Effects of gamma-irradiation of wheat on gluten proteins

The effects of Co-60 gamma-irradiation treatments (2.5, 5.0, 10.0 and 20.0 kGy) on the gluten proteins of two bread wheats and one durum wheat cultivar were investigated. Dough theological properties of the flour processed from the irradiated wheat were also determined using a computerised micromixograph. Irradiation caused a significant deteriorating effect on all mixogram parameters. There was no observable effect of irradiation on gliadin proteins analysed by polyacrylamide gel electrophoresis. The 50% 1-propanol-insoluble (50 PI) glutenin fraction was highly affected by irradiation. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, reduced 50 PI glutenin showed a noticeable reduction in band intensities of both high (HMW) and low molecular weight (LMW) glutenin subunits (GS) with increasing irradiation dosage greater than 5 kGy. The irradiation effect on 50 PI glutenin was further studied and quantified by reversed-phase high-performance liquid chromatography of glutenin subunits; there was a progressive decrease in the quantity of subunits with increasing irradiation dose level. Compared to non-irradiated wheat, the relative decline in total insoluble glutenin at the 20 kGy dosage level ranged from 34-49% depending on cultivar. Increasing levels of irradiation also progressively reduced the ratio of HMW:LMW-GS up to 13-15% at 20 kGy indicating that irradiation had a greater effect: on the largest polymers of glutenin. The observed weakening of dough mixing properties and concomitant decline in the quantity of 50 PI glutenin with increasing levels of gamma-irradiation are consistent with a degradation of glutenin to a lower average molecular size by depolymerisation and/or disaggregation. (C) 1998 Academic Press.