Packaging and how you store your microgreens plays a big role in the shelf life of your products. You microgreens need to be healthy and high quality, but it can all be for nothing if you don’t store them properly.
To maximize microgreen storage life after harvest:
Store your microgreens as close to 33°F (1°C) as possible without freezing them, in an airtight container (unperforated) to keep relative humidity as close to 100% as possible. Handle them as little as possible before storing & avoid washing and drying until you’re ready to eat them.
Improper storage can cause a lot of problems:
- Nasty taste from absorbing “fridge flavor”
- Wilting and Unhealthy microgreens
- Shorter shelf life
- Browning and Bruising
- Mold and Microbial Growth
Get ahead of all of these problems and learn how to store your Microgreens by reading this article!
For microgreen buyers
Store them in your fridge in as close to an airtight container as you can. And use the crisper drawer in your fridge.
Close the vent!
The vent is designed to allow you to let more or less air into your crisper drawer. For microgreens you want higher relative humidity (less air exchange).
The temperature setting in your fridge should be as low as possible, without freezing any of your food. Freezing damages cell walls, and causes the texture and flavor to change.
While it does use a little bit more power to keep your food colder, it’s offset by less wasted food: it keeps that much longer.
For microgreens growers
You don’t want a lot of air in your packaging, more air means more oxidation and degradation of your product.
On the other hand if you’re overstuffing your microgreens into the package you can bruise them and this will really speed up decomposition and lower shelf-life.
Excess moisture in with the packaging isn’t ideal, but it can help keep relative humidity up (the number one cause of wilting in non-sealed packaging. You don’t want your microgreens sitting in water.
Grow them properly
If you’re able to grow your microgreens properly they’ll keep a lot longer. Relatively sterile conditions, with good ventilation, and strong healthy plants will all improve storage time.
You need to get a lot of things right, which can be tricky at first. The best thing is to focus on each step and master them one-by-one.
You can get an overview of the critical steps for microgreens here:
And here’s a quick overview of how each of the growing steps impacts storage life:
- Sterilize your seed: seed hulls can harbor mold and other micro-organisms
- Soak seeds to encourage even germination: Uneven germination means some seed hulls are soaking in humid soil. They’re perfect food for mold that’s trying to take hold.
- Drain seeds and rinse: Rinsing seeds during the soaking period can cause any mold spores that have germinated to get flushed away.
- Mix, sift, and measure soil: Using high quality indoor soil, and removing any un-composted debris like twigs and sticks can give mold less food for growth.
- Prepare flats (spread soil, water): Even soil thickness and even watering mean your microgreens grow more evenly.
- Plant seeds evenly at correct density: Density has a huge impact on microbe growth. Too dense and you won’t have any airflow between plants. This leads to a perfect humid environment for mold growth.
- Cover for blackout period (sterilized empty flats), stack or weight: A weighted blackout period traps in moisture and helps orient your microgreen roots in the right direction. This also gives some seeds a little chance to catch up so everything grows evenly. More even germination and vigorous growth gives healthier microgreens which inevitably keep longer.
- Uncover once germinated and expose to light: Blacking out for too long can cause mold problems, and if you don’t wait until even germination, then you have ungerminated seeds which promote microbial growth, transfer microbes to your healthy microgreens, and reduce shelf life.
- Harvesting: There’s a lot more detail on this below, but bruising, rough handling, washing of microgreens, and dirty tools can all reduce storage life.
- Washing: Make sure you scrub or spray down all your equipment and work areas between work period and especially between crops of microgreens. Removing any debris gives microbes less surface area and food to gain a foothold on.
- Sanitize (work area, flats, equipment): This is absolutely critical. While there are always a bit of mold and other microorganisms floating around in the air, you want to start with a clean slate each time.
Proper Microgreens Harvesting Increases Shelf Life
Microgreens are tender young plants and need to be handled really carefully. Careful and minimal handling can improve shelf-life too.
There’s actually more info than I can cover here on harvesting, so I put it into a separate article.
Harvesting is an often overlooked step in growing microgreens, but it has a huge impact on how long your microgreens keep for.
Check out my article here:
Harvest with sanitation in mind
To maximize shelf-life you need to pay attention to how you get your microgreens ready for storage. When you’re harvesting you want to rig the game so your microgreens have the best chance:
- Sanitation: keep your tools, work area, and all your growing equipment clean. I use a mix of water, food grade hydrogen peroxide and white vinegar. Putting in a few extra minutes of sanitation per day has saved me A LOT of trays of microgreens. It pays off quickly.
Handling during harvesting
- Handling: you want to be as gentle, and touch the microgreens as little as possible. They have thin protective walls on their stems and leaves. Any rubbing
Cooling immediately after harvest
If you need to rinse your microgreens to rid them of soil and seed husks, do it in the coldest water you have access to. The cold water will help keep them crisp, and spoil slower.
But ideally, you want to modify your process over time to reduce handling, and reduce the amount of soil that gets on your product so you don’t have to wash at all.
