Evaporated milk is a type of concentrated milk product that has had about 60% of its water content removed. It differs from sweetened condensed milk, which has added sugar. When evaporated milk is heated, a chemical reaction called the Maillard reaction occurs, causing the milk to take on a tan or brown color.
What is Evaporated Milk?
Evaporated milk begins as regular pasteurized cow’s milk. It then goes through a process called evaporation to remove roughly 60% of the water content. The resulting product is a thick, creamy milk containing all the proteins, vitamins, and minerals found in fresh milk, just in a more concentrated form.
The purpose of evaporating the majority of water is to increase the product’s shelf life. By removing water, the growth of bacteria is inhibited, allowing evaporated milk to be stored unrefrigerated. Once opened, evaporated milk must be stored in the refrigerator.
Composition of Evaporated Milk
The makeup of evaporated milk is:
- 60% less water than fresh milk
- Higher protein content – minimum of 6.5% rather than 3.5%
- Higher calcium content – at least 30% of the daily recommended amount per cup
- Slightly caramelized due to heat processing
- Vitamin D added to replace what is lost during evaporation
The process of evaporation gives evaporated milk a light golden hue and slightly cooked flavor even before it is heated further. The color and flavor become more pronounced when the product is used for cooking or baking.
How is Evaporated Milk Made?
Evaporated milk is produced by heating fresh milk to around 190°F (88°C) under vacuum conditions. The vacuum atmosphere allows the water to boil off at a lower temperature. Almost 60% of the water evaporates away over the course of about 30 minutes.
Once the desired amount of concentration is reached, the milk is rapidly cooled to halt the evaporation process. At this point, vitamin D is added to replace what was lost during evaporation. Finally, the milk is packaged into cans or cartons and sterilized at high heat to kill any remaining bacteria.
Why Does Evaporated Milk Brown When Heated?
Heating evaporated milk causes it to take on a tan or light brown color through a process called the Maillard reaction. This is a chemical reaction that occurs between amino acids and reducing sugars at high temperatures.
As the proteins and lactose sugars in milk are exposed to heat, they break down. The amino groups from proteins and carbonyl groups from sugars react, forming glycosylamine complexes that then rearrange into Amadori compounds. These intermediate products continue reacting to produce molecules that impart new color, aroma, and flavor.
The end result is the characteristic brown color and rich, nutty flavor associated with heated milk products like evaporated milk. The Maillard reaction is responsible for many of the distinctive flavors in roasted and grilled foods.
Factors Influencing Browning
Several factors impact the extent of Maillard browning when evaporated milk is heated:
- Temperature – Higher heat causes more rapid and extensive Maillard reactions.
- Acidity – Increased acidity accelerates browning.
- Water content – Evaporated milk browns faster than regular milk due to lower water content.
- Heating mechanism – Boiling causes more browning compared to gentler heating.
- Heating duration – The longer evaporated milk is boiled, the darker the color.
For these reasons, evaporated milk used in recipes like fudge and caramel will take on a much darker color than milk simply warmed on the stovetop or in the microwave.
Browning Differences Between Evaporated & Condensed Milk
Evaporated and condensed milk are two canned milk products. While similar in some ways, they brown differently when heated due to a couple factors:
- Sugar content – Condensed milk contains added sugar, which participates in Maillard reactions and accelerates browning. Evaporated milk has no added sugars.
- Heating process – Condensed milk is sterilized at lower temperatures than evaporated milk, resulting in less initial browning.
For these reasons, condensed milk generally browns faster and darker when heated compared to evaporated milk. The added sugar leads to increased Maillard reactions, while the lighter initial color means more browning can occur before reaching the maximum brown hue.
Is Browning Harmful?
The Maillard reaction produces hundreds of different flavor compounds and melanoidin pigments that give browned food its characteristic colors. While this chemical process can decrease the availability of certain amino acids, the browning is not harmful or an indicator of spoiled milk.
The U.S. Food and Drug Administration (FDA) has approved caramel coloring produced through Maillard reactions for use in food. Caramel coloring is made by heating carbohydrates like glucose and sucrose. In a similar fashion, the browning of evaporated milk during heating is not a health concern.
Uses for Heated Evaporated Milk
Here are some common uses for evaporated milk that is browned through heating:
- Coffee creamer
- Hot chocolate
- Smoothing gravies and sauces
- Sweetened condensed milk
- Dulce de leche
- Fudge
- Caramel
- Pumpkin pie
- Candies
- Custards
In recipes like these, the rich nuttiness and brown hue from the Maillard reaction adds desirable flavor and appearance. The browning also thickens and enhances the flavor of the evaporated milk itself.
Preventing Unwanted Browning
Sometimes browned evaporated milk is not the goal, like when using it as an ingredient in white sauces or cream soups. Here are some tips to prevent excess browning:
- Use low to medium heat when warming evaporated milk.
- Warm evaporated milk in a double boiler or heat proof bowl rather than directly in a pan.
- Add a pinch of baking soda to the milk – this increases pH and slows the Maillard reaction.
- Warm evaporated milk in short bursts, cooling in between.
- Add evaporated milk at the end when using in recipes.
Storing Evaporated Milk
Unopened evaporated milk has a shelf life of 6 to 12 months when stored at room temperature. Once opened, it should be refrigerated and used within 5 to 7 days.
If evaporated milk has browned slightly during the heating process, it should be safe to consume if used right away. Severely browned milk may indicate overheating and a loss of nutrients, so it’s better to discard it.
Properly stored and handled evaporated milk will maintain its quality and flavor. Refrigeration prevents unwanted spoilage and browning during storage.
The Chemistry Behind Evaporated Milk’s Browning
To summarize, here are the key points about the chemistry that causes evaporated milk to brown when heated:
- Heating causes Maillard reactions between proteins and sugars.
- Amino groups and carbonyl groups form glycosylamines and Amadori compounds.
- These intermediate products rearrange to form brown melanoidin pigments.
- Hundreds of flavor compounds are also generated, giving a nutty, roasted flavor.
- Increased temperature, acidity, and concentration accelerate Maillard reactions.
- The browning indicates a complex cascade of chemical changes, not spoilage.
Through this fascinating process, simple milk ingredients transform into a multitude of new aromatic and flavorful compounds that provide the characteristic color and taste of evaporated milk when it’s heated or used in cooking.
Conclusion
When evaporated milk is heated, it takes on a tan or brown hue through the Maillard reaction. This occurs between the proteins and sugars in milk. The same chemical reaction is responsible for the satisfying flavors of roasted meats, baked goods, and other cooked foods.
While fresh milk is about 87% water, evaporated milk has about 60% of its water content removed. This makes it more prone to browning when heated. The brown color is not an indication of spoilage, but rather a complex cascade of chemical changes during cooking.
Browning can be minimized or encouraged through different heating techniques to achieve the desired results in various recipes. Overall, the Maillard reaction provides evaporated milk with a richer, nuttier flavor and darker color that enhances many popular dishes.
