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
“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.
What causes canned foods to change color? ›
Color changes typically result from the following: How the produce is handled between harvesting and canning. Growing conditions for a particular season. Overcooking or heating foods at too high a temperature.
What are 5 signs of spoilage in home canned foods? ›
Check each jar thoroughly
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.
What are the signs of a damaged canned food? ›
Cans that are leaking, bulging, or have holes in them have Critical (Class I) defects and are easy to identify as unsafe. The difference between Major (Class II) and Minor (Class III) defects in cans is more difficult to evaluate.
How do you know if canned food is OK? ›
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.
How do you know if a canning jar is safe? ›
If the product has turned dark or soft, enzymes have been active or there was too much air present that caused oxidation. Note: molds may lower the acidity of the product in the jar and allow C, botulinum spores to germinate. If something smells bad, bacterial or yeast activity would be suspected.
How to tell if canned food has botulism? ›
Any of the following signs indicate that home-canned and store-bought food might be contaminated with toxins or harmful germs.
- 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.
Dents, bulges, or holes in canned food
Dents, bulges, and holes in canned food are a sign that botulism bacteria may be present. Food in improperly sealed jars can also contain Clostridium botulinum. If you notice any of these signs in canned or jarred food, don't eat it!
What is the most common spoilage in cans? ›
Spoilage can be caused by physical injury, enzymatic degradation, or microbial activity. The main types are physical, chemical, and microbial spoilage. Microbial spoilage is the most common and is caused by the growth of microorganisms like bacteria, yeasts and molds.
Can botulism be killed by cooking? ›
How can botulism be prevented? Only cooking or boiling food destroys botulinum toxin. Freezing does not destroy the toxin. If you prepare or eat traditionally prepared Alaska Native foods, the food safety tips below may decrease your risk of botulism.
Foodborne botulism can happen by eating foods that have been contaminated with botulinum toxin. Common sources of foodborne botulism are homemade foods that have been improperly canned, preserved, or fermented. Though uncommon, store-bought foods also can be contaminated with botulinum toxin.
Can you get food poisoning from old canned food? ›
While extremely rare, a toxin or poison produced by the bacteria Clostridium botulinum (C. botulinum) is a very serious danger in canned goods. Botulism is a deadly food poisoning. The botulism bacteria — rod shaped under the microscope — grow best in anaerobic (absence of oxygen) conditions.
How can you tell if a glass jar is food safe? ›
After feeling the weight of the glass in your hand, tap the side of the glass with either your fingernail or the tongs of a fork. If it makes a gentle clink, your glassware is most likely safe. However, if it makes a long ring, it may contain heavy metals.
Are colored mason jars food safe? ›
COLORED JARS
Blue, green and purple jars have been made for home food preservation. However, there are other colored jars, such as yellow, available for craft projects, but are not recommended for food preservation.
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.
