2024

Sammalisto, Saara

Oats have gained popularity in breadmaking, especially in Northern countries. However, non-wheat oat baking has been studied relatively little and quality factors have not been set for breadmaking oats. Limited knowledge makes oat baking challenging to predict and control. Oats differ from typical breadmaking cereals as a hydrothermal steaming and tempering treatment is included in their milling process. Currently, no standard exists for the treatment, and the relations between treatment parameters and milling properties of oats remain unstudied. The aim of this study was to investigate whether oat flour particle size could be altered by the hydrothermal treatment parameters. A further aim was to identify factors related to the baking properties of oats by investigating the baking properties of 20 whole grain oat cultivar samples and evaluating the functionality of various hydrocolloids in oat baking. Both native oat groat properties and steaming and tempering treatment parameters were shown to affect particle size of oat flours, as softer native groats and increasing treatment temperature resulted in finer oat flours. In softer native groats, also moisture content during the treatment affected particle size. In baking study of 20 whole grain oat cultivar samples, significant variation was observed in optimal dough consistency, bread specific volume, and bread crumb properties. Dough yield optimisation was an important factor affecting volume and texture of the oat bread. In addition to high optimal dough yield, high fat content of the flour was related to the increased specific volume of the bread, and small particle size was related to the softer bread crumb and reduced staling rate. Regarding hydrocolloids studied in oat baking, with oat ß-glucan extract (water-soluble fraction of oat bran concentrate, OBC) as a hydrocolloid, softer bread crumb and reduced rate of staling were obtained compared with use of psyllium and HPMC as hydrocolloids at optimised level. For the improvement in crumb properties, removal of the insoluble fraction from OBC was necessary. The present study showed that oat flour particle size can be optimised for specific uses by choosing soft native groats and adjusting hydrothermal treatment parameters. In whole gain oat baking with optimised dough yield, increasing fat content of the flours improved gas cell stabilisation, and with smaller particle size of the flours, dough water was presumably more evenly distributed. With oat ß-glucan extract as a hydrocolloid, oat bread of softer crumb and slower staling rate was obtained compared to the use of common commercial hydrocolloids, psyllium and HPMC, at optimised addition level. Increased dissolution of ß-glucan and removal of insoluble fraction from OBC likely enabled ß-glucan to bind water better in the dough and resulted in even distribution of dough water and improved hydration of dough components. The results of this study provide better understanding about factors affecting the baking properties of oats, and the findings can be utilised in design of new oat bakery products.