Changes in the content and composition of vitamin E in damp barley stored in airtight bins

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AbstractThe effect of airtight storage on the content and composition of vitamin E was studied in damp barley at 20 and 28% moisture. Airtight storage with an external supply of carbon dioxide was compared with conventional airtight storage with or without an expansion sack. In two additional models, the grain was also treated with 1% ammonia (NH3). The tocopherols and tocotrienols in the grain were analysed using high pressure liquid chromatography with fluorescence detection. The changes in vitamin E during airtight storage were determined by the moisture content of the barley. In barley at 20% moisture, the vitamin E content increased until mid‐April and after 10 months the final levels were similar to those at harvest (55–65 mg kg−1) except in the bin treated wih ammonia. In barley at 28% moisture, vitamin E breakdown processes prevailed from the beginning of airtight storage and led to an unsatisfactory level of this vitamin in the grain. In barley, α‐tocotrienol was clearly the dominating isomer. The relative distribution of the isomers in barley at 20% moisture was stable during the airtight storage. For 28% moisture barley in most of the experimental models, the fraction of tocopherol isomers increased at the cost of the tocotrienols. It was concluded that the higher moisture content and a lower pH apparently favoured saturation of the side chains of the trienols. Treatment of barley with 1% ammonia gas resulted in a general decrease in the total vitamin E content and a simultaneous increase in the relative fraction of α‐tocotrienol. Therefore, α‐tocotrienol appeared to be more resistant to ammonia treatment than are the other isomers. For barley at 20% moisture content, the type of silo arrangement had hardly any effect on the vitamin E concentration or on the proportions of the isomers. For the barley at 28% moisture content, an external supply of CO2 appeared to have a preservative effect on vitamin E content.