Strategies for decelerating the deterioration of fats in extrudet wholegrain products

Research institutions:

1. Institute for Food and Environmental Research (ILU) Nuthetal
2. German Institute of Food Technologies (DIL), Quakenbrück

For the production of high-quality wholemeal extrudates from wheat and oats, raw materials with good grain formation are necessary in order to guarantee a favourable ratio of endosperm and marginal layers. The cereal remains in perfect sensory condition during storage as long as the grains are dry and have a low aw-value. Enzymatic changes are inhibited. The surface is significantly enlarged by the grinding, fat and fat-oxidizing enzymes are "activated" by air and warming during the grinding process, and the proportion of natural antioxidants is reduced. Between grinding and extrusion, the storage period should be as short as possible. In extrusion, specific mechanical (SME) and thermal energy input (mass temperature) enables the required material conversions to be achieved in order to produce loosened extrudates. In wheat with comparatively little fat, under gentle extrusion conditions, no oxidative fat spoilage is sensory detected on freshly dried and stored extrudates within the BBD. Oats as extrusion raw material were investigated with different degrees of processing. The extrusion of oats with a higher fat content, at higher extrusion moisture levels, also requires drying, i.e. additional thermal stress forces fat oxidation. During extrusion the fat binding is increased, i.e. the extractable fraction (EFA) decreases. The higher the fat bond, the better the fat is protected against oxidation. If the SME is significantly increased, this leads to an acceleration of the fat spoilage. The intensity of the formation of rancid oxidation products is significantly increased by the drying conditions. High thermal stress is a major factor influencing fat oxidation. The conditions have been created to forecast the stability of extruded products on the basis of a new evaluation using a Rancimat curve.

This IGF project of the FEI was supported via AiF within  the programme for promoting the Industrial Collective Research (IGF) of the German Ministry of Economic Affairs and Energy (BMWi), based on a resolution of the German Parliament. Project AiF 18753 BG