In vitro DIAAS of Swiss soybean cultivars using the INFOGEST model: Increase in protein quality from soybean to soymilk and tofu.

To support the transition towards more sustainable and healthy diets, viable alternatives to foods of animal origin need to be identified. Many plant-based protein sources are currently marketed with claims of minimal environmental impact, but very limited consideration has been given to their protein quality and bioavailable mineral content considering the fact that animal-based foods are typically the primary source of both in Western diets. In this study, traditionally consumed soy foods (cooked soybeans, soymilk, tofu) from different Swiss soybean cultivars were nutritionally characterized and the in vitro digestibility of individual amino acids and total protein were assessed using an in vitro model based on the static INFOGEST protocol; the protein quality was evaluated using the in vitro digestible indispensable amino acid score (DIAAS). The results reveal an increase in total protein in vitro digestibility across the traditional soy food production value chain: 52.1-62.7% for cooked soybeans, 84.1-90.6% for soymilk, and 94.9-98.4% for tofu. Protein quality, determined using the recommended amino acid pattern for 0.5-3 years old, was "low" (no claim) for cooked soybeans (DIAAS < 60), while soymilk (DIAAS = 78-88) and tofu products (DIAAS = 79-91) were of similar "good" protein quality, with considerably higher DIAAS values than those of cooked soybeans (P < 0.001). The iron and zinc contents in soy foods were substantial, but high molar ratios of phytic acid (PA) to iron (PA/Fe; >8) and PA to zinc (PA/Zn; >15) indicate a possible strong inhibition of iron and zinc bioavailability. Based on the DIAAS results, soymilk and tofu would be suitable plant-based alternatives to animal-based foods, while future efforts should focus on optimizing soybean preparation to overcome the negative effects of the plant tissue matrix as well as processing steps to reduce mineral absorption inhibiting substances.

Identification of mega-environments in Europe and effect of allelic variation at maturity E loci on adaptation of European soybean.

Soybean cultivation holds great potential for a sustainable agriculture in Europe, but adaptation remains a central issue. In this large mega-environment (MEV) study, 75 European cultivars from five early maturity groups (MGs 000-II) were evaluated for maturity-related traits at 22 locations in 10 countries across Europe. Clustering of the locations based on phenotypic similarity revealed six MEVs in latitudinal direction and suggested several more. Analysis of maturity identified several groups of cultivars with phenotypic similarity that are optimally adapted to the different growing regions in Europe. We identified several haplotypes for the allelic variants at the E1, E2, E3 and E4 genes, with each E haplotype comprising cultivars from different MGs. Cultivars with the same E haplotype can exhibit different flowering and maturity characteristics, suggesting that the genetic control of these traits is more complex and that adaptation involves additional genetic pathways, for example temperature requirement. Taken together, our study allowed the first unified assessment of soybean-growing regions in Europe and illustrates the strong effect of photoperiod on soybean adaptation and MEV classification, as well as the effects of the E maturity loci for soybean adaptation in Europe.