The secrets inside your saliva

At first glance, saliva seems like a pretty boring thing, just a convenient way to moisten our food. But the reality is quite different, as scientists are beginning to realize. Liquid interacts with everything that enters the mouth, and even though it’s 99% water, it has a profound effect 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 of King’s College London.

Scientists have long understood some of the functions of saliva: it protects teeth, facilitates speech, and establishes a comfortable environment for food to enter mouth. But researchers are now discovering that saliva is also a mediator and translator, influencing how food moves through the mouth and how it triggers our senses. New 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 allows people to feel the saltiness of the chips. It’s not very acidic, which is why a splash of lemon can be so stimulating. Water and proteins from saliva lubricate each bite of food, and its enzymes such as amylase and lipase start the digestion process.

This moistening also dissolves the chemical taste components or taste substances in the saliva so that they can travel to and interact with the taste buds. Through saliva, says Jianshe Chen, a food scientist at Zhejiang Gongshang University in Hangzhou, China, “we detect chemical information about food: flavor, taste.”

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Chen coined the term “oral food processing” in 2009 to describe a multidisciplinary field that relies on food science, physics of food materials, physiological and psychological responses of the body to food, and more, a topic he wrote about in the 2022 Annual Review of Food Science and Technology. When people eat, he explains, they’re not actually enjoying the food itself, but the mixture of food and saliva. For example, an eater can perceive a molecule of sweet or sour taste in a bite of food only if that molecule can reach the taste buds – and for this to happen, it must pass through the layer of saliva that coats the tongue.

That’s not a given, says Carpenter, who points out that soda is sweeter than soda. The researchers hypothesized that this was because the bursting bubbles of carbon dioxide in the fresh soda provided a sour kick that essentially turned the brain away 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 the soda bubbles from flowing between the tongue and palate. Carpenter thinks these backup bubbles could physically block sugars from reaching taste receptors in the language. With carbonated juice, bubbles do not form that would block the sweet taste.