Browsing by Subject "taikinan rakenne"

The literature review examined barley (Hordeum vulgare) hordein, starch granule-associated proteins and gelprotein, dough formation during mixing and starch-protein interaction in the dough. The aim of this study was to define the structure of barley dough and specify barley hordeins that form the dough structure. The purpose of the preliminary studies was to find out can ascorbic acid change barley dough structure. Mixograph was used to mix barley dough and to study dough formation. Barley dough rheology was studied using dynamic oscillation measurements. 1.5 % SDS-solution and centrifugation was used to isolate proteins from barley dough. The protein composition of the separated dough phases was analysed by SDS-PAGE. SDS sedimentation value was also determined. Ascorbic acid (120 ppm flour weight) did not change the rheological properties of the barley dough. Centrifugation separated four solid phases from barley dough; gelprotein, white layer, bran and starch. Results from the Bradford protein assay and the iodine test showed that white layer under gelprotein in the centrifuge tube contained protein and starch while gelprotein contained only proteins. SDS-PAGE showed that reduced gelprotein from barley dough consisted of D- and B-hordein but only minor amount of C-hordein. C-hordein was found, however in the dough liquid phase. The protein composition of the gelprotein was identical with the white layer. In the non-reduced gelprotein and the white layer hordeins were in polymeric form because they did not penetrate in the SDS-PAGE gel. Two studied barley doughs with the same protein content (12.0 %) differed they protein composition. In SDS-PAGE one band more B-hordeins (35 kDa) was showed in the dough which area (cm2) of the mixogramm, sedimentation value and storage modulus (G´) and loss modulus (G´´) were higher. The storage modulus (G´) of the barley dough increased during 160 min dough rest. G´ and G´´ values of the barley dough were frequency (Hz) dependent and they increased when frequency increased. Sedimentation value positively correlated with modulus (G´, G´´) and area (cm2) of the mixogramm. Based on dough rheology this study showed that barley dough structure was a weak gel. Barley hordein, especially certain B-hordeins seems to be significant in the formation of dough structure. In addition results indicated the interaction between starch and hordein in the barley dough. This study clearly showed that barley dough contained high molecular weight hordein polymers stabilized by interchain and intrachain disulfide bonds. Hordein polymer size remained unknown but the rheological properties of barley dough support the conclusion that high molecular weight gelprotein structure formed in the barley dough.