Background
Evaporated and condensed milk are two types of concentrated milk from which the water has been removed. Evaporated milk is milk concentrated to one-half or less of its original bulk by evaporation under high pressure and temperature, without the addition of sugar, and usually contains a specified amount of milk fat and solids. This gives regular evaporated milk—depending on its fat content—a shelf life of up to 15 months.
Condensed milk is essentially evaporated milk with sugar added. The milk is then canned for consumer use and commercial applications such as baking, ice cream processing, and confectionery manufacture. This product typically has a shelf life of around two years. When concentrated milk was first developed in the mid-1800s, before the advent of refrigeration, many people used it as a beverage. However, except for some tropical regions, this is rarely the case today.
History
In 1852, a young dairy farmer named Gail Borden was on a ship returning to the United States from the Great Exhibition in London. When rough seas made the cows on board seasick and unable to be milked, infant passengers began to go hungry. Borden wondered how milk could be processed and packaged so that it would not spoil. This was a problem not only on long ocean voyages but also on land, as milk was then shipped in unsanitary oak barrels and spoiled quickly.
When Borden returned home, he began experimenting with raw milk, determining that it was 87% water. By boiling the water off the top of the milk in an airtight pan, Borden eventually obtained condensed milk that resisted spoilage. On a later trip by train to Washington, D.C. to apply for a patent for his new product, Borden met Jeremiah Milbank, a wealthy grocery wholesaler. Milbank was impressed with Borden’s ideas and agreed to finance a condensed milk operation. In 1864, the first Eagle Brand Consolidated Milk production plant opened on the east branch of the Croton River in southeastern New York.
Borden’s new product was not an immediate success. In 1856, condensed milk was blamed for an outbreak of rickets in working-class children because it was made with skimmed milk, and therefore lacked fats and other nutrients. Others complained about its appearance and taste because they were accustomed to milk with a higher water content that had often been whitened with chalk. Despite this criticism, the idea of condensed milk caught on, and Borden began to license other factories to produce it under his name.
The outbreak of the American Civil War proved beneficial for business when the Union Army ordered condensed milk for its field rations. At the height of the war, Borden’s Elgin, Illinois plant was producing 300,000 gallons of condensed milk annually.
To differentiate his own product from that of the licensed plants, Borden rebranded his condensed milk as Eagle Brand. Around this time, two American brothers, Charles A. and George H. Page, founded the Anglo-Swiss Condensed Milk Company in Switzerland. One of their employees, John Baptist Meyenberg, suggested eliminating the added sugar to produce evaporated milk. Meyenberg’s idea was rejected, so he emigrated to the United States and, by 1885, was producing the first commercial brand of evaporated milk at his Highland Park, Illinois plant, the Helvetica Milk Condensing Company.
In the late 1880s, Eldridge Amos Stuart, a grocer in El Paso, Texas, noted that milk was spoiling in the heat and causing illness in children. Stuart developed a method for processing canned, sterilised evaporated milk. In 1899, Stuart partnered with Meyenberg to supply Klondike gold miners with evaporated milk in 16-ounce cans.
An article on homogenisation in the 16 April 1904 issue of Scientific American influenced the concentrated milk industry, which adopted the process long before fresh milk plants did. Further improvements followed. In 1934, Meyenberg’s company—now headquartered in St. Louis, Missouri, and renamed the Pet Milk Company—became the first to fortify its evaporated milk with Vitamin D. This was achieved through irradiation, a process developed in 1923 by Harry Steenbock, a chemist at the University of Wisconsin. In this method, milk is exposed to ultraviolet light, producing reactions that generate Vitamin D and enrich the milk.
Raw Materials
The primary ingredient is raw cow’s milk, purchased from nearby dairy farms.
A salt such as potassium phosphate is used as a stabilising agent to prevent the milk from breaking down during processing. Carrageenan, a food additive derived from red algae (Irish moss), is used as a suspending agent. The milk is also fortified with Vitamin D through exposure to ultraviolet light. Powdered lactose crystals are added to concentrated milk to stimulate lactose production—a sugar that increases shelf life.
The Manufacturing Process
Evaporated Milk
The raw milk is transported from the dairy farm to the plant in refrigerated tankers. At the plant, the milk is tested for odour, taste, bacteria, sediment, and the composition of milk protein and fat. The composition is measured by passing the milk under highly sensitive infrared lights.
The milk is filtered and passed into pasteurisers, where it is quickly heated using one of two methods:
High-Temperature Short Time (HTST) – the milk is heated to 161°F (71.6°C) for 15 seconds.
Ultra-High Temperature (UHT) – the milk is heated to 280°F (138°C) for two seconds.
Both methods improve milk stability, reduce bacterial content, and prevent coagulation during storage.
The warm milk is then transferred to an evaporator. Through vacuum evaporation (exposing the milk to a pressure lower than atmospheric pressure), the boiling point is lowered to 104–113°F (40–45°C), concentrating the milk to 30–40% solids while maintaining minimal cooked flavour.
The milk is subsequently homogenised by forcing it under high pressure through small openings. This breaks down fat globules into fine particles, improving colour and stability.
Pre-measured amounts of a stabilising salt such as potassium phosphate are added to make the milk smooth and creamy, giving it a pale tan colour. The milk is then passed under ultraviolet light to fortify it with Vitamin D before being piped into pre-sterilised cans and vacuum-sealed.
Condensed Milk
The milk is flash-heated to approximately 185°F (85°C) for several seconds and then transferred to the evaporator where the water is removed.
Under vacuum pressure, the milk is concentrated until it reaches 30–40% solids and acquires a syrup-like consistency. It is then cooled and inoculated with around 40% powdered lactose crystals, which are agitated to stimulate crystallisation. The added sugar preserves the condensed milk.
Finally, the milk is piped into sterilised cans and vacuum-sealed.
Quality Control
The milk industry is subject to strict regional and federal regulations governing bacterial prevention and the composition of solids and fats.
According to the United States Food and Drug Administration (FDA):
Sweetened condensed milk must contain at least 28% total milk solids and 8% milk fat by weight.
Evaporated milk must contain at least 6.5% milk fat, 16.5% non-fat milk solids, and a total of at least 23% milk solids.
Evaporated milk must also contain 25 International Units (IUs) of Vitamin D.
The milk is taste-tested for freshness both at the dairy farm and upon arrival at the processing plant. Once in the plant, the milk is not handled directly, moving through a closed system of pipes, vats, and automated machinery. At least one-third of labour time in the milk industry is devoted to cleaning and sterilising utensils and equipment. Milk inspectors conduct regular inspections to ensure compliance and hygiene standards.