茶酚>焦性没食子酸>绿原酸>酪氨酸>苯酚>愈创木酚。鲜切甘薯中主要的酚类物质和酶促褐变底物为绿原酸。
The free phenols (FP) in the amount of over 90% of total phenols (TP) were found predominant in freshcut sweet potatoes, and the ratio of FP/TP increased a little during storage. The content of FP and TP increased in the first three days and then decreased. The activity of PPO extracted from freshcut sweet potatoes was also increased in the first three days and then decreased. The results showed that the same tendency existed with the changes of FP and TP, while the activities of POD and CAT maintained consistent during storage. The optimal temperature for the enzyme was 15.2℃, at which it was more stable than elsewhere, while there was a second optimal temperature at 50℃. The optimal pH for the PPO was 4.4, and the PPO activity dropped rapidly when pH was below 4.0 or above 8.5. NaHSO3, CA, EDTA-2Na and VC all had inhibiting effect on PPO with different efficacies. The combining capability of PPO with different substrates was in the order of catechol, pyrogallol pyrogallic acid, chlorgenic acid, tyrosine, phenol and guaiacol. The main phenol with also enzymatic browning substrates in fresh-cut sweet potatoes was chlorgenic acid.
出处
《食品科学》
EI
CAS
CSCD
北大核心
2005年第5期54-59,共6页
Food Science
基金
国家十五科技攻关项目(2001BA501A10)
关键词
甘薯
酶促褐变
机理
sweet potatoes(Ipomoea batatas)
enzymatic browning
mechanism
