Abstract
Barley (Hordeum vulgare L.) is a healthy grain because of its high content of dietary fibre and phenolic compounds. It faces periods of high temperature during grain filling, frequently reducing grain weight. Heat stress may also affect some of the bioactive compounds present in the grain. To produce quality grains that provide nutritional and health benefits, it is important to understand the effect of environmental stresses on the quantity and quality of bioactive compounds. We have studied the effect of post-anthesis thermal stress on barley bioactive compounds and antioxidant capacity under Mediterranean field conditions during two consecutive growing seasons in four barley genotypes. Thermal stress affected grain weight and size and changed the relative composition of bioactive compounds. The relationship between heat stress and grain β-glucans and arabinoxylans content was indirect, as the resulting increases in concentrations were due to the lower grain weight under stress. Conversely, heat stress had a significant direct impact on some phenolic compounds, increasing their concentrations differentially across genotypes, which contributed to an improvement in antioxidant capacity of up to 30%. Post-anthesis thermal stress had a significant effect on β-glucans, arabinoxylans, phenolic compound concentration and antioxidant capacity of barley grains. Final grain quality could, at least partially, be controlled in order to increase the bioactive concentrations in the barley grain, by cultivation in growing areas prone to heat stress. Late sowings or late flowering genotypes could also be considered, should a premium be implemented to compensate for lower yields. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Highlights
Barley (Hordeum vulgare L.) is the fourth most abundant cereal in the world, being well adapted against extreme environmental conditions.[1]
Our results showed that the arabinoxylan concentration in barley grain was apparently affected by thermal-induced stress; covariance analysis showed that any difference in arabinoxylans detected disappeared once grain weight (GW) was introduced as covariable in the model (Table 1)
In the case of ⊎-glucans and arabinoxylans, the relationship between heat stress and their content was indirect because the resulting increases in concentrations were due to the lower GW under stress
Summary
Barley (Hordeum vulgare L.) is the fourth most abundant cereal in the world, being well adapted against extreme environmental conditions.[1]. Barley is a good source of bioactive compounds, components with potential health-promoting effects, such as ⊎-glucans, arabinoxylans, phenolic compounds (PC), vitamin E (tocols), sterols and folates.2 ⊎-Glucans and arabinoxylans are the major non-starch polysaccharides present in cell walls of the barley grain. ⊎-Glucans are polymers of ⊎-D-glucose with glycosidic linkages (1,4) and (1,3) They are related to several positive health effects, such as maintaining normal blood cholesterol levels, reduction of blood glucose after meals,[3,4] and improving the responsiveness of the immune system against infectious diseases, inflammation and some types of cancer.[5] Arabinoxylans consist of (1,4)-⊎-linked xylopyranosyl residues, being the second most abundant barley cell wall polysaccharide. Barley (Hordeum vulgare L.) is a healthy grain because of its high content of dietary fibre and phenolic compounds. To produce quality grains that provide nutritional and health benefits, it is important to understand the effect of environmental stresses on the quantity and quality of bioactive compounds
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