Abstract
Hazelnut shells represent a waste material (about 42% of the total biomass) deriving from hazelnut harvest. These are mainly used as a heating source; however, they represent an interesting source of polyphenols useful in health field. The impact on phenolic profile and concentrations of hazelnut shell extracts obtained by three extraction methods (maceration, ultrasonic bath, and high-power ultrasonic), as well as temperature, extraction time, and preventive maceration, was studied. The prepared extracts were characterized in terms of chemical composition, antioxidant and antimicrobial activities. Eighteen different phenolic compounds were identified and quantified by chemical analysis and gallic acid was the most abundant in all the extracts analyzed. Other relevant compounds were chlorogenic acid, protocatechuic acid and catechin. Preventive maceration had a positive effect on the extraction of different types of compounds regardless of the method performed. Application of the high-power ultrasonic method had different effects, either positive or negative, depending on the type of compound and extraction time. All the prepared extracts showed antioxidant activity especially those prepared by maceration, and many of them were able to inhibit the growth of both B. subtilis and B. cereus.
Highlights
Corylus avellana L. are widely cultivated, especially in Turkey, Italy andSpain, as kernels represent a source of many compounds, such as proteins (10–20%), fatty acids, phospholipids, sterols, amino acids, sugars, vitamins, minerals, flavonoids, phenolic acids [1,2,3,4]
Other major polyphenols found in the extracts were chlorogenic acid, rutin, and protocatechuic acid at a maximum concentration of 1345.5, 2611.0, and 1794.0 μg per gram of extract, respectively
The aim of this work was to reuse a waste material, the hazelnut shells, as a source of active ingredients to be used in the health field
Summary
Corylus avellana L. (hazelnuts) are widely cultivated, especially in Turkey, Italy andSpain, as kernels represent a source of many compounds, such as proteins (10–20%), fatty acids (e.g., oleic and linoleic acids), phospholipids (e.g., phosphatidylcholine), sterols (e.g., sitosterol), amino acids (e.g., arginine, leucine, glutamic acid), sugars, vitamins (vitamins B1, B2, B6, niacin, ascorbic acid, folic acid, α-tocopherol), minerals, flavonoids (quercetin, myricetin, kaempferol, eriodictyol, catechin, epicatechin, gallocatechin), phenolic acids (gallic acid, caffeic acid, p-coumaric acid, ferulic acid, sinapic acid) [1,2,3,4]. (hazelnuts) are widely cultivated, especially in Turkey, Italy and. Hazelnut cultivars show a high level of genetic diversity for traits such as vigor, growth habits, nut size, shape and shell thickness. Cultivars most commonly used in food industry are Tonda Gentile delle Langhe ( named Tonda Gentile Trilobata), Tonda Gentile Romana, Tonda di Giffoni, S. Mortarella, and Riccia di Talanico, which are cultivated in Italy. Tonda di Giffoni and Tonda Gentile delle Langhe have gained the European Protected Geographical Indication (PGI) label, and they are known as “Nocciola di Giffoni” and “Nocciola Piemonte”, respectively [1]. Hard shells, green leafy covers and hazelnut tree leaves are by-products of the roasting, cracking, shelling/hulling, and harvesting processes, respectively [1]
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