Making yogurt - cooler vs sous vide

[seabream]

I made two batches of yogurt, one using a cooler and another one using sous vide. As a starter, I used yogotherm cultures. All the milk was heated and cooled to the same temperature, at the same time, in the same pot (82C and then 42C). The sous vide was set to 42C and the yogurt in the cooler had some towels and hot water bottles around it, and was placed near the fire place. I let both batches of yogurt stay at this temperature for the same amount of time (7 hours or so).

The result was interesting... both batches came out with similar consistency, but the sous vide yogurt was *a lot* more sour than the cooler one. The only difference between the two batches was really the temperature at which they were held.

Sadly, we enjoyed the cooler yogurt much more. I want to like sous vide for making yogurt. I am hoping that once I figure out the ideal temperature and time for our taste, I'll be able to reproduce the results easily (which is a problem I have with the cooler method).

I want to make another batch based on a good plan, but I'm a bit unsure about what to try next. Here's what I'm thinking of trying:

* Reduce the amount of time that I keep the yogurt at the target temperature. I'm assuming that the same enzymes that happily reproduce at warm temperatures also cause sourness, so maybe cutting down on the time will produce less sourness. I'm not so sure this will work because the Modernist Cuisine says to hold the temperature for 8 hours, and I already reduced it to 7 on my first try. Will the yogurt set if I reduce the time further?

* Increase the sous vide temperature to 45C. The Modernist Cuisine says to incubate at 45C - I set it to 42C by mistake. However, some online article that I can no longer find had the temperature range in which yogurt can be made successfully, and both temperatures are within that range. So I'm not so sure that this will make a big difference.

Any information that anyone can share is very welcome!

Thanks in advance!

[inductioncook]

With bread fermentation, many of the more sour bacteria multiply faster at higher temperatures, and you may be the victim of that here.

[DickL]

I make yogurt all the time doing something like your second method. (I don't have a sous vide system.) A number of years ago through trial and error came to the conclusion that starting at 52C, adding the starter (normally about a tablespoon and a half at refrigerator temperature, which of course cools it a little immediately) and then letting it cool slowly in an insulated container worked well. I currently use a round quart container for the yogurt and put it in an ice bucket that provides about an inch of air space around and over the container. It cools to room temperature in a few hours, probably about 6 to 8. As it sits longer, it gets more sour; I've found I like it best after about 48 hours from starting (give or take a few hours).

BTW, for starter I use a 50/50 blend of two commercial yogurts, Trader Joe's European Style Plain Whole Milk yogurt and ömür whole milk yogurt (Kaymakli Tam Yagli), neither of which has anything beyond milk and starter in it. I mix the two and freeze the blend in small containers which will make about four batches each. Using this starter gives me consistent results.

For the milk component, I use skim milk (or sometimes 1%, depending what's on sale) enriched with some dry milk (1/4 or 1/3 cup per quart, depending on the type of dry milk).

The result is nicely firm, but when stirred becomes creamy. Quite a bit different from your approach, but it works for me.

[andiesenji]

In my experience with making yogurt for the past fifty years or so, your incubation temperature is too high.

The optimal temp for the best flavor is between 85 - 100° F. (30 to 37° C.)

There are multiple strains of bacteria that contribute to the development of the yogurt consistency and flavor and getting the correct balance is most important.

I have different types of yogurt makers. The electrics maintain the same temp throughout the incubation period, about 95 degrees F.

The insulated types start out at about 100° F., and the temp gradually drops over the 12 hours I usually leave it to incubate. The flavor is consistent with both methods, the texture depends on the type of milk used.

If you use light cream (half & half here in the US) you will get a product as thick as Greek yogurt - no straining required.

If you use heavy cream, you will get a result similar to clotted cream, perfect for spreading on toast, split scones, date-nut bread or ??

[seabream]

Thank you for the replies!

I will try lowering the sous vide temperature, and I will experiment with new starters.