Evaluation of the effect of heat treatment on the biological value of vitamin A fortified soybean oil

Abstract From the public health point of view, fortification with vitamin A of common edible vegetable oils is an important step towards the improvement of vitamin A status of populations in developing countries. Our recent study in Brazil has clearly shown that retinyl palmitate added to refined soybean oil remains stable during commonly used storage and cooking procedures and that fortification of commercial vegetable oils is feasible in Brazil and possibly in many other developing countries which principally use vegetable oils as a source of fat in their diet. The objective of this study was to investigate the biological value of vitamin A fortified soybean oil which has been subjected to various heat treatments similar to those encountered during cooking by boiling at 100°C and during repeated deep frying at 170°C. A standard rat bioassay procedure was used and evaluations were carried out based on food intake, weight gain, and levels of vitamin A in plasma and liver of test animals. The results of this study support our previous findings and indicate further that vitamin A palmitate in fortified soybean oil retains 100% of its biological value during cooking procedures requiring boiling at 100°C for about 20 minutes and that the biological value of vitamin A fortified soybean oil is reduced by about 50% after repeated use (4 times) of the same oil for deep frying at 170°C. Further studies are needed to confirm these findings in humans.