Presentation on theme: "Drying Foods at Home National Center for Home Food Preservation"— Presentation transcript:
Drying Foods at Home National Center for Home Food Preservation
Disclaimers This slide show is a description of principles and considerations in food dehydration at home. It is not intended to be complete directions or instruction for drying specific foods. It was developed to help educators teach classes in home food dehydration. References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.
A long, long time ago, in a far away place… One of the oldest methods of preserving food Evidence of Middle Eastern and oriental cultures drying foods in 12,000 B.C. Sun and wind- natural dryers Fire creates heat to dry in still houses Electricity Cylindrical commercial dehydrator design patented in 1980
Why dry? Simple Minimal equipment, supplies, and ingredients Reduces size and weight of food Long shelf life Requires little space
Why not dry? Time- 1 (parsley) to 48 (peaches) continuous hours in dehydrator…2 to 6 days under the sun Attention – watch, stir, turn, test for dryness Preparation is same as for canning or freezing Not suitable for all foods
How does drying preserve? Microorganisms (yeast, mold, bacteria) need water to grow, so removing moisture prevents spoilage from microorganisms. –Concerns with jerky and foodborne illness Enzyme action is slowed (though not stopped), which means that color, texture, and quality do not degrade as rapidly once food is dried.
Choosing a method of drying You must be able to control: –Air circulation –Moving air encourages evaporation by maintaining low humidity –Temperature –140°F ideal for most foods –Too slow (low temp., poor air circ.)=microorganisms could grow –Too fast (high temp., rapid air circ.)=cooked food or “case hardening” “Case hardening” is when the outside dries but moisture is trapped inside, resulting in mold.
Methods Outside: Sun Solar Vine Inside: Room Oven Dehydrator
Sun drying For: foods high in sugar and acid (fruits) and very few vegetables (whole peppers, beans, peas) Weather: Hot- 85°F or higher Dry- less than 60% humidity Breezy Work: Build racks or screens Turn 2-3 times per day and cover or bring in at night Cover with cheesecloth and control for insects and pests Pasteurization +/- : low cost, high yield/ takes several days
Solar drying For: foods high in sugar and acid (fruits) and a few vegetables (whole peppers, beans, peas) Weather: –Similar to sun drying, except that temp. increases by 20°F-30°F and air flow increases Work: –Make the dryer (aluminum foil/glass, plastic sheet) –Turn food 2-3 times a day –Pasteurization +/- : low cost /lower yield than sun drying, takes several days
Vine drying For: beans (navy, kidney, butter, great northern), lentils, and soybeans Weather: Same as sun drying Work: Minimal- leave bean pods on vine until they rattle Pasteurization +/- : low cost/takes several days, may need additional drying method
Pasteurization Required for all methods of drying outdoors Done after drying to kill insects and their eggs 1. Freezer method: Seal food in freezer bags/containers and place in freezer set at 0°F or below for at least 48 hours. 2. Oven method: Place food in a single layer on a tray or pan and put into an oven preheated to 160°F for 30 minutes.
Room drying For: herbs, nuts, chili peppers, and partially dried fruits Space/equipment: Sunny room- 80°F and low humidity Fan for air movement Trays, string, or paper bags Work: String herbs or peppers in bundles and suspend in air Spread nuts in single layer on paper, tray, or in paper bag +/- : low cost/takes several days
Oven drying For: Most foods Equipment: Oven which registers 140°F- 150°F Fan for air movement Cookie sheets and liners or cooking spray Work: Set oven racks 2 to 3 inches apart Place foods in single layer on cookie sheets Keep oven door open 2 to 6 inches and place fan nearby Rotate foods occasionally and watch for scorching +/- : relatively low cost/high energy use, ties up oven
Dehydrator drying For: most foods, except milk products and eggs Equipment : Dehydrator with trays Electrical supply Work: Buy dehydrator Occasional turning and testing for dryness +/- : high quality, sanitary, fast/high cost, limited capacity
Dehydrators- features to look for ? Double wall Metal or high grade plastic (not wood) Enclosed heating element Counter-top design Enclosed thermostat Dial to regulate temperature Auto shut-off timer Fan or blower Plastic, sturdy, washable mesh trays Look for: UL seal At least 1 year guarantee Convenient service
Dehydrator design- what’s the difference? Horizontal air flow- heat & fan on side Reduces flavor mixing Equal heat dispersal No dripping onto heating element Limit on height of food pieces Vertical air flow- heat & fan in base/lid Flavors might mix Uneven heat dispersal unless trays rotated Liquids might drip onto heating element; choose fan in lid Andress, E.L. and Harrison. J.A. (2011). So Easy to Preserve, 5 th ed. Cooperative Extension, University of Georgia. p. 322.
