Influence of the storage time on the concentration of alpha-tocopherol and gamma-tocopherol in vegetable oils

Abstract

The alpha- and gamma-tocopherol are among the homologues of vitamin E which plays a key role as an antioxidant. The richest dietary sources of vitamin E are vegetable oils. This study aimed at evaluating the alpha- and gamma-tocopherol contents in oils from canola, sunflower, corn and soybeans, and to verify their variations after storage time. The vegetable oils were purchased at supermarkets in Natal / RN, and they were kept at room temperature and protected from light. The tests was made at different times during storage (time 0 and after 30, 60 and 90 days). The high performance liquid chromatography (HPLC) was used to determine their concentrations. The statistical analysis was performed using analysis of variance (ANOVA) test; and the differences were considered statistically significant when p < 0.05. By the end of the storage time (90 days), the alpha- and gamma-tocopherol contents showed a significant decrease of 38.7 % and 36.0 % for canola oil; 42.2 % and 22.2 % in soybean oil; 28.3 % and 29.2 % in sunflower oil; 39.0 % and 17.9 % in corn oil, respectively. The concentrations of alpha- and gamma-tocopherol in vegetable oils significantly decreased after the storage period under the conditions used in this study.