RISK PROFILE: LISTERIA MONOCYTOGENES IN LOW MOISTURE CHEESES Prepared as part of a New Zealand Food Safety Authority contract for scientific services by Dr Rob Lake Dr Andrew Hudson Peter Cressey Susan Gilbert July 2005 Institute of Environmental Science & Research Limited Christchurch Science Centre Location address: 27 Creyke Road, Ilam, Christchurch Postal address: P O Box 29 181, Christchurch, New Zealand Website: www.esr.cri.nz A CROWN RESEARCH INSTITUTE Client Report FW0440 RISK PROFILE: LISTERIA MONOCYTOGENES IN LOW MOISTURE CHEESES Dr Stephen On Food Safety Programme Leader Rob Lake Maurice Wilson Project Leader Peer Reviewer DISCLAIMER This report or document (“the Report”) is given by the Institute of Environmental Science and Research Limited (“ESR”) solely for the benefit of the New Zealand Food Safety Authority (“NZFSA”), Public Health Services Providers and other Third Party Beneficiaries as defined in the Contract between ESR and the NZFSA, and is strictly subject to the conditions laid out in that Contract. Neither ESR nor any of its employees makes any warranty, express or implied, or assumes any legal liability or responsibility for use of the Report or its contents by any other person or organisation. Risk Profile Listeria monocytogenes in July 2005 Low Moisture Cheeses ACKNOWLEDGEMENTS The authors would like to thank Maurice Wilson, ESR, Mount Albert Science Centre, for providing information for this Risk Profile. New Zealand Specialist Cheesemakers Association Inc. for providing the flowchart illustrating the cheesemaking process and for information. Risk Profile Listeria monocytogenes in July 2005 Low Moisture Cheeses CONTENTS SUMMARY .1 1 INTRODUCTION .3 2 HAZARD IDENTIFICATION: THE ORGANISM .6 2.1 Listeria monocytogenes .6 2.1.1 The organism/toxin .6 2.1.2 Growth and survival.6 2.1.3 Inactivation (Critical Control Points and Hurdles) .7 2.1.4 Sources.7 3 HAZARD IDENTIFICATION: THE FOOD .9 3.1 Relevant Characteristics of the Food: Low Moisture Cheese.9 3.1.1 Ingredients and processing.10 3.1.1.1 Milk.10 3.1.1.2 FSANZ approved raw milk methods, cheese treatment and pasteurisation .13 3.1.1.3 Acidification by starter cultures.15 3.1.1.4 Rennet .16 3.1.1.5 Curd processing .16 3.1.1.6 Salt .17 3.1.1.7 Ripening and Storage.17 3.1.1.8 Summary of controls in cheese making.18 3.1.2 Definition of low moisture cheeses.18 3.1.2.1 Red smear cheeses .20 3.1.2.2 Processed cheeses .20 3.2 Survival and Growth of L. monocytogenes in or on Low Moisture Cheeses .20 3.2.1 Semi-soft cheese .23 3.2.2 Hard cheese.24 3.2.3 Swiss cheeses (semi-soft and hard).25 3.2.4 Processed cheese.26 3.2.5 Conclusions.26 3.3 The Food Supply in New Zealand .27 3.3.1 Producti