lecture about the structure the milk fat globule and milk sugar (lactose) and effect of homogenization on fat globules indicating advantage and disadvantages.

1. 1
Water:
Milk contain 87.5% water of the total volume of milk. The major part 84%is called free water
The minor part 3.5% is called bound water in which the milk constituents is dissolved.

2. Milk Fat globules or butter fat or fat droplet synthesis and forms
- Bovine milk contains 3–5% of fat, occurring in a dispersed form called fat globules.
- Milk fat globules are synthesized in epithelial cells of the mammary gland.
- Cream is examples of fat-in-water (or oil-in-water) as fat present in the form of emulsions.
- The milk fat exists as small globules dispersed in the milk serum
- Milk fat composed of two main structures: fat droplet surrounded with fat globule
membrane that dispersed in milk in the form of emulsion.
N.B: This emulsion form is
stabilized by the very thin
membrane only 10-20 nm thick
(1 nm = 10–9 m) which surrounds
the globules.
2

3. 3
The diameter of the milk fat globule (MFG) ranges
from 0.1-12 µm with an average of around 4.5µm.

4. So, It is well known that if raw milk is left to stand, fat layer will separate. Where fat globules
will cream due to the differences in densities between the fat and plasma phases of milk. So,
in cold raw milk, creaming takes place faster aggregation of fat globules under the influence
of a protein called agglutinin.
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As the fat globules are not only the largest particles in the milk but also the lightest (density
at 15.5 °C = 0.93 g/cm3), they tend to rise to the surface when milk is left to stand in a wide
vessel for a while.
1- Size of fat globules : the small size of the fat globules makes creaming a slow process.
Cream line formation
2- The temperature rise than 40ºCaggregates are easily broken up by heating or mechanical TTT.
Factors affecting Cream line formation
3- Skimming of milk fat : no cream line formation.
4- Milk homogenization: decrease cream line formation.

5. 5
Milk homogenization of milk prevents this creaming by decreasing the diameter and size
distribution of the fat globules. Homogenization has become a standard industrial process,
universally practiced as a means of stabilizing the fat emulsion against gravity separation.
Milk homogenization
N.B: Homogenization efficiency increases with temperature
from 42◦C to 72◦C and stabilizes around 72◦C - 77◦C

6. 6
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

7. 7
Chemical composition of fat globule
It composed of fat droplet as a core surrounded with FGM. The droplet interior is made up
of a triglyceride core surrounded by the fat globule membrane. This membrane, 10–20 nm
in diameter, protects the globules mainly against coalescence and lipolytic activity.
Milk fat is dispersed in milk as small, spherical globules, stabilized in the form of emulsion by its
surrounding membrane.

8. is a mixture of different fatty-acid esters called triglycerides, which are composed of an
alcohol called glycerol and various fatty acids. Glycerides make up almost 99 % of milk fat.
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Milk fat droplet
Milk fat droplet consists of
triglycerides (the dominating
components), di- and
monoglycerides, fatty acids,
sterols, carotenoids (giving
the yellow colour of the fat)
and vitamins (A, D, E, and K).
Trace elements are minor
components.

9. Some of the components are emulsifiers and prevent
individual globules from joining together.
MFGM protects fat globules from lipolysis catalysed by
lipase activity, mainly linked to the casein micelles.
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Milk fat membrane (FGM)
Milk fat globule mambrane, (MFGM) composed by lipoproteins, phospholipids, trace
elements, enzymes, and carotene bound water.

10. 10
Milk fat membrane (FGM)
The phospholipids in milk fat globule
membrane generally are characterized
by a higher content of unsaturated fatty
acids and a lower content of short-chain
fatty acids (C4–C10) in comparison to the
milk fat. The globule membrane also
contains vitamin E in trace amounts,
which is important due to its
antioxidative functions. The globule
membrane also contains carotene,
although a majority of this group of
compounds is located inside the globule.

11. 11

12. 12
Milk Lactose or Milk Sugar
It is a disaccharide composed of the monosaccharides glucose come from blood and galactose (
??) synthesized in golgi apperatus in mammary gland both linked by glycosidic link.
It is only found in milk in its natural state , synthesized in mammary gland.

13. In order to digest lactose, your body digestive tract produces the enzyme lactase. Lactase
is produced by the small intestine and secreted to break down lactose into its simpler
forms of sugar—glucose and galactose. These simple sugars are easily absorbed into the
bloodstream and used as energy.
Lactase
N.B : Lactase enzyme can be produced
from digestive tract or from bacterial
origin.
lactose glucose+ galactose
How Lactose is Digested
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14. Lactose intolerance occurs when you don't produce enough lactase or do not digest lactose
well. Due to lack of lactase enzyme or due to injury in epithelial cell lining so, the body can
not utilize lactose and can not split it in to glucose and galactose.
Symptoms of Lactose Intolerance:
1- usually occur within 30 minutes to two hours after eating dairy products.
2- bloating, an uncomfortable feeling of fullness, cramping, abdominal pain, diarrhea,
gas, and nausea.
Besides avoiding dairy products, there are lactose-free and lactose-reduced milk
products at most grocery stores. Can take fermented milks
Avoiding Lactose Intolerance
Lactose Intolerance people
Lactase
lactose glucose+ galactose
x
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15. 1- Low solubility cause problems in processing like crystallization like in ice-cream & conc. milk
causing sandy taste.
2- Maillard reaction (sugar (CHO) + amine (NH2)) where there was reaction between amino
group of protein and the aldhyde group of sugars producing brown color and off flavour.
This reaction (Browning reaction) intensity depend on :
1- Conc. Of lactose &pt. 2- pH 3- time &temp. of processing
Solubility & crystallization of lactose
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16. Fermentation of lactose
LAB
lactose lactic acid + vol. by product
Increase lactic acid amount will stop the action of LAB.
Properties of lactose
1- It is present in form of opaque solution (true solution).
2- It is less sweet than sucrose (5% sucrose=10% lactose) (double).
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17. Thank you for attention
Presented by :
Dr. Dina A. B. Awad
Lecturer of food hygiene department
Faculty of veterinary medicine
Benha university , Egypt