[lic] Kemian tekniikan korkeakoulu / CHEM

Permanent URI for this collectionhttps://aaltodoc.aalto.fi/handle/123456789/26

Browse

Browsing [lic] Kemian tekniikan korkeakoulu / CHEM by Department "Department of Bioproducts and Biosystems"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Colloidal structures of phospholipids in vegetable oil and their potential usage in surface treatment of nanocellulose for food applications
    (2019) Lehtinen, Olli-Pekka
     School of Chemical Engineering | Licentiate thesis
    The aim of the licentiate’s thesis was to understand the colloidal behaviour of phospholipids in vegetable oils and to study the adsorption of phospholipid nanostructures onto the surface of cellulose nanofibrils. Water concentration, temperature and free fatty acid had an effect on the formation of reverse micelles of phospholipids in vegetable oil. At low water concentration, phospholipids formed solubilized reverse cylindrical micelles above critical micelle concentration (cmc) in the oil. Increasing temperature decreased the cmc of phospholipids in oil. Addition of moderate amount of water into oil caused solubilized phospholipids to form lamellar liquid crystal structures that were precipitated from the oil and formed separate phase. Oleic acid in rapeseed oil increased the solubility of lecithin and suppressed the formation of phospholipid reverse micelles at low water content. In presence of more water, the oleic acid stabilized the reverse micelles and consequently more water was needed to induce the phase separation. Thus it could be concluded that moderate amounts of oleic acid (5 wt.-%, 10 wt.-% and 20 wt.-%) in the oil delayed the removal of phospholipid reverse micelles upon addition of water, and the formation of lamellar structures required more water. This was caused by the increased solubility of lecithin into oil due to the co-solvent effect of oleic acid. Nanocellulose has shown many potential applications in foods, such as emulsifiers, fillers, structuring agents and cholesterol binders. An interesting application for nanocellulose would be the replacement of saturated fats in foods to decrease the fat content and the energy content of the products. To increase the compatibility of nanocellulose with the vegetable oil, the adsorption of phospholipid nanostructures was studied by immersing cellulose nanofibril film into the oily liquid containing phospholipid lamellar structures. The contact angle measurement seemed not to be an optimal way to measure the adsorption of phospholipids onto the surface of nanocellulose due to the variation in the results. Some of the contact angle measurement results indicated that the addition of the oily liquid containing phospholipid lamellar structures onto the surface of nanocellulose decreased the hydrophilicity of the surface after rinsing it with chloroform. In addition, two measurements indicated that the addition of oily liquid containing phospholipid lamellar structures decreased the hydrophilicity of the surface.
  • Viscose filterability and fiber wall pore size as a measure of pulp reactivity
    (2019) Lehtonen, Eeva
     School of Chemical Engineering | Licentiate thesis
    This study presents research on pulp properties and characteristics affecting the reactivity and accessibility of the pulps. Pulps with different production methods and wood species were selected for the tests. Mainly dissolving pulps were investigated, but in addition, one paper grade pulp was also included in the selection as a reference of hemicellulose-rich pulp. In order to comprehensively understand the cellulose structure, pulp samples were investigated at three different levels: molecular, supramolecular and morphological. The main method used in this study was the viscose filterability test (Treiber test), which determines the filterability value (FV) of viscose and describes pulp reactivity, which is understood as the processability and quality of the pulp. The Treiber test device was built and thoroughly evaluated for FV determination. Pulp accessibility (reactivity) was investigated by determining the pore size of the fibre wall. The methods included solid-state NMR (to determine the lateral fibril aggregate dimensions (LFAD)), the fibre saturation point (FSP) and BET measurements. The results showed that the production method of the dissolving pulp, as well as pulp’s chemical composition, macromolecular properties and other characteristics affect the pulp reactivity (FV). High hemicellulose content indicated poor reactivity (FV) and a lower CS2 -charge negatively affected reactivity. A relationship between the crystallinities measured by NMR and the viscose filterability was found. This result was not expected, due to the results of earlier studies. A correlation between the crystal width and the filterability value was also found. Viscose filterability increased parallel with increasing crystal width.