When canning apples or peaches, the color can be protected by using ascorbic acid, which prevents the food from turning brown, said K-State food scientist Karen Blakeslee.
What color should canned foods be?
K-State food scientist explains why preserved foods change color
Oct. 3, 2023
By Maddy Rohr, K-State Research and Extension news service
MANHATTAN, Kan. – It is the season of canning from apples to cauliflower, pears, peaches and beets. And if you’re concerned about why a canned food has changed color, Kansas State University food scientist Karen Blakeslee said it can be for a variety of reasons.
“In canning, if there is an unexpected color change, that can be a signal that spoilage is present and can affect the quality of the food,” Blakeslee said. “For example, if the stored jars of food are exposed to light, that can cause the food to change color and could cause spoilage.”
Blakeslee added that if food inside the jar is above the liquid at the top of jar, that food can discolor during storage but still be safe to eat.
“Some foods such as pickled cauliflower or garlic can turn pink or blue because the food may be immature or pigments in the food react with the acid in the pickling solution, causing color changes. This doesn’t look right, but is not harmful,” Blakeslee said.
Blakeslee recommends the following to keep canned food safe:
- Keep all produce cool after harvest.
- When using the hot pack method, do not overcook or heat to too high of temperatures. Excessive heat changes natural food pigments.
- Use correct processing methods and time to reduce discoloration.
- Pressure canning can be used to can pears, but it can cause pink discoloration in canned pears. Water bath processing is a better method.
“If the fruit grew in dry weather, it often turns pink and cannot be prevented. While the color doesn’t look right, the pears are safe to eat,” Blakeslee said.
Additionally, garlic can become greenish or purple if it is immature or not completely dry before canning. Red beets may lose color if overcooked or over-processed before canning.
Blakeslee said some color changes can be prevented.
“When canning apples or peaches, the color can be protected by using ascorbic acid, which prevents the food from turning brown,” Blakeslee said. “But some foods, like green beans, will change from bright green to olive green during canning and that is a normal color change that cannot be prevented.”
Blakeslee, who also is coordinator of K-State’s Rapid Response Center for Food Science, publishes a monthly newsletter called You Asked It! that provides numerous tips on food safety. More information is also available from local extension offices in Kansas.
FAQs
Most shelf-stable foods are safe indefinitely. In fact, canned goods will last for years, as long as the can itself is in good condition (no rust, dents, or swelling). Packaged foods (cereal, pasta, cookies) will be safe past the 'best by' date, although they may eventually become stale or develop an off flavor.
Are discolored foods in jars safe for consumption? ›
Blakeslee added that if food inside the jar is above the liquid at the top of jar, that food can discolor during storage but still be safe to eat.
How do you tell if canned food is spoilage? ›
Look at the contents for rising air bubbles and unnatural color. While opening the jar, smell for unnatural odors and look for spurting liquid and cotton-like mold growth (white, blue, black, or green) on the top food surface and underside of lid.
Are discolored canned peaches safe to eat? ›
Can linings might discolor or corrode when metal reacts with high-acid foods such as tomatoes or pineapple. As long as the can is in good shape, the contents should be safe to eat, although the taste, texture and nutritional value of the food can diminish over time. Home canned foods should be used within 1 year.
How do I know if I canned correctly? ›
Testing the Seal
Wait 24 hours or overnight for jars to cool. Press the center of the lid. If it is down and will not move, it is sealed. If the lid looks concave (curved down), it is sealed.
When not to eat canned food? ›
Baker is quick to point out that if the can is dented, especially along the seam, or shows any sign of bulging or rust, it could be a sign of spoiling or botulism. This is potentially dangerous, so it should be discarded to be safe.
How to detect botulism in canned food? ›
When in doubt, throw it out!
- The container is leaking, bulging, or swollen.
- The container looks damaged, cracked, or abnormal.
- The container spurts liquid or foam when opened.
- The food is discolored, moldy, or smells bad.
Usually, this is associated with the proteins in the food, mixed with the heat from pressure canning or water bathing. In return this causes these compounds to be released that create these harmless black or brown spots under the lids. These spots are not harmful; they are just unattractive.
Are old blue mason jars food safe? ›
Vintage, or antique, canning jars are perfect for decorative use. Canning jars have a life expectancy of 10–13 years. After that, you will experience more breakage because of the wear and tear of normal use. Because of this, it is not recommended to use vintage or antique canning jars for food preservation.
What is the most common spoilage in cans? ›
22.3.1.5 Spoilage by Yeasts and Molds
Film yeasts may grow on the surfaces of pickled meat, pickles, olives, and similar products. Molds are the most common food spoilage microorganisms in home-canned foods (such as jams, jellies, marmalades, fruits, and butters) due to their high sugar concentrations (70%).
Gassiness, indicated by tiny bubbles moving upward in the jar (or bubbles visible when you open the can) Food that looks mushy, moldy, or cloudy. Food that gives off an unpleasant or disagreeable odor when you open the jar. Spurting liquid from the can or jar when you open it.
What are three ways you can tell if foods are spoiled? ›
Foods that deteriorate and develop unpleasant odors, tastes, and textures are spoiled. Spoilage bacteria can cause fruits and vegetables to get mushy or slimy, or meat to develop a bad odor. Most people would not choose to eat spoiled food. However, if they did, they probably would not get sick.
What canned food has the longest shelf life? ›
According to the FSIS, canned foods with a low acid content, like meat, beans, peas, soups, or vegetables (or our favorite, canned tuna), will keep anywhere from two to five years. High-acid canned goods like tomato sauce and canned fruit will keep up to 18 months.
Can you eat 100 year old canned peaches? ›
According to the United States Department of Agriculture, canned contents are safe to eat as long as the can is in “good shape.” The Canned Food Alliance agrees, citing 100-year-old canned food that was recovered from sunken ships and tested microbiologically safe.
Why did my canned peaches turn brown? ›
What Causes Peaches To Brown? Peach can be eaten after washing it. But if you are slicing and freezing peaches or canning them, it is nearly impossible to prevent them from turning brown. The browning process kicks because when you cut a peach, a group of enzymes called polyphenol oxidases (PPOs) are activated.
Can canned wet food go bad? ›
In most cases, the reasons for canned food going bad are: Exposure to air, leading to bacteria growth. High humidity or moisture in the air, causing mold. Hot weather, leading to rancidity.
How do you test canned food? ›
If the lid springs up when you release your finger, the lid is unsealed. Tap the lid with the bottom of a teaspoon. If it makes a dull sound, the lid is not sealed. If food is in contact with the underside of the lid, it will also cause a dull sound.
What are the signs that you cannot consume canned food? ›
If the contents have an unusual odour or colour, or if you notice that the inside of a metal container (or lid) is rusted, throw out the contents. Do not use or taste the food. Canned foods are often highly perishable and can spoil quickly once they are opened.
How does canned food not spoil? ›
How is food canned commercially? Jars or cans are heated to a temperature high enough to destroy the microorganisms that could cause food spoilage and/or foodborne illness. The heating process also removes air from the product and creates a vacuum. This vacuum helps prevent recontamination by harmful microorganisms.
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