Have you opened some frozen food to find it has a dry, grayish surface or lots of ice crystals clinging to the surface? This is freezer burn. Freezer burn is simply the result of air coming into contact with food, and while it may not look appetizing, it is usually safe to eat.
Frozen food
The phenomenon of freezer burn happens when tiny ice crystals on the food’s surface evaporate directly into vapor without first going through the liquid water phase – a process scientifically termed sublimation. This moisture loss or dehydration leaves the food’s surface layers dried out and discolored.
Freezer burn happens when food is not adequately wrapped to remove oxygen, which has a bleaching effect on the food surface. Food stored constantly at 0 °F will always be safe. Only the quality suffers with lengthy or inadequate freezer storage.
The bleaching and moisture loss effect of freezer burn may not make food unsafe to eat, but it certainly affects the taste, texture, and color. Severely freezer-burned food will have an off taste and smell that is especially noticeable. It’s best to toss any food that exhibits severe freezer burn as the quality does not merit the effort to save or prepare it. Products exhibiting mild freezer burn are usually fine to eat by cutting away the burned area either before or after cooking. Foods with a higher water content are more likely to get freezer burn.
A few simple precautions will help to avoid freezer burn and ensure frozen foods remain at peak condition at time of use and eliminate food waste. Here are some tips from the experts:
Use freezer-safe containers. Only use bags, jars, paper and containers that are labeled for freezer use. These products are designed to keep air out.
Remove as much air as possible. Air is the enemy of frozen food. Vacuum sealers do a wonderful job of removing air. However, squeezing the contents without smashing will also remove a lot of air. Some people like to insert a straw into the corner of a zipper bag and pull air out before the final close. If using freezer containers, crumple a piece of waterproof paper on top of the food to help minimize headspace. This helps prevent freezer burn, ice crystal formation, and keeps food pieces from drying out.
Maintain the freezer temperature at zero degrees F or lower to help freeze food fast and stay frozen solid. Foods stored near or in freezer doors or at the top of a chest freezer should be eaten first as these areas are for short-term storage. Also avoid packing the freezer tightly; air must be able to flow freely around the food.
Let foods cool before packaging. The USDA recommends cooling food as rapidly as possible, either in the refrigerator or in an ice bath. Cold foods are less likely to trap steam inside the packaging. Steam, like air, is detrimental to frozen foods as it turns to ice crystals. Individual blanched vegetables, fruits, meat pieces, and baked goods are best if cooled and then flash frozen on baking trays (tray pack method) for an hour or two before packaging.
Store-packaging may be left on meat products but they should be over-wrapped in freezer paper, heavy duty foil or plastic wrap, or placed in freezer bags prior to freezing for long-term storage.
Label and date. Freezing keeps food safe almost indefinitely. However, there are recommended storage times for best quality. Refer to the FDA Refrigerator and Freezer Storage Chart which lists optimum freezing times for best quality.
Freezer burn affects food’s quality but not its safety. Even though the food is safe to eat, it doesn’t mean one should. Freezer burn fundamentally changes a food’s chemical composition, affecting its flavor and texture. All foods are susceptible to freezer burn but with proper packaging and freezer management, the problem can largely be eliminated.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
Sometimes a small amount of a frozen food is needed, like a few strawberries for a smoothie, one chicken breast, or a few pepper slices for a soup. By “flash freezing” or using the “tray pack” method, one can easily remove just the right amount of fruit, vegetable, meat, and even baked items needed, rather than thawing larger amounts of food all at once. Removing only what is needed is a great way to reduce food waste.
In the food industry, flash freezing quickly chills food items at extremely low temperatures with circulating air. This quick-chill method keeps ice crystals small, preserving the cell structure and preventing moisture loss in the food when it thaws. In the home, flash freezing refers to the tray pack method or practice of freezing individual pieces of food separately spread out on a baking sheet or tray until firm (1-2 hours). When frozen firm, the frozen food is promptly packaged (use containers or bags specific for freezing to prevent freezer burn) leaving no head space, sealed, labeled, and returned to the freezer. This prevents individual pieces of food from fusing together during freezing.
Small ice crystals are desirable in frozen food to preserve texture. Large ice crystals rupture food cells and cause a soft, mushy texture. Small crystals are formed when food is frozen quickly and kept at a constant storage temperature of 0ºF (-18ºC) or lower, making the at-home tray pack method desirable for any foods that come in or can be cut or broken into individual pieces. Raw, cooked, or blanched foods may be frozen using the tray pack method.
