Amasi – called maas in Afrikaans – is the thick, tangy fermented milk eaten across South Africa, Zimbabwe and neighboring countries. It’s poured over maize porridge, drunk from the glass and sold in cartons in every South African supermarket. Traditionally it was made by leaving raw milk to sour on its own, often in a calabash. At home today, the safe and reliable way is pasteurized whole milk with a small amount of starter, left at room temperature for a day or two. Why raw milk stays risky even once it has soured is covered in can you make kefir or yogurt with raw milk. The full recipe is below.
What Amasi Is
Amasi is milk soured and thickened by lactic acid bacteria at room temperature – no heating step and no rennet. It sits somewhere between buttermilk and plain yogurt: thick enough to spoon, pourable when stirred, and tart. Left long enough, it separates into white curds and a thin, yellowish whey; many people pour off the whey for a thicker result.
When researchers analyzed 15 traditional fermented milks from households in South Africa and Namibia, lactic acid bacteria dominated, mainly Lactococcus lactis, Leuconostoc species (especially Leuconostoc mesenteroides) and some Lactobacillus (Beukes et al., 2001). These are “mesophilic” bacteria that work best at room temperature – the same group used for cultured buttermilk – which is why amasi doesn’t need an incubator.
Amasi in Southern African Food
In many Southern African homes, cattle and milk carry deep cultural weight, and soured milk was the practical way to keep milk before refrigeration. Traditionally, milk was left to ferment in a calabash or clay pot, and a little of the previous batch – or the vessel itself – seeded the next one.
The most classic way to eat it is with maize porridge: crumbly umphokoqo or phuthu mixed with cold amasi, or stiff pap dipped into it. Commercial maas is made from pasteurized milk with starter cultures and is widely sold in South Africa.
It’s important enough nutritionally that South Africa’s revised food-based dietary guidelines recommend having milk, maas or yoghurt every day, and researchers reviewing that decision described maas as a culturally relevant traditional food (Du Plooy et al., 2018).
Other African fermented milks include Kenya’s smoked mursik and the Fulani fura da nono. For a Nordic relative made the same room-temperature way, see filmjölk.
Why We Don’t Recommend Raw Milk
Many recipes call raw milk the “authentic” choice, because its own bacteria sour it without a starter. But raw milk can carry Campylobacter, E. coli, Listeria, Salmonella and Brucella, and anyone can get seriously ill from it – especially children, pregnant women, older adults and people with weakened immune systems (CDC). Souring does not reliably make it safe:
- E. coli O157:H7 survived fermentation and storage in goat-milk amasi (Dlamini and Buys, 2009).
- The bacterium that causes bovine tuberculosis survived for at least 2 weeks in souring raw milk at 20°C (Michel et al., 2015).
- In Zimbabwean trials, raw milk left to sour on its own or with back-slopping had the highest E. coli counts after 48 hours, while an added starter culture lowered the pH faster and kept E. coli lowest (Gran et al., 2003).
So the recipe below uses pasteurized milk and a starter. It still produces thick, tangy, live-culture amasi.
Choosing a Starter
- Store-bought amasi or maas – the obvious choice if you can find it.
- Cultured buttermilk with live cultures – made with the same kind of room-temperature bacteria.
- Your previous batch – keep 2–3 tablespoons back each time. Start fresh from bought starter if a batch tastes off.
- Not ideal: yogurt. Yogurt cultures work best at around 110°F (43°C) and are slow and unpredictable at room temperature. Use them only if nothing else is available.
Use whole, regular pasteurized milk. Skim milk gives a thin result, and ultra-pasteurized (UHT) milk tends to set more weakly.
Signs It’s Ready – and Signs Something’s Wrong
- Ready: the milk has set into a thick mass that pulls away from the side of the jar when tilted, and it smells clean and sour, like buttermilk. Some whey on top or at the bottom is normal.
- Too sour or very separated: it fermented too long or too warm. Stir it back together, use it in baking, and shorten the time next batch.
- Still liquid after 48 hours: the room is too cold (below about 65°F/18°C) or the starter was weak. Move it somewhere warmer.
- Throw it out if you see fuzzy mold (any color), pink or orange patches, or if it smells rotten, putrid or like nail polish rather than sour.
How to Eat Amasi
- With maize porridge: mixed into crumbly phuthu or umphokoqo, or with stiff pap.
- As a drink: stirred smooth and poured into a glass, plain or with a little sugar or honey (no honey for babies under 1).
- In place of buttermilk in scones, pancakes, soda bread and muffins.
- In smoothies instead of yogurt or kefir – see our kefir smoothie recipes.
- As a dressing or dip base with garlic, herbs, lemon and salt.
Amasi, yogurt and kefir compared: amasi and yogurt are both soured milk, but yogurt is incubated warm with specific thermophilic cultures, while amasi sours at room temperature. Kefir uses grains containing yeasts as well, so it’s fizzier. See kefir vs yogurt and how to make yogurt at home. In Kazakhstan, camel’s milk is fermented into shubat.