Concentrated milks such as evaporated milk and sweetened condensed milk are produced through processes like evaporation and membrane processing to remove water. This reduces weight and volume for easier transport and storage while extending shelf life. Concentrated milks are used to supplement fresh milk supply and in food manufacturing. Technological steps include milk standardization, heating, addition of sugar for condensed milk, concentration, cooling, and canning. Microbial defects include blown cans from gas production and thickening or curdling from bacterial growth. Non-microbial defects involve lactose crystallization or Maillard browning from excessive heating. Proper processing and storage are needed to prevent defects in concentrated milks.

1. Notes on
Concentrated milks
( Technology & Faults)

2. 2

3. Concentrated milks
Long life milk products
Milk powder
3

4. 1- Reduction weight &volume so– easy transport & small storage place.
2- Extended the shelf life time (method of milk preservation).
3- Stock for seasonal fluctuation in milk production.
4- Easily used after reconstitution to be fluid milk .
5-Used in adverse conditions in wars.
6-Milk powders are used by consumers as a substitute for fresh milk &as
ingredients for the manufacture of a range of processed food products.
7-High N.V.
4

5. Sweetened condensed milk
(condensed milk) 75% total solids
( 45% sugar +30% milk solids)
Un sweetened evaporated milk
25% milk solids
no sugar
Methods of water removal:
1- Evaporation (most common)
by heat under vacuum.
2- Membrane processing
(UF&RO)
3- Freezing
1- Concentrated milks

6. 6
Membrane processing
Retenate
Feed (MILK)
Permeate

7. 7
Feed (milk)
water
Water, salts
Water,salts,sugar
Water,salts,sugar,Protein
and Fat

8. Technological steps of concentration
1- Selection & preparation of milk
2- Standardizedization
3- Casein stabilization
Spore& thermodurics bacteria
Color& flavour abnormalities
Clafication by centrifugal separator
stabilization (Sod citrate.)
preheating
The ratio of fat to total solid should be 1:3.4
4- Preheating
8
85 C for 10-20 min
5- Concentration
50-55C for about 2 h
(1:3 in evaporated milk or
1:2.5 in condensed milk).

9. 9
Casein stabilization:
Casein has tendency to precipitate when subjected to high heat treatment that leads
to gelation or thickening in the final products -------------So, addition of stabilizing
salts as trisod.phosphate or sod. citrate 0.2-0.3 g/kg milk---------------- These salts act
as emulsifiers , help in homogenization and prevent precipitation of caseins.
Preheating:
It is applied before milk concentration at 85ºC/10-20min.or 115-128ºC/1-6 min.
it is important for:
1-Improve milk quality.
2- Inactivation of milk enzymes.
3-Help in stabilization of casein micelles.
4- Temperature adjustment before concentration process.
5- Prevent sticking to evaporator.

10. Technological steps of un-Sweetened evaporated milk
6- Homogenization
7- Rapid cooling
8- Filling & canning
50 C under high pressure
Atmospheric method
9- Sterilization
17 C within 15-20 min )
10 C or at room temperature 10
4 C to prevent lactose crystalization
10 - Cooling -
11 - Storage

11. 11
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.
Effect of homogenization
https://dairyprocessinghandbook.com/chapter/homogenizers

12. Technological steps of Sweetened condensed milk
5- Addition of sugar 16-18 kg/100 litter milk
6- Concentration
7-Cooling & crystallization Preheated,
Carefully selected
57.2 C.
Forced crystallization
8- Filling & canning
Atmospheric method or vacuum method)
12-16 C
Homogenization
x
Sterilization
x 12

13. 13
Nutritive value of concentrated milk
-High protein
- High lactose
- High of mineral content
- Easily digested

14. Evaporated milkCondensed milk
Concentrated milk defects:
Microbial defects Non microbial defects
14

15. Microbial defects of sweetened condensed milk
(blown, thickening, buttons, rancidity)
1- Blown cans
- Caused by Co2 or H2 or mixture (Microorganism dependent)
-Contents (highly odorours)
Osmotolerant gas producing yeast
( Torula latis condensei, Saccharomyces
spp,candida)(alcoho& gases)
Coliforms
(poor sanitary conditions)
(Acid flavour & gas)
Bacillus lactis aerogenes
Control
-Using good sugar quality
- Efficient plant sanitation and canning condition
- not store in hot place
Common in worm months
Puncture, sealing
15

