Rethink that cold brew. Hot coffee might be better for your health.

Those claims that cold-brew coffee will cause less heartburn and is healthier than hot brew? They may be exaggerated.

Two overly caffeinated researchers from Jefferson University (the merged Philadelphia University and Thomas Jefferson University) decided to put the claims to the test and investigate the acidity and antioxidant activity of cold-brew coffee. The paper by Niny Rao, an associate professor of chemistry, and Megan Fuller, an assistant professor of chemistry, was published last week in Scientific Reports.

When looking at acidity, the researchers found that the pH levels of both brews were similar and ranged between 4.85 and 5.13 after they tested samples for all the varieties in their study. The higher the pH, the less acidic the brew, and the less likely it would be to cause an upset stomach.

They also found that hot coffee had more beneficial antioxidants than cold brew.

Inspiration for the study came from personal experience.

Rao tried to make a batch of cold-brew coffee at home and brought it to work.

"It did not turn out as well as it could be," she said.

After some discussion in the lab about the industry's marketing efforts and finding there was no research behind the claims that cold brew is better — a big red flag — the pair initiated their study.

They tried to control as many variables as possible, including grind size, roast temperatures, and water chemistry, Fuller said.

They used six coffees from Brazil, Colombia, Myanmar, Mexico, and two regions of Ethiopia that were available locally, and looked for beans that were harvested within a very small area or region.

They were surprised by the results.

"I thought the pHs would be more different," said Fuller. "They were remarkably close."

Fuller noted that the internet allows for the rapid sharing of ideas that are not necessarily valid. That sharing has proved to be a successful business model, though. The cold-brew market has shot up like a rocket, 580 percent from 2011 to 2016. It generated $38 million in 2017.

For the non-coffee drinkers among us, cold brew is made by steeping coarsely ground fresh coffee beans in cool water for an extended period of time. The grounds are then filtered out, using paper coffee filters, a French press, or another such method.

Hot coffee is usually made with water heated to between 195 and 205 degrees Fahrenheit, using one to two tablespoons of ground coffee for every six ounces of water, according to the National Coffee Association. Iced coffee is made by pouring regular hot coffee that has cooled over ice.

The two researchers are big coffee connoisseurs.

Fuller's favorite coffee drink is an Americano with three shots of espresso from High Point Cafe, sometimes with milk and cocoa. Rao gets her organic Mexican medium-roast beans from Golden Valley Farms Coffee Roasters in West Chester and likes a small cup of lukewarm black coffee to start her day.

Next, the researchers will study how long you can safely store homemade cold brew in the refrigerator, Fuller said. Unlike store-bought varieties, it doesn't have preservatives.

"We are interested in looking at microbial populations," she said.

What should coffee drinkers do with the recent study results?

"Don't change your habits," Fuller said. "You enjoy what you enjoy."