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The implications of frequently encountered grading factors on the processing quality of durum wheat

2. Introduction

Wheat physical condition is influenced by environmental conditions during growth and harvest. Some of the commonly encountered forms of environmental damage can have serious implications on wheat processing quality (Dexter and Tipples 1987, Dexter 1993). Therefore, most wheat producing countries market wheat on the basis of physical attributes, as determined by grading and classification systems. An ideal system strikes a balance between the interests of wheat processors and producers. Wheat grade standards should be set to ensure segregation according to processing potential, while allowing the maximum possible proportion of wheat in the top grades to maximize return.

In Canada the Canadian Grain Commission (CGC) is responsible for setting grade standards for all grains and oilseeds. CGC wheat grade standards are set on a scientific basis so that physical damage permitted accurately reflects processing implications. An ongoing collaborative research effort by the Grain Research Laboratory (GRL) and Industry Services divisions of the CGC ensures that grade standards are fair and effective.

Recently we reviewed the effects of commonly encountered grading factors on common wheat end-use quality (Dexter and Edwards 1998). The implications of grading factors on the processing potential on durum wheat merit separate discussion, because quality implications are different than common wheat (Feillet and Dexter 1996). Grading factors associated with surface discoloration of kernels are more important for durum wheat because bright speck-free semolina is essential to give the aesthetic appearance required for successful marketing of premium pasta products. This article summarizes the results of recent research on frequently encountered grading factors that affect the safety and processing value of durum wheat, and assesses the significance of each grading factor on semolina milling and pasta quality.