Browsing by Subject "kaurahiutale"

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  • Jaakkola, Jenni (Helsingfors universitet, 2015)
    The aim of this master’s thesis was to study the effects of flaking conditions on the quality properties of oat flakes and to simulate the flaking process in laboratory conditions. The review of literature deals with oat processing focusing on oat flaking and oat flake quality properties. The flaking process includes groats steaming and tempering, which plasticizes the groats when moisture is absorbed. Then the groats are flattened by a flaking roller mill. Increasing tempering temperature and time results in higher water absorption. Increasing tempering time also increases the amount of fines. Flake breakage in the process reduces the flake yield resulting in more costs. There are no published studies that evaluate the impact of steaming on flake quality properties. The aim of the experimental part of this thesis was to study the effects of flaking moisture on flake strength and quality. Kilned and unkilned groats were flaked in a laboratory-scale flaking machine. Laboratory-scale flaking was carried out with a standardized flake thickness 0,7-0,8 mm. In addition, the properties of five commercial oat flakes were analyzed. There was significant variation between the different commercial oat flakes in their both water hydration capacities and amount of fines. The results implied that flaking conditions have an effect to these flake quality properties. Oat flakes were significantly thicker with higher flaking moisture. The roll gap was tightened to produce the same flake thickness. Both the bulk density and the amount of fines decreased with higher flaking moistures. There were no significant changes in the pasting properties of flakes made of kilned groats compared to kilned groats. Increasing flaking moisture reduces the amount of fines. In addition, water absorption increased with high flaking moistures. Even a three-percent increase in flaking moisture improved the quality of oat flakes. Increasing flaking moisture in between 12-20 % had a beneficial effect on quality properties of oat flakes.
  • 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.