As mentioned in my other post on the types of milk you can use to make kefir, fresh milk or pasteurized milk is milk which has been heated to around 70 degrees celsius. UHT milk is subjected to even higher temperatures at 135 degrees celsius (275 degrees fahrenheit) for about 1 to 2 seconds to kill off any undesirable microbes.
This post is kind of lengthy so I’ve broken it up into a few sections:
- Is UHT milk really that bad?
- One-time comparison of UHT and Fresh Milk
- Other considerations / stuff to try in the future
Is UHT milk really that bad?
I’ve seen claims that UHT milk is too dead to support live cultures. This is completely untrue. You can make kefir and yogurt with UHT milk and I’ve done both successfully. Contrary to claims that yogurt or kefir cannot be made in UHT milk, the cultures in both might even do better without the competition from other microorganisms.
There are also concerns about the digestibility of and nutrient loss in UHT milk due to the high temperatures. For the former, the research seems to go both ways. Some support the idea that UHT milk is less digestible1. Others say there are no differences or that UHT milk is even more digestible compared to non-UHT234. For the second issue, it seems generally agreed that there is some nutrient loss in UHT milk24
I wonder if digestibility of UHT milk itself matters if you’re using it to make kefir since the fermentation process improves digestibility. However, because the nutrient content of kefir largely depends on what you used to make it with, I’m not too keen on using UHT milk most of the time even though it’s much cheaper.
Of course, if UHT milk is the only viable source of milk you can get for your kefir, I would say it’s better than not getting any at all. Although I usually use pasteurized goat’s milk, I do have UHT milk stocked up in case I run out of the former.
To bring this section to a conclusion, UHT milk can be made into kefir. However, it is probably not so great if you’re drinking UHT milk on its own. If made into kefir, I think the benefits outweigh the costs especially if UHT milk is the only type of milk you can get.
A one-time comparison of UHT milk and fresh milk
I’ve always known that UHT milk and fresh milk tastes different, but what about the kefir they make? My impression was that UHT milk made a thicker kefir but I’ve never noticed a difference in taste. The other day, I decided to do a side-by-side comparison.
I split the kefir grains into two parts and put them in equal amounts of fresh cow milk or UHT cow milk. Put a different colored cap on and labelled them too just in case I forgot which was which:
Left them in a dark cupboard and this was what I got after a day (UHT milk on the left and fresh milk on the right):
- On first look, there was no difference between the UHT milk and fresh milk.
- The caps were made with rubber or some kind of flexible plastic and frequently pop off the glass during fermentation. The one with the UHT milk popped off first. But since this is a one-time thing, it’s not quite enough to make a conclusion.
- While straining the kefir, I noticed the one made with UHT milk was slightly thicker as usual.
- There was no difference in smell or taste
By the way, I had a backup made with pasteurized goat’s milk and this was what it looked like. Notice the air bubbles in the goat milk kefir have all burst and left tiny holes on the surface while the ones in the cow milk kefir are just forming huge bubbles on the surface.
First, this was only a one-off comparison so I’m wondering if I might have found differences that I weren’t able to see if I had done it over a period of time
- Would the kefir grains have grown faster/bigger/smaller in one type of milk?
- Do different brands of UHT milk give different results?
- Would there have been a difference if I had used more milk? (Maybe they tasted the same because I used too little and both were completely fermented)
I’m interested in answering these questions and when I find the time, I’ll do this properly and link them up in a series of posts or something.
Also, I was thinking of sticking to one type of milk for a period of time and recording stuff such as any symptoms of lactose intolerance, differences in how I felt, or whatever else. I could probably find out if UHT milk or fresh milk was better (for me at least). But I have no idea how to go about doing this properly or even what exactly I should be recording…yet.
Finally, if you have any comments, suggestions on how to improve this post, or anything else, I’ll really appreciate it if you could leave a comment or email me at hello[at]kefirblog[dot]com. Thank you for reading!
- Composition and calcium status of acid whey from pasteurized, UHT-treated and in-bottle sterilized milk [↩]
- Dairy processing handbook chapter 9 p. 220 – 221 [↩] [↩]
- Peptic digestibility of proteins in different heat-treated commercial cow’s milks [↩]
- Effect of UHT treatment on the milk nutrients [↩] [↩]