Hazelnut Shells as Source of Active Ingredients: Extracts Preparation and Characterization

Area of Science:

• Agricultural Waste Valorization
• Phytochemistry
• Food Science

Background:

• Hazelnut shells are a significant agricultural byproduct, primarily used for heating.
• These shells contain valuable polyphenolic compounds with potential health benefits.
• Optimizing extraction methods is crucial for unlocking the phytochemical potential of hazelnut shells.

Purpose of the Study:

• To investigate the impact of different extraction methods (maceration, ultrasonic bath, high-power ultrasonic) on the phenolic profile and concentrations in hazelnut shell extracts.
• To evaluate the influence of extraction parameters such as temperature, time, and preventive maceration.
• To characterize the chemical composition, antioxidant, and antimicrobial activities of the obtained extracts.

Main Methods:

• Extraction of phenolic compounds from hazelnut shells using maceration, ultrasonic bath, and high-power ultrasonic techniques.
• Optimization of extraction parameters including temperature, time, and the use of preventive maceration.
• Chemical analysis for identification and quantification of phenolic compounds (e.g., gallic acid, chlorogenic acid, protocatechuic acid, catechin).
• Assay of antioxidant and antimicrobial activities against relevant bacterial strains (e.g., B. subtilis, B. cereus).

Main Results:

• Eighteen different phenolic compounds were identified and quantified, with gallic acid being the most abundant.
• Preventive maceration positively influenced the extraction of various compounds, irrespective of the primary extraction method.
• High-power ultrasonic extraction showed variable effects on compound yield depending on the specific compound and extraction duration.
• All extracts exhibited antioxidant activity, particularly those obtained through maceration.
• Several extracts demonstrated significant inhibition against Bacillus subtilis and Bacillus cereus.

Conclusions:

• Hazelnut shells are a valuable source of bioactive polyphenols with demonstrated antioxidant and antimicrobial properties.
• Extraction methodology significantly influences the phenolic composition and bioactivity of hazelnut shell extracts.
• Preventive maceration is a beneficial pretreatment for enhancing polyphenol extraction from hazelnut shells.
• These findings support the valorization of hazelnut shell waste into functional ingredients for health-related applications.