One of the biggest questions asked for those starting out is - Can you use milk straight out of the fridge or does it need to be warm / room temperature?
The short answer is that YES you can definitely use milk directly out of the fridge when making milk kefir.
Most people use milk directly out of the fridge as it is much more convenient and works well.
However a few people do warm up the milk to room temperature before making kefir.
There are 3 different ways to bring milk to room temperature for kefir
- Gently heat the milk on the stove until slightly warm or until its temperature is about room temperature.
- Let the milk sit out for hour or so until its naturally warmed up
- Lightly boil or pasteurize the milk and then let it cool down to room temperature.
The first method is the best in my opinion. Warm it up quickly and gently without pasteurizing it and without adding excess spoilage bacteria. It may still create more spoilage bacteria, but not as much as the 2nd method.
Letting the milk sit out until its at room temperature is not ideal as it can add excessive spoilage bacteria which may cause imbalances or bad tasting kefir.
Pasteurizing is not necessary, nor is it ideal. The more its pasteurized, the more sterile it becomes. That’s okay when making yogurt as it helps the weaker yogurt bacteria thrive better. With kefir that’s not necessary. Kefir grains have adapted to handle raw milk just fine with all that raw bacteria and enzymes fully intact.There’s no need to further pasteurize it.
However, there are some minor differences between kefir that is made with cold milk and kefir that is made with room temperature milk...
Traditionally, milk kefir was most likely made with fresh room temperature raw milk as they obviously did not have refrigeration. They did not warm up the milk, pasteurize or cook it in anyway. They simply used room temperature raw milk.
We’ve tasted the difference between cold milk and heated milk to room temperature and the taste after 24 hours is essentially the same under most conditions. It’s virtually indistinguishable.
When we tested, the grains with the warm milk did have a little more whey. It wasn’t too significant though and the impact was limited.
Jar on the left was from cold milk. Jar on the right was warmed up milk.
When we tested, we did notice a little more growth in the milk that was warmed up to room temperature. Anecdotally, other people have experience more growth as well. Perhaps the shock of the cold milk does stall the growth a little.
No significant difference either. When we did our test, the thickness was very similar. If anything, the kefir made from cold milk was slightly thicker. This was likely due to it having a little less whey.
Yes, you can use milk directly out of the fridge and most people do that method when making kefir. However, there is some evidence to suggest that the cold milk does shock the grains a bit and may slow grain growth. Within 24 hours, they do recover and there's very little difference in flavor or thickness.
Warming up the milk may slightly help grain growth, but on the down side, it may cause more spoilage bacteria issues or make the milk become more sterile with pasteurization. So in the end, its probably not worth it unless you are looking to optimize growth rate.