|Delwiche, Stephen - Steve|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2000
Publication Date: 3/1/2001
Interpretive Summary: Recent advances in the understanding of the fundamental physical properties of wheat and its mode of breakage during milling have shown that considerable variation occurs in the mechanical strength of endosperm from different varieties and from different kernels of the same variety. It has further been demonstrated that the properties of a bulk sample can be predicted from those of individual kernels within the sample. In the laboratory of one of the authors, fundamental measures of the compressive strength properties (such as maximum stress before crumbling or break, the energy input to maximum stress, and the slope of the stress vs. displacement loading response) were recently performed. Although this probably represents the best description of physical strength of wheat endosperm, and hence is useful to the understanding of milling operations, the procedure is very laborious and time consuming. The current study examines the statistical relationships between the abovementioned fundamental strength properties and the readings that can be obtained from a commercial mechanically-based device that records the resistive force to crushing of individual kernels. The results indicate that by use of three terms from the commercial device, strength properties can be estimated with very good accuracy. This could open the way to novel means of characterizing wheat milling quality for grain segregation and mill intake.
Technical Abstract: A study was conducted to better understand the relationship between hardness of wheat and the compressive strength properties of wheat endosperm. Wheat kernels from the National Institute of Standards and Technology's Reference Material No. 8441 were characterized for physical strength by uniaxial compression and by a specialized commercial wheat hardness measurement instrument, known as the Single-Kernel Wheat Characterization System (SKCS). Compressive strength measurements (maximum stress, work to maximum stress, and modulus of elasticity) were performed on machined endosperm specimens. All possible one, two, and three term equations involving the SKCS measurements, kernel weight, peak force, area of the crush force profile, and an exponential constant term from the generalized Gompertz function (used to describe the distribution of force readings collected during the crushing of a kernel), were examined for their ability to predict each compressive strength property. Three terms (weight, area, and the Gompertz function constant) were sufficient to predict any of the compressive strength properties (R >= 0.94). The Gompertz function term B, from the expression Y = A**(B**X), had the strongest effect in the prediction of compressive strength but the inclusion of kernel weight was necessary to correct for the effect of weight on the SKCS crush force profile. These results indicate that the SKCS may provide a simpler, practical method for estimating wheat endosperm compressive strength than mechanical testing of machined endosperm specimens which is difficult and time consuming.