On a counter, on a wine farm, there's a large glass jar containing a thick liquid of a mushroomy, off-white shade. There are small bubbles in the slop. There are worrying indications of condensation on the inside of the jar. It's alive. But what is it?I ask the man behind the counter. He is one of the bakers at Lust, the newish bistro and bakery at Vrede en Lust. (Lust is pronounced the Afrikaans way, with a heavy "uhgh", not the English way, as in panting desire.)It's a sourdough starter, the man tells me, the stuff they use to make the round sourdough loaves here. But why is it on display?That mixture is 15 years old.It's a "wild yeast culture", according to Lust's menu, "created and nurtured by patron chef Jean Pierre Smith".Smith confirms that he first mixed this particular bread starter in 2000."For a South African starter, it's mature, developed, but there are some in France and San Francisco that are 140 years old."What is a bread starter, and what's a wild one?Most breads are made with cultivated yeast, which reacts with water, flour and heat to create air in the dough. Once activated, "bakers yeast" will not last.In Smith's sourdough and rye bread starters natural fermentation takes place. It's also known as biological leavening. The lactobacilli and yeast he uses are sourced from nature. That's the "wild" part.The lactobacillus species of bacteria - found in the urinary, digestive and genital tracts of humans - is very good at lowering and maintaining the pH balance (acidity) of a substance. It's this ability that prevents the starter culture going off.Smith dips into his 15-year-old starter for all his sourdough loaves. He uses it to make bread starters to sell. He feeds it, too.The maturity of a sourdough starter leads to "beautiful layers of taste", he says.It's not all about taste, though. By definition, artisanal bread is shaped by hand; it's made in small batches and with natural processes.At Lust, Smith goes "the whole nine yards". After each sourdough and rye loaf is mixed, it undergoes fermentation for a further 96 hours. It is cooked in a wood-fired hearth."If I can put a loaf on the shelf in 24 hours, that's too fast for me."Obviously, the more artisanal the bread, the fewer industrial processes and chemicals.When it comes to the environment and our health - not to mention weight gain - it's important to know that there are breads and there are breads. There's a scale. Broadly speaking, artisanal bread is to supermarket bread what whole fruit is to fruit juice. Artisanal bread and fruit are sourced from nature. Fruit juice and supermarket bread are processed to within an inch of their lives."We are more aware now of what we are putting into our bodies," said Smith. "We would rather go the natural route."The lactobacillus bacteria used at Lust are also used in starter cultures for other foods such as yoghurt, cheese, sauerkraut, pickles and kimchi.Lust Bistro & Bakery is at Vrede en Lust wine farm, Franschhoek: 021-874-8155..