Abstract
High temperatures at the end of the season are frequent under Mediterranean conditions, affecting final grain quality. This study determined the deposition patterns throughout grain filling of dry matter, dietary fiber, phenolic compounds and antioxidant capacity for four barley genotypes under two contrasting temperatures. Deposition pattern for dietary fiber followed that of grain weight. Genotypic differences for duration were more significant than for rate. Anthocyanins followed a second-degree polynomial pattern, reaching a maximum before grain maturation. Free and bound phenols decreased as grain developed, suggesting that they are synthesized in early stages. Rate of bound phenols deposition was more sensitive to genotypic changes. Overall, antioxidant capacity decreased over time; the decay being less steep under stress for all genotypes. Heat stress negatively affected grain weight. It did not alter the profile of β-glucans and arabinoxylans deposition but positively changed the accumulation of some phenolic compounds, increasing the antioxidant capacity differentially across genotypes. These results support the growing of food barley in high-temperature stress-prone areas, as some bioactive compound and antioxidant capacity will increase, regardless of the smaller grain size. Moreover, if a market develops for food-barley ingredients, early harvesting of non-mature grain to maximize antioxidant capacity should be considered.
Highlights
IntroductionΒ-glucans are major non-starch polysaccharides present in cell walls
Barley (Hordeum vulgare L.) grain contains a variable amount of bioactive compounds with known health-promoting properties, such as dietary fiber (β-glucans, arabinoxylans, cellulose, lignin, and lignans), phenolic compounds, tocols, sterols and folates [1]
Barley cultivated in a heat-stressed area, under Mediterranean conditions, is a valuable source of dietary fiber, phenolic compounds and antioxidant capacity for cerealbased healthy food products
Summary
Β-glucans are major non-starch polysaccharides present in cell walls They are linked to the maintenance of normal blood cholesterol levels [2] and the reduction of blood glucose after meals [3], as well as improving the responsiveness of the immune system to infectious diseases, inflammation and some types of cancer [4]. Phenolic compounds are a large class of secondary plant metabolites, which can be found free or bound to compounds in the cell wall of the barley grain. Phenolic compounds, with their strong antioxidant power, are associated with the reduction of cardiovascular disease, inflammation and a diversity of cancers [6]. Interest in the health benefits of barley has led to an increased focus on these bioactive compounds in mature grain [7,8]
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