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You are probably aware that humans have five main taste sensitivities in the mouth; namely bitter, salt, sweet, sour and umami. There are claims of other taste sensations such as kokumi (an extension of umami expressed as heartiness or “richness”, such as in mature cheeses and slow-cooked foods), fats, and perhaps also starches (particularly the shorter-chain carbohydrates) – and on the surface, the claims seem quite plausible though due to genetic differences in humans, it is possible that these additional tastes may not be experienced as commonly as the main five tastes.

Regardless of whether humans experience five, seven or eight tastes, food scientists know a lot about the chemicals that trigger taste cells in human taste buds (a taste bud is normally a collection of different taste cells) – and hence there is an assortment of compounds which can be introduced to processed foods to render them much more attractive to eat.

The bitter problem

At this point, the bitter taste sense warrants a little further discourse – it is the most sensitive taste in most humans and probably evolved to protect us from ingesting poisonous foods.

As a result, humans generally do not like food which is significantly bitter, apart from coffee, tea, beers, certain vegetables and some alcoholic cocktails. Children also have up to three times as many taste cells as adults and this explains why many kids are particularly averse to bitter foods such as broccoli, sprouts, mushrooms, cabbages, et cetera – they tend to slowly lose this antipathy as they grow up.

The sense of bitter is actually pretty interesting as humans can sense bitter in many, many thousands of separate compounds, and if you are curious about how this works, here’s a little summary.

The problem is that some common food additives are particularly bitter chemicals and mass-produced food needs to address the general taste preferences of large populations – hence bitterness in processed foods is a problem which needs to be eliminated, or at least masked.

A classic example is drinks containing caffeine, which is a very bitter compound in its natural state – as a result practically all commercially packaged caffeine drinks are severely overloaded with sugars or sweeteners to mask the bitterness of caffeine.

There are around a dozen synthetic compounds which can block some of the bitter sensation – however, they are not very efficient as they cannot block all the bitter taste cells, so these compounds are not so commonly used.

food additives

The next time you read a food label at the grocery store, you will know a bit more about what those E6xx numbers stand for. Photo: AFP

Therefore, bitterness in processed foods usually need some form of masking, usually with sugars and salt. If there exists an effective way to reduce the taste of bitterness in foods, it is feasible that the sugar or salt content in many processed foods can be reduced by very significant amounts.

As a little digression, when looking into bitter-tasting food chemicals like E202 (potassium sorbate), E326 (potassium lactate), et cetera, I came across E211 (sodium benzoate) which is commonly used as a preservative agent in dairy, meat and other products due to its antiseptic properties – E211 is a curious compound as it can taste either salty, sweet, bitter or have no taste at all. How this happens, I have no idea but it appears to be linked to genetics.

The savouries

Returning back to the main subject, apart from some exceptions, the E6xx numbers deal mostly with additives which enhance the umami aspects of food – basically, the savoury taste that we enjoy when eating good meats, fine cheeses and delicious stocks.

The most common additive in this range by far is E621 (monosodium glutamate or MSG), the umami-inducing chemical often vilified by self-righteous health websites and various uninformed people – and this gauche prejudice warrants some comment.

Reality and MSG

food additives

Much research have confirmed very low levels of MSG toxicity in humans – poor research results in the past obtained using test rodents ignored the facts that (i) infant rodents are susceptible to MSG due to differences in their Blood-Brain Barrier (BBB), and (ii) they were injected with doses of MSG impossible to achieve when scaled up to human dietary consumption levels – in any case, humans do not inject themselves with strong solutions of MSG.

However, some asthmatics may react to pure MSG ingested without food and there may be a very small sub-set of humans who may experience a minor allergy to MSG (possibly due to genetics), though no such gene has currently been identified.

Importantly, to date, there are no known human deaths which can be directly linked to the consumption of MSG. There is also no conclusive evidence of any link between MSG and obesity, though it is likely humans might prefer to eat more food enhanced with MSG.

