Characterization and Comparison of Alkali Extracted Starches from Selected Cereals and Tubers

Abstract

Aims: Starch is used in the food industry to impart functional properties and to modify food texture and consistency. In this study starches isolated from six sources using an alkali extraction method were evaluated for physicochemical properties.
 Study Design: Complete randomized design.
 Place and Duration of Study: Department of Food Science and Technology, Faculty of Livestock, Fisheries, & Nutrition, Wayamba University of Sri Lanka, Makandura, Gonawila (NWP), Sri Lanka between April 2017 and August 2017.
 Methodology: Starches were isolated from white rice, foxtail millet, proso millet, cassava, sweet potato and all-purpose wheat flour. Proximate composition, mineral content, physical properties and microscopic characteristics were determined and they were compared.
 Results: The level of starch extracted was within the range of 27.5-64.1% on a dry basis. Extracted starched contains about 99% carbohydrate in DW and less than 1% non-carbohydrate fraction (protein, fat, fiber and ash and minerals). The amylose content followed the order: proso millet > wheat > foxtail millet > rice > sweet potato > cassava. There was considerable variation in swelling factor, solubility, gelatinization temperature among all starches. Both swelling power and solubility had a positive relationship with temperature and the swelling power (at 90°C) followed the order: corn > cassava > foxtail millet > wheat > proso millet > rice > sweet potato. The gelatinization temperature of starches ranged from 62°C to 76°C.
 Conclusion: The study would be helpful to better understand the chemical, physical and microscopic characteristics of these starches and the application of novel starches obtain from non-conventional sources which are foxtail millet, proso millet and sweet potato as a thickening agent and a substitute to other common starches in food.

Comparative Study on Functional Properties of Starch Extracted from Various Sources

“…Starch from traditional black rice and sorghum was extracted using the alkali method (Wijesinghe & Gunathilake, 2020). The procedures used for the extraction of starch are as shown in Figure 1.The starch yield was calculated using the following equation.…”

“…From Figure 2, it can be observed that the starch yield of traditional black rice and sorghum was found to be 50.14% and 44.78% respectively. Less yield of starch is due to lower dispersibility and solubility of glutens present in the sample, and also difficulties in filtering due to an increase in viscosity of sample slurry (Wijesinghe & Gunathilake, 2020).…”

“…These differences in amylose and amylopectin content in starch samples are due to the starch extraction method, different genotypes, and environmental factors. More amylose gives better gel strength and more amylopectin gives higher viscosity (Wijesinghe and Gunathilake, 2020). Hence, rice starch and sorghum starch can be used to improve the gel strength and viscosity of the products respectively.…”

“…The pH of starch can act as a quality indicator (Kasaye Atlaw, 2018). Also, when the pH of starch is low, paste clarity is more, and vice versa (Wijesinghe and Gunathilake, 2020). Hence, the lower the pH value of the starch, the clearer is the paste of the starch.…”