The second article, the actual scientific study, is long and difficult to read, but it does support the conclusion that you can't just use a probiotic like VSL3 and expect to get yogurt with the same mix of bacteria.
For example, the classic yogurt culture is characterized by a protosymbiosis between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. This synergism, seen as an accelerated and efficient acidification of the milk and multiplication of the culture organisms and based on cross-feeding of both organisms, is not a property of the 2 species but of specific strains of theses species (18–21). Antagonism, on the other hand, is often based on the production of substances that inhibit or inactivate more or less specifically other related starter organisms or even unrelated bacteria.
In other words, one "starter organism" is probably killing off the others, when you dump a mix of probiotics in your milk, such as found in VSL3. This is what "antagonism" and "inhibit or inactivate more or less specifically other related starter organisms" is referring to. It's the antagonism between one starter organism and another starter organism, which is what the different bacterial strains in a probiotic starter (like VSL3) would be.
The passage continues:
Most importantly, antagonism is caused by bacteriocins, which are peptides or proteins exhibiting antibiotic properties (22, 23). The ability to produce bacteriocins is often discussed as a desirable property of probiotics (10); however, antagonism to starter cultures and vice versa may be a limiting factor for combinations of starters and probiotics.
The last phrase really makes the point. Putting the usual starters, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, together with other probiotics limits the potential for them all to survive, because they will probably compete with each other. Again, the article indicates, there is "antagonism" between them, caused by the "bacteriocins" that the different strains release. Also it's important to note, if you look it up, that "bacteriocins" are inhibitory factors (antibiotics, in fact) released by a bacteria that inhibit the growth of closely related strains (which is exactly what the various probiotic strains in something like VSL3 are).
The article continues:
The intensity of the interactions between probiotics and both the food matrix and the starter organisms depends in large part on the time that probiotics are added to the product, ie, whether they are present during fermentation or are added after. In the latter case, interactions may be minimal because addition may occur immediately before or even after cooling below 8°C and the metabolic activity of starters and probiotics is drastically reduced at these temperatures. However, with extended storage, even small interactions may yield measurable effects. Also, an interruption of the cold chain must be avoided to keep interactions to a minimum.
This says, adding the probiotics later, after fermentation, when the yogurt has been cooled, allows them to survive. Before that there will be "interactions" (i.e. antagonism), between the probiotics and the starter organisms. In addition, the longer the yogurt sits there, even at cool temperatures, the more the various probiotic strains will kill each other off.
You can't just look at the concluding paragraph of this long, detailed, abstract article, which is what AZYooper quotes above, and assume you've fully understood what the whole article is saying.
So the article really is not just questioning the labelling of commercial yogurt. It questions the way probiotics are added to commerical yogurt and discusses in very precise detail how the manufacturing process itself effects whether the probiotics even survive. And these problems apply just as much to making your own yogurt at home.
I also really would not say the worst case scenario is that you get just plain old yogurt. The worst case (and fairly likely) scenario is that you don't know what you have. That to me seems deeply problematic and not a good idea. Best case, you just have plain old yogurt. But there is almost no chance you have anything approximating VSL3 (or whatever probiotic you use as a starter). The different strains in the probiotic are going to compete with each other and only some are going to survive.
So I think, unfortunately, people are really throwing away money using VSL3 or any probiotic as a starter, instead of just regular yogurt starters.
Post Edited (gg555) : 10/5/2011 2:00:56 AM (GMT-6)