Microbes - Friend or Foe1 Dairy Products

Microbes - Friend or Foe2 Potential Pathogens in Milk Listeria Salmonella E. coli Campylobacter Yersinia Staphylococcus aureus Clostridium

Microbes - Friend or Foe3 Listeria monocytogenes Soil, dust, mud and animals Can multiply at refrigeration temperatures Can cause meningitis and septicaemia

Microbes - Friend or Foe4 Salmonella Over 2000 types Cows, poultry, pigs Diarrhoea, cramps, vomiting and fever

Microbes - Friend or Foe5 Escherichia coli Rare, infective dose 10 cells Faecal material into milk Abdominal pain and severe diarrhoea

Microbes - Friend or Foe6 Clostridium perfringens Environment, human and animal intestines Ingestion of large numbers cause illness Cramps and diarrhoea

Microbes - Friend or Foe7 Staphylococcus aureus Nose, throat and skin of healthy people Can cause food poisoning when ingested Abdominal pain and vomiting

Microbes - Friend or Foe8 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 Foe9 Hygiene procedures Daily cleaning of milking apparatus Farmer washing hands / wearing gloves Not milking cows with mastitis Not feeding hay/ silage while milking

Microbes - Friend or Foe10 Hand swabs

Microbes - Friend or Foe11 Raw Milk Quality

Microbes - Friend or Foe12 Temperature Tested on arrival Below 5ºC Organisms and temperature influence bacterial proliferation Number of bacteria per ml after 24 hours 5ºC2,600 10ºC11, ºC18, ºC180,000 20ºC450,000

Microbes - Friend or Foe13 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 Foe14 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 Foe15 Raw Milk Quality No added water No antibiotic residues – Starter cultures No taints Good compositional quality

Microbes - Friend or Foe16 Typical Milk Composition

Microbes - Friend or Foe17 Other Dairy Products

Microbes - Friend or Foe18 Summary so far Pathogens Source Effect Milk quality How do we eliminate any pathogens in raw milk?

Microbes - Friend or Foe19 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.

Microbes - Friend or Foe20 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 Foe21 Friendly Microbes Milk to vats Starter cultures added Bacteria LactoseLactic Acid

Microbes - Friend or Foe22 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 Foe23 Lactococcus lactis ssp cremoris

Microbes - Friend or Foe24 Bacteria in Yogurt Lactobacillus bulgaricus Streptococcus thermophilus Lactobacillus acidophilus Bifidobacterium

Microbes - Friend or Foe25 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 Foe26 Other effects of Bacteria Produce gases – Edam Produce flavour and aroma Produce enzymes

Microbes - Friend or Foe27 Other Microbes in Cheese Moulds:Penicillium camembertii Penicillium roquefortii Added to affect flavours Others:Micrococcus Yeasts Moulds

Microbes - Friend or Foe28 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 Foe29 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 Foe30 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 Foe31 Summary Potential pathogens in milk Source, effect and prevention Testing of raw milk quality Pasteurisation Friendly bacteria Blue stilton production