Topic 1 Fruits and vegetables: raw and cooked

Fruits and vegetables lose nutrients and organoleptic characteristics from the moment they are cut. From this moment on they have to use their own vitamins and nutrients to survive. In view of this what we can do is to try to slow down this process of deterioration. To maintain freshness as long as possible, fruits and vegetables must be protected from 2 powerful enemies: light and heat. Both destroy sensitive vitamins such as B vitamins and vitamin C that are in citrus fruits, peppers, tomatoes, broccoli and leafy vegetables. Root vegetables are more resistant and although local distribution is optimal it is less important in terms of preserving their nutrients. Delicate vegetables such as tomatoes, asparagus or salad leaves need special protection. These vegetables are more easily damaged and are therefore less resistant to damage during transport. For this reason it is especially recommended to consume local products as they are transported over short distances and can be consumed within a few days after harvesting. When these foods are transported over long distances, they are usually harvested before they ripen in order to protect them better. Root vegetables such as carrots, turnips and radishes are best kept in the refrigerator. Hard leafy vegetables such as kale also keep better. However, there are vegetables such as potatoes, sweet potatoes, onions and pumpkins that are best kept in a cool, dark, well-ventilated cupboard. The most effective way to extend the shelf life of these fresh products is to control the storage temperature. This temperature depends on where the fruits and vegetables come from. Those from temperate climates are best stored near freezing point. For example, apples. Fruits and vegetables from warmer or tropical climates are damaged at very low temperatures, so it is better to store them at a higher temperature (10 degrees) or even at room temperature. For example, banana skins turn black, avocados darken and stop softening and citrus fruits can develop spots on the skin. Herbs, such as basil, suffer more in the fridge and keep better if exposed to light. Tomatoes or avocados ripen better outside the fridge and can be stored in the fridge when they are already ripe.

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Freezing is the most effective method of stopping the general metabolism of fruits and vegetables. However, most microbes are revived by heating the vegetable because they are resistant to freezing. Freezing that can be done at home can also spoil the texture and cause vitamins and pigments to be lost. If you are going to freeze vegetables or fruit for a long time it is best to first subject them to a blanching process. This consists of placing them in boiling water for 1-2 minutes and then transferring them to ice water to prevent further cooking and softening of the walls of the vegetable. In this way their texture, colour and properties are better preserved.

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Non-heat techniques are best suited to minimise nutrient loss, such as cured, marinated or pickled foods. It is important to wash raw vegetables thoroughly, but do not soak them because some of the vitamins and minerals will be lost in the water. You can also make homemade preserves at home. They are very useful to combine it later in different dishes. In these preserves ingredients are introduced to help preserve food for a longer period of time. One method is to use an acidic medium, such as vinegar, which destroys microorganisms and inhibits enzymatic growth. These methods are more like semi-preserves so cold or sterilization is necessary. Another technique for preserving in fat (confit) can be used for vegetables and also for meat and fish. They are usually sterilized as well.