CIEH SE Region Training Event Pasteurisation and Cheese HACCP. HACCP for cheesemaking

Transcription

1 CIEH SE Region Training Event Pasteurisation and Cheese HACCP HACCP for cheesemaking Paul Neaves Williams & Neaves The food microbiologists

2 HACCP PRINCIPLES FOR PASTEURISED AND UNPASTEURISED MILK CHEESES Introduction Milk pasteurisation became widespread to prevent the spread of infectious diseases such as bovine tuberculosis and brucellosis The process is employed widely by the dairy industry as a CCP but pasteurisation is thought by some to affect adversely the organoleptic qualities of cheese 2

3 HACCP PRINCIPLES FOR PASTEURISED AND UNPASTEURISED MILK CHEESES However, today s consumer demands new and exciting foods that are perceived to be: - natural - wholesome - unprocessed - organic Therefore conflict exists between market development and today s quest for absolute food safety 3 Microbiological risk assessment is a crucial part of the system.

4 HOW DO WE INTERPRET THE FOOD POISONING STATISTICS? In , general outbreaks of food poisoning in England & Wales were attributed as follows:- Milk & cheese 3.5% of which: cheese 1.6% unpasteurised milk 0.8% pasteurised/recontam. milk 1.1% 4 What an excellent track record the UK dairy industry has!

5 WHY WE MAKE CHEESE 5

6 COMPOSITION OF MILK Milk Cow Goat Ewe Buffalo Fat % Protein % Lactose % Minerals/ vitamins % Water %

7 COMPOSITION OF CHEESE Cheese Parmesan Cheddar Edam Brie Fat % Protein % Lactose % <0.1 <0.1 Water %

8 8 STEPS IN CHEESEMAKING Milk supply & delivery Milk pasteurisation Starter culture propagation Curd production Salting dry salt or brine Maturation Distribution/retail/the consumer

9 The UK raw milk supply is the best in the world Brian Peacock, Chairman, UK Dairy Association ca

10 Everybody knows that the microbiological quality of raw milk is horrendous A food technologist, who shall be nameless, ca

11 THE UK RAW MILK SUPPLY IS THE BEST IN THE WORLD In 1982, the UK pioneered the concept of a farmer quality payment scheme based upon TBC (total bacterial count) Today, many countries operate similar schemes using either TBC or Bactoscan 11

12 THE UK RAW MILK SUPPLY IS THE BEST IN THE WORLD EU and UK legislation operate to a benchmark TBC of 100,000 cfu/ml In the UK, ex-farm TBCs of <1000 cfu/ml are not uncommon Bactoscan = 5-8 x TBC 12

13 PATHOGENS AND RAW MILK CHEESEMAKING Raw milk will inevitably sometimes contain pathogens but their presence in the final product can be minimised by good agricultural and hygienic practices, and appropriate CCPs. In cheesemaking, traditionally, the Big 4 are:- Salmonella Listeria monocytogenes Staph. aureus E. coli ( conventional ) 13

14 PATHOGENS AND RAW MILK CHEESEMAKING But, currently, our main concerns include:- - E. coli O157 (and related strains) - Mycobacterium bovis (re-emergence) Hygienic control of unpasteurised milk cheeses involves a 'farm to fork' approach. No CCP is 'absolute'; final product safety is a team effort by a series of control measures working together. 14

15 15 PATHOGENS IN RAW MILK How does the microbiological quality of UK raw milk compare with that of other countries? PHLS survey of UK raw milk ( ):- - Campylobacter jejuni 1.7% of samples - Salmonella 0.5% of samples - E. coli O % of samples Survey of US raw milk (2001):- - Campylobacter jejuni 9.2% of samples - Shiga-toxin producing E. coli 3.8% of samples - Listeria monocytogenes 4.6% of samples - Salmonella 6.1% of samples - Yersinia enterocolitica (virulent) 6.1% of samples

16 LISTERIA IN RAW MILK Dairy industry survey of UK raw milk:- - Salmonella 0.36% of samples - Listeria monocytogenes 5.08% of samples Listeria contamination is seasonal:- - January % - August % - January % 60% of positives <10 cfu/ml; highest count 62 cfu/ml O Donnell, ET (1995) J. Soc. Dairy Tech.,

