Sourcing added value food ingredients from home-grown oats

Abstract

A study was carried out to examine the potential for the fractionation of oat grains and the use of the resultant components as food ingredients. The study included the following elements:

Assessment of agronomic and environmental effects on grain composition
Development of a dry milling process for oats
Analysis of the properties of oat components following dry milling
Evaluation of the properties of oat flour as a thickener in a béchemal sauce mixture
A literature review of oat fractionation technology
Grain quality is likely to be an important aspect for oat fractionation and guidelines for oat growers are necessary in order to meet the demands of this market - quality criteria will be more stringent than in other areas where oats are traded. Grain protein content can be largely controlled by the grower through application of appropriate amounts of nitrogen fertiliser as ammonium nitrate or foliar urea but b -glucan and oil contents are more difficult to control and mostly vary due to variety. b -glucan content was increased in the study through application of foliar urea though further studies are needed to understand the mechanism for this effect. The effect of foliar urea on b -glucan content has significant implications for the growing of oats and provides a means by which the value of the crop can be increased in many markets.

It was demonstrated that dry milling followed by sieving can be used to prepare starch-rich and bran-rich flours streams. The starch-rich stream contained typically 60% starch, 9% protein and 1% b -glucan while the bran-rich stream contained 48% starch, 15% protein and 5% b -glucan. It was necessary to dehull oats prior to milling but otherwise there were no problems using this technique. Adjustment of mill parameters was necessary to optimise the extraction of components into the flour streams and maximum separation was achieved using a three pass process in which the oversieve material at each stage was passed through the mill again. Further refinement of the milling than that in the study may yield greater separation of components and there was evidence that aspects of grain quality (as yet unidentified) may impact on the efficiency of the process.

Studies of isolated components were concentrated on starch, b -glucan, antioxidants and polar lipids with emulsifier properties. Starch properties were shown to be similar to those published in the literature and did not appear to be affected by agronomy or environment. An important finding was the presence of significant amounts of a -amylase activity in some samples. There were no significant differences in b -glucan properties which related to agronomic or environmental treatments. There was evidence that extraction efficiency of b -glucan can be affected by variety and foliar urea application and if proven this could have crop management implications. Significant antioxidant activity was found in the flour samples. This was not affected by agronomy but there was evidence that it may be affected by soil water availability. There was also some evidence that milling may be a critical stage in the recovery of antioxidant activity. The glycolipid emulsifier was identified in milled flours but the level did not appear to be affected by any of the factors in the study, in contrast to earlier studies which indicated large differences due to site.

The properties of oat flour in béchemel sauce preparations was compared with chemically modified maize starch and wheat flour. The oat flour was found to be acceptable for this purpose and sensory properties of the sauce were comparable to sauces prepared with the other thickeners.

The project demonstrated that considerable potential exists to source food ingredients from oats with dry milling as a preliminary separation stage. A review of processes available for fractionation of oats revealed that patents surrounding existing processes are not likely to be a barrier to commercialisation of a process. Further impetus is likely to come from examination of the other oat components which were beyond the scope of this study and also markets for components in other industry sectors. Some of these additional studies are currently being examined by the Objective 5B funded Oatec project.