You must have had the experience whereby food and drink seem to lose their taste when you have a head cold and your nose is blocked. However, the thing is that under such conditions your taste buds are operating just fine. It is your sense of smell that has temporarily stopped working. This everyday example helps, I think, to illustrate just how important the sense of smell is to our perception and enjoyment of the foods we eat. The only thing that the taste buds on your tongue actually tell you about are the sweet, salt, sour, bitter, and umami (the mysterious fifth, proteinaceous taste associated with monosodium glutamate - MSG) notes in a food. Everything else, the caramelised, meaty, creamy, floral, herbal, fruity, and burnt notes you get while eating (or, for that matter, baking) all come from the volatile aromas picked up by your nose.
One of the most amazing tricks played by our minds is to convince us all that the food attributes detected by our noses actually originate from the food we can feel moving about in our mouths (this phenomenon is known as ‘oral referral’). In fact, many researchers believe that as much as 75-95% of what we think we taste actually comes from the sense of smell.1
Visual cues are also really important in terms of setting our flavour expectations and hence our experience of flavour. After all, we nearly always look at the foods that we are about to eat first. Colour cues, for example, provide clues about the likely taste and flavour of food and drink. Add some odourless, tasteless red food dye to a white wine and even the wine experts can be fooled into thinking that they are tasting a red wine!2 One sees very similar results emerging from those studies in which cakes and pastries have been miscoloured. A rich dark brown slice of chocolate cake will, for instance, likely taste much more chocolatey than a white slice of chocolate cake.
For me, though, it is sound that really deserves the title of the forgotten flavour sense, especially when it comes to baked goods. If you don’t believe me, just think about how unappealing a soggy crisp is.3 The nutritional properties haven’t changed, but the sound most certainly has. In fact, most of us find crispy, crunchy, and crackly foods pretty much irresistible. But why, you have to ask yourself? Well, my suspicion is that our brains have learned that louder foods generally signal fresher foods, be it fruits, vegetables, or baked goods. Crisper sounds may also signal more accessible energy from cooked foods such as a meat roast.
Intriguingly, the latest research shows that crispier, noisier foods tend to retain their flavour for longer when we eat them too.4 Back in 2008, Max Zampini and I were awarded the IG Nobel prize for nutrition for our ground-breaking work showing that we could enhance the perceived crispness and freshness of potato chips (or crisps) by 15% simply by boosting the sound of the crunch when people first bit into them.5
The oral-somatosensory feeling of foods in the mouth also plays a key role in our enjoyment. Just think of the tactile cues associated with savouring a spoonful of ice cream, say, or a piece of chocolate as it melts slowly in your mouth. Temperature, texture, viscosity, and mouthfeel, all constitute a key part of the enjoyment associated with consuming many everyday foods.6
What may be even more surprising, though, is that the feeling of food in the hand can also influence our perception of food in the mouth. In one study, stale and fresh pretzels were cut in half and then glued back together. Sometimes, people would bite into a fresh pretzel while holding a stale pretzel end, or vice versa. Remarkably, the feel of the food in the hand was found to influence people’s perception of the food in their mouth.7 Given that the feel of the packaging can exert a similar influence over the consumer’s in-mouth experience, you may now understand why the larger food companies are starting to think much more carefully about the tactile attributes of their packaging.
In conclusion, the perception of flavour is one of the most multisensory of our experiences, as it does involve taste and smell, obviously, but also touch, sight, and even sound. By understanding the rules by which the consumer’s mind combines the various sensory cues in everyday food products, such as bakery items, the hope is that we can start to deliver foods that more effectively stimulate the senses.
1. For a review, see Spence, C. (2015). Just how much of what we taste derives from the sense of smell? Flavour, 4:30. https://flavourjournal.biomedcentral.com/articles/10.1186/s13411-015-0040-2.
2. For a review, see Spence, C. (2015). On the psychological impact of food colour. Flavour, 4:21. https://flavourjournal.biomedcentral.com/articles/10.1186/s13411-015-0031-3.
3. Weiss, G. (2001). Why is a soggy potato chip unappetizing? Science, 293, 1753-1754.
4. Luckett, C. R., Meullenet, J.-F. & Seo, H.-S. (2016). Crispness level of potato chips affects temporal dynamics of flavor perception and mastication patterns in adults of different age groups. Food Quality & Preference, 51, 8-19.
5. These prizes are awarded annually for research that first makes you laugh, and then makes you think. See http://www.improbable.com/ig/; Zampini, M., & Spence, C. (2004). The role of auditory cues in modulating the perceived crispness and staleness of potato chips. Journal of Sensory Science, 19, 347-363.
6. Spence, C., & Piqueras-Fiszman, B. (2016). Oral-somatosensory contributions to flavor perception and the appreciation of food and drink. In B. Piqueras-Fiszman & C. Spence (Eds.), Multisensory flavor perception: From fundamental neuroscience through to the marketplace (pp. 59-79). Duxford, CB: Elsevier.
7. Barnett-Cowan, M. (2010). An illusion you can sink your teeth into: Haptic cues modulate the perceived freshness and crispness of pretzels. Perception, 39, 1684-1686.