French Expeller meal: ways to improve quality through processes

Soybean meal is the main source of non-fodder protein for livestock worldwide. In France, however, the soybean sector is relatively young and still underdeveloped. The literature shows that extruded whole beans have a good nutritional value, but do not allow good oil recovery. Solvent extraction of oil after extrusion is also effective, but the investment required and the health and safety regulations are heavy. This is why the production of expeller cake, partially de-oiled, is becoming a trend. 

The French oilcakes meet the demands of consumers who are concerned about product quality and the sustainability of farming practices, and thus enhance the value of local industries. Unlike conventional plants, expeller plants generally use a cooking-pressing process. Soybean cooking in these units must meet two objectives: degrade heat-labile anti-trypsic factors and preserve amino acid digestibility (lysine in particular, which is sensitive to heat). The ideal conditions for both objectives are difficult to achieve in the cooking process, and it is not unusual to find cakes of poor quality for one of these criteria. 
Observations on industrial sites were carried out as part of the Cap Protéine project (national protein sovereignty plan) and showed that there are difficulties in drying seeds with the conventional cookers used by these plants. Investigations and modeling of the residence time distribution in the cookers showed that the air passing through these cookers was far from moisture-saturated. The result of this poor performance is an excessively long residence time (media > 6 h), leading to losses in protein solubility (< 70%) and therefore protein digestibility. This work has made it possible to propose to the studied factories ways of improving the efficiency of cookers for drying, and of improving the performance of presses to enable them to be at least as efficient with less dry seeds.