A matter of Taste: Salt

Salt is essential for us to survive and humans have added salt to enhance the taste or preserve food for thousands of years. The trade in this highly valued commodity has even been attributed as the beginnings of human civilisation.  Its use in food preservation meant that people could store food over winter and food could be traded over large distances, allowing travel and the mixing of cultures and ideas.

Salt enters the salt taste cells through sodium ion channels.  These channels are found on the top of the taste cells that form part of our taste buds. When the sodium enters the taste cells it causes a signal to travel from the top to the bottom of the cell, which is next to a nerve cell. The nerve cell then transmits that signal to the brain. Once in the brain all the nerves transmitting 'salt' signals are clustered in the same area, no matter where in the  mouth the original taste was detected, and are interpreted as 'salty'.

The sodium channels can also allow the acid found in sour foods into cells.  I've been known to add too much salt when cooking and tried to reduce the salty tast by adding lemon juice.  This works because the citric acid in the lemon juice interacts with some of the 'salt' receptors  - reducing the number of receptors detecting 'salt' and therefore reducing the perception of saltiness.

Yet as well being essential for our bodies to function, too much salt can be bad for us. Our bodies therefore try and maintain the balance of salt we need and our sense of taste has adapted to help that regulation.  Our bodies have a threshold level of salt, above which we no longer like it.  This 'bliss point' is different for each person. And salt also does more than make our food taste salty.  It also affects our perception of other tastes and textures such as sweetness, thickness or as an overall flavour enhancer, which is partly why it's used in the food industry. Alternatives to salt, which don't have the undesirable health consequences, have been developed but these can tase different to normal salt.  For example, potassium chloride (instead of sodium chloride which is 'normal' salt) can taste bitter.


The other reason our food industry values salt is the same as in ancient times - its preservative quality.  High levels of salt prevents the growth of the microbes that cause food to spoil or make us ill.  Using salt for this purpose can lead to very high levels of salt in some processed foods as part of the strategy to extend food shelf life. 

Our innate love of salt combined with its utility in preserving food and enhancing flavour makes reducing its use difficult for food producers.  They are trying to meet consumer demand and pressures from healthcare providers to reduce salt in foods, whilst retaining the shelf life and taste profile of their products. Perhaps the only way to successfully achieve lower salt in processed foods is for us as consumers to change our expectations of both shelf life and taste.






References:

http://www.ncbi.nlm.nih.gov/books/NBK50958/#

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072592/

http://www.ncbi.nlm.nih.gov/books/NBK11148/

http://www.nih.gov/researchmatters/february2010/02082010taste.htm

http://www.cf.ac.uk/biosi/staffinfo/jacob/teaching/sensory/taste.html#WhyTaste