1. Manufacture low sodium string cheese by culture and direct acidification methods with different salt substitutes and flavor enhancers and determine flavor acceptability </P>
2. Determine the survival of pathogenic microorganisms in low sodium string cheese </P>
3. Determine the effect of added antimicrobials and bacteriocins on survival of pathogenic bacteria in cheese
Pressure has been put on the food industry to reduced sodium levels. Since reduction or elimination of salt from dairy products could potentially change the microbial stability an alternative antimicrobial agent may be needed. In addition to the use of antimicrobials salt replacers could be used to maintain acceptable flavor. To determine which antimicrobials have potential for success in reduced sodium dairy products, this study evaluated eight commercially available antimicrobials (lauric arginate, natural enzyme systems and various fermentates). Antimicrobials were also tested in combination with six commercial sodium reduction agents to determine if their use would interfere with antimicrobial activity. Sodium reduction agents contained one or more of the following components calcium salt, potassium salt, sodium chloride, cultured corn sugar and trehalose. Milk and low-sodium cheese agar systems were used as the growth medium for screening. Antimicrobials with and without sodium reduction agents were added to the agar systems, then a five-strain cocktail of Listeria monocytogenes, Salmonella or Escherichia coli O157:H7 was spread plated at three concentrations. Samples were then incubated at 30?C and observed for growth after 24 and 48h. A nisin-containing antimicrobial blend, lauric arginate, a natural enzyme system and a fermentate inhibited growth of all pathogens on milk agar after 48h. In the cheese agar, pathogen growth was observed after 48h with the nisin-containing antimicrobial blend, and the fermentate; while lauric arginate showed pathogen growth in 48h or less. No pathogen growth was observed in the cheese agar containing the enzyme system. </P>When the nisin-containing antimicrobial blend, lauric arginate and fermentate were tested in combination with sodium reduction agents containing potassium chloride, growth of Salmonella and E. coli O157:H7 was observed within 48h. Regardless of the salt substitute, there was no pathogen growth when the natural enzyme system was tested. Result from this study can aid in the selection of antimicrobials and sodium reduction agents for use in dairy products. However, testing in the dairy product itself is needed to confirm screen results and ensure a safe product.