Impact of hurdle technologies and low temperatures during ripening on the production of nitrate-free pork salami: A microbiological and metabolomic comparison

In this work, cold-dry fermented nitrate-free sausages were produced by adopting hurdle technologies. The strategy consists of using lactic acid bacteria (LAB) growing at low temperatures, the addition of lactic and ascorbic acids, and low temperatures during the ripening-drying process (35 days at different RH values). Four experimental conditions (B and B1 with 0.2% ascorbic acid, R and R1 with 0.3% lactic acid – B1 and R1 with lower RH during ripening) were compared with a control (N; traditionally manufactured, 80 mg/kg of nitrates and nitrites). Overall, sample R underwent a pH change from 5.22 (t0) to 5.06 (t14). Besides, all samples displayed aw values ≤ 0.92 at t22, thus reaching values < 0.895 at t35. Interestingly, the lower RH values (65–80%) during ripening determined a case hardening, significantly affecting colour parameters. Metabolomics coupled with TBARS assay showed few differences when comparing B and R with the control, whereas lipid oxidation markers (18-hydroxyoleate, LogFC = 0.83–16-Hydroxy-hexadecanoic acid, LogFC = 0.77) and MDA increased in B1 and R1. Overall, RH values revealed to be critical parameters, to be accurately defined to avoid undesired phenomena when hurdle technologies are used. Nonetheless, our findings support the manufacturing of nitrate-free salami by unconventional technologies.