engleski

Effect of different drying techniques on bioactive profile and antioxidant capacity of basil (Ocimum basilicum L.)

Worldwide, basil (Ocimum basilicum L.) is one of the most important culinary herbal crops, and is produced for fresh or dry leaf, essential oil and seed markets. Apart from culinary value, basil has attracted considerable interest among researchers during the last decade due to its bioactive properties. Strong antioxidant activity, ascribed to high levels of polyphenolic compounds, as well as health beneficial properties, including anticancerogenic, antimicrobial, anticonvulsant and stimulative to digestion activities, support the importance of maintaining high levels of bioactive compounds of basil. In basil processing, most conventional drying techniques, such as air drying, use relatively high temperatures for substantial amount of time, causing losses of volatiles and flavour, changes in colour and texture and deterioration of bioactive substances, which results in lower quality of the final product. In that order, alternative non-thermal drying techniques are increasingly being considered for commercial applications, since low temperature and low oxygen environment reduce heat-induced and oxidative damages of the material during processing. Therefore, the aim of this study was to compare the effect of three different drying techniques (air-drying, freeze-drying and CO2 drying) on the bioactive potential of basil, and to determine the optimal processing conditions that provide the highest level of basil's native bioactive compounds. The contents of total phenols, total flavonoids and total chlorophylls (chlorophyll a and chlorophyll b), as well as the antioxidant capacity, using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging assays, were determined by UV/Vis spectrophotometric methods. Phenolic acids in fresh and dried basil samples were identified and quantified using reversed phase high performance liquid chromatography (HPLC-PDA). Total phenol and flavonoid contents of basil samples varied between 10.55 – 35.01 mg GAE/g DM and from 4.30 to 18.70 mg GAE/g DM, respectively. The antioxidant capacity of basil samples ranged from 45.69 to 207.59 µmol Trolox/g DM (determined with DPPH assay) and from 75.48 to 215.66 µmol Trolox/g DM (determined with ABTS assay). Among the 4 identified phenolic acids (caftaric, caffeic, chicoric and rosmarinic acid), rosmarinic acid was the most abundant in all analyzed samples. According to the obtained results, freeze drying was recognized as the most suitable technique for preservation of polyphenolic compounds, providing the highest levels of bioactive compounds and antioxidant capacity in dried basil samples, with values closely comparable to the ones obtained for fresh basil. Regarding the CO2 drying technique, the combination of 40 °C during 2 hours, and 80 and 100 bars, were found to be the most efficient drying conditions for maintaining the native bioactive composition of basil (in accordance with the one obtained for the freeze dried sample). Air drying of basil resulted with the lowest content of phenolic compounds and chlorophylls. Taking into account that freeze drying is rather expensive process, the obtained results imply the need for further development and optimization of CO2 drying technique in this field, especially considering the high quality of final dried product.

Antioxidant capacity; Basil; CO2 drying; Freeze-drying; Polyphenols

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