New barley cultivars: chemical, microstructural and nutritional aspects focusing on carbohydrates

New barley cultivars were selected to represent genotypes known to vary in their contents of protein, amylose and amylopectin and beta-glucan. The chemical composition of the cultivars was analysed focusing on dietary fibre components, especially structure and extractability. Barley cultivars, chosen with support from the chemical analyses were grown in Sweden in two years, at three locations, with three nitrogen fertilization rates. The yield and analysed variables (TKW, Bw and chemical composition) were investigated. Barley samples with different starch composition were further selected for microstructural and broiler chicken nutritional studies. The results were evaluated with analysis of variance and principal component analysis. High amylose and high amylopectin (waxy) barley have high total beta-glucan content with a very low proportion of extractable beta-glucan in the high amylose barleys. Presence of probable amounts of xylose residues branched only at O-2 was observed for water extractable arabinoxylans. A wide variation in the characteristics of the barley cultivars contributed to large effects on yield and analysed variables compared with environment and growing conditions. Calcofluor stained micrographs showed that the high amylose and waxy barleys had thicker endosperm cell walls compared with normal starch barley. Starch granule distribution in normal and waxy barley was bimodal while it was more evenly distributed in the high amylose barleys. Iodine stained micrographs revealed black medium sized starch granules indicating a high amylose content in the subaleurone layer of the covered waxy barley. Chickens fed diets based on normal starch barley weighed more and consumed more feed compared with chickens fed diets based on high amylose and waxy barley. Enzyme supplementation improved the production parameters in comparison to chickens fed diets without enzyme. Ileal starch digestibility among chickens fed the unsupplemented waxy diet was significantly lower than for birds given the corresponding normal starch diet. Micrographs and chemical analyses indicated that a high content of total and unextractable beta-glucan as in the high amylose diet render the endosperm cell walls more difficult to break down and the availability of starch and protein were delayed.