Foods that can be Flash Frozen with the Tray Pack Method
Bacteria, molds, and yeast are present on all fresh foods and multiply rapidly between temperatures of 40°F and 140°F (4°C and 60°C). Therefore, fresh fruits and vegetables should be washed with cool water to remove dirt and residues and prepared appropriately, including blanching when necessary, prior to freezing. Other foods should be handled appropriately for their type. Freezing does not kill most microorganisms in food but prevents their growth. When thawed, the surviving organisms on any frozen food can grow again.
Fresh fruits: strawberries, blueberries, blackberries, raspberries, cherries, mango chunks, cranberries, grapes, bananas slices, pineapple chunks, peach slices, kiwi slices, gooseberries, currants, rhubarb. Fruits that darken, such as peaches, can be pre-treated with ascorbic acid and drained prior to freezing.
Fresh vegetables that do not need blanching prior to freezing: peppers and chilies (seeded, whole, halved, or chopped), onions and garlic (chopped), tomatoes (peeled). [See Freezing Onions, Peppers, and Tomatoes.]
Fresh vegetables that have been blanched, cooled, and drained prior: green/yellow beans, shelled peas, zucchini/summer squash, whole-kernel corn, carrots, okra, sugar/snap peas and small mixed vegetables. [See How to Blanch and Freeze Vegetables.]
Individual portions of meat or chunks of meat.
Individual scoops of cookie dough.
Unbaked, shaped yeast dough.
Individual portions of baked items.
Trays or baking sheets may be lined with a silicone baking mat (Silpat) or parchment paper if sticking or freezing to the metal is of concern. To ensure that there is sufficient cold air to circulate around the trays to freeze quickly and not raise the temperature of already frozen food, add no more than 2 pounds of food per square foot of freezer space.
Food stored at temperatures of 0°F or below will always be safe to eat. Freezing prevents the growth of the microorganisms that cause food-borne illness. However, frozen foods might lose flavor, texture, or overall quality over time. The FDA Refrigerator and Freezer Storage Chart lists optimum freezing times for the best quality of most foods. Other recommendations from StillTasty.com for items not on the list include:
Baked items – 3-6 months
Unbaked yeast dough – 1 month
Cheesecake slices – 2 weeks
Fruit – 1 year
Cookie dough – 3-4 months
With the exception of most yeast dough products, it’s best to plan ahead and thaw frozen food in the refrigerator, where it will remain at a safe, constant temperature — at 40°F (4°C) or below. Other options include thawing in cold water or in the microwave. It’s also safe to cook foods from the frozen state; frozen vegetables are commonly prepared this way. Frozen fruit can be served frozen as snacks or used in salads or desserts.
The Mayo Clinic favors flash-freezing of produce, indicating that studies have shown that fruits and vegetables that are appropriately prepared and frozen as quickly as possible retain nutrients better.
For more information on freezing foods, check out The Science of Freezing Foods by the University of Minnesota Extension.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
Some of America’s favorite, most versatile foods are found in the frozen food aisle. There are some 3,700 frozen food options available to consumers catering to every lifestyle, ethnic cuisine, daily food need, or food occasion.
Frozen foods have definitely made our lives easier and offer great value. With a wide assortment of choices from ready-to-cook meals to ingredients and produce that leave nothing to waste, there are so many reasons to prepare meals using frozen foods. Freezing keeps our foods safe and fresh tasting. Here are some frozen food facts from the National Frozen & Refrigerated Foods Association:
Frozen foods are picked at the peak of ripeness and flash frozen, sometimes right in the field, locking in all of the beneficial nutrients and keeping them in their perfect, just-picked state.
Frozen fruits and vegetables are equally as nutritious as their fresh and canned counterparts.
Freezing acts as a natural preservative, so many of your favorite frozen foods contain no preservatives.
Frozen foods are consistently priced year-round. You are paying for 100% edible food – no stalks, seeds or rinds. And many frozen foods are perfectly portioned so there’s no waste.
Frozen foods last much longer than their fresh counterparts. You can use just what you need and put the rest back in the freezer for next time – wasting less food and saving you money.
We can also freeze many things ourselves at home—summer produce, meat, poultry, fish, eggs, milk, cheese, leftovers, make-ahead-meals, casseroles, breads, cakes, pies, and more. Our food dollars are saved when we use frozen foods in our meals. Prior to freezing, best practices must be followed for any food to retain best quality and be safe after thawing. Check out Storing Food in the Freezer for helpful and safe preparation tips and Freezing Convenience Foods for using your freezer to help with meal preparations.
