Browsing by Subject "vanheneminen"
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(2020)Oat starch differs from other cereal starches in morphology and composition. According to the food industry, the usage of oat in baking is restricted by the rapid staling of oat products, meaning they deteriorate in quality, seen as increased hardness and crumbliness. In baking, starch is only partly gelatinized due to restricted amounts of available water. The gelatinization and aging properties of oat starch in limited water are not yet comprehensively known. The aim of this study was to investigate how the stage of gelatinization and total water content affected the aging of gels prepared from oat flours produced by different treatments. In this study, Mixolab was used to prepare gels from oat flour and water with three different water contents (50, 60 and 70 % water) and in three different stages of gelatinization (under, optimally and over gelatinized). The aging of gels was indicated by the change in their hardness which was measured by a Texture Analyzer 1, 2 and 7 days after preparation. Other analyses from the flour samples included water retention capacity by centrifugation method, particle size distribution by laser diffraction and gelatinization behavior in excess water measured by a viscometer (RVA). Results showed that the further the gelatinization proceeded, the more the samples hardened during storage. The hardness of under gelatinized samples did not increase at all. In optimally gelatinized samples the hardness increased in the samples which had the least water. All the over gelatinized samples hardened during storage. The further the gelatinization process had proceeded, the more there probably was solubilized starch in the sample, causing the gel hardness to increase more. The bigger the water content, the softer was the sample. In the samples with the highest water contents, the hardness did not increase rapidly, probably because the solubilized starch molecules were too far apart to create crystal structures. Only minor increase in hardness was observed in gels made from non-heat treated oat flour. This could be explained by the possible enzyme activity in the flour retarding the aging, since the natural enzymes in oat were not inactivated by heat treatment. The differences between flours were explained by their different particle sizes and starch and beta glucan contents. Beta glucan increased the water retention capacity of flour in room temperature. The highest consistencies during gelatinization and hardest gels during storage were produced by the flour which had the highest starch content. It also had the smallest particle size, thus causing it to have the highest water retention capacity.
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(2020)One of the most common packaging materials for food is polymers. The properties offered by plastic packaging are good for food, but there is a general demand to reduce the usage of plastic. The demand for reduction is due to the fact that plastic is often made from fossil raw materials. In the case of foodstuffs, it is not possible to completely remove the plastic packaging material as this would result in faster food spoilage and thus greater food waste. The amount of plastic can be reduced by using it as part of the multilayer material. In multilayer materials, the most common raw material is cardboard, which is generated from renewable raw materials. In addition to plastic packaging made of virgin material, plastic materials made from recycled polymers may also be used in food packaging in future, provided that their safety conditions are met. The aim of the study was to investigate the effect of freezing temperatures and ultraviolet radiation (UV) on the properties and aging of recycled plastic. The research methods were divided into physical, barrier and chemical measurements. Samples were imaged using a scanning electron microscope. The hypothesis in the study was that freezing conditions and UV treatment both age the packaging material. UV radiation is expected to age samples more than freezing conditions. The study will focus on PET (polyethylene terephthalate) and LDPE (low density polyethylene) coated cardboards. The study partially answers to the hypothesis. Frost conditions were had weaker aging effect than UV radiation, as expected. On the other hand, recycled plastics cannot be said to be easier to age than virgin materials. Particularly between the different measurements, the materials did not differ clearly in their aging.
Now showing items 1-2 of 2