Effects of crystallinity on puffing qualities of rice starch-based product

Abstract

The influence of relative crystallinity (RC) of retrograded starch gel (RG) and pellet (P) on physical properties as well as sensory attributes of rice starch-based puffed product (PD) was determined. Mathematical models for predicting of the sensory attributes of PD from either RC of the P or physical properties of the PD were developed. In order to achieve these aims, the effects of amylose content (AC in the range of 0.12-19.00% w/w on dry basis); cooling rate (1, 3, 5, and 9 °C/min) and aging time (24, 48, and 72 h) on RC, physical properties of RG; P and PD, and sensory attributes of PD were evaluated. Starches, isolated from waxy rice (RD 6) and non-waxy rice (Jeckchey-Saohai), were mixed to obtain an AC of 0.12, 4.00, 9.00, 14.00, and 19.00%. The crystalline type and RC of RG and P were determined by X-ray diffraction pattern (XRD) while retrogradation enthalpy (∆Hrt) was determined using Differential Scanning Calorimetry (DSC) thermogram. For all cooling rates and aging times, the polymorph (B and V) and endotherms were found for AC ≥4.00%. For gels and P, RC and ∆Hrt increased linearly with AC with slopes of 0.57 and 0.27 %RC/%AC, and 0.34 and 0.15 J/g%AC, respectively. They also increased with aging time from 24 to 72 h at least 7 and 15% for RC gel and P while ∆Hrt increased at least 4% and 7%. The cooling rate did not affect RC and ∆Hrt. An increase in hardness was found to be 0.53 and 1.20 N/%RC for P and PD, respectively. The fracturability of P increased 0.22 N/%RC. For the PD, the hardness, fracturability, and bulk density increased 1.20 N/%RC, 0.89 N/%RC and 0.03g/ml/%RC; while expansion ratio decreased 0.134/%RC. A higher RC of P provided smaller and denser air cell structures and lower expansion, but higher crispness, hardness and fracturability of the PD. The developed models showed that the RC of P in a range of 0.95-6.96% can be an excellent predictor of physical properties (hardness, fracturability, bulk density, and expansion ratio) and sensory attributes (air cell density, air cell size, expansion, puffiness, crispness, hardness, and brittleness) of PD (R2≥0.85). It also found that physical properties (hardness, fracturability and puffiness) and their match sensory attributes (hardness, brittleness, and crispness) did correlate (r≥0.85). Puffiness and crispness correlated to expansion and brittleness (r≥0.88). P having RC in the range of 2.8-3.7%, made from a starch of 9% AC, got the highest scores for appearance and texture while also having just the right intensity of crispness and hardness by 76.3-78.3% of consumers.