🥣 Yogurt

Yogurt is a fermented milk product made by culturing milk with two heat-loving bacteria: Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. That is how the Codex Alimentarius standard defines it: these bacteria have to remain alive and abundant — at least 10⁷ colony-forming units (CFU) per gram — until the end of the shelf life.

At the factory, milk is standardised, heated to 90–95 °C for about 5 minutes so that the curd sets firmly, cooled to 40–45 °C and inoculated with the starter. Over 4–5 hours at 42–43 °C, lactic acid lowers the pH to 4.2–4.5, the casein coagulates and the yogurt thickens. Under the Codex, yogurt has to contain at least 2.7 % milk protein and 0.6 % acidity.

The Codex classes strained yogurt — Greek yogurt, labneh — as a concentrated product with at least 5.6 % protein; whey may not be drained from ordinary yogurt. Yogurt differs from kefir in its starter: kefir grains contain yeasts, and kefir is fermented at about 23 °C.

Yogurt or kefir? They are different products: yogurt is cultured with two bacteria at 42–43 °C, while kefir is made with kefir grains containing yeasts and fermented at about 23 °C. Greek yogurt is simply strained yogurt: under the Codex, strained products, labneh included, hold at least 5.6 % protein, while ordinary yogurt needs 2.7 %. So Greek differs from regular in the whey drained off, and from kefir in the culture and temperature. When choosing, compare ingredients and sugar on the label rather than names.

On the shelf, look for the word 'yogurt' in the name: under the Codex Alimentarius it may be used only for a product that meets the standard. If the name says something else, such as 'yogurt product', read the ingredients more carefully. Yogurt heated after fermentation holds no live bacteria, and that has to be stated. Strained styles such as Greek carry at least 5.6 % protein, which the nutrition table shows. Look in the chilled aisle of a supermarket or discounter, or at a market.

Why it matters to you. If yogurt has been heat-treated after fermentation, it no longer contains live bacteria — under the Codex such a product has to be labelled 'heat-treated'. In the EU, the claim that live yogurt cultures improve lactose digestion is allowed only when there are at least 10⁸ CFU per gram. The NHS recommends choosing plain low-fat yogurt with no added sugar and checking the sugar on the label. Keep yogurt in the fridge at 0–5 °C and follow the use-by date.