Re-analysis of vitamin A values of selected Malaysian foods of animal origin by the AOAC and HPLC methods

Abstract

Vitamin A values of 40 foods of animal origin from various food groups and several processed foods were studied using a newly developed, reverse-phase, high-performance liquid chromatography (HPLC) method. Carotenoids and retinol were separated isocratically on an octadecylsilane (C 18) column using a ternary mixture of acetonitrile, methanol and ethyl acetate. Two detectors connected in series were used to detect and quantify carotenoids simultaneously at 436 nm and retinol at 313 nm in a single chromatographic run. All samples were also simultaneously determined using the Association of Official Analytical Chemists (AOAC) open-column (alumina) chromatographic method. The AOAC method was found to give significantly higher retinol contents in the foods studied, due to the presence of other pigments that gave falsely elevated absorbance readings. Although there was no statistically significant difference in β-carotene contents given by the HPLC and AOAC methods, there were more foods with higher results given by the latter method. β-Carotene contents were generally low; only in seven foods did the carotene contribute more than 50% of the total vitamin A value. The contribution of other provitamin A carotenoids is probably insignificant. Thus, the total vitamin A activity of these foods was mainly contributed by retinol. The proposed HPLC method has been shown to be applicable to the determination of carotenoids in vegetables and fruits, as well as to the determination of carotenoids and retinol in foods of animal origin.