Bread, apples, and even butter (to an extent): These are just a few of the foods that are at the center of the “fridge or leave it on the counter” debate. But what about nuts? Do you leave it on the counter, put it in the fridge, or put it in the freezer?
We all have that extra bag of pecans in the back of the pantry just in case we want to bake. Surely these fat and protein bombs stay safely there for the long haul, right? However, it turns out that based on how the nuts break down over time, there is one storage method that beats the rest.
Can nuts spoil?
Yes – they don’t just spoil, but they go rancid. This may come as a shock, but nuts only keep fresh at room temperature for about three months. Troy Karen Schech, a food scientist at Rutgers University inverse The compounds that give nuts their old-oil flavor can be tasted at very low levels, as small as parts per million or billion.
The problem is that many people get used to the flavor, especially when it’s still at low levels. Schaich brought natural, spoiled peanut butter to her students as an example. She said, “They smelled it and said, ‘Oh, that smell is normal.'” inverse. She says fresh peanut butter tastes “like cardboard” because it lacks the compounds that give it the oily flavor we might be used to. But when those levels get too high, they develop flavors that have a slightly bitter aftertaste.
What makes nuts spoil?
There is a complex chemistry at play when the air interacts with the fat molecules in the nuts. Their physical form affects how quickly they expire. Nuts with a large surface area are prone to rapid rancidity because there are more areas exposed to oxygen. For this reason, walnuts decompose faster because they have the largest surface area. The brain-like edges of the nut create tons of cracks where oxygen can seep out. On the other hand, almonds take longer to spoil because they are so pressed. Its density is greater than its surface area.
At the molecular level, Schaich points to the trans fat content as a major factor. When nuts oxidize or react with the oxygen around them, new compounds are produced. The higher the percentage of unsaturated fats, the faster the nut will oxidize. Nuts that are high in unsaturated fats are full of molecules that are locked in double bonds, which means that the bonded atoms share two pairs of electrons between them instead of just one. Once this double bond is oxidized, it releases molecules called free radicals, which are uncharged molecules that can easily bind to anything around them and form new matter. The free radicals in nuts can synthesize hydroperoxides, aldehydes, and ketones. Hydroperoxides are very sensitive to degradation in heat and light, so they can speed up reactions, while the latter two create that flavor in stale nuts.
Storage conditions can speed up or slow down this process as well. Reactions happen more quickly at higher temperatures, so a refrigerator, or even better a freezer, grinds oxidation almost to a halt, preventing free radicals from forming in nuts. Exposure to light also affects oxidation. Keeping shelled nuts or any other food high in unsaturated fats in direct light will make them go bad faster.
It’s worth considering slowing down the stink because once it starts, it won’t stop. “The problem with stink is once it starts, it’s a chain reaction [that] You go and go and go,” she says inverse.
Is eating rotten nuts harmful?
Eating spoiled nuts is not the same as eating spoiled dairy products or bad seafood. It’s akin to eating stale potato chips—there’s maybe a bit of a taste (if that), but it’s not inducing to miserable, and it won’t cut your feet off your feet.
Hydroperoxides and aldehydes are known to contain some toxic compounds, but from the moment you put the bad nuts in your mouth, your body starts producing enzymes that break down the hydroperoxides, aldehydes, and other oxidation by-products. These enzymes follow your stomach and intestines, bringing them to life at an acidic pH, and largely detoxing those by-products.
“If someone is living on rotten peanuts, rotten potato chips, and all sorts of snacks, that could be a problem,” says Schaich. “As long as you eat a healthy diet and don’t overindulge in a lot of oxidizing foods on a consistent basis, it won’t hurt you,” says Schaich.
What is the best way to store nuts?
In a tightly closed glass container in the freezer. An airtight seal involves removing all oxygen from the inside of the jar. Schaich also says that two or three layers of plastic wrap is another effective method.
Keeping nuts in the shell at room temperature is also an option, but only for six weeks. Schaich says that if you put in some whole walnuts “at Thanksgiving, [they] Maybe they can have a ‘Christmas’ before they offer those flavours.
If you have a dedicated shelf in your cupboard for walnuts, macadamias, almonds, cashews, peanuts, and your other favorites, keeping them there probably won’t do you any harm, assuming you eat a balanced diet. But if you tend to keep your favorite nuts fresh for a long time, consider blending them and storing them in the freezer.