It was recently proposed that the in vitro protein solubility is better to classify animal by-product meals (ABP) using pepsin concentration of .0002% than with higher concentrations. However on this concentration no reference value exists to express ABP quality based on protein solubility. The objective of this study was to obtain protein solubility values for poultry by-product meals (PBP), as model to ABP. Two PBP and casein (considered 100% soluble protein) were used as protein sources. All meals were autoclaved at 120ºC, during 0, 10, 20, 40 and 80 minutes. Concentrations of pepsin on acid HCl 0,0744N were 0.0002 and 0.02%. The experiment was carried out according to a completely randomized design with factorial scheme 3 (sources) x 5 (temperatures) x 2 (concentrations), with four replications for enzyme concentration of 0.0002% and two replications for enzyme at 0.02%. It were determined the in vitro protein solubility values on acid/pepsin solution and the in vivo metabolizable energy of PBP meals. The results indicated that on pepsin concentration of 0.0002%, the values of good quality PBP are over 55%. In the same way, solubility close to 84% could be considered good quality source, but decreasing solubility are considered bad quality with 67% on pepsin at concentration of 0.02%.
methodology; digestibility; protein ingredients; animal by-products
