Investigating the Effects of Time and Temperature on the Growth of Escherichia coli O157:H7 and Listeria monocytogenes in Raw Cow’s Milk Based on Simulated Consumer Food Handling Practices

Abstract

Consumption of raw cow’s milk (RCM) is increasing in popularity in developed countries despite the associated foodborne disease risks. While previous research has focused on consumer motivations for drinking RCM, there is limited research on how consumer handling practices may impact the microbiological safety of RCM. In this study, consumer handling practices associated with transport, storage, and freezing and thawing were simulated to investigate the impact of time and temperature variables on the concentrations of either Escherichia coli O157:H7 or Listeria monocytogenes in RCM. We found that the type of storage during simulated transport had a large (η2 = 0.70) and significant (p < 0.001) effect on both pathogens. The refrigeration temperature also had a large (η2 = 0.43) and significant (p < 0.001) effect on both pathogens during refrigerated storage. The interaction between pathogen species and initial pathogen inoculum level had a large (η2 = 0.20) and significant (p = 0.012) effect on the concentration of the pathogens during ambient temperature storage. We found that freezing and thawing practices did not have a significant effect on the pathogens (p > 0.05). However, we were able to recover L. monocytogenes, but not E. coli O157:H7, from RCM after freezing for 365 days. The results from this study highlight that consumer transport and storage practices can have significant effects on the growth of E. coli O157:H7 and L. monocytogenes in RCM. Consumer food handling practices should be considered when developing public health strategies aimed at reducing the risks of RCM consumption.

Why knowledge is the best way to reduce the risks associated with raw milk and raw milk products

“…In order to reduce the risks associated with raw milk and its products, there are five highly effective guidance strategies for food services: (1) Never buy milk and its derivatives from clandestine sources; the latter are not inspected, and in addition to transmitting pathogens these products may be adulterated; (2) When buying raw milk from legally approved sources always boil the raw milk before use or consumption, once even inspected raw products can harbour pathogenic bacteria. (3) Fatty dairy products pose considerable risks: only use industrialised cream, whipped cream and butter; (4) Clean hands and surfaces that have come into contact with raw milk and its products to minimise cross-contamination: hands and surfaces should be cleaned with soap and water and then sanitised; (5) It is essential to strictly control the temperature regarding raw milk and its products; this practice is not only linked to spoilage bacteria, but it can also minimise the presence of pathogenic microorganisms (Leclair et al ., 2019). The temperature of transport and refrigeration should never exceed 4 °C.…”

“…Products should be sealed when stored, should not come into contact with other foods, and should be consumed as soon as possible. Freezing does not guarantee safety: some microorganisms such as L. monocytogenes can survive for more than 365 d in frozen raw milk (Leclair et al ., 2019). Figure 1 summarises the main strategies discussed above.…”

Comparative assessment of sanitary bacteriological indicators of cow's and goat milk

“…Це відбувається тому, що підвищення кількості соматичних клітин є наслідком запального процесу через присутність внутрішньовим'яної інфекції; також цей показник вважається чутливим маркером стану здоров'я вимені у кіз (Hunt et al, 2013;Sandrucci, Tamburini, Gislon, Bava,& Zucali, 2019;Souza et al, 2012). Нормальний рівень соматичних клітин у неінфікованому вимені кіз (~ 300 тис / мл), і овець (~ 200 тис / мл) істотно вищий ніж у молочних корів (~ 70 тис / мл), отже, цей показник в інфікованому вимені кіз і овець, як правило, значно вищий ніж у корів (Cak, Yilmaz, & Ocak, 2017;Leclair, McLean, Dunn, Meyer, & Palombo, 2019…”

Growth interferences between bacterial strains from raw cow's milk and their impact on growth of Listeria monocytogenes and Staphylococcus aureus

“…L. monocytogenes and Staphylococcus aureus are the major pathogens associated with consumption of raw milk and raw milk products and outbreaks occur regularly (Fusco et al 2020). L. monocytogenes is of particular importance in stored raw milk, since it is able to grow under refrigeration (Leclair et al 2019).…”

“…Listeria monocytogenes is of particular importance in stored raw milk, since it is able to grow under refrigeration (Leclair et al . 2019).…”