No abstract

Cereal Chem. 76(1):150-158The effect of proteolytic enzymes, associated with Fusarium head blight, on wheat storage proteins and dough functionality was studied. Fusarium damaged kernels (FDK) and sound kernels were hand-picked from F. graminearum Schwabe and F. avenaceum (Fr.) Sacc. infected samples of bread and durum wheat. Scanning electron microscopy revealed significant degradation of endosperm protein in FDK. Storage proteins from FDK and sound kernels were analyzed by SDS-PAGE, RP-HPLC, and SE-HPLC. Total storage protein was lower in FDK but no significant qualitative differences in protein were detected by either RP-HPLC or SDS-PAGE. SE-HPLC was used to follow the hydrolysis of wheat storage protein by proteolytic enzymes found in FDK and a pure culture of F. graminearum. Selective inhibition of proteolytic activity by p-chloromercuribenzoate, and not soybean trypsin inhibitor or iodoacetic acid, suggests that the F. graminearum protease is an alkaline protease. Farinograph and extensigraph curves showed that the presence of FDK decreased dough consistency and resistance to extension. The presence of FDK in flour resulted in a substantial reduction in loaf volume. The loss of dough functionality and loaf volume potential was attributed to the presence of fungal proteases.

Fiber-rich fractions (FRF) derived from roller milling of waxy (W) and high amylose (HA) starch hull-less barley genotypes were evaluated for suitability as functional ingredients in fresh and dried white salted (WSN) and fresh yellow alkaline (YAN) noodles. FRF-W and FRF-HA both contained over 300 g kg −1 dietary fiber, and over 200 g kg −1 of β-glucans. Replacement of 250 g kg −1 Canada Prairie Spring White (cv AC Vista) wheat patent flour with the FRF posed no problems in noodle processing, although water absorption had to be substantially increased. All three noodle types enriched with the FRF were significantly darker and contained more brown specks than the wheat flour control noodles. The presence of the FRF reduced cooking time of fresh YAN and WSN by ∼50%. The addition of FRF improved cooked YAN texture, as evidenced by increased firmness and resistance to compression. FRF-enriched fresh WSN were comparable to the wheat flour control noodles for those parameters, whereas enrichment of dry WSN by FRF imparted less firmness and less chewiness. FRF-enriched fresh YAN and WSN offer consumer convenience due to shorter cooking time, improved nutritional quality and acceptable cooking quality. These features might make FRF-enriched noodles sufficiently attractive to health-conscious consumers to overcome the negative effects of color and appearance 

Cereal Chem. 76(5):638-645Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from <5% for the strongest least extensible cultivar to >25% for the weakest cultivar, with a coefficient of variation among replicates of <10%. Storage modulus (G′) at 2 Hz ranged from ≈7,000 Pa for the weakest cultivar to >16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of <6%. Tan δ (G′′/G′) values were ≈0.4 for the strongest versus >0.5 for the weakest cultivars, indicating the larger contribution of the elastic component in the strong cultivars. The rheometer allows discrimination of durum wheat cultivars of varying gluten strength while requiring less sample than traditional physical dough testing techniques.

Ten durum wheat cultivars harvested in Manitoba in 1995, which were downgraded primarily because of fusarium‐damaged (FD) kernels, were subjected to mycological tests and evaluated for semolina milling and pasta‐making quality. Fusarium graminearum was the primary fungus infecting kernels. The ratio of FD to deoxynivlaenol (DON) level varied slightly among cultivars but was generally near unity. Retention of DON in semolina was about 50%. FD had a negative impact on kernel weight and test weight, resulting in lower semolina yield. Semolina ash content and bran specks were not affected by FD, but semolina became duller and redder. FD had no effect on protein content, but gluten strength was weaker probably due to a lower proportion of glutenins as shown by reversed‐phase high‐performance liquid chromatographic analysis of sequentially extracted gluten proteins. The influence of FD on gluten strength was not sufficient to alter pasta texture. FD had a strong adverse effect on pasta color. Even for the least damaged cultivars, which had FD levels near the limit of 2% established for the No. 3 and No. 4 Canadian Western Amber Durum (CWAD) grades, the deterioration in pasta color was readily discernible by eye, confirming that the strict FD tolerances for premium No. 1 CWAD (0.25%) and No. 2 CWAD (0.5%) grades are warranted.