Retell Lecture

Are you a chocolate-lover? Even true chocoholics might not know what their favourite treat has in common with yogurt, cheese, and wine: its flavours come from fermentation. Fermentation is the process of improving a food through the controlled activity of microbes. The food you know as chocolate starts its life as the seeds of football-shaped fruit. Farmers scoop out the seeds and pulp into piles or boxes. The seeds are now called "cacao beans". They ferment for about a week before they're dried, roasted, and crushed with sugar until smooth and ready to eat. Let's go back to that fermentation step. Cacao fermentation is a multi-stage process. The first stage involves yeast. Just like the yeast in your beer, yeast in a cacao fermentation produces alcohol by digesting the sugary pulp around the beans. As the pulp breaks down, oxygen seeps in. And oxygen-loving bacteria take over. The bacteria generate acetic acid from the alcohol that the yeast produced. Acetic acid causes biochemical changes as it soaks into the beans, and that has a major impact on flavour. Finally, as the acid slowly evaporates and the sugars are all used up, spore-forming organisms begin to grow. Cacao is a wild fermentation. Farmers rely on natural microbes in their environment to create unique, local flavours.