1. The document discusses different thermal treatments for milk including pasteurization, sterilization, and boiling. 2. Pasteurization involves heating milk to temperatures between 63-85°C for short periods of time to minimize pathogens while preserving chemical and physical properties. Common pasteurization methods are listed. 3. Sterilization or long-life milk involves higher temperatures over longer periods to destroy all microorganisms allowing milk to be stored at room temperature for several months. Methods of in-bottle and UHT sterilization are described.

1. Dr. Dina A. B. Awad
Lecturer food hygiene and control , faculty of veterinary medicine
Benha university, Egypt

2. Milk thermal treatments
1- Pasteurization 2- Sterilization
3- Boiling
Chemical, organoleptic properties of milk
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3. 1- Pasteurization processes
Raw milk
Certain
temperature
Certain
time
Sudden cooling
Minimizing
pathogenic organisms
Aim Associated
Minimal chemical,
physical changes
63°C/30 min
72°C/15sec
85°C/2-4 sec
4-10° C

4. Receiving of raw milk at 4 °C
Organoleptic examination
Acidity determination (C.O.B,A.P.T)
Dirt & sediment examination
Antibiotic residues & T.B.C & MBRT
Filtration 35-50 °C OR clarification 4.5 °C
Standardization
Homogenization
Pearson square
(add cream or skim milk)
(LTLT) 63C/30min
Kill 98% bacteria
Not affect chemical properties
1- avoid cream line
2-mouth feel
3- improve color
Pasteurization process
(HTST) 72C/ 15 sec.
Kill 99% bacteria
Slightly affect chemical properties
(Flash method) 85C/ 2-4 sec.
Kill 99.5% bacteria
Slightly affect chemical properties
Pasteurization
flow chart
Cooling less 7°C (inhibit thermoduric bacteria)&packaging (7 days)
Coxiella
burnteii

7. Milk
receiving

8. clarification 4.5 °C
Milk mechanical clarifier
Filtration 35-50 °C
Applied under centrifugation
(ppt dirt) Producing clarifier slime
Remove dust, somatic cell,some bacteria
Using disc wool or synthetic filters
Remove visible dirt and sediment,
coarse particles
But not the bacterial cells

9. Standardization

10. 10
1st stage
2nd stage
Advantages:
1- Smaller fat globules --no cream-line formation
2-Whiter and more appetizing colour.
3-More better mouthfeel.
4-Better stability of cultured milk products.
Disadvantages:
1-May increased sensitivity to light – sunlight can
result in “sunlight flavour” .
2-More susceptible for rancid flavour.
April /2020
Dr.Dina A. B.Awad
Homogenization

11. Factors affecting keeping quality of pasteurized milk
Initial
bacterial
count
Efficiency of
pasteurization
Process
Sudden
cooling at
5-7 C
Post
pasteurization
contamination
Time –temperature factor (accurate) (phosphatase enz.)
To stop the action of bacteria that resist pasteurized temperature.
Insufficient clean piplines,tanks,filling machine, contamination water supply, poor personal hygiene
To avoid that??????????????????????????????????????????????????????????????????????????????
- Thermophilic bacteria-- resist holding method but HTST destroy it. St. coccus thermophilus
Thermoduric bacteria– resist pasteurization (spore former) as bacillus cereus,bacillus subtilus. (bactofugation)
Pschrophilic bacteria –as pseudomoans bacteria produce heat resistant enzymespoilage in pasteurized milk.(thermisation)

12. Spoilage of pasteurized milk
When stored at high temperature or at room temperature or kept opened – shelf life
Growth thermophilc bacteria
5.5pH Growth of lactobacilli
4 or less pH
N.B
Survive thermoduric bacteria,
bacillus (Sweet curdling)
(Rennin like enz.)
Mould &yeast pH
--Their presence indicate post
pasteurization contamination
Extend shelf life (ESL)--- means extended shelf life of the product
With maintaining its nutritional value (ultra-pasteurization )
125-130°C –2-4 sec

13. Milk sterilization (long
life milk)
A process in which milk is heated to a certain time that all microorganisms are destroyed
Producing high quality milk could stored for long time at room temperature (tropical areas).
Methods of
sterilization
In –bottle (container) UHT(uprization)
Sterilization for both milk &bottle

14. Flow chart for in -bottle sterilization
APT Test negative
Remove debris(brown sediment??)
Avoid cream line formation
Initial removal bacterial spores
Pre-serilization of milk at 80 C
Bottling in pre-wormed bottles
Milk in bottle sterilization
Cooling gradual within 1 hr
At 115-120/15-20 min in steam
Kept at room temp. 6 months
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15. Flow chart UHT sterilization
APT Test negative
Remove debris(brown sediment??)
Direct heating type
Inject milk in steam
Fearing from unsterile packaging
UHT process 140 – 150° C/1-4 sec.
Homogenization (avoid aggregates)
Packaging under O3
Page 132
Tubular heating using
Plate heat exchanger
Steam instead of hot water

16. Advantage and disadvantages UHT sterilization
Milk is effectively sterilized Gelation, ppt protein, loss vit.,cooked
Spoilage of UHT sterilization
Page 130
Rare:::::::::but,,,,,,,,,,,,,,,,,,heat resistant spores ---
survived Post- heat treatment
contamination
Psychrotrophic
organisms
Dual heat treatment
140C/5 sec
60 C/5 min
Bactofugation