Tim Long, UC Master Food Preserver Online Program Volunteer    

Dehydration preserves food by removing 80–95% of its moisture, which inhibits the growth of bacteria, yeasts, and molds that require water to grow. It is one of the oldest preservation methods, dating back to 12,000 BCE.  This ancient, simple method uses heat (140° F), dry air, and air movement to create lightweight, nutrient-dense food ideal for long-term storage, backpacking, or preserving seasonal harvests.

Jars of dried apples (photo credit Marina Hsieh)

Core Dehydration Methods

• Electric Dehydrators: Considered the most efficient and reliable method. These machines use an electric element for heat and a fan for air circulation to dry food uniformly at controlled temperatures (typically 95°F–165°F).
• Oven Drying: A convenient option for those without a dedicated dehydrator. It requires setting the oven to its lowest temperature—usually 140°F—and propping the door open to allow moisture to escape. It is less energy-efficient and can take 2–3 times longer than a dehydrator.
• Sun Drying: A traditional outdoor method requiring at least 85°F, low humidity (under 60%), and several days of direct sunlight. It is primarily recommended for fruits due to their high sugar and acid content.
• Air/Room Drying: Best for herbs, hot peppers, and mushrooms. Food is hung in a well-ventilated, low-light indoor area until it is brittle.
• Solar Drying: Uses a "solar dehydrator" (often a tabletop greenhouse structure) to capture and magnify the sun's heat without electricity.
• Freeze-Drying (Lyophilization): A more advanced process in which food is frozen and then placed in a vacuum, causing water to sublimate directly from ice to vapor. This preserves the food's original structure, flavor, and nutrients better than heat-based methods.
• Microwave Drying: Suitable only for small quantities of herbs or leafy greens. It is not recommended for most other foods as it can cause an overcooked taste.

Essential Preparation Steps

• Pretreatment: Many vegetables require blanching (briefly boiling or steaming) to stop enzymatic reactions that cause spoilage. Light-colored fruits are often dipped in antioxidant solutions (like lemon juice or ascorbic acid) to prevent browning.
• Slicing: For even drying, food should be sliced into uniform pieces, typically 1/8 to 1/2 inch thick.
• Conditioning: After drying, fruit should be placed in an airtight container for 7–10 days and shaken daily to redistribute any remaining moisture.
• Pasteurization: Any food dried outdoors should be pasteurized by heating (160°F for 30 minutes) or freezing (0°F for 48 hours) to kill potential insect eggs.

Recommended Drying Temperatures

For long-term storage, keep dehydrated foods in airtight glass jars or vacuum-sealed pouches in a cool, dark, and dry place. Keeping properly sealed dehydrated foods in the freezer will extend their shelf-life almost indefinitely.

Learn more! Attend an online training

For a deeper dive on the above topics, please join the Master Food Preserver Online Delivery Team presentation on Zoom on Tuesday April 14 at 7pm.  https://www.eventbrite.com/e/how-to-dehydrate-food-safely-at-home-without-a-dehydrator-tickets-1983578480632?aff=ebdsoporgprofile 

There will be an additional class on Freese Drying specifically on May 19 at 7pm.

References 

 https://extension.missouri.edu/publications/gh1562

 https://www.ballmasonjars.com/step-step-dehydrating.html

 https://ucanr.edu/site/uc-master-food-preserver-program-orange-county/dehydration

 https://ucanr.edu/sites/default/files/2020-09/335543.pdf

Kirsten Hansen, UC Master Food Preserver Online Delivery Program Volunteer  

The Master Food Preserve Online Delivery Program volunteers loved making preserved lemons this winter! Our Citrus 1: Citrus Without Canning class and Garden to Glass: Winter Mocktails classes featured two different methods for making preserved lemons, and many of us made preserved lemons for our own use. If you missed either class, the recordings for all Online Delivery Programs classes are available on the UC Master Food Preserver website. 

If you made a jar of preserved lemons this winter, you may be wondering how to use them. Traditionally, salt-preserved lemons are used in Moroccan cuisine and other food traditions across the Mediterranean, perhaps most famously as an essential part of tagines—Moroccan stews served with couscous. But preserved lemons are powerhouse ingredients that are useful far beyond traditional tagines. In the Citrus I class, we suggested using them in grain salads and pilafs, soups and stews, and dips. The Garden to Glass: Winter Mocktails class featured a delicious “dirty mocktini” that uses preserved lemon brine. 