Don’t try to dry like this… Heat vent drying Microwave drying, except herbs –And only if your oven manufacturer allows it.
What food products can you dry ? Fruits Vegetables Leathers Jerkies Herbs Nuts and seeds
Fruits – Preparation Wash Core if needed Uniform pieces- whole, halved, or sliced Peeled and thinly sliced dries fastest “Check” whole fruits with thick skins (ex: cranberries) Place in boiling water until skin cracks, then quickly place into cold water to prevent cooking.
Fruits – Pretreatment Sulfuring Sulfite dip Ascorbic acid Ascorbic acid mixtures Fruit juice dip Honey dip Syrup blanching Steam blanching To prevent immediate and long-term darkening
Longest lasting: Sulfur 1.Sulfuring Outdoors only Adverse reactions possible 2.Sulfite dip Adverse reactions possible For one quart of water use: ¾ to 1½ tsp. sodium bisulfite 1½ to 3 tsp. sodium sulfite 1 to 2 Tbsp. sodium meta-bisulfite Soak slices 5 minutes, halves 15 minutes Rinse
Flavor (and calories) added: Dips 5. Fruit juice dip Choose juice high in vitamin C (orange, lemon, pineapple, grape, or cranberry) Soak 3 to 5 minutes, drain 6. Honey dip To 1½ cups boiling water, add and mix ½ cups sugar Cool, then add ½ cups honey. Soak 3 to 5 minutes, drain.
Sweet and simple: Blanching 7. Syrup blanching Boil 2 cups water, 1 cup sugar, and 1 cup light corn syrup Add 1 pound fruit Simmer 10 minutes Remove form heat and let stand 30 minutes Rinse lightly and drain 8. Steam blanching Boil water, lower fruit according to blanching times
Fruits – Drying Single layer Follow directions and drying times provided Watch food carefully at the end…dries much faster! Dry until doesn’t stick or have any visible moisture- Tests: fold in half, squeeze No more than 20% of original moisture should remain for storage.
Fruits – Conditioning Cool 30 to 60 minutes –Packaging too soon = too much moisture could be retained –Too late = moisture could be picked-up Condition to equalize: –Seal in container for 7 to10 days, shaking occasionally –If you see condensation, dry some more Store in dry, moisture-proof containers
Vegetables –Preparation Select freshly picked, high quality veggies Wash Trim and peel as needed Make pieces uniform
Vegetables – Pretreating Water blanching Fill large pot 2/3 with water Bring to boil, then submerge veggies in a basket or colander Start timer (refer to blanching time table) when water returns to a boil If it takes more than one minute to come to a boil, then there are too many veggies…reduce amount next time Dip veggies in cold water quickly– until just slightly hot – to stop cooking Pat veggies dry and place in on tray Steam blanching Add water to large pot, only so full that the steamer basket will not touch the water Bring to boil, then place veggies in the basket Cover with lid and steam according to time given in directions Dip veggies in cold water quickly – until just slightly hot – to stop cooking Pat veggies dry and place in on tray To inactivate enzymes
Vegetables –Drying Dry until brittle or crisp –Some vegetables shatter if hit with a hammer! Store in airtight containers with no more than 10% of original moisture Lower moisture content results in no need for conditioning
Leathers…fruits AND veggies Fun way to mix flavors (ex: banana blueberry) Can use fresh, canned or frozen fruits Can also use tomatoes, pumpkin puree, or mixed vegetables (tomato, onion, celery)
Leathers – Preparation Wash fruit Peel if needed, and cut into small pieces Add lemon juice or ascorbic acid to prevent browning of light colored fruit –2 tsp. lemon juice or 1/8 tsp. ascorbic acid per 2 cups fruit Purée until smooth Add sugar, honey, or corn syrup if desired
Leathers – Drying Line cookie sheet with plastic wrap or use dehydrator tray insert Pour 1/8 inch thick, individual or large Dry at 140°F for 4 to 6 hours (individual) or 6 to 8 hours (large), or up to 18 hours in an oven, or 1 to 2 days in the sun Dry until no indentation from touch in center Roll in plastic wrap and store in moisture-proof container for up to one month at room temp.
