The pigment transformation from nitrosylheme to Zn-protoporphyrin IX in cooked ham products

In this study, we investigated cooked hams to understand the relationship between display life and quality changes, as well as the microbiological characteristics of refrigerated storage for up to 90 days. Initially, the L* and a* values exhibited an initial decline with a gradual restitution to levels insignificantly disparate from those Day 15 hams. In contrast, the b* and h° values demonstrated an ascending pattern, indicating an augmentation in yellow intensity during the storage. Furthermore, there was an observable escalation in the C* value following 45 days of storage, implying an amplified luminosity and vividness of color during the latter phase of the storage period. Analyses of TBARS, TVB-N, and other physicochemical indexes indicated that the hams underwent deterioration during storage. Whereas, UV–vis and fluorescence spectroscopy illustrated that the pigment in cooked hams changed from nitrosylheme (NO-heme) to Zn-protoporphyrin IX (ZnPP) during storage. The NO-heme content decreased from 41.08 ± 0.44 to 12.76 ± 0.29 mg/kg, while the ZnPP content increased from 12.19 ± 0.41 to 89.44 ± 1.57 mg/kg. The structure of the bacterial community in the ham samples changed over the storage period. Towards the end of the shelf life, the microbial population was dominated by Lactic acid bacteria (LAB), particularly Latilactobacillus (34.91%) and Leuconostoc (19.73%). Redundancy analysis and Pearson correlation revealed a positive correlation between Latilactobacillus and Leuconostoc with TBARS, TVB-N, ZnPP content, and negative correlations with Aw and NO-heme.