Nutritional and techno-functional characterization of protein isolates obtained from porcine heart.

Abstract

Given the growing demand for protein sources and the premise of meeting global requirements, there is a need for more efficient use of by-products generated in the slaughter process, like pig heart, which in turn are highly nutritious and also have the capacity for techno-functional application. The pH-shifting technique using aqueous solutions allows the efficient recovery of proteins of high nutritional quality and with improved functional properties, but the muscle protein extraction could be improved using saline solutions that directly influence the yield and final quality of the protein isolate. However, the muscle heme pigments oxidize during extraction, generating a blackish color of the isolates, making their use in foods less attractive. An alternative would be to use nitrite salts in the extraction solution since they interact with heme pigments forming a reddish heat-stable nitrous pigment. Thus, this study aimed at obtaining and characterizing proteins isolated from the porcine heart (HPI), extracted with aqueous (HPIaq) or saline (HPIsal) solutions, stabilized or not with sodium nitrite. Treatments did not influence the isolates' protein content (89.0%), and HPIsal had a higher salt-soluble (53.8 vs. 47.0%) and lower insoluble (19.2 vs. 24.1%) proteins content than HPIaq. The total heme pigments and collagen contents were unaffected by the extraction solution, but they were higher in samples treated with nitrite (921.6 vs. 707.6 μg hematin per g). Saline extraction only reduces the color intensity (C* = 9.1 vs. 12.7), but HPIs extracted with nitrite had a lighter (L* = 62.4 vs. 59.2), reddish (h = 65.7 vs. 69.5°) and less intense color (C* = 26.5 vs. 30.7). The oil retention, water absorption, and emulsifying capacity (EC) of isolates were not affected by the extraction solutions, but the saline extraction reduced the emulsion stability (ES) and the nitrite-based-treatment reduced EC and ES. The isolates contained high levels of iron (165.8