Browsing by Subject "kaurajauho"

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  • Tikkanen, Marika (Helsingfors universitet, 2016)
    The literature review studied the composition of oat grain, processing methods, and factors linked to baking quality of oat flours and flakes. The aim of the experimental part of the study was to examine the processing stages that modify water-binding capacity (WBC) and baking properties of oat flours. The effects of heat treatment temperature and duration as well as milling of whole grain oat flour on WBC were investigated. WBC was determined using a centrifugal method following a Box - Behnken design, where every variable had three levels: duration of the heat treatment (50, 60, 70 min), temperature of the heat treatment (95, 100, 105°C) and coarseness of the flour (fine, medium, coarse). In baking tests, the baking quality of two whole grain oat flours with different particle size distribution was compared in oat-wheat baking (50 % oat). Bread volume, firming and sensory quality were evaluated. Furthermore, the WBC of oat flakes produced by several manufacturers was compared. Coarseness of the oat flours had the strongest effect on WBC, which increased as the proportion of fine particles increased. Quick (small flake) oats bound more water than large flake oats. The duration and temperature of the heat treatments did not have significant effects on WBC, although it was at its highest when duration and temperature were at their maximum (70 min/105 °C). The specific volume of the breads containing coarse oat flours was highest. Firming of these breads was also slower, but there was no significant difference. Fine oat flours contained a large number of bran particles that are known to disturb gas bubbles in dough, allowing gas to escape. The consistency of the dough made with coarse oat flour stayed low due to its low WBC. In that case, there was a sufficient amount of water for wheat gluten to form a continuous gluten network, resulting in the highest specific volume in the bread. Results showed that milling had a great effect on WBC of whole grain oat flours. For bread-baking purposes, the optimum oat flour was coarsely milled.
  • Rauta, Janne (Helsingin yliopisto, 2019)
    Extrusion is a versatile thermomechanical food processing technology, and cereal based snack products made with extrusion are one of the most significant ready-to-eat products. The literature review covered extrusion process in general while the effect of different components of grain and milk powders in extrusion was examined more closely, and also different methods to evaluate the properties and the quality of extrusion products were examined. The objective of the experimental study was to study the effects of sugar content and composition as well as the effects of different milk protein and water contents of the mass on the properties (water content, expansion and hardness) and organoleptic quality of extrudates. Experiments were carried out by using twin-screw extruder and the main component of extrudates was a mixture of oat flour and waxy maize starch. Three different milk powders were used (one lactose-containing and two lactose-free skimmed milk powders) in experiments, so that the milk protein content of mass was 8, 10 and 12 % (from solids) and water content 14, 16 and 18 %. The effect of sugar composition (lactose vs. glucose/galactose mixture) and sugar content (lowering the milk sugar content to about 60 % from solids) in extrusion was also examined. The water content, hardness and expansion of extrudates were measured. In sensory analysis (n=6) the effect of different milk powders and water contents on extrudates were evaluated. More expanded and less hard extrudates were obtained by adding milk powder that contained lactose compared to lactose-free milk powders. Lowering the sugar content did not affect the properties of extrudates significantly. Increasing the milk protein content of the mass increased the typical positive features of extrudates when lactose-containing milk powder was used, but when lactose-free milk powders were used the effect was the opposite. Increasing the water content of the mass decreased the expansion and increased the hardness of extrudates. In sensory analysis the major differences were observed in the darkness of color and the diameter of the extrudates. According to the results of the present study it is possible to obtain extrudates with good structure using lactose-containing milk powder as well as lactose-free milk powder. However, lactose-containing milk powder may be a better alternative in extrusion compared to the lactose-free milk powder. It may be possible, to some extent, to lower the sugar content of the extrudates that contain lactose-free milk powders without compromising the structural and organoleptical quality of the extrudates.