Recently, the FDA reported several cases of Listeria contamination in RTE meat products. There are some natural preservative ingredients that can be used in the meat processing to prevent microbial contamination. For the preservative solution of RTE meat products, nisin, vinegar powder and cultured dextrose(fermented sugar) can be considered. The following is a detailed introduction to these ingredients:

Nisin:

• Nisin is an antimicrobial peptide that is active against Gram-positive bacteria (such as Listeria monocytogenes on the surface of meat). Nisin is a polycyclic antimicrobial peptide produced by Lactococcus lactis and is commonly used as a food preservative. It is mainly used in meat and cheese to control the growth of Gram-positive spoilage bacteria and pathogens.

• Nisin destroys the cell membrane by forming pores in the cell wall, causing cell death.

• Nisin can be used in a variety of liquid or solid foods, canned or packaged, and can be stored at ambient or refrigerated temperatures.

• Nisin is primarily used in heat-processed foods to prevent spoilage caused by spore-forming bacteria and can also be used to control spoilage caused by heat-sensitive lactic acid bacteria and B. thermosphacta.

• Nisin can also be used as part of a safety measure to control pathogens such as Bacillus cereus, Listeria monocytogenes, and Clostridium botulinum.

• Nisin can be combined with organic acids, chelating agents, vacuum packaging, or modified atmosphere packaging to enhance its antimicrobial activity.

Applications of Nisin in Meat Products:

• Nisin has been tested in a variety of meat products, including raw, cooked, and fermented meat products.

• Nisin can be added to meat slurries or applied to surfaces before packaging.

• Nisin can be added directly to meat because it is heat-stable.

• Adding nisin to bologna sausage inhibits the growth of spoilage lactic acid bacteria.

• In ham and bologna, nisin showed increased effectiveness against a wide range of bacteria (e.g., heat-killed Bacillus, Lactobacillus curvatus, Leuconostoc mesenteroides, Listeria monocytogenes, Salmonella, and E. coli O157:H7) when used in combination with lysozyme and EDTA.

• In homemade-style pasteurized refrigerated gravies and sauces, nisin inhibited the growth of psychrophilic Bacillus cereus.

• A combination of nisin and citrate has been shown to effectively control C. perfringens in Italian wurstel sausages.

• In meat systems, nisin has a more promising application in sausages and pâtés, as homogenization of the meat allows nisin to be more easily distributed.

• Nisin can be used to prevent the growth of C. perfringens spores in natural sausage casings.

• Nisin can also be used in active packaging to extend the shelf life of meat products. For example, nisin is incorporated into plastics to inhibit bacterial growth on the surface of meat.

• Nisin combined with high hydrostatic pressure (HHP) can extend the shelf life of mechanically recovered poultry meat.

• Nisin is typically applied to food at concentrations of 1-25 ppm. It inhibits the growth of a wide range of Gram-positive bacteria, including Listeria monocytogenes.

• The mechanism of action of nisin is disruption of the microbial cell membrane, resulting in leakage of cellular components.

• Nisin can be combined with other antimicrobial agents to enhance its effectiveness. For example, it can be combined with lactate, acetate, ethylenediaminetetraacetic acid (EDTA), or lysozyme. Combining with EDTA can increase its effectiveness against Gram-negative bacteria.

• Studies have shown that nisin can effectively extend the shelf life of meat products. For example, in chicken packaged in modified atmosphere (MAP), nisin combined with EDTA can effectively reduce bacterial counts and extend shelf life. In ready-to-eat meat products such as ham and bologna, nisin has also been shown to inhibit the growth of Listeria monocytogenes.

Vinegar Powder:

• Vinegar powder is a dehydrated form of vinegar that can be used as a preservative in foods. Vinegar powder acts as a natural preservative that inhibits bacterial growth. The acidic components in vinegar powder help lower the pH of foods, which inhibits the growth of microorganisms.

• Vinegar, especially acetic acid, is often used in marinating meats to improve flavor, extend shelf life, and mask off-flavors.

• Acetates can be combined with other antimicrobials such as nisin to enhance their effectiveness.

• Vinegar powder has similar properties to vinegar in terms of food preservation and can inhibit the growth of certain bacteria.

• For example, the use of vinegar powder in boneless ham and deli-style turkey breasts can delay the growth of Listeria monocytogenes even better than vinegar alone.

Cultured Dextrose:

• Cultured sugar/vinegar mixtures are produced by fermentation of certain cultures, resulting in a complex product containing sugars, organic acids, peptides and aromatics. Cultured dextrose is a natural preservative produced by microbial fermentation.

• In marinades, cultured dextrose can be used as a substitute for lactic acid and/or salt to enhance food safety and quality.

• 3% cultured dextrose has been found to inhibit the growth of Campylobacter and Salmonella typhimurium in cooked chicken breasts.

• In frozen and RTE chicken breasts, the use of cultured dextrose can improve texture, suggesting that this ingredient can be used to improve the safety and quality of processed poultry products.

Other relevant information

• Combination use: To overcome the limitations of a single preservative, two or more biological preservatives can be used in combination, or preservatives can be used in combination with other preservation technologies.

• Natural sources: To meet consumer demand for natural ingredients, preservatives from natural sources, such as antimicrobials from plants, can be used.

• Modified atmosphere packaging (MAP): Modified atmosphere packaging can extend the shelf life of meat products by changing the gas composition within the package. Modified atmosphere packaging with high carbon dioxide concentrations, combined with nisin, has been shown to effectively inhibit the growth of Listeria monocytogenes.

• Active packaging: Active packaging systems can release antimicrobial or antioxidant compounds to extend the shelf life of foods. For example, antimicrobials such as nisin can be added to edible films for the packaging of meat products.

Nisin, vinegar powder, and cultured dextrose are all potential natural preservatives that can be used to improve the safety and shelf life of ready-to-eat meat products. By rationally combining these preservatives and combining them with other preservation technologies, microbial growth can be effectively controlled and consumer demand for natural, safe foods can be met.