Lactiplantibacillus plantarum YR07 Fermentation: A Nitrite-Free Zinc Protoporphyrin Coloring Strategy for Fermented Sausages

Nitrites, commonly used as coloring agents in traditional meat processing, can generate carcinogenic N-nitrosamines. This study developed a microbial fermentation-based coloring technology to replace nitrites. A fermented sausage model included five treatments: control; nitrite-added (50 mg/kg); and three treatments inoculated with food-grade probiotics ( Lactiplantibacillus plantarum YR07, Latilactobacillus sakei L48, Latilactobacillus curvatus WQ). Colorimetric analysis showed that on day 7 the YR07 treatment showed significantly higher redness (a* 9.17 ± 0.10) than control (7.38 ± 0.10), L48 (7.52 ± 0.35) and WQ (6.76 ± 0.14) treatments ( p < 0.05), approaching the nitrite-treated treatment (10.55 ± 0.05). UV-Vis spectroscopy confirmed characteristic nitrosylheme in nitrite-treated sausages, whereas zinc protoporphyrin (ZnPP) dominated probiotic-inoculated treatments. Fluorescence spectroscopy further demonstrated sustained highest intensity in YR07 during processing. ZnPP content on day 7, with the YR07 treatment showing significantly higher levels (5.16 ± 0.09 mg/kg) compared to the control (1.98 ± 0.04 mg/kg) and nitrite-treated treatments (0.50 ± 0.03 mg/kg) ( p < 0.05). Ferrochelatase activity in YR07-inoculated sausages (134.54 ± 2.96 U/g) significantly exceeded ( p < 0.05) both the control (102.01 ± 1.09 U/g) and nitrite-treated treatments (9.75 ± 0.72 U/g), demonstrating nitrite's inhibitory effect on the enzyme. HPLC analysis on day 7 showed that YR07-inoculated (13.32 ± 1.36 mg/kg) and nitrite-treated sausages (10.53 ± 49 mg/kg) contained less heme than the control (19.65 ± 0.31 mg/kg), suggesting heme may serve as substrate for ZnPP biosynthesis. This study not only provides a feasible microbial alternative to nitrite but also elucidates the potential mechanism of ZnPP formation.