Effect of Polyphenol Oxidase Activity on Discoloration of Noodle Dough Sheet Prepared from Korean Wheats
2008
Kang, C.S. (Honam Agricultural Research Institute, NICS, RDA, Iksan, Republic of Korea) | Cheong, Y.K. (Honam Agricultural Research Institute, NICS, RDA, Iksan, Republic of Korea) | Kim, S.L. (National Institute of Crop Science, RDA, Suwon, Republic of Korea) | Kim, D.K. (Chonbuk National University Medical School, Jeonju, Republic of Korea) | Kim, J.G. (Honam Agricultural Research Institute, NICS, RDA, Iksan, Republic of Korea) | Park, C.S. (Honam Agricultural Research Institute, NICS, RDA, Iksan, Republic of Korea), E-mail: [email protected]
Polyphenol oxidase (PPO) is implicated in discoloration of white salted noodles and other wheat based foods. PPO activity was evaluated to determine the effect on discoloration of noodle dough sheets prepared from 25 Korean wheat flours during storage and to screen experimental lines with low PPO activity in 52 Korean wheats. PPO activity was assayed with whole-seed and performed with L-dihydroxyphenylalanine (L-DOPA) as substrates. Absorbance by L-DOPA assay of 25 Korean wheats was from 0.285 to 1.368 at 475 nm. PPO activity was significantly related with grain characteristics, including 1000-kernel weight and grain colors. In flour characteristics, PPO activity positively correlated with ash and protein content (r = 0.658, P less than 0.001 and r = 0.424, P less than 0.05, respectively) and negatively correlated with L* value of flour (r = 0.412, P less than 0.05). In the changes of color of noodle dough sheet, L* and b* values consistently decreased and a* value increased during storage. PPO activity negatively correlated with L* value of noodle dough sheet during storage (r = 0.566, P less than 0.01 at 2 hr, r = 0.547, P less than 0.01 at 24 hr, and r = 0.509, P less than 0.01 at 48 hr). But, no significant relationship was found in between PPO activity, a* and b* values during storage. The 52 Korean wheat lines examined in this study were divided into 3 different groups, low (less than 0.500), medium (0.501-0.999) and high level (greater than 1.000), on the basis of the level of PPO activity. Twenty two Korean wheat lines showed low level of PPO activity and Suwon 252, 277 and 280 showed lower PPO activity (less than 0.200) than others.
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