A novel continuous method to determine the antitrypsin inhibitor activity in soybean derivatives

EZEQUIEL COSCUETA; GUILLERMO A. PICO; MANUELA E. PINTADO; GASTÓN KNOBEL; CARLOS E. BOSCHETTI; LUCIANA PELLEGRINI MALPIEDI; BIBIANA B. NERLI

Salamanca

Congreso; BIOIberoamérica 2016; 2016

At present, soybean is the world's most important oilseed, used not only as oil source but for protein source. However, like other beans and grains, soybeans contain several anti-nutritional factors (lectins, trypsin inhibitors, rafinose, etc). Trypsin inhibitors (TI) are major components reported to cause growth, digestive and metabolic diseases. These factors are heat-labile, therefore, they are able to be removed totally or partially by different treatments during industrialization. The determination of IT content is of importance to evaluate the quality ofprocessing stages. At present, the standard method is based on the ability of extracts of soybean meals to inhibit the activity of trypsin towards a chromogenic substract(Kakade et al. 1974; AOCS 2009). The amount of product formed during incubation is determined through absorbance measurements in presence and absence of soy extract, thus giving differences related to the IT content. It is a discontinuous or stopped assay in which the enzyme (trypsin) is inactivated after the incubation time (10 minutes) by lowering the pH. The overall assay is complicated and does not to fulfill the requirements for quality control in industrial processing of soy-beam derivatives.It presents several shortcomings. In this context, the goal of this work was to overcome the disadvantages by developing an improved continuous assay and to propose an adequate treatment of the data in order to inform the results in standard units (TIU). Furthermore, the analysis of the progress of reaction with time was assessed to determine the optimal conditions that assure a linear relationship between the measurements and the IT content in samples. The modified proposed method involves a continuous spectrophotometric rate determination for trypsin activity. Reactiontakes place directly in the spectrophotometer cuvette reducing volume from 10 to 2.5 mL. The analysis of different samples with a wide range of IT content showed no significant differences (p