Although frozen food is convenient, foods in the freezer only remain safe and at best quality if the freezer temperature is at or below 0 degrees F. Keeping a thermometer in the freezer is helpful for monitoring the temperature. The thermometer should be checked frequently to be sure the freezer is maintaining the appropriate temperature. Further, always date and label foods placed in the freezer. Older foods should be used before newer ones for best quality and to avoid freezer burn. Food Safety.gov has a Cold Food Storage Chart for maintaining frozen food best quality; frozen foods stored continuously at 0°F (-18°C) or below can be kept indefinitely.
If you would like more information about freezing and food safety, contact AnswerLine, Monday-Friday, 9 am to noon and 1-4 pm: Phone: 1-800-262-3804 or 515-296-5883 (Iowa residents); 1-800-854-1678 (Minnesota residents); 1-800-735-2942 (Relay Iowa) Email: answer@iastate.edu Follow us on: Facebook or Instagram
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
While residents of most midwestern states usually don’t think about their elevation, elevation affects all aspects of food preparation–cooking, baking, canning, jams and jellies, and candy making. As elevation rises, air pressure falls and water boils at lower temperatures making recipe adjustments necessary.
Boiling water at 1014 Ft of elevation – Photo: mrgeiger
Elevation and Everyday Cooking and Baking
When it comes to everyday cooking and baking, there are few noticeable effects of elevation until one reaches 3,000 feet. Higher elevations present several challenges when preparing some foods. At higher elevations, leavened products using yeast, baking powder/soda, egg whites, or steam rise more rapidly, may collapse, and may not be fully cooked. Because water boils at a lower temperature at higher elevations, foods that are prepared by boiling or simmering will cook at a lower temperature, and it will take longer. High elevation areas are also prone to low humidity, which can cause the moisture in foods to evaporate more quickly during cooking. At elevations above 3,000 feet, preparation of food may require changes in time, temperature or recipe. For those that find themselves at higher elevations, Colorado State University and New Mexico State University have excellent tips and guidelines for successful baking and cooking.
Elevation and Canning Safety
Because water boils at 212°F at sea level and decreases about 1°F for each 500-ft increase in elevation, adjustments must be made when canning foods at home to ensure home-canned foods are processed safely. The amount of time that jars are held at a certain temperature during canning is important to producing a safe product. Processing times for most recipes are based on elevations of 0-1,000 feet unless stated otherwise. When elevations are above 1,000 feet, extra time is added for food processed in a water-bath canner. For food processed in a pressure canner, extra pressure is added. Both adjustments are needed to get to their respective safe processing temperatures for high acid and low acid foods.
USDA and National Center For Home Food Preservation (NCHFP) recipes include a table for proper processing based on elevation to insure sufficient time and temperature have been reached for a safe, shelf-stable product. In the NCHFP table for Crushed Tomatoes, note that time is increased in 5 minute increments as elevation increases for boiling water canning and pounds of pressure is increased for pressure canning. (Crushed tomatoes are one example of a food that can be processed by either boiling-water bath or pressure.)
While time is adjusted for water-bath canning, pressure regulation differs by the type of pressure canning equipment used—dial- or weighted-gauge canner.
Elevation and Sugar Concentrations
Elevation is also a factor in candy making and the gelling of jams and jellies when pectin is not used. At higher altitudes, atmospheric pressure is less so water boils at lower temperatures and evaporates more quickly. Syrups become concentrated and reach the gel point at a lower temperature. The concentration of sugar required to form a gel is in the range of 60 to 65 percent which occurs at 217 and 220 degrees F, respectively, at sea level. As elevation increases, the gelling point decreases by 2 degrees per 1,000 feet. When elevation is not taken into consideration, overcooked jam is the result as too much water has boiled away leaving a sugar concentration that is too high, leaving a jam that is gummy, dark in color or tough. The same is true for candy making. For each 1,000 feet above sea level, reduce the temperature in the recipe by 2 degrees F to prevent overcooking. Colorado State University provides a High Elevation Candy Making (Sugar Solution) Adjustment chart for various kinds of candy mixtures.
Find and Know Your Elevation
Elevation matters in all aspects of food preparation. It is especially important for the safety of home canned products beginning at elevations above 1,000 feet. Before beginning the canning process or making sugar concentrations, find your elevation using one of these sources to insure proper processing of canned products and prevent overcooking of jams and candies:
Refer to an elevation map for your state showing approximate elevations such as this one by Iowa State University Extension and Outreach from the Preserve the Taste of Summerseries.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
Stack of food storage containers with food – Photo: Canva.com
Safe storage practices are just as important as knowing how to safely prepare, serve, or preserve food. Most kitchens contain an assortment of containers, wraps, and bags for storing food either short- or long term. These items may be glass, plastic, silicone or metal. How do we know if a container is appropriate and safe for storing our foods?
