Browsing by Author "Peltola, Kimmo"

Literature review of this thesis deals with properties and applications of hemicelluloses and stabilizers used in milk products. In addition, the literature review discusses interactions between proteins and polysaccharides and how they affect properties of food products. In the experimental section, interactions between birch glucuronoxylan and milk protein were compared to interactions between gum Arabic and milk protein. Experimental research included interaction tests between polysaccharides and milk protein and preparation of yoghurt. The aim of interaction tests was to find sample compositions where interactions were present. Protein-polysaccharide interactions were investigated with methods based on light scattering, fluorescence spectroscopy, zeta-potential, and electric conductivity. Viscosities, whey separation and sensory properties of yogurt samples were also studied. This study showed that birch glucuronoxylan and gum Arabic have different effect on samples containing milk proteins. When concentrations of glucuronoxylan and gum Arabic were equal, structure of sample with glucuronoxylan was more stable than structure of sample with gum Arabic. Fluorescence spectroscopy showed that glucuronoxylan affected the emission intensity more than gum Arabic. This may be due to stronger interactions between glucuronoxylan and milk proteins compared to gum Arabic. Electric conductivity measurements also showed similar results. Viscosities of reference yoghurt sample and yoghurt sample with glucuronoxylan did not differ. Viscosity of yoghurt sample with gum Arabic was lower than viscosities of other two samples. Whey separation took place in all samples. In sensory evaluation of yoghurt samples, the thicknesses of reference sample and sample with glucuronoxylan were evaluated similar. Sample with gum Arabic was evaluated the thinnest. There were not observable differences in taste of yoghurt samples.