Around 7.2 million tonnes of food and drink are thrown away every year in the UK [1]. This is often due to food going off or reaching its best before date before it is used. Fresh fruit makes up 13% of the food thrown away, and the amount of this that could have been avoided is about 0.58 million tonnes per year [2]. This could be done with a home compost system. Shop-bought fruit is often grown abroad and imported, and even if it is locally grown, materials and energy used to produce, package and transport it, as well as the food itself, are wasted when it is thrown away. Home-grown or wild fruit is only available when it is in season, and if a lot is produced or collected it can go off before it’s all used, potentially adding to landfill and wasting any resources used in growing and harvesting it.
There are several ways of treating fruit that isn’t going to be eaten straight away, including freezing, preserving or drying. Freezing is a quick and easy way of preserving food, but might not be ideal if freezer space is limited. Methods of preserving such as jam-making can take time, effort and equipment. Drying is a simple process and special equipment is not essential.
It is worth considering that drying, as with any preservation method, will remove some of the nutrients from fruit [3]. Fruits that brown easily, such as apples, can be pre-treated by dipping in a mixture of water and lemon juice to prevent this [3, 4] and fruits with tough skins should be “cracked” (by dipping in boiling water for 30-60 seconds, then dipping in cold water) [3] or pricked so that they don’t burst during the drying process. Dried fruit is ready when it is chewy, rather than brittle [3, 4]. There are various methods that can be used to dry fruit, depending on the time and equipment available.
Air or sun drying
Air and sun drying use no extra energy, but might not be a viable option in the UK, even in summer as high temperatures and low humidity are needed. If conditions are suitable, fruit can be air dried by spreading it out on trays or placing it in a pot (stirring regularly) and covering it with netting to keep birds off, then placing it in the sun for several days [5], or by hanging cored or sliced fruit on string [4]. Alternatively, a sun dryer can be built with wood and mesh [6].
Using an oven or microwave
Perhaps the most straightforward way of drying fruit, particularly if it is being done infrequently and in small batches, is in a very cool oven or microwave. For an oven, about 40 oC (100 oF) is the ideal temperature; although most oven controls don’t go that low, they can still be used on the lowest temperature possible to save energy and avoid cooking or burning the fruit.
Alternatively fruit can be dried when the oven is cooling down after cooking, which also saves energy as the oven isn’t being used specifically for drying the fruit. Some fruit will need 6-8 hours to dry completely, so will need to be dried in several stages and stored in between if using a cooling oven; don’t leave it until it’s almost off to start this process.
The time needed will depend on the fruit, and whether the oven has a fan or not, so progress will need to be checked regularly. Small fruits can be dried whole, while larger ones should be thinly sliced, or pitted and placed with the pitted side up. Individual pieces of fruit should not touch each other, as they need as much air to circulate around them as possible. Instructions and approximate drying times for common fruits have been supplied online by Colorado State University [3]. The door can be left slightly open (or opened periodically) to release moisture and allow adequate ventilation [7].
Drying fruit in a microwave is quicker, but not suitable for more delicate fruits due to the higher heat levels compared to a very cool oven [8]. This method is also only suitable for small batches of fruit (but is probably more energy efficient than leaving a fan oven running for 8 hours to dry only a small amount, depending on the energy ratings of the appliances). The microwave should be used on the defrost setting, and the fruit spread out and turned regularly – the drying process should take 30-45 minutes [8].
Using a dehydrator
Fruit can also be dried in dehydrators, which are available in a range of sizes. They should be placed somewhere with good air circulation, so that the moist extracted air is not reused in drying the fruit [9]. Again fruit should be spread out on the trays, without touching, and trays could be rotated to ensure even drying – times will vary according to fruit, and might be indicated by the manufacturer instructions [10]. Dehydrators tend to be low wattage [11], but they do need electricity to power them, and unlike a cooling oven which would have been used for cooking anyway, they are only usable for the purpose of drying food.
Dried fruit should be stored in dry (glass jars, for example, can be dried in a cooling oven to make sure all the moisture has been removed), airtight containers. It can be used and eaten dried, or rehydrated if necessary by placing in boiling water [3, 9]. An online calculator is available to estimate the weight of food after drying from its pre-drying weight [12]. Dried fruit can be added to cereals, yoghurt, cakes, biscuits and other meals and recipes, combined with herbs and spices to make tea infusions, or eaten alone.
[1] http://www.wrap.org.uk/retail_supply_chain/research_tools/research/report_household.html
[2] www.wrap.org.uk/downloads/Household_Food_and_Drink_Waste_in_the_UK_Nov_2011.39e8bf7a.8048.pdf
[3] http://www.ext.colostate.edu/pubs/foodnut/09309.html
[4] http://www.wikihow.com/Make-Dried-Fruit
[5] http://www.ehow.com/how_2083871_dry-fruit.html
[6] http://www.ehow.co.uk/how_7921776_build-nonelectric-food-dehydrator.html
[7] http://www.allotment.org.uk/allotment_foods/drying-food/index.php
[8] http://www.ehow.com/how_5103996_dry-fruit-microwave.html
[9] http://www.fruitexpert.co.uk/DryingFruitFromYourGarden.html
[10] http://www.ehow.com/how_6393689_dry-fruits-vegetables-dehydrator.html
[11] http://www.discountjuicers.com/dehydratorcompare.html
[12] http://www.food-dehydrator.com/calculator/food-dehydrator-weight-calculator.aspx
