Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2007
Publication Date: 6/18/2008
Citation: Morris, C.F., Bettge, A.D., Pitts, M.J., King, G.E., Pecka, K., Mccluskey, P.J. 2008. The compressive strength of wheat endosperm: Comparison of endosperm 'bricks' to the single kernel characterization system. Cereal Chemistry 85(3):359-365.
Interpretive Summary: An understanding of wheat kernel hardness (texture) is important for determining the processing and end-use quality of wheat. A previously developed device was used to prepare tiny brick-shaped specimens from the endosperm of individual kernels of wheat. These bricks were subjected to compression testing. Material engineering properties were analyzed. Results on kernel hardness using the endosperm brick measurement system were compared with those obtained using the Single Kernel Characterization System 4100 Hardness Index (SKCS HI). The two systems were in general agreement regarding the classes of soft, hard, and durum wheat. However, each seemed to characterize hardness in slightly different ways. Based on the variation obtained using the endosperm bricks, the SKCS appeared to be performing well. Given the inherent variation in kernel properties, neither system may be able to correctly classify all wheat kernels according to hardness class. However, with some improvements, better classification may potentially be achieved.
Technical Abstract: The three major classes of endosperm texture (“grain hardness”) of soft and hard common, and durum wheat represent and define one of the leading determinants of the milling and end-use quality of wheat. Although these three genetic classes are directly related to the Hardness locus and puroindoline gene function, much less is known about the kernel-to-kernel variation within pure varietal grain lots. Measurement of this variation is of considerable interest. The objective of this research was to compare kernel texture as determined by compression failure testing using endosperm ‘bricks’ with results of whole-kernel hardness obtained with the Single Kernel Characterization System 4100 Hardness Index (SKCS HI). In general terms, the variation obtained with the SKCS HI was of similar magnitude to that obtained using failure strain and failure energy of endosperm brick compression. Objective comparisons included frequency distribution plots, normalized frequency distribution plots, ANOVA model R2’s and coefficients of variation. Results indicated that compression testing and SKCS HI similarly captured the main features of texture classes but also reflected notable differences in texture properties among and within soft, hard and durum classes. Neither brick compression testing nor the SKCS HI may be reasonably expected to correctly classify all individual kernels as to genetic texture class. However, modest improvements in correct classification rate or, more importantly, better classification related to end-use quality may still be achievable.