The Science of Flavour

Oxford psychologist Charles Spence has spent many years discovering that little of how we experience flavour is to do with the taste buds in our mouths. In fact smell, vision, touch and even sound dictate how we perceive food. When Spence started studying the sensory science behind flavour perception, it was a deeply unfashionable subject. He says that from ancient times, there was a notion that the senses involved in eating and drinking were less sophisticated than those of hearing and vision. Now, no one questions the validity of the research field he calls 'gastrophysics'. Spence heads the Crossmodal Research Laboratory at the University of Oxford. 'Crossmodal', here, is the investigation of how all the senses interact. Although we rarely realise it, when it comes to flavour perception, all of us have synaesthesia. That is, our senses intermingling so that our brains combine shapes, textures, colours and even sounds with corresponding tastes.

Take a perfectly ripe strawberry: scarlet, heart-shaped and neatly dimpled with seeds. Red and roundness are psychological cues for sweetness. The smell conjures memories we associate with the fruit – summer picnics, and the positive feelings that go with them. Freshness is felt in the first bite: the subtle crunch confirms it, even before we taste the juice. But if you’ve ever experienced the blandness of eating a strawberry while holding your nose, you’ll believe the oft-quoted statistic that flavour is 80% down to smell. In reality, it’s impossible to quantify precisely just how much flavour is delivered through the nose, but it is certainly more influential than the limited number of tastes our tongues pick up: sweet, sour, savoury (otherwise known by the Japanese term, umami), salt and bitter. There’s a growing acceptance that we can also detect less obvious tastes such as metallic, fat, carbonation, water and calcium, among others.

Furthermore, aroma is bound up with memory and emotion. 'The nerves relating to smell go directly to the amygdala,' says Avery Gilbert, a world authority on smell. 'These are areas of the brain involved in emotional response – fight or flight, positive and negative emotion.' This is why food and nostalgia are so entwined: the brain has paired the aroma with the experience. Flavour preferences are learned by positive associations (a great holiday), or negative ones (feeling unwell). On the flipside, while salt and sugar appreciation is hard-wired, we learn to love the bitterness of coffee through sheer force of will (wanting to be grown up). Research findings about the effects of colour, shape, touch sensations and sound on flavour have triggered a trend for sensory seasoning. Want to intensify sweetness? Use a red light bulb, make the food round rather than angular, or play high-pitched music – all of the above have increased the perception of sweetness in studies. The sounds of crinkly packaging, and crunchy food, increase perception of freshness. Want more savoury? Put some low-pitched music on.

When it comes to dinnerware, the heavier it is, the more viscous, creamy and expensive the food served is perceived to be. And if you hold the bowl while eating, you’ll feel fuller, sooner. There’s little evidence as to why this is the case, but ingrained associations are often suggested. Young people associate blue with raspberry-flavoured drinks. Red often signifies ripeness in nature. It feels intuitively right that jagged shapes and sounds would go with bitterness, whereas sweet is comfortably round. Big food brands use these associations to surreptitiously increase appeal. Meanwhile, chefs love them because they heighten the senses. 'Cooking is probably the most multisensual art. I try to stimulate all the senses,' renowned Spanish chef Ferran Adria has said. However, it isn’t only big chefs and the food industry who can put the science to use. It can demystify appetite and flavour for everyone, inform and inspire us to eat well, while offering a window into the bigger picture of how our senses and minds work.