Validation of phytosterol analysis by alkaline hydrolysis and trimethylsilyl derivatization coupled with gas chromatography for rice products

Abstract

In this study, the alkaline hydrolysis and trimethylsilyl derivatization method coupled with gas chromatography-flame ionization detection was validated for phytosterol analysis and then applied for determination of major phytosterols (β-sitosterol, campesterol, and stigmasterol) in rice products highly consumed in Asian countries. Recoveries of three phytosterols from brown rice, rice bran oil and standard reference material-3251 were 87.6–104.4%, 87.7–107.6%, and 92.6–99.1%, respectively, showing good accuracy of analysis. Excellent precision of phytosterol analysis was achieved from repeatability (RSD <4%), reproducibility (RSD <8%) and HorRat ratio (0.3 ≤ HorRatr/HorRatR ≤ 1.0). Limit of quantitation of phytosterol analysis was 0.08–0.09 mg/100 g, showing high sensitivity of analysis. The total phytosterol contents (sum of major phytosterols) of rice products ranged from 18.88 to 1375.47 mg/100 g, which was high in the order of rice bran oil, rice germ, brown rice, rice with large germ, white rice and puffed rice. β-Sitosterol was the most predominant phytosterol in all rice products, which composed about 58.4–63.6% of the total phytosterols. White rice showed much lower phytosterol levels than brown rice and rice bran oil. However, it could be a good source of phytosterols because of the quantity daily consumed.