A Sustainable Alternative for Cosmetic Applications: NADES Extraction of Bioactive Compounds from Hazelnut By-Products

What if the secret to greener cosmetics lies in the leftover shells and skins of hazelnuts? A new study reveals that these by-products, often discarded, are treasure troves of bioactive compounds.

Hazelnut processing leaves behind skins, shells, and defatted flour—by-products that are rich in polyphenols, fibers, and other valuable molecules. Rather than tossing them away, scientists are exploring ways to turn these remnants into ingredients for nutraceuticals and cosmetics.

In this study, researchers compared three natural deep eutectic solvents (NADES)—betaine/sorbitol/water, fructose/lactic acid/water, and fructose/glycerol/water—against a conventional ethanol/water extractant. They paired these solvents with two extraction methods: traditional heat with stirring and ultrasound-assisted extraction.

The results were striking. The betaine/sorbitol/water NADES proved superior for extracting from skins and shells, while fructose/lactic acid/water worked best for defatted flour. Although skins are the least abundant by-product, they boasted the highest polyphenol content and antiradical activity, making them prime candidates for cosmetic applications.

The study also tested the leftover extraction residues for conversion into energy or chemicals. Some materials showed potential for thermochemical conversion, while others were suitable for anaerobic digestion—turning waste into even more value.

Key Points

• NADES outperform ethanol/water for extracting polyphenols from hazelnut by-products.
• Betaine/sorbitol/water best for skins/shells; fructose/lactic acid/water for defatted flour.
• Skins have highest polyphenol content and antiradical activity.