Yogurt cultures seem to come in two varieties: heirloom and direct-set.

The difference between the varieties is that one is a carefully selected mix of bacterial strains (direct-set), and the other is a "mother" that's been cultivated and sustained over generations (heirloom).

Most direct-set culture will specify that the culture cannot be reused. This means that once the yogurt is done culturing, one should not use a part of that yogurt to culture more milk.

On the other hand, heirloom cultures are specifically meant to be reused and sustained.

Where does the difference lie?

My guess is that the direct-set is not a "stable" symbiotic mixture of microbes, so the fear is that if one reuses that yogurt AFTER it's been sitting in the fridge, it'll have some additional microbes it may have picked up in it, which may foul the next batch.

The heirloom variety may be more "stable" in some way, so any additional microbes may be out-competed and won't survive into the next batch.

Another question is: if contamination is the only worry in direct-set cultures, could one immediately freeze direct-set yogurt (to avoid contamination) and then reuse it to get similar results?

  • 1
    It's also possible that the microbes in the direct-set will compete with each other or otherwise die off as part of the process, so the resultant yogurt might not have the same mix as what you started with. ... or it's all just marketing to try to make you buy more each time. I really have no clue. (this is all just speculation)
    – Joe
    Commented Nov 26, 2015 at 13:34
  • @Joe: That's also a good point, I didn't think of that possibility. That's really the crux of the matter though: will it be so bad if I reuse it?
    – Ron
    Commented Nov 26, 2015 at 14:15

4 Answers 4


It's simple. Heirlooms will produce expected results no matter how many times you reinoculate your culture. Direct set is a blend of species and eventually only the strongest strain will remain and it may not create anything you want to eat. I never bought cultures, I just buy plain or vanilla yogurt, eat it and use what's left behind to make another batch.

Remember the single most important part of yogurt making is hygiene. I can't stress this enough. Yogurt won't always tell you it's bad until it's too late and you eat it and get very very sick. Trust me on this from experience. With yogurt HYGIENE is the most important part of the process.!!!


I have re-used my direct set with success; just No Guarantee.

Contamination issue is no different.

Think of Heirloom as an old-time garden tomato vrs a high performing hybrid that won't breed true.


40 Batches with "Direct-Set" and no Problems

12 years ago I never heard of heirloom cultures and at the time I had started my culture from a freeze-dried starter that lasted 40 batches without degradation in quality and the only reason it stopped was because I was out of country for three months. That starter would have been described now as "commercial" or "direct-set".

I have started again with a freeze-dried starter and I'm 4 batches in and see no degradation in quality just as before.

No Proof of Heirloom cultures

The only mention I can find of "Heirloom cultures" and the terms such as "commercial direct-set culture" points back to two sources. One being a website called: https://www.culturesforhealth.com and a book which is also sold on that website called "The Art of Fermentation".

There's no real proof or scientific study for these "heirloom cultures" and since there is only one know place to buy "heirloom cultures" its just as reasonable to believe its a marketing lie.

Easy to believe you need to a Heirloom Culture to mask learning failure

When I first started making yogurt I had quite a few failed batches, but this was corrected when:

  • I got yogurt makers to keep the incubation temp consistent
  • stir constantly so temp was evenly distributed
  • invested in a digital thermometer
  • learned to be patience and heat my milk at the lowest setting
  • ensure to hold the temp at 180F for 15-30mins to get desired thickness
  • keep my yogurt plain for starter, and mix my flavour at time of eating
  • and start new batches within 7-12 days.

If I was for the first time learning now I might falsely believed it was my culture being a so called "direct-set" because I would keep thinking "what if?".


I think putting your starter (some yogurt you want to use as) in the freezer will also prolong and ensure how many generations of batches will be able to be made in the future. My mother in the US taught me how to make yogurt as a child. Then when I lived in India with my Uncle I learned how to make (heirloom) Starter; yogurt from scratch with no previously originated Starter; or previous yogurt to use to in the fermentation process. Heirlooms vary (how to make) Starter by Country.

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