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Food Dehydration - Step 1a - Sulfuring

Food Dehydration - Step 1a - Sulfuring

Dry your own fruits, vegetables and other foods

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Sulfuring treatments to prevent browning

If you don't use a sulfuring treatment, many fruits, especially apples, pears, and peaches, will gradually darken during drying and storage. Fruits may be dried without sulfuring, but this sulfuring decreases the loss of vitamins A and C and preserves color and flavor. Sulfuring also deters bugs and souring. Is sulfuring safe?  Yes, it's been around for generations, and while a very small number of people are allergic to it (remember the salad bars?) someone is allergic to almost everything on the planet...

Supplies needed:

You will need

  • trays,
  • a box to place over the fruit, and
  • an outdoors workplace (a screened canopy over a picnic table is perfect)
  • refined pure sulfur (sublimed) (sold at drugs stores or online). Use 1 level teaspoon powdered sulfur for each pound of prepared fruit. .A 2-ounce box of sulfur will treat 16 to 18 pounds of prepared fruit.


Sulfur only the amount of fruit you can dry at one time. Basically, you will create tarys with wood slats or cheesecloth over wood slats and stack them, The burning sulfur will rise through the trays, treating the dried fruit.

Step 1 - setup

 Make trays of wood slats or strips or a wood frame covered with a loosely woven cloth that will allow the fumes to circulate. Do not use metal trays or metal screening because sulfur will corrode them.  I make a wood frame and use stiff PLASTIC screen to separate the levels (trays).

Stack the trays one above the other, separating them with blocks of wood, bricks, or stones. The bottom tray should be 6 to 10 inches above the ground to allow space above the burning sulfur. Allow 2 to 3 inches of space between the rest of the trays. Leave a 6-inch space between the top tray and the top of the box used to cover the stacked trays. This box can be a large cardboard carton or a wooden crate covered with building paper. Make a small opening close to the bottom edge of the box, near one corner, to let air in so that the sulfur will burn. Make about a 1/2-inch hole near the top of the back of the box to create a draft.

Step 2 - load the trays

Put the dried fruit on trays. Don't overload the trays, try to leave each piece not touching the others.

Stack trays as directed in step 1.

Step 3 - start the sufur

 Place sulfur in a clean, flat small dish or pan. Use a metal, ceramic or enameled dish or a small aluminum pie tin, or shape a dish from a double thickness of aluminum foil.

 Roll sulfur loosely in a small piece of paper, twist the ends closed, and place it on the dish.

Light the paper. As soon as the sulfur starts to burn, slide the dish under the bottom tray and put the sulfuring box over the stacked trays.

Sulfur first melts at 240° F, becomes a pasty looking brown, and then burns with a clear blue flame. (The sulfur dioxide fumes you smell protect the fruit.

Do not breathe the fumes because they will irritate your nose and eyes and could make you feel sick.) This is why you are doing this outside!

After the sulfur has finished burning, close the openings in the box with masking tape and start counting the sulfuring time.

Step 4 - close up the boxes and start timing

See directions for each fruit. An alternative for some fruits is steam blanching

  • Apples - Sulfur 60 minutes, or steam-blanch 5 minutes and sulfur 30 minutes. (Apples may be dried without any pretreatment, but they will be darker and have a different flavor).
  • Peaches - Sulfur 1 hour or blanch in steam 7 or 8 minutes.
  • Pears - Sulfur 1 hour or blanch in steam 5 minutes and sulfur 30 minutes
  • Plums - Sulfur 1 hour.
  • Berries, cherries and grapes: sulfuring is not recommended for these

Step 5 - Finishing

When the time is up, lift the box off, tilting it away from you so that fumes don't come up in your face. Remove trays carefully.