Once digested, the sodium and glutamate molecules in MSG get unlinked and the freed glutamate is chemically equivalent to glutamic acid which is an amino acid found in practically all proteins – the residual sodium is used by the body as an electrolyte or removed via the kidneys.

The body also produces glutamate itself as part of its metabolic processes.

Some confusion may have arisen from the fact that excess MSG in the brain can be an excitotoxin (a compound which kills brain cells) – however, there is no proof that dietary MSG can cross the human BBB and kill cells in the brain (though this is not true of test baby rodents).

As such, all the evidence suggests that MSG is a safe compound when ingested normally with food – therefore the Chinese restaurant syndrome that some people complain about is more likely linked to foods with possibly excessive salt, sugar or other ingredients rather than MSG.

Objections to MSG

By the way, please do not think that I am defending the use of MSG and other umami additives – because I am not.

In many cases, the use of these additives in processed food is primarily to enhance or disguise the use of poor-quality ingredients, and this is clearly objectionable.

However, it is often claimed that MSG disturbingly causes human health issues or brain damage – but this is simply scientifically untrue for the general human population.

The curious umami receptor

The taste receptor for umami is rather unusual in that it is a folded protein which elongates upon contact with MSG. Two other types of chemicals, inosinates and guanylates, can also bind to the extended umami receptor and this stimulates the sensation of umami by up to 15 times.

Hence, for many people, an unfair and wholly irresistible umami bomb would be foods containing all three chemicals – that is the reason why many snack foods tend to contain E621, E627 (disodium guanylate), E631 (disodium inosinate) or perhaps permutations of the following additives.

food additives

The combination of MSG, inosinate and guanylate in this label for a potato-based snack makes it irresistible for many humans.

There are variants of MSG used as additives, such as E620 (glutamic acid), E622 (monopotassium glutamate), E623 (calcium diglutamate), E624 (monoammonium glutamate) and E625 (magnesium diglutamate). For guanylates, other variations are E626 (guanylic acid), E628 (dipotassium guanylate) and E629 (calcium guanylate). And alternatives for inosinates are E630 (inosinic acid), E632 (dipotassium inosinate) and E633 (calcium inosinate).

As a side note, there may be some unspecific evidence of digestive issues for some people related to the potassium-based compounds.

Combination additives are E634 (calcium 5’-ribonucleotides) and E635 (disodium 5’-ribonucleotides) – these are effectively pre-mixed inosinates and guanylates and used where food already contains a lot of natural MSG (such as meat extracts) or added MSG.

The non-savouries

Produced from the gelatin derived from animal bones, E640 (glycine) is a very simple amino acid found in all animal or fish proteins and often sold as a health supplement in its own right (though the claimed benefits are somewhat extravagant). In food, it is used as a bread enhancer by providing nutrients for fermenting yeast.

E641 (l-leucine) is another amino acid used in the same way as E640 to enhance breads and is also sold as a health supplement as it can promote the synthesis of muscle proteins (though it does not seem to improve the muscle mass of older people).

Curiously, this essential amino acid is also sold for use as a weight control treatment – however, a normal diet would provide adequate l-leucine for healthy humans.

E636 (maltol) and E637 (ethyl maltol) can be used to improve the flavour of chocolates, candies and beverages but they are not included in the EU list of allowed additives, though their use appears to be permitted in the United States and other countries.

Again, please note that over-consumption of many additives may lead to possible health hazards and side-effects – and it is simply not possible to cover all potential reactions due to the numbers and combinations of additives.

However, most food additives are regulated in their use and therefore should not cause problems when processed foods are consumed in reasonable amounts by healthy humans.

The next part covers how processed food can be made to taste sweet without the use of sugar – and reviews a bitter scientific controversy which is currently still not wholly resolved to everyone’s satisfaction, even after over 40 years. You should be interested because it very probably affects you or someone you know.