Owing to limited rainfall following germination, combined with late heavy frosts, a large portion of the 1928 wheat crop of Western Canada contained many types of frost damage together with immature and green kernels. A survey of the crop was made in the three laboratories collaborating with the Associate Committee on Grain Research with the dual object of studying the Canadian grading system as applied to frosted wheat and of securing information on the relative effects of green, immature, and frosted kernels on milling and baking quality. The study is based on 228 samples grading from No. 1 Northern to No. 6.Physical examinations showed that the percentage of sound kernels progressively decreased with a decrease in grade, with a greater relative increase in the percentage of "heavy damage" in the lower grades. Test weight per bushel also decreased. Partial correlations showed that individually the various forms of damage had only a slight effect on reducing weight per bushel, heavily frosted and immature kernels having a greater influence than bran frosted kernels.On a regrading of the samples after storage over winter, 83.3% of the samples were unchanged in grade while 13.2% received a higher grade.The mean total flour yield decreased with grade, the variability in yield being much higher within the commercial grades. Owing to the tough and fibrous nature of the middlings there was approximately a 20% increase in the time required to mill a sample of No. 5 or No. 6 wheat as compared with the statutory grades. Bran frost, heavy frost, and immature kernels are negatively correlated with flour yield and are of approximately equal importance in their effects. Weight per measured bushel and the percentage of total sound kernels are the best single indices of flour yield.Baking quality was determined in the three laboratories using either a 55% patent or a straight grade flour and baking according to the simple, bromate, malt and blend formulas. While the simple formula gave incongruous results all the others revealed that the average baking quality as measured by loaf volume, crumb color and texture decreased with grade except in the instance of grade No. 4 which was superior to No. 3 Northern. Absorption markedly increased in the lower grades. The straight grade and patent flours gave the same relative results when baked by either the simple or the bromate formula.The average responses to the differential baking tests also decreased with wheat grade, the magnitude of the individual responses being correlated with protein content. Partial correlations calculated for the response to bromate showed that both protein content and percentage of sound kernels are positively correlated with this variable.The variability in baking quality within each grade increased with decreasing grade, owing in part to variations in the percentage of sound kernels, but chiefly to variations in protein content. Protein content of wheat is the best single measure of baking quality within each grade, but is not a reliable measure when comparisons are made between grades, owing to differences in protein quality. Partial correlations showed, as in the instance of milling quality, that the various classes of visible damage need not be considered individually with regard to their effects on baking quality.The results of this study indicate that weight per measured bushel and either the percentage of total sound or hard red vitreous kernels could be used to advantage as grading factors in the commercial grades. It is concluded that the grading system in use in 1928 was applied in an efficient manner and gave a satisfactory indication of the relative quality of the various grades with the exception of the anomalous relationship between No. 3 Northern and No. 4.The variability in baking quality within grades is excessively high, particularly in the lower grades. Although variations in protein content are chiefly responsible for the lack of uniformity within grades, some improvement may be effected by restricting the variability in the percentage of total sound or vitreous kernels allowable in the various grades. The revisions in the Canada Grain Act instituted in 1930 during the progress of the investigation, are in line with the results of this study and may be expected to bring about a greater uniformity in grade characteristics.
EFFECT OF LEAF RUST ON THE YIELD OF RESISTANT WHEATS
