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  • What happens when you chew? How can chewing affect how quickly energy is released from different foods?

    What happens when you chew?

    Chewing breaks foods into smaller pieces so they can be swallowed. Chewing also adds saliva, which coats the food in digestive enzymes, water and mucus. Saliva contains the digestive enzyme amylase that breaks down starch into smaller sugars, like glucose and fructose.

    The 'chew and spit' test

    How do you measure the size of bits of chewed food? There is a simple way of doing this. People are asked to chew their food and spit it out when they would normally swallow it. The chewed food particles can then be separated by size using a stack of sieves with different sizes of mesh. It’s messy, but it works!

    However, researchers at Plant & Food Research made a machine that can replicate some chewing actions.

    Particle size matters

    Most people chew the same foods to about the same size. This is important because the size of the food particle affects the time it takes to digest. Larger particles take a long time to digest, which means energy is released slowly from the food and it has a lower glycaemic load. Smaller particles are quickly digested and have a higher glycaemic load.

    What changes the way we chew?

    The food structure, density, shape and surface area will all affect the way we chew food. It also affects how we digest food. For example, pasta and white bread both have similar ingredients, but energy is released from these foods at different rates. This is because pasta is wet and slippery and isn’t chewed much before it is swallowed - it takes longer to digest so it has a low glycaemic load. White bread is drier and is chewed a lot before it is swallowed. The smaller the particles the faster it is digested so it has a high glycaemic load.

    Changing chewing

    Plant & Food Research scientist Dr Marco Morgenstern researches ways to alter the rate that energy is released from foods. One way to do this is to vary food structure and composition, as this changes the amount a food is chewed and the rate at which energy is released from the food. Dr Morgenstern says that the way someone chews food is more dependent on the food’s properties rather than the individual doing the chewing.

    Related content

    Chewing is the first step of ingesting food. To learn more about mechanical and chemical digestion in the human body, read Digestion chemistry – introduction. This article has links to numerous articles and media resources regarding the digestive system.

    Useful link

    To chew or not to chew, what suits you? profiles the Plant & Food Research study about chewing and energy release.

      Published 1 February 2007, Updated 29 September 2017 Referencing Hub articles
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