What is yoghurt, exactly?

What is yoghurt?

In its simplest form, yoghurt is fermented milk. To make it, milk is first heated to about 85°C to “denature” the protein (change its structure), which subsequently prevents it from forming curds. Once the milk has been cooled to around 45°C, live cultures are added, specifically Lactobacillus bulgaricus and Streptococcus thermophilus (although other bacteria may also be included) to encourage fermentation and convert the lactose into lactic acid.

In essence, yoghurt is a way of prolonging the life of fresh milk and has been used for centuries across many cultures – you’ll find it fresh lassi drinks to dressings, marinades and desserts, and used as a thickening agent.

These days, you’ll find good brands in a variety of styles in supermarkets, as well as at farmers’ markets and independent grocers where small-scale producers, such as Marrook Farm on the Bulga Plateau, NSW, are worth supporting. There are significant differences between pot-set, Greek-style and stirred yoghurts, so here’s the lowdown…

Pot-set

As the name suggests, this has been set in the pot it’s sold in. Because it doesn’t require stabilisers, pot-set yoghurt tends to separate into milk solids and whey, which can be poured out for use in cooking.

Pot-set yoghurt is sometimes sold unhomogenised, which leaves a layer of cream on the top. Use this style of yoghurt for curries and dressings.

Greek-style

True Greek-style yoghurt is generally creamier as it’s been strained to remove most of the whey, resulting in a richer product. Some commercial brands add thickeners and/or sweeteners, so check the label. It usually has about eight per cent fat content (about double that of pot-set), and is high in protein. It’s great in desserts, stirred through soups and for making tzatziki.

Stirred

If yoghurt isn’t labelled as pot-set or Greek-style, then it’s stirred yoghurt, which is made in a bulk vat before being packaged. Some stirred yoghurt has added milk protein or whey powder which helps to thicken the texture and gives a glossy finish.

Milk types

In Australia, we typically consume cow’s-milk yoghurt, but it’s also possible to find yoghurt made with sheep’s, goat’s and buffalo’s milk, and soon even camel’s milk. Each type has its own characteristics: buffalo’s is high in protein and fat, producing a rich yoghurt; sheep’s is high in fat, giving the yoghurt a very creamy texture; while goat’s has smaller fat molecules, creating a thinner yoghurt.

Notes on buying:

Always check the label for added sugar or other extra ingredients.

Light can affect the flavour in glass packaging, but glass is a more sustainable choice than plastic.

If you find that yoghurt is too thin for your liking, make your own Greek-style yoghurt by straining it through muslin or a coffee filter in a sieve over a bowl. Stir salt through the yoghurt before straining to make labne.