Cathy2 wrote:My oven has a bread proofing temperature of 100 degrees. I use this feature for creme fraiche as well as yogurt, especially in winter.
aschie30 wrote:Yup, that's why I posted about putting it in the oven. (I've also made yogurt this way.)
One temperature doesn't fit all when it comes to microorganisms. The bacteria used to make yogurt (
Lactobacillus bulgaricus and
Streptococcus thermophilus) are classified as thermophiles—that is, they like higher temperatures. Those used for cultured buttermilk and crème fraîche (various subspecies of
Lactococcus lactis and sometimes
Leuconostoc mesenteroides) are mesophilc organisms—in other words, they're happiest at medium temperatures. Generally, commercial yogurt is incubated around 110° F and buttermilk around 72° F.
As with
sauerkraut, that's not to say you can't get good results by doing things differently. Yogurt incubated above 110° will favor
Lactobacillus growth, resulting in more acid but less complex flavor; temperatures below 110° favor the
Streptococcus, less acid and more flavors. Similarly for buttermilk (and I assume crème fraîche), temperatures above 72° favor
Lactococcus, thus more acid, less flavor; below 72° favors
Leuconostoc, less acid, more flavor.
aschie30 wrote:After 8 hours on the countertop, it was still runny, so I flipped on the oven and off (no more than ten seconds), and stuck the jar in there for the remainder of the day. (I think my kitchen is too drafty.) The result was nothing short of spectacular: thick, creamy, glistening, and tangy.
In the first 8 hours of this two-step protocol, probably
Leuconostoc was busily churning out the flavor molecules but was unable to produce enough acid to cause the milk proteins to aggregate. When shifted to a higher temperature the
Lactococci took over and made enough acid to cause aggregation of the casein into a gel-like matrix ("thick"). It sounds like you stumbled onto the perfect way to make crème fraîche in your kitchen; the trick may be to do it reproducibly.
aschie30 wrote:Anyway, I didn't up the buttermilk because I thought it would thicken it, I did it for taste. Other versions I've made didn't have enough tanginess for me, so I think I'll keep it at 2 tablespoons buttermilk per cup of heavy cream.
If you incubate at a controlled temperature somewhat over 72° that ought to give you more tang. It's the temperature more than the amount of starter culture that affects the result. It rarely hurts to add a little more starter and it's a good idea to use the freshest buttermilk you can get (the bacteria die off during storage, even in the refrigerator).
Cathy2 wrote:I want to try making cultured butter from the homemade creme fraiche next.
For butter, I would guess that lower incubation temperatures might be preferable. You want more complex flavors but don't want all the fat entrapped in the protein matrix.
Tim wrote:You can also use a range of culturing agents to customize your flavor profile. Yesterday a friend gave me some wonderful creme fraiche that was cultured overnight at room temp with fresh sheep's milk cheese.
It's definitely worth trying different brands of buttermilk, different types of cultured milks or various commercial cultures to find ones that suit you. The microbes used for fresh goat cheese should be very similar to those used for crème fraîche. If you look at the descriptions at
New England Cheesemaking Supply Company you'll see that the types of bacteria are the same in their
chèvre and
crème fraîche cultures:
Lactococcus lactis subsp
lactis,
Lactococcus lactis subsp
cremoris and
Lactococcus lactis subsp
lactis biovar diacetylactis (I assume they accidentally left out "
lactis" as the subspecies for this last bug). It's interesting they don't include any
Leuconostoc species, usually included in buttermilk cultures.
I've made many batches of yogurt and some occasional crème fraîche but wouldn't consider myself to have much practical knowledge. Much of what I summarized above is
textbook information. Sometimes slightly different microorganisms are used than the ones I mentioned. They might have different growth characteristics and temperature optima but I think most of what I wrote is generally true. If nothing else it should provide a rational basis for fiddling with or troubleshooting recipes. Now that I have a controllable water bath I hope to do some fiddling myself.
For an excellent nontechnical introduction to cultured dairy products (with some great recipes) see
Anne Mendelson's Milk: The Surprising Story of Milk Through the Ages. I just started reading it and am quite impressed.