Abstract
The present study evaluates natural composition of Serbian roasted hazelnut skins (HS) with potential role in application as functional nutrient of various food products. Total phenols (TPC) and flavonoids contents (TFC) in HS extracts obtained with different ethanol concentrations (10%—I, 50%—II and 96%—III) and their antioxidant activities were investigated. The highest total phenols content (706.0 ± 9.7 mgGAE/gextract) was observed in 96% ethanol HS extract. Ethanol HS extracts showed very high antioxidant activity with effective concentrations (EC50) ranged between 0.052 and 0.066 mg/mL. The phenol and flavonoid content of roasted HS extracts I–III was determined by HPLC-ESI-MS/MS analyses. Contents of lipids, proteins, carbohydrates, metals, and C, H, N, S elements in roasted HS were also determined. Relatively high C/N, C/P and C/N/P ratios, rich metal contents and fatty acids composition indicated that hazelnut skin might be a good candidate for use as either human or fungal functional nutrient. In addition, possible application of phenolic HS extracts as UV booster was studied by recording UV spectra (220–440 nm) of 10 mg/L of HS extracts I–III combined with 10 mg/L of chemical sunscreen agent benzophenone-3 and in vitro sun protection factor (SPF) was calculated.
Highlights
IntroductionHazelnuts are one significant commercial crop in the past decade due to the great world application in confectionery industry (dairy, bakery, and chocolate products), as well as in cosmetics and pharmaceuticals
Hazelnuts are one significant commercial crop in the past decade due to the great world application in confectionery industry, as well as in cosmetics and pharmaceuticals
Proteins and ashes contents of hazelnut skins (HS) were shown on dry weight basis and they are similar to reported data [11,25,26]
Summary
Hazelnuts are one significant commercial crop in the past decade due to the great world application in confectionery industry (dairy, bakery, and chocolate products), as well as in cosmetics and pharmaceuticals. It is well known that 90% of hazelnuts (C.avellana L.) are used in food industries as shelled nuts [5,6], and during hazelnut industry production some by-products are produced (shell, green leafy cover, and skin). Hazelnut skins are the main by-product after roasting in the hazelnut industry which account for 2.5% of the total nut weight [7,8]. Some studies have reported that this waste material can find application as functional food ingredients regarding hazelnut skin richness in polyphenols and dietary fiber [7,9]. Published data indicated that roasted hazelnut skin contained the highest content of total phenolics and has the highest antioxidant activity, followed by natural and roasted hazelnuts [8]. Galanakis et al showed potential of application of recovered phenols from olive mill wastewater as UV booster in cosmetics and possibility to reach desirable SPF value by addition of estimated amount of olive phenols [16,17]
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