Studies on the Physicochemical Properties of the Tubers of New Sweet Potato Lines

甘藷新品系塊根理化性質之研究

劉新裕(S. Y. Liu) ； 梁純玲(C. L. Liang) ； 李良(L. Li)

《中華農業研究》 34卷1期 (1985/03) Pp. 21-32

https://doi.org/10.29951/JARC.198503.0003

摘要

本研究在分析甘藷17個新品系及臺農57號塊根之理化性質，藉以評估其品質之優劣及探討甘藷塊根之乾物率、澱粉率，還原糖含量與澱粉水解酵素之活性間的相互關係。
在物理性質方面，這18個甘藷品系（種）的澱粉粒大小介於28.98×26.57μ及8.05×7.25μ之間。所有甘藷澱粉溶液於溫度上升到90℃時之粘度約爲最初室溫的20屠。由90℃冷卻回室溫時，其粕度呈繼續上升趨勢，只有C70-111及C71-94二品系的粘度略呈下降現象。有三個新品系之塊根乾物率超過40%，而所有甘藷新品系之平均乾物率高達36.6%，且都比臺農57號的27.8%爲高，塊根之含水率則以臺農57號最高(72.2%)，超出含水率之平均值達8.3%。
在化學性質方面，參試甘藷烘乾塊根之澱粉率的變域在61.99%及75.38%之間，此表示因品種之不同將有很大的差異。在17個新品系中有53%新品系之澱粉含量超過平均值(67.93%)，即使最低的品系也含有61.99%的澱粉率，所以這些甘藷應歸屬於高澱粉之甘藷品系。塊根鮮重澱粉率之變域在18.42-30.68另之間。由於臺農57號之乾物率最低，此將明顯不利於鮮重澱粉率，其鮮重澱粉率爲所有參試甘藷中最低者(18.42%)，而C71-96則同時其有最高的鮮重及乾重澱粉率。在澱粉之化學結構中，顆粒澱粉之平均含量爲14.25%，其變域在8.50到17.32%之間。而烘乾塊根之平均還原醣含量爲3.71%，最高值達8.44%，最低的只有0.24%，此顯示在塊根中存在著或多或少的澱粉水解酵素，於常溫常壓下能分解塊根澱粉成爲還原醣。
在所有塊根之理化性質中，有下列三項性質呈現極顯著關係：塊根乾物率與鮮重塊根澱粉率(r=0.96599)，鮮重澱粉率與乾重澱粉率(r=0.76782)以及還原醣含量與澱粉水解酵素之活性(r=0.98117)。由於塊根乾物率與塊根鮮重澱粉率之關係爲爲密切，所以可由甘藷塊根乾物率來估算求得塊根鮮重澱粉率。兩者之直線迴歸方程式爲：Ŷ=0.82664 X-5.25795，Ŷ爲塊根鮮重澱粉率，X爲塊根乾物率，式中表示每提高塊根乾物率1%，即可能增加其塊根鮮重澱粉率0.83%。此應可利用爲高澱粉甘藷育種工作之一種指標。

並列摘要

This study was conducted with 17 new sweet potato lines and one commercial variety to investigate the physical and chemical properties of the tuber powder and to find out the relationship between tuber dry matter content, reducing sugar, starch content and enzyme activity of tuber amylase.
The starch granular size of these sweet potatoes ranged from 8.05×7.25μ to 28.98×26.57μ. The viscosity of the tuber powder solution at 90℃ was about 20 times as large as that at room temperature. After cooling from 90℃ to room temperature the viscosity was much higher than that at 90℃. The average dry matter content of these new lines amounted to 36.6%, being much higher than that of Tainung 57(27.8%). Three new lines had a dry matter content more than 40%. The tuber moisture content ranged from 56.5 to 72.2%, Tainung 57 had the highest moisture content, being 8.3% higher than the average.
The tuber starch content on dry basis ranged from 61.99 to 75.38%. More than half of the new lines had a higher tuber starch content than the average (67.93%). The tuber starch content on wet basis ranged from 18.42 to 30.68%. The commercial variety, Tainung 57, had the lowest tuber starch content on wet basis due to its low tuber dry matter content, while C 71-96 had the highest tuber starch content both on dry and wet basis. The average reducing sugar content was 3.71%. C71-196 had the highest value of 8.44%, while C66-33 had only 0.24%. The amount of the reducing sugar in tuber indicated that amylase more or less existed in the tuber. This enzyme can convert starch molecule into reducing sugar under normal pressure and temperature.
High significant relationships were found between these physicochemical properties, namely, tuber dry matter content and tuber starch content on vet basis (r=0.97), tuber starch content on wet basis and tuber starch content on dry basis (r=0.77) and reducing suger content and amylase activity (r=0.98). Because of the close relationship between tuber dry matter and tuber starch content on wet basis, the tuber dry matter percentage could be used to evaluate the tuber starch content on wet basis. A regression equation Ŷ=0.82664 X-5.25795 was then derived, where Ŷ was the tuber starch content on wet basis and X was the tuber dry matter.