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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

Microbes - Friend or Foe

Dairy Products

Microbes - Friend or Foe

potential pathogens in milk
Potential Pathogens in Milk
  • Listeria
  • Salmonella
  • E. coli
  • Campylobacter
  • Yersinia
  • Staphylococcus aureus
  • Clostridium

Microbes - Friend or Foe

listeria monocytogenes
Listeria monocytogenes
  • Soil, dust, mud and animals
  • Can multiply at refrigeration temperatures
  • Can cause meningitis and septicaemia

Microbes - Friend or Foe

salmonella
Salmonella
  • Over 2000 types
  • Cows, poultry, pigs
  • Diarrhoea, cramps, vomiting and fever

Microbes - Friend or Foe

escherichia coli
Escherichia coli
  • Rare, infective dose 10 cells
  • Faecal material into milk
  • Abdominal pain and severe diarrhoea

Microbes - Friend or Foe

clostridium perfringens
Clostridium perfringens
  • Environment, human and animal intestines
  • Ingestion of large numbers cause illness
  • Cramps and diarrhoea

Microbes - Friend or Foe

staphylococcus aureus
Staphylococcusaureus
  • Nose, throat and skin of healthy people
  • Can cause food poisoning when ingested
  • Abdominal pain and vomiting

Microbes - Friend or Foe

source of potential pathogens
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

hygiene procedures
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

hand swabs

Hand swabs

Microbes - Friend or Foe

raw milk quality

Raw Milk Quality

Microbes - Friend or Foe

temperature
Temperature
  • Tested on arrival
  • Below 5ºC
  • Organisms and temperature influence bacterial proliferation

Microbes - Friend or Foe

animal cell counts
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

low levels of bacteria
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

raw milk quality15
Raw Milk Quality
  • No added water
  • No antibiotic residues – Starter cultures
  • No taints
  • Good compositional quality

Microbes - Friend or Foe

typical milk composition
Typical Milk Composition

Microbes - Friend or Foe

other dairy products
Other Dairy Products

Microbes - Friend or Foe

summary so far
Summary so far
  • Pathogens
  • Source
  • Effect
  • Milk quality
  • How do we eliminate any pathogens in raw milk?

Microbes - Friend or Foe

pasteurisation
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

phosphatase test
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

friendly microbes
Friendly Microbes
  • Milk to vats
  • Starter cultures added

Bacteria

Lactose Lactic Acid

Microbes - Friend or Foe

examples of starter cultures
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

lactococcus lactis ssp cremoris
Lactococcus lactis ssp cremoris

Microbes - Friend or Foe

bacteria in yogurt
Bacteria in Yogurt
  • Lactobacillus bulgaricus
  • Streptococcus thermophilus
  • Lactobacillus acidophilus
  • Bifidobacterium

Microbes - Friend or Foe

why do we need friendly bacteria
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

other effects of bacteria
Other effects of Bacteria
  • Produce gases – Edam
  • Produce flavour and aroma
  • Produce enzymes

Microbes - Friend or Foe

other microbes in cheese
Other Microbes in Cheese
  • Moulds: Penicillium camembertii Penicillium roquefortii
  • Added to affect flavours
  • Others: Micrococcus Yeasts Moulds

Microbes - Friend or Foe

blue stilton production
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

blue stilton production29
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

blue stilton production30
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

summary
Summary
  • Potential pathogens in milk
  • Source, effect and prevention
  • Testing of raw milk quality
  • Pasteurisation
  • Friendly bacteria
  • Blue stilton production

Microbes - Friend or Foe