Under Italian law, only cow’s milk fermented with Lactobacillus bulgaricus and Streptococcus thermophilus may be sold as “yoghurt”. These microorganisms must be alive and active, that is, able to metabolise and multiply, right up to the moment of consumption.

The cell density is also defined by law: it must be equal to or greater than 100,000,000 cells (colony forming units) per millilitre. However, this does not mean that products obtained from other milks and/or by other enzymes (such as probiotics) may not be better from a gastronomic or nutritional point of view.