The Science Behind Salt

Today we sprinkle salt on popcorn, stir it into sauce, or grind it onto a plate of pasta, but this readily available and cheap-as-chips seasoning was once more revered.

Table salt - the white isometric crystals found on almost every kitchen table, in every restaurant, in pretty much every single meal in the world - was once described by Plato as being especially dear to the gods, whilst Homer referred to it as ‘the divine substance’. ^{1, 2}

Salt, the fifth taste

There are numerous reasons for adding salt to food. Nowadays, the most common reason comes down to its unique ability to enhance the flavours of almost any food. It both enhances the pleasurable aspects of enjoyable ingredients, whilst masking certain flavours of otherwise bitter or unpalatable foods. In both ways, salt quite literally makes food taste better. ³

The effect is not, however, infinite. This is because salt not only has the capacity to enhance the positive sensory attributes of other ingredients – it also imparts a taste of its own. There are five primary taste sensations: sour, sweet, bitter, umami, and salty.⁴ Sodium Chloride, the prototypical salt, has an almost pure ‘salt’ taste, the intensity of which increases with rising concentrations. There is a point at which this rising ‘saltiness’ tips from adding to the level of hedonic pleasure derived from a salty snack to decreasing the palatability of food.³

This optimum level of salt (often referred to as the ‘bliss point’) does not have a set value, but rather depends on the other ingredients present, as well as on the individual consuming the food—with the bliss point varying from person to person depending on their previous salt exposure.^{3, 5}

How salt preserves food

Whist its sensory attributes are powerful, and undeniably the most dominant reason for its use in modern cuisine, historically, preservation was the main culinary use of salt.⁶

Salt is an effective preservative for many reasons: it binds to water, reducing the amount available for microbial growth and chemical reactions. It can also induce something called osmotic shock – a process which sees extensive water being lost from the microbial cell, leading either to slowing of growth or even cell death.

Today, although rarely utilised as the sole method of preservation, it is still frequently relied on in combination with other additives and/or techniques to create an environment that is highly resistant to spoilage.⁶

Salt & sauerkraut: how it ferments

Another salt-dependent culinary trend, currently experiencing an unprecedented rise in popularity, is fermentation. Despite constituting another form of food preservation – fermentation relies on the presence, as opposed to the absence, of microbes.

During the fermentation process, salt (in the form of brine), inhibits the growth of spoiling bacteria and fungi, but promotes the growth of the more salt-resistant lactic-acid bacteria (LAB). ^{6, 7} LAB convert energy from food sugars and starches into lactic acid which, by lowering the pH of the brine, acts as a natural preservative, as well as accounting for the deliciously tangy flavour characteristic of fermented foods.

This process is further helped by the salt drawing water and sugars out of the plant tissues, making them more readily available to the LAB, increasing the rate at which they can convert cabbage into sauerkraut, cucumbers into pickles and milk into yogurts and cheese. ^{6, 8}

Too much salt intake & health problems

Salt –or more specifically, the sodium component of salt— is essential for the proper functioning of our body. It is, amongst other things, necessary for the firing of nerve cells, in the contraction of muscle fibres and in the maintenance fluid balance.⁹

That being said, we need only small amounts for the healthy functioning of the body. Although the absolute minimum is not yet well defined, it is thought to be in the range of 200-500mg per day of sodium (or 0.5-1.25g salt). ¹⁰  

Today, with the prevalence of pre-prepared and processed foods, which heavily rely on salt’s capacity to both increase shelf life and improve taste, one has to almost actively try to be sodium deficient.

Whilst being low in sodium can have severe consequences, so too can having too much. High sodium intake has been linked to increased blood pressure (BP) and cardiovascular disease (CVD).¹¹ There is, however, a less widely discussed but growing body of evidence which implicates high salt consumption with a whole host of systemic problems, from osteoporosis to headaches.¹² Of these impacts, perhaps the most alarming is the potential for salt to promote cancer, most notably gastric and renal cell cancers.^{13, 14, 15, 16, 17}

Despite the necessary intake being so low, the average daily global intake is close to 9.75g of salt per day. ¹⁸ It should come as no surprise, therefore, to hear that the World Health Organisation (WHO) recommends that all member states implement a salt reduction program. Astonishingly, were global intakes brought down to within the recommended levels, an estimated 2.5 million deaths could be prevented every year.  ^{19, 20}

Take it with a grain of salt

Quite literally. A small amount of sodium is necessary for our health but try not to go overboard. Rather than opting for a high-sodium ready meal, try to get your sodium from a less processed (gut-friendly) fermented food, like sauerkraut. I myself am rather partial to a healthy serving of sauerkraut.

Have a go at fermenting from home, and let us know your own tips and tricks to get the perfect salty pickle!