Inside Fen Farm Dairy: How we test our raw milk

Raw milk testing

It’s all very well us telling you that our raw milk is safe to drink, but how do we know this is true? Each day we carry out laboratory standard tests straight after milking. Read on to find out how we do it.

The process

We take a 1ml sample of the milk and drop it onto the centre of the petrifilm plate. We then place the petrifilm in an incubator for 14 hours before reading the result.

What are we testing?

Using this process we are measuring the number of coliforms present in the milk sample.

Raw milk coliform test

This image shows the petrifilm after testing is complete. It shows a count of 5 coliforms (you only count the dots that have a gas bubble around them.)


The milk we tested on the day these photos were taken contained 5 counts of coliforms and on average, our daily reading is lower than 3 counts. The FSA limit and legal limit for raw milk is 100 counts of coliforms. To put these results into context, our reading is well below the legal limit for pasteurised milk, which is 10 counts.

We are proud that our efforts to produce safe and delicious raw milk mean we are producing raw milk that conforms even to pasteurised standards. 

To find out how we do this, watch our raw milk video where Jonny talks us through each of the 7 steps we take here at Fen Farm to produce raw milk of the highest standard, from herd welfare through to hygiene in the milking parlour.