Browsing by Subject "kiteytyminen"

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  • Pölkki, Annika (Helsingin yliopisto, 2015)
    The scope of the literature review was to define the physical properties and crystallization of amorphous sugars as single substances and mixtures. The purpose of the experimental part was to measure the water sorption, glass transition and crystallization of sucrose, isomaltulose and different mixtures of both. Crystallization and water sorption was measured with Dynamic Vapour Sorptions (DVS) -system, and with a differential scanningcalorimeter (DSC). Water sorption was studied by weighing samples that were stored at different relative humidities (11 - 85 %). Crystal forms were studied with the x-ray diffraction method. The sucrose samples reached a stable-state at relative humidities of 11-33% in one day of storage. The same was true for isomaltulose samples. Mixtures adsorbed more water the higher the relative humidity. Mixture samples reached a stable state in a day of storage at relative humidities of 11 - 44 %. Water sorption was modelled with the BET-model. The glass transition temperature, measured with DSC, of anhydrous sucrose was measured at 57 ºC. The glass transition temperature of anhydrous isomaltulose was slightly lower 47 ºC. The glass tranition temperature of a mixture sample, at 0 % relative humidity, was in between those two, 50 ºC. The glass transition temperature of sucrose was higher than that of isomaltulose after storage at relative humidities of 11 - 33 %. The critical water content of sucrose and mixture was 3, for isomaltulose it was 2 (g water/100 g solid). The critical storage humidity for sucrose was 25 %, for isomaltulose and mixtures it was 20 %. In testing with DSC sucrose was the only sample to crystallize. The higher the storage relative humidity before testing, the lower the crystallization temperature was for all sucrose samples. Crystallization temperature test run with the DVS system showed that sucrose crystallized at lower relative humidity than a mixture. Pure sucrose and mixtures did not share any reflection angles in x-ray diffraction tests, but isomaltulose and mixtures shared many reflection angles. This led to the conclusion that the mixtures contain more isomaltulose crystals than sucrose crystals. Adding isomaltulose to sucrose did not have a large effect on glass transition temperatures. Glass transition temperatures for mixtures were inbetween sucrose and isomaltulose. Isomaltulose however retarded crystallization greatly. The mixture required a significantly higher relative humidity in order to crystallize than either sucrose or isomaltulose.
  • Markkanen, Minna (Helsingin yliopisto, 2021)
    The orbicular quartz monzonite from Kuohenmaa, Southwest Finland, is one of the most beautiful and well-known orbicular rocks in the world. The cores of the orbicules are peraluminous in composition, most likely of xenolithic metasedimentary origin. The cores are surrounded by orbicule mantles, which consist of several alternating biotite- and plagioclase-rich shells. There are three types of orbicules in Kuohenmaa orbicular rock: proto-, small-, and large-orbicular types. Proto-orbicules have only a few shells, small orbicules ~ 50 shells in average, and large orbicules over 250 distinct shells. In addition to shells, one sample was observed to be associated with comb layering in the contact of proto-orbicular and large orbicular types. Structures and textures of the comb layer resembles those of the outer shells of large orbicules. The orbicules are embedded in interstitial coarse-grained groundmass that forms locally almost pegmatitic patches. The petrographic observations were acquired from eight samples or sample photographs gathered from different collections. A mineral chemistry dataset was measured from a single large orbicule from the University of Helsinki collections. The main minerals of the Kuohenmaa orbicular rock are plagioclase, biotite, microcline, muscovite, and chlorite. The shell textures vary from branching plagioclase-rich shells to fine-grained plagioclase- or biotite-rich shells. Branching shells are mainly oligoclase, but a few granular andesine crystals were detected in the core. Peculiar interstitial fibrous allanite masses were found in the inner branching plagioclase-rich shells. The plagioclase compositions generally follow a regular fractional crystallization trend from core to groundmass, but some changes towards more primary compositions are observed in the orbicule mantle. Plagioclase crystals display only minor compositional zoning, suggesting rather quick crystallization. Biotite is very aluminous (Al2O3 17.63–18.53) in composition, and the compositional changes seem to have somewhat positive correlation with plagioclase compositions, suggesting changes in their crystallization conditions. Injections of primary melt from a deeper source most likely caused the observed changes to more primitive composition in plagioclase and biotite composition. Through the detailed petrographic and geochemical studies, a model of undercooling caused by decompression driven fluid saturation is proposed as a mechanism for orbicule formation in the Kuohenmaa orbicular rock. Branching plagioclase with interstitial fibrous allanite masses and several fluid inclusions in plagioclase indicates separate aqueous REE-enriched melt and rapid crystallization. Further studies of fluid inclusions and REE-enriched phases could provide information of the fluid origin and crystallization conditions.
