When I took microbiology I learned that bacteria live a very specific temperature ranges and can not tolderate temperature extremes well. So how can the cultures in yogurt and frozen yogurt remain live and active at the temperature differences between your fridge and freezer and the lumen of your intestine?
Peter Griffin
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I did an undergraduate microbiology project on this. I spent many hours in the lab trying to find the three cultures listed on Activia since you left…I’m pretty interested, and pretty skeptical about all this stuff.
The best way make sure you’re getting live, active cultures is to make your own yogurt. As far as the frozen stuff, my guess is that the freezing will be primarily microbistatic and that some fraction of the initial culture will indeed survive the freezing. The choice of language you’ve given is problematic, isn’t it “contains live and active…” No doubt it *contained* live and active cultures, and if it we’re thawed, would probably have something living (though less than to start). Marketing to ignorant people is a wonderful thing isn’t it?
As far as the Activia thing, they’ve trademarked “Bifidus regularis” which is probably a made up name for some substrain of Bifidobacterium bifidus, an obligate anaerobic lactobacillus that they co-culture with the other facultative lactobacilli, although we had trouble finding it, even using the anaerobic jar. I’m quite sure that Market Basket or Stop and Shop brand probably has just as much probiotic value as Activia, at a much lower cost.
My bottom line…eat what makes you happy, for tomorrow we die
Anonymous
Frozen Yogurt Live Cultures
Anonymous
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How can yogurt and frozen yogurt contain the same bacterial cultures and both say live and active?
When I took microbiology I learned that bacteria live a very specific temperature ranges and can not tolderate temperature extremes well. So how can the cultures in yogurt and frozen yogurt remain live and active at the temperature differences between your fridge and freezer and the lumen of your...
ajmill1978
Microorganisms, especially yeasts and lactobacilli (which are the cultures you see in yogurt) have particular temperature ranges for optimal *growth*. But they can just sit around and survive at a much wider range of temperatures, especially colder temps.
Heating above certain temperature disrupts their cell membranes and proteins (denaturing them) effectively killing them. That's how pasteurization works. However, the same is not always true for freezing. Essentially, you just slow the microorganisms down so that they can't grow. Some may even die if they are punctured with an ice crystal, but a majority of microorganisms survive, when thawed and brought to room temperature.
This is why we can freeze yeasted doughs for shipment, whereupon they are thawed and will rise. In biochemistry laboratories, we keep bacteria frozen at -80C for years, only to thaw them out when we need them.
Anonymous
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