Effect of convective solar drying on colour, total phenols and radical scavenging activity of olive leaves (Olea europaea L.)

Abstract

In this study, olive leaves, which are known for their therapeutic and antioxidant properties, were used to assess the effect of solar drying conditions (temperature and flow rate) on the drying time and quality parameters of olive leaves. Samples were dried at three drying temperatures (40, 50 and 60°C) and at two drying air flow rates (1.62 and 3.3 m 3 min )1 ) in a convective laboratory solar dryer. From the experimental results, it was noted that the drying time required to reduce the moisture content to 0.10 kg kg )1 d.b. depends mainly on the drying temperature. The quality attributes of the dehydrated olive leaf samples were investigated in term of colour, total phenols and radical scavenging activity. The effect of solar drying on L*, a* b* parameters was significant (P < 0.05) for all the studied olive leaves. Besides, the total phenols of olive leaves were significantly (P < 0.05) influenced by drying air conditions and tended to decrease with increased drying time. The DPPH radical scavenging activity was higher in fresh [EC 50 39.40 (ZR)-39.95 (CH)] than in dried leaves. However, the radical scavenging activity was also high in leaves dried at 60°C, 3.3 m 3 min )1 [EC 50 54.21 (ZR)-68.79 (CL)].

Effect of Convective and Vacuum–Microwave Drying on the Bioactive Compounds, Color, and Antioxidant Capacity of Sour Cherries

“…A more attractive color was obtained and higher anthocyanins content was ensured when a lower power was used for final drying. The value of coordinate a* decreased compared to the fresh samples and denoted a more red chroma, which is indicative of the browning reaction (Bahloul et al 2009). Consumers prefer visible quality, i.e., the color of the product; therefore, ΔE values can be very important for the dried product, which expresses the human eye's ability to discriminate between colors of a sample.…”

A Review on Solar Drying of Agricultural Produce

“…Solar radiation causes all natural cycles and activities such as rain, wind, ocean currents, photosynthesis and several other phenomena which are crucial for life. The entire world energy need has been based from the very beginning on solar energy [7][8][9]. All fossil fuels (coal, gas, oil) are converted form of solar energy.…”

“…Bahloul et al [7] Coffee Solar dryer with black transpired air solar collector -Coffee beans dried faster in the solar dryer with acceptable quality and no serious defects.…”

Instant controlled pressure drop texturing for intensifying ethanol solvent extraction of olive (Olea europaea) leaf polyphenols

“…Olive leaf is well known as rich in antioxidant compounds [1,2], and has been used as a folk medicine against fever and malaria [3,4]. Moreover, its extracts widely have beneficiated from numerous research works [2,5]. Olive leaves extracts have shown hypotensive, hypoglycemic, antimicrobial and antioxidant activities [3,6].…”