In vitro digestibility of protein with enzymatic crudes, obtained from residues of the slaughter house

In order to study the in vitro digestibility of protein with enzymatic crudes enriched with pepsin substituting the commercial enzyme, residues from the experimental slaughter house of the Institute of Animal Science (ICA) were used. Two enzymatic crudes were obtained from 100 g of gastric mucus taken from bovine abomasum and porcine stomach of recently slaughtered animals. Both crudes were characterized using electrophoresis and zymography. The content of total proteins and enzymatic activity were determined. They were purified using polyethylene glycol (PEG)/phosphate two-phase systems. The proteolytic activity of crudes, and their purified fractions, was compared to the commercial pepsin through studies on in vitro digestibility of protein. A completely randomized design, with a 3 x 3 factorial arrangement was used, fixed in three treatments (commercial enzyme, porcine homogenate (HP) and bovine homogenate (HB)) and three times of incubation (2, 4 and 6 h). Crudes presented high concentration of total proteins (HP 27.19 g.L-1 and HB 21.34g.L-1) and high enzymatic activity, expressed in g.L-1 of pepsin (HP 1.16 and HB 0.47). Pepsin within the crudes had a similar performance to the pattern enzyme of two-phase systems. It was concentrated in the superior phase, which was rich in PEG. Purification indicators for both crudes showed a purification factor superior to 3 and yields higher than 60 %. Digestibility analyses had no differences among treatments. It can be concluded that crudes and their purified fractions can be used for the analysis of in vitro digestibility of protein. Key words: crudes, pepsin, two-phase systems, in vitro digestibility