Back in the 1800s, sour and sweet were a hot item. Americans drank shrubs and switchels — refreshing mixes of vinegar, water, spices lightly sweetened with honey, sugar or molasses. Southern households preserved their fruits in vinegar. And some of the nation's most popular berries were tangy — like the famed Klondike strawberry and tart cherries that came in eight different varieties. But by the middle of the 20th century, these tart-sweet delights had all but vanished.
It has taken a long time, but sour is returning — in switchels, tangy Greek yogurt, whey beverages, fruit vinegar and sour beers. Why? It seems we're finally rebelling against the sugar that now saturates us. But that's not all — our palates are growing more sophisticated, thanks to globalization, and we've rediscovered the health benefits of fermented foods.
First came immensely successful sugarcane plantations that released a flood of cheap sugar in the early 1800s. "Households began preserving all the produce from their orchards in sugar instead of vinegar," says Shields.
Then, around 1870, beet sugar, which was even cheaper and easier to grow than cane, arrived on the scene. Granulated sugar, most often made from beets — white, sweet, and easy to pour — was soon to be found in boxes, bags and packets everywhere.
But what really made sugar ubiquitous, Shields believes, was Prohibition. "The merriness and revelry of the social world evaporated overnight and people turned to sugar instead of alcohol," he says. Around that time, sweet-sour cherries and strawberries — fruits beloved for 400 years — died a quick and silent death. In their place came a procession of berries bred for sweetness.
Of course, once sugar became more abundant and affordable, we could hardly resist it. A love of sugar is writ into our biology — receptors on our tastebuds as well as specialized cells in the digestive tract release feel-good hormones that create the exquisite experience we associate with sweetness, according to molecular biologist Robert Margolskee of Monell Chemical Senses Center in Philadelphia.
New Belgium's Lips of Faith La Folie is one of the sour ales now on the U.S. market.
And over the last century, our food has gotten sweeter and sweeter. Today's sweet corn has been bred to be almost 40 percent sugar, and a handful of sweet apples dominate the market.
"In a culture of easy sweetness," writes Michael Pollan in The Botany of Desire, "...even the touch of acid that gives the apple's sweetness some dimension fell out of favor."
But increasingly, we're realizing that the American habit of consuming 22 teaspoons a day of sugar on average is seriously unhealthy. "Consumers are more and more concerned about eating too much sugar," says food science analyst Stephanie Mattucci, of the global market research firm Mintel. And the science backs those fears up: a diet high in sugar has been linked to high blood pressure, heart disease and diabetes risk.
Meanwhile, there's new evidence that sour, fermented foods may enhance digestion, balance gut flora and boost the immune system. And such claims have fueled sales of tangy Greek yogurt, Mattucci says. In the beverage aisle, switchels (a blend of apple cider vinegar, water, sweeteners and sometimes spices), shrubs, sour beers, vinegar drinks, kefir and sour whey drinks are all making small inroads.
Today millennials are buying foods with sweet and sour blends, says Mattucci. One reason is that they have been exposed from a young age to a range of far more intense global flavors than their parents — Mintel's research shows that 70 percent of older millennials consider themselves adventurous eaters and open to trying new flavors, while 46 percent like fermented, sour foods. "We've come to fear sugar, and so sour appeals to us," says Mattucci. "We perceive it as more authentic, less sugary, and healthier."
Just as there is a biology of sweet, there is a powerful drive for sour: Extreme sour tastes are preferred by children (Sour Patch Kids, anyone?) more than adults, and sour-loving children have more adventurous palates overall, according to research by Djin Gie Liem and Julie Mennella of Monell Chemical Senses Center.
We may even see a revival of the Klondike strawberry and the sweet-tart cherry, says Shields, who is working with horticulturist Bryan Ward of Clemson University in South Carolina to grow a batch of Klondikes.
As for cherries, Shields says, "People are searching all over Appalachia now for me for the Morello sour pie cherry. I'm sure it is still out there somewhere. And I'm trying to get the tart Hick's Everbearing Mulberry back on the southern landscape." Those were fruits that posed a sort of delicious paradox for the tongue — a harmony of taste that we may just be ready to embrace again.
Jill Neimark is an Atlanta-based writer whose work has been featured in Discover, Scientific American, Science, Nautilus, Aeon, Psychology Today and The New York Times.