Preserved lemon cake slices (photo K. Hansen, used with permission)

One of my favorite ways to use preserved lemons is in a simple Preserved Lemon Tea Cake. As sunny in looks as it is in taste, it was originally published by recipe developer Zaynab Issa in the March 2022 issue of Bon Appétit magazine. Here, the preserved lemon packs lots of citrus flavor in a small package and helps create a not-too-sweet anytime treat. As a bonus, this recipe uses the whole lemon, whereas many other recipes use just the skin and discard the flesh - zero waste! I’ve made a few adjustments to the original recipe, swapping an equal amount yogurt for the original sour cream because I always have yogurt in the refrigerator but only sometimes have sour cream. I decreased the number of dishes I have to wash by chopping the lemon into a paste by hand rather than using a food processor and mixing the batter in a bowl rather than a stand mixer. But really, the original recipe is basically perfect as written.

Preserved Lemon Tea Cake Recipe

Yield: Makes one 8½ x 4½" loaf

Ingredients

Cake Batter

• ½ cup extra-virgin olive oil, plus more for parchment
• 1 preserved lemon (about 55 g)
• 1½ cups (188 g) all-purpose flour
• 2 tsp. baking powder
• ½ tsp. ground turmeric
• 3 large eggs
• 1 cup plus 2 Tbsp. (225 g) granulated sugar
• ½ cup yogurt OR sour cream
• 1 Tbsp. finely grated lemon zest
• 3 Tbsp. fresh lemon juice

Glaze

• ¾ cup (83 g) powdered sugar
• 1 Tbsp. whole milk
• Flaky sea salt

Instructions

1. Place a rack in middle of oven; preheat to 350°F. Line an 8½ x 4½" loaf pan, preferably metal, with parchment paper, leaving generous overhang on the long sides, and brush with oil. Cut preserved lemon into quarters; remove any seeds. Chop and smash the lemon with your knife until it forms a rough paste.
2. Whisk flour, baking powder, and turmeric in a medium bowl to combine. Beat eggs, granulated sugar, and remaining ½ cup oil in the bowl of a stand mixer fitted with the paddle attachment on medium speed until smooth and incorporated, about 1 minute. Add yogurt or sour cream and mix to combine. Add preserved-lemon paste, lemon zest, and lemon juice and mix to combine. Reduce speed to low, add dry ingredients, and mix until just combined, about 15 seconds. (Batter can also be mixed in a large bowl with an electric hand mixer or whisk.) Scrape batter into prepared pan and smooth the top.
3. Bake cake until top is golden brown and a tester inserted into the center comes out clean, 50–60 minutes. Transfer pan to a wire rack and let cake cool for 15 minutes. Run a knife around sides of pan to loosen and, using parchment paper overhang, lift cake out of pan and onto rack. Peel away parchment paper and discard. Let cake cool completely.
4. While cake is cooling, whisk powdered sugar and milk in a medium bowl until smooth.
5. Transfer cake to a platter or large plate. Using a rubber spatula to help guide glaze, spoon glaze over cake, letting it drip down the sides (you should have a fairly thick coating). Sprinkle sea salt over glaze and let cake sit until glaze is set, about 30 minutes.

Do ahead: Cake can be made 3 days ahead. Store in an airtight container at room temperature.

Monica Gross, UC Master Food Preserver Online Program Volunteer  

For most of human history, feeding a family involved navigating times when food was plentiful, such as at harvest time, and periods when it was scarce. Before methods of food preservation were developed, food insecurity was a difficult challenge. Food preservation methods prior to ice boxes and refrigerators included smoking, drying, salting, root cellaring or cold storage, fermenting, and eventually canning. 

Food preservation using home canning was evolving in the late 1800s alongside the development of refrigeration. It was not until 1858, however, in the United States, when John Landis Mason, who was 26 years old, patented a threaded screw-top jar that could be processed to be airtight and watertight. Hence, the Mason jar was born! This article will provide a brief recounting of the milestones that led to the development of the canning jar and lid. 

