Browsing by Subject "Galactoglucomannan"

The current trend in the food and forest industries is to utilize sustainable and renewable products. One such product is galactoglucomannans (GGM), water-soluble hemicelluloses covering 25–35 % of the dry wood mass. GGM can be extracted from spruce sawdust or branches using a safe and environmentally friendly pressurized hot water extraction (PHWE) method. Deacetylation of GGM happening during extraction and concentration by membrane filtration at alkali conditions possibly enables gel formation. This thesis aims to observe if low acetyl GGM has the ability to form a gel and which factors have an impact on its gelation and gel properties. Low acetyl PHWE GGM powders were provided by the Natural Resources Institute of Finland (Luke). The GGM solutions at different pH values (4, 7, and 10) and solid concentration levels (5, 10, and 15 %) were prepared using a magnetic stirring rod and then ultrasonicated (50% amplitudes for 5 min). Viscosity, rheological properties, water holding capacity (WHC), hardness, and adhesiveness were measured on days 1, 2, 3, and 5 during storage at room temperature (22 °C). The results showed that GGM was able to form a gel at all investigated conditions, except for the samples at pH 4 and a solid concentration of 5 %. GGM solutions at high pH (7–10) and solid concentrations (10–15%) formed gels without ultrasonication. All GGM gels had high WHC (≥ 90 %). Gel viscosity increased with prolonging of storage time and increased solid concentration. The frequency sweep analyses showed that all investigated samples had a gel-like behavior. Gel hardness and adhesiveness increased in all the samples during storage and increased solid concentration. The thesis demonstrated that low acetyl GGM could form a gel, which could be used as a gelling agent, where solid concentration and pH impacted to gel structure. Thus, the study could widen industrial applications of GGM or at least engage interest.