Scientists Upcycle to Enrich Milk Chocolate with Antioxidants

Researchers report a new way to combine milk chocolate with waste peanut skins and other wastes to boost its antioxidant properties.

While milk chocolate is a consumer favorite worldwide, prized for its sweet flavor and creamy texture, it isn’t considered healthy food. In contrast, dark chocolate has high levels of phenolic compounds, which can provide antioxidant health benefits, but it is also a harder, more bitter chocolate.

“The idea for this project began with testing different types of agricultural waste for bioactivity, particularly peanut skins,” says Lisa Dean, Ph.D., the project’s principal investigator. “Our initial goal was to extract phenolics from the skins and find a way to mix them with food.”

When manufacturers roast and process peanuts to make peanut butter, candy and other products, they toss aside the papery red skins that encase the legume inside its shell. Thousands of tons of peanut skins are discarded each year, but since they contain 15% phenolic compounds by weight, they’re a potential goldmine of antioxidant bioactivity. Not only do antioxidants provide anti-inflammatory health benefits, but they also help keep food products from spoiling, the research shows.

“Phenolics are very bitter, so we had to find some way to mitigate that sensation,” Dean says. In fact, the natural presence of phenolic compounds is what gives dark chocolate its bitterness, along with less fat and sugar compared to its cousin milk chocolate. Dark varieties are also more expensive than milk ones because of their higher cocoa content, so the addition of a waste like peanut skins provides similar benefits for a fraction of the price. And peanut skins are not the only food waste that can enhance milk chocolate in this way; the researchers are also exploring the extraction and incorporation of phenolic compounds from used coffee grounds, discarded tea leaves and other food scraps.

To make sure their new confection would pass gastronomic muster, the researchers created individual squares of chocolate with concentrations of phenolics ranging from 0.1% to 8.1% and had a trained sensory panel taste each one. The goal was to have the phenolic powder be undetectable in the flavor of the milk chocolate. The taste-testers found that concentrations over 0.9% were detectable, but incorporating the phenolics at 0.8% resulted in a good compromise of a high level of bioactivity without sacrificing flavor or texture. In fact, more than half of the taste testers preferred the 0.8% phenolic milk chocolate over the un-dosed control milk chocolate. This sample having higher chemical antioxidant activity than most dark chocolates.

While these results are very promising, Dean and the team also acknowledge that peanuts are a major food allergy concern. They tested the phenolic powder made from the skins for the presence of allergens, and while none were detected, they say that a product containing peanut skins should still be labeled as containing peanuts.

While commercial availability of their boosted chocolate is still a ways off and subject to corporate patents, they hope that their efforts will eventually lead to better milk chocolate on supermarket shelves.

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