Milk chocolate is loved by consumers all over the world because of its sweetness and creamy texture. This dessert can be found in all types of snacks, but it is not entirely healthy. In contrast, dark chocolate contains high levels of phenolic compounds, which can provide antioxidant health benefits, but it is also a harder, bitter chocolate. Today, researchers report a new method of combining milk chocolate with waste peanut skins and other waste materials to enhance its antioxidant properties.
The researchers presented their results at the American Chemical Society (ACS) Virtual Conference and Expo in Fall 2020. The conference that ended yesterday featured a wide range of scientific topics, with more than 6,000 lectures.
“The idea of the project started with testing the biological activity of different types of agricultural waste, especially peanut skins,” said Lisa Dean, the main researcher of the project. “Our initial goal was to extract phenols from the skin and find a way to mix them with food.”
When manufacturers roast and process peanuts to make peanut butter, candies, and other products, they discard the paper red skin that wraps the beans in their shells. Thousands of tons of peanut skins are discarded every year, but since they contain 15% phenolic compounds, they are a potential gold mine for antioxidant biological activity. Antioxidants not only provide anti-inflammatory health benefits, but also help prevent food spoilage.
In fact, the natural presence of phenolic compounds gives dark chocolate a bitter taste. Compared with cousin milk chocolate, it has less fat and sugar. Dark varieties are also more expensive than milk varieties because of their higher cocoa content, so the addition of wastes such as peanut skins can provide similar benefits and are inexpensive. Peanut skins are not the only food waste that can enhance milk chocolate in this way. Researchers are also exploring ways to extract and incorporate phenolic compounds from waste coffee grounds, waste tea and other food residues.
To create their antioxidant-enhanced milk chocolate, Dean and her researchers at the United States Department of Agriculture (USDA) Agricultural Research Service worked with the peanut company to obtain peanut skins. From there, they grind the skin into a powder and then use 70% ethanol to extract the phenolic compounds. The remaining lignin and cellulose can be used as animal feed for roughage. They also work with local coffee roasters and tea producers to use similar methods to extract antioxidants from these materials to obtain used coffee grounds and tea leaves. The phenolic powder is then mixed with the common food additive maltodextrin to make it easier to incorporate into the final milk chocolate product.
To ensure that their new dessert can pass the food festival, the researchers created a single square chocolate in which the concentration of phenols ranges from 0.1% to 8.1%, and everyone has a trained sense to taste. The purpose is to make the phenolic powder in the taste of milk chocolate undetectable. Taste testers found that concentrations of more than 0.9% can be detected, but incorporation of phenolic resin at a concentration of 0.8% would well impair high levels of biological activity without sacrificing flavor or texture. In fact, more than half of the taste testers preferred 0.8% phenolic milk chocolate to uncontrollable milk chocolate. This sample has higher chemical antioxidant activity than most dark chocolates.
Although these results are encouraging, Dean and his research team also acknowledge that peanuts are a major food allergy problem. They tested the phenolic powder made from skin for the presence of allergens. Although no allergens were found, they said that products containing peanut skin should still be labeled as containing peanuts.
Next, the researchers plan to further explore the use of peanut skins, coffee grounds and other waste products for other foods. In particular, Dean hopes to test whether the antioxidants in peanut skins can extend the shelf life of nut butters, which can rot quickly due to their high fat content. Although the commercial supply of its enhanced chocolate is still far away and needs to be patented by the company, they hope that their efforts will eventually make the milk chocolate on supermarket shelves better.