Keifer question

[cilla4progress]

Ive been making keifer for about 10 years from organic cow's milk. I know it can even be made with water!

I use pasteurized (not ultra-pasteurized, because you need the bacteria for fermentation). But I know someone who does, and I dont understand how?

Also, why can I only find the pasteurized in gallon jugs, not 1/2, from my local stores?

Thanks in advance!

[Major Nikon]

1. Both are the same in terms of bacteria count

The difference is how it's pasteurized. "ultra" means it's been pasteurized using a very high temperature for a very short period of time. Other methods use lower temperatures and longer periods of time to achieve the same bacteria reduction.

The reason UHT pasteurized milk is generally avoided for fermented dairy products like kefir is because the high temperatures involved denature the whey proteins in ways that interfere with coagulation.

The reason it's hard to find dairy that isn't UHT is because the shelf life is greatly increased. So many dairy manufacturers have pretty much exclusively switched to UHT and non-ultra pasteurized products are becoming much harder to find.

[cilla4progress]

2. Thanks very much -

Appreciate you sharing your knowledge!

Sounds like I should stick with plain pasteurized...though not clear on how coagulation factors in?

[Major Nikon]

3. Has to do with the methods of pasteurization

Pasteurization is a function of temperature AND time. The higher the temperature, the shorter the time needed to achieve the same bacteria reduction.

The old pasteurization method was done in a vat. The milk is heated to around 160F and kept there for 30 minutes. There's several other methods that have been used over the years. UHT heats milk to 280F for 2-3 seconds.

As you can see the difference in temperature is significant, which the reduction in bacteria (effectively sterilized) is the same. So for the sake of bacteria, there isn't a difference. However, protein reacts considerably different at different temperatures. Even for this very short period of time the proteins in the milk will denature in very different ways. You can actually taste the difference. Some people who are more sensitive to tasting the mallard reaction will find UHT milk tastes "cooked".

Fermented milk products kefir, yogurt, etc., rely on coagulation of the milk proteins in order to thicken. If the protein has been denatured at higher temperatures, it will not coagulate as well.

[cilla4progress]

4. Wow - fascinating!

You've taught me so much! Thank you!