| The potato (Solanum tuberosum L.) is one of the most important grain and cash crops. Potato tubers are rich in starch, proteins, vitamins, minerals, trace elements, and significant levels of important antioxidants such as carotenoids and phenolic acids which have positive effects on scavenging free radical and inhibiting disease growth. In this thesis, carotenoids and phenolic acids in the tuber of 21 varieties with different flesh color were studied. The main conclusions are as follows:1. Vacuum freeze drying pretreatment of tubers and high performance liquid chromatogramphic (HPLC) methods were developed for analysis of carotenoids and phenolic acids in potato tuber. Agilent 1100 UV detector and ZOBAX C 18(4.6×250 mm,5μm) chromatographic column were used for the separation of carotenoids and phenolic acids. The results showed that carotenoids were separated more effectively with the mobile phase acetonitrile:dichlommethane:methanol(75:20:5, contained 0.1% BHT)at the flow rate 1.0 ml/min and 450 nm wavelength. Phenolic acids were analyzed by methanol:water:acetic acid(30:70:2, v/v)as a mobile phase with a flow rate of 1.0 ml/ min. Chlorogenic acid and caffeic acid were monitored with at 327 nm, and protocatechuic acid was detected at 260 nm.2. There were significant differences between potato varieties in contents of total caroteniods, lutein and zeaxanthin. The content of total caroteniods ranged from 39.36 to 160.92μg/100g FW in different varieties, and yellow flesh potatoes had higher concentration than white or purple ones. Total carotenoids of yellow flesh rang from 87.85 to 160.92μg /100g. The contents of Lutein accounted for approximately 1/3 of total carotenoids content in many varieties and rang from 5.20 to 48.64μg/100 g FW. The content of zeaxanthin in deep yellow flesh potatoes was much higher, while white flesh potatoes had negligible amounts.3. After 2 months storage at 4℃, the contents of total carotenoids and lutein in tubers increased while zeaxanthin reduced to be indetectable. It can be speculated that lutein was more stable than zeaxanthin at 4℃storage. Because the type of carotenoids and their relative proportions were different between varieties, the changes of carotenoid were various after cold storage.4. Tuber color parameters were significant differences between varieties. The Values of b~*, C~* and YE-313 of tuber color showed significant positive correlation with carotenoids content. It was suggested that carotenoids content of tubers was highly associated with yellow flesh. The color parameters of L~*, a~* and b~* value from (L~*, a~*, b~*) color space produced the best regressions with contents of lutein+zeaxanthin and total carotenoids. The equations produced better consistency between results from prediction and mensurement. This method can be used to assess the tuber color and carotenoid content of potatoes in breeding.5. There were significant differences between potato varieties in contents of chlorogenic acid, protocatechuic acid, caffeic acid and total phenolic acids. Total phenolic acids ranged from 54.08 to 1708.85μg/g in experimental varieties. Varieties with purple flesh showed a high content of total phenolic acids and rang from 1566.71 to 1708.85μg /g, of them, the varieties of Sharon's blue and Macintosh black were the highest. Meanwhile, the content of phenolic acids in white varieties were much less. The chlorogenic acid was the most abundant among members of potato phenolic acids. It accounted for approximately 90% of total phenolic acids content.6. Purple flesh variety had higher DPPH radical scavenging activities. There was significant correlation between DPPH radical scavenging activities and total phenolic acid (r=0.9646, P＜0.01), and chlorogenic acid (r=0.9595, P＜0.01). It indicated that phenolic acids may act as active components in tubers, and chlorogenic acid could be playing an important role in antioxidant activities in potato tuber.
|
PDF Full Text Request