Hot coffee delivers more antioxidant benefits than cold brew, research finds

by Colleen Zewe
Medill Reports

As the weather gets colder, caffeine-lovers often switch from cold brew to hot coffee. This switch packs more benefits than just warming you up. New research shows that hot coffee contains more antioxidants than cold.


Chemists Niny Rao and Megan Fuller compared the chemical makeup of hot brew coffee and cold brew coffee. Their findings, published in Scientific Reports, bust some myths that cold brew is better for you than hot coffee. The two researchers are with Jefferson (Philadelphia University + Thomas Jefferson University) in Philadelphia.

Fuller and Rao said that, based on coffee’s chemical profile, the drink has benefits and drawbacks. It is naturally acidic and can thus cause gastrointestinal programs, such as reflux and heartburn. However, the antioxidants in coffee, called CQA antioxidants, have anti-inflammatory effects, leading to “decreased risk of liver, metabolic and neurologic diseases,” their study states.

The chemists, who are self-proclaimed coffee lovers, said they noticed blogs and coffee companies claims that cold brew is less acidic and therefore causes less gastrointestinal problems, and that it has more antioxidants. However, the researchers decided to pursue research to back up these claims, and looked look into the differences between hot and cold coffee themselves.

“The claim is questionable,” Rao said. “Because we are coffee enthusiasts looking to study coffee, our research was driven by these claims made by marketing teams that were not substantiated by any research. We wanted to give knowledge to the consumer.”

Rao and Fuller used commercially available light-to-medium roast beans. They brewed the hot coffee with a French press. They used a New York Times recipe to brew the cold coffee, brewing it for seven hours in a Mason jar before filtering. They tested the coffee’s pH, or general acid level, total titratable acid, and antioxidant levels.

pH

All coffee beverages have a low pH. The lower the pH, the higher the acid level, while a higher pH means something is basic. A pH of 7 means means a substance  is neutral. Water is only of the only substances with a neutral pH. pH measures the concentration of hydrogen ions, or charged atoms, and acidic drinks have more hydrogen ions. Acidic beverages can cause irritation in the esophagus and stomach. The researchers saw claims that cold brew has decreased acidity, making it easier on the stomach. But they found very little difference between the pH levels in hot and cold coffee. All scored a 4 or 5 on a pH  test, giving them almost equal acidity.

pH levels of the different coffee samples (Colleen Zewe/MEDILL)
pH levels of the different coffee samples (Colleen Zewe/MEDILL)

Total Titratable Acid

While pH measures the concentration of hydrogen ions, total titratable acid measures the amount of hydrogen ions that can be neutralized through the addition of a strong base. TA is considered a good indicator of whether coffee will taste bitter or sour because it shows how strong the individual acids in the drink are.

The researchers found that hot coffee has more titratable acids, showing that it probably has more acids in it than cold brew coffee. Though the two types of coffee have similar concentrations of acid, hot coffee has a more diverse mix of acids than cold. The researchers believe that when hot water comes in contact with the coffee grind, it extracts more acids than cold water does, thus giving hot coffee more acids than cold brew, even though they have similar acidity concentrations overall.

“It was great for us to figure out because the cold water that contacts the bean for seven, 10 or 12 hours,” Fuller said. “You would think that if time replaces temperature, you might end up with the same coffee, but it turns out that heat is really crucial to the compounds that make hot coffee taste like hot coffee.”

Total titratable acid concentrations in the coffee samples (Colleen Zewe/MEDILL)
Total titratable acid concentrations in the coffee samples (Colleen Zewe/MEDILL)

Antioxidants

Antioxidants attack free radicals in the body, and free radicals are unbonded, unstable molecules that can cause bodily damage. They can bond with other healthy molecules in the body and cause them to degenerate. Antioxidants found in food help remove free radicals before they wreak havoc.

Fuller and Rao found that hot coffee contains more of the antioxidant caffeoylquinic acid than cold brew. They believe CQA is probably extracted during the heating process, so it is not extracted as much in cold brew.

 

Total CQA levels of the coffee samples (Colleen Zewe/MEDILL)
Total CQA levels of the coffee samples (Colleen Zewe/MEDILL)

However, they emphasized that despite these findings, people should drink whichever coffee they enjoy most.

“A well-balanced diet typically has a reasonable amount of antioxidants, so nobody really has to worry about it,” Fuller said. “If you surveyed 100 people on the street and said, ‘Why do you drink coffee?,’ zero of them are going to say it’s for the antioxidants. They’re all going to say it’s for the caffeine buzz.”

Caffeine content comes from roasting the beans, not the brewing process, so caffeine differs between the beans used, not whether the brew is hot or cold.

Fuller and Rao agreed that ultimately, consumers should know that all coffee is healthy in moderation, but they should be wary of marketing claims that one coffee is healthier than the other.

“We wanted to let people know that they can be curious about what they put in their body. We can measure these things, and we don’t have to rely on what marketers tell us,” Fuller said. “We can get unbiased results and ask questions about things we put in our bodies.”

 

Photo at top: Not only does hot coffee warm you up in the winter, but it also contains valuable antioxidants. (Colleen Zewe/MEDILL)