Individual and interactional effects of β-glucan, starch, and protein on pasting properties of oat flours

Seven experimental oat lines with high (6.2-7.2%), medium (5.5-5.9%), and low (4.4-5.3%) β-glucan concentrations were evaluated for contributions of β-glucan, starch, protein, and their interactions, to pasting properties of oat flours by using a Rapid Visco Analyser (RVA, Newport Scientific, Warriewood, NSW, Australia). Significant correlations (P < 0.05) between β-glucan concentration and pasting parameters of oat slurries were obtained under autolysis without 1 h of incubation, inhibition, and amylolysis. The relative decrease of viscosity after enzymatic hydrolysis of β-glucan correlated with β-glucan concentration (P < 0.05). These data demonstrated the important contribution of β-glucan to pasting. The relative decrease of viscosity after either amylolysis or enzymatic removal of protein correlated with β-glucan concentration (P < 0.1), which might be explained by the considerable contribution of the interaction of β-glucan with starch and protein, to pasting. The viscosity decrease by hydrolysis of protein was much greater than the actual viscosity remaining after hydrolysis of both β-glucan and starch, reconfirming the importance of interactions between protein and other oat components to pasting. Optimal multiple linear regression (MLR) models were generated to predict key pasting parameters in both buffer without 1 h of incubation and silver nitrate solution by using a stepwise procedure. The β-glucan concentration alone or together with the concentration of starch, rather than protein, was selected as the predictor under certain conditions. These results illustrated the major unit contribution of β-glucan, secondary unit contribution of starch, and minimal unit contribution of protein to pasting.