Influence of processing on protein quality and environmental impact assessment of soy-based meat analogues

While meat is an established source of high-quality protein, limited data exists on plant-based meat analogues, particularly regarding how specific production steps and extrusion conditions affect their protein quality and ecological footprint. We used the Protéix soybean cultivar to produce dry soy protein intermediate products with varying degrees of refinement and employed them to obtain meat analogues by high-moisture extrusion. As a reference, a commercial soy protein concentrate was used to produce meat analogues by high- and low-moisture extrusion. In vitro amino acid (AA) digestibility and in vitro DIAAS of intermediate products and extrudates were assessed and compared to traditional soy-based foods and chicken breast. The meat analogues had high total protein in vitro digestibility (>95 %) irrespective of extrusion type, energy input, and soybean variety. The extrusion process substantially enhanced protein digestibility of mildly refined soy protein powders which had low protein digestibility (<60 %). Consequently, meat analogues based on these raw materials showed the lowest environmental footprint per kg quality-corrected protein - with a fourfold lower global warming potential than chicken, compared to only a 17 % reduction observed for meat analogues based on soy protein isolate. In vitro DIAAS values for all studied meat analogues ranged from 81 to 102 for children aged 0.5 to 3 years and were only limited in sulfur-containing AA. Soy-based meat analogues were equally digestible as tofu and cooked chicken breast, had similar protein quality as soymilk and tofu, and can be good to excellent protein sources for humans.