Browsing by Author "Tikkanen, Marika"

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.