17 THE SPECIALIST CHEESEMAKERS OWN DATA Specialist cheesemakers in the UK submitted to the SCA Technical Committee the results of routine pathogen tests made on their raw milk supplies, January 2011 August

18 THE SPECIALIST CHEESEMAKERS OWN DATA Organism No. tests Detected /25ml <20/ml Highest count No. % No. % cfu/ml L. monocytogenes / <20 Listeria spp. (other than Lm) Salmonella enterica E. coli O n/a n/a n/a 0.0 (<0.3%) 0.0 (<0.4%) n/a n/a n/a n/a n/a n/a Organism Coagulase-positive staphs. No. tests <20/ml 100/ml 1000/ml Highest count No. % No. % No. % cfu/ml x10 3 E. coli (conventional) x0 3 Coliforms x10 5 Enterobacteriaceae x

19 OTHER SANITARY STATISTICS Faecal contamination of raw milk (Denmark):- Poor hygiene: Good hygiene: Maximum hygiene: 2.0g faeces / 20 Kg milk 0.2g faeces / 20 Kg milk 0.04g faeces / 20 Kg milk Source: British Mastitis Conference - 9/10/02 19

20 MILK PROCUREMENT Cheesemakers who use unpasteurised milk must have a detailed knowledge of their major raw material Knowledge of production conditions is enhanced by a close relationship with the milk producer(s) 20

21 MILK PROCUREMENT 21 Health of the milking herd - gastrointestinal disease - mastitis Closed herd policy - bovine tuberculosis Farmer Quality Payment Scheme - Bactoscan/TBC - Pathogen monitoring

22 OTF STATUS Milk for raw milk cheesemaking MUST be produced by herds that have Official Tuberculosis Free (OTF) status and have not been served with a Heat Treatment Order. These herds are tested more frequently than usual, mostly annually, and the milk producer should hold a valid certificate indicating the date and result of the last test. 22

23 FARM HYGIENE & MANAGEMENT For unpasteurised milk cheeses, milk production hygiene must be tightly controlled:- Cleaning and sterilisation of milking equipment (obvious) Should teats be washed and dried before attaching the milking cluster? Dry teats using a separate disposable towel for each cow Indoors or outdoors housing? Should sand replace straw for bedding? Russian starlings in open-sided cattle sheds (How) can we make this a CCP? 23

24 MILK PROCUREMENT Various options exist for procuring a milk supply:- LOW RISK HIGH RISK own herd vertically-integrated co-operative where milk producers own the dairy independent milk producers under direct contract to the dairy 'open market' milk supplied by a primary purchaser / haulier Of these, a cheesemaker's own herd is likely to provide the least risk of pathogen contamination and 'open market' milk the greatest. Current trend for UK farmhouse cheesemakers is to buy milk from a primary purchaser who may be unwilling to disclose the identity of the milk producer(s) 24

25 25 MILK PROCUREMENT Dairies in other European countries are often vertically-integrated co-operatives in which the cheesemakers:- - own their own tankers - collect milk themselves - monitor farm hygiene by testing individual milk supplies for specific pathogens - may pay farmers according to the incidence of pathogens: e.g. monthly tests for:- - Salmonella - Listeria - Staph. aureus - E. coli - STEC

26 RAW MILK TRANSPORT Because most UK milk is pasteurised, little attention has been given to the consequences of contaminating a milk tanker with pathogenic micro-organisms How many deliveries has the tanker made before my delivery? When was the tanker last CIP cleaned? Farmhouse cheesemakers sometimes use the tanker hose to fill the cheese vat directly:- - Where s the hose been? - How do you stop it from falling into the vat of milk? - How do you clean it? (How) can we make this a CCP? 26

27 MILK DELIVERY Direct pipeline ideal? Mobile tank owned by the farmer 27 - how to clean? Contract haulier - car wash (external) before off-loading (France) - first delivery after tanker cleaning (internal) (UK) Milk into vat (no holding tank) - the tanker hose (where s it been?) - the dairy s hose (how to clean it)

28 CAN THE RAW MILK SUPPLY BE A CCP? 28

29 CHEESES AND CHEESEMAKING PRACTICE Cheese is not a single commodity. Different varieties have widely varying compositional and technological variations. A CCP that works for one cheese may not work for another. 29

