Structure-function relationships of cereal B-glucans

There is good evidence that rheological properties play a key role in deter-mining the health benefits of cereal ?-glucans. The primary focus of studies has been flow viscosity. Because of the power law relationship between concentration or molecular weight, and viscosity, small differences in solubility or molecular weight can profoundly influence viscosity development in solution (halving concentration may produce a 15 fold decrease in zero shear viscosity). Depolymerisation similarly may have a profound effect on flow viscosity, but as well as reducing the measured flow viscosity, the elasticity, or gel character of the solution may increase. In model clinical studies of glycemic response, using different preparations of ?-glucan, about 90% of the differences between different treatments could be accounted for by the flow viscosity of the drinks consumed by the subjects, but the influence of gel formation on glycemic response is unclear. Oats and barley are the primary source of ?-glucan but it is also found in rye, wheat and the lichen Icelandic Moss. Structural analysis show that the ?-glucan from all sources is com-posed primarily of ?-(1?3)-linked cellotriosyl and cellotetraosyl units, but there are also regions that are more cellulose-like in character, with 4 or more consecutive ?-(1?4)-linked glucose units. There are some differences between the structures of these different ?-glucans, and these, as well as molecular weight, modify the ability to form gels. Studies of the different gelation characteristics of the ?-glucans have allowed conclusions as to the mechanism of gelation. Böhm N. & Kulicke, W.-M. 1999a. Carbohydrate Research 315: 293-301; Böhm, N. & Kulicke, W.-M. 1999b. Carbohydrate Research 315: 302-311; Tosh, S.M., Wood, P.J., Wang, Q. & Weisz, J. 2003. Carbohydrate Polymers 55: 425 436.vokMyynti MTT tietopalvelu