If there is one dish that screams Korean food then that must be kimchi! A fiery, tangy, umami-packed staple food, this delicacy is more than just a side dish, but a truly fascinating example of food science at work, from its very first step of preparation. 

At its core, kimchi is a fermented food. This means that it is preserved by lowering its pH (increasing its acidity). This acidic environment keeps unwanted microorganisms from taking over and spoiling the food. Fermentation is indeed one of human's clever trick to making food last, even for years! All over the world, people have been fermenting foods long before fridges were invented. It turns out fermented foods are also delicious which is why some of these foods, like kimchi, are very popular nowadays. Today we do not need fermented food for survival but we still ferment some foods because we love those complex flavours and, as science shows, it is good for us too! Kimchi is rich in probiotics, those friendly bacteria that support a healthy gut microbiome, aid digestion and boost our immune system (and make our skin glow too ;))!

Kimchi is mostly associated with spicy fermented cabbage but in reality kimchi can be made with radish, kohlrabi, spring onions and plenty of other vegetables. Some regional varieties also include seafood. Think fish sauce and fermented shrimp for that extra savoury kick. 

So let's delve into the science angle!

Why is kimchi safe to eat, even after months or years sitting in a jar? 

The answer is Salt. 

When you salt vegetables (pretty much the first step of preparing kimchi) you are not only seasoning them, but you are killing off most bacteria except for the halotolerant (salt-tolerant) ones. These survivors are mainly lactobacilli, a type of bacteria that thrive on sugars. You feed these bacteria with sugar and sometimes cooked rice flour and as they munch away they produce acids (which lower the pH and stop harmful microbes from growing) and carbon dioxide (which creates an oxygen free or "anaerobic" environment that keeps the fermentation going). 

The result of this is a tangy, crisp, fermented kimchi bursting with flavour and alive with beneficial bacteria, but just one word of warning on this, that carbon dioxide builds up pressure inside your jar, so unless you fancy a kimchi volcano erupting in your kitchen remember to "burp" your kimchi every now and then. 

So for those in food science and technology, fermentation presents a complex process, especially when we think of an industrial scale food manufacturing operation of kimchi. Fermentation involves multiple types of bacteria, sugars, acids, temperatures and time and predicting how a batch of kimchi will turn out, can be quite complex due to the many variables. Using computational tools at our disposal we can simulate the growth of bacteria, the production of acids as well as the formation of gas under the different conditions allowing us to optimise fermentation time for consistent flavour and texture and experiment virtually with ingredients or salt levels to see how they affect taste as well as safety. So modelling and simulation helps turn centuries-old culinary art into a precise science without losing any of its magic.