Five glutenin subfractions (R-2-R-6) were extracted by sequential centrifug
ation and addition of sodium chloride, from defatted flours of three wheat
cultivars viz. Aubaine (extra-strong), Hereward (strong) and Riband (weak).
Seven minutes mixing time was used to carry out fractionation on the basis
of depolymerization of glutenin macropolymers (GMP) by using a 2-g Mixogra
ph traces. Depolymerization of GMP occurred at much higher rates in dough o
f weak cultivars compared with strong and extra-strong cultivars. Protein c
ontent was also estimated in GMP (SDS-unextractable) and supernatant (SDS-e
xtractable). Extra-strong cv. Aubaine contained maximum amount of all the g
lutenin fractions (R-2-R-6) followed by strong cv. Hereward and weak cv. Ri
band. Polypeptide compositions of different glutenin fractions were determi
ned by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE
) under reduced and unreduced conditions, followed by densitometric scannin
g of stained patterns. The pattern areas of reduced fractions were divided
into subareas representative of three main protein classes: high molecular
weight (HMW) glutenin subunits; omega -gliadins and a mixture of low molecu
lar (LMW) glutenin subunits and alpha, beta and gamma -gliadins. The amount
s of various subunits were proportionate according to the molecular weight
of the fractions in each cultivar. The ratio of HMW-glutenin subunits to th
e LMW-glutenin subunits in each cultivar were found to decrease with the fr
actionation from R-2 to R-6. Bread-making quality of three cultivars was al
so assessed by adding various fractions to a base flour and measuring mixog
raph peak development time and loaf volume in an optimized baking test. The
quality of bread prepared from flour of weak cv. Riband was improved signi
ficantly by the addition of HMW fraction (R-2) when measured in terms of lo
af volume. However, the addition of LMW fraction (R-5 + R-6) did not cause
any appreciable improvement in bread quality over control. On the other han
d, addition of HMW fraction (R-2) in the flour of good bread wheat cv. Here
ward caused adverse effects on the bread-making quality by disturbing the v
iscoelastic properties. Supplementation of R-2 fractions in extra strong wh
eat cv. Aubaine caused marginal reduction in loaf volume over control. Ther
efore, the precise proportion present of the two classes of subunit is esse
ntial to achieving a proper balance between elastic and viscous properties.