Jerky – Preparation Use only lean meat (beef, pork, venison, smoked turkey breast) Slice meat to ¼ inch thick Place in pan with marinade and let sit 1 to 2 hours or overnight For wild game: –Treat to kill Trichinella parasite by freezing piece no more than 6 inches thick at 0°F for at least 30 days Treat pork by freezing piece no more than 6 inches thick at 5°F for 20 days Heating is necessary to eliminate E. coli O157:H7 risk –Heat jerky to 160°F using prescribed methods for pre- or post-drying –Eating jerky dried at 140°F (or below) may pose bacterial risk
Jerky – Heating 1. Heat prior to drying Refrigerate strips in marinade Boil strips in marinade for 5 minutes If possible, check temp. of thickest strips with metal stem-type thermometer to make sure they are 160°F Drain Place in dehydrator preheated to 140°F 2. Heat after drying Preheat oven to 275°F Place dried strips on cookie sheet, not overlapping Heat 10 minutes (at least) Check temp. (160°F) of thickest strips with metal stem-type thermometer
Jerky – Drying Do not dry outside Marinate Dry at 140°F Begin checking for dryness after 3 hours Dry when cracks, but does not break when cool Store jerky in sealed container at room temp. for 2 weeks, or refrigerate/freeze for longer shelf life
Herbs – Preparation Harvest herbs before flowers open Rinse in cool water and shake off excess water For room drying – bundle and tie For oven drying – separate leaves from stems and lay on paper towel, up to five layers on top of each other For dehydrator and microwave drying, place herbs in single layer on tray
Herbs – Drying (in Room) Simply expose to warm, dry, well-ventilated air Sun drying is not recommended Done when leaves crumble and stems break Sturdy herbs like rosemary, sage, thyme, and parsley are easy to tie in small bundles and hang Tender herbs like basil, oregano, tarragon, and mint can also be hung in small bunches –Hang inside paper bags with holes in the sides –Close top with a rubber band
Herbs – Drying in Electrical Appliances Use a cool oven with only the oven light or pilot light on –Will dry overnight Set dehydrator to only 95°F to115°F –Drying times vary from one to four hours Check periodically – done when herbs crumble and stems break when bent Microwaves can be used to dry small quantities –Only IF your oven manufacturer allows it.
Nuts and Seeds – Preparation Not the same as roasting Can dry some seeds (like sunflowers) on plant Wash seeds and place in single layer; peanuts can be shelled or unshelled Option 1: Dry outside in sun Option 2: Dry in dehydrator at 100°F to 130°F (depending on which seed or nut) for 1 to 2 hours Option 3: Dry in warm oven for 3 to 4 hours Stir frequently
Helpful hints Don’t mix foods with strong smells or drying times. Use vegetable oil, vegetable spray, or cheesecloth to prevent sticking to trays. Don’t overlap pieces of food on drying trays. Remember, the larger the load, the longer the drying time, the more nutrients lost. Rotate racks and turn foods periodically.
What to do with dried foods? Eat and enjoy as is! Fruits: –Plump or soften: Cover with liquid for 5 to 10 minutes Steam 3 to 5 minutes Soak, then simmer Vegetables: –Soak 1 to 2 hours in 1 to 2 cups liquid per 1 cup veggies –Add straight to soup, without soaking
Control points Cleanliness is key. Follow 2 hour rule with perishables. Marinate meat in refrigerator. Preheat dehydrator to 140°F (or required temp). Avoid case hardening. Cool to room temperature before packaging. Store in cool, dark, dry conditions.
Credits This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No Photography and illustration credits: –Elizabeth L. Andress, Elaine D’Sa, and Kasey Christian. National Center for Home Food Preservation, University of Georgia. –Andress, E.L. and Harrison, J.A. Preserving Food: Drying Fruits and Vegetables. Athens, GA: University of Georgia Cooperative Extension. Specific credits can be provided for re-use of any individual photo taken by the University of Georgia.
Reference materials Andress, E.L., Harrison, J.A. (2011). So Easy to Preserve,5 th ed. Athens, GA: University of Georgia Cooperative Extension. Nummer, B.A. (2002). Historical Origins of Food Preservation. Athens, GA: The University of Georgia, National Center for Home Food Processing and Preservation. Erickson, C.S.( 1980). United States Patent hydrators&pg=PA1#v=onepage&q=history%20of%20dehydrators&f=false. hydrators&pg=PA1#v=onepage&q=history%20of%20dehydrators&f=false National Academy of Engineering. (2013). Greatest Engineering Achievements of the 20th Century.