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Fermentation of soybean meal results in a net reduction of heat-labile and heat-stable antinutritional factors

Ruiz, N., A. Robles-Montes and J. van Eys

A proprietary fermentation process of soybean meal (SBM) was developed at a Central America oilseed processing plant. In brief, the process is based on a dual solid-state fermentation of Hi-Pro SBM using a combination of specific Aspergillus spp. and Bacillus spp. inoculum. Fermentation took place under semi-anaerobic conditions and prevailing ambient temperatures (25 – 35oC). Moisture levels during fermentation were maintained at 55% and fermentation progress was controlled through repeated measures of temperature, pH and sugar content. Fermentation was halted by low temperature drying to humidity levels of 10%. The objective of this presentation is to report the effect of fermentation on the net content of heat-labile and heat-stable antinutritional factors of soybean meal. Student’s t-test was used to differentiate the analytical means of SBM versus those of FSBM. The results for at least six industrial productions of fermented soybean meal versus their unfermented SBM were as follows: trypsin inhibitors significantly decreased (P<0.001) from 2.56±0.42 mg/g in SBM (N=8) to 0.97±0.14 mg/g in FSBM (N=6). Sucrose significantly decreased (P<0.001) from 5.91±0.87% in SBM (N=6) to 0.05±0.04% in FSBM (N=26). Raffinose significantly decreased (P<0.001) from 1.28±0.45% in SBM (N=6) to 0.08±0.07% in FSBM (N=26). Stachyose significantly decreased (P<0.001) from 4.86±0.94 (N=6) to 0.13±0.09% in FSBM (N=26). Fermentation also resulted in an important reduction in lectin content and increase in organic acid content most notably lactic acid from non- detectable in SBM to 6.16±0.22% in FSBM (N=13). Similarly, fermentation also increase acetic acid from non- detectable in SBM to 0.52±0.27% in FSBM (N=13).

In conclusion, fermentation of SBM − by the process as described above − improves the nutritional characteristics and should allow for greater incorporation of diets in young and sensitive.