There is a growing demand for clean-label products. This study aimed to obtain a food-grade coloring ingredient for meat products based on the formation of Zn-protoporphyrin from porcine livers, thus contributing to the development of nitrite-free products. First, the effects of sodium disulfite, and acetic, ascorbic, and lactic acids on Zn-protoporphyrin formation and total microbial count were studied. The combination of ascorbic and acetic acid resulted in a higher Zn-protoporphyrin content than acetic acid alone and maintained microbial levels (ca. 3 log CFU/mL). Second, a response surface methodology was used to maximize Zn-protoporphyrin while maintaining microbiological food standards. The effects of pH (4.2–5.4), incubation time (3–30 h), and temperature (25–50 ºC) were studied. The selected conditions for Zn-protoporphyrin formation involved anaerobic incubation at pH 4.8 and 45 °C for 24 h. The safety was validated through challenge testing for relevant pathogens (Listeria monocytogenes, Salmonella spp., and Clostridium perfringens). A significant reduction (> 6 log units) was observed for L. monocytogenes and Salmonella, whereas C. perfringens spores remained at inoculated levels. The optimized procedure is proven to be microbiologically safe, and it is proposed to improve the color of nitrite-free meat products.