Called competitive inhibition, this biocontrol approach uses non-pathogenic microorganisms to prevent the growth of pathogens in targeted substances. For example, LAB cultures may be applied to MPR fruits and vegetables (e.g., already peeled, and possibly sliced, grated, or shredded) to inhibit the growth of pathogens that may be present, including Salmonella, Shigella, Escherichia coli O157:H7, Staphylococcus aureus, and others.
"Whether these pathogens grow and cause disease depends on the type of product, conditions of storage (time, temperature, atmosphere, etc.), and competing microflora," wrote Fred Breidt, Ph.D., and Henry P. Fleming, Ph.D., the article's authors. "Altering the normal microbial ecology of these products through cutting, processing, modified-atmosphere packaging, and refrigerated storage may have the unintended effect of allowing the growth of pathogenic bacteria [without biocontrol]."
Naturally found in fermented foods such as pickles and sauerkraut, lactic acid bacteria can prevent the growth of pathogens and spoilage organisms in minimally processed produce and other non-fermented foods. In fermented foods, these cultures are being studied for ways to manipulate the fermentation process to enhance flavor and shelf life.
LAB, such as the Lactobacillus species found in yogurt, are generally much more resistant to acid than other bacteria, thus can survive in environments that are lethal to most pathogens. Moreover, they can produce a variety of metabolites [substances produced by or taking part in metabolism], including lactic and acetic acids which increase acidity in foods, inhibiting the growth of other microorganisms.