Canning 101: Why Do Colors Change in Home Canned Foods?

February 26, 2015(updated on October 3, 2018)

Packing jars

It happens to all of us at some point in our canning careers. You go to retrieve a jar of precious, brightly colored jam, only to discover that the once vibrant color has gone muddy and dull. Once you get over the disappointment, you start to wonder two things. What happened to cause the loss in color and is that jar of jam (or pickles, jelly, fruit butter, relish, fruit halves or tomatoes) still safe to eat?

There are a number of reasons why a preserve has lost its color. Let’s dig in.

Weather Conditions During Growing – The opportunity for discoloration starts while the fruit is still on the tree. Fruit that’s grown during really hot, dry summers has a tendency to turn pink once in the jars. If you experience this kind of discoloration, worry not. While it can’t be avoided, it won’t impact the flavor, texture or safety.

Picking and Storage – Produce starts to break down as soon as it comes off the tree, plant or bush. Heat and extended storage can lead to faded color. However, as long as the fruits and vegetables were still in edible shape when it went into the jar, the product is still safe to eat.

Oxidation – This one is the bane of all canners. As soon as you start cutting up fruit and exposing the flesh to air, it starts to brown. During prep, you can stave off oxidation by submerging the fruit in acidified water (a couple tablespoons of bottled lemon juice in a bowl will do the job). But even when you think you’ve done everything right, you sometimes have some browning on the surface of the finished jam (peach, nectarine, and apricot are particularly prone to this) or, in the case of whole fruit, anything peeking up out of the syrup may discolor. Still safe, though some people prefer to scrape the browned layer away.

Light Exposure – Anytime something with color is exposed to ultraviolet light, it will fade. The reason is that those UV rays weaken the chemical bonds of the color particles over time, causing them to break down. We experience this as color loss. Light-faded products are still safe to eat, but they may not be as delicious as they originally were.

Reduced Sugar – Sugar helps maintain color because it absorbs water and acts as a buffer. The more you reduce sugar in a preserve, the more prone to color loss that product will be.

Exposure to Reactive Metals – Reactive metals like copper, aluminum, and cast iron can leach small amounts of metal into your preserve during cooking, which can lead to darkening and a bonus metallic flavor (yum!). It’s best to keep highly acidic foods out of cookware made with these metals (the exception is high sugar preserves cooked in copper. The sugar prevents the metallic leaching). These preserves aren’t unsafe, but they don’t always taste good.

Use of Salt with Additives – This applies primarily to pickles, but it’s a good one to know. The reason recipes typically call for pickling salt is not just because it dissolves quickly. It’s also free of iodine and anti-caking agents, both of which can cause pickles to yellow or darken.

The basic takeaway here is that most forms of mild fading or browning don’t impact the safety of your finished product. As long as the seal is good, the preserve don’t have any mold growing on the sugar, and it doesn’t bubble when you open the jar, it’s really okay (just to be clear, we’re talking about high acid preserves here). For best quality, keep your canned goods out of direct light and in a place between 50 and 70 degrees F.

Information for this post came from the following sources: Bernardin FAQ, NCHFP Pickle Problems page, Fresh Preserving, the Library of Congress and my brain.

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12 responses to “Canning 101: Why Do Colors Change in Home Canned Foods?”

  1. A wise man I meet a couple of years ago in a raspberry patch that he owns, told me even if something is not the best color after canning, close your eyes they will taste the same. After chatting for a while about different canning ideas, I realized this man was blind. Good advise.
    I made a batch of peach jam a couple weeks ago with some frozen fruit from this past summer and the color is not so bright, but the taste is wonderful, I labeled the jam gg peach jam, for that wise man, Gary Gleason.

  2. Thanks, Marisa, for this series! It’s so helpful in understanding how canning “works,” above and beyond following recipes.

  3. Thank you for yet another great article. I know this question isn’t relative to the color of canned goods, but your picture of the asparagus prompted me to look up canning asparagus on your site…it’s about that time. I noticed you only use pints…either jelly or tall specialized jars. Is there any particular reason you don’t use quart jars for asparagus…besides worry about the opened jar being consumed before spoiling? My mom always used quart jars, but then, we always ate them up quickly. Just want to be sure there isn’t another important flavor or safety reason for the smaller jars. I’ve decided I need to make my own this year. Thanks!

  4. I am making hot sauce that uses fresh chillies that are pureed and heated to 75 or higher celsius for 15 minutes together with over 60% white spirit vinegar plus small volumes of sea salt, fresh squeezed lemon juice, xanthan gum and sugar. We then bottle the sauce at 75 celsius or higher into glass sauce bottles that have been boiled for 20 minutes. We fill to the top and seal with PET screw caps and then invert the bottles and boild for 10 minutes and then cool inverted bottles in a water bath.

    Chillies used are jalapeno red or Cayenne red, Jalapeno green, cayenne green or Serrano green, habanero yello or orange depending on the sauce type.

    Can you advise on this method re how to ensure a 1 year shelf stable product at ambient temps.

    Re the green sauce can you advise how to keep the green colour as close to the natural fruit colour as possible.

    • It sounds like you’re working on a commercial product and that’s unfortunately outside my area of expertise.

  5. Beets lose some color.. add a cup of deep red wine to Borscht or beet puree pot,
    or a tsp to quarts and beets retain a red color

  6. Recently opened a canning jar of homemade beet jelly which has been around for at least 1-2 years. The seal was really good as it took some work to get the lid off. My question or concern is the colour of the jelly is black. Is that OK or do I need to throw it out.

    • Many preserves fade or darken over time, so that’s not a great indicator of whether it’s okay or not. As long as the product was made using a safe recipe, it’s probably still safe to eat. Just remember that preserved food declines over time, so it might taste as good now as it did when it first went into the jars.

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