The Search for Natural Antimicrobial Compounds for Use in the Pork Industry

The pork industry is interested in using natural antimicrobials as alternatives to antibiotics. However, for this to be accomplished more of these compounds need to be identified and tested. Discovery of these antimicrobials involves extensive investigations of the relationships between the food matrix and the foodborne pathogens affiliated with it. One research area is the identification of natural antimicrobial compounds that arise from the feed or food source during processing. Other potential antimicrobial products are botanical compounds which have traditionally been used as flavor enhancers and/or preservatives.

Examples of ‘natural’ preservatives currently in use are nisin (a bacteriocin), monolaurin (an antiviral compound) and lactoperoxidase (an antimicrobial), but there are limitations to their use. These limitations may include development of resistant strains, reduced spectrum of activity, the cost of application, and the impact these compounds have on the organoleptic quality of foods and feed. To an extent, these limitations can be conquered by applying the hurdle effect (Ricke and Kundinger, 2004). The hurdle effect is using a combination of preservative factors (known as hurdles) that improve microbial stability as well as the organoleptic, nutritional, and economical properties of food. The antimicrobial activities of the three compounds above are greatly improved when used in combination with each other or with traditional treatments like hydrostatic pressure, low pH, freezing, etc. (Dufour et al., 2003).

Bacteriocins are currently the most widely used ‘natural’ preservatives in foods. They are antibacterial peptides produced from bacteria that kill or inhibit the growth of other closely related bacteria by a variety of mechanisms such as inhibition of cell wall synthesis, permeabilization of the target cell membrane, and/or by inhibiting RNase or DNase activity. These antimicrobial proteins are mainly produced from lactic acid bacteria (LAB) and target food pathogens without toxic or unpleasant effects on the product. With application of the hurdle effect, bacteriocins have the potential to utilize synergies of combined treatments to more effectively preserve foods and feed (Cleveland et al., 2001).

The most commonly used bacteriocin today is nisin. Discovered in 1928, nisin has been used as an antimicrobial food preservative for more than 50 years and is now approved for use in over 40 countries. However, it is only considered a ‘natural’ preservative when used in concentrations that do not exceed what is found in food naturally fermented with a nisin-producing starter culture (Cleveland et al., 2001).

Continued research and discovery of new natural antimicrobial compounds is of increasing importance to the producer because such compounds will be critical to meet increasing consumer demand for ‘healthier’ or ‘natural’ products.

References

Clevand, J., T. J. Montville, I. F. Nes, and M. L. Chikindas. 2001. Bacteriocins: safe, natural antimicrobials for food preservation. Int. J. Food Micro. 71:1-20.

Dufour, M., R. S. Simmonds, and P. J. Bremer. 2003. Development of a method to quantify in vitro the synergistic activity of “natural” antimicrobials. Int. J. Food Micro. 85:249-258.

Ricke, S. C., and M. M Kundinger. 2004. Alternatives to antibiotic use – natural food and feed amendments. J. Anim. Sci. 82 (Suppl. 1):19 (Abstr).

By Rachel Griffin and C. M. Wood, VA Tech
Livestock Update newsletter - Virginia Cooperative Extension