Comparative evaluation of CO₂ drying as an alternative drying technique of basil (Ocimum basilicum L.) - The effect...

In this study the potential of employing CO₂ drying as an alternative to conventional drying techniques of basil was evaluated, with the aim of preservation of native bioactive and sensory properties of basil. For that purpose, optimal CO₂ processing conditions were established and compared to air-dried and freeze dried basil samples. The contents of bioactive compounds (polyphenols, chlorophylls, ascorbic acid) and antioxidant capacity were determined spectrophotometrically and using high performance liquid chromatography (HPLC-PDA) analysis. Color analysis and essential oil content were also determined, while consumer evaluation of sensory properties was conducted using hedonic scale preference analysis. According to the obtained results, freeze drying was recognized as the most suitable technique for preservation of color, essential oil content, bioactive compounds and antioxidant capacity of basil. The essential oil content of basil ranged from 0.21 to 0.96%, and decreased upon prolongation of CO₂ drying time. Among 4 identified phenolic acids (rosmarinic, chicoric, caftaric and caffeic), rosmarinic acid was the most abundant in all samples. Longer CO₂ drying duration (4h) also exhibited the most detrimental effect on the polyphenolic compound content and antioxidant capacity of basil. The taste and appearance of CO₂ dried basil were scored higher in comparison to air-dried basil, but further optimization of CO₂ drying is needed to improve its aroma properties. Based on the obtained results, employing shorter CO₂ drying time (2, 3h) and pressures of 80-100bar at 40°C might be a good alternative to freeze drying of basil.