Canning food began with a challenge by Napoleon

The dawn of the practice of canning began in France in 1795 with a proposal put forth by Napoleon Bonaparte. He challenged inventors to devise a method of preserving food for the French military. A multiskilled chef named Nicolas Appert developed “Appertizing,” which we now call “Canning.” It took Appert 14 years to develop his method and in 1810, he was awarded the handsome sum of 12,000 francs by the French Ministry of the Interior, subject to the requirement that he make the details of his canning process available to the public. (At the time, the typical daily wage of a French worker was just 3 francs!) In that same year, in fulfillment of the reward requirement, Appert wrote and published L'Art de conserver, pendant plusieurs années, toutes les substances animales et végétales (The Art of Preserving, for Several Years, All Animal and Vegetable Substances), the first book on what we would consider “modern” food preservation techniques.

Appert’s method used glass bottles called “fruit jars,” which were 2 to 4 inches in diameter. The jars had to be of uniform thickness throughout to prevent breakage. There were no threads at the neck as we are familiar with today. The top was secured by a cork, which was tapped into place. The cork was secured with a wire and the application of homemade luting or cement. The jar was then boiled. 

Appert’s method persisted for 50 years before Louis Pasteur explained that it was the process of boiling the jars that killed the microbes that caused food spoilage.

A jar invented by a tinsmith

Approximately 50 years after Appert’s success, in America, John Mason filed a patent on November 30, 1858 for a new type of fruit jar closure (see Figure). He devised a brand-new closing method that involved the threads that we are familiar with on our modern Mason jars and lids. Surprisingly, John Mason was not a glassblower; he was a tinsmith by profession.  The new lids that he invented were made of zinc and could be screwed onto glass fruit jars with threads. 

John L. Mason and figures from two of his U.S. Patents (Public Domain)

Mason hired others to make the fruit jars, as they were called. He conscripted a shop owned by Samuel Crowley to make the first jars. A glassblower named Clayton Parker, who worked for Crowley, made the first Mason jar. Crowleytown, New Jersey, is credited as the location where Mason jars were first manufactured. This interesting website shows a picture of the first Mason jar.

Mason's Patent Crowleytown Jar - FOHBC Virtual Museum of Historical Bottles and Glass

As it turned out, Mason’s screw top lids were not without problems. The zinc lid imparted a metallic flavor to the jar’s contents. The jars were also prone to breakage; the shoulders of the jars oftentimes couldn’t withstand the twisting force as the lid was applied or removed, and the jars sometimes broke. These deficiencies were worked on over the years by Mason and others.

After Mason’s patent expired in 1870, many others filed patents in an attempt solve the problems with the jars and lids. Mason himself filed other patents trying to overcome the jar’s inherent flaws. Later, a man named Lewis Boyd invented an opal glass plate to line Mason’s lid. This solved the metallic taste problem for the time being.

Innovation led to solutions

The problem of jar breakage was eventually solved as glass blowing methods improved over the years and the jars could be manufactured with uniform thickness. Much of the innovation came through the Ball brothers. Now that the fruit jar patent was in the public domain, the Ball brothers entered the glassmaking business in 1880. Their first jar was called the “Buffalo Jar” and was marked with the Ball Brothers Glass Manufacturing Company, BBGM Co insignia. The Buffalo Jar, with the company insignia, can be seen at this link: BBGMCo Buffalo Jar - FOHBC Virtual Museum of Historical Bottles and Glass

Other companies began manufacturing jars. Competition was fierce. The Ball Brothers Glass Manufacturing Company eventually came out on top because of the development of the Ball-Bingham machine, a powered glass-blowing machine. Jar production increased dramatically and the market was flooded with the Ball product. In addition, the Ball company partnered with colleges, established fellowships, and focused on agricultural home economic studies. The brothers extended their influence into the home with the publication of their first Blue Book, a pamphlet that included canning instructions and recipes. The pamphlet was published in 1909.

Ball Blue Book Canning Old | PDF | Fruit Preserves | Pickling

In 1915, a grocery wholesaler Alexander H. Kerr was advancing lid development. In 1915 he filed a patent for a jar lid with an integrated sealing compound that would flow when heated, creating a hermetic seal between the lid and the jar. The lid was held in place by a band. This was the precursor of the two-piece sealing method that we use today. 

