Ohmic heating-assisted extraction of anthocyanins from black rice bran to prepare a natural food colourant

Abstract

Black glutinous rice bran (Oryza sativa L.) is a potential source of the dark purple anthocyanin pigments. This study investigated some quality aspects and bioactive compounds of the colourant powder obtained from rice bran extracted by ohmic heating (OHM) assisted solvent extraction. The moisture content (MC) of the bran was adjusted to 30% and 40%. Four different levels of electric field strengths (E) of 50, 100, 150, and 200 V cm- 1 were applied. The results showed that OHM assisted solvent extraction was a promising method offering both high yield and high concentration of bioactive compounds. The solubility, aw, bulk density, and color values (L∗, C∗, and h°) of the colorant powder of all treatments were comparable. The colourant powder obtained from the bran extracted using OHM with 30% MC (E=100, 150, and 200 V cm- 1) and 40% MC (E = 50, 100, 150, and V cm- 1) had the highest level of bioactive compounds. Industrial relevance The ohmic heating was a promising technique to assist solvent extraction of anthocyanin pigment from black rice bran. The colourant powder prepared by ohmic heating assisted (CP-OHM) had higher colourant yield, anthocyanin pigments, and bioactive compounds than conventional methods. The present study suggested that ohmic heating could be applied to develop industrial production scale of natural colourants.