Antimicrobial effects among rosemary extract, cultured dextrose and buffered vinegar

Chemical preservatives in combination with various processing aids have been traditionally applied to food systems to prevent food spoilage microorganisms or foodbome pathogens. However, an increasing demand toward natural and additive-free food products from consumers prompted the food industry to seek effective "clean label" antimicrobial solutions which maintain safety and stability of the food products.

Cultured dextrose is a commercially available food additive produced by fermentation of sugar sources such as com, cane sugar, or dairy based sources including skim milk. The cultured dextrose is composed of various fermentation metabolites where the main active components are antimicrobial peptides and organic acids. The microorganisms involved in the fermentation are mainly probiotic bacteria, such as propionic acid (including Propionibacterium freudenreichii) and lactic acid bacteria (including Lactococcus lactis). The main application of cultured dextrose is to inhibit the growth of bacteria, yeast, and mold in food systems.

Cultured dextrose could be an effective preservative in various applications including dairy, baked goods, or culinary products. However, the product often imparts savory notes to the product when used in effective dosages.

The increased evidences that plant materials have a potential for antimicrobial activity led researchers to study different extracts to inhibit bacteria, yeasts, and molds in various applications. Plant secondary metabolites are natural compounds that are known for their plant defense mechanisms and possess multiple biological activities including antimicrobial effects. They include alkaloids, flavonoids, tannins, terpenes, quinones, and resins. One of the major limitations for using plant extracts as an antimicrobial agent in the food and feed industry is that the plant extracts often require high effective dosage and thus negatively impacts the organoleptic property of the applied matrices.

Essential oils are mixture of volatile compounds extracted from plant biomass and have been identified as natural antimicrobial agents where the activity is mainly understood to arise from phenolic components. However, the usage of essential oils as a food preservative is limited due to the high flavor profile, which flavor profile negatively impacts the organoleptic property of the applied food.

Buffered vinegar is another "clean label" alternative for chemical preservatives in the current food industry, especially for meat and poultry. Buffered vinegar is known to inhibit the growth of foodborne pathogens as well as common spoilage organisms. The taste impact of vinegar may be reduced by buffering the vinegar with sodium or potassium based alkalis. However, the concentration of buffered vinegar required to exhibit antimicrobial activity often imparts "vinegar'* or "acidic" notes in the final products and negatively impacts the organoleptic property.

The combinations of these ingredients which could effectively suppress the growth of spoilage microorganisms or pathogens at lower concentrations and thereby diminish the associated flavor impact of the constituent antimicrobials. These synergistic combinations find application in meat and poultry, sauces and dressings, salads, hummus, seafood, cosmetics and / or nutritional supplements.

The combinations relates to antimicrobial processes and to novel antimicrobial compositions which may be employed in such processes. In search of a novel and powerful "clean-label" antimicrobial solution, three distinct dasses of antimicrobials including plant extrads (such as plant essential oils), cultured dextrose, and buffered vinegar were tested for synergistic antimicrobial effects. Surprising synergies were observed when rosemary extract or rosemary essential oil, cultured dextrose, and buffered vinegar were combined. Combinations of two and/or three of these antimicrobials all showed synergistic antimicrobial effect against Salmonella entericia subsp. enterica serovar Typhimurium.