Development of ready-to-eat rice starch-based puffed products by coupling freeze-drying and microwave

Abstract

The rice starch mixtures with varying amylose contents (AC) of 0.12-19.00% weight were prepared by mixing waxy and nonwaxy rice starches. The 5% rice bran oil shortening was added in the starch paste. After gelatinisation, thin slabs of starch pastes were aged at 4 °C for 24 h. The aged slabs were dried by freeze-drying to obtain 25% moisture content. A microwave oven set to 600 J s-1 for 90 s was then used for puffing. The crucial factors affecting the snack purchase were texture and nutrition. The relative crystallinity and retrogradation enthalpy (Hr) of freeze-dried pellets increased with increasing the AC. From using a differential scanning calorimeter (DSC), endotherms of pellets were shown only when AC > 0.12%. An amylose-lipid complex was shown in pellets with AC ≥ 9.00%. Relationships between the AC and all puffed product properties were linear. Increasing AC provided greater hardness, fracturability, bulk density, but lower expansion ratio. From the sensory evaluation, the panellists preferred the puffed products with 9.00% AC. Increasing the AC gave higher crispness, hardness, brittleness, air cell opacity and density, but resulted in less puffiness. Thus, the microwave drying has the potential to puff a healthy expanded snack but giving the desirable properties depends on AC. Increasing amylose content results in more hardness, fracturability and bulk density but less expansion ratio. The crystallinity provides a higher crispness but a lower puffiness. © 2016 Institute of Food Science and Technology.