If you start your day with yoghurt for breakfast, don't take the health benefits for granted. Yoghurt is considered a convenient and healthy food, high in protein and low in fat. But - and I say this at the risk of upsetting industrial producers - most of the stuff on display at supermarket chains is made from modified milk and contains thickeners, sweeteners and additives. Any claims that this form of "dessert yoghurt" is healthy are questionable; these yoghurts are vastly different to unadulterated natural "live" yoghurt made the traditional way from whole milk.
Pictured above: Homemade yoghurt with strawberry and watermelon salad
Real yoghurt is fermented milk thickened by a natural bacterial starter. It contains no rennet and, in its simplest form, the whey is not separated and drained, meaning the yoghurt's composition and fat content remain the same as that of the milk used to produce it.
Its origins date back to when nomadic people soured milk inside animal-skin bags, most probably to better digest it. Yoghurt became popular in the cuisines of the Indian subcontinent, Greece, Central Asia and Eastern Europe. But with the odd exception of skyr - an Icelandic yoghurt introduced by the Vikings a thousand years ago - yoghurt was not well known in Western Europe until the early 20th century, when the research of Nobel Prize-winning doctor Élie Metchnikoff, known as the "father of natural immunity", linked the longevity of Bulgarian peasants with their consumption of large amounts of sour fermented milk, or yohourth.
In his book The Prolongation of Life, Metchnikoff suggested that yohourth encouraged certain bacteria to settle in the intestines, where they increased proteins, milk sugars and other nutrients like calcium. This has since been claimed to improve our immune systems, reduce cholesterol and the risk of diabetes, and offer an antidote to the negative effects of antibiotics. As a result, yoghurt has developed a reputation as a probiotic wonder-food beneficial to the digestive system.
In Australia, natural "live" yoghurt is known as pot-set yoghurt. Both its texture and flavour are influenced by a number of factors, including the type of animal, the composition of the milk, and the strains of culture used in coagulation.
Most of our live yoghurt is made from cow's milk, and we're spoilt for choice when it comes to those made with organic or biodynamic milk, either on the farm or in small regional artisan dairies. Seasons have an influence on quality, and yoghurt made in the spring is generally richer and creamier than yoghurt made at other times of year. The breed of cow is also important. Yoghurt made with Jersey cow's milk, for instance, has a golden colour compared with that made with Holstein Friesian milk; it's also exceptionally rich and creamy.
Yoghurt can also be made with milk from sheep, goats and buffalo; it's pure white in colour because non-bovine dairy animals do not absorb carotene.
"Fresh quality milk is everything," according to Richard Thomas of Meredith's Dairy, which produces celebrated ewe's milk yoghurt. For a bit of fun, compare the green-label version made with probiotic cultures to the blue-label version made without. It's the same milk, but they are very different.
The thick, creamy live buffalo yoghurt from Shaw River in Western District Victoria is another benchmark. Produced using only fresh whole buffalo milk from a single herd grazing the seaside pastures of the farm, it's higher in antioxidants, phosphorus and calcium than cow's milk, according to farmer Roger Haldane.
By contrast, the consistency of live natural yoghurt made from goat's milk tends to be thin and runny due to the very fine composition of the fat globules in the milk. It's common to find goat's milk yoghurt thickened with skim milk solids (including, shock horror, cow's milk solids) or from modified ultra-filtrated milk.
The strains of cultures used in production also have a significant influence on the balance of acidity, texture and flavour. Most live yoghurts contain Lactobacillus bulgaricus and Streptococcus thermophilus, but other bacterial cultures are often added to help make the yoghurt more easily digestible, the most common being Bifidobacterium and Lactobacillus acidophilus.
My advice is to think local. Check the label for added ingredients and, if you really want to ensure the benefits of those containing added cultures, remember yoghurt is best enjoyed fresh. The longer live yoghurt is kept, the more likely any added L bulgaricus will have cannibalised the L acidophilus to negligible qualities.
Or why not make your own natural yoghurt? It's remarkably simple - all you need is fresh good-quality whole milk and a few teaspoons of live yoghurt.