Abstract
The thermal and pasting properties and Resistant Starch (RS) formation of high amylose rice flour were investigated at 121°C using different solvents and storage times. The samples treated with water and lactic acid 10 mmol/L with storage times 0, 24, 48 and 72 h had the highest degree of gelatinization, ranging from 98.64 to 99.86%. The samples treated with ethanol and lactic acid 10 mmol/L (in ethanol) had degrees of gelatinization varying between 58.25 and 59.91%. For the study on the thermal properties, the onset temperature (To), peak temperature (Tp), conclusion temperature (Tc) and enthalpy (ΔH) of resistant starch preparation (retrograded rice flour) using water and lactic acid 10 mmol/L were not observed, but those of heated flour using ethanol and lactic acid in ethanol (10 mmol/L) were detected. The endothermic peaks of the amylose-lipid complex and resistant starch were also observed at higher temperatures from the Differential Scanning Calorimeter (DSC), with no effect of treatments on To, Tp and Tc. Rice flour heated in water and then stored for 24 h showed a favorable effect on formation of RS at 10.80%. Significant reductions were observed in all Rapid Visco Analyzer (RVA) viscosities of the retrograded rice flours.
Highlights
Resistant Starch (RS) refers to flour or starch products, which cannot be digested by enzyme α-1,4 amylase, or absorbed in the small intestine of humans
The rice flour treated with water and lactic acid 10 mmol/L as solvents showed degrees of gelatinization between 98.64 and 99.69%, whereas the degrees of gelatinization of flour treated with ethanol and lactic acid (10 mmol/L in ethanol) were between 58.24 and 60.72%
The results revealed that the amount of RS significantly reduced with storage time increase from 24 h for water and 48 to 72 h at 60°C in other treatments
Summary
Resistant Starch (RS) refers to flour or starch products, which cannot be digested by enzyme α-1,4 amylase, or absorbed in the small intestine of humans. This results in health benefits as dietary fibers and prebiotics. When RS passes through the colon it is fermented by bacteria to short chain fatty acids. These acid groups are beneficial to health by inhibiting the growth of pathogenic microorganisms. RS2 is condensed and partially crystalline native starch granules found in unripe banana, raw potato and high-amylose corn starches. RS4 can be produced by the chemical modifications to make the starch resistant to the action of enzymes such as starch phosphates, hydroxypropyl starches, starch acetates and citrate starches (Wepner et al, 1999)
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