At first glance, saliva seems like a pretty boring substance, just a convenient way to moisten our food. But the reality is quite different, as scientists are beginning to understand. Liquid interacts with everything that goes into the mouth, and even though it is 99% water, it has a profound influence on the flavors – and our enjoyment – of what we eat and drink.
«It’s a liquid, but it’s not just a liquid,» says oral biologist Guy Carpenter from King’s College London.
Scientists have long understood some of the functions of saliva: it protects teeth, facilitates speech, and creates a welcoming environment for food to enter the mouth. But researchers are now discovering that saliva is also a mediator and translator, influencing how food moves through the mouth and how it engages our senses. Emerging evidence suggests that interactions between saliva and food may even help shape the foods we like to eat.
The substance is not very salty, which makes it possible to taste the salty taste of a potato chip. It’s not very acidic, which is why a lemon spritz can be so uplifting. The liquid’s salivary water and proteins lubricate every bite of food, and its enzymes such as amylase and lipase trigger the digestion process.
This wetting also dissolves the chemical components of taste, or taste buds, in the saliva so that they can travel and interact with the taste buds. Through saliva, explains Jianshe Chen, a food scientist at Zhejiang Gongshang University in Hangzhou, China, «we detect the chemical information of food: the flavor, the taste.»
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Chen coined the term «oral food processing» in 2009 to describe the multidisciplinary field that draws on food science, the physics of food materials, the body’s physiological and psychological responses to food, and more, a subject about which he wrote in the 2022 annual review. of food science and technology. When people eat, he explains, they are not savoring the food itself, but a mixture of food and saliva. For example, an eater can only perceive a molecule with a sweet or sour taste in a bite of food if that molecule can reach the taste buds – and for that it must pass through the layer of saliva that covers the tongue.
It’s not a given, says Carpenter, who points out how flat soda tastes sweeter than sparkling soda. Researchers had assumed it was because popping carbon dioxide bubbles in cold soda produced an acid hit that essentially distracted the brain from the sweetness. But when Carpenter and his colleagues studied the process in the lab in a kind of artificial mouth, they found that saliva prevented soda bubbles from flowing between the tongue and the palate. Carpenter thinks these blocked bubbles could physically block sugars from reaching taste receptors on the tongue. With flat soda, no bubbles build up to block the sweet taste.