Why do we choose Evaporated Milk?

Evaporated milk.

Evaporated milk is known as homogenized milk in which 60% of the water has been removed. In a more detail explanation, evaporated milk is the milk which has concentrated to one-half or less of its original bulk by evaporation under high pressures and temperatures. It contains a specified amount of milk fat and solids. After the milk has undergone a series of processing steps, the final product as evaporated milk is canned. Since evaporation process eliminate most of the water which create favourable condition need for rapid growth of microorganisms, hence it is shelf-stable canned milk product.

Is it similar as condensed milk?

Evaporated milk and sweetened condensed milk.

People are likely to confused between evaporated milk and sweetened condensed milk. In fact, it itself is condensed milk, but unsweetened. However, sweetened condensed milk may undergo the similar process as evaporated milk, just that the major differences between them is that sweetened condensed milk is added with sugar. Evaporated milk has similar texture with skim milk while sweetened condensed sugar is more viscous due to the addition of sugar. Although both have similarities in some aspect, evaporated and condensed milk cannot be used interchangeably as the taste and texture would be different. Evaporated milk has bland taste while sweetened condensed milk is very sweet.

Nutritional value

There are skim, low-fat, and whole milk varieties of evaporated milk from which approximately 60% of the moisture has been removed. It must contain no less than 7.5% milk fat and 25% milk solids-non-fat (MSNF) if whole milk was the raw material. Evaporated milk from low-fat milk must contain no more than 4% milk fat and 20-24% MSNF. Evaporated skimmed milk must contain no less than 17 percent MSNF and no more than 0.3 percent of fat. The milk solid-non-fat stated above contain the lactose, caseins, whey proteins, and minerals (ash content). Evaporated milk may contain permitted stabilizer which are usually the stabilizing salts such as sodium citrate, disodium phosphate or calcium chloride to maintain its viscosity during the storage period. Sodium ascorbate may be present as a preservative. Fortification of vitamins A, D and C is allowed.

Composition of milk fat and milk solid-non-fat in different types of evaporated milk.

Types of evaporated milk	Milk fat (%)	Milk solids (%)
Full cream	>7.5	>25
Low-fat	<4	20-24
Skimmed	<0.3	>17

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Typical Composition for Whole Evaporated Milk

Composition	Percentage (%)
Moisture	75.0
Fat	7.5
Lactose	9.5
Protein	6.5
Ash	1.5

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How evaporated milk is made?

The raw milk is first transported from the dairy farm to the plant in refrigerated tank trucks. At the plant, the milk is first tested for odour, taste, bacteria, sediment, and the composition of milk protein and milk fat. The composition of protein and fat is measured by passing the milk under highly sensitive infrared lights.

Flow chart of processing evaporated milk.

After the certain requirements are reached, the warm milk is piped to an evaporator for vacuum evaporation. Water is evaporated by means of indirect heating whereby product and heating medium (steam) are kept separated from one another by using a sheet of steel. In the evaporator, the milk is subjected to a pressure of 160-320 hPa and temperature of 55–70 °C. Since the milk is subjected to a pressure lower than atmospheric pressure, thus the boiling point of the milk is lowered to 40-45°C. As a result, most water is removed from the milk until it is concentrated to 30-40% solids. Hence, the viscosity of the milk is increased as there is less interaction between water molecules and milk fat and milk solids. The flow rate of the liquid is decreased.

Illustration of milk evaporator.

Next, the milk is chilled to 4°C before proceeding to homogenization step. The milk is then homogenized by forcing it under high pressure through tiny holes. This breaks down the fat globules into very small particles which helps to improve its colour. Besides, separation is also prevented to enhance stability of the emulsion.

Then, pre-measured amounts of a stabilizing salt, such as potassium phosphate, are added to the milk to make it smooth and creamy. Stabilizing is important to maintain the viscosity of the milk by preventing coagulation and curd formation which are undesirable caused by high temperature of heat treatment afterwards. Slight change in salt equilibrium of milk, induces significant change in structure and functional properties of casein micelles. If a coagulum of milk protein is formed, the aggregated micelles are dispersible by stabilizing salt. This stabilization causes the colour of the milk to turn a pale tan.

Milk is then passed under a series of ultraviolet lights for fortification of vitamins D. For the packing of evaporated milk, tin is usually used for canning as it resists high temperature during sterilisation. The milk is piped into pre-sterilized cans that are immediately vacuum-seal.

Finally, the canned evaporated milk is commercially sterilized at 115-118 °C for 15 minutes. In this process, Maillard reaction occurs where a slightly caramelized flavour is induced, and it is slightly darker in colour than fresh milk due to chemical reaction between protein and lactose. Immediately after sterilization of evaporated milk, it is cooled down quickly to ensure its safety and quality. Finally, a dense, creamy, ultra-concentrated canned evaporated milk which is sterilised is completed and can be stored for several months.

After the series of processing steps, evaporated milk should be stored in low temperature to ensure its quality. Low temperature storage (0-7°C) prevents sediment formation caused by the settling out of calcium and magnesium salts. If the storage temperature is too high, the milk colour becomes brownish and the pH decreases. Discolouration is rapid if the storage temperature is above 32°C. However, if the storage temperature is too low, protein will precipitate. Storage at freezing temperature will only cause the change in the texture of the product.

Easy steps to make evaporated milk at home!

Why evaporated milk?

Evaporated milk lost about half of the water and this reduce the favourable condition required for the growth of microorganisms. Commercial evaporated milk is shelf-stable and stays fresh for up to two years if held at a temperature of 0-16°C. It often used as a substitute for fresh milk as it has much longer shelf-life. Some people choose evaporated milk rather than sweetened condensed milk due to its mild flavour as it is unsweetened. If you don’t prefer too much sweetness, you may choose evaporated milk!

Reference

1. D. D. Muir (2011), Food and Beverage Stability and Shelf Life, The stability and shelf life of milk and milk products (Pp 755–778).
2.  H.J. Hess (2003), Encyclopedia of Food Sciences and Nutrition (Second Edition), Condensed Milk (Pp 1574-1581).
3. https://www.chowhound.com/food-news/186862/what-is-the-difference-between-evaporated-milk-and-condensed-milk/
4. http://dairyprocessinghandbook.com/chapter/evaporators
5. http://www.madehow.com/Volume-6/Evaporated-and-Condensed-Milk.html