Why is The Temperature Of Milk Important For Your Coffee?

Image of milk foaming

Have you ever been served a coffee and when it touches your lips it feels like you’ve drank lava? Or alternatively, been served a drink which is lukewarm or even cold? The answer is most likely yes, as this has happened to all of us at least once in our lives! The right temperature of milk for your coffee is crucial. Below are a few examples of different temperature milk and how they can effect a cup of coffee.

What Happens When You Heat Milk?

The process of heating milk creates foaming. It involves forcing water vapour and air into the milk whilst applying heat to it. Milk is made up of several compounds with the two most important compounds being vital for the success of the foaming process.

The compounds are protein and fat and the milk contains a mix of whey and casein proteins. When the milk is heated, the structures of the protein displace and creates spheres around the air. This then leads to the creation of bubbles which is the exact texture perfect for coffee. The fat within the milk is responsible for the smooth and rich tasting creaminess that we love from milk. You will get a better quality foam with milks with lower fat quantities.

Effects of Over-Heated Milk

The milk foam is increasingly stabilised by the more heat that I placed onto it, higher temperatures tend to cause denaturing within whey proteins. When over-heating your milk it makes it impossible for you to taste the subtle flavours that occurs from heated milk, and may also burn your mouth during consumption. When milk is heated over 100°C, the lactose within it reacts with proteins and creates a hideous aroma, the fats also become involved in oxidation reactions which in turn ruins the flavour.

Effects of Under-Heated Milk

As well as being over-heated, milk can also be under-heated. If milk is foamed to a temperature between 35-40 °C then it is not useable for coffee. The foam will be really thin and different sized air bubbles will merge together. In lower temperatures, whey proteins have not completed denatured and fats are a mixture of solids and liquids. This means that liquid fats can get into the air bubbles created by the denatured proteins and completely ruin the foam. Heat it perfectly or do not heat it at all. 

What is The Perfect Milk Temperature?

The recommended temperature for the perfect milk in your coffee is around 55–65°C. In this heat, the fats are liquid and will not destroy the foam. The amount of whey protein is ideal for absorption so the foam will maintain stability. At this temperature, the lactose cannot react with the proteins and create undesirable flavours. The best temperature for a sweet tasting coffee is at around 60 °C, this will not detract from the overall flavour of the coffee.

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