Highlights

• •Protein in soy-based meat analogues has high digestibility and DIAAS.
• •Soy-based meat analogues are good-excellent protein sources for humans.
• •Environmental impact drivers are cultivation, protein extraction and drying.
• •Optimal DIAAS per environmental impact in extruded, mildly extracted soy protein.

Abstract

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>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.

Critique

The authors are commendably honest about the "limitations" and failures of their pilot-scale production, particularly the "incomplete defatting process". They openly state their self-produced intermediates are not "fully representative of industrially produced ones"

The study uses one single soybean cultivar ("Protéix") and one commercial soy protein concentrate (SPC). This is a convenience sample, not a representative one. Conclusions cannot be generalized to "soy-based meat analogues" when the raw material is a single, non-randomly selected cultivar.

The authors admit their pilot-scale process failed. Their self-produced intermediate products (SWF, SPC, and SPI) had "substantially" high fat content (15-21%) instead of the <1% industrial target. These are, by the study's own admission, not representative products.

That said, we'd probably expect the digestability found here to roughly approximate real products: while the study's starting ingredients were flawed and unrepresentative (with <60% digestibility), the final extruded products ended up in the same place as the commercial reference: very high digestibility (>95%)