16. 2- Thickening Acidity &
cheesey
odour
-Bacilus subtilis
-Bacilis micoids
-B.stearothermophilus
- Micrococcus strains
Rennin
like enz.
Clotting & aggregation
for milk casein
So, can be detected by souring & cheesy texture due to curd formation
Control
-Low storage temp.
-Improve plant sanitation
-Bactofugation (???)
16

17. Small masses of mould mycelium &
coagulated casein usually colored white
to brown may be found in the surface or
subsurface layers
3- Buttons
bad taste
cheesy
consistency
-Pencillum
-Asperigillus
Clotting enzyme
cause localized
coagulation
Detected by presence of mould mycelium ,coagulated casein , hard cheesy consistency
&colord curd
Control -Canning under a septic conditions (vaccum package)
-Improve plant sanitation (CIP).
-Storage below (12-15c).
-Inversation ( gasses).
4- Rancidity -Contamination of milk by lipase producing bacteria.
17

18. Microbial defects of unsweetened evaporated milk
Sources
Insufficient heat
tretment
Post heat
treatment
contamination
(leaky cans)
- B.coagulans & B.Stearothermophilus cause acid coagulation &cheesy odor.
- B.subtilis cause non acid curd then digested to brownish liquid with bitter taste.
- B.megaterium cause cheesy odor curd with some gases.
- Closterdia spp cause gas production with puterifaction and H2S.
18

19. Non- Microbial defects of concentrated milk (industry)
19

20. Small hard crystals due to:
1- Slow cooling after heating
2- Insufficient dissolving of sugar
20
Selection & preparation of milk
Cooled clarified , standardized milk at 4ºc
Preheated, standardized, stabilized ,conc. milk
Spore& thermodurics bacteria
Color& flavour abnormalities
Clafication by centrifugal separator
Milk standardization (fat %)
stabilization (Sod citrate.)
preheating
Addition of sugar
Rabid cooling
Milk standardization (sugar index)
Unsweetened concentrated milk
Package (filling & canning)
Concentration under vacuum

21. stabilization (Sod citrate.)
preheating
Change in the colloidal sol.
Of proteins due to storage
and excessive heating or
evaporation
21

22. Color& flavour abnormalities
Small clots float on milk surface &
cheesy consistency due to selection
of mastitic milk with abnormal high
albumen & globulin
22
Selection & preparation of milk
Cooled clarified , standardized milk at 4ºc
Preheated, standardized, stabilized ,conc. milk
stabilization (Sod citrate.)
preheating
Addition of sugar
Rabid cooling
Milk standardization (sugar index)
Unsweetened concentrated milk
Package (filling & canning)
Concentration under vacuum

23. preheating
Concentration under vacuum
Due to the effect of high
temperature During
processing result in charring of
lactose
23

24. Chemical abnormalities
Selection of milk contain high
lipase enz.or cystic ovary or
milk at the end of lactation and
presence of cupper residues.
24
Selection & preparation of milk
Cooled clarified , standardized milk at 4ºc
Preheated, standardized, stabilized ,conc. milk
stabilization (Sod citrate.)
preheating
Addition of sugar
Rabid cooling
Milk standardization (sugar index)
Unsweetened concentrated milk
Package (filling & canning)
Concentration under vacuum

25. Due to overfilling of can by cold milk
which under heating expands
Or due to chemical action on the
metal of the cans.
25

26. product derived from concentrated milk with sugar addition
T.S% =84-90% Water%= 16% Can be cut by a knife
1-Block milk
2- Caramelized condensed milk
Concentrated milks
Market mostly as a paste or in powder or
tablet form .Produced by concentrating &
caramelizing milk With 18 to20% sucrose or
glucose with or without Flavour
supplement.
Other
26

27. 3- Condensed skim milk
Obtained by a simple concentration of skim
milk by vacuum evaporation or RO consider
more cheaper---- with protein ratio 50-80%
4- Recombined concentrated milk
Used as substitution of whole milk in
area where there is shortage in supply. it
prepared from milk powder.
27

28. Thank you for attention
Presented by :
Dr. Dina A. B. Awad
Lecturer of food hygiene department
Faculty of veterinary medicine
Benha university , Egypt