Rheological properties of starch isolated from longan kernels with protease-assisted alkali method

Abstract

As a byproduct from the deep processing of longan fruit, longan kernel is rich in starch and is a good source for starch production. In this study, the rheological properties of longan kernel starch (LS) extracted by protease-assisted alkali method were investigated. When the shear rate was from 1 to 100 s−1, the pastes containing 4%–7% (w/v) of LS showed a non-Newtonian fluid with a pseudoplastic fluid characteristic. Their shear stress, apparent viscosity, complex viscosity, storage modulus (G′), and loss modulus (G″) positively correlated with starch concentration. The loss factor (tan δ) of all LS pastes was less than 1. At same concentration, LS paste showed a stronger pseudoplastic fluid characteristic and higher elasticity than corn starch and pea starch pastes. Based on this, LS has potential in processing of jelly, soft sweets, ham sausage, and some other sauces.