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Influence of the origin of the beans on the chemical composition, particle size distribution, and color of soybean meal

Kadardar, H., L. Aguirre, G. Fondevila, M. Elkissi, G. Mateos and L. Cámara

We studied the influence of the origin of the soybean on the chemical composition, protein quality, particle size distribution (PS), and color of commercial soybean meals (SBM). A total of 50 SBM samples from Argentina (ARG; n=10), Brazil (BRA; n=10), USA (n=15), and South Africa (SA; n=15) were used. Samples from SA were collected from crushing plants in the country of origin whereas for the other 3 origins the samples were obtained in crushing plants different European locations or at the arrival of the vessels to European ports. The samples were analyzed for main components (proximal analyses, sucrose, oligosaccharides, CF, NDF, and mineral content), protein quality indicators [urease activity (UA), KOH solubility (KOH), protein dispersibility index (PDI), and trypsin inhibitor activity (TIA)], PS distribution [geometric mean diameter ± standard deviation (GMD ± GSD)], and color [L* (luminosity), a* (redness), b* (yellowness)] using Minolta camera. Data were analyzed by the GLM procedure of SAS, with origin of the SBM as main effect. In addition, Pearson correlation (r) analyses were conducted to determine the relation between chemical values and color of the SBM using the CORR procedure of SAS. On 88% DM basis, no differences in CP content were detected among SBM origin. The BRA meals had more NDF, raffinose, and Fe but less sucrose and stachyose than the SA meals, with the ARG and USA meals being intermediate (P<0.001). PDI and KOH values were higher for the USA meals than for the South American meals, with the SA meals being intermediate (P<0.01). TIA tended to be higher for the SA and USA meals than for the South American meals (P=0.06). Particle size uniformity was better for the SA and USA meals than for the South American meals (P<0.05). Also, the BRA meals had lower L* and higher a* values than the SA meals, with ARG and USA meals being intermediate (P<0.001). Independently of SBM origin, the greatest correlations were observed between Fe content and L* (r = -0.527; P<0.01) and the a* (r = 0.293; P<0.05) values of the meals. Also, UA, PDI, KOH, and TIA were negatively correlated with the a* Minolta value (r = -0.429, -0.353, -0.482 and -0.766, respectively; P<0.01). The higher a* values of the BRA meals, might reflect the high acidity of the soil and the greater Fe content of the beans produced in this area. The correlation between a* and the PDI value may reflect that extra heat was applied to the BRA beans at the farm to dry the seeds.

In summary, chemical composition, protein quality, PS distribution, and color varied widely among commercial SBM according to bean origin.