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Over-processing of Soybean Meal

Lee, Heuisuck, J.D. Garlish and P.R. Ferket

In a classic Over Processing of Soybean Meal study, the effect of overcooked soybean meals (SBM) on chick growth and amino acid availability, experimental SBMs were custom-prepared at a commercial processing plant by changing the conditions of a desolventizer-toaster (DT) unit. Six progressively overcooked meals were produced by increasing the DT temperature up to 50% and extending DT retention time up to 75% above normal.

The meals measured .05, .03, .01, .09, .00, and .00 ΔpH of urease activity; 6.10, 5.01, 4.62, 4.83, 2.32, and 1.78 mg/g SBM of trypsin inhibitor activity; 92, 89, 91, 88, 81, and 81% of protein solubility in 0.2% KOH; and 46, 43, 41, 40, 23, and 19% of protein solubility in 0.1M borate at 40 C, respectively. Total amino acids were not affected by these heat treatments. Analyses of the soluble carbohydrate extract also found no differences in the degradation of sucrose, raffinose, and stachyose with increasing heat treatment.

In a chick growth experiment with a methionine-adequate, low-protein diet, chicks fed normally- processed SBM showed significantly greater weight gains compared to the chicks fed overcooked SBMs. In a separate study, the research group found significant differences in apparent amino acid availability to growing chicks, but not in true amino acid availability by adult roosters among the four progressively overcooked meals. These results suggest that the temperature or the retention time of a DT unit may be increased by 50% over the usual operating conditions without reducing amino acid availability from SBM.

Lee, H. and J.D. Garlich. 1992. Effect of overcooked soybean meal on chicken performance and amino acid availability. Poultry Sci. 71(3): 499-508

In companion studies, three turkey growth experiments were conducted to evaluate the effect of overcooked soybean meal (SBM) on body weight gain and gain: feed ratio. Soybean meals were custom prepared by changing the temperature and the retention time of the desolventizer-toaster unit at a commercial soybean processing plant. Three different meals were produced mainly by altering retention time from normal to approximately 1.35 and 2.43 times normal operating conditions.

Turkey poults were fed various combinations of the regular and over-processed soybean meal. The researchers concluded SBM did not show a detrimental effect on turkey growth until it was overcooked by 2.4 times the normal conditions. The researchers concluded that usual operating conditions in commercial SBM processing plants are well within the range for producing high quality SBMs for poultry feeds.

Lee, Heuisuck, J.D. Garlish and P.R. Ferket. 1991. Effect of overcooked soybean meal on turkey performance. Poultry Science (1991) 70 (12):2509-2515