Selected Staphylococcus spp. and ZnPP-containing liver extract are nitrite-free alternatives to enhance red colour of dry-fermented sausages

As an alternative to adding pure nitrite sources to dry-fermented sausages, we examined three different strategies involving the addition of two meat-associated coagulase-negative staphylococci (CNS) showing nitric-oxide synthase (NOS) activity, a porcine liver extract rich in the pigment zinc protoporphyrin (ZnPP), and a polyphenol-rich ingredient (NATPRE T-10 CUR HT) alone or in combination with the other strategies. We studied the colour development of nine dry-fermented sausages originating from a meat batter control without nitrite (CTRL-), control with nitrite (CTRL+), inoculated with Staphylococcus equorum (L33), inoculated with Staphylococcus saprophyticus (L49), formulated with a ZnPP-rich extract (ZnPPEx), formulated with NATPRE alone (CTRL-/NATPRE) or in combination with the other strategies (L33/NATPRE, L49/NATPRE, ZnPPEx/NATPRE, respectively). The colour was affected by the treatment, ripening period, and their interaction (P < 0.001). After ripening, all treatments resulted in good colour when compared to the CTRL-. Nitrosyl-heme was always detected, but the CTRL+ treatment and those involving residual nitrite sources through the addition of NATPRE recorded higher values than the other samples, which produced similar results. Treatments involving the addition of the ZnPP-rich ingredient resulted in high ZnPP levels. The aqueous extracts showed the presence of soluble ZnPP forms in the ZnPPEx and ZnPPEx/NATPRE sausages, whereas the addition of nitrite and NATPRE resulted in a loss of myoglobin solubility. The mechanism of NOS-positive staphylococcal strains to maintain colour is unclear, but L49 was able to maintain reduced oxymyoglobin until the end of ripening. These findings reveal the potential of these strategies to promote colour in dry-fermented meats.