AY Honors/Food - Drying/Answer Key

Food - Drying

1. List at least three different ways to dry foods.

Sun Drying

Food can be dried in the sun, but only if the temperatures are near 100°F (38°C) and the humidity is low. The fruit must be covered with cheeseclothe (or something similar) to protect it from insects. If it is dried on a table, the table legs should be set in cans of water to prevent insects from crawling up the legs and getting into the fruit. The fruit will take several days to dry, and the humidity and other weather conditions must be monitored. If the temperature drops significantly during the night, dew may form, and the fruit will absorb it quickly. Because of this, it may be neccessary to take the fruit indoors at night.

Oven Drying

This is the fastest way to dry food, but only small quantities at a time can be dried this way. The oven is preheated to about 140°F (60°C) and the food is placed on racks in the oven. The door must be held open about two inches (5cm) for a gas oven, or about 4 inches (10cm) for an electric oven. A thermometer is placed in the center of the rack to make sure the temperature stays near 140°F (60°C). A fan should be placed near the open oven door so that air inside the oven can circulate and allow the moisture to escape.

The food trays must be rotated every 30 minutes because the heat inside the oven will not be distributed evenly. Rotate the trays from front to back, top to bottom, and left to right.

Food Dryer

Food dryers can be purchased or home-built. They can dry more food than an oven but it takes a little longer. They also use less electricity than an electric oven. A food dryer is an enclosed box with a heat source, a fan, and a set of racks upon which the food is placed. Most home-built food dryers use a 100 watt light bulb as the heat source. It takes four to six hours to dry a batch of food in a food dryer, and like ovens, they operate at about 140°F (60°C).

2. Why and how do you sulphur fruits?

Commercially prepared dried fruit may contain sulfur dioxide which can trigger asthma in sensitive individuals, though dried fruit without sulfur dioxide is also available, particularly in health stores. The sulphur is added to "fix" the colour of the product. "Organic" dried fruit is produced without sulphur which results in dark fruit and the flavour is much more charecteristic of the fresh fruit. The color of some fruits can also be "fixed" to some extent, with minimal impact on flavour, by treating the freshly cut fruit with a preparation rich in Vitamin C (e.g., a mixture of water and lemon juice) for a few minutes prior to drying.

Sulphuring fruit is accomplished by burning a block of sulphur in an enclosed box (such as a dehydrator) with the fruit inside. The burning sulphur gives off sulphur dioxide which fixes the color of the fruit. This should only be done outside.

3. How is dried fruit stored and protected from insects?

As soon as it cools, dried fruit should be packed into insect-proof containers, such as glass jars or metal cans with tight-fitting lids. Do not let sulphured fruit touch metal, as this will cause the fruit to become discolored. You can pack fruit into plastic bags and then place that in a metal container. Plastic bags are not 100% insect (or rodent) proof, so make sure you store the fruit in a place where they cannot get to it. A cool, dry place is best.

4. How are dried foods reconstituted?

Just add water. You can also simmer them in boiling water for 15 minutes.

5. What is important in selecting fruit to be used in making fruit leather?

The fruit must be ripe, or slightly overripe. Be sure to use good quality fruit, as it will make good quality fruit leather. Select fruit that is fresh, and fully sound - basically, the same things you look for when selecting fruit for the table. Cut out any bad parts of the fruit. The saying, "one bad apple spoils the whole lot" applies to fruit leather, as a bad piece of fruit can impart a bad flavor to any of the fruit it comes into contact with. In making fruit leather, the fruit is pureed before drying, so the bad fruit will come into contact with all the fruit.

6. How are dried nuts stored?

Dried nuts must be stored in a cool, dry place in air-tight containers to prevent reabsorbtion of moisture.

7. Dry the following and provide samples for testing:

a. Bread. Make crumbs and use in a recipe for sampling.

Bread can be dried without the use of special equipment by placing several slices in a large bowl and covering it with a towel. The bowl should be kept indoors. After several days, the bread will be dry (also known as "stale") and it can then be crumbled. The usual use for bread crumbs is to make stuffing. You may use any stuffing recipe you like (as long as it uses bread crumbs), or you can use this one:

Ingredients

• 1 small onion
• 1 stalk of celery
• 1 clove garlic
• 2 Tablespoons butter or margarine
• 1/2 teaspoon sage
• 1/2 teaspoon thyme
• 1 cup vegetable broth
• 4 cups bread crumbs

Procedure

Finely chop the onion, celery, and garlic, then sauté them in the margarine in a 2 quart pot until transparent. Add the sage and thyme and vegetable broth and simmer for 5 minutes. Remove from heat and add the bread crumbs, folding them into the mixture. Let it sit for 10 minutes, fluff, and serve.

b. Fruit leather

Wash the fruit and puree it in a food processor. Line a shallow pan with wax paper, being sure to bring the edges up so that the pureed fruit cannot run under it. Pour the fruit puree into the pan until it is about a quarter inch deep (0.6 cm). Place it in the food dryer set to 140°F (60°C). Check it after four hours (but it may take much longer). Remove the fruit when it is tacky to the touch. Remove it and the wax paper from the pan and slice into thin strips, leaving the wax paper attached. Roll the strips (and wax paper) into a spiral and place in a sealable plastic bag. Store in a cool dry place. Fruit leather can be stored for up to six months.

c. Vegetable leather

Pumpkin Leather

• 2 cups of canned pumpkin, or 2 cups of fresh pumpkin, cooked and pureed.
• 1/2 cup honey
• 1/2 teaspoon cinnemon
• 1/4 teaspoon nutmeg (powdered)
• 1/4 teaspoon cloves (powedered)

Combine ingredients and dry at 140°F (60°C) (same as for fruit leather).

Tomato Leather

Core and slice ripe tomatoes into quarters. Boil for 15 minutes. Remove from water, force through a colandar or a seive. Add salt (if desired for flavoring), and simmer until thick. Spread on a plastic or wax paper lined tray and dry at 140°F (60°C) (same as for fruit leather).

References

• http://extension.usu.edu/files/foodpubs/fn330.pdf Utah State Extension
• http://www.extension.uiuc.edu/~vista/html_pubs/DRYING/dryfood.html University of Illinois at Urbana-Champaign.
• http://www.thefarm.org/charities/i4at/surv/dryguide.htm
• http://homeorchard.ucdavis.edu/8005.pdf Storing nuts