To begin, all food products should be stored in food-grade containers. Food-grade is a regulatory term used to specify materials and products that are suitable and safe to come into contact with food and beverages at any point in the field-to-consumer chain. To be certified as a food-grade, food-safe material, the material undergoes extensive testing to insure that the material does not affect the color, odor, taste, or safety of the food or leach substances into the food. The Food and Drug Administration (FDA) is the regulatory agency responsible for determining the safety of materials for food use. It is important to note that a food-grade material is only considered food-safe if it is utilized per its intended use.
Safe Food-Grade Container Options
Glass, stainless steel, and ceramic – These materials are non-reactive and non-toxic. They are easily sanitized and offer the most longevity. These materials are sturdy and heat-tolerant and do not release chemicals or toxins into food. Further, they are inert and do not react with natural chemicals or dyes found in food. Food and beverages stored in these containers stay fresh longer. Glass and ceramic can be microwaved; all three can be heated in the oven and placed into the dishwasher. These materials are eco-friendly; glass is especially so being 100% recyclable. Some cons of these materials include weight, breakability (glass and ceramic), cost, bulk, and lack of portability.
Plastic – There are many reasons to use plastics: inexpensive, lightweight, hard to break, stackable, and readily available. While there are many plastic choices, one must choose wisely. Experts caution us against using plastics in general, and in particular older plastics, or re-using one-time-use plastics from purchased foods. Although plastic containers are convenient, many may contain BPA (Bisphenol A), a chemical that blocks and interferes with hormones leading to health issues. BPA is a big concern in older plastics or plastics that are scratched or heated in the microwave.
Any plastic used should be microwave safe, dishwasher safe, and BPA-free. Plastic products are typically labeled with a number surrounded by the recycling symbol. These numbers and labels identify both the type of resin used to make the plastic and the product’s recyclability. Associated with the different types of resin are potential health risks. The Smart Plastics Guide provided by the Public Broadcasting System (PBS) summarizes seven different types of commonly used plastics, product examples, recyclability, and potential health risks.
Safe plastic numbers include 2, 4, and 5. These containers can store food without any toxic chemical infiltration and include the HDPE, LDPE, and PP materials. Containers with the number 7 are made of polycarbonate (the category that includes BPA), so should not be used with food. Plastics bearing numbers 1, 3, and 6 are single-use-only containers or bottles.
So what about those easy-to-pick-up plastic containers available at retailers or our long-held Tupperware®? Check to make sure they are labeled with one of the safe plastic numbers, BPA-free, and dishwasher and microwave safe. According to its website, Tupperware® items sold in the US and Canada have been BPA-free since March 2010; containers prior to 2010 should be disposed of as should any other older containers that do not display numbers 2, 4, or 5, contain BPA, and are not dishwasher and microwave safe.
Since plastic does not have the longevity of glass or stainless steel, food safety experts encourage swapping out plastic containers frequently and especially if there is any discoloration, odor, or a change in taste when using the container. When plastic containers become scratched, stained, or damaged, they begin to pose a food safety risk by harboring bacteria and other harmful microorganisms that can contaminate food.
Silicone – Per the FDA, food grade silicone is safe and will not react with other materials or release hazardous compounds or fumes when heated. Food-grade silicone is safe to store food, put in the microwave, freezer, oven, and dishwasher without hardening, cracking, peeling, or becoming brittle as it is resistant to extreme temperatures. It is made without petroleum-based chemicals, BPA, BPS, PVC, latex, lead, phthalates, or fillers. It will not leak, break down, or degrade over time. Silicone containers are available in many forms, lightweight, easy to transport, and considered a non-hazardous waste.
Cautions with silicone storage containers include limited studies on the long-term health effects of using silicone products as they are fairly new to the market. And while silicone is not a hazardous waste, it can only be recycled at special recycling centers.
All containers should provide a secure, air-tight seal.
As we strive to provide fresh, flavorful, and safe food for our families, it is important to store our food properly. Make choosing an appropriate food-grade storage container a priority to keep your food safe and fresh in the pantry, freezer, or refrigerator.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
AnswerLine is pleased to welcome Jennie Savits as our newest team member. Jennie joined AnswerLine on June 1 and brings a wealth of knowledge and experience to the team. Further, she is no stranger to Iowa State University or Extension and Outreach.
Jennie holds BS/MS degrees in Food Science from Iowa State University and completed 11 years with the Midwest Grape and Wine Industry Institute at Iowa State University. While with the Institute, Jennie held various roles in the lab and in the field. She worked on extension and outreach activities and research projects to support the local grape and wine industry in Iowa and throughout the Midwest. Jennie also has experience with the Department of Food Science and Human Nutrition at Iowa State University as a lecturer, where she taught food science laboratory courses and oversaw laboratory renovations.
