Composition
According to their fat content, the milk will be separated into: whole milk, semi-skimmed milk and skimmed milk. Depending on the method of sterilization, we also speak of pasteurized milk or UHT milk (Upérisation à Haute
Temperature, simplified to Ultra High Temperature later).cow’s milk
We will use UHT milk, which makes up almost the entire French milk market (more of 97% of fluid milk sales).
Sterilized at over 135°C for a few seconds, UHT milk undergoes total destruction of the
germs, allowing it to be stored for months at room temperature.
1) Fat
The energy value of milk (in kcal) is determined by its fat content (lipids) ; the higher the fat content, the more energy and therefore more calories the milk will contain.
Cows’ diet and breed can influence the lipid content of the milk at the time of treats. For example, by adding flaxseed to the cow’s feed, the milk will be naturally richer in omega-3.
This fat contains approximately 406 different fatty acids, i.e. 60 to 70% fatty acids. saturated fatty acids (SFA) and 30 to 40% unsaturated fatty acids (UFA), mainly monounsaturated.
→ SFAs: those with short chains are particularly well digested and quickly used as
energy source by the body.
→ AGI: in the group of monounsaturates, oleic acid is the main one. It is the latter that found in olive oil. Milk contains few polyunsaturated fatty acids (less than 8%).
Skimmed milk contains almost no or no fatty acids.
Essential fatty acids (EFAs), alpha-linolenic acid (omega 3) and linoleic acid (omega 6) are very low in cow’s milk, the best sources of these fatty acids being the vegetable oils. Only linoleic acid (C18:2,n-6) is present in very small amounts in milk. cow (less than 2 %) (3 ).
EFAs are essential to our body and will therefore be included in infant formulas.
2) Protein
Proteins are composed of caseins, soluble proteins and enzymes. We differentiate:
- 80% “slow” proteins (caseins), which are insoluble, heat-stable and very low in fat. resistant to proteolysis, but incriminated in the majority of milk protein allergies from cow. Casomorphine is an opioid peptide derived from the degradation of casein, exerting a powerful secretagogue function of intestinal mucus (4).
- 20% “fast” proteins, found in whey (2-3% of the total whey protein), and of α-lactalbumins, 40% of β-lactoglobulins, lactoferrins, lactoferricins), are soluble, thermostable and very resistant to digestion. α-lactalbumin is involved in the biosynthesis of lactose. Without it there would be no lactose. in milk, however, the suppression of the expression of this protein is not possible.
to obtain lactose-free milks (5).
Lactoferricin is a peptide obtained in the stomach during the cleavage of bovine lactoferrin (6). - other proteins are present in “trace” amounts (<0.01%), such as the growth.
Animal proteins have a higher nutritional value than vegetable proteins because they contain in satisfactory proportions all the amino acids essential for the organism.
3) Carbohydrates
Milk contains carbohydrates mainly in the form of lactose (97%). The latter favours the absorption of minerals, especially calcium, and plays a positive role on the intestinal flora with prebiotic action.
Lactose is hydrolysed in the digestive tract by lactase into glucose and galactose, which are absorbed by the digestive tract.
then separately. Lactose has a low sweetening power (7).
The carbohydrate content is comparable for the different types of cow’s milk. There are semi-skimmed milks with reduced lactose content, which contain the same value of energy, the same fat, protein and carbohydrate content but almost no fatty acids,
of vitamins and minerals.
4) Minerals and vitamins
Cow’s milk is particularly rich in calcium (120 mg/100 g) and this content is comparable for different types of milk.
The Ca/P ratio is favourable to the assimilation of calcium by the organism, but overall, calcium milk is well absorbed due to the presence of lactose, proteins, peptides, etc.
As far as vitamins are concerned, milk is an important source of vitamins but especially vitamin A. The concentration of the latter is almost halved in semi-skimmed milk; the skimmed milk is completely devoid of it.
Vitamin-enriched, concentrated, sweetened and unsweetened milks are commercially available.
Le calcium
Calcium is one of the most abundant chemical elements on Earth. It is the fifth most abundant element in the human body, accounting for 1.9% of body weight (more than one kilogram).
Its role in the formation of bone and teeth is the best known of all, but it is useful to others. mechanisms. These include the transmission of nerve impulses, a role in the contraction (including vascular, thus helping to maintain blood pressure) and in the
blood clotting.
It is a nutrient found mainly in bone (99%) and in a smaller percentage of the total diet. quantity (but indispensable) in the blood. The norm for this blood calcaemia is 2.20 – 2.60mmol/L or 88 – 104 mg/L (8).
To maintain this level in the blood, the body draws on bone reserves if the intake of calcium through diet is insufficient. It is therefore necessary to ensure that you ingest enough of calcium to maintain good bone density.
