Coffee's antioxidant power highest in medium roasts, not lightest, study finds

Many coffee drinkers meticulously adjust water temperature, brewing time, or method, believing these details maximize antioxidants. However, a physician suggests the most significant factor is actually the roast level of the beans. Dr. Wang Ssu-heng of Hengxin Rehabilitation Clinic points to foreign research indicating that while lighter roasts are often thought to retain more antioxidants, the reality is more nuanced.

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The key factor that truly affects the total antioxidant capacity of coffee is not the brewing method, but the roast level.

The primary antioxidant in coffee is chlorogenic acid, which is sensitive to high temperatures. Deeper roasting destroys more of this compound, meaning darker roasts have less. However, the roasting process also creates "melanoidins," another type of antioxidant, through the Maillard reaction. While darker roasts degrade chlorogenic acid, they simultaneously produce more melanoidins, partially compensating for the loss.

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The bean is roasted deeper, the chlorogenic acid is destroyed more; generally speaking, light roast retains the most, dark roast has the least left. Therefore, the amount of polyphenols you drink is not determined by whether you use pour-over or drip, or brew for 3 minutes or 5 minutes, but by how well-roasted the beans you buy are.

This interplay between chlorogenic acid degradation and melanoidin production results in the highest total antioxidant capacity falling in the "light to medium roast" range. Roasting too light or too dark reduces the overall antioxidant content. Therefore, for those seeking the maximum antioxidant benefit, the sweet spot lies between light and medium roasts, rather than exclusively favoring the lightest options.

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Roasting is destroying chlorogenic acid on one hand, and on the other hand, it is helping to 'produce' an antioxidant called 'melanoidin'. Actually, it is a product of the Maillard reaction, the thing that makes coffee turn brown and gives it a charming aroma. So, although dark roasting reduces chlorogenic acid, melanoidins help to bring some back.

Regarding brewing methods, while they do have an impact, it's less critical than the roast level. Espresso, despite its short brewing time, boasts the highest antioxidant concentration per milliliter due to its intense concentration. For pour-over methods, around three minutes appears to be optimal. Dr. Wang concludes that focusing on the roast level, rather than obsessing over brewing details like water temperature or time, offers a more effective and cost-efficient way to maximize antioxidant intake from coffee.

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The result of the pull of these two forces is that the total antioxidant capacity of the entire cup of coffee peaks right in the middle of 'light to medium roast'. Too light or too dark, and the antioxidant capacity is actually lower.