| Summary: | 碩士 === 靜宜大學 === 食品營養研究所 === 94 === Abstract
The purposes of this study were to investigate the changes of physicochemical properties and enzymatic activity of yam tubers during storage. The analysis of physicochemical properties included starch content, free sugar content, textural and color profiles, cooking losses, water soluble solid and enzyme activity of yam tubers. This study also investigated the difference of physicochemical properties in three sections of yam tubers during storage.
The results showed that the weight of yam tubers decreased due to the moisture evaporation during storage period. Crude fiber of proximate compositions of yam tubers increased as storage time progressed. Comparing the activity of polyphenol oxidase (PPO) in the three sections of yam tubers, the highest PPO activity was found in stem tip section. Meanwhile, the activity of PPO in three sections of yam tuber increased with the increase of storage time and reached the highest at 10th weeks, then gradually decreased later during storage. The degree of enzymatic browning reached a peak level at 10th weeks which evidenced the activity of PPO strongly influenced the color changes of yam tubers. The highest amylase activity was located in the stem tip of yam tuber. The amylase activity of yam tuber increased with the increase of storage time. The changes of free sugar content were similar to the amylase activity during storage. However, the monosaccharide composition of free sugar was not significantly changed during storage. The cooking losses of yam tubers decreased with increase of storage time and reached the lowest level at 10th weeks. As comparing the changes of hardness, color and cooking losses in three sections of yam tuber, the stem middle of yam tuber exhibited the most stable physical properties.
The results of this study could conclude that the deterioration of yam tuber during storage strongly affected by the changes of amylase and PPO activity. The results inferred that the changes of physicochemical properties would be used as indicator of quality of yam tuber after harvest.
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