Nutritional Value of Differently Processed Soybean Seeds

BACKGROUND AND OBJECTIVES: Soybeans have been used in human and animal nutrition because of their favorable agronomic characteristics, relatively low price, high quality and quantity of protein and oil as well as their important functional properties for the development of different types of foods for humans. However, Raw Soybean Seed Meal (RSSM) contain high levels of anti-nutritional factors (ANFs), such as protease trypsin inhibitors, lipase inhibitors, goitrogens, and hemagglutins, which must be deactivated by proper heat treatment prior to inclusion in animal and human diets. The main objective of this study was to determine the nutritional and anti-trypsin content of raw soybean seeds in comparison to the solvent extracted and steam cooked soybeans. MATERIALS AND METHODS: The proximate composition, minerals and anti-trypsin content of raw soybean seeds and differently processed soybean seeds were determined using standard methods. One way Analysis of Variance (ANOVA) was used in analysing the data. RESULTS: The moisture content of solvent extracted soybean seeds (SES) (6.7±0.2 % ) was significantly higher than Raw Soyean Seed Meal (RSSM) and Extruded Full-Fat Soybean Seeds (EFFS) (P<0.05). EFFS seeds had lower ash content (4.4±0.1%) as compared to the SES and RSSM. SES had significantly very low crude fat content (2.7±0.2%) than EFFS and RSSM (P<0.005). SES had higher crude protein content (48.9±0.6%) than EFFS and RSSM. RSSM had significantly higher calcium content (1.81±0.007 %) than both EFFS and SES seeds (P<0.05). There was a significant difference in phosphorous content among all the soybean seeds with RSSM having the highest content (0.96±0.1) and EFFS seeds having the lowest (0.59±0.06%), (P<0.05). There was a significant difference in trypsin inhibitor content in raw and different processed soybeans with RSSM having the highest concentration (54.0±1.5) while EFFSs had the lowest content (1.0±0.03 mg inhibited Trypsin/g). The highest essential amino acid content in EFFS, SES and RSSM seeds was arginine (8.67±0.3) ,(8.69±0.5) and (7.77±0.3g/16g N) respectively. While the lowest essential amino in raw and differently processed soybeans was methionine with SES having the lowest concentration (1.46±0.2g/16g N). The results further indicate that EFFSs had the highest concentrations of all the non-essential amino acids apart from cystine which was slightly higher in SES than in EFFSs whilst glutamic acid was the highest non-essential amino acid obtained in EFFSs. RSSM had lower amount of all the non-essential amino acids apart from tyrosine as compared to SES and EFFS though the differences were not significant (P>0.05). CONCLUSIONS: Soybeans processed by steaming (EEFS) could be used as a protein and energy source at the village level as the method is easier and cheaper to use while it maintains most of the nutrients and removes the antnutrient factors.