examination of fermented dairy product like yogurt including physical,chemical and sanitary examination

1. Fermented dairy products
Yogurt
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2. Semisolid cultured dairy products ,obtained from (milk, skimmed milk, conc .milk
recombined milk) after addition of starter culture.
Classification according to EOS
skimhalffull
0.5% not more than1.5%3%
cow
5.5%
bufflo
Fat%
9% & 8.25%9%8.5%8.75%S N F%
Fermented dairy yogurt:
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3. 3

4. Milk after clarification
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5. After opening
1- Physical examination
Before opening
-Signs of blowing
- leaking
-Gas formation
-Expired date
-Signs of abnormal flavour
- abnormal color
- growth of yeast or mold
- abnormal taste
Preparation of yogurt sample
- Random representative sample sent unopened to lab in ice box.
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6. 1- Soured flavour (over acidity)
-High amount of S.C used.
- increase in fermentation temperature .
-Increase in fermentation time .
-Failure of cooling after fermentation.
-Storage at high temperature.
2- Whey off (synersis)
-High amount of S.C used.
- increase in fermentation temperature .
-Increase in fermentation time .
-Failure of cooling after fermentation.
-Storage at high temperature.
-Inadequate heat treatment.
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7. 3- Off Taste flavour
4- Soft texture
-Inadequate heat treatment of raw milk.
-Impurities in milk used in manufacture.
-Impurities in S.C. used in manufacture.
-Bad selection of milk.
-Inactivation of S.C .
- decrease in time & temperature of fermentation.
-Inadequate heat treatment.
- Agitation during fermentation.
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8. 2- Blown can or swollen
- Growth of yeast and mold especially in fruity
yogurt. Leads to gas formation.
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9. b) T.S%
2- Chemical examination
a) fat% C) Moisture % d) Ash% e) Protein% f)Lactose%
a) Determination of fat%
-Gerber method by milk
butyrometer
-Rosegottelib
Method
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10. b) T.S%
2- Chemical examination
a) fat% C) Moisture % d) Ash% e) Protein% f)Lactose%
By evaporation
method
By Ignition
method
Bendict’s quantitive
method
By Kjeldhal
method
By evaporation
method
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11. 3- Sanitary & keeping quality examination
Acidity %
20 ml D.w
10 g yogurt sample
1ml Ph.Ph. 1%
NaoH N/9
Titrate till
faint pink
color
R
R
10
Acidity degree= Rx 10
Acidity % =
Normal acidity % ,85%-0,9% Comment?????
Microbiological examination
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12. Microbiological examination
Simple activity test: for detection the activity of S.C
10 ml milk previously
wormed at 35c/30 min.
1 g S.C sample
Shake well
Incubation
40-42c/4h
Calculate acidity %
(0.85-0.90%)
Normal acidity % ,85%-0,9% Comment?????
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13. Thank you for attention
Presented by :
Dr. Dina A. B. Awad
Lecturer of food hygiene department
Faculty of veterinary medicine
Benha university , Egypt
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