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Application of the Rapid Visco Analyzer (RVA) as an Effective Rheological Tool for Measurement of β-Glucan Viscosity

¹Guelph Food Research Centre, Agriculture and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario, Canada, N1G 5C9. ²University of Alexandria, Faculty of Agriculture, Department of Food Science and Technology, El-Shatby 21545, Alexandria, Egypt. ³Cereal Research Centre, Agriculture and Agri-Food Canada, 196 Innovation Drive, Winnipeg, Manitoba, Canada, R3T 2N2. ⁴Corresponding author. Phone: (519) 780-8019. E-mail: susan.tosh@agr.gc.ca

The physiochemical characteristics of β-glucan in oat and barley foods can affect human physiological response. A method for continuous measurement of β-glucan viscosity with a Rapid Visco Analyzer (RVA) was developed to overcome the complexity of the common protocols based on in vitro digestion methods. The effects of several parameters on viscosity and solubility were considered. Oat cereal foods showed different RVA viscosity profiles depending on their physiochemical characteristics. Products high in starch exhibited a high initial viscosity that was reduced by α-amylase action, whereas products with low amounts of starch exhibited a slow increase in viscosity. The viscosity of all samples reached a plateau in the viscosity curve after 1–2 hr, which is the key for obtaining reproducible results. Optimum digestion condition was achieved using sodium phosphate buffer (pH 6.9) and 1% β-glucan dispersion at 37°C and 160 rpm. A particle size of <0.6 mm gave more consistent viscosities than did larger particles without affecting the solubility of β-glucan. Pancreatin and α-amylase concentrations affected the viscosity profile by influencing the digestion rate of protein and starch in the samples, but pepsin had limited influence at pH 6.9. Highly significant Pearson correlation between the in vitro digestibility protocol and RVA methods was achieved, indicting that the developed method could be used as an effective alternative for measurement of β-glucan viscosity.