How safe are bacteria, yeast, and enzymes used in the making of foods like yogurt, cheese, and bread? Don’t these organisms mutate?
First of, an enzyme isn’t an organism, but rather a protein.
Second, yes they do sometimes mutate. However, in a particular colony finding one mutant is no big deal, because the other hundreds of millions of bacteria or fungi will not be mutants. It only becomes a problem if the mutant strain breeds faster than the desired strain. If that happens then you have to throw out that batch.
Plus, mutation shouldn’t imply that it mutates into something dangerous. Most mutations result in the organism unable to survive in the current environment and they die off. Sometimes mutations are neutral and provide no benefit or harm to the organism.
Right, most of these mutant strains aren’t dangerous, just unpalatable, or perhaps simply don’t have the exact effect the manufacturer desires.
Take for example yogurt. Different strains of yeast can produce different tasting yogurt. Yogurt can be made from wild cultures…leave raw milk sitting out and it will naturally turn into yogurt. But commercial yogurt production depends on being able to precisely replicate the same product every time. So whatever cultures are desired are isolated, grown, and then added to the milk. The milk will invariably have other cultures already present, but if you add millions of yeast cells of a particular strain they will outbreed and overpower any undesirable cultures that start with only a few cells even if the undesireable cells multiply more quickly they’d need many generations of doubling to catch up to the introduced culture.
And producing pure strains of a culture is pretty easy. You simply take a sample from your yogurt and smear it on an agar plate, then smear that smear a bit farther on the plate, then smear that smear. Let the agar plate grow for a while, and you’ll have a colony. The extremely dilute smears will have colonies that show up as single dots because that colony was founded by a single cell. Sample the single dot colony and you’ll know that every cell in that colony is identical. Now, it may be the case that through some fluke the single colony is an undesireable strain, so you test that batch to make sure it produces the yogurt or whatever you desire. Then grow large amounts of cells from that colony, and innoculate your milk from the master batch.
Of course, you can simply innoculate new batches with a little bit of leftovers from previous batches, but then you’ll get mutants and eventually your yogurt isn’t going to be exactly the same as it was the first time. You have to breed and innoculate with pure strains to be sure of making the exact same thing every time. Ancient herders just used the old batch to innoculate the new batch, but modern agribusiness use pure strains.
They’re doomed, man. You’ll be fine, but the yeast is a goner when the oven turns on.
Sailboat
Very informative–and comforting. Thank you all.
Actually, yogurt is produced by bacteria, not yeast and I believe that only Lactobacillus or Bifidobacterium cultures are currently allowed for commercial yogurt. The FDA considers yeast and other cultures “contaminates” if I’m not mistaken. It’s been a long time since I studied yogurt production. I’ve been making my own for 25 years using cultures not commercially available.
Don’t many of the hundreds of different types of cheese come from different, i.e. mutated, bacterial strains in the first place?
Yeah, I’m a bit slack when it comes to cleaning out the fridge, too.
Surely the biggest problem with yoghurt, beer, cheese etc. is not mutation of active cultures, but contamination with other (airborne) bacteria/yeast spores?