  • Kolu, Anna-Maija (Helsingfors universitet, 2013)
    Spray drying is one way to dry protein medicines and it has many advantages compared to other drying methods, for example it is a fast process. In spray drying high temperature and mechanical stress can inactivate the protein. Disaccharides are generally used as protective agents of protein in spray drying because they have an ability to protect the structure of the protein during drying and storage. Aim of this research was to study the stability of the protein during spray drying and storage by using β-galactosidace as a model protein. Aim was also to characterize the physical properties of trehalose and melibiose and to study how well they protect the protein. Some of the central matters to be examined were the glass transition temperature, crystallinity, water activity, yield of the spray dried powder and protein activity. Especially studying the properties of melibiose in spray drying was important because it has not been used before. The study also included the optimization of the process parameters to be suitable for the product. Trehalose and melibiose transformed to an amorphous form during spray drying. Both XRPD and DSC showed an amorfous form. Trehalose and melibiose proved to be good protective agents for the protein during spray drying and storatge probably because they remained their amorphous structure. β-galactosidase remained activity very well. Optimizing of the process parameters was successful because protein remained its activity and still the powder was quite dry and yield was good. The changes in the structure of the protein were studied with FT-IR but the amount of the protein was too small. Problems caused by the spray drier may have an effect to the results, but on the other hand the spray dryer was made to work optimally.
  • Narinen, Lauri (Helsingin yliopisto, 2019)
    Controlling crystallization is an important factor in the production of food, whether it is preventing crystallization or enabling it, depending on the food product. To control crystallization, one must understand the theory behind crystallization and the components in food that affect crystallization. In sugar icing the most obvious components are sugars and water that affect crystallization. Also, the frozen storage has an important role concerning shelf-life of the sugar icing. The aim of this study was to prolong the shelf-life of the sugar icing on top of the donuts and to understand the phenomena that have an influence on the quality of the sugar icing during freezer storage. The experimental part of the study was divided into two parts. Preliminary tests were conducted in the first part. In these preliminary tests the aim was to measure the temperature and relative humidity during the melting of donuts in its packaging and to evaluate the applicability of ultracentrifuge and Karl Fischer titration in the measurement of the sugar icings properties. In the main experiment part, the water activity was measured from the different parts of the donut, the freezing of the sugar icing as well as its viscosity were evaluated and the shelf-life of the sugar icing on top of the donuts was evaluated. Karl Fischer titration was found to be a suitable method for measurement of water content of sugar icings. Also, the ultracentrifuge was found to be a suitable method to measure the liquid phase of the sugar icing. In the measurement of the conditions during the melting of the donuts it was detected that the conditions in the package that was open during the melting of the products, balanced with the conditions surrounding the packaging rather quickly. At the same in the closed package the conditions remained same during melting even though the melting was done in different surrounding conditions. The shelf-life of the donuts was found to be shortest in those icings that had less water or if the water was less free in the icing. The longest shelf-life was found to be in the coated sugar icings. Methods to prolong the shelf-life of the sugar icing on top of the donut were found in this study. Also, the phenomena affecting the quality of the sugar icing during frozen storage were discovered to some extent but to understand them even further requires more research.