Applied food science: using food industry by-products
Food science brings together different disciplines, such as engineering, biology and the physical sciences, to study the nature of food, food deterioration and food processing. Food scientists also discover how food can be improved for consumers and create exciting new products.
The food industry generates large amounts of waste, or by-products. One area of food science seeks to address this problem by identifying functional components of by-products and creating new products that harness them.
There are many examples of how food by-products can be used to improve our health:
- Pomegranate peel contains antibacterial properties
- Aloe vera is used in many medicinal and therapeutic remedies
- Rice bran, a by-product of rice production, is high in dietary fibre which keeps our digestive systems healthy
For more information on these examples, check out the article from the International Journal of Waste Resources in the See Also section.
In this step, we’ll look at one key example of a useful by-product and how it’s made.
Using fruit pomace to make pectin
Pectin is a gelling and thickening substance made from pomace (solid remains of fruit or vegetables after pressing for juice or oil), which is a by-product of creating fruit juice. This means that no part of the fruit is wasted. Its properties were discovered over 200 years ago, but it wasn’t until the early 20th century that its practical uses in food production were identified.
Pectin is present in many of the products you might consume regularly. It’s used in jam, marmalade and jelly to thicken them, and in confectionery such as jelly candies to give them a good bite and flavour. It can also be used as a fat substitute in low-fat foods, and can stabilise yoghurt drinks, juices and low-sugar soft drinks and improve the way they feel in your mouth.
So, how does leftover apple peel get turned into something you spread onto your toast in the morning?
You can see a diagram of this process in the downloads section below.
- Since apples and citrus fruits are only harvested at certain times of the year, the first step is to dry the fruit residues so that they can be stored. This means pectin can be produced all year round.
- Pectin is a structural molecule of the plant cell wall. An extraction process is used to make it soluble (dissolvable in water), and then the water containing the pectin is separated from the (now pectin-free) fruit pomace.
- The water containing the pectin is filtered to remove impurities, and then concentrated to pure liquid pectin.
- Pectin is insoluble (doesn’t dissolve) in alcohol. With a special process using alcohol, the pectin is separated from its liquid solution and washed. This is called precipitation.
- The pectin obtained through precipitation is then pressed, dried, ground and then sieved to remove any inconsistencies.
- The pectin is mixed in a special mixing facility to standardise the batch. It’s either mixed with itself, other pectin batches, or other substances (neutral sugars like dextrose or sucrose and buffer salts like citrates, carbonates and phosphates). The final product is called the standardised pectin.
- Before the pectin can be used in food products it needs to go through detailed laboratory tests to make sure the quality is high enough.
- The pectin is examined and put through various tests. Not all pectin is suitable for every kind of use, so pectins need to be standardised to a particular gelling strength, melting point and viscosity depending on what product they’re going to be used for.
- If all the tests are passed, the pectin is ready to be packaged, sold and distributed to various industrial sectors. As well as food products, pectin is used in cosmetics (for example, shampoos and conditioners) and pharmaceutical products (for example, gel capsules). That’s a lot of uses from a by-product that otherwise would have gone to waste!
Pectin isn’t the only use for fruit waste, though. For more examples, see the ‘Waste to Wealth’ article in the See Also section.
In the next step, you’ll see a case study of how pectin is being used to create exciting and unusual food products.
We would like to thank Herbstreith & Fox for providing the information and diagram for this article.
© University of Cambridge and Herbstreith & Fox