Why are all sour cream cultures I've found for sale online labeled as direct set? Why can't I reuse like I do yogurt?

Question

I've realized we go through a lot of sour cream in my household, and I want to start making probably about a pint or two a week during the summer months.

I've been researching for a few hours, and while I haven't found any reusable sour cream culture, I haven't found any reason I can't reuse sour cream culture. On the same websites selling culture, there's reusable yogurt and cheese culture, so I'm pretty sure it's not just a sales tactic.

I've come across a few articles that state you have to be careful with reusing culture for other fermented milk recipes. It looks like contamination with other bacteria is a concern even with yogurt. Learning that, I may just go ahead and start setting aside my culture for the next batch right off the bat, before any spoon or air contamination can hit the yogurt. I learned from my parents, who reuse from the bottom of the pot when we're getting low.

The only reason I can think of for sour cream being an issue is temperature. I assume that at 75 degrees, a lot of different bacterias can thrive. With yogurt at 110 degrees, maybe it's more of a hostile environment to unwanted bacteria, making it more easily reusable?

If that's the case, I think I can make a jar of sour cream and pour it into an ice cube tray and freeze it to provide myself with culture for a few more batches out of that one.

If there's something special about sour cream culture that it's not reusable at all, why is it special, and can I make my own through some process?

Answer 1

If you can't find a reusable sour cream starter, you can use buttermilk starter. Some bloggers and biology/chemistry professors just use fresh active buttermilk as a starter rather than ordering some online. If you look at the various labels and product pages, you will find that both the buttermilk and sour cream starters contain the same four cultures: Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Lactococcus lactis biovar diacetylactis and Leuconostoc mesenteroides subsp. cremoris.

In the Q & A for their buttermilk starter, culturesforhealth.com also provides this tip for using it for sour cream:

It is best to maintain it in regular whole milk, rather than reculturing cream long term.

On another page, Dr. Frankhauser goes on to say:

SOUR CREAM is produced by the same bacteria as buttermilk, but the starting milk product is pasteurized light cream. Bacteria are less numerous than in buttermilk.

This may be related to the lower concentrations of lactose found in unfermented milk products that contain higher percentages of fat. My best guess is that companies don't market the sour cream starters as heirloom or reusable because starting the new batch from the last batch may not reliably provide results that are as robust over time as their other products. If you just use milk for your starter, you can reuse it over time.

Answer 2

You don't actually need to buy sour cream starter - I never did - you can just buy a carton of cultured buttermilk (if it is 'fresh' - they have a long shelf life, but the bacteria might not live that long, so get one with a date well into the future), then make your own batch of buttermilk from that, and then use YOUR buttermilk to start the sour cream. Your own buttermilk will be popping with culture compared to the store-bought.

Sour cream is restartable without buying more IF you keep your buttermilk culture going. I did that for quite a while, would make sour cream by using a dollop of my buttermilk as starter. My sour cream would last me a long time, so even aside from the info here that sour cream doesn't contain as much culture as buttermilk, by the time I finished eating it I'm sure most of the bacteria in it likely weren't viable anymore.

I would add that my home-cultured buttermilk was a million times better-tasting than store-bought buttermilk, even though I started it with (a large dollop, like half a cup, of) the store-bought. And mine was so thick you could almost stand a spoon in it. I had never liked buttermilk until I cultured my own. It tasted like Lassi from an Indian restaurant, but was even thicker.

Buttermilk and sour cream are insanely easy to make, because you don't need to heat the milk or cream up first to sterilize it. You just add the culture, shake and stir it up, (cover I think?), and let it stand on your counter for 24 hours or just overnight if it's not too cold. You add a fair amount (especially if it's storebought buttermilk because by the time you buy it, the culture may be dying out). Years ago I even emailed Dr. Fankhauser (of Fankhauser's Cheese Site) to ask him why, and he answered me that the bacteria that produce cultured buttermilk and sour cream are very aggressive compared to those that produce yogurt, and they basically overwhelm and kick out any 'bad' bacteria that might be in the milk. Not the case with yogurt cultures, they can be overwhelmed by bad bacteria if any are present. That's why you have to sterilize the milk for yogurt (or use reconstituted powdered milk). He was a professor of microbiology so I trust him! And a really nice guy.