At this point in the pandemic, it’s fair to say that the YouTube algorithm knows me pretty well. So when it suggested Food and Wine’s Mad Genius video on toasting nuts in the microwave, I obviously clicked on it.
Weird method, easily testable subject, potential for drastic time savings? Yes please.
I figured this would be a fun, fast little experiment that I could knock out in one or two days and then move on to some bigger projects.
And then I got interested. And did some research. And realized that I wanted more robust answers. And that’s when my fast little test spiralled into something a little more complicated.
Toasting nuts in the microwave: will it work?
Before started testing anything, I wanted to do some research to see if toasting nuts in the microwave made sense from a scientific perspective. I mean, Harold McGee says it works, and I trust him, but I’m a journalist by training and the whole trust but verify thing is hard to get past.
I had a general idea about how microwaves work – a device inside the microwave called a magnetron produces microwaves that bounce around inside the cooking chamber, vibrating the water molecules in the food. The vibrating molecules produce heat, which cooks whatever it is that you’ve put in the microwave, allegedly from the inside out.
However, I also knew that nuts don’t actually contain very much water, which meant either I had missed something, or that something else was going on.
Turns out it was both.
Water molecules vibrate in a microwave field because they behave like tiny magnets – when a wave passes through them, they will flip so that their “poles” line up with the field around them. Fats, like those in nuts, also have these magnetic properties, but they are much much weaker. Think the difference between one of those flat magnetic calendars that remind you to get your oil changed and a rare earth magnet.
I had assumed that because nuts have low water content and because fats generally don’t react much in a microwave field, just plopping them in a microwave wouldn’t have much effect.
You know what they say about assuming.
I’d forgotten about specific heat – the amount of energy it takes to heat one gram of something by one degree Celsius. It’s basically a way of measuring how easy it is to change the temperature of a substance. Water has the highest specific heat of anything you’re likely to come across in your day to day, while the specific heat of fat is relatively low.
Imagine for a moment that the water and fat molecules inside of the microwave are two kids at a college party. For the purposes of the analogy, Water is a pretty big dude – let’s say at least six feet tall and pushing 300 pounds. They like to have a good time, they’re pretty used to the party scene, and they have developed quite a tolerance. Fat, on the other hand, is more petite – 5’ 2”, 5’ 3” and might weigh 110 soaking wet. They’re newly of age and don’t have the experience or tolerance Water does. Both are looking to get a buzz going, but the number of beers it’s going to take to get them there is wildly different.
Water knows who to talk to and where to get drinks, but because they’re so big and because they’ve developed a tolerance, they have to have three or four beers before they start to feel anything. By contrast, although it takes Fat a bit longer to find who to talk to and where to get drinks because they are newer on the scene, it only takes them one beer to develop a buzz.
So it is with the water and fat in the nuts – although the fat molecules in the nuts don’t react as easily to the microwave field as the water molecules, they are easier to heat so the microwaves they do catch go farther and the fat heats up much faster than the water does. In theory, this will quickly and efficiently toast the nuts all the way through.
Designing the experiment
Now that I knew that the idea of toasting nuts in the microwave had some merit, I decided to test it for myself.
And this is where things went off the rails.
I could have just stuck the pecans I had on hand into the microwave and called it a day. But noooooo. I started out thinking I needed a control – I’d toast some nuts using my usual method and see how they compared to the microwave. And then I came across a second method for microwave toasting and wanted to see which worked better. And then I thought I should try it with more than one kind of nut to make sure I got consistent results. And the next thing I knew I had a fully fledged experimental design.
Let me walk you through it.
I decided to test four different methods: toasting in the oven, dry toasting in a skillet, microwave toasting dry, and microwave toasting with a light coating of oil. Each method would be evaluated on total time to completion, evenness of toasting, overall flavor, and perceived ease. I would use raw, untoasted nuts as a control to compare flavor.
I picked which nuts to test by very scientifically seeing what they had at the store – walnuts, hazelnuts, pistachios, pecans, and pumpkin seeds.
Now, my kitchen is obviously not a lab, and I’m working with natural food products which can vary significantly, but I wanted to do my best to control as many variables as I could. This meant that in every case I measured my nuts by weight so I knew each set was as close to identical as I could get. I toasted each set of the five nuts individually, working each method individually (and always in the same order: oven at 350°F, skillet over medium heat, microwave dry, microwave oil), so I could give my full attention to each. I tried, as much as possible, to make sure that I tossed and stirred things at the same time intervals, and I made sure that I always started with a cold pan or plate, so subsequent runs didn’t get a head start from residual heat. And when the nuts had toasted to my satisfaction, I removed them from the hot pan or plate immediately and allowed them to cool completely on metal cookie sheets before I tasted anything.
I timed most runs with a stopwatch, or by adding together the total amount of time I set on my timers when I forgot. Tasting was necessarily subjective, but I did my best to compare fairly and to make sure that my palate was clear before moving on to the next set.
Was this a perfect system?
No.
I’ll freely admit that nuts are the thing I burn most, so I tended to err on the side of underdone if I got nervous. I was tired and bored close to the end, so consistency and precision probably dropped as I went. I also didn’t taste blind, so I’m sure my impressions of the cooking process colored my palate to a certain extent.
