Determination of the correlation between amylose and phosphorus content and gelatinization profile of starches and flours obtained from edible tropical tubers using differential scanning calorimetry and atomic absorption spectroscopy

Abstract

Xanthosoma sagittifolium, Colocassia esculenta, and Ipomoea batata plants produce underground storage organs that contain mainly starch and fiber. These staple food items have been misused for many years and in many instances they exhibit a high percentage of loss because of spoilage. However, the availability of tropical and subtropical crops such as Xanthosoma sagittifolium, Colocasia esculena, and Ipomoea batata in the temperate zones of the world has increased in recent years because research has improved varieties of these crops by agronomic and genetic techniques. With the excellent varieties available today, they could be grown more extensively and constitute farinaceous foods of high nutritive and economical value. Before they are more widely used, the functional properties of these tubers must be evaluated. One of the approaches to characterize functional properties of the starches or flours obtained from storage organs of these plants is through gelatinization profiles. The gelatinization profile can be determined using several techniques of which differential scanning calorimetry (DSC) is the most common. It is a general consensus that the gelatinization profile is a function of the amylose and phosphorous contents of starches. In this study the gelatinization profiles of starches isolated from Colocasia esculenta, Xanthosoma sagitifolium, and Ipomea batata storage organs were evaluated using changes in the heat flow or enthalpy during the gelatinization process by DSC methodology. The amylose content was also evaluated using the DSC technique and a colorimetric method. The phosphorous content was analyzed by colorimetry using the method described in AOAC, 1993. The results show that starch isolated from Ipomoea batata has a similar amylose content as starch isolated from Xanthosoma sagittifolium. Both show more starch content than Colocasia esculenta. The phosphorous content was higher in Ipomoea batata than Xanthosoma sagittifolium or Colocasia esculenta starches. The gelatinization profile range is wider in Ipomoea batata than the other two starches. Differences in these parameters may affect the functional properties of the products formulated with these starches.