Effect of long-term storage on the free and esterified carotenoids in durum wheat (Triticum turgidum conv. durum) and tritordeum (× Tritordeum Ascherson et Graebner) grains

•Long-term storage affects carotenoids in durum wheat and tritordeum grains.•Total carotenoid content decreased according first-order degradative kinetic model.•Carotenoid retention was higher in tritordeum than durum wheat.•Esterified xanthophylls were more stable than the free ones.•Xanthophyll esterification can be promoted by environmental conditions.

The effect of long-term storage on the carotenoid composition in durum wheat and tritordeum grains was studied. Total carotenoid (mainly lutein) content decreased according to a temperature dependent first-order degradative kinetic model. The carotenoid retention was similar in both genotypes at the lower temperatures (71-73% at − 32 °C, 70% at 6 °C and 55-56% at 20 °C), whereas at the higher temperatures the pigment retention was higher in tritordeum (42% at 37 °C; 10% at 50 °C) than durum wheat (23% at 37 °C; 1% at 50 °C), probably due to the greater proportion of esterified xanthophylls. A clear difference between free and esterified pigments was observed, with smaller losses and slower degradation (higher stability) observed for the latter. The xanthophyll esterification process was highly specific and had a significant effect on the carotenoid stability according to the fatty acids involved in the esterification and their position on the lutein molecule. The results were consistent with a degradation process in which the carotenoid behavior is influenced by the chemical structure. Xanthophyll esterification can be promoted by environmental conditions, regardless of the cereal genotype, and is a powerful tool to modulate the carotenoid profile in cereals.

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