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Microbes - Friend or Foe

Microbes - Friend or Foe. Dairy Products. Potential Pathogens in Milk. Listeria Salmonella E. coli Campylobacter Yersinia Staphylococcus aureus Clostridium . Listeria monocytogenes. Soil, dust, mud and animals Can multiply at refrigeration temperatures

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Microbes - Friend or Foe

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

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

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

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

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

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

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

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

  10. Hand swabs Microbes - Friend or Foe

  11. Raw Milk Quality Microbes - Friend or Foe

  12. Temperature • Tested on arrival • Below 5ºC • Organisms and temperature influence bacterial proliferation 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 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 Microbes - Friend or Foe

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

  16. Typical Milk Composition Microbes - Friend or Foe

  17. Other Dairy Products Microbes - Friend or Foe

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

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

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

  23. Lactococcus lactis ssp cremoris Microbes - Friend or Foe

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

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

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

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