Jennie’s interest in food science stemmed from participation in the 4H and FFA organizations. Growing up in rural Boone County, she was a member of the Harrison Happy Hustlers 4-H club and the Boone A&M FFA Chapter. Jennie enjoyed completing 4H projects in the areas of food and nutrition, horticulture, and livestock. Food science became a key area of interest after she competed on a team that won the inaugural Iowa FFA Food Science Career Development Event (CDE). Their team went on to place 2nd nationally and directed Jennie’s career path toward food science.
Jennie says that she really enjoys the opportunity to help people find answers and solve problems, especially on topics related to food safety and food preservation. Jennie has developed strong relationships within the Iowa State University Extension and Outreach organization and looks forward to helping disseminate research based information to those we serve.
Savits family – Photo: jsavits
Jennie lives with her husband, Paul, and their 5 children on a farm near Ogden. She enjoys spending time with family, helping out around the farm, and gardening.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
The last things that anyone wants to find in homemade grape jelly or syrup are granular or crunchy bits or a hard crystal formation at the bottom of a jar of juice or intermingled in jelly. After the effort of foraging wild grapes or picking domestic grapes, juicing the grapes, straining the juice, and making and processing juice, syrup, or jelly/jam, these finds are discouraging. The hard formation or crunch bits are crystals—crystals formed from tartrate acid, sugar, or evaporation.
What Are Tartrate Crystals?
Tartrate crystal formed at the bottom of grape juice. Photo by M Geiger.
Grapes differ from many other fruits in that they contain tartaric acid, a unique, natural compound. When juice is extracted from grapes and cooled, the tartaric acid reacts with potassium, the mineral of highest concentration in most grape juices, to form harmless potassium bitartrate crystals, also known as tartrate crystals or tartrates. While the crystals pose no food safety risk, they are certainly unwanted when preparing grape juice, syrup, jams, jellies, and even wine. Tartrates in wine are known as wine diamonds and may appear as salt crystals, glass shards, or fine dust in a bottle or glass of wine—visual defects that the wine industry works hard to prevent. Tartaric acid is used in the making of cream of tartar.
Preventing Tartrate Crystals
Regardless of the grape variety or color, preventing tartrates is easy to solve with time and filtering materials.
Begin by extracting the juice from the grapes by traditional methods or a steam canner. Let the freshly extracted juice sit undisturbed overnight or for 24 hours in the refrigerator. Oregon State University Extension suggests two to five days. My personal experience is that longer is better if one has the time and space, as crystals have formed in my juices after sitting overnight and even after 24 hours. When the juice is warm, the tartaric acid is suspended; as the juice cools, the tartaric acid binds with the potassium to form solid crystals that sink to the bottom of the container along with any other sediment.
Remove the juice from the refrigerator, being careful not to disturb the juice. Clarify the juice by pouring the juice into a clean container through cheesecloth, a jelly bag, or a fine strainer before beginning any further preparation. As you near the bottom of the container, avoid pouring the sediment and crystals into the container. The sediment and crystals should be discarded. It is also an option to filter the juice a second time, if desired.
Free of tartrates and sediment, the juice is ready to be used for jelly, syrup, or juice. Recipes for jelly, syrup, and juice can be found at the National Center for Home Food Preservation. The juice can also be frozen to be used later for making jelly or enjoying as juice.
What are Sugar Crystals?
Sugar is made up of tiny sucrose crystals which prefer to remain in their dry, undisturbed crystalline state. Even when sugar is dissolved in liquid, as when making jams and jellies, the sugar molecules like to congregate into groups or crystals. All they need to start the process is a “seed,” such as a lone undissolved sugar crystal as a nucleus to draw other sugar molecules towards it. Sugar crystals are not unique to grape sweet spreads. Regardless of the fruit, the sugar must be completely dissolved with no traces of crystals to provide a “seed” when making sweet spreads or syrups.
Preventing Sugar Crystals
Crystals in sweet spreads may be caused by excessive sugar, undissolved sugar sticking to the sides of the kettle, or a mixture cooked too slowly, too long, or too little. To prevent crystals from forming:
Follow the recipe exactly. Do not add or decrease the sugar or double the recipe.
Wipe the side of the pan free of crystals with a damp cloth before filling the jars. This will prevent a seed point from forming.
Cook with a rapid boil. Remove from heat immediately when the jellying point is reached.
Cook until the sugar has completely dissolved and mixed with the fruit juice.
Learn additional tips to prevent crystals from this Penn State Extension video. Sweet spreads exhibiting sugar crystals are safe to eat.
