Do frozen and pasteurised yogurts lose their beneficial properties?

Eating yogurt every now and then is healthy due to the lactic ferments that help our bacterial flora, especially when they are alive. But, don’t these lactic ferments die in frozen and pasteurised yogurt and therefore stop being beneficial for our health?  

Question sent by OLGA IBÁÑEZ (València). MERCÈ PIQUERAS answers:

Even though TV advertisements talk about «lactic ferments», actually they should talk about «bacteria». They probably do it for marketing reasons, because people link bacteria with infections. Yogurts do contain biological ferments —enzymes that cause milk fermentation. Living bacteria is what makes yogurt so beneficial for our health. (Piqueras i Mariné, 2006). There are researchers who won’t accept that yogurt bacteria are beneficial for our immune system, but many studies show that this beneficial effect is indeed real. I also believe it is true, due to my own personal experience.

I do not know what happens with frozen yogurt, but most bacteria survive the freezing process. In act, bacterial cultures are kept frozen. Pasteurised yogurts are another story. They should not be called «yogurts» because bacteria die and, by definition, yogurt is a milk derivate that contains living fermentation agents— that is bacteria. In 2003, Spain decreed a change in the definition of «yogurt», and a yogurt variety was introduced— «pasteurised yogurt after fermentation». That is an oxymoron because, if pasteurised, there are no living bacteria left, only their «corpses». This change was made by the time Leche Pascual (a very popular brand of milk in Spain) and Danone were in dispute (Piqueras, 2004).

Mercè Piqueras. Biologist and science writer.