The modern canning methods that we use today allow us to safely and confidently can foods for our families and friends. We benefit from the collective innovation and work of Nicolas Appert, John Mason, the Ball brothers, namely Edmund, Frank, George Lucius, and William, and finally Alexander Kerr. Our modern societies no longer suffer from food insecurity because of problems with food preservation. In the modern era it may be hard to imagine the struggles that our ancestors overcame to feed themselves as we can easily get food at our local grocery store. We are fortunate to live in the 21^st century!

References

Joann Moser, 2016, Mason Jar Nation: The Jars that Changed America and 50 Clever Ways to Use Them Today. Cool Springs Press, 144pp. 

A Brief History of the Mason Jar, Smithsonian Magazine August 26, 2020.

How Did We Can? | Canning Timeline Table, USDA National Agricultural Library

History of Ball Mason Jars

Earl Weak, UC Master Food Preserver Online Delivery Program Volunteer

County of residence: Alameda

Earl Weak relaxes at his home after an orange harvest (used with permission)

My name is Earl Weak. I became UC Master Food Preserver (MFP) in 2024 as a member of the first class of the Online Delivery Program. My boyhood home was in Abilene, Kansas. I went to the same high school that Dwight Eisenhower graduated from about 60 years before my graduation in 1963. President Eisenhower returned to Abilene a few times while I was in grade school. I still remember my kindergarten teacher talking about the beautiful tulip garden at the Eisenhower home. I think the tulip bulbs for the garden were a gift from the Netherlands after World War II.

While in high school, I started working in the chemistry lab at the local flour mill. This started my interest in flour milling and food technology. After completing high school, I continued my education at Kansas State University in the grain-science program. I graduated from Kansas State University with a degree in food science. After my Army service and more schooling, I started working in the baking industry. My first job was with a national bakery in Kansas City, MO. I worked with bread, fried pies, and cakes. I moved to California for my next job with a cookie-baking company. Large baking ovens were used for baking low-moisture, crisp cookies. I also worked with chocolate to coat some of the cookies and gained additional experience working with fig bars and other fruit-filled cookies.

After retiring, my interest in food preservation directed me to the University of California’s MFP Program. However, I live in Alameda County, which doesn’t have a county-based Program. In 2024, UC started an online MFP Program. I applied and was accepted.  The MFP training has given me new insights into food preservation. I quickly gained appreciation for steam canning. The steam canner is much lighter and comes to a boil much faster than a water-bath canner. Steam canning works for high-acid foods such as apples. I also gained appreciation for dehydrating vegetables. Zucchini dehydration has given me new uses for my summer zucchini surplus!

Now for my last few words. This year, I started my 81^st trip around the sun. I am an old guy (geezer) but I can always learn new things. The MFP Program presents that opportunity. My grandmother was born in 1875. I don’t remember her talking about canning, but she did have many stories to tell about living in a sod house in Nebraska. I still remember her story about making cottage cheese and how she determined the heat level (no thermometers) in the oven of her wood-burning stove. She liked to read and in my young days she would read to me, even my books on dinosaurs.

Marina Hsieh and Henry Shaw, UC Master Food Preserver Online Program Volunteer

Known as Mứt Tắc in Vietnam, these delicious, candied tidbits are a traditional Lunar New Year treat. Just as you eat fresh kumquats whole, you candy all parts of the fruit, whether whole, sliced, or quartered. Serve with tea, in fancy drink concoctions, as a garnish to cakes and desserts, or with salads and savory dishes. 

Yield: about 30 candies or 1 pint in syrup

Ingredients:

• 1 pound kumquats
• Water
• 2 cups sugar

Optional spices:

• 1 (1-inch) coin ginger
• 1 cinnamon stick
• 1 star anise pod

• 2 cloves

   

Instructions:

