Vermont Maple Syrup Preserve the Flavor with Proper Maple Syrup Storage

The flavor of maple syrup should remain as delightful as the day it flowed from the tree, through the evaporator, and to the bottle. Unfortunately, at some point you may find crystals growing in the bottom of the bottle or mold growing on the top. Don’t fret – your syrup can be saved!

  • Storing Maple Syrup
  • Maple Syrup Crystals
  • Moldy Maple Syrup
  • Re-heating Maple Syrup
  • Adjusting the Sugar Content of Maple Syrup 

    How to Store Maple Syrup

    Maple syrup is resistant to spoiling because of the high sugar content. In truth, I leave my syrup in a bottle out on the kitchen counter. Sitting out at room temperature for weeks has never been a problem in our house. Plus it makes it so much easier to grab and pour onto my yogurt!

    To store maple syrup properly, refrigerate or freeze it after opening. To maintain the color and flavor of your maple syrup, always store it in glass containers, never plastic. Storing maple syrup in plastic (even unopened), the syrup will darken over time due to oxygen permeating through the plastic. Read more about glass vs. plastic in this blog. If you have maple syrup in plastic jugs, keep them in a cool, dry location to help preserve the color and flavor. Although it does take some effort, you may want to consider repackaging your maple syrup into glass bottles. Read below to find out how.

    Maple syrup will last indefinitely if stored properly. The Canadian Strategic Reserve even has some inventory that is ten years old. I’m not a fan of storing maple syrup that long, but something tells me that your syrup will be eaten before that!

    Maple Syrup Crystals

    If your maple syrup container is starting to look like Superman’s Crystal Cave, then the sugar content of the syrup is too high and crystals are slowly forming. The crystals aren’t bad so no worries. They are actually delicious if you can get them out of the container. Hot water can help with that.

    You can resolve the crystallization issue by re-boiling the maple syrup and adding some water to bring the sugar content back to the correct range. That’s probably more effort than it’s worth, but see the section below on adjusting sugar content below if you want to give it a try.

    Moldy Maple Syrup

    Maple syrup may get moldy if left out of the refrigerator for a long time. One cool thing about maple syrup is that the sugar content is so high that mold doesn’t grow inside the syrup; it’s only on the top surface. So don’t throw it out – the maple syrup can be saved!

    For generations, Vermonters have skimmed or strained off the mold and then merrily poured the maple syrup onto their pancakes. Is that OK? Probably. But like the five-second rule, I’m sure it’s not the “proper” recommendation. If you’re concerned about mold, you can reheat the syrup to kill any mold or bacteria that might be lingering in your syrup. See below for how to heat it, and how to adjust the sugar content as required.

    Re-Heating Maple Syrup

    In the sugarhouse, the finished maple syrup is heated to between 180 and 200°F. Then the bottles are filled to the top, an air-tight cap is secured, and the bottles are laid on their sides to kill any bacteria hanging out on the lids.

    Re-heating your syrup to 180°F will kill any mold or bacteria in your syrup and make it safe to eat. The sugar content will increase a little bit as some of the water evaporates from the maple syrup, but this probably won’t be an issue for most folks. The syrup may be a little extra sweet and may have a slightly thicker mouth-feel. The concern would be if it becomes so sweet that crystals start to form. If you’re at all concerned, read the section below on how to check and adjust the sugar content of your syrup.

    CAUTION: when you heat maple syrup, don’t take your eyes off it. The pot will go from hot to boiling over as soon as you look away. Maple syrup bubbles will rise and flow over the edge of the pot and make a serious mess of your stove. Make sure to have butter or cooking oil at the ready. The oil breaks the surface tension, and will quickly knock down the bubbles. It doesn’t take much – you could barely touch a fork to the butter and likely have more than enough. Seriously, like 1/100th of a teaspoon type amount. It’s pretty amazing!

    How to Adjust the Sugar Content of Maple Syrup

    When bottled in a Vermont sugarhouse, maple syrup should be cooked until the sugar content is 66.9%. In Canada and some US states, the minimum sugar content is a little bit lower at 66.0%. That 0.9% sugar may not sound like a lot, but it’s one of the reasons why Vermont maple syrup tastes just a little bit better than most others!

    Your target sugar content is 66.9%: too high and you may get crystals; too low and the risk of mold increases.

    Unless you happen to have a syrup hydrometer kicking around in the kitchen utensil drawer you’ll need a candy thermometer for this. You don’t want to use a digital probe meat thermometer because it won’t work well in a pot of maple syrup full of boiling bubbles.

    Start by boiling plain water. Let it get to a rolling boil for a few minutes and then check the temperature. Water boils at about 212°F; however, that changes with the barometric pressure. In the sugarhouse, thermometers have an adjustable set point to adjust each day. For your purposes, just note the exact temperature of the boiling water.

    Next, find a sturdy pot with high sides that is small enough to ensure you have about an inch and a half or so of maple syrup in the bottom. Remember the warning about boiling over, and keep that butter handy to knock down the bubbles when they inevitably begin to boil over. And never take your eye off the boiling syrup!

    To hit the 66.9% sugar content, you need your syrup to boil at 7.5°F above the temperature of the boiling water. It’s a sensitive measurement: 7.1°F over the boiling water point would result in maple syrup that is 66.0% sugar content. Somewhere in the 7-8°F should work well. So if your water boiled at 212.5°F, then your syrup will be properly adjusted when it boils at 212.5 + 7.5 = 220°F. As you heat the maple syrup, keep stirring to ensure the heat is evenly spread throughout the pot.

    If your maple syrup is at a full boil, but is less than the target temperature, keep boiling it. You’ll need to raise the sugar content by evaporating off some of the water. When it gets close to being maple syrup you’ll notice a change in the bubbles. The bubbles on the surface will grow larger and larger as the sugar content increases. Before you know it, the multitudes of tiny bubbles will begin to join into large bubbles that may be an inch or two across as they rise to the surface. It can be a little mesmerizing like driving in a snowstorm at night, so stay focused!

    If your maple syrup is at a full boil, but exceeds the target temperature, you need to add a little water to bring down the sugar content. Start with a tablespoon or so. Add the water, stir, wait a couple of minutes, and then check the temperature. Continue to add more water to bring down the boiling temperature until you hit your target. Don’t worry if you go too far because you can simply wait for the water to evaporate and the boiling temperature will go back up.

    Once you’re satisfied that the sugar content is where you want it to be, turn it off and cover it so that no more water evaporates. Now you have a couple of options: put it in a container to be refrigerated or frozen; or, put it in a container designed for canning hot liquids. Glass Mason jars with nice new lids work well. Just fill the jar with syrup that is between 180 and 200°F, put on the lid, and tip it on its side for a minute to kill any bacteria on the lid.

    Now you’re good to store that maple syrup indefinitely. Enjoy!


    (artwork by George Lawrence printed on a T-shirt I bought at the Tunbridge World's Fair about 30 years ago)