EFFECTS OF FROST DAMAGE AND IMMATURITY ON THE QUALITY OF DURUM-WHEAT

Frost damage and immaturity were the predominant grading factors assoc iated with the 1992 Canadian durum wheat crop. Canadian Grain Commissi on grain inspectors composited samples from the 1992 durum wheat harve st survey to yield a series of sample representative on the visual lim its of frost damage and immaturity for each Canada Western Amber Durum (CWAD) wheat grade. The greater severity of frost damage and immaturi ty permitted in No. 4 CWAD and No. 5 CWAD compared to the higher quali ty milling grades was reflected by lower test weight and reduced kerne l size. End-use quality assessment of the composites verified that the CWAD visual grade standards correctly classify Canadian durum wheat. There was a gradual decrease in milling performance and spaghetti qual ity from No. 1 CWAD to No. 3 CWAD. No. 4 CWAD, which is not intended f or high quality pasta, exhibited significantly poorer quality, and No. 5 CWAD, which is a feed-wheat grade, was very poor. Severe frost dama ge and immaturity had a negative impact upon semolina milling performa nce due to the combined effects of low semolina yield, unacceptable sp eck counts, high semolina ash content, and dull semolina color. The po or refinement of semolina from severely frosted and immature durum whe at resulted in duller, browner spaghetti. However, frost damage and im maturity did not influence spaghetti cooking quality, even though a lo wer yield of wet gluten per unit protein and abnormal mixograph mixing properties indicated that glute properties had been adversely affecte d. The proportion of gliadins to glutenins declined with increasing fr ost damage and immaturity, but no qualitative differences in gluten pr oteins were apparent.