Browsing by Subject "Hemiselluloosa"

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  • Teräslahti, Suvi (Helsingin yliopisto, 2015)
    The oxidation of polyunsaturated fatty acids is one of the most important chemical reactions degrading the nutritional quality, taste and safety of food products. The characteristics of emulsions, the mechanisms of unravelling of the emulsion structure along with the behavior of commercial emulsion stabilization agents were presented in the literary review part. Also the potential of polysaccharides as emulsion stabilizers was evaluated and a summary of characteristics of lipid oxidation in emulsions was presented. The aim of this study was to evaluate the chemical stability of oil-in-water emulsions stabilized with four polysaccharides by monitoring the oxidation of their lipid phases. In the experimental part, the ability of spruce galactoglucomannan (GGM) to stabilize the lipids in an emulsion was compared with the stabilizing capacity of carboxymethylated galactoglucomannan (CM-GGM) and two commercially available polysaccharides, corn fiber gun (CFG) and gum arabic (GA). Normal and antioxidant-free rapeseed oils were used in the emulsions and the emulsions were protected from light and stored at 4 and 40 °C. The lipid particle sizes of the emulsions were measured with optical microscope and peroxide values were determined from the lipid phases of emulsions. The formation of volatile oxidation products in the emulsions was determined with SPME-GC-MS and the amounts of lipid-derived polymers were determined with size exclusion chromatography (SEC-RI). The structure of the polysaccharides and a part of their phenolic compounds slowed down the oxidation of emulsions. Less hydroperoxides, volatile oxidation products and polymers was formed in the emulsion stabilized with GGM. The lipid phases of emulsions stabilized with native and carboxymethylated GGM oxidized equally slowly. The emulsion stabilized with GA oxidized faster than other emulsions. The lipid particles in emulsion stabilized with both native and carboxymethylated GGM were observed to form flocs. Also the natural antioxidants of the rapeseed oil and a lower storage temperature improved the chemical stability of the emulsions. The physical location of spruce GGM in the emulsion structure and detailed identification (MS) of GGM’s phenolic compounds would be interesting research topics in the future.