The Toxic Truth Behind Cashews

What's your favorite nut?

While technically not a nut (they're legumes), peanuts are undeniably many people's response to that question. Though almonds dominate American food trends these days — from milk to flour to butter — and walnuts reign supreme in baked goods, my personal favorite, pistachios, shine on their own, in ice cream or baklava. But for many people worldwide, the answer is simple: cashews.

One thing these "nuts" all have in common? They aren't actually nuts. But the cashew has a unique set of botanical characteristics that make it stand out from its fellow false nuts.

A staple in Brazilian, Indian, and Southeast Asian cuisines, cashews have become a favorite among vegans for their high-fat content, which allows them to be transformed into everything from milk to butter to cream and even cheese alternatives. But like peanuts, cashews aren't nuts, and their story is extraordinary.

The Cashew’s Unusual Anatomy

Let's clarify some botanical terminology. True tree nuts are hard-shelled fruits containing a single edible seed that doesn't naturally split open to release their seeds. Examples include chestnuts, hazelnuts, and acorns. Legumes, like peanuts and peas, are seeds grown in pods. Then we have drupes — fruits characterized by a fleshy outer layer containing a harder shell, which itself contains a soft seed. Popular drupes in the "nut" world include almonds, walnuts, and cashews.

Cashews stand out even among drupes. The cashew tree produces distinct pear-shaped cashew apples, with the drupe extending from their bottoms. That "apple" is a false fruit, as it develops from parts other than the flower's ovary and doesn't result from fertilization (now you know what is required to make a real fruit). The drupe itself is the true fruit of the cashew tree, and this is where things get fascinating.

That false fruit is incredibly perishable, leading to the significant waste of cashew apples worldwide. But the real challenge lies in harvesting the valuable seeds within the drupes.

A Hazardous Harvest: The Challenge of Processing Cashews

The process begins with fresh cashews in their protective drupes, which must be spread out to dry in the sun for several days. This drying separates the cashew apple from its drupe and preserves the highly perishable false fruit, which begins to turn within 24 hours of picking.

The transformation continues as workers load the dried drupes into drums and heat them to 350°F (175°C). This crucial step makes the outer shell brittle enough to crack and begins neutralizing the dangerous protective urushiol compounds — the same substance found in poison oak and poison ivy — found in that hard outer shell. These compounds can cause severe chemical burns, and when heated, release toxic fumes that require proper ventilation and protective equipment.

The most delicate part comes next: extracting the cashew from its shell. Workers must apply precise pressure to crack the shell without damaging the kernel inside. Despite technological advances, human hands remain the most effective tools for this task, though it requires heavy-duty protection against any remaining urushiol.

The freed kernels then undergo another drying process before workers carefully remove their final layer — a tough, reddish-brown skin called the testa. Each cashew is then graded by size, color, and condition, with perfect halves commanding premium prices and broken pieces finding their way into processed foods.

While some facilities are modernizing with automation systems, the complex nature of cashew processing resists complete mechanization. Progressive facilities focus instead on improving worker safety through better ventilation and protective gear, though these improvements increase processing costs.

These seemingly simple seeds (remember, they’re not nuts!) represent a remarkable collaboration between humans and nature, transforming one of the plant world's most defensive fruits into a beloved food. So, next time you enjoy a dish of chicken cashew, or snack on some trail mix, take a moment to appreciate the remarkable journey that seed took to reach your tummy.

And while we’re here, hit reply and tell me about your favorite way to use cashews! Personally, I’m a sucker for stir-fired dishes with these fatty seeds.

Next Week on Feed Your Curiosity

What kind of museum keeps a half-cooked hamburger under glass? Next week, I'll take you inside a hidden collection that tells the stories of how epidemiologists solve deadly food mysteries — and why you might want to invest in a meat thermometer.

Thanks for Reading Feed Your Curiosity!

I'm Bryan M. Vance, a writer who hunts down stories that make people say "wait, really?" Every two weeks, I share fascinating tales about our wonderfully weird world — from mind-bending scientific discoveries to bizarre historical footnotes that time forgot.

Got a curious story to share? Hit reply. I'd love to hear what rabbit holes you've fallen down lately.

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