Evaporation Crystals
Crystals that form at the top of a jar of jelly or sweet spread that has been opened and allowed to stand are caused by evaporation of liquid. Over time, these crystals may also work their way down through the spread. This is usually due to long-term refrigeration or a poorly capped jar kept in the refrigerator. Fruit spreads exhibiting evaporation crystals are safe to eat. White, fluffy mold on the surface of a sweet spread is a sign of spoilage and should be discarded.
Sweet spreads that have crystallized due to evaporation can sometimes be saved with a gentle rewarming to melt the crystals, as one might reheat honey that has crystallized. Place the jar in a pan of hot water or carefully microwave until the crystals melt. Stir as needed. If melting is successful, a fresh jar should be used to prevent recrystallization from the crystals that may remain on the walls of the jar. Adding a small amount of lemon juice or corn syrup may also fix it. In all cases, it is usually a temporary fix as the product may crystallize again if not used in a timely manner. A tight-fitting lid is the best prevention.
With just a little patience and careful preparation, crystals of all types can be prevented in grape products.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
The dictionary defines ‘conditioning’ as a means to change a behavior or strengthen muscles. In the realm of food preservation safety, ‘conditioning’ is the process used to equalize moisture left in food after dehydrating to decrease the chance of spoilage or mold growth. While conditioning could be used for all dried foods (herbs, vegetables, and fruits), conditioning is most important for fruit including tomatoes; it is often the “forgotten step in dehydrating.”
Dehydrated foods in jars – Photo: Canva.com
The moisture content of home dried fruit should be about 20 percent1 or less when removed from the dehydrator or oven. However, due to the size of the pieces, location in the dryer, or uneven drying, the remaining moisture may not be evenly distributed among the pieces. Even drying can be hard to obtain in a home dehydrator and naturally some pieces will likely have more than a 20% moisture. Because there is no sure way to test for moisture at home, conditioning becomes necessary and is the last step before final storage. Conditioning is not necessary if the fruit is dried for immediate snacking rather than storage; dried fruit for snacking should be stored in the fridge and eat within 3-4 days.
Conditioning is easily done following these steps:
Cool foods on trays and test for dryness. Dried fruits should be leathery and pliable when cool. Squeeze a handful of the fruit. If no moisture is left on the hand and pieces spring apart when released, they are dry.2
Place the food into non-porous, food grade containers (glass or clear plastic jars work great) filling about two-thirds full. Seal the container with a lid.
Shake or stir the contents daily for 2-4 days. During this time, the drier pieces will absorb the excess moisture of the less dried pieces.
Check for condensation on the lid or sides of the container or food pieces sticking together. Also, look for signs of spoilage. If condensation is noted, return the food to the dryer for additional drying time followed by another conditioning. If there is any sign of mold, discard the product.
If drying the same food in successive batches, freshly dried fruit may be added to a conditioning batch within the first five days with conditioning time lengthened to accommodate the additional food.3 Conditioning is also recommended for fruit leathers.
What about conditioning vegetables and herbs? Vegetables and herbs do not generally require conditioning because they contain very little water when properly dried. Dried vegetables should be hard and brittle. For more information on individual vegetables, check out Drying Vegetables – 9.308 to help determine dryness. Herbs are dry when they are crisp and crumbly. Conditioning of vegetables and herbs is an option to reduce concern.
Once fruit is conditioned, it is ready for packaging in glass jars, food-grade plastic containers or plastic food-storage bags. The packaging used should provide an airtight seal. An oxygen or moisture absorber may be added but is not necessary. Packaging in smaller amounts is recommended as once the package is opened, quality begins to deteriorate; the food may lose flavor or absorb moisture and odors from the air. Storing in a cool, dry, dark location is best. The same packaging recommendations apply to vegetables and herbs.
So while the dictionary doesn’t define the conditioning of dried foods, perhaps a third definition should be added. Conditioning is an essential step in the safety of dried foods, particularly fruits and tomatoes.
Sources:
So Easy to Preserve, 6th edition. Page 341. University of Georgia Cooperative Extension
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
Calcium Chloride is a firming agent that can be used in quick-processed pickles for crispness. It works by firming the natural pectin of the vegetable. It should not be confused with table salt, which is sodium chloride.
Calcium chloride products – Photo: mrgeiger
Currently, calcium chloride is available to consumers as a granular product under the labels of Ball Pickle Crisp® and Mrs. Wages Xtra Crunch®. Regardless of the label, both are pure, certified food-grade calcium chloride. (Non-food-grade calcium chloride should not be used for home canning.) Calcium chloride is a safe, non-toxic food additive that has been tested and approved by the Food and Drug Administration (FDA), World Health Organization (WHO), Canadian Food Inspection Agency, and European Food Safety Authority (EFSA).
