Abstract
Starches were isolated from soaked and malted sorghum and studied to understand their physicochemical and functional properties. The swelling power (SP) and the water solubility index (WSI) of both starches were nearly similar at temperatures below 50 °C, but at more than 50 °C, the starch isolated from malted sorghum showed lower SP and high WSI than those isolated from raw and soaked sorghum. The pasting properties of starches determined by rapid visco-analyzer (RVA) showed that malted sorghum starch had a lower viscosity peak value (86 BU/RVU) than raw sorghum starch (454 BU/RVU). For both sorghum, X-ray diffractograms exhibited an A-type diffraction pattern, typical of cereal starches and the relative degrees of crystallinity ranged from 9.62 to 15.50%. Differential scanning calorimetry (DSC) revealed that raw sorghum starch showed an endotherm with a peak temperature (Tp) at 78.06 °C and gelatinization enthalpies of 2.83 J/g whereas five-day malted sorghum starch had a Tp at 47.22 °C and gelatinization enthalpies of 2.06 J/g. Storage modulus (G′) and loss modulus (G″) of all starch suspensions increased steeply to a maximum at 70 °C and then decreased with continuous heating. The structural analysis of malted sorghum starch showed porosity on the granule’s surface susceptible to the amylolysis. The results showed that physicochemical and functional properties of sorghum starches are influenced by soaking and malting methods.
Highlights
As more than 500 million people in developing countries depend on sorghum as the main staple food, relevant scientific information generated for this crop can certainly play a key role in food development [1]
The results indicated significant changes in terms of functional properties of sorghum starches obtained after soaking and malting
Starches isolated from malted sorghum showed lower swelling power (SP) and higher water solubility index (WSI) than those isolated from raw and soaked sorghum
Summary
As more than 500 million people in developing countries depend on sorghum as the main staple food, relevant scientific information generated for this crop can certainly play a key role in food development [1]. Starch is currently enjoying attention owing to its usefulness in different food products. Like other cereals, is rich in starch–a major storage form for carbohydrates–which makes up about 60-80% of normal kernels and has excellent potential for industrial applications [2,3]. Starch is used in a variety of food products as a raw material or food additive, and has an important role as a thickener, bulking agent, gelling agent, water absorbent and is used in foods with varying moisture contents such as puddings, cookies, or drinks. Starch modification, which involves the alteration of the physical, chemical and functional characteristics, can be used to tailor starch to specific food applications Some of the starch derivatives are being increasingly used as fat substitutes [4,5].
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