42-3 |
Characterization of hot cereals by yield stress using the vane method |
J. J. DEJONGH, Food Science and Human Nutrition, Michigan State University, 2100 Anthony Hall, East Lansing, MI 48824 and J. F. Steffe, Agricultural Engineering, Michigan State University, 209 Farrall Hall, East Lansing, MI 48824. Consumer complaints concerning hot cereals often relate to the texture and flow properties of the prepared product. At the present time, no objective test exists to relate the rheological behavior of hot cereals to the subjective "measurements" of a consumer when consuming the final product. Yield stress, determined by the vane method, is an effective quantitative indication of the behavior of hot cereals. The objective of this research is to develop a rheological test for hydrated hot cereal that can be used for product development and quality control in an industrial setting. Cereal was prepared according to package instructions then stirred until it was cooled down to 140°F (eating temperature). The sample was then poured into a squared container and the vane was inserted. A four-blade vane (height=0.051m, diameter=0.025m) was used in conjunction with a Haake VT550. The blade was set at a constant speed of one rpm and the torque was measured for 180 seconds. The peak torque was used to determine yield stress using standard calculations. Variables such as time, temperature, and shear history were studied in relation to how they affect the yield stress. Typical yield stresses for the four cereals sampled are displayed in the following table: 2 ½ minute Cook on Stove Cream of Wheat - 37 Pa 1 minute Oatmeal - 99Pa 2 ½ minute Malt-o-Meal - 30 Pa Instant Original Cream of Wheat - 30Pa Results show that yield stress can be used to characterize the difference in flow properties of hot cereals. The experimental protocol developed in this study can form the basis for a simple product quality test in the hot cereal industry.
Session 42, Food Engineering: Rheology and texture
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