甘薯與馬鈴薯之營養價值

Abstract

甘薯與馬鈴薯富含澱粉、纖維及微量營養素，可作為主食或蔬菜食用。此二類作物之蛋白質品質優良；雖單位能量較穀類與豆類低，然其每日單位面積食能產量而言，卻高於主要糧食作物。紅心甘薯與甘薯葉之維生素A含量豐富，對某些開發中國家的人民，尤其是小孩及婦女很重要，可避免維生素A缺乏症。 甘薯與馬鈴薯的澱粉較難消化，並會降低蛋白質利用率，若經烹煮後則可改善之。以動物試驗探求甘薯脹氣原因，則可發現澱粉引起的脹氣量遠高於糖與膳食纖維，約佔百分之八十五。再將馬鈴薯及甘薯澱粉與其他作物所引起的脹氣比較，可知甘薯、香蕉及馬鈴薯澱粉同屬於高脹氣澱粉，而綠豆、小麥、樹薯、米等則屬於低脹氣澱粉。脹氣現象亦可因烹煮而改善之。 惟膳食纖維愈來愈受重視，由甘薯品種間纖維成分分析得知，可以育種方式培育口感佳、且膳食纖維較高之品種。 Sweet potato and potato, as food rich in starch, fiber and micronutrients, are suitable for staple food or vegetables. Both of them contain high quality protein. The two crops have lower energy contents but higher energy yields than many cereal and legumes. With high concentration in vitamin A, the red-fleshed roots and green tips of sweet potato could be used as a means to prevent vitamin A deficiency in the developing countries. The starch of both sweet potato and potato is hard to be digested and leads to flatulence. Besides, it reduces the availability of protein. These detrimental effects could be lessened if the tubers of sweet potato and potato are consumed in the cooked form. The factors affecting the occurrence of flatulence has been studied in the animal feed experiment. The experimental results showed that starch contributed to 85% of hydrogen production which is higher than resulted from sugar and dietary fibers. As compared to other crops, the starch of sweet potato, banana, and potato produced higher hydrogen than mungbean, wheat, cassava and rice. The importance of dietary fibers to human health is much emphasized nowadays. The analyses of fiber contents among different varieties of sweet potato demonstrated that new varieties with better eating quality and higher dietary fibers content could be developed by breeding.