Influence of sodium chloride and vacuum impregnation on the quality and bioactive compounds of parboiled glutinous rice

Abstract

This study investigated the effect of NaCl (2 and 4% (w/v)) and vacuum impregnation (VI) (150, 200, 250, and 300 Pa) on the quality parameters (water uptake, elongation ratio, visual color, and texture), tocols, γ-oryzanol and phenolic compounds of parboiled rice. Parboiling with NaCl and VI resulted in increased lightness and higher concentrations of bioactive compounds than rice parboiled by the traditional method. The highest concentration of tocopherols, γ-oryzanol, and phenolic acids (syringic, and ferulic acids) were obtained from parboiled rice with NaCl concentration at 2% (w/v) and VI at 250 and 300 Pa. As the NaCl concentration and VI levels increased the hardness L*, b* and ΔE values also increased, but the a* value and water uptake decreased. Results suggested that NaCl–VI soaking was observed to be an effective method for parboiling which promoted the visual color and enhanced the concentration of bioactive compounds in the parboiled rice.