As an aspiring foodie, I’m on the internet a lot. Over the past year or so in the realm of trendy food blogs, everyone who’s anyone is talking about za’atar. Much like the crispy kale trend that reigned the web for several years, za’atar (pronounced like it’s spelled) is all anyone can write about. Za’atar is a staple Middle Eastern spice blend that’s swirled into oils and slathered on meats to add an herby zip at any meal. It’s fantastic, and dunking a crusty pull of bread into olive oil without za’atar involved should be a crime.
Today I’m jumping on the za’atar bandwagon, not to share a recipe, but to talk about a za’atar constituent — sumac. If you grew up in the southern U.S. like me, sumac may bring to mind an itchy rash you got traipsing through the woods as a kid. But the type of sumac in za’atar isn’t the poisonous shrub from the Toxicodendron genus. This sumac, scientifically named Rhus corlaria, grows in subtropical and temperate climates, producing a deep crimson berry that’s ground into a reddish-purple powder with an oh-so-lovely lemon flavor — it’s a bright addition to the savory oregano, thyme and caraway in za’atar.
Sumac has lived a diverse life beyond the spice cabinet for centuries. Oil extracted from its seeds has a tallow-like texture, standing solid at room temperature, and is used to make candles. The plant is used medicinally to treat dysentery and stimulate the appetite. Its bark and leaves are brimming with tannin, a dye-binding agent, natural colorant, and according to recent study out of Turkey, a possible dye removal treatment for textile industry wastewaters.
Sumac leaves’ high tannin levels and wide availability led researchers from Yildiz Technical University to consider them as a novel, low cost adsorbent of a synthetic dye called methylene blue. Methylene blue is commonly used to color everything from leather and silk to paper and plastic, and alongside a host of other dyes, is being released via wastewater into water bodies worldwide.
Synthetic dyes entering aquatic ecosystems can have some ugly impacts. Dye residues prevent light from penetrating water, affecting photosynthetic activity in plant life. They can also have detrimental effects on humans — in methylene blue’s case, increased heart rate, vomiting and diarrhea upon even limited exposure. These aren’t symptoms most of us want brewing in our morning coffee, so its important that industrial effluents containing dye be cleaned before re-entering the water stream.
That’s where sumac’s tannins come in.
Tannins have a chemical structure that heavy metal ions love. Like magnets, tannins attract and cling to these ions as they pass by. Because heavy metals like lead and copper are often used in synthetic dye production, sumac leaves grab and trap the dyes, preventing their residue from entering the environment as waste.
While this “sumac solution” hasn’t been tested on a grand scale yet, the results from this study look promising. Compared to other dye removal adsorbents like activated carbon, sumac is plentiful and cheap, making it a competitive option. And as biosorption becomes a more accepted method for toxin removal, we may have a new reason to love sumac, aside from my beloved za’atar.