Dried asparagus is not something you immediately think of but given that we are quite familiar with dried mushrooms, dried tomatoes and other dried vegetables I don’t see why not. If you can believe everything you read (ie I have nothing to back this up!) the Greeks and Romans preserved their asparagus for winter use by either freezing or drying it.
Drying is a way of preserving some of your asparagus glut for use later in the year. Whilst some of the nutrients will be lost (eg vitamin C is lost in the blanching part of the process) other nutrients eg Vitamin A, riboflavin, niacin and thiamine are all fairly well retained whilst iron is not destroyed by the drying process.
Dried asparagus is ideal to use in casseroles and soups but experiment with it and see what works for you!
Before drying you need to blanch your asparagus spears. Blanching helps to prevent undesirable changes in flavour and texture during storage and relaxes the tissues so that the spears dry more quickly. It also enhances the destruction of potentially harmful bacteria. Follow this simple process then return here to proceed with the drying process.
You will need to sort out drying trays. You can buy special drying equipment but unless you plan on getting very keen on food drying something much more simple will suffice. You need to enable good air-flow around the asparagus and avoid any reaction with the food trays.
Cake racks or baking trays with cheesecloth stretched over them will work well. As asparagus is not acidic you can probably get away without the cheesecloth but it will ensure no reaction with your racks etc. Any plastic trays with perforated bottoms or slatted wooden racks will also work well.
Before drying wash the trays in hot soapy water and dry thoroughly to ensure there is no danger of contamination. You may like to try a light coat of fresh vegetable oil or non-stick substance on wooden slats to make them easier to clean. Make sure your trays are about 1 ½ inches smaller than your oven or drying space to ensure good air circulation. If you stack your trays allow at least 2 inches between trays.
Arrange the blanched asparagus on the trays ideally in a single layer although you can try layers up to 1/2 inch deep. Obviously the more spread out they are the more easily they will dry.
To dry the asparagus in an oven ideally you want a temperature of 140 degrees F. This may not be that easy to achieve. You may need to experiment. Setting the thermostat to 140 – 150 degrees F and leaving the door slightly open to allow moisture to escape may be the best method. Conventional ovens may not maintain a consistent temperature at such a low heat. If you have a slow oven try using this.
Watch the asparagus for scorching and turn the trays and switch their position every couple of hours to keep the drying even.
Dry for 6 – 10 hours! If you dry them too fast the outer skin can go hard preventing moisture from escaping. Conversely if you dry too slowly bacterial growth can be encouraged. Allow at least 3 inches of clearance between the top and bottom of the oven. If the spares are more than one layer deep you will need to turn them. I would suggest trying to stick to one layer only.
The asparagus is dried when it is leathery and brittle.
Once the drying is complete leave the asparagus in the oven for an hour or so to return to room temperature then pack in very clean air tight containers.
Your dried asparagus should keep from 3 – 6 months. It will keep longer if you can keep it in a reasonably cool place. Fruit keeps twice as long at 60degrees F as it does at 80 degrees F. Every time you open the container you will allow some moisture in and the product will deteriorate so pack it in the sort of quantities you are likely to use. Small air tight bags may be good for this or small air tight plastic containers. If you use clear plastic bags and you see any moisture on the inside of the bag the drying process has not completed or you put the “dried” asparagus in before it had cooled properly.
Keep the dried asparagus in the cool and dark as far as possible.
If you get really keen on drying food, and dried asparagus works well for you, you could try a special dehydrator oven.
These are usually thermostatically controlled electric dehydrators which can be used for home food drying. They cost typically from £50 to £150 and can be used to dry fruit, vegetables, beef jerky etc. As with most things you pay more for more features. Eg. Thermostats and timers.
The Colorado State University - University Co-operative Extension – Food and Nutrition Series, Preparation - Drying Vegetables No. 9.308 by P. Kendall, P. DiPersio and J. Sofos has been a useful source of information on drying asparagus and also includes information on drying all sorts of other vegetables.
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Basics of how to cook fresh asparagusstart by looking at How to Cook Asparagus first for some background information on a range of cooking methods.
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