Feature articles

Our taste for sweet

Prof Russel Keast.jpg

We asked Professor Russell Keast from the Centre for Advanced Sensory Science Deakin University all about our taste for sweet.

Why do we have a fondness for sweet things?

From an evolutionary perspective sweetness signals a readily available source of energy. Sweetness and the hedonic response to it were vital for species survival.

Is everybody's perception of sweet the same?

No, there are large individual differences in how intense we experience sweetness. One teaspoon of sucrose in a cup of water will be mildly sweet for one person and intensely sweet for a second person. This is normal.

Does our taste preference change with age?

Taste preference change with experience, and experience usually comes with age; so in a way the statement is correct, albeit indirect.

Does the physical form of food/beverage affect sweet taste perception, ie liquid vs solid etc?

Certainly; the food matrix has a large effect as the sugars must dissolve in saliva to access the taste receptors. If the sugars are bound in a solid matrix, or unavailable to taste receptors then there will be no taste perception.

Is our individual liking for sweetness inherited?

Liking for sweetness is innate and sweetness is hard wired, we are born with an appetite for sweet; a recent publication in Nature provide further insight. Using a rodent model and activating the sweet taste regions of the brain, they behaved like the water was sweet. It shows that taste is formed in the brain and the signals sent are merely electrical. It is the brain that decodes and provides meaning.

What does 'bliss point' mean? Do manufacturers formulate to meet it?

The bliss point is the point of maximal liking; but the bliss point will vary between individuals and it can become complex. For example I may like something very sweet and my sense of taste may also be quite sensitive to sugar, that is I may find low concentrations intensely sweet. Conversely you may prefer moderate sweetness and have an insensitive sense of taste. In this case we may have similar bliss point concentration of sugar; or you preferring moderate sweetness may need a higher concentration of sugar to reach your bliss point than I need to reach mine. I believe manufacturers produce foods we like, so in a way they aim for a point of maximal liking for the general population – as a consumer that is what you want. But what we want is not necessarily good for health!

Can our liking for sweet be modified? (Are we slaves to our primal sensory appetite or can we behaviourally re-trained?)

We can (see answer below) but behaviour tends to revert to what we know.

Can our sweet taste be tricked by sugar alternatives? Can some people be more successfully tricked by sugar alternatives than others?

I have recently changed my opinion on this. I did believe the disconnect between calories and sweetness would be overcome by our biology. However, the weight of evidence suggests high intensity (HI) sweeteners are effective at reducing calories, with some limitations. Generally we remember the sweetness profile of sucrose and any HI sweetener is easily distinguishable from sucrose, mostly due to a different time-intensity profile differences from sucrose, but they can also have side tastes. An individual who is more susceptible to experiencing intense bitterness may have a strong aversion to some HI sweeteners due to bitterness.

There is a trend toward sugar-free foods and diets; what are the sensory implications of this approach?

A very recent study published in AJCN involving my former colleagues at Monell Chemical Senses Center in Philadelphia put people on a low sugar diet and after 3 months the participants experienced greater levels of sweetness sensitivity, but being on the low sugar diet had no effect on their most preferred level of sugar. This has previously been shown for salt and my research group have demonstrated a similar effect for fat. In this way the taste system is becoming more sensitive to sugar in times of scarcity. However, after the intervention finished the participants quickly reverted back to normal sugar diet and their sweet perception reverted to pre-diet state.

Many food companies are reducing the sugar content of their products; what advice would you give them?

Keep it up. Small reductions are worthwhile, but large reductions can cause problems for regular consumers. Sugar is perhaps the easiest to effectively reduce from a taste perspective because of the emergence of HI sweeteners – but as I previously stated, HI sweeteners come with their own problems. The development of a HI sweetener with the profile of sucrose would greatly help. The best HI alternative at this stage is sucralose.

Why do you think 'healthy' food products (lower in saturated fat, salt & sugar; higher in fibre) are perceived as tasting bad/worse?

This is interesting. One of the things a food manufacturer should avoid is actually saying reduced salt/sugar/fat as it changes the mindset of the consumer. We did a study with salt where we had a food presented with a normal label or a Heart Foundation label and stating 30% less salt. Although the actual foods were identical, the labelled reduced salt food was found less pleasant. Perhaps it is the appetitive nature of the fat, salt sugar that is so persuasive in consumers' minds. Consumers believe removing these ingredients from what is optimal, while maybe creating a more healthy option (although not always) is compromising flavour. To get acceptance a person must prioritise health over flavour and flavour often wins that battle.

Is it possible to produce foods that taste good as well as being healthy, or is there always a taste compromise?

It is absolutely possible to produce tasty healthy foods, and there are hundreds available currently. In my opinion the problem is with portion size and frequency of consumption, we just eat too much energy. At our current state of knowledge, removing approximately 10% of fat, salt and sugar is possible without overly compromising product quality. Anything above this requires advanced thinking in product design and often what could be done in a lab setting may not be feasible when scaled up in production. Our DNA is constructed to maintain mechanisms that encourage consumption of fats, salts and sugars so it will take revolutionary thinking to make a significant impact. Much research has focussed on the balance between liking (encouraging consumption) and fullness (brake on consumption). We need a food supply that is liked, therefore current levels of salt, sugar and fat in foods have a role, but we need strong focus on the brake mechanisms in future years.

NEXT: Goodbye tick, hello stars 


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