engleski

Apricot kernels – important food by-product

Introduction. Nowadays, a tendency for reducing food industry waste is becoming more prominent due to a growing interest for utilization of food industry by-products for various purposes. These by- products contain many potentially useful substances and they could become significant raw materials in the production/development of new products. Apricot kernels as by-products of processing are a valuable source of bioactive components like amygdalin, tocopherols, phenolic compounds and fatty acids. Some of them were studied in this research. Materials and Methods. Apricot kernels were obtained from Association of fruit brandy producers (Kneţevi vinogradi, Croatia). The initial oil content in apricot kernels was determined by Soxhlet extraction system using n-hexane as a solvent. Crude oil was obtained by cold pressing of apricot kernels on the laboratory screw press, and its oil quality parameters, namely, peroxide number, free fatty acids, moisture, insoluble impurities, iodine number and saponification number were determined. Furthermore, oil from apricot kernels was obtained also by supercritical CO2 (SC-CO2) extraction at pressure of 300 bar, temperature of 40°C and CO2 mass flow of 2 kg/h. The oil was collected every hour during extraction process (total extraction time was 5 hours). The oils obtained by screw pressing and with SC-CO2 were analysed for fatty acid composition, total tocopherols and amygdalin concentration. The apricot kernel extract was produced using 50% ethanol solution and was analysed for antioxidant and antibacterial activity, as well as amygdalin concentration. Antioxidant activity of extracts was determined by DPPH method. Antibacterial activity was conducted against four test bacteria strains: Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. It was assessed in terms of minimum inhibitory concentrations by a modified broth microdilution method. Fatty acid composition was determined by gas chromatography with flame ionization detector (GC-FID). Tocopherol concentrations were performed on reversed-phase High Performance Liquid Chromatography (HPLC) with fluorescence detection (FLD) and amygdalin concentration by HPLC with UV detection. Results. The initial oil content in apricot kernels was 49.60%, and moisture content 6.87%. The moisture content in crude cold pressed apricot kernel oil was 0.13%, peroxide number 0.49, free fatty acids 1.78, insoluble impurities 0.46%, iodine number 103.45, and saponification number 192.11. Concentration of total tocopherols during SC-CO2 extraction decreased from first collected fraction to the last, precisely from 2.52 mg/g of oil to 0.50 mg/g of oil. However, the concentration of total tocopherols in cold pressed apricot kernel oil was significantly lower (0.94 mg/g of oil) compared to SC-CO2 oil, while α-tocopherol was not detected. Fatty acid composition showed prevalence of palmitic, oleic (cis-9) and linoleic (cis-9, 12) acid, specifically 5.93%, 57.33% and 33.81% in all SC- CO2 extracts, which showed a great similarity to values of oil obtained by cold pressing.

apricot kernels, by-product, extraction, bioactive components

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