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J. F. STEFFE, Dept. of Agricultural Engineering, Michigan State University, 209 Farrall Hall, East Lansing, MI 48824-1323 and C. R. Daubert, North Carolina State University.

Years of collaborative research experience, under the auspices of a national research committee (NC-136), have lead to the evolution of a standard means of measuring the yield stress of foods using the vane method. Concepts considered in developing the standard, and the resolution of technical issues in creating firm guidelines, are discussed in this paper. The yield stress concept is presented and the difference between the static and dynamic yield stresses explained. Specifications for the many variables influencing the procedure are given: number of blades, width and diameter of vanes, sample container dimensions, angular velocity of the vane, end effect assumptions, and calculations involving both the slope and single point techniques. Low-cost rotational instruments are surveyed and various issues regarding instrument selection are summarized: torque response of soft vs hard instruments, controlled-rate vs controlled-stress testing mode, and rate of data acquisition. Future activities needed to finalize the standard are discussed.