Antilisterial Activity of Whey, Derived from Raw Regular and Ultrafiltered Milk Cheese

Abstract

Cheese is generally recognized as a safe and nutritious food. However, Listeria monocytogenes is a foodborne pathogen that has caused serious illness linked to cheese consumption. Cross contamination of ready-to-eat food is a significant concern in the spread of Listeria. It is crucial for cheese manufacturers to take precautions to prevent contamination with this harmful pathogen. Whey is the liquid by-product of cheese-making and is one of the main proteins in milk. Whey is strained and discarded during the cheese-making process, but a useful and beneficial application of cheese whey coming from its protein composition is hypothesized to inhibit bacterial growth. This research was designed to study the antilisterial activity of cheese whey strained from cheese made with raw regular compared to ultrafiltered (UF) milk. Regular and UF whey were filtered to eliminate cheese particles and background microbiota. All samples were inoculated with a combination of three strains of Listeria. We speculated that normal growth of Listeria would occur following multiple serial dilutions, inoculation, and incubation. However, data showed enhanced antilisterial activity of regular cheese whey stored at room temperature compared to ultrafiltered cheese whey. We speculate that a protein of a particular molecular weight (in kDa), or an enzyme of low abundance in cheese whey may have notable antilisterial activity. We also found that lactic acid content does not contribute to enhanced antilisterial activity.