Mercadona's kefir in Spain: fermented or just milk with strains?

Mercadona's kefir in Spain: fermented or just milk with strains?

In the supermarket there is a product called kefir which, when peine, has the texture of a liquid yogurt. Nothing like the lumpy, cauliflower-like mass you get when fermenting milk with traditional kefir grains. The question hanging over the package is simple: how much kefir is actually in the kefir sold in stores? The short answer is that nobody knows, because the label does not say.

The product sold under that name is made, according to some participants' guesses, from milk that undergoes heat treatment and is then inoculated with cultures. The result is homogeneous, smooth and stable. Homemade kefir, on the other hand, is a live culture that ferments milk in about 24 hours and produces a tart, slightly fizzy drink with an irregular texture. The difference in taste and behavior in the glass is the first clue that they are not the same thing.

What the label of Mercadona's kefir says

The package does not specify the percentage of kefir or the amount of live microorganisms. Nor does it clarify whether the final product has been pasteurized after fermentation, a step that would eliminate any active cultures. The absence of this information is itself telling: if the manufacturer does not boast about probiotic content, it is probably because it cannot.

Some argue that pasteurization is applied only to the milk before inoculating the cultures, which would allow some bacteria to remain alive. Others maintain that the product is packaged immediately after adding the strains, without giving them time to ferment. In both cases, the result would be a dairy drink with little or no real kefir.

Homemade kefir: the cauliflower you don't eat

Traditional kefir is made with grains, a mass of bacteria and yeasts that is placed in milk and left to sit for a day. After that time, the liquid is strained and fresh milk is added back over the grains. These grains grow and multiply, so the surplus has to be removed. What you drink is the fermented milk, not the cauliflower.

The texture of homemade kefir is thicker and more acidic than the packaged product. Some consumers describe Mercadona's as "liquid yogurt" and point out that it bears no resemblance to what you get at home. The difference is not just one of taste: homemade kefir contains a living microbial community that the packaged version may have lost.

The debate about honey and probiotics

One of the most repeated discussions is whether honey kills kefir cultures. Some claim that honey is a natural antibiotic and that adding it destroys the strains. Against that idea, studies are cited that use honey as a substrate for growing kefir and describe the result as a product with high antioxidant power. The evidence is inconclusive, but the debate reflects a broader concern: whether packaged kefir retains any probiotic properties at all.

Alternatives in the supermarket

Mercadona's kefir is not the only one. Similar products are sold at other chains, with different textures and flavors. Some consumers prefer brands like Margui or those offered by Alcampo, which they describe as more fermented and with a taste closer to homemade. The difference in price and quality varies, but the label still fails to clarify the actual kefir content.

Is it worth making it at home?

Making kefir at home is simple: get some grains, add milk and wait a day. The cost is minimal and the resulting product is a live probiotic. The drawback is the upkeep: the milk has to be changed every 24 to 48 hours, and if you neglect it, the culture can weaken or become contaminated. Some enthusiasts have seen their grains stop growing after months of use, possibly due to the cold of the fridge or a lack of nutrients.

The safety of homemade kefir depends on hygiene and the quality of the grains. There is no health control like that of a packaged product, but the practice is common and the risks, if a few basic rules are trinc, are low. The remaining question is whether supermarket kefir offers anything more than fermented milk. The answer, as of today, is still not on the label.