Milk chocolate remains a global favorite for its irresistible sweet, creamy taste. Yet, it's not known for health benefits. In contrast, dark chocolate boasts high levels of phenolic compounds that deliver antioxidant properties, though its bitterness and firmer texture limit its appeal. Now, experts from the USDA have developed a method to fortify milk chocolate with antioxidants derived from peanut shells and other food waste.
“The idea for this project started with testing different types of agricultural waste for bioactivity, especially peanut shells,” said Lisa Dean, Ph.D., the project's principal investigator. “Our original goal was to extract phenols from the skin and find a way to mix them with food.”
During peanut roasting and processing for butter, candy, and more, manufacturers discard the papery red skins enclosing the nuts. Thousands of tons of peanut shells are wasted annually, despite containing 15% phenolic compounds by weight—a rich source of antioxidants that fight inflammation and preserve food freshness.
“Phenols are very bitter, so we had to find a way to soften that feeling,” Dean explains. This bitterness mirrors dark chocolate's profile, which has less fat, sugar, and higher cocoa content, driving up costs. Incorporating waste like peanut shells delivers comparable benefits affordably. The team is also exploring phenolic extraction from used coffee grounds, discarded tea leaves, and similar byproducts.
To produce their enhanced chocolate, Dean's USDA Agricultural Research Service team partnered with peanut companies for shells, grinding them into powder and extracting phenols with 70% ethanol. Residual lignin and cellulose support animal feed. Similar processes yielded extracts from local coffee roasters' grounds and tea leaves. The phenol powder is then blended with maltodextrin, a standard food additive, for seamless integration into milk chocolate.
Ensuring palatability, the researchers crafted chocolate squares with phenol concentrations from 0.1% to 8.1% and evaluated them via a trained sensory panel. Levels above 0.9% were noticeable, but 0.8% struck the ideal balance: robust bioactivity without compromising flavor or texture. Over half the panel preferred this version to plain milk chocolate, which outperformed most dark chocolates in antioxidant activity.
Though promising, peanut allergies pose challenges. Tests confirmed no allergens in the phenol powder, but products with peanut shells require peanut labeling.
Looking ahead, the team will investigate these antioxidants in nut butters to combat rancidity from high fat content, plus other fortified foods. While commercial antioxidant milk chocolate awaits patents and scaling, it could soon transform supermarket shelves.