Calcium chloride may be used in place of food-grade lime (calcium hydroxide) to firm pickles. However, it does so with less fuss and offers the same great taste and crispness. Firming with lime is traditionally done by soaking fresh cucumbers in a lime-water solution before pickling them; during the soaking, the calcium hydroxide binds with the pectin in the cucumber making it stronger. Excess lime absorbed by the cucumbers must be removed by additional rinsing to make pickles safe; pickling lime raises the pH (more alkaline) and has been linked to botulism. Because calcium chloride does not have the hydroxide component of lime, it does not change the pH (acidity) of pickled food or pose a food safety risk. No soaking and rinsing is involved when calcium chloride is used. Rather, a small amount of the calcium chloride granules is added to each jar of pickles before sealing, following the manufacturer’s directions. (Calcium chloride should not be added to a vat during brining or fermentation of pickles.)
Calcium chloride will not replace the crispness that is lost from fresh produce. That crispness comes from the vegetable’s natural pectin, so starting with fresh-picked, top-quality produce is best.
There are other uses for calcium chloride beyond pickle crispness. It is used by brewers, cheese- and wine-makers and has been found to improve the texture of canned apple slices, pears, and peaches. Consumers report using it when canning whole tomatoes to hold the tomatoes together. Calcium chloride may impart a bit of a salty taste but adds no sodium. Use of calcium chloride should be avoided by anyone having a sensitivity to it.
Calcium Chloride products have an indefinite shelf life but are sensitive to moisture and will clump and become hard when exposed to humidity, so it is important to keep the granules as dry as possible; store the products tightly sealed in a cool, dry location.
Reference to any commercial product, process, or service, or the use of any trade, firm, or corporate name is for general informational purposes only and does not constitute an endorsement, recommendation, or certification of any kind. Persons using such products assume responsibility for their use and should make their own assessment of the information and whether it is suitable for their intended use in accordance with current directions of the manufacturer.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
Canning, pickling, freezing, drying, and fermenting are well-known methods of preserving fruits and vegetables for future use. These processes have been used for generations and made simpler and safer over time with the help of science and innovation. Freeze drying (lyophilization) is a more recent option for home food preservation due to the advent of home freeze dry units. HarvestRight, a company in Salt Lake City, Utah, introduced a freeze drying unit for home use in 2018, opening new opportunities for home food preservation. Early in 2023, a second company, Prep4Life, introduced a slightly different freeze drying unit for home use known as THE CUBE; Prep4Life is also a Utah-based company.
Example of a freeze drying unit exhibit at retail location – Photo: mrgeiger
Freeze drying is not a new process. The process may date back to the 13th century, with the Incas using a simple process to preserve potatoes in the Andes. The first patent was issued in 1934. During World War II, it was used to safely transport blood serum and penicillin to the battlefield. In the 1950s–1960s, freeze drying was viewed as a multi-purpose tool for pharmaceuticals and food processing and became a major component of space and military rations. Freeze drying has been widely used in the food industry for some time to extend the shelf-life of food while maintaining quality (think berries in commercial cereals that feature real berries) and offer consumers fast meal prep, emergency preparedness, and portable food. Freeze-dried foods also offer convenience as some foods can be eaten “as is” (except for raw meat, poultry, seafood, and eggs), added directly to recipes, or rehydrated and used as fresh food.
In a nutshell, freeze drying works by dropping the product temperature to <-40F under pressure, then reducing the pressure and adding heat to allow the frozen water in the product to change directly to a vapor (sublimate). Per HarvestRight, the process removes 98-99 percent of the moisture in food yet retains 97 percent of the nutrients, natural enzymes, and original flavor and color, making it a superior method for preserving food [1]. Additionally, freeze-dried foods are easy to use; food returns to its original pre-freeze dried state by just adding water. Since nearly all water has been removed, freeze-dried food is light, making it a favorite for camping and backpacking. A 10-pound bag of fresh apples weighs about one pound after freeze drying. Further, freeze dried foods supposedly have a 25-year shelf-life under proper storage conditions.
To date, very little university research has been done on in-home freeze drying; specifically research on how long the food retains quality and nutritive characteristics [3] as well as bacterial studies. Utah State Extension staff has been experimenting with the HarvestRight dryers. In a recent webinar, they stressed that freeze drying produces high quality foods that are safe as long as they are handled properly prior to freeze drying, dried thoroughly, packaged appropriately, and used or prepared correctly once the packaging is opened. It is important to note that freeze drying does not kill bacteria or other microorganisms; they remain viable, but dormant, despite the extreme conditions of freeze drying. Any bacteria or microorganism on raw foods prior to freeze drying will reactivate upon rehydration. Therefore, food items that are traditionally cooked before eating must also be cooked before eating as a freeze-dried food.
