Extraction of proteins from aqueous and salt solutions of porcine edible byproducts using the pH-shifting technique

Abstract

The use of aqueous and saline solution and the treatment with sodium nitrite in the protein extraction by the pH-shifting technique of edible pig byproducts (heart and liver) were evaluated. Protein solubility curves were obtained, and the optimal pH of solubility (PS) and precipitation (isoelectric point, pI) were defined. The addition of salt increases the solubility in alkaline pH (11.0) for both byproducts, being set at 2.0 for the liver and 3.0 for the heart. The precipitation yields of the total protein were lower in the aqueous heart extracts (71.75%) than in the other extracts (84.23%), but the precipitation yield of total heme pigments (77.63%) was not affected by the treatments or byproduct type. The yield of protein recovery was higher in liver extracts (68.04%) than in heart extracts (49,98%), regardless of the extraction solution used. The increasing additions of nitrite increased the levels of residual nitrite (NO2R) on the precipitates, but lower additions were enough to favor the formation of the pinkish-red color characteristic of cured meat products, by increasing the redness (a*) and reducing the hue angle (h) color. Higher values of NO2R and a* and lower values of h were also observed in the precipitates extracted by the saline solution when compared to those obtained by the aqueous solution. Thus, the use of saline solutions supplemented with 20 mg/mL sodium nitrite proved to be a viable alternative in protein recovery processes in pig byproducts, especially in livers, being a promising alternative to development of techno-functional ingredients to use in meat products.