Making clabber for cheese starter culture

[EschatonNow]

Hello all,

I'm trying to clabber some local raw (cow's) milk for use as a mesophilic starter culture in cheesemaking. These have been my primary resources:

[1] http://cheeseforum.org/forum/index.php/topic,1927.msg14236.html#msg14236
[2] http://cheeseforum.org/forum/index.php/topic,7222.msg51651.html#msg51651
[3] https://familycow.proboards.com/post/141239/thread
[4] https://www.cheese-in-the-city.com/2019/06/14/make-your-own-clabber.html

In general, what should I look for in a clabber to know it'll make a healthy starter culture for delicious and well-ripened cheeses? (I'm not relying on it to coagulate my milk, since I'm happy using rennet.)

In particular, I'm already 11 days (5 or 6 generations) into my first attempt at clabber and was hoping you might be able to offer feedback on my process/product:

• The milk was purchased chilled from a local dairy (milked that day), so I placed it in a water bath to bring it up to temperature after skimming it as well as I could.
• From source [2] above, it seemed that keeping the milk around 100F would help to select for the strains I want, so I've been keeping it in an oven that I occasionally bump up to keep it between 80 and 100 degrees (my kitchen is around 67F). That being said, it sometimes drops to 70F overnight, and it once got scorched when my housemate preheated the oven before removing my clabber! I was using a half-gallon jar at the time and it was only 3m before he realized his mistake, so I doubt the milk was warmed through, but the oven temperature reached the 150s before the clabber was rescued.
• Some have said they never clabber milk in their kitchen, to avoid cross-contamination, so for the first three generations (when I figured the culture was more vulnerable) I was opening and feeding it outside before moving it back to the oven.
• I keep it in mason jars banded with paper towels.
• I've been feeding it with bottled, pasteurized milk that, for any given feeding, hasn't been opened for more than a few days and is barely allowed outside the fridge. To feed it, I whisk together the clabber and pour off everything but a little bit (around a quarter cup per pint) before topping it off again with milk.
• The first batch of raw milk took about 4 or 5 days to sour and thicken. The next generation took a couple days, and every one since has taken a single day (or less) to thicken.
• After the first batch thickened, I skimmed some cream I'd missed before feeding it, and the next couple of batches developed a very thin layer of slime on top that I first mistook for additional cream. This seems to have disappeared by now.
• My clabber doesn't smell "off" at all (I've been nibbling on it occasionally, and strained my leftover clabber into cheese yesterday), but it's quite sour, gives off a decent amount of gas when I go to stir it, and has a much grainier texture than I expected. The picture in source [4], especially, led me to expect more of a yogurt consistency.
• I've been clabbering in two mason jars kept side-by-side, and lately (for last three feedings), one of them has fully separated by the time I go to feed and the other is almost separating itself. For the last feeding, as an experiment, I used a few spoonfuls of whey (plus some tiny curds I couldn't keep out) to culture one of the jars, and the regular whisked clabber to culture the other. The clabber-fed one has separated already (it's been 22h), and the whey-fed jar hasn't yet.

Any insight you can offer, regarding either my general question or my progress, would be greatly appreciated! 

~~~

P.S. Thank you all so much for your generosity and dedication! I've been relying on this site for a while now and this is my first time posting.

[Bantams]

If you're getting bubbles/air then it has coliform bacteria. Toss it. I'm sorry!
Good raw milk should coagulate into a smooth uniform curd with just a bit of whey on top by 24 hours. Should smell like delicious tangy buttermilk.
I wouldn't worry too much about temp - I warm to 100 initially and then leave at room temperature (70). Don't worry about contamination from the room - the milk already has plenty of bacteria from the cows' biome, teats, etc. 

Try again with the same milk (just one generation) - but if it takes more than 36 hours or has bubbles or smells like anything other than nice buttermilk, the milk is not clean enough. You'll want a new source of raw milk. I disagree with those saying you can make a good culture after many generations of clabbering. If the milk doesn't clabber properly the first time, it has coliforms or other undesirable bacteria and is not something I would want in my kitchen.  Yes, it is beneficial to refine a good culture through successive generations, but if the milk isn't high quality to start with then it's not wise to use it in a raw state.

Unfortunately coliforms are common in raw milk (not usually an issue in regularly tested Grade A raw milk for retail (raw) sale though).  You may need to try various sources to find one that's suitable.  Incidentally, the clabber test (how well milk clabbers in 24 hours) serves as a fairly accurate representation of raw milk quality and serves as a handy quality test when lab reports are not available/feasible. 

[mikekchar]

AC4U for all of your great tips Bantams.  You've answered many, many of my unasked questions :-)

[EschatonNow]

Agreed, thank you for the insight!

Any recommendations for feeding? Does it matter if I feed my clabber with raw or pasteurized milk? Does it need to be super-duper fresh, or can it have been in the fridge for a few days to a week? Also, I've read that I can keep my clabber in the fridge for about a week between feedings, instead of feeding it daily on the kitchen counter--do I need to build it up for a few generations before I can do this? Lastly, how long will it last frozen if I want to use it to culture cheeses?

[Bantams]

You can "refine" your clabber culture by making a few generations, them freeze it in ice cube trays for cheesemaking later. I'm sure it will last in the freezer for a while.

You can feed it with pasteurized milk, or continue to use the raw milk if it's super fresh (1-2 days) and you don't have any issues with contamination (milk is always really fresh and high quality - you've never had any coliform development, etc). If the quality is hit or miss I would stick with pasteurized.
Either way, use a newly opened bottle.
The clabber should be fine in the fridge for a week at a time (it's useable for cooking for many weeks but I'm sure some species are less tolerant of the cold acidic conditions and die off).

I only have experience with clabber for fresh cheese and sour cream/buttermilk (very acidic preparations). For use in aged cheeses you may want a more nuanced/varied culture and so clabbering only for 12-24 hours without fridge storage will likely promote a wider range of species.  And that means making cheese (or new clabber) daily  which isn't necessarily practical unless you milk your own animals.  This is just my assumption based off of traditional cheesemaking using carried over whey/curd from day to day, batch to batch.