The cereal grains: focus on vitamin E

Abstract

Tocopherols (T) and tocotrienols (T3) were analysed using HPLC and vitamin E content was calculated in selected cereal grains and their different morphological fractions. Wheat (Triticum aestivum L.) cv. Almari, barley (Hordeum vulgare L.) cv. Gregor, rye (Secale cereale L.) cv. Dańkowskie Złote, oat (Avena sativa L.) cv. Sławko and buckwheat (Fagopyrum esculentum Moench) cv. Kora were used in this study. The highest level of tocopherols was found in dehulled buckwheat and in its fraction of the endosperm with the embryo, where γ-T was found to be the main tocopherol (94.1% and 93.7% of total, respectively). α-T and β-T were the main isomers found in wheat, barley, rye and oat. β-T3 was the main tocotrienol found in wheat and oat, whereas α-T3 predominated in barley and rye. Small quantities of γ-T3 were only found in barley. No tocotrienols were found in buckwheat grains and their morphological fractions. The content of tocopherols and tocotrienols in the fractions of endosperm with embryo was 10-30% lower than in whole grain. The fraction originating from rye was the richest one in total tocols, followed by wheat and barley. Similarly, among the analysed fractions of pericarp and testa the richest fraction was that from rye, followed by wheat and barley. Extrusion cooking caused a significant decrease in tocopherols and tocotrienols, expressed in terms of biological activity of vitamin E, from 63 to 94%, depending on the cultivar examined. α-Tocopherol and α-tocotrienol were least resistant to hydrothermal processing. The remaining tocols were more stable, though the degree of their degradation reached up to 50%.

Keywords

• tocopherols
• tocotrienols
• vitamin e
• cereal grains
• morphological fractions
• hydrothermal process