Comparison of a commercial soybean cultivar and an isoline lacking the Kunitz trypsin inhibitor: composition, nutritional value, and effects of heating

Abstract

The content and heat stability of protease inhibitors of a standard cultivar (Williams 82) and an isoline (L81-4590) lacking the Kunitz trypsin inhibitor (KTI) were measured by using enzyme inhibition and enzyme-linked immunosorbent assays (ELISA). The KTI content of the isoline was less than 0.2% compared to Williams 82, with the exact content depending on the extent of cross-pollination of the soybeans. Steam heating of the isoline flour (121 °C, 20 min) resulted in a near-zero level of trypsin inhibitory activity, while 20% remained in the Williams 82 sample. The raw soy flour prepared from the isoline was nutritionally superior to the raw flour prepared from the standard variety, as measured by PER and pancreatic weights. The increased PER was likely due to the lower level of trypsin inhibitory activity in the isoline. Steam heating the flours for up to 30 min at 121 °C progressively increased the PER for both strains. Screening of several accessions from the USDA Soybean Germplasm Collection showed variation in the content of trypsin inhibitor, sulfur amino acids, and lectins, indicating that further screening studies could lead to the discovery of soybeans which yield flour that is safe and nutritious, with minimal heating.

The influence of strain and age on some egg quality parameters of commercial laying hens

“…Extrusion also leads to starch gelatinisation and reduces the activity of trypsin inhibitors, which improves the conditions for efficient digestion of proteins in the small intestine of pigs (O'Doherty and Keady, 2001) and chickens (Arija et al, 2006). Crude genetically enhanced soybeans (Soja Lana) was as expected had a much lower level of trypsin inhibitors in comparison with the standard raw soybeans, as Kunitz trypsin inhibitor antitrypsin, main component of the seed (Friedman et al, 1991). Soybean varieties with low levels of Kunitz inhibitors may have different levels of trypsin inhibitors, depending on the spot they are grown (Kumar et al, 2003), the presence of other types of trypsin inhibitors (Tan- Wilson et al, 1987), variations in the level lipoksigegenase (Machado et al, 2008) and anti-nutritive factors such as phytates and tannins (Liener, 1994).…”

“…The growth depression could be explained by other heat-labile antinutritional factors present in raw soybeans -Bowman-Birk trypsin inhibitor and lectin. Previous results suggest that simple removal of Kunitz inhibitor without any intervention upon Bowman-Birk inhibitor, although allowing a reduction of processing costs (Friedman et al, 1991) does not appear to solve a problem of direct livestock nutrition.…”

“…Nevertheless, KTI free soybean cultivars can offer nutritional advantages, since they need a shorter heating time for inactivation of trypsin inhibitors (Friedman et al, 1991). Furthermore, such varieties might be processed more economically into human foods as well.…”

“…Palacios et al (2004) have obtained results by genetically improved strains that had better quality than standard soy protein, but Machado et al (2008), in its biological assay did not perceive significant differences when the two varieties of soybean were thermally treated in the same way. This can be explained by different levels of lectins in different cultivars of soybean (Friedman et al, 1991). Differences in the quality of protein are expected due to variations in the quantity of different types of trypsin inhibitors and other anti-nutritive components in different varieties of soybean (Liener, 1994).…”

Soybean: feed quality and safety. Part 1: Biologically active components. A review

“…Han et al (1991) reported that raw Kunitz-inhibitor-free soybean (KFSB) has better nutritional value than conventional raw soybean but lower than commercial soybean meal in chicks. The raw KFSB has 16 times lower trypsin inhibitor content than commercial soybean meal, but the Birkman inhibitor contents were similar (Friedman et al, 1991). This means that KFBS requires the same heat treatment as commercial soybean meal.…”