|Pecka, Kameron - USDA-ARS WWQL|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 19, 2006
Publication Date: January 15, 2007
Repository URL: http://hdl.handle.net/10113/18296
Citation: Morris, C.F., Pecka, K., Bettge, A.D. 2007. Note: A device for the preperation of cereal endosperm bricks. Cereal Chemistry 84:67-69. Interpretive Summary: The objective of this paper was to produce a geometrically defined subsample of the endosperm as opposed to studying the whole kernel. The authors have devised and constructed a device for preparing wheat (or cereal) endosperm bricks that eliminates the need for adhesive paper and glue to hold specimens during their preparation. The have used the described device (termed kernel sander) to prepare hundreds of bricks of various wheat (Triticum aestivum, and T. turgidum var. durum) cultivars, including vitreous and nonvitreous (mealy) kernels selected from individual grain lots. The kernel sander is comprised of two parts, the base (lower) and sander (upper) components. The outstanding features of the base include a series of channels to hold the specimens during their machining, and side rails that support and guide the sander.
Technical Abstract: The study of cereal chemistry has been advanced by the analysis of the material properties of cereal endosperm. In particular, the study of wheat (Triticum sp. L.) endosperm hardness (kernel texture) has been a topic of intense interest for the past ca. 100 years (Pomeranz and Williams 1990, Morris 2002). One of the first recorded devices for measuring wheat kernel texture was that of Roberts (1910) which determined the force required to crush individual kernels. There are two reasons why the assessment of kernel texture in wheat, in particular, is of great interest: 1) wheat exhibits distinct classes of kernel texture, namely soft, hard and durum, and 2) the differences in kernel texture among these classes has a profound effect on flour milling, starch damage, particle size distribution, water absorption and end-use quality (Morris and Rose 1996, Morris 2002). As we will describe, our objective was to produce a geometrically-defined sub-sample of the endosperm, as opposed to studying the whole kernel. The measurement of wheat kernel texture has been largely empirical because kernels and endosperm are difficult to work with due largely to their diminutive size. Current methods (AACC International 2000) such as Near-Infrared Reflectance (39-70A), Particle Size Index (55-30), and Single Kernel Characterization System (55-31) provide measurements in arbitrary unit-less proportions or scales. Generally, to obtain objective measures of material properties in ‘universal’ units of force, work, etc., complex geometries must be simplified, and in the case of wheat, the bran, germ and pigment strand should also be eliminated. A few researchers have been successful in achieving this goal. Glenn of the USDA developed a method of “turning” on a lathe endosperm cylinders of defined geometry, and then subjecting them to testing in both compression and tension (Glenn et al 1991, Jolly 1991, Jolly et al 1996, Delwiche 2000, Osborne et al 2001, Dobraszczyk et al 2002). This same technique was studied in the senior author’s lab and found to be exceedingly tedious; the centering of the kernel “cheek” on the lathe stub was particularly problematic. Haddad, Abecassis and co-workers (Haddad et al 1998, 1999, 2001; Samson et al 2005) eliminated the problems associated with “turning” cylinders, by preparing via sanding rectangular parallelepipedal test samples. Here we term such specimens “bricks”. We have devised and constructed a similar device that eliminates the need for adhesive paper and glue to hold specimens during their preparation (see Haddad et al 1998, Fig. 2). Further, one of the processing steps in the technique described by Haddad et al (1998) (see Fig. 3), viz. “Two machined half-grains are placed between two sheets, and a wedge is set at height l of the extremities of the sheets.” has been eliminated. We have used the device described here to prepare hundreds of bricks of various wheat (T. aestivum and T. turgidum var. durum) cultivars, including vitreous and non-vitreous (mealy) kernels selected from individual grain lots. These bricks are amenable to material property analysis using common instrumentation such as the TA-XT2i in compression mode. Our experience to date indicates a very low rate of “aberrant” failure, which could be ascribed to cracks or other “defects”, of the bricks so prepared and tested, on the order of ca. 1-2%.