Production of Rice Bran Oil with Light Color and High Oryzanol Content by Multi‐stage Molecular Distillation

Abstract

AbstractColor is regarded as an important quality parameter for rice bran oil (RBO). Nevertheless, numerous grade‐three and grade‐four RBOs with dark color are currently available in the Chinese market. These oils are usually produced by steam refining and exhibit a mahogany color, which is undesired by customers. Here, we describe the development of a new industrially viable refining method based on multi‐stage molecular distillation (MMD), through which decoloration and fractionation of grade‐four RBO were accomplished, and four kinds of products, pigment oil, semi‐refined oil‐I (SRO‐I), semi‐refined oil‐II (SRO‐II), and semi‐refined oil‐III (SRO‐III), were obtained. The pigment oil was hazy and mahogany colored, containing 84.84 % non‐triacylglycerols, mainly pigments, tocopherols, and free fatty acids. SRO‐I was hazy and orange, containing 20,563 mg/kg of oryzanol (accounting for 77–82 % of raw oil) and was 28.68 % of non‐triacylglycerols. In particular, higher content of monounsaturated triacylglycerols, diunsaturated triacylglycerols and non‐triacylglycerols was responsible for the haze. SRO‐II and SRO‐III had a clear yellow appearance and a non‐triacylglycerol content <1.5 %. These semi‐refined oils were mixed directly after MMD and further refined by mild deacidification and winterization to obtain fully refined oil, which met the requirements of commonly used standards. Notably, the final oil exhibited light color and retained nearly 80 % of the oryzanol of raw oil. The yield of final oil reached 80–85 % through the entire refining process.