Microbes - Friend or Foe

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Microbes - Friend or Foe: 

Microbes - Friend or Foe 1 Microbes - Friend or Foe Dairy Products

Potential Pathogens in Milk: 

Microbes - Friend or Foe 2 Potential Pathogens in Milk Listeria Salmonella E. coli Campylobacter Yersinia Staphylococcus aureus Clostridium

Listeria monocytogenes: 

Microbes - Friend or Foe 3 Listeria monocytogenes Soil, dust, mud and animals Can multiply at refrigeration temperatures Can cause meningitis and septicaemia

Salmonella: 

Microbes - Friend or Foe 4 Salmonella Over 2000 types Cows, poultry, pigs Diarrhoea, cramps, vomiting and fever

Escherichia coli: 

Microbes - Friend or Foe 5 Escherichia coli Rare, infective dose 10 cells Faecal material into milk Abdominal pain and severe diarrhoea

Clostridium perfringens: 

Microbes - Friend or Foe 6 Clostridium perfringens Environment, human and animal intestines Ingestion of large numbers cause illness Cramps and diarrhoea

Staphylococcus aureus: 

Microbes - Friend or Foe 7 Staphylococcus aureus Nose, throat and skin of healthy people Can cause food poisoning when ingested Abdominal pain and vomiting

Source of potential pathogens: 

Microbes - Friend or Foe 8 Source of potential pathogens The cow – coat, udders, faecal contamination Environmental - Soil, bedding, food Mastitis Milk handling equipment Producer Prolonged holding of milk in silo Mixing old and new milk

Hygiene procedures : 

Microbes - Friend or Foe 9 Hygiene procedures Daily cleaning of milking apparatus Farmer washing hands / wearing gloves Not milking cows with mastitis Not feeding hay/ silage while milking

Hand swabs : 

Microbes - Friend or Foe 10 Hand swabs

Raw Milk Quality : 

Microbes - Friend or Foe 11 Raw Milk Quality

Temperature : 

Microbes - Friend or Foe 12 Temperature Tested on arrival Below 5 ºC Organisms and temperature influence bacterial proliferation Number of bacteria per ml after 24 hours 5ºC 2,600 10ºC 11,600 12.5ºC 18,800 15.5ºC 180,000 20ºC 450,000

Animal cell counts: 

Microbes - Friend or Foe 13 Animal cell counts Test for low level of animal cells Epithelial cells and white blood cells Mastitis High level indicates sub clinical mastitis Pathogens Streptococcus & S. Aureus

Low levels of bacteria: 

Microbes - Friend or Foe 14 Low levels of bacteria Resazurin test Changes colour by actively proliferating bacteria Blue, Lilac = Low level of bacteria Pink, white = High level - Retest

Raw Milk Quality: 

Microbes - Friend or Foe 15 Raw Milk Quality No added water No antibiotic residues – Starter cultures No taints Good compositional quality

Typical Milk Composition: 

Microbes - Friend or Foe 16 Typical Milk Composition

Other Dairy Products: 

Microbes - Friend or Foe 17 Other Dairy Products

Summary so far: 

Microbes - Friend or Foe 18 Summary so far Pathogens Source Effect Milk quality How do we eliminate any pathogens in raw milk?

Pasteurisation: 

Microbes - Friend or Foe 19 Pasteurisation Discovered by Louis Pasteur Milk is heated to 72 o C for at least 15 seconds. Cooled immediately. Pasteurisation kills harmful bacteria (Pathogens). Mycobacterium paratuberculosis .

Phosphatase test: 

Microbes - Friend or Foe 20 Phosphatase test To test pasteurisation process efficacy To check no raw milk contamination Phosphatase is an enzyme Inactivated by pasteurisation Any remaining phosphatase activity = pasteurisation process not effective

Friendly Microbes : 

Microbes - Friend or Foe 21 Friendly Microbes Milk to vats Starter cultures added Bacteria Lactose Lactic Acid

Examples of Starter cultures: 

Microbes - Friend or Foe 22 Examples of Starter cultures Blue stilton Lactobacillus lactis subsp diacetylactis Leuconostoc mesenteroides subsp cremoris White stilton Lactobacillus lactis subsp lactis Lactobacillus lactis subsp cremoris

Lactococcus lactis ssp cremoris: 

Microbes - Friend or Foe 23 Lactococcus lactis ssp cremoris

Bacteria in Yogurt: 

Microbes - Friend or Foe 24 Bacteria in Yogurt Lactobacillus bulgaricus Streptococcus thermophilus Lactobacillus acidophilus Bifidobacterium

Why do we need friendly bacteria?: 

Microbes - Friend or Foe 25 Why do we need friendly bacteria? Acidification of cheese by starter bacteria Results in optimum lactic acid content Allows protein coagulation by rennet = curd Stir and Cut the curd – release whey Fat retained in the coagulum Water drains out in the whey

Other effects of Bacteria: 

Microbes - Friend or Foe 26 Other effects of Bacteria Produce gases – Edam Produce flavour and aroma Produce enzymes

Other Microbes in Cheese: 

Microbes - Friend or Foe 27 Other Microbes in Cheese Moulds: Penicillium camembertii Penicillium roquefortii Added to affect flavours Others: Micrococcus Yeasts Moulds

Blue Stilton Production: 

Microbes - Friend or Foe 28 Blue Stilton Production Raw Milk (5°C) Fat adjustment (Standardisation) Pasteurisation (72°C, >15 secs) Transfer to Vat (30°C) Add Starter Culture (Bacteria) Add Blue Mould Add Rennet (To coagulate protein)

Blue Stilton Production: 

Microbes - Friend or Foe 29 Blue Stilton Production Acid development and curd formation Drain whey off curd Salt and mill curd Fill hoops Drainage (20°C) Cool, de-hoop and cling film (10°C) Remove cling film

Blue Stilton Production: 

Microbes - Friend or Foe 30 Blue Stilton Production Maturation (13°C) Skewering (To allow air in) Further maturation (13°C) Transfer to cold store (5°C) Cutting & Wrapping / Packing

Summary : 

Microbes - Friend or Foe 31 Summary Potential pathogens in milk Source, effect and prevention Testing of raw milk quality Pasteurisation Friendly bacteria Blue stilton production