Obtaining and characterization of protein isolates from porcine heart and liver

Abstract

The need to use meat by-products provided the objective of evaluating the effects of different extraction solutions (aqueous and saline) and nitrite addition in the protein recovery steps of heart and liver porcine obtained by the pH-shifting technique. Protein solubility curves were performed and the optimal pH of solubility (PS) and precipitation (isoelectric point; PI) defined for both by-products and solutions. The concentration of total soluble protein in PS was higher (P<0.05) in liver extract than in heart extract. Increasing additions of nitrite increased (P<0.05) the residual nitrite content (NO2R) and favored the formation of the pinkish-red color by increasing the red index (a*) and reducing the shade angle (h°), especially in salt. Next, porcine hearts (HIP), extracted in aqueous solution (HIPaq) or saline (HIPsal) with or without sodium nitrite were dried by lyophilization and characterized. The treatments did not influence

the protein content of the isolates, but the HIPsal showed a higher (P<0.05) proportion of salt- soluble proteins and a lower proportion of insoluble proteins than the HIPaq. The color of

HIPsal was lighter (P<0.05) and less intense (P<0.05) than that of HIPaq. Treatment with nitrite reduced (P<0.05) the h values, making the samples redder. Saline extraction (P<0.05) reduced the emulsion stability (EE) and nitrite treatment reduced (P<0.05) the EC and EE of the isolates. All HIPs had a high content of iron and calcium and all essential amino acids (EAA) with scores above the required, except for valine in HIPsal. Similarly, porcine livers (LIP) were also extracted in aqueous solution (LIPaq) or saline (LIPsal) with or without sodium nitrite, lyophilized and characterized. LIPsals had a higher protein content (P<0.05), in addition to a higher proportion of salt-soluble proteins than LIPaq. The color tone was the same (P>0.05) for all isolates, however, the LIPsal sample with nitrite showed a less intense color (P<0.05) than the others. The LIP showed good emulsifying capacity (EC) and ES, similar (P>0.05) to commercial references; still, PLI salt added with nitrite exhibited the best (P<0.05) oil holding capacity (ORC). In addition, LIP contained high iron content, with LIPsal having a higher proportion of heme iron. The LIP contained all the AAE, with high scores and high estimated protein efficiency. Thus, there is a high potential for obtaining protein isolates from by-products porcine and their use as techno-functional or nutritional ingredients. The HIP exhibited a more attractive color treated with nitrite and good nutritional properties, and the LIP, in addition to demonstrating to be nutritionally viable, with a high concentration of iron, presented technological properties close to those of proteins on the market.