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An intercomparison of the AACC hardness score based on measurement of reflectance at 1680nm and 2230nm has shown that its repeatability and reproducibility are proportional to the score. A linear relationship between hardness score and grain moisture content was confirmed for hard but not for soft wheat varieties. For both hard and soft varieties, the hardness score was found to increase with increasing grain protein content but this effect was not consistent across two different growing seasons.
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Brown et al. (1993) studied this question.
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