Formation and properties of aqueous compatible colloidal blends between pre-gelatinized maize starch and zein

Abstract

This study investigates the formation and properties of compatible binary colloidal blends between pre-gelatinized (uncomplexed and complexed with stearic acid) maize starches (hydrophilic component) and commercial zein (hydrophobic component) with the aim of creating a bipolymeric material with unique properties. The blends were formed under alkaline condition (0.1 M NaOH) with 3:1, 1:1 and 1:3 starch: zein (w/w) ratios. The 3:1 starch–zein blends showed best stability or compatibility. Blends made with starch complexed with stearic acid had better stability than those with uncomplexed starch. Most of the blends were not freeze-thaw stable except for 3:1 starch (complexed with stearic acid)-zein blend. The blends with better stability had higher apparent viscosity, and a microstructure showing uniform mix of starch – zein as observed by confocal laser scanning microscopy. The likely reason for the compatibility of starch and zein is the change in surface activity of zein, possibly due to deamidation, in 0.1 M NaOH as shown by the negative zeta potential values. The pre-gelatinized maize starches also show negative zeta potential values. In conclusion, compatible binary colloidal blends can be produced between pre-gelatinized maize starch and commercial zein using 0.1 M NaOH.