30 THE CHEESE SAFETY WEDGE Some cheese varieties are more robust than others:- 30

31 DIFFERENT TYPES OF CHEESE Caerphilly - Can be sold within a week of production, or - Can be matured for up to 6 months Cheddar - Mild Cheddar is matured for just a few weeks - Mature Cheddar may be stored for 18 months or more Mould-ripened cheeses - Are inevitably matured for several weeks / months - But they have a higher moisture content than hard cheeses and the ph value rises due to the mould growth and permits the growth of Listeria monocytogenes Therefore many factors operate in concert 31

32 UNPASTEURISED MILK CHEESES Parmesan is considered to be made from raw milk:- - but the curd is heated to 55 C for at least 45 min. (plus heating & cooling) - a heat process that is roughly equivalent to pasteurisation However, whether or not the milk is pasteurised, curd handling often involves the use of equipment that is not easy to clean, with manual handling and exposed product Thus the potential for in-process contamination is equally great 32

33 CHEESES AND CHEESEMAKING PRACTICE The control of curd production and maturation plays an essential part in determining the growth, survival or death of bacterial pathogens In order for a CCP to be effective, the hazard must be defined very precisely. 33 You cannot say, I have something measureable that I want to use as a CCP. Now what hazard can I use it for?

34 CHEESE AND CHEESEMAKING PRACTICE Factors that may affect the fate of bacterial pathogens:- A) during curd production - rate of acid development (a few hours or overnight) - titratable acidity (or ph) of the fresh curd (ph ) - salt-in-moisture content (0-10%) and time of salt addition (DOP or DOP+1) B) during maturation (and shelf life) - ph changes due to mould ripening (ph ) - maturation time (0-18 months or more) - maturation temperature (4-16 C) - maturation humidity (85%) Different pathogens react in different ways to the same set of conditions 34

35 COAGULATION OF THE MILK SOLIDS May or may not involve:- Starter cultures (lactic acid bacteria, LAB), that convert lactose into lactic acid which reduces the ph value. Acidification may be fast or slow. May or may not involve:- Rennet, an enzyme that acts on the casein element of milk protein, causing it to coagulate, trapping water and fat. 35

36 COAGULATION OF THE MILK SOLIDS Options to clot the milk solids:- Fast acidification (ph <5.5) by microbes, and enzyme action - English hard cheese Slow acidification (ph <5.0) by microbes, and enzyme action - Blue and white mould-ripened cheese Slow acidification (ph <4.7) by microbes, no enzyme action - Cream cheese, goats log Acidification, and heating above 87 C - Ricotta, mascarpone Other options exist! 36

37 CURD PRODUCTION Starter cultures acidify curd either quickly or slowly:- Hard cheese 3 to 6 hours - slow vat if curd fails to achieve: - ph 5.5 or lactic acid 0.4% - after 6 hours (possible CCP) Soft/semi-soft cheese 10 to 18 hours - poor starter activity if curd fails to achieve: - ph 5.0 or lactic acid 0.7% - the next day (not a CCP?) 37 The HARA team of a major supermarket thinks that failure to achieve ph 5.0 within 8 hours makes cheese lethal!

38 ACIDIFICATION WITHOUT ENZYME ACTION To make lactic curd:- Lactic acid bacteria convert lactose into lactic acid ph value decreases to a point (the isoelectric point, ph 4.7) where casein comes out of solution Curds are formed after prolonged incubation (e.g. 30 C / 24 h) 38

39 DRAINING LACTIC CURD 39

40 A SLOW VAT Originated for Cheddar cheese production:- A slow vat occurs when the curd fails to achieve 0.4% lactic acid within 6 hours of rennet addition, i.e. rennet to mill time. These criteria:- - were designed to control growth of staphylococci - can be used in HACCP as a CCP 40

41 SOFT CHEESE? For soft cheese, the acidification rate for a NORMAL make is too slow to control pathogens. Almost all soft cheeses are made as slow vats! Therefore:- - cannot be used as a CCP to control growth of pathogens during curd production. - Brie de Meaux may contain E. coli at up to 10 5 cfu/g For most soft cheese, there is no CCP at this stage, hence their position towards the thin end of the Cheese Safety Wedge. 41

