Browsing by Author "Junttila, Emmi"

Many food products such as butter, salad dressings and ice-cream consist of water-in-oil (W/O) or oil-in-water (O/W) emulsions. Emulsions are thermodynamically unstable and this is the reason why food industry uses different kinds of emulsifiers and stabilizers which extend the shelf-life of the products and also improves their quality. The consumers’ interest towards plan-based and sustainable ingredients has increased, but at the moment the number of Finnish plant-based stabilizers is limited. Forest industry is also under pressure to find new use for its by-products.. Some studies on the glucuronoxylan and galactoglucomannan extracted from spruce and birch saw meal have been made and the results have been promising. Xylan has been extracted by different methods and from birch sawdust the yield has been approximately 50 wt%. The use of birch GX in food products has not yet been authorized, but the food industry is already using some of the byproducts of woodworking industry such as xylitol. The aim of this study was to find the suitable mixture ratio of oil, water and birch glucuronoxylan in emulsions as well as the factors affecting the physical state of the emulsions. The results of this study can be used to support the findings of other studies so that domestic plant based emulsion stabilizers can be used in the food-industry in the future. In this study seven different emulsions were produced by varying the ratio of oil and glucuronoxylan. By studying the physical properties of the freshly prepared emulsions together with the varying storage conditions (+4 °C, +21 °C and +40 °C) the study aimed to find the optimal mixture ratio. The droplet size of dispersed phase was studied by using static light scattering and the possible flocculation was viewed by optical microscopy. The height of the creamed phase and the turbidity/ other changes in appearance were visually investigated by photographing the samples. A sample of emulsion was taken apart and centrifuged to find out the amount of xylan on the oil droplet interface and in the continuous phase. In addition, the monosaccharide composition of xylan on oil droplet interface and continuous phase were determined by gas chromatography mass spectrometry (GC-MS). All the seven emulsions investigated were polydispersions according to the droplet size distribution. There were two peaks on almost every droplet size distributions since the first measuring. The droplet size distributions were stable for the whole 67 days investigation period when the emulsions were stored in +4 °C temperature excluding two emulsions. In +21 °C and +40 °C temperatures the droplet size of all the investigated emulsion grew. The greatest part of the carbohydrates was in the continuous phase of emulsions. The size difference between the polysaccharides from the surface of the oil droplets and the continuous phase was not big. About 80 % of the monosaccharides in the emulsions was xylose. According to the findings of this study, there was more methyl glucuronic acid, which is a component of xylan, in the water than in the interfacial oil phase of the emulsions (0.65 – 5.7 μg/g).