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Nuts and seeds are the perfect nutritious addition to smoothies, salads, oatmeal, baked goods, and so much more. So when a recipe calls for them or snack time rolls around, many of us head to the pantry where several nut and seed varieties linger in the back of our cupboards, often for months on end. But what you might not realize is that the pantry is not actually the best place to store your nuts and seeds. Rather, the refrigerator—or better yet the freezer—are more ideal when you’re trying to stretch your dollar (and nut supply). Read on to learn why nuts are so prone to spoilage, how to best store them, and their average shelf-life in different storage settings.
Why Nuts Are Prone to Spoilage
Nuts and seeds are staple food items in households nationwide, and are super tasty and highly nutritious options. “They usually offer high amounts of protein, unsaturated fats, fiber, plant compounds, minerals, and vitamins,” says Abbey Thiel, PhD, food scientist, consultant, and educator.
This impressive nutrient profile lends them to supporting immune, metabolic, heart, skin, and overall health. And while the unsaturated fats in nuts and seeds help lower cholesterol levels, dull the blood sugar response, and decrease systemic inflammation, they are also the primary culprit for why nuts are so prone to spoilage.
Fat molecules are composed of carbon, hydrogen, and oxygen atoms bonded together in a specific fashion. “The term ‘unsaturated’ simply means that the fat molecules have double bonds between carbon atoms, whereas saturated fats have single bonds. Unfortunately, these double bonds make the fat susceptible to oxidation or rancidity,” explains Thiel.
She goes on to explain that the process of oxidation is a set of chemical reactions where fat is broken down, forming undesirable flavor molecules. “We usually perceive these flavors as rancid or reminiscent of cardboard or paint,” she adds. Rancid nuts and seeds can also classically taste sour and bitter.
But beyond the perishable fats found in nuts and seeds, these popular ingredients are also susceptible to fungal growth, including mold and yeast. And unfortunately, this kind of mold is typically invisible to the naked eye—unlike that found on bread or dairy products. Pistachios and peanuts are some of the most susceptible nuts to mold growth. However, a 2015 study assessing 64 tree nut samples found walnuts to have the highest mold and yeast counts, and pecans to have the lowest.
The vast majority of mold and yeast growth found on nuts and seeds won’t result in illness after consumption. However, there have been instances where harmful molds, like aflatoxin on peanuts, have resulted in food recalls over the years.
The Best Way to Store Nuts and Seeds
Thankfully, through smart storage, we can increase the chances that we won’t accidentally snack on a moldy or rancid nut or seed.
“Oxidation is spurred along with oxygen and light, so you want to keep your nuts and seeds away from both of these,” says Thiel. She also adds that heat can accelerate the oxidative process.
“These stipulations are even more important if the nuts or seeds are already ground, as ground particles have even more surface area that can interact with oxygen, be hit by light, or increase in temperature,” Thiel adds.
Given these parameters, nuts and seeds are best stored in airtight, sealed food storage containers to keep oxygen away from them as much as possible. A dark, closed cupboard or pantry can technically be a safe place for your nuts and seeds to avoid light exposure. However, the fridge and freezer trump the pantry as a dark environment with minimal air flow and very low temperatures, slowing the fat oxidation process way down.
How Long Can You Store Nuts and Seeds?
The proof is in the pudding when we compare the shelf life between these different storage environments. Nuts and seeds of all varieties stored at room temperature have an average shelf life of somewhere between one and three months. In the refrigerator, these healthy fat sources will stay fresh for approximately six months.
However, the freezer really reigns supreme when it comes to nut and seed storage, as these snack time favorites can maintain freshness for upwards of a year (or even two!) in this setting. Plus, frozen nuts and seeds have an almost indistinguishable texture and flavor from those stored at room temperature.
Tips for Boosting Shelf-Life
While cold storage is the ultimate hack for increasing the freshness of your nuts and seeds, there are few other helpful tricks of the trade.
The first of which is to steer clear of bulk bins. While buying in bulk is a fantastic financial and environmental decision, nuts and seeds are best bought at the grocery store. This is because there’s no way of knowing how long they’ve been sitting in those bins that aren’t airtight. Individually-packaged nuts and seeds at the grocery store are almost always sold in sealed, airtight containers and (usually) are not sitting on a shelf with direct sunlight.
Grind any nuts or seeds at home as opposed to buying them pre-ground. This will help ensure optimal freshness and will likely save you money, as the more processing a whole food undergoes, the higher the price often is. Be sure to store any ground nuts or seeds in the freezer or fridge!
Controlling mold is a little tricker. While all the aforementioned tips will certainly help mitigate mold growth, there aren’t telltale signs, like off-putting flavor, that clue us in to whether or not mold is present on our nuts or seeds. If you’re really concerned about mold for any reason, you can soak your nuts or seeds in water for two hours and then either roast them until golden brown, or dehydrate them at 115 degrees for eight hours. These steps will help reduce or eliminate any mold growth.
The Bottom Line
Nuts and seeds are undoubtedly convenient and tasty sources of several important nutrients. However, their impressive nutrient density is also what makes them particularly prone to rancidity and mold growth. Through smart storage in cold, dark, airtight environments as well as soaking and/or roasting prior to enjoying, we can rest assured that these snackable favorites will not only taste delicious but will be low or free from mold.