1. Using a bird's beak knife or other sharp paring knife, cut 6 to 8 vertical slits around each kumquat, spacing them evenly. Leave the top and bottom ends of each kumquat intact and be careful not to cut all the way through the fruit (Image 1).
2. Lightly pinch the top and bottom of each kumquat to form a lantern shape. Use a toothpick or knife tip to gently remove the seeds. Don't worry if you can't remove every seed; they will loosen during cooking, and it's more important to handle the kumquats gently so they don't split apart.
3. Fill a saucepan with water and bring to a boil. Add the kumquats and blanch for 1 minute. Remove the kumquats and drain. Repeat this process two more times (three times total), using fresh water each time. Check again for stray seeds and gently remove them.
4. Refill the pot with 2 cups of water, sugar, and spices (if using). Bring to a boil, stirring to dissolve the sugar. Add the kumquats and reduce heat to low. Keep the kumquats evenly covered in syrup by periodically spooning syrup over them or gently submerging them with a wooden spoon; they will initially float. Simmer until the peel is translucent, about 45 minutes.
5. Remove from heat, cover the saucepan with a cloth, and let the kumquats steep for 8 hours or overnight.
6. At this point, one can dry the kumquats to make candy or store them in syrup. 

Image 1. Slicing and deseeding in preparation for making candied kumquat flowers (Used with permission, Henry Shaw). 

Dried:

1. Using a slotted spoon, remove each kumquat from the syrup and gently press down on the top and bottom to flatten it into a flower shape. This is also a good opportunity to press out any remaining seeds.
2. Dry the kumquats on a baking rack, on a parchment-lined baking sheet in an oven at 200°F or below, or in a dehydrator at 135°F. Drying time depends on the method, conditions, and fruit size; in a dehydrator it takes about 8-12 hours.
3. The candies are ready when they are pliable and no longer very sticky to the touch. They may be optionally rolled in sugar like any candied citrus peel or sprinkled with a few flakes of Maldon salt just before serving.
4. Store in an airtight container in the refrigerator. Kumquats are best consumed within a week, but properly dried and stored, they can keep for months. 

In Syrup:

1. Transfer the kumquats to an airtight container, cover with syrup, and refrigerate (Image 2). Kumquats in syrup are best consumed within several weeks.

Note: Strain and store any remaining syrup in a clean, preferably sterilized, jar in the refrigerator. Use it to flavor sparkling water and cocktails, drizzle on cake or ice cream, or mix into dressings and marinades. 

Candied kumquat flowers (Used with permission, Henry Shaw).

Recipe source: Adapted from Emily Han, 2013, UCCE Master Food Preserver Program of Amador/Calaveras Counties

Joy Agcongay, UC Master Food Preserver Online Program Volunteer

Why Salt and Sugar Matter in Preserved Foods

When we talk about salt and sugar in general cooking, we often think of them as tools to enhance flavor. In food preservation, however, salt and sugar often play a different role. They help control microbial growth by reducing the amount of available moisture in foods. This is why they are key ingredients in many shelf-stable products such as jams, jellies, and pickled vegetables.

Historically, salt- and sugar-based preservation methods were developed to support long-term food storage for households and communities, and not designed to address the dietary needs of babies and toddlers, who were typically fed breast milk and foods prepared for near-term use.

Because salt and sugar play a key role in creating shelf-stable conditions, changes to their use directly affect how foods can be safely preserved.

Why Baby and Toddler Foods Are Different

Research-based nutrition recommendations for young children, particularly those under the age of two, emphasize limiting sodium (i.e., salt) and avoiding added sugars and sweeteners, including honey. Current guidance from the UC Nutrition Policy Institute reflects these recommendations for infant and toddler feeding.

When salt and sugars are reduced or omitted, foods no longer have the same conditions that support long-term, shelf-stable preservation. This difference directly affects how baby and toddler foods can be safely stored and preserved at home.

How Texture and Moisture Affect Storage

Many foods made for babies and toddlers are soft in texture—puréed, mashed (Image 1), or finely chopped. These textures share characteristics that affect storage and preservation.

Foods for small children are: 

• often higher in moisture
• more uniform
• dense in texture, and
• prepared without added salt or sugar

These characteristics influence which preservation approaches are appropriate and help explain why guidance for baby and toddler foods differs from that for many other home-preserved foods.

Image 1. Mashed butternut squash and rice baby food (Used with permission, Paige Weisskirch). 

