Effect of drying method on oleuropein, total phenolic content, flavonoid content, and antioxidant activity of olive (Olea europaea) leaf. Issue 5 (13th February 2018)

• Record Type: Journal Article
• Authors: Şahin, Selin; Elhussein, Elaf; Bilgin, Mehmet; Lorenzo, Jose M.; Barba, Francisco J.; Roohinejad, Shahin
• Is Part Of: Journal of food processing and preservation. Volume 42:Issue 5(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-02-13
• Subjects: Food -- Preservation -- Periodicals; Food industry and trade -- Periodicals; 664.005
• DOI: 10.1111/jfpp.13604
• Languages: English
• ISSNs: 0145-8892

Abstract

Abstract: The purpose of this research was to study the effect of microwave drying (MD) on the major phenolic compound oleuropein, total phenolic and flavonoid contents, and antioxidant activity of the olive leaves. The results were compared to those obtained after using freeze drying (FD), vacuum drying (VD), oven drying (OD), and ambient air‐drying (AAD). Response surface methodology, using a central composite face‐centerd design, was used to optimize the effects of microwave irradiation power (300–500 W), solid mass (1.5–2.5 g), and drying time (4–6 min) on oleuropein and other olive leaves antioxidant compounds. The second‐order models were found highly adequate with very low root mean squared deviation ( RMSD ) and high coeffecient of determination ( R 2 ) values. The results of MD under optimum conditions (2.085 g sample at 459.257 W for 6 min of drying period) has demonstrated to be the best drying method followed by FD, VD, OD, and AAD. Practical applications: Olive leaves are agricultural waste which contains significant amounts of valuable compounds such as oleuropein and phenolic compounds. Nowadays, application of these compounds has attracted considerable interest as food additives and/or nutraceuticals in both food and pharmaceutical industries. Several methods have been applied for the extraction of phenolic compounds from olive leaves and by‐products. However, to obtain higher extraction yield, it is important to reduce the water content of the samples before extraction. This study demonstrates the feasibility of using microwave drying as a promising technique compared to other methods (e.g., freeze‐, vacuum‐, oven‐, and ambient air‐drying) for drying of olive leaves with minimum changes in total phenolic, flavonoids, antioxidant activity, and oleuropein contents.