Let’s see what I found out, shall we?
How toasting nuts in the microwave stacks up
Time to completion
Let me say this up front: this is the area where my data is the most squidgy. I was focused on pushing the nuts as far as I could without burning them, which meant I often forgot to start my stopwatch and had to retroactively figure out how long things took by adding timer intervals together.
That said, the results are pretty much exactly what you’d expect, and the differences between each method are large enough that I’m not concerned that I skewed the data by lack of to-the-second times.
The oven, with its relatively long preheat time and large heating area, took the longest, averaging just over 23 minutes start-to-finish. If you ignore preheat time, that figure goes down to just over 15.
Toasting in a skillet was faster – over medium heat, it preheats fairly quickly and nuts didn’t take much time to toast, averaging just over six minutes start to finish.
Somewhat unsurprisingly, both methods for toasting nuts in the microwave were fastest. Total time averaged around two minutes, with the fastest runs (the pumpkin seeds) coming in at just 45 seconds.
Perceived ease
I have to admit, the results in this section surprised me. I thought for sure that using the microwave would feel the easiest.
It didn’t.
Because the nuts don’t brown on the outside the way they might in the oven, it was really hard to tell how things were progressing, and because the microwave heats things so quickly, the difference between delicious and charcoal was only a matter of seconds. It was weirdly stressful – I was checking and stirring every 30 seconds and second-guessing myself on whether the nuts would survive another round.
That said, the microwave was still easier than the skillet. If you’re going to toast nuts in a pan you have to keep them moving constantly, or they WILL burn. Sitting the pan on the stove and stirring is ok, but if the nuts aren’t flipping over as you move them around, they will burn on one side regardless. Doing the fancy chef pan toss is a better option because it makes sure everything in the pan is getting flipped around, but that’s definitely a skill you have to practice or you get nuts all over your kitchen (please don’t ask me or my vacuum how I know this).
Perhaps because it is my usual go-to, oven toasting felt easiest to me. Pop the nuts on a sheet tray, give them a gentle toss every five minutes or so, and as long as you don’t forget about them you get nicely toasted results while you focus on other things. It’s easy to see progress because the nuts are getting color on the outside, and the whole process moves slowly enough that you have some leeway to ignore the timer if you need to put something down.
Evenness
I think the photos speak for themselves here. Nothing did a particularly good job getting even color on all the nuts except the oven.
The microwave did ok, with marginal improvement if you tossed the nuts in oil first.
Frankly, the skillet was abysmal. Maybe I’m just bad at toasting nuts this way, but to my eye most came out raw with burnt spots on the high points. Pumpkin seeds were the exception, but they are small, thin, and uniformly sized, which means they heat faster and more evenly.
Flavor
The oven was the clear winner here, producing clear, well-rounded roasty flavors that made every nut I tried taste, well, nuttier. That’s not a great explanation, but if you’ve tasted a well-toasted nut next to a raw one, you know exactly what I’m talking about.
The differences between microwaving with a coat of oil and without were extremely minor, but in general the oil coat produced slightly better-tasting results. Both methods produced a lighter toast than the oven (although, admittedly, this may be because I got scared and pulled the nuts out early), and both had an accompanying acrid, burnt-popcorn flavor that wasn’t particularly pleasant. The oil-coated nuts didn’t have this off-taste as strongly, but it was definitely still there.
Honestly, I can’t say that toasting in a skillet produced any roasted flavor at all. By and large, the nuts tasted raw, with the unpleasant addition of burnt spots. Honestly, this is probably because I didn’t leave the nuts in long enough, but I got spooked by the burning spots, the nuts were smoking, and my downstairs neighbors just had a baby and I didn’t want to set off the fire alarm. In any case, based on the evidence from this test, I cannot recommend this method based on flavor alone.
Final thoughts on toasting nuts in the microwave
Given that I went into this little experiment thinking that there was no way that toasting nuts in the microwave functioned as advertised, I’m honestly pretty surprised at the result. Was it oversold as a method? Yes. But that doesn’t mean that it doesn’t work.
I’m still going to use the oven as my go-to – in my opinion, the results are worth the extra time. That said, if I need only a handful of nuts in an application where they are not the primary flavor, or if I’m not planning on using the oven for anything else that night, I think microwave toasting is a very viable second option.
Honestly, I’m most surprised that the skillet toasting worked as poorly as it did. For something that is often listed as the suggested method for toasting nuts in recipes, I really don’t think it can produce good enough results consistently for the average person, especially given the amount of effort involved. I certainly won’t be using it any longer.
What about you? Will you try this? Is there a method I missed? Is there anything you want me to test in the future? Let me know in the comments.
My mother always roasted with the oven door open. Did that slow it down so you were less likely to go too long or did it help you smell the when they were done? Whichever, I know smell is my best measure of oven roasted nuts.
Keeping the door open is a great idea! I always set a timer because with my oven at home by the time you smelled anything it was too late…
Happy to see a repost of this guide to toasting nuts as we move headlong into a season rife with toasted nuts. Especially to be reminded other options for toasting nuts can be as effective as an oven, which in my house is a very good thing because, as you noted, the oven is often ahead of the timer.