Why Commercial and Homemade Baby Foods Differ

These differences often raise questions when caregivers compare homemade baby foods to products found on grocery store shelves. Commercial baby foods are often shelf stable because they are processed and packaged using specialized equipment and tightly controlled conditions that are not available in-home kitchens. Because of these differences, research-based home food preservation guidelines follow different rules. Most homemade baby and toddler foods—again, typically prepared with limited salt, no added sugars or sweeteners, and soft textures—are not suitable for shelf-stable preservation at home.

For home-prepared baby and toddler foods, the safest approach is careful preparation followed by long-term storage in the freezer, while following current nutritional guidance for salt and sugar. 

With the right preparation and storage choices, homemade baby and toddler foods can be both safe and practical at home.

Cole Imperi, UC Master Food Preserver Online Program Volunteer

County of residence: Los Angeles

Cole Imperi and fellow trainees (Used with permission). 

The first time I canned anything was the second summer after I bought my first house a few blocks from the Ohio River in Northern Kentucky. I had set up a big backyard garden comprised entirely of heirloom tomatoes, and discovered what happens at the end of a prolific growing season—pounds and pounds of tomatoes that need to be brought inside and dealt with before the first frost.

My husband and I learned to can out of necessity, and we started with tomato jam. If I remember correctly, we made 48 half pints that first season. 

The second thing I ever canned was pickled peaches. My neighbor that lived caddywhompus to us had two peach trees. Exasperated, he showed up at my back fence and dropped two big black garbage bags full of peaches into my backyard and said DO SOMETHING WITH THESE. They became pickled peaches. 

But I didn’t come to the Master Food Preserver (MFP) program because of canning, I came because of grief. But not in the way you might think!

In my career, I’m a thanatologist. Thanatology is the study of death, dying, grief, and loss. In all my years doing this work, I’ve noticed that grievers (and those who love them) tend to congregate around places where transformation happens. Gardens and kitchens are places of transformation. Gardeners turn soil and seeds into harvests, and cooks turn ingredients and spices into meals. The products of gardens and kitchens become tangible reminders that people love us, and that we love them. Casseroles dropped off on doorsteps, or a flat of tomatoes left by a neighbor at your back door, or a half pint of fig preserves left on your desk at work… just because. Food is often a container for things that are hard to say with words alone. And grievers? They use grief to turn their losses into healing, into discovering their ‘new normal’, into whatever comes next.

In early December of 2025, my husband and I packed up two big boxes to send to each of our parents who live across the country. Each box contained 7 different things I’d canned since finishing the Master Food Preserver training program in June of 2025. We were really packing up boxes of food that said, “I miss you” and “I miss sharing meals with you.” 

The other draw for me is community. I’ve been a volunteer and an educator the bulk of my adult life. And part of why I value those things so much is absolutely informed by my work as a thanatologist—when loss shows up, you really see who you can count on, who shows up, and who doesn’t. For someone who’s a transplant to Los Angeles, it’s important to me to give back to a community that has embraced and welcomed me and helped me find a sense of ‘home’ here, too. 

There’s also a part of food preservation that hits home for a lot of people, but in a legacy sort of way. When my fellow Master Food Preservers offer classes to the public, one of the most common questions we get are from attendees who say something like: “My Grandma used to can, can I use her recipes?” For a lot of people, canning and food preservation in general touch on memories, on growing up, on the relationship we still have to our loved ones, even if they’ve passed on. (And by the way, the answer to that common question is “probably not”. You can still can tomatoes (or whatever it was that Grandma did), it’s just that we know a lot more about food safety these days, so the recipe might be tweaked, but it will also probably taste better. Safe, tested recipes mean they are tested not only for safety, but also for flavor and texture.) A lot of people are discovering or reconnecting to their roots when they sign up to take one of our food preservation classes. 

The MFP program was exceptionally rigorous, and it completely transformed my relationship to my kitchen. I’m a better cook just in general because of the program, and it made me a better gardener too. It’s rewarding to be able to contribute to my community in this way. I’d highly recommend this program to anyone who has even a tiny interest—we need more people from more backgrounds and experiences to join our crew. While I came to the program by way of thanatology, maybe you’ll find your way here because of your own unique background and experiences.  

Robin Martin, UC Master Food Preserver Online Program Volunteer

County of residence: Sacramento

Robin Martin (Used with permission).