Preserving food – drying / dehydrating
Before the invention of refrigeration, dehydration was one of the most reliable means of preserving food. The process of dehydrating, as the name implies, removes water from fruits, vegetables, and meats. Without water, bacteria and fungi (in the form of yeasts and molds) cannot breed. The result is brittle, perfectly preserved, shelf-stable food that does not require refrigeration. It’s a great solution for gardeners with very little freezer space, and in some cases, the end product is better than its frozen counterpart.
There are several ways to dehydrate your harvest, including solar drying and electric dehydrators. From the simplest act of hanging a bundle of herbs upside down to dry in the garage to the more elaborate contraptions like homemade solar food dryers, dehydration is relatively straightforward and inexpensive to do at home. Let’s look at the possibilities.
For simple herbs such as sage, bay, thyme, oregano, dill, and rosemary, drying is as easy as spreading them out on a screen or paper towel in a room with plenty of air circulation. They may take up to a week to fully dry, but after they become brittle and crumbly you can grind and store them in a glass jar for use in savory dishes. This method of drying should be done out of direct sunlight.
Home-scale food dehydrators are readily available for the task if you’re willing to spend the money. These enclosed units come with five to nine stacking trays that sit compactly on a kitchen counter. You simply load the trays, close the unit, and plug it in. Some dehydrators have timers so you don’t forget about your project and end up with unpalatable food pebbles. Good-quality electric dehydrators will cost a couple hundred dollars, but loyal preservation folk will say it’s worth the expense.
Many gardeners and cooks use their oven to dry their harvest. The only caveat is you have to have an oven that can hold temperatures below 200°F. The ideal temperature for drying food is 140°F (though raw food advocates opt for temperatures below 115°F). Some ovens can accomplish this temperature with only the pilot light. If you have an electric oven that begins at 200°F, this may not be an option for you.
Using the power of the sun to dry food is preferred by many gardeners because the sun’s energy is free—there’s nothing to plug in. It can be as simple as laying screens of food out on a table or rooftop and covering them with additional screens to keep the bugs away. You can go a step (or two) further by building a solar food dryer to harness the sun’s power and incorporate convection, or consistent air current, into the mix. Why convection? Because food dries faster with proper air circulation. Electric dehydrators have a fan to circulate air during the drying process, but the air is simply blasted over the surface of the food. Solar food dryers use convection—heat transfer by the circulation of fluids (in this case, air) to speed the drying process. What would ordinarily take two days to dehydrate in an electric dehydrator can take only one day in a solar unit, depending upon its design.
Regardless of your chosen method of dehydration, it’s a good idea to know which fruits and vegetables dehydrate the best. Here’s a quick starter list of suitable crops to try:
Peppers, chile and sweet
Corn, sweet and popping
Onions (leeks, green, bulb)
Zucchini (sliced very thin)
Stone fruits (apricots, peaches, plums)
When it comes to drying fruit, other factors come into play. Commercial companies use sulfites to preserve color when drying, but home gardeners tend to shy away from preservatives. Instead, some soak fruit slices for five minutes in a mixture of vitamin C powder and water. Drying times vary, depending on the thickness and moisture content of the food. The world of food preservation is immense, and this book doesn’t venture to cover every trick of the trade. If you are new to dehydrating, there are plenty of in-depth dehydrating books out there. Check the Bibliography and Resources section for a few suggestions.
SOLAR FOOD DRYERS
Eben Fodor’s book Solar Food Dryer is filled with detailed charts on how to capture the sun’s energy for preserving food. It has step-by-step instructions for how to build the most efficient solar food dryer possible, and as a bonus, he does it all with recycled materials.
You can too. Here’s how:
1. Get the book. Read it cover to cover (it’s just over 100 pages). His instructions detail the involved process, but if you choose to accept this mission, the results are completely satisfying.
2. Start scrounging around for wood scraps in the neighborhood, on Craigslist, and nearby construction sites (no stealing, please, but most companies are willing to give you discards). If you have access to Freecycle (a local recycling forum for discarding and acquiring used stuff), look for additional materials there.
3. Go to the hardware store to get any parts you couldn’t find recycled (mostly screws and brackets). There is an optional electrical component to the project as well, which allows you to plug in two 200-watt light bulbs at night to keep the process going. It calls for porcelain light sockets (they withstand high temperatures). Most hardware stores in the United States do not carry the size needed for this project, though Fodor reports that Ace Hardware and True Value Hardware stores do. Alternatively, look online for 9880 Leviton Medium Surface Mount Porcelain Light Sockets. You will also need to locate food-grade screen material, which is not made from vinyl like regular window screening.
4. Now put on your math cap. Recalculate the dimensions in Fodor’s book to account for your recycled materials. His glass window was 273⁄4” × 30″. Let’s say yours is long and narrow instead: 48″ × 15″. You will need to adjust the dimensions for length and width on all related parts, and reduce your screen size to 2″ smaller than your window. Keep in mind with narrow windows, the angle of the glass (to capture the sun’s rays) changes.
5. Cut all materials with a table saw. Get help from a carpenter friend or family member if you are clumsy or fear losing a finger. Always wear protective goggles and use a push stick. Note: Don’t use plywood for legs or rear braces; use solid wood.
6. Assemble your solar food dryer. Start with the end that holds the legs and interior rails for holding drying trays and a metal absorber plate.
Connect the ends with the cross pieces to create a standing frame. Add the bottom panel to hold the frame square. This may require another set of hands to hold it in place while drilling in screws.
7. Install the electrical backup lighting (if using) to ensure continued drying overnight and when temperatures drop due to clouds or fog. This is highly recommended if you live in an area with coastal marine layer conditions. The lighting elements can keep the unit between 90°–120°F overnight, depending on wattage.
8. Cut, shape, paint, and install the absorber plate. Standard thin sheet metal works great for this project. It cuts easily with tin snips. Making the proper folds in the design can be a little challenging, but if you enlist the help of a friend, it will be much easier to bend sheet metal in a specific place without the use of heavy machinery (hint: use the edge of a piece of wood and four hands).
The book says to paint the sheet metal with high-temperature stove paint. One glance at the back of that label may make you shy away from having stove paint anywhere near your food. It off-gasses like mad for a few days, so leave the painted absorber plate out in the sun as long as possible before assembling. As an alternative, you could opt for a nontoxic metal paint. DecoArt nontoxic, no-prep metal paint works like a charm, and is available online and at some craft stores.
9. Finish the assembly—this unit uses natural convection, with screened openings on the bottom and top to facilitate airflow. The top has a vent door to regulate airflow and temperature. The vents are covered with regular screen material to keep insects out. Install the access door and vents.
10. Now for the window. The book uses just the glass part, but if your dimensions include the frame, don’t remove it. Attach the window to the dryer and bracket it into place. Use a vice to bend the brackets as needed.
Add a thermometer for tracking temperatures (requires a small hole in the side of the unit), and your food-safe screens and start dehydrating!
Total cost for this adventure in making the unit featured here was $118.84, including new screening, sheet metal, hardware, electrical wiring and fixtures, and one small hole in the hand (wayward drill). Salvaged materials included the window, screen, wood, some hardware, staples, reflective tape, and elbow grease. Relatively speaking, you can spend $300 or more on a fancy high-powered electric dryer, but you still have to plug it in. Given that it is nearly impossible to find solar food dryers for sale, it makes this machine priceless.