Effect of Antimicrobials and Sodium Replacement Agents on the Survival of Pathogenic Bacteria in Low Sodium Low-Moisture Part-Skim (LMPS) Mozzarella Cheese

Author

Tiffany M J Taylor, California Polytechnic State University, San Luis ObispoFollow

DOI: https://doi.org/10.15368/theses.2013.187
Available at: https://digitalcommons.calpoly.edu/theses/1102

Date of Award

12-2013

Degree Name

MS in Agriculture - Food Science and Nutrition

Department/Program

Food Science and Nutrition

Advisor

Amanda Lathrop

Abstract

Recent increases in chronic cardiovascular diseases, such as hypertension, have put pressure on the food industry to reduce sodium levels. Dairy products, though full of vital nutrients, are perceived as being high in sodium. However, the reduction of salt in dairy products could potentially alter the microbial stability, as well as cause unfavorable changes in flavor. In order to reduce the sodium level, while maintaining acceptable flavor and microbial stability, salt replacers and alternative antimicrobial agents may need to be introduced into the food matrix. To identify potential antimicrobials for use in reduced sodium dairy products, this study evaluated the efficacy of eight commercially available antimicrobials in TSA, milk agar, and cheese agar. Antimicrobials included MicroGard 100, MicroGard 430, Nisaplin, NovaGard CB1, Protect-M, PuraQ Verdad RV75, SEA-i F75 and VMY1P. Antimicrobials were also tested in combination with six commercial sodium reduction agents (potassium chloride, Puracal PP/USP, Purasal Hi Pure P Plus, PuraQ Verdad NV10, SaltWise 0029 and SaltWise 1029) to if there were any interference with antimicrobial activity.

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: 10¹, 10² and 10⁴ CFU/plate. Samples were then incubated at 35°C and observed for growth after 24 and 48h. SEA-i F75 was the most effective antimicrobial in each of the agars tested. Additionally, no interactions were observed between SEA-i F75 and any of the sodium replacement agents.

SEA-i F75 was selected for use in a final challenge study using six formulations of LMPS mozzarella cheese: regular sodium control cheese (1.7% NaCl, no antimicrobial added); low sodium control cheese (0.7% NaCl, no antimicrobial added); low sodium treated cheese (0.7% NaCl, treatment with SEA-i F75); low sodium cheese with KCl as salt replacer (0.7% NaCl, 1.0% KCl, treatment with SEA-i F75); low sodium cheese with Alta 2345 as salt replacer (0.7% NaCl, 0.25% Alta 2345, treatment with SEA-i F75); and low sodium cheese with Salona as salt replacer (0.7% NaCl, 0.95% Salona, treatment with SEA-i F75).

Fifteen gram cheese pieces from each formulation were dipped in an antimicrobial solution containing 0.25% SEA-i F75 then inoculated with L. monocytogenes, Salmonella, or E. coli O157:H7 at a target inoculum concentration of 10²-10³ CFU/g and incubated at either 4° or 12°C. In all trials, over all formulations and temperatures tested, initial decreases in counts, followed by organism recovery were observed. Therefore, SEA-i F75 was not effective at reducing the counts of pathogenic bacteria in LMPS mozzarella cheese.

Results from this study highlight the effect of the food matrix, and its components on antimicrobial efficacy. Future research includes examining the effect of one of the other antimicrobials in LMPS mozzarella cheese.