Inativação de inibidores de tripsina na mamona (Ricinus Communis L.) processada industrialmente após tratamentos térmico e químico

Abstract

Castor bean seeds contain antinutritional factors, and industrial processing to obtain the oil may or may not inactivate the trypsin inhibitors. The loss of activity of these factors would increase the safety of the residue generated for use in animal feed. Particle size, temperature, heating time, pressure, humidity of the material and the environment, as well as the use of chemical compounds may contribute to the efficiency of protocols for inactivating antinutritional factors of protein origin. In this context, the present study aimed to inactivate the trypsin inhibitors present in the industrial processing stages of castor bean seeds using thermal and chemical treatment protocols and to partially characterize them. Initially, samples from the last three stages of industrial processing (STEP 3 (E3) castor bean cake, STEP 4 (E4) castor bean meal with hexane, STEP 5 (E5) desolventized castor bean meal) of the seeds were crushed and flours with 0.5 mm particle size were obtained. For the heat treatment of the last three steps, moist heat under pressure (121°C, at 1.10 kg/cm², for 20 min and 60 min) was applied to samples of dry flours or flours previously hydrated with water in a ratio of 1:1.5 (w/v). For the chemical treatment, CaO was added in a ratio of 1:0.09 (w/w) and water at 55°C in a ratio of 1:1.5 (w/v). Samples from the last step of industrial processing were also treated with dry heat (150°C, for 60, 120 and 180 min). All flours, in the different steps of industrial processing, treated or not, were subjected to protein extraction using water as solvent in a ratio of 1:3 (w/v). In the chemical treatment, to remove CaO before extraction, the samples were dialyzed in 2 kDa membranes and, subsequently, the volume was adjusted to a ratio of 1:10 (w/v). After diluting the flours, protein extractions were similar, occurring under constant agitation for one hour at ± 25°C, followed by centrifugation at 10,000 x g for 30 min at 4°C. The proteins present in the extracts from the last stage of industrial processing were further fractionated using 2 and 12 kDa membranes and with ammonium sulfate in the ranges of 0-30%, 30-60% and 60-90%. The specific trypsin inhibitor activity (IU/mg of protein) was determined in all extracts and fractions. Only chemical treatment with CaO was able to completely inactivate the trypsin inhibitors in castor bean meal. Through fractionation with ammonium sulfate, it was observed that in the last stage of industrial processing there is the presence of more than one trypsin inhibitor, observing inhibitory activity in all protein fractions (0-30%; 30-60% and 60-90%). In addition, these inhibitors have low molecular weight, since activity was only observed in the fraction between 2 and 12 kDa. The high thermal resistance of the trypsin inhibitors from castor bean meal shows a highbiotechnological potential of these molecules, in relation to plant defense characteristics, but also reinforces the need for the addition of chemical treatment after industrial processing to make castor bean meal safer for animal feed, promoting reuse, adding value to the residue, while pointing to future research on safe and efficient application in the animal feed industry.