Effect of single and dual steps annealing in combination with hydroxypropylation on physicochemical, functional and rheological properties of barley starch.

Dual modification of barley starch using annealing and hydroxypropylation was carried out. The native starch was first annealed in single step and dual step. After that, hydroxypropylation of the native, single step and dual step annealed starches were performed. The properties of native and modified starches were then investigated. Relative crystallinity of the modified starches decreased with level of hydroxypropylation and increased on annealing. Swelling, solubility, freeze-thaw stability and paste viscosities increased on hydroxypropylation and decreased with annealing. Paste clarity increased on both annealing and hydroxypropylation. Freeze-thaw stability, paste clarity and final viscosity were higher for dual modified barley starches modified by combining annealing and hydroxypropylation. Rheological studies revealed pseudoplastic nature of the starches. The flow behaviour index was found to decrease with level of hydoxypropylation for native starch, but increased for the dual modified starches. Dual modification of barley starch by combining dual step annealing with hydroxypropylation significantly improved the properties of native starch.