Solid-state fermented flaxseed oil cake of improved antioxidant capacity as potential food additive

The influence of fermentation with Rhizopus oligosporus tempe mold (DSM 1964 or ATCC 64063 strain) on the antioxidant potential of flaxseed oil cake was studied. Solid-state fermentation (SSF) process resulted in the slight increase in proteins and the significant loss of lipids. Even 48 h, the shortest fermentation period, caused the significant increase in phenolic content (13–85%), radical scavenging activity (about twofold higher against DPPH•) and reducing power (by 20–30%). Prolongation of the fermentation by 24 or 48 h resulted in further enhancement of antioxidant capacity. The addition of fermented product (ATCC 64063, 96 h) to yoghurt caused twofold increase in its protein content. The amounts of proteins and antiradical compounds released after the in vitro digestion were higher, as compared with yoghurt alone (by 20 and 40%, respectively). These results allow to consider the fermented flaxseed oil cake as a valuable food additive. Practical Applications Solid-state fermentation tempe type is the traditional method of raw materials processing in order to improve the nutritional and organoleptic properties of food, which is often accompanied by their enrichment in the nonenzymatic antioxidants. Flaxseed oil cake fermentation with tempe mold Rhizopus oligosporus resulted in obtaining products of enhanced soluble phenolic content, radical scavenging activity and reducing power. Thus, SSF can be an alternative method of the processing of the industrial waste product, namely, flaxseed oil cake, in order to apply it as the potential functional food additive of high antioxidant capacity.