Effect of Cell-Free Supernatant from Lacticaseibacillus paracasei on the Nutritional, Oxidative, and Microbiological Quality of Sous-vide Cooked Red Deer Meat

Game meat, including red deer ( Cervus elaphus ), is valued for its high protein content and favorable lipid composition but remains highly susceptible to oxidative deterioration, which limits its technological stability during processing and storage. Natural clean-label strategies are therefore needed to improve the quality and shelf life of game meat products. This study investigated the effect of a cell-free supernatant (CFS) produced by Lacticaseibacillus paracasei B1 as a natural marinade on the physicochemical, oxidative, microbiological, and nutritional quality of sous-vide cooked venison. Red deer steaks were marinated in a 1% CFS solution for 24 h at 4 °C or left untreated (control), vacuum-packed, and cooked sous-vide at 60 °C for 6 or 8 h. Analyses were performed immediately after processing and after 30 days of refrigerated storage at 4 °C. CFS marination significantly decreased pH (6.13 vs. 6.01) and oxidation–reduction potential (337.6 vs. 322.0 mV), creating a more reducing environment in the meat. Marinated samples also exhibited higher antioxidant activity, reflected by increased ABTS•⁺ radical scavenging activity (64.83% vs. 57.82%) and metal-chelating capacity (55.66% vs. 45.16%). In addition, CFS improved the nutritional lipid profile by reducing saturated fatty acid content (0.479 vs. 0.683 g/100 g) and the thrombogenic index (0.97 vs. 1.20). Refrigerated storage increased protein oxidation, as indicated by higher carbonyl content (40.29 to 71.10 nmol/mg protein), while CFS treatment attenuated oxidative deterioration during the early stages of storage. Storage also altered the free amino acid profile of the meat. The results indicate that L. paracasei B1 CFS is a promising clean-label marinating agent that enhances the oxidative stability and selected nutritional quality characteristics of sous-vide venison. Its application may contribute to the development of high-quality game meat products with improved technological stability and extended refrigerated shelf life.