Cereal Chem. 73 (2):284-289 |
Analytical Techniques and Instrumentation
Temperature of Liquid Contents in RVA Cans During Operation (1,2).
J. L. Hazelton (3,4) and C. E. Walker (3). (1) Presented in part at the AACC 79th Annual Meeting, Nashville, TN, October, 1994. (2) Published as contribution 95-505-J, Kansas Agricultural Experiment Station. (3) Department of Grain Science and Industry, Kansas State University, Manhattan 66506-2201. (4) Corresponding author. Phone 913/532-6161. Fax: 913/532-7010. Accepted December 22, 1995. Copyright 1996 by the American Association of Cereal Chemists, Inc.
The Rapid Visco-Analyser (RVA) normally does not indicate the actual temperature inside the sample can during operation, but rather that of the heated block. Sample cans were modified by incorporating a thermocouple that was immersed in the contents, and its temperature could then be monitored during operation. Three different starch types and four temperature profiles of differing ramping rates were used. It was found that the actual paste temperature lagged behind the block temperature, and the lag was a function of the heating/cooling rate and the apparent peak viscosity of the starch sample. A second-order multiple-regression equation (r = 0.94) was developed to predict that lag. The results can be used to predict the actual liquid temperature for any given point on the pasting curve.