Study On The Interaction Between Spent Brewer's Yeast β-glucans And Other Macromolecules

Food are usually complex mixtures of many components including biopolymeric thickeners and gelling agents, in which polysaccharides and proteins play important roles due to their functional and textural properties. The synergistic effect between certain macromolecular compounds (like galactomannan, agarose, gelatin and so on) are known to improve mechanical properties, functional properties and appearance of food products. The mechanism of interaction between them has been the subject of much interest since early studies (Dea & Morrison, 1975) and is a matter of debate and quite a few valuable findings and several models have been proposed following one by one.The objectives of this thesis were studied on the interactions between brewer's yeastβ-glucans (BYG) andκ-carrageenan (KC), Xanthan Gum (XG), or gelatin (GEL), respectively, by rheological, differential scanning calorimetry (DSC) and scanning electron microscope (SEM) experiments.The results were as follows:1 Small amplitude oscillatory tests in the linear domain of viscoelasticity showed that brewer's yeastβ-glucans suspension (solid content less than 6.0%) showed typical dilute polymer solution characteristic in all experiment conditions. SEM images gave perspicuous micro-properties of brewer's yeastβ-glucan particulates, which was well-regulated and homogenous.2 Small amplitude oscillatory tests in the linear domain of viscoelasticity showed thatκ-carrageenan played the major role in the viscoelasticity of the mixtures, and brewer's yeastβ-glucans strengthened the gel-net configuration,instead of inhibiting the formation of the ordered structure ofκ-carrageenan, especially in mixtures with lowκ-carrageenan concentration(0.05 and 0.1wt%), that is, when the content of brewer's yeastβ-glucans was up to 4.0%, the G'and G''value of mixture were 50-60 times higher than that ofκ-carrageenan alone. Cooling and heating DSC curves with broad exothermic and endothermic peaks, which were inconsistent with the phenomena ofκ-carrageenan alone, was indicated that there were some interactions between the two polymers. SEM images showed thatκ-carrageenan upbuild the continuous network construction and brewer's yeastβ-glucan particulates seem to adhere to the network, both the two polymers contribute to the network.3 Brewer's yeastβ-glucans and xanthan gum showed compatibility in mixture system. Because both of the two polymers have no gelation quality, the mixtures did not show gel behavior, either. Xanthan gum played the leading role in the rheological properties of the mixtures, and brewer's yeastβ-glucans raised the value of G'and...