Why beans can be hard to digest, and what a Sask. researcher is doing about it

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14 hours ago

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As humans, we've gone to great lengths to overcome legumes' natural defences. We have the tenacity of our forebears to thank every time we fill a bowl with chili or swipe refried beans with a tortilla. Take lupins, which require boiling and washing for a week while frequently changing the water to make them palatable. Even then, they don't soften, but no need to worry. Do as the Italians do and pop them like olives as a bar snack.
For less needy legumes, such as pinto beans or chickpeas, the question of whether to soak or not often rears its head. There are supporters in both camps, and though it's not strictly necessary, there's one compelling reason to soak beans and peas: digestibility.
Legumes contain 'antinutrients,' such as oligosaccharides — the reason beans can't shake the 'musical fruit' moniker — that prevent animals (including humans) from fully digesting them. Soaking helps reduce these compounds, making legumes more digestible.
With a little bit of planning, soaking is perfectly doable at home. (Forethought isn't always required to enjoy beans, of course. Just open a can.) But it complicates things in an industrial setting, says Tolen Moirangthem, a PhD student at the University of Saskatchewan (USask) College of Engineering and the lead author of a recent study published in Innovative Food Science & Emerging Technologies that found a better method with big potential.
Soaking beans overnight — 'even two days, let it ferment a little bit' — does the trick at home, says Moirangthem. But on an industrial scale, with multiple tons of legumes, that's a huge amount of time and risk. 'If water is involved, there are microbes coming in, there's bacteria coming in, all sorts of stuff coming in. So if anything goes wrong, my entire sample is off. It's gone,' says Moirangthem.
'We're always looking for an alternative. Is it less time-consuming, faster, easier to handle? Those are the things that matter when it comes to scaling up.'
Moirangthem and a team of researchers from the USask Department of Chemical and Biological Engineering devised a heating method using radio frequency (RF) waves. Instead of up to two days, their process takes five minutes. In addition to being efficient, it's also more effective at reducing antinutrients and eliminating negative flavours than current techniques.
The large ovens that food processing companies currently use to heat beans and peas can burn the outside of the legumes before the inside is hot enough to deactivate the antinutrients. The USask researchers found that their selective heating method, which Moirangthem compares to microwaves, reduced the amount of an antinutrient (trypsin inhibitors, proteins) by 81 per cent.
Since their method works without water, there's no soaking or boiling. 'We're trying to explore how we can do it in a dry way,' says Moirangthem. The goal is to produce a digestible, plant-based protein that can be used as an ingredient in burger patties and protein powders and added as a flour in bakeries.
Moirangthem has been studying food for the past 15 years, driven by a mission to bolster food security. 'With the global population increasing at this exponential rate, there will be times, in the near future, that we don't have enough food for people,' he says. 'How can we fight this? How can we (make sure) everybody gets a little bit to eat, at least to survive, and it has to be nutritious.'
He sees potential in legumes to meet the world's protein needs cost-effectively and sustainably. Since dairy and meat are perishable, they're more fragile to work with, Moirangthem highlights. On the other hand, dried peas and beans are non-perishable, have a long shelf life and 'can still deliver similar nutritional protein content.'
With all their promise, Moirangthem adds that legumes present a few challenges. For one, the functional properties of the protein. 'It's way easier to make a dairy-based protein supplement or dairy-based protein product because the functional property supports product manufacturing, and it doesn't require a lot of processing before we can utilize it.' Plant-based protein takes more work. 'We're trying to find how we can enhance the functional properties of proteins in beans so that we can actually go on par with (animal protein).'
Then, there's digestibility and the issue of antinutritional properties, which interfere with our ability to absorb all of the legumes' nutrients.
Moirangthem's research has shown that antinutrients can be reduced using RF heating. 'My study just scratched the surface, but it has potential.' He plans to continue researching the method and explore what other food processing operations it could replace. He also wants to go deeper into antinutrients and study the effect of RF heating on specific properties.
Moirangthem highlights that Canada's ample farmland could make it a global nutrition hub. 'If we come together and invest in the right places and work on the right ideas, I think we can do a lot of good things,' he says, noting that he'd like to see more collaboration between academia and industry.
'Otherwise, all the research we do in the lab remains in the lab. We need to work hand in hand, and government policies to encourage such projects or such sustainable approaches would be a good stepping stone.'
Should you soak your beans?
Radio frequency machines like the one Moirangthem and his colleagues use in the lab are meant for industrial use. 'It's a huge setup.' So, what's the best way to ensure that the legumes you cook from dried at home are as digestible as possible?
'The best thing is traditional, very traditional, and easy to do. Soak it in water for a couple of days (at room temperature). That's it,' says Moirangthem. Cooks in his native India push it even further, fermenting legume-based batters for dishes such as dosa or idli. 'It's very easily digested.'
As you probably already know from experience, soaking beans isn't necessary. You can have a perfectly enjoyable legume-rich meal without planning ahead. However, as food writer Joe Yonan writes in his 2020 book, Cool Beans, 'just because you don't have to soak beans before cooking doesn't mean you shouldn't.'
Yonan refers to soaking as 'the great bean equalizer,' acting as insurance if your legumes are old, and resulting in more even cooking and less time on the stove. Not to mention, as discussed above, soaking reduces some of the antinutrients, making legumes more digestible. (Make sure to discard the soaking water and cook the beans in fresh water.)
That said, if soaking will prevent you from eating beans, take the shortcut. Most Canadians only get half as much fibre as they need each day. Legumes, such as beans, chickpeas and lentils, are an excellent source, and nutrition experts recommend eating more of them. So, don't let soaking stand in your way of joining the leguminati.
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