Permeate is made when milk is filtered through a fine 'sieve' or membrane using a technique called ultrafiltration. It may later be added back into milk to ensure consistent levels of fat and protein.

The level of naturally occurring fat and protein in milk can vary depending on several factors, including the season, the stage of lactation, and what cows have been fed.

Ultrafiltration is one way to standardise the protein and fat content in milk right throughout the year. This process separates the lactose, vitamins and the minerals (collectively called permeate) from the milk protein and fat. 

Milk manufacturers may add permeate back to cow’s milk to reach the desired nutrient levels. Some manufacturers choose not to do so and advertise their milk as ‘permeate free’.  

There are no permeate-free dairies, as it is a process undertaken by manufacturers. However, if you are looking for milk without permeate, check the packaging and nutritional information of milk products at the supermarket.