A lot of successful microgreens outfits don’t wash their produce before selling. Not washing is thought to improve shelf life. Washing involves moving the microgreens around, and drying them, and the thin protective layers on the vegetation can be damaged.
In terms of cooling microgreens after harvest, we can take a lot of lessons from other greens like lettuce that have had hundreds of millions of research and development dollars invested.
“Lettuce (Lactuca Sativa) is a perishable commodity that requires immediate precooling and refrigerated storage after harvest to prolong its shelf life.” Source
Lettuce can be stored up to 2 to 3 weeks when held at optimum conditions of 0°C and 98 – 100% RH (Hardenburg et al. 1986).
Key takeaways if we assume microgreens storage should be approximately similar to lettuce:
- Optimal temperature is as close to 0 C (32 F) as you can get without freezing
- High Relative Humidity (98% -100%) is ideal, this means storing in solid containers (no perforations) because your fridge/cooler will be at a lower humidity, drawing water vapour away from your microgreens
Don’t store wet microgreens (drying and airflow)
Wet microgreens are’t going to last as long. Don’t store your microgreens wet! Your watering schedule will place a huge part in how wet your microgreens are at harvest.
Experiment with your watering schedule until you’re satisfied. I find that I get into a regular amount of water per day for my microgreens, then dropping it to half the day before seems to work good.
I’m in a very low humidity (high altitude) location, so you’ll probably have different results.
Optimize your workflow
If you’re growing for yourself, eat fast them right after you harvest them! Keeping microgreens growing for a little longer can change their flavor. But it doesn’t happen that fast, and you might find you actually like your microgreens a few days older.
If you eat microgreens right after you harvest them, you don’t need to worry about storage at all!
Straight into the salad spinner or salad bowl.
If you’re selling them, you can extend the time that customers can store the greens by getting them to market as soon as possible. Cut down the amount of time the greens spend between harvest and getting to the end-user. You can do this by growing the right amount, and harvesting as soon as possible before delivery.
Ethylene Absorbing Produce Bags
A lot of fruits and vegetables in a typical fridge will release ethylene gas which speeds up plant respiration, ripening and decomposition. In microgreens and other greens, higher ethylene levels can cause browning.
To counter-act this problem, materials have been developed that absorb ethylene and put into the form of produce bags.
So there actually appears to be some science behind the marketing in this case!
I haven’t tested these bags myself, but I’m very curious how they would fare against a regular plastic bag for microgreen shelf life.
You can find these BPA-free Produce Bags on Amazon here:
Keep it Fresh Produce Bags – BPA Free (Links to Article)
This paper has some really interesting take-aways:
Post Harvest Physiology of Microgreens – (K.J. Burba et al)
Storage life at 10°C and 4°C temperatures was tested for three species, shelf life dropped from:
- 14 days to 7 days for Red cabbage (a loss of 50% or 7 days of shelf life)
- 20 days to 14 for Radish (a loss of 30% or 7 days of shelf life)
- 14 days to 7 days to Arugula (a loss of 50% or 7 days of shelf life)
Shelf life is often controlled by the microgreen’s respiration rate (measured by new CO divided by unit of fresh microgreen weight)
Dropping temperature is the most effective way to lower respiration and keep quality up
Cotyledons are designed to act as a carbohydrate store for young seedlings, so the plant is continually drawing on them to sustain metabolic activity
These techniques are more interesting than practical for most microgreen growers (including me!)
But it’s interesting to dig into the scientific literature for clues on how we can improve what we’re doing.
There is some cutting edge work being done to extend the freshness of greens as long as possible. And a lot of it involves modifying the gases that the microgreens are stored and packaged in.
Modified air packaging
The idea here is to substitute the air inside the packaging with different gases. Oxygen is very reactive (we need it to be so we can breathe!) Reactive is bad when it comes to storing microgreens for longer.
More info on Modified Air Packaging here.
Large scale controlled atmosphere storage
It might be hard to believe, but produce you buy at a farmer’s market might be as old as a year, and still taste fresh! By controlling the atmosphere during storage, unnatural things are possible.
Interesting read on this subject here.
Visual quality is the most important factor from a business perspective. Even if nutrients are high, a bruised, unhappy looking pack of microgreens is less likely to sell.
Cooling microgreens as soon as possible after harvest is critical for quality. There are a lot of researchers and big budgets invested in keeping food good for longer. The following article investigates sprouts (a younger cousin of microgreens).
Vacuum cooling and storage temperature influence the quality of stored mung bean sprouts, (DeEll, J. et al 2000)
I’m Alex Lafreniere. I learned a lot about plants when I built and operated a landscaping company. I learned even more when I started growing and selling Microgreens. But, learning is a journey, not a goal. Ever since travelling across the world, I’ve wanted to find ways to bring more delicious and exotic plants into my life. This is the site where I share everything I’ve learned with you. And maybe we’ll learn a thing or two together.
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