From Vineyard Waste to Pasta Sauce

Grape pomace is what’s left after the juice has been squeezed out of a grape—skin, seeds, stems, and pulp. Some of the pomace can be repurposed in applications like fertilizer or compost, but most of it is wasted. Given that 20% to 25% of grapes’ weight ends up as pomace after wine is made, and global wine production is around 244 million hectoliters, that’s a lot of waste.

Pomace, which contains vitamins, minerals, and bioactive compounds like polyphenols, as well as fibers and prebiotic oligosaccharides, has many nutritional benefits, and finding ways to use it is an area of active research.

Researchers at Acadia University, which is located in the Annapolis Valley of Nova Scotia, home to a thriving wine industry, wanted to see if adding grape pomace to tomato sauce would be more accepted by wine drinkers than by those who don’t drink wine. The findings from their research were published recently in the Journal of Food Science.

“We did some preliminary work, and we thought that pasta sauce worked really well because people usually drink wine while they’re eating pasta,” says research team member Matthew McSweeney, a professor at the university’s School of Nutrition and Dietetics.

In addition, McSweeney notes that research has shown that familiarity with a product leads to liking it, so he and his colleagues hypothesized that wine drinkers might have a more positive response to pasta sauce formulated with added grape pomace despite the fact that it has a gritty texture and strong flavor, which can be off-putting. They devised a sensory test to see if they were correct. (The bitterness and astringency of grape pomace comes from its anthocyanins, which give grapes their colors.)

Taste Testers Weigh In

The researchers used an off-the-shelf tomato sauce, chosen for the sake of consistency, and pomace from Merlot grapes. They added varying amounts of pomace (3%, 6%, and 9%), and also used a control sauce without any pomace added.

There were two groups of tasters: 44 were regular wine drinkers, and 58 were not. They tasted each of the four samples and rated them for flavor, appearance, texture, and overall liking.

The addition of pomace did produce off-flavors and textures in the pasta sauces, the testers reported. The more pomace in the sauce, the less the tasters liked its flavor and texture.

The 3% version still tasted like a typical tomato sauce, with bell peppers, herbs, and sweetness identified. The 6% was bitter and grainy, according to the tasters, and the 9% was metallic and astringent. But the 9% was also rated as earthy, vegetal, and wine flavored.

As the researchers anticipated, there was a difference between the wine drinkers and those who didn’t drink wine. The wine drinkers gave the pomace-added sauces higher marks for appearance and gave the 3% and 9% sauces much more favorable marks on all factors than those who didn’t drink wine. Interestingly, the 6% version was the only one that was ranked the same by the two groups of testers.

“We did find that people who drank more wine seem to enjoy the taste of the pasta sauce more than non-consumers of wine,” says McSweeney. “We’re pretty excited about that.”

McSweeney’s own estimation of the sauces was positive, even though he’s not much of a wine drinker. He was an outlier—he thinks that the 6% pomace addition is optimal. “The 9% did get a little more earthy and vegetable and bitter, but the 6% or 9% had a little more savoriness and had a little more depth for the flavor in it,” he says.

McSweeney sees opportunities to create formulations of foods to incorporate grape pomace’s qualities. For example, he says, “you could formulate a pasta sauce that optimizes the grape pomace taste.”ft