Effect of Gamma-irradiation and/or Extrusion on the Nutritional Value of Soy Flour

Although soybean is rich with its high amount of protein, phenolic compounds and other bioactive nutrients, their bioavailability and utilization by either humans or animals are relatively low due to the presence of high proportions of various antinutrients. The aim of the present study was the investigation of the use of ?-radiation and/or extrusion for inactivation or removal of certain antinutritional factors. Also, the effect of these processing methods on the nutritional value of soy flour was studied. Analysis included estimation of the proximate composition, level of some antinutrients and the concentration of total phenols of raw and processed soy flour. In addition, amino acids content was analyzed by using high performance amino acid analyzer-Biochrom 20. Gas chromatography was used for analysis of fatty acids; phenolic compounds were determined by high performance liquid chromatography. The results showed that the proximate composition of soy flour was unchanged by the irradiation (5 & 10 KGy) and/or by extrusion except the moisture content was decreased by extrusion. ?-irradiation and/or extrusion processing significantly reduced the levels of phytic acid, tannins, and trypsin inhibitor while the total phenols was increased compared to the unprocessed control samples. All essential amino acids, fatty acids and phenolic compound were significantly changed. From these results, it is possible to demonstrate the benefits of ?-irradiation and/or heating extrusion processing on the nutritional properties of soy flour through reducing its antinutritional contents and improving some of functional nutrients.