PROCESSING OF FRUIT AND VEGETABLES
Fruit and vegetables are fresh, water-rich foods and important sources of vitamins and minerals. However, this very richness also makes them highly perishable, meaning they spoil easily if not stored properly.
For this reason, after harvesting, many fruits and vegetables undergo processing to preserve their flavour, nutritional value and food safety for longer.
Why transform?
The processing of fruit and vegetables has three main objectives:
- Preventing food waste by making use of produce that is not sold fresh.
- Extend the shelf life, keeping the product safe for weeks or months.
- Develop new food products, such as juices, jams, soups, sauces or healthy snacks.
Initial stages
Once harvested, the fruit and vegetables are sorted, washed and cut.
They may follow different processing routes, depending on the type of end product.
Main processing methods
Freezing is one of the most commonly used techniques. Fruit and vegetables are rapidly cooled to temperatures below –18 °C, turning the water into ice and halting the growth of microorganisms. Before freezing, vegetables are often blanched (immersed in hot water for a few minutes) to inactivate enzymes and preserve colour and flavour.
Freezing allows for good preservation of vitamins and antioxidants, although some losses may occur, and the produce can be used directly in soups, stir-fries or smoothies.
Drying removes water from food, reducing water activity and inhibiting the growth of mould and bacteria. It can be carried out in various ways:
- In the sun or in warm air, a traditional method used for figs, tomatoes and aromatic herbs;
- By freeze-drying, which removes water at low temperatures, thereby better preserving the flavour and vitamins;
- Using microwaves or infrared, which are faster and more energy-efficient modern techniques.
Dried products, such as dried apples, sun-dried tomatoes, onion powder or dried herbs, have a long shelf life and retain many of their nutrients.
Thermal preservation is used for fruit and vegetables cooked in syrup, vinegar, brine or tomato sauce. Heat destroys microorganisms and enzymes, and the hermetically sealed container prevents air from entering and prevents further contamination. Jams, jellies and preserves are another example, where sugar acts as a natural preservative.
JAM-MAKING PROCESS
| Stage | Description |
|---|---|
| 1. Select ripe fruit | It should be ripe, but not too ripe, as the pectin content decreases with over-ripening. |
| 2. Prepare the fruit | Wash thoroughly and remove any peel, stones, stalks or seeds as required. |
| 3. Add water and acid (e.g. lemon juice), if necessary | Add water and acid (e.g. lemon juice), if necessary |
| 4. Add sugar | Stir until dissolved. A high concentration of sugar helps to preserve the mixture. |
| 5. Bring to the boil | Heat until it reaches a vigorous, sustained boil. The bubbles should not disappear when stirred. |
| 6. Test the gel point | Thermometer → 105°C OR the wrinkle test on a cold plate. |
| 7. Bottling | When it reaches the right consistency, pour it into sterilised jars and seal them tightly. |
Fruits such as oranges, apples, mangoes and strawberries can be processed into juices, pulp and concentrates. The process involves juice extraction, filtration, pasteurisation and packaging. Many juices are also enriched with vitamins or combined with vegetables such as carrots and beetroot, creating more balanced drinks.
During processing, by-products such as peel, pulp and seeds are produced. At present, many by-products are put to good use and reused:
- The peels can be used to produce organic compost or bioplastics;
- The pulp and bagasse can be processed into juices, dietary fibre or animal feed;
- Some waste is used to generate biogas and energy.
These practices form part of the circular economy, helping to reduce the food industry’s environmental impact.
A tip for planning your meals
Processed foods, such as frozen vegetables, dried fruit, ready-made soups or natural juices, are good options when chosen carefully.
Opt for products with no added sugar, salt or colourings, and, wherever possible, locally produced and seasonal produce.
This way, you can make the most of food technology whilst contributing to a balanced and sustainable diet.
FOODWISELAB Challenge
To understand how fruit and vegetables can be processed in different ways, and to recognise how the degree of processing affects their nutritional quality, flavour and impact on health.
FROM FRESH TO PROCESSED: THE PROCESSING OF FRUIT AND VEGETABLES