Barley starch: Structure, properties and in vitro digestibility - A review

Abundance, cheapness, biodegradability and non-toxic behaviour of starches attract many food and non-food industries. Starch provides viscosity, adhesion, texture and homogeneity to various food products. This review article deals with the chemical composition, structure, granular morphology, pasting, thermal and in vitro digestibility properties of barley starches. Significant variations were found in characteristics of starches from normal, waxy and high amylose barley cultivars suggesting their broader potential applications. Amylose content appears to be the major factor controlling almost all physicochemical properties of barley starch due to its influence on physico-chemical, functional, pasting and thermal properties. Morphological studies have reflected significant differences among barley starch granule shapes. Waxy barley starch granules composed of a mixture of large spherical, disc and lenticular shaped whereas normal and waxy starches showed small irregularly shaped starch granules. A characteristic of cereal starches, A-type crystallinity of barley starches were observed by X-ray diffractions. For barley starch, storage modulus (G') value for starch pastes was reported to be more than loss modulus (G'') and <1 value of tan δ (G''/G') of barley starch indicating their elastic behaviour than viscous.