A Simple Measure of Kernel Hardness in Wheat¹

Abstract

ANY simple test that will aid the wheat breeder in measuring 1"\. characteristics of grain is of value in increasing the efficiency of the breeding program. In the eastern soft wheat region hard wheats are being used extensively as parents to secure resistance to various diseases and a simple test is especially needed for identifying, in the early generations, hybrid lines with soft grain. Hard wheats in general produce coarse granular flour and soft wheats fine smooth flour. The particle size index test developed by Cutler and Brinson 3 appears to differentiate varieties in a very satisfactory way so far as this character is concerned. It is slow, however. The doughball time test has also been suggested by Cutler and Worzella 4 as a measure of quality for small samples. Since the degree of granulation of a flour seems to be related to hardness of the grain, it occurred to the authors that a pearler such as is used in the inspection of barley and which has also been used for studies in the milling of parboiled rice, might be useful in estimating the hardness of wheat samples. Some preliminary trials seemed to verify this assumption and hence a more extensive investigation was planned and carried out. The results appear promising enough to justify presenting the results. MATERIALS AND METHODSThe pearler consists of an enclosed grinding stone attached to a Ys h. p. directdrive electric motor. An interval timer, a balance sensitive to o.or gram, and a set of Tyler screens completes the apparatus necessary for the pearling test.Preliminary tests were made on grain of varieties grown in field plats at the Arlington Experiment Farm, Arlington, Va. Later samples from the varieties in the uniform soft winter wheat nurseries grown at several stations in the eastern states were studied. Also, in order to obtain data with a wider range of kernel types, samples of a few winter and spring varieties grown in field plats at experiment stations in the western United States were included.The wheat was stored for two months or more prior to pearling in an ordinary seed storage room. The moisture in the grain varied between ro and r 1% and no shriveled or badly broken grain was used. The procedure used in the test was as follows:1. Approximately 100 grams of wheat were placed on a No. 6 Tyler screen held over a No. 8. After shaking a definite number of times by hand, three 20gram samples were weighed from the grain remaining on the No. 8 screen.2. A sample was placed in the pearler and the latter started and run exactly 3 minutes.

The Adaptation to Small Samples of the Pearling Test For Kernel Hardness in Wheat1

“…H. H. KRAMER AND H. R. ALBRECHT 2 T HE barley pearler has come into prominance as a measure of kernel hardness in wheat since its use for that purpose was first proposed by Taylor, Bayles, and Fifield (4) 3 in 1939. They showed that the pearling index is closely correlated with the particle size index developed by Cutler and Brinson (r), and found fair agreement between the pearling index and the fermentation time test suggested by Cutler and Worzella (2).…”

Measurement of Wheat Hardness by Seed Scarifier and Barley Pearler and Comparison with Single‐Kernel Characterization System

“…Hardness values obtained by BP were expressed as ARI instead of pearling index (PI). PI was defined by Taylor et al (1939) and calculated as percent of surface removal (or % of wheat pearled off). By definition, the two units are convertible based on the formula, ARI = 100 -PI.…”

“…NIR hardness score was calibrated by the same reference material. For hardness values obtained by BP and other abrasive-action-based equipment (such as TADD), several expressions were used including 1) pearling index (PI) or % of kernel weight pearled off (Taylor et al 1939); 2) pearling resistance index (PRI), defined as the weight of pearled grains (Obuchowski and Bushuk 1980); 3) rate constant, defined as % milling loss/min (Lawton and Faubion 1989); and 4) abrasive hardness index (AHI), defined as time (sec) required to pearl 1% off (Reichert et al 1981). In this study, hardness values measured by SS and BP are expressed as % of remaining kernel weight after a given time of abrading and defined as abrasion resistance index (ARI).…”

“…It is based on measurement of abrasion resistance. The method was first developed by Taylor et al (1939), who used a Strong-Scott barley pearler (BP) to abrasively mill wheat. Essentially the method consists of placing a weighed amount of wheat in the pearler and calculating percent-ages of outer layer removal (defined as the pearling index) after a given time of pearling.…”

A Study of Quality, as Measured by the Pearling Test, in Crosses between Hard and Soft Wheats1

“…The pearling test, originated by Taylor, Bayles, and Fifield (12) measures the kernel hardness of wheat by subjecting the grain to the abrasive action of a revolving stone in a commercial barley pearler. High correlations between results of the pearling test and tests measuring gluten strength in soft wheats have been reported by Bayfield et al ( 2, 3), Morris et al (9) and Bowman et al (5).…”