Interaction between barley cultivars and growth temperature on starch degradation properties measured in vitro

Eight 2-row barley cultivars (waxy, normal and high amylose) were grown in controlled environment chambers at 9, 12, 15, 18 and 21 °C until maturity. The flour samples were analysed for total starch content, mixed-linked β-glucan content (total, soluble and insoluble), content of protein, fat and neutral detergent fibre (NDF) in addition to the amount of total, free and lipid complexed amylose. A non-ruminant in vitro method was used to analyse the degradation of starch (5–10–15–30–60–90–120–240 min incubation times) from the samples grown at different temperatures. A partial least square (PLS) regression model was made to highlight the flour characteristics that influenced the starch degradation the most. The waxy starches were degraded faster and to a higher extent than the normal and high amylose starches at all incubation times. At short incubation times the high amylose was not degraded as rapidly as the normal ones, but as incubation time increased, they changed range, and at 240 min incubation time the normal genotypes were degraded to a lesser extent than the high amylose. The amylose–amylopectin ratio was most important regarding starch degradation. The growth temperature influenced the starch degradation considerably; the degradation was negatively correlated to the growth temperature. The PLS regression model showed that the content of total and insoluble β-glucans became increasingly important as the incubation time increased.