Impact of Low Moisture Extrusion on Reducing Anti-Nutritional Factors and Enhancing Nutritional Value and Protein Properties in Oilseed Blends

Oilseed cakes, including rapeseeds, hemp, and flaxseeds, boast a high protein content, positioning them as sustainable sources of protein. However, the utilization of these oilseeds in food products is largely restricted due to the presence of considerable anti-nutritional factors. Meanwhile, extrusion technology has gained prominence for producing high-quality ingredients, particularly for plant-based meat alternatives.

This study employed low moisture extrusion on oilseeds with the objective of reducing anti-nutritional factors, enhancing nutritional value, and altering the protein structure and characteristics for improved usability. Three types of oilseeds were blended with either pea or hemp protein in a 50:50 w/w ratio. This strategy aimed to modify amino acid profiles and augment the overall protein content. The oilseed blends underwent low moisture extrusion (at 10% and 20% moisture levels) with a barrel temperature of 120°C.

The extrusion process did not adversely affect the protein content. It notably reduced protein solubility by up to 44.5% and increased in vitro digestibility by 13.5%. Regarding polyphenol content, a significant reduction was observed in rapeseed and flaxseed blends (up to 47.6%) post-extrusion. A substantial decrease in anti-nutritional factors was evident, with saponins reducing by 9.6 - 29.9%, condensed tannins by 22.9% - 44.6%, and trypsin inhibitors from 1.1 to 11.9 TUI/mg in the extruded samples. However, the extrusion process had a limited impact on phytic acid reduction. The process generally led to a marked reduction in surface hydrophobicity, disruption of hydrophobic interactions, and alterations in protein profiles under non-reducing conditions. 

These findings underscore that extrusion cooking significantly enhances the quality of under-utilized oilseeds, rendering them as promising ingredients for diverse food applications, such as in the formulation of plant-based meat analogues. This advancement aligns with the goals of sustainable food production and offers a potential pathway for the valorization of oilseed cakes in the food industry.