42 40 Temperature profile for Brie cheese production 30 Temperature ( C) Time (days) 42

43 Log cfu/ml (g) Predicted growth of E. coli O157 during Brie cheese production Time (days) 43

44 SLOW ACIDIFICATION AND QUALITY For soft cheese, rate of acidification can be used as a quality parameter to monitor day-to-day consistency of production. Just don t write it into HACCP! 44

45 STARTER CULTURE PROPAGATION Starter cultures are obtained either from a proprietary source or are mothered (propagated) at the dairy. This is done by inoculating a culture into sterilised milk (usually a churn-full that has been heat-treated at 90 C/30 min. then cooled) and incubating overnight to produce bulk starter. 45

46 STARTER CULTURE PROPAGATION Direct vat inoculation (DVI/DVS) Low In-house propagation ( mother cultures ) - linear - circular Back-slopping (OK for Parmesan) High 46 IS THIS A CCP?

47 STARTER CULTURE PROPAGATION 47

48 ph VALUE OR TITATABLE ACIDITY? ph value determines the fate of microbes T/A tells you about cheese quality: The two are related but not quantitatively 48 ph probes are usually made of GLASS DO NOT PUT IT IN THE VAT OR THE CURD! ph meters are laboratory instruments and should be calibrated at the start of each day of production ph probes should be cleaned regularly to remove fat and protein deposits

49 MEASURING TITRATABLE ACIDITY 49

50 ph CHANGE DURING CURD FORMATION 50

51 T/A CHANGE DURING CURD FORMATION 51

52 TESTING THE CURD 52

53 CUTTING THE CURD 53

54 CUTTING THE CURD 54

55 STIRRING THE CURDS AND WHEY 55

56 FILLING CAMEMBERT MOULDS 56

57 PEG MILL FOR HARD CHEESE 57

58 SALTING CURD FOR HARD CHEESE 58

59 COOLEA CHEESE (GOUDA STYLE) 59

60 SALTING DRY SALT v BRINE Dry salting - often on day of curd production Low Brining 60 - usually next day - brine may be 20 weeks or 20 years old! - requires maintenance sieve / add salt - requires testing for E. coli / Listeria High

61 BRINING CHEESE Cheesemakers often make a brine that contains 20%w/w salt How to monitor brine strength and how often: Hydrometer Refractometer Does an egg float? (or a potato if you re in Ireland) Is ph important? Does ph need to be monitored? Immerse cheese for around 10 hours/kg 61

62 DRY SALTING 62

63 HOW DO WE MEASURE BRINE STRENGTH? There are a number of different scales for measuring brine strength. In the UK, % saturation and % NaCl are most commonly used. BRINE STRENGTH (at 15.5 C) GRAMS/LITRE Salometer degrees Saturation (%) NaCl (% w/w) Baumé degrees Specific gravity NaCl Water What does a 20% brine mean?

64 BRINING GOUDA AND CAMEMBERT 64

65 BRINE TANK! 65

66 MATURATION Need to control: - time / temperature / humidity - better to be consistent than accurate (is calibration necessary?) Listeria is only a hygiene problem: - controllable! Wooden shelving is OK for hard cheese but not for soft: - must be properly maintained clean / dry / no damage - allows cheese to breathe Salmonella / E. coli: - can grow in soft cheese - die in hard cheese (>60 days) 66

67 A DISUSED RAILWAY TUNNEL! 67

68 IDEAL CONDITIONS FOR MATURATION 68

69 MATURING HARD CHEESE 69

70 TYPICAL PROCESS PARAMETERS HARD CHEESE Parameter Milk In Into Next Maturation intake vat mould day Start End Temperature ( C) Aqueous salt (%) ph value Time 0h 0.5h 5h 20h 24h 6-24m 70

71 TYPICAL PROCESS PARAMETERS MOULD-RIPENED, SOFT CHEESE Parameter Milk In Into Next Maturation intake vat mould day Start End Temperature ( C) Aqueous salt (%) ph value Time 0h 0.5h 2.5h 20h 24h 21-28d 71

72 FATE OF PATHOGENS - HARD, ENGLISH CHEESES Milk In Into Next Maturation intake vat mould day C ph Salt E. coli 72 Staph. aureus (hours) TIME (months)

