Vitamin A is rapidly degraded in retinyl palmitate-fortified soybean oil stored under household conditions.

Oil fortification with retinyl palmitate is intended to lower the prevalence of vitamin A deficiency in populations at risk. Although the stability of vitamin A in vegetable oil has been shown to depend on environmental factors, very little information is known about the stability of vitamin A in preoxidized vegetable oils. The present study investigated the stability of retinyl palmitate in mildly oxidized (peroxide value < 2 mequiv O2/kg) and highly oxidized (peroxide value > 10 mequiv O2/kg) soybean oil stored under domestic and retail conditions. Soybean oil was filled in transparent bottles, which were exposed to cold fluorescent light at 22 or 32 °C for 56 days. Periodic oil sampling increased the headspace, thereby mimicking consumer handling. Loss of retinyl palmitate in soybean oil by a maximum of 84.8 ± 5.76% was accompanied by a decrease of vitamin E by 53.3 ± 0.87% and by an increase of the peroxide value from 1.20 ± 0.004 to 24.3 ± 0.02 mequiv O2/kg. Fortification of highly oxidized oil with 31.6 IU/g retinyl palmitate led to a doubling of the average decrease of retinol per day compared to fortification of mildly oxidized oil. In conclusion, oil fortification programs need to consider the oxidative status of the oil used for retinyl palmitate fortification.

Cold fluorescent light as major inducer of lipid oxidation in soybean oil stored at household conditions for eight weeks.

Light, temperature, and oxygen availability has been shown to promote rancidity in vegetable oils. However, the contribution of each of these environmental factors to lipid oxidation in oil stored under household conditions is not known. We aimed to identify the major inducer of oxidative deterioration of soybean oil stored at constant (67.0 mL) or increasing (67.0-283 mL) headspace volume, 22 or 32 °C, with or without illumination by cold fluorescent light for 56 days by means of fatty acid composition, peroxide value, formation of conjugated dienes, lipid radicals, hexanal, and the decrease in the contents of tocopherols. Soybean oil stored in the dark for 56 days showed an increase of the peroxide value by 124 ± 0.62% (p = 0.006), whereas exposure of the oil to light in a cycle of 12 h light alternating with 12 h darkness for 56 days led to a rise of the peroxide value by 1473 ± 1.79% (p ≤ 0.001). Little effects on the oxidative status of the oil were observed after elevating the temperature from 22 to 32 °C and the headspace volume from 67.0 to 283 mL during 56 days of storage. We conclude that storing soybean oil in transparent bottles under household conditions might pose an increased risk for accelerated lipid oxidation induced by exposure to cold fluorescent light.