Skimmed – Milk from which almost all the fat has been removed is known as skimmed milk. However, a small fraction of the fat, about 0.1% is almost impossible to remove by the standard method using a centrifugal separator. Skimmed milk should never be used to feed babies as the fat-soluble vitamins have been removed with the fat. Skimmed milk and semi-skimmed milk have become popular with consumers because they are healthier.
Examination – pale colour, watery, thin consistency, no cream line and a weak flavour.
Packaging - Plastic carton with red top and label.
Nutritional value – Protein – 3.4g
Fat – 0.1g
Calcium – 124mg
Uses – Used for drinking (especially by people on low fat diets) and in some cases can replace eggs in baked goods.
Semi Skimmed Milk – This milk is also pasteurised and so goes though the same process as skimmed milk. The difference is that semi- skimmed milk does have all it’s fat taken away. Semi-skimmed milk by law has to contain 1.5-1.8 per cent fat.
Examination – white, no smell, thin consistency although thicker than skimmed milk, slight cream line, blander than whole milk, and not as creamy as whole milk.
Packaging – Plastic carton with green top and label.
Nutritional value – Protein-
Fat-
Calcium-
Uses – Used for drinking and in some cases can replace eggs in baked goods.
Whole milk – This milk is also pasteurised but this milk by law must contain at least 3% fat.
Examination – White (darker), smells creamy, has a cream line, medium consistency not as thin as semi skimmed and creamy flavour.
Packaging – plastic carton with blue top and label.
Nutritional value – protein – 3.2g
Fat – 4g
Calcium – 119mg
Uses – Used for drinking and in some cases can replace eggs in baked goods.
Whole Goats Milk – this milk is from goats but is still pasteurised. It has a higher percentage of fat.
Examination - A rich white colour, thicker consistency than the others, strong and creamy.
Packaging – Cardboard carton, red/blue.
Nutritional Value – protein – 2.8g
Fat – 3.6g
Calcium - 120mg
Jersey And Guernsey Milk – This milk is made from different breeds of cows (Jersey and Guernsey) to ‘ordinary’ milk. It contains a higher proportion of fat than ‘ordinary’ milk an average 4.8%, by law it must contain at least 4%.
Examination – thick, creamy, has a cream line, strong but pleasant flavour.
Packaging – plastic carton with a gold top.
Nutritional value – protein - 3.4g
Fat – 5.2g
Calcium – 134mg
Organic Whole Milk - Organic whole milk is processed in the same way as ordinary whole milk but organic milk has no added additives. It is from cows, which have been reared on grass (which has had no treatment) only.
Examination – darker cream colour, creamy flavour and sweet smell.
Packaging – cardboard carton with a light blue and white label.
Nutritional Value – Protein – 3.2g
Fat – 4g
Concentrated Milks.
Water can readily be removed from milk by evaporation. Products were made for many years by this method, but all had a marked ‘cooked milk flavour’. The advent of the evaporator working under a strong vacuum enabled the concentration to be undertaken at a lower temperature, thus reducing the heat damage, for example at 50°C.
Evaporated milk – this is made by evaporating water from milk to reduce the water content to about 70%. The product sometimes has a poor granular texture, which can be improved by adding either sodium citrate, disodium phosphate or calcium chloride. The product is still highly perishable and has to be homogenised, then sealed into cans and heat process in retorts at 121°C for about 15 minutes, depend on the can size.
Examination – sweet, creamy, sugary and has a cream line.
Packaging – in a tin, red label with a little blue and white.
Nutritional value – Protein – 8.2g
Fat – 9g
Calcium - 300mg
Condensed Milk- this is a similar product to evaporated milk, but is sweetened, and in fact depends on its sugar content for preservation. Milk must first be pasteurised, as the product is not heat processed, but it is not cooled as it passes directly to the evaporator. A sugar syrup (60-65% sucrose) is added to the evaporator and the whole milk is concentrated under vacuum at 50-55°C. The product is then cooled and agitated at the same time. Often very small crystals of lactose are added to ensure rapid crystallization of the lactose. The addition of the large amount of sucrose forces lactose, less soluble than sucrose, out of solution. If the lactose is allowed to crystallize slowly it produces large crystals, sometimes as big as marbles. Agitation ad seeing with small crystals ensures small lactose crystals, which are unnoticed in the product. The product is poured into sterilized cans and sealed without further preservation and therefore careful hygiene is needed during this process.
Examination – Yellow, brown colour, very thick consistency, sweet, sticky flavour.
Packaging – In a tin with blue and white label.
Nutritional value – Protein – 10.5g
Fat – 0.2g
Uses – Used in chocolate and confectionery.
Sterilization.
For sterilization, milk is first preheated to around 50°C, separated and standardized to produce either standardized whole milk, semi-skimmed or skimmed milk, homogenized and filled into bottles, which are closed with a hermetic seal.
There is no legally defined process for sterilizing milk but, commonly, filled bottles are carried on a conveyor belt through a steam pressure chamber and emerge after 10 to 30 minutes having been subjected to temperatures of between 110°C and 130°C. Cooling takes place using a cold water tank, sprays or, in some cases, atmospheric air. The bottles are then packed into crates. For in-container sterilization processes the milk is typically heated to temperatures of 110 to 120°C for 10 to 30 minutes.
‘UHT’ Semi-skimmed milk.
UHT stands for ultra high temperatures. It is produced by the method above but this caused an overall reduction in the nutritive value of milk. The vitamins are badly affected in that vitamin C content is halved, B12 is destroyed and one third of thiamin is lost. The biological value of the proteins is reduced.
Examination – Creamy yellow, sulphur smell and strong flavour.
Packaging – Cardboard carton with green and white labels.
Nutritional value - Protein – 3.4g
Fat – 1.7g
Calcium – 122mg
Uses – Can be kept longer so probably used by manufacturers in products.
Conclusion.
I have found that the way in which the milk is process determines the milk qualities. For example, whole milk has a creamy flavour and texture as it has only been pasteurised but the sterilised milk has had a much more severe heat process and as a result has a strong cooked milk flavour. I have also found out that vitamins are destroyed where there is a lot of processing but in evaporated milk there is a lot of calcium, which is probably added by the manufacturer. Also other nutrients are destroyed with the more severe processing for example the protein is halved in UHT milk.
The type of milk produced depends on the animal and breed it is taken from because the goats milk was very different form the cows milk and depending on what breed the cows were the protein, fat and calcium amount in the milk varied.
