The present invention relates to a method of reducing the concentration of Gram-negative bacteria in a food product, the method comprising adding a red wine extract produced from red wine by dealcoholization, concentration and drying, and a culture comprising at least one class IIa bacteriocin-producing lactic acid bacterial strain to a food product, ripening the food product, and storing the food product at a temperature of at the most 15° C. until a concentration less than 1 E-1 of Gram-negative bacteria. In a preferred embodiment of the invention, Gram-negative bacteria already present are eliminated. In one embodiment of the invention, the Gram-negative bacteria are Salmonella ssp. The bacteriocin-producing culture may comprise at least one of Lactobacillus curvatus (DSM 18775) and Pediococcus acidilactici (DSM 28307). The invention further relates to a kit for reducing the concentration of Gram-negative bacteria in a food product comprising a red wine extract produced from red wine by dealcoholization, concentration and drying, and a culture comprising at least one class IIa bacteriocin-producing lactic acid bacterial strain.