Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2007
Publication Date: 2/15/2008
Citation: Liu, K. 2008. Measurement of Wheat Hardness by Seed Scarifier and Barley Pearler and Comparison with Single-Kernel Characterization System . Cereal Chemistry. 85(2):165-173
Interpretive Summary: Hardness or texture of wheat is the single most important trait that positively correlates with protein content, and determines milling properties and end-uses. However, wheat hardness has to be empirically measured and thus is largely related to how the trait is measured. There are many reported methods for measuring hardness of wheat and some other cereal grains, often based on different principles. For many years, due to simplicity and low cost, methods using a barley pearler (BP) had once been one of common bulk sample methods for determining kernel hardness. However, in recent years, newer methods such as single-kernel characterization system (SKCS) and near-infrared reflectance (NIR) spectroscopy, have gained increasing popularity. Yet, the instruments for these methods are relatively expensive and not readily available. This study was conducted with three objectives: 1) to describe a new procedure for measuring wheat hardness based on a seed scarifier (SS), another low-cost, abrasive milling device, 2) to compare the new procedure with other methods based on BP and SKCS, and 3) to investigate factors affecting hardness measurement and steps to minimize some inadequacies commonly associated with abrasive hardness measurement methods based on SS or BP. One significant finding of the study was that like barley pearler, seed scarifier can serve as a reliable yet low-cost alternative to SKCS and NIR for measuring wheat hardness when certain recommended steps are taken into considerations. Furthermore, the study provided a better understanding of different factors affecting wheat hardness, certain limitations of wheat hardness measurement by any types of instrument, and recommended procedures for method improvement based on SS or BP.
Technical Abstract: A new procedure based on a seed scarifier (SS) for measuring wheat hardness was described and investigated along with methods of barley pearler (BP) and single kernel characterization system (SKCS). Hardness measured by SS and BP was expressed as percentage of kernel weight remained after abrading and defined as abrasion resistance index (ARI). For a given sample weight, increasing abrading time decreased ARI, but improved the ability to differentiate variation among samples. The effect of sample moisture was also statistically significant. For improved performance of SS and BP, based on distinct patterns of relationships between surface removal rates and surface removal levels among soft and hard wheats, a combination of parameters that produces ARI values in the range of 80-20, and a run for a set of reference material are recommended. Differences in measured hardness values by SS, BP and SKCS existed within a wheat group, but they were very much method-dependent. Nevertheless, all methods were able to differentiate variations between soft and hard wheat groups. Due to their low-cost, durability, simplicity, repeatability and aforementioned ability, SS and BP, although limited by lack of standardization and calibration procedures, can still be useful for grain hardness measurement, particularly when and where instruments for contemporarily popular methods, such as SKCS and near-infrared reflectance (NIR) spectroscopy, are not readily available.