Growth potential of Listeria monocytogenes in traditional Austrian cooked-cured meat products

Abstract European Union legislation limits for Listeria monocytogenes in ready-to-eat foods are based on whether or not foods favour the multiplication of this bacterium. The latter is defined by criteria for water activity ( a w ), pH and shelf-life. We studied a peculiar group of traditional Austrian meats implicated in foodborne listeriosis made from cured cooked comminuted meat with gelatin/aspic (Presswurst), blood (Blutwurst) or fat as a binder (Leberpate, Streichwurst, Zwiebelstreichwurst). Average pH values were 5.74 ± 0.45; 6.62 ± 0.31; 6.18 ± 0.36; 6.19 ± 0.15; 6.28 ± 0.04 for Presswurst ( n  = 15), Blutwurst ( n  = 15), Leberpate ( n  = 10), Streichwurst ( n  = 18) and Zwiebelstreichwurst ( n  = 3), respectively. Corresponding a w values were: 0.968 ± 0.004; 0.965 ± 0.004; 0.961 ± 0.005; 0.963 ± 0.003 and 0.957 ± 0.005. There were no statistically significant differences of pH among spreadable meat products. Presswurst had significantly lower pH values, but a significantly higher level of lactic acid bacteria. With the exception of one low pH Presswurst sample, all foods under study would favour the growth of L. monocytogenes. In a 9 days challenge test, Blutwurst showed a strong potential for supporting L. monocytogenes growth (2.4–4.6 log). In contrast, Presswurst was not able to support growth in all temperatures tested. A pH vs. a w chart was designed delineating the growth/no-growth border (defined as 0.43 log increase over 216 h) at 2, 4 and 8 °C. For a given sample (i.e. a pH/ a w data pair), it could be easily assessed if the product would likely be “safe” for 9 days at temperatures of a w chart for small businesses, the competent authority and for didactic purposes is discussed.