Volume 8, Issue 3 (Accepted manuscript 2026)
pbp 2026, 8(3): 0-0 |
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Tajik M. Effect of Different Drying Methods and Conditions on Phenolic Compounds, Antioxidant Activity, and Colour Characteristics of Olea europaea L. Leaves. pbp 2026; 8 (3)
URL: http://pbp.medilam.ac.ir/article-1-433-en.html
URL: http://pbp.medilam.ac.ir/article-1-433-en.html
MSc, Department of Food Science and Engineering, Da.C, Islamic Azad University, Damghan, Iran , mahshadnim@gmail.com
Abstract: (20 Views)
Objective: Olive (Olea europaea L.) leaves are a valuable source of bioactive phytochemicals, particularly oleuropein, which is largely responsible for many of their therapeutic properties. They also contain abundant phenolic compounds that contribute substantially to their antioxidant capacity. Owing to their high moisture content, freshly harvested olive leaves must be dried before phenolic compounds can be efficiently extracted and utilised. This study aimed to determine the drying method that best preserves the physicochemical properties, phenolic constituents, antioxidant activity, and colour quality of olive leaves.
Materials and Methods: Fresh olive leaves were subjected to three drying approaches. In the first treatment, samples were dried in a hot-air oven at three different temperatures. In the second, drying was performed using a fluidized-bed dryer under the same temperature conditions. The third approach involved combined drying techniques, including oven–microwave and fluidized-bed–microwave systems. The effects of drying method, drying temperature, and microwave power on total phenolic content, antioxidant activity, and colour characteristics were subsequently evaluated.
Results: Microwave-assisted drying significantly improved the retention of phenolic compounds and enhanced DPPH radical-scavenging activity compared with conventional drying methods. However, increasing either the drying temperature or microwave power resulted in significant reductions in total phenolic content and antioxidant activity. Among all treatments, samples dried at 35°C retained the highest phenolic content and exhibited the greatest DPPH radical-scavenging activity, whereas those dried at 75°C showed the lowest values. Furthermore, microwave-assisted drying consistently preserved higher levels of phenolic compounds and antioxidant activity than corresponding treatments without microwave application. Nevertheless, increasing microwave power from 360 W to 720 W caused a marked decline in both parameters.
Conclusion: The reductions in phenolic content and antioxidant activity observed at elevated drying temperatures and higher microwave powers are most likely attributable to the thermal degradation of phenolic compounds during the drying process. Similarly, the greater deterioration in leaf colour under these conditions reflects the thermal sensitivity of olive leaf pigments to excessive heat and microwave energy. Overall, microwave-assisted drying at low temperatures appears to be the most effective approach for preserving the bioactive constituents, antioxidant properties, and colour quality of olive leaves.
Materials and Methods: Fresh olive leaves were subjected to three drying approaches. In the first treatment, samples were dried in a hot-air oven at three different temperatures. In the second, drying was performed using a fluidized-bed dryer under the same temperature conditions. The third approach involved combined drying techniques, including oven–microwave and fluidized-bed–microwave systems. The effects of drying method, drying temperature, and microwave power on total phenolic content, antioxidant activity, and colour characteristics were subsequently evaluated.
Results: Microwave-assisted drying significantly improved the retention of phenolic compounds and enhanced DPPH radical-scavenging activity compared with conventional drying methods. However, increasing either the drying temperature or microwave power resulted in significant reductions in total phenolic content and antioxidant activity. Among all treatments, samples dried at 35°C retained the highest phenolic content and exhibited the greatest DPPH radical-scavenging activity, whereas those dried at 75°C showed the lowest values. Furthermore, microwave-assisted drying consistently preserved higher levels of phenolic compounds and antioxidant activity than corresponding treatments without microwave application. Nevertheless, increasing microwave power from 360 W to 720 W caused a marked decline in both parameters.
Conclusion: The reductions in phenolic content and antioxidant activity observed at elevated drying temperatures and higher microwave powers are most likely attributable to the thermal degradation of phenolic compounds during the drying process. Similarly, the greater deterioration in leaf colour under these conditions reflects the thermal sensitivity of olive leaf pigments to excessive heat and microwave energy. Overall, microwave-assisted drying at low temperatures appears to be the most effective approach for preserving the bioactive constituents, antioxidant properties, and colour quality of olive leaves.
Type of Study: Research |
Subject:
Pharmacognosy
Received: 2026/06/4 | Accepted: 2026/07/29 | Published: 2026/01/11
Received: 2026/06/4 | Accepted: 2026/07/29 | Published: 2026/01/11
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