73 FATE OF PATHOGENS - MOULD-RIPENED, SOFT CHEESES Milk In Into Next Maturation intake vat mould day C ph Salt E. coli 73 Staph. aureus (hours) TIME (weeks)

74 COMPETITION BETWEEN MICROBES Competition:- occurs between different species of Gram-negative bacteria (Enterobacteriaceae) and growth of the weaker organism is suppressed (The Jameson Effect). Can high coliforms in cheese suppress E. coli O157 and contribute to the product safety? 74

75 COMPETITION BETWEEN MICROBES Pathogens may be poor competitors but the effect is difficult to quantify Limitation of Combase:- Prediction: Listeria grows by 1 log/17.5 days on Caerphilly cheese. Listeria DOES NOT grow on Caerphilly cheese 75

76 THE LIMITATIONS OF MATHEMATICAL MODELLING TYPE OF CHEESE SALT IN PRODUCT MOISTURE SALT IN MOISTURE ph VALUE FATE OF 20 C RISK RECOMMENDED MAX. TEMPERATURE (%) (%) (%) Pathogen Mature Cheddar Mature Brie Combase prediction* Staph. 3 log growth/37 h low Salmonella 3 log growth/>43 h** low Listeria 3 log growth/60 h low E. coli 3 log growth/74 h low Staph. 3 log growth/22 h high Salmonella 3 log growth/26 h high Listeria 3 log growth/27 h high E. coli 3 log growth/32 h high (<8 C; ambient) Ambient * NOTE 1: Combase does not take into account the significant element of inhibition brought about by microbial competition and therefore, for fermented foods, its predictions are excessively pessimistic. ** NOTE 2: The Combase equation for Salmonella does not allow the use of salt in moisture values >4.6%. <8 C 76

77 FATE OF MYCOBACTERIUM BOVIS IN CAERPHILLY CHEESE 77 Michael Rowe, Richard Forgrave, Queens University Belfast, Campden BRI presentation 8 March 2011

78 FATE OF MYCOBACTERIUM BOVIS IN CHEDDAR CHEESE 78 Michael Rowe, Richard Forgrave, Queens University Belfast, Campden BRI presentation 8 March 2011

79 DISTRIBUTION, RETAIL & THE CONSUMER Temperature control: - important for soft cheese - less important for hard cheese Where does maturation end and shelf life begin? C <8 C (<5 C) 79

80 CASE STUDY: Staph. aureus in a semi-soft, raw milk, washed-rind cheese From time to time, incidents occur concerning Staph. aureus in cheese made from raw milk. Milk supplied by a local farmer with direct delivery using a mobile tank. Staph. aureus in cheese: 10, ,000/g 80

81 Staph. aureus in a semi-soft, raw milk, washed-rind cheese Somatic cell counts:- 1 cow: >4,000,000 cells/ml 3 cows: >1,000,000 cells/ml 118 cows: around 250,000 cells/ml 81 Staph. aureus:- MILK- from tank delivered: 9,200/ml CURD - after 3 hrs at 35 C: 17,000/g CHEESE - after 7 days: 102,000/g CHEESE - after 34 days: 49,000/g

82 Staph. aureus in a semi-soft, raw milk, washed-rind cheese Where is the control measure? 82

83 FATE OF BACTERIAL PATHOGENS IN CHEESE where is the CCP? HARD CHEESE Curd production Maturation/ shelf life Salmonella +/- -- E. coli +/- -- Staph. aureus + -- Listeria +/- +/- or - MOULD-RIPENED SOFT CHEESE Curd production Maturation/ shelf life Salmonella ++ + E. coli Staph. aureus ++ + Listeria +/- ++ SOFT/SEMI-SOFT CHEESE Curd production Maturation/ shelf life Salmonella + +/- or - E. coli ++ +/- or - Staph. aureus + +/- or - Listeria +/- +/- or - Key: +++ Substantial growth possible (>2 log) ++ Moderate growth possible (2 log) + Slight growth possible (<2 log) +/- Survival, but no growth expected - Slow death expected (<1 log/month) -- Rapid death expected ( 1 log/month) 83

84 MMM. 84