Many people believe when they're buying a packet of citric acid from the supermarket, that it is derived from citrus fruits such as lemons, oranges, and grapefruits. However, this is a common misconception. In reality, store-bought citric acid is not produced directly from these fruits. Instead, it is produced through a fermentation process using a specific type of mould called Aspergillus niger.

The process of producing citric acid begins with fermenting a sugar source, such as corn or sugar beets, with the Aspergillus niger mould. This mould is able to convert the sugar into citric acid through a series of metabolic reactions. Once the fermentation process is complete, the citric acid is extracted and purified to be used in a variety of products, such as food additives, pharmaceuticals, and cleaning agents.

While citrus fruits do contain natural citric acid, the amount is relatively low compared to the quantities needed for commercial production. Therefore, companies see it as much more cost-effective and efficient to produce citric acid industrially through fermentation.

So the next time you are enjoying a tangy piece of candy/lolly/sweet or a refreshing softdrink/soda, remember that a little bit of black mould is what gives it that sweet and sour kick.