Nearly any food item can be freeze dried—fruits, vegetables, herbs, meats (cooked and raw), eggs, dairy, meals, casseroles, desserts. Utah State recommends that vegetables be blanched prior to freeze drying to prevent discoloration. Food high in fat content, high in sugar content, and baked goods such as breads, cakes, muffins, etc do not freeze dry well and should be avoided. Sugar causes foods to expand.
To ensure the safety and quality of freeze-dried foods, basic food safety principles must be used in preparation, product must be completely dried (crisp), and product must be stored quickly and properly. As soon as foods are removed from the drier, they must be immediately packaged to prevent them from taking on moisture. Proper packaging is crucial to extend the shelf life of freeze-dried foods and prevent contamination or spoilage. The storage container must eliminate oxygen, light, and moisture. In order of long-term to short-term storage, the following containers may be used: Mylar® bags, vacuum-sealed canning jars, #10 cans, vacuum sealed bags, and PETE re-sealable containers. An oxygen absorber, not a desiccant, must be enclosed in the container to remove or decrease the available oxygen in the package to help maintain product safety, quality, and extend shelf life. Foods should be stored in a cool, dark place.
For long-term storage, PET or PETE (Polyethylene terephthalate) food grade, non-toxic plastic pouches, also known as “mylar bags” are excellent. The opaque (silver) Mylar® bags are preferred; they block out air and light during storage, can be resealed once opened and take up less space than glass jars or cans. Mylar® bags with a clear side are not long-term air tight [3]. Mason canning jars can be used if they are vacuum sealed with a vacuum sealing machine capable of using a jar sealing device. Metal cans have a zero oxygen transfer rate and are great for long-term storage [4]. However, a #10 can contains a large amount of dried food which must be used at the time of opening or resealed in another container. Vacuum bags and re-sealable containers have short-term oxygen barrier qualities.
Oxygen absorbers do not have a long shelf life; as soon as they are exposed to air (oxygen), they start to absorb and are spent when they become hard. They are available in different sizes (measured in cc’s); contents and container size should be considered when purchasing absorbers. The smaller the container the less cc’s needed. There is no harm in using a larger than needed absorber and would be preferred to one that is too small [3]. When a container is opened, the absorber should be replaced before resealing.
A freeze dryer is not a fancy food dehydrator. While a freeze drying unit and a dehydrator both remove moisture from food so that microorganisms cannot grow and enzyme action is slowed down, a dehydrator uses low heat and a fan to remove 80-90 percent of the moisture content from food[5]. While dehydration is a very acceptable means of food preservation, it differs from freeze drying in several ways: – foods shrink up and develop a leathery feel and appearance; – foods do not return to their natural state; – foods retain less of their nutritional value; – foods have a 4 months to 1 year shelf life; – fewer foods are successfully dehydrated; – foods rehydrate slowly.
There are many advantages to freeze drying. Besides holding nutritive value, it allows one to utilize garden produce at the peak of harvest, buy in bulk, save money over commercially prepared freeze-dried foods, offers a long shelf life, preserve foods that cannot be typically preserved, and offers compact, lightweight storage. Some disadvantages pointed out by Utah State Extension include unit size, noise, time for drying and allowing freezer to unthaw, cleaning, sanitation, and maintenance, small batch sizes, and cost—cost of the machine as well as machine accessories, packaging supplies, sealers [10], and electricity. In addition, reconstituting freeze-dried foods is somewhat experimental. Utah State Extension specialists suggest starting with a small amount of water and giving ample time to reabsorb; there is no need to rehydrate herbs, onions, or bell peppers as they can be added directly to foods and will absorb moisture from the food. Buying a Home Freeze-Dryer: What to Know Before You Goand Let’s Preserve: Freeze Dryingoffer more information.
The options for food preservation are many.Each method offers pros and cons to preservation and storage. If long-term food storage or portable food storage is the goal, freeze-drying is an option to consider. HarvestRight machines are available at several retail outlets. The Cube is available from the Prep4Life company.
Schmutz, Andrea and Callie Ward. 2 May 2023. Freeze Drying. Utah State University. Preserve the Harvest Webinar.
Reference to any commercial product, process, or service, or the use of any trade, firm, or corporate name is for general informational purposes only and does not constitute an endorsement, recommendation, or certification of any kind. Persons using such products assume responsibility for their use and should make their own assessment of the information and whether it is suitable for their intended use in accordance with current directions of the manufacturer.
I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.
