Lisa Dean is a food technologist with the USDA ARS Food Science and Market Quality and Handling Research Unit in Raleigh, North Carolina. She and her team investigate nutritional content, flavor attributes and shelf-life to maintain and improve the overall quality of peanuts.
In this Q & A, she talks about flavor testing in peanuts as well as work making peanut skins, normally discarded as waste or used in animal feeds, into a food ingredient.
How do you and your team evaluate peanut varieties?
At the Food Science and Market Quality and Handling Research Unit, my group evaluates peanut flavor using Descriptive Sensory Analysis with the Spectrum® method. Each attribute is given a number score and the scores are averaged across the number of panelists, including members of the lab group, students and staff from the Department of Food, Bioprocessing and Nutrition Sciences at NCSU. Everyone on the panel is trained to score the attributes listed in the peanut lexicon, and some members have over 2,000 hours of experience.
We work with the USDA ARS National Peanut Research Laboratory in Dawson, Georgia. Peanut samples are sent there from the various breeding programs around the United States as part of the Uniform Peanut Performance Trials where they are shelled and graded.
Once the samples are sent to us in Raleigh, North Carolina, the peanuts are evaluated for “roastability,” that is, what conditions are needed for optimum roasting and how evenly does the sample roast? The composition, protein, moisture, sugar, fatty acid and vitamin E content is determined using wet chemistry and chromatography.
Peanut skins are usually removed before processing and consumption, but could skins have a benefit to the consumer?
Peanut skins are very high in tannin compounds, which make them bitter and astringent. The compounds present are similar to those in tea, chocolate and cranberries. As a result, most people remove them when eating in-shell peanuts. When making peanut butter, the skins are removed by blanching. If left on, the peanut butter is a darker color with flecks. It is also a stiffer peanut butter that cannot be spread as easily.
The same compounds that cause the bitter flavor also have antioxidant and anti-inflammatory properties in cell culture. They may also have anti-aging and anti-cancer properties. In nature, they serve to reduce insect infestation to some degree due to the bitterness.
Research has shown that these properties can be captured from other food processing waste such as coffee grounds, spent tea leaves, grape pomace, fruit peels, cocoa hulls and similar materials. It would stand to reason that peanut skins could be used in these ways as well.
What ways are you using peanut skins?
Our group has isolated the active compounds from the peanut skins, leaving behind a debittered fiber material that makes a better animal feed ingredient. The tannin compound extract can also be spray-dried to make a functional food ingredient to fortify milk chocolate and to make flavored coatings for peanuts.
USDA ARS scientists have developed a way to use peanut skins to fortify milk chocolate to increase the antioxidant levels. Peanut skins contain phenolic compounds including procyanidins, which have been shown to reduce inflammation and act as natural antimicrobials.
A way has developed to combine soluble extracts of the phenolic compounds with maltodextrin, a starch-based polysaccharide, to make a free-flowing powder that was easier to handle and could control the bitterness. The resulting powder could then be used as a functional food ingredient, albeit, with the caution that the allergenicity of peanuts carries over to peanut skins and subsequent reporting of peanut allergy information on the label.
In taste tests, most consumers could not tell that peanut skins were added to the milk chocolate until the level was well above that where the antioxidant level was equal to dark chocolate. PG