This document discusses the analysis of water and milk. It outlines the ideal characteristics of safe drinking water and describes common waterborne diseases caused by viruses, bacteria, and protozoa. Methods for water testing include the presumptive coliform test, McCrady's probability table, and membrane filter method. Milk analysis examines the typical microflora present, diseases that can be transmitted through milk, pasteurization methods, and biological standards. Sampling techniques and chemical/microbiological tests for both water and milk are also outlined.

1. Analysis of Water and Milk
Dr Priya Santharam

2. Safe water
Free from micro organisms / chemical substances
Cool
Clear
Colourless
Devoid of disagreeable smell / taste

3. Drinking water is liable to contaminants….
Chemical / biological
Chemical :
– Industrial / agricultural waste
Biological:
– Faecal pollution of water

4. Water borne diseases
Viral : viral hepatitis A & E, poliomyelitis, rotavirus diarrhoea
Bacterial: cholera, typhoid, paratyphoid, dysentry,
diarrhoea due to E.coli, C.jejuni, Y.enterocolitica
Protozoal: Amoebiasis, Giardiasis, Balatidium coli diarrhoea
Helminthic: round worm, whip worm, thread worm

5. Bacteriological indicators
E.coli and coliform
Fecal streptococci ( Enterococcus faecalis)
Clostridium perfringens

6. Why choose coliforms?
Commensals in Intestinal tract
Easy detection
Longer survival
Resistance to chlorination

7. Sample collection and transport
Tap / pump outlet:
Sample from reservoir ( river, lake, streams)
Sample from dug well
Transported and examined within 1-3 hrs
Neutralisation of chlorine: sodium thiosulphate

8. Flora of water
Normal:
Natural water: Micrococcus, Pseudomonas, Serratia,
flavobacterium, Alkaligenes, Acinetobacter
Soil bacteria: Bacillus subtilis, Bacillus megaterium, Klebsiella spp
Contaminated:
Intestinal: E.coli, Klebsiella spp, Enterococcus fecalis, Clostridium
welchii
Sewage bacteria: Proteus vulgaris, Clostridium sporogenes,
Nocardia spp

9. Methods of analysis
Presumptive coliform and differential test
Detection of Enterococcus.fecalis / Cl.perfringens
Colony count

10. Presumptive coliform test
Multiple tube test:
– Most probable number of coliforms in 100ml water
– Double and single strength modified MacConkeys fluid medium+
durhams tube with bromocresol blue
Procedure: 50ml water + 50ml DSM
10ml water + 10ml DSM
1ml water + 5ml SSM each
0.1ml water+ 5ml SSM each
Incubated 37˚C for 48hrs. Then compared with McCrady probability
table

11. McCrady’s
Probability
Table

12. McCrady’s
Probability
Table

13. Eijkman test – confirmatory test
Positive presumptive culture tubes are subcultured to SSM.
Incubated at 44˚C for 24 hrs.
Production of gas and indole production is confirmatory

14. Other tests
• Membrane filter method
• Detection of
– fecal strep – glucose azide broth @ 45˚C
– Cl.welchii – litmus milk anaerobically - 5 days
• Colony count - 22˚C( organic matter) and 37˚C
• Biological examination for plankton –
objectionable water taste

15. Classification of drinking water
Presumptive
coliform
count/100ml
E.coli count
per 100ml
Class 1 Excellent 0 0
Class 2 Satisfactory 1 - 3 0
Class 3 Suspicious 4 - 10 0
Class 4 unsatisfactory > 10 0, 1 or more

16. Water needing analysis
Water used for dialysis: <200 cfu/ml of water
Water used in aerated soft drinks industries:
free from any microorganism

17. Milk analysis
Good culture media
Easily spreads diseases
Bacterial source
– Milk ducts of udder
– Milking equipment
– Milker – unclean hands / carrier
– Unclean udders & dust in milking shed
– Water – used for cleaning udders
– Diseased animals

18. Likely flora in milk
Acid forming: Lactic streptococci, Ent.faecalis,
Lactobacilli, Staphylococci
Alkali forming: Alkaligenes spp, Achromobacter
Gas forming: Coliform bacilli, Cl.welchii, Cl.butyricum
Proteolytic: B.subtilis, B.cereus, Pr.vulgaris

19. Milk borne diseases
Human diseases:
Typhoid, Paratyphoid, Cholera, Shigellosis, Enteropthogenic
E.coli, Staphylococcal food poisoning, Streptococcal
infections, TB, Hepatitis
Animal infections:
TB, Brucellosis, Streptococcal infections, Salmonellosis,
Qfever, Cowpox, Foot and mouth disease, Anthrax,
Leptospirosis, Milkers nodes, Y.enterocolitica

20. Pasteurisation
Holder method
– 63˚C for 30 min
Flash method
– 72˚C for 15 sec
Ultra high temperature
– 125 - 132˚C for 2 to 3 sec

21. Biological standards
Pasteurised milk – should not contain coliform in
0.1ml milk
– phosphatase test <10 μg of
p-nitrophenol / ml milk
Sterilised milk – satisfy turbidity test
Ultra heated milk - < 10 bacteria / 0.01ml milk

22. Sampling and viable counts
Retail bottle – unopened bottle
Large container – sterile dipper to 4oz sterile
screw capped bottle
Viable count – yeast extract milk agar
Coliform count – MacConkey fluid medium

23. Chemical tests
Methylene blue – viable bacteria reduce the dye in the milk kept
in a cool dark place decolourisation of milk
Resazurin test – series of colour changes
blue, lilac, mauve, pink, colourless on
complete reduction
Ten minute resazurin test done in creameries and compared with
Lovibond comparator

24. Phosphatase test – To test the presence phosphatase
inactivated by pasteurisation
substrate –disodium p-nitrophenyl phosphate
end product - p-nitrophenyl giving yellow colour to milk
Turbidity test- check for sterilisation
– Principle: milk boiled to sterilisation T˚ will have
precpitated all heat coagulable proteins. If
Ammonium sulphate is added to the milk,
filtered and boiled for 5 min no turbidity results
yellow

25. Detection of specific pathogens
Tubercle bacilli
– centrifuged milk – inoculated into guinea pigs
– Culture
Brucella
– Heavy inoculation on serum dextrose agar
– Centrifuged deposit into guinea pigs
– Serology – milk ring or whey agglutination tests