Effect of drying techniques and operating conditions on the retention of color, phenolics, and antioxidant properties in dried lemon scented tea tree (Leptospermum petersonii) leaves

Leptospermum petersonii is an aromatic native Australian plant that has been traditionally used as a medicine and a tea; however, its application in food products is increasing. The aim of this study was to investigate the most suitable and energy-efficient drying conditions to retain phenolic compounds, antioxidant properties, and, color in dried Leptospermum petersonii leaves. In this study, six drying techniques were investigated including hot air, vacuum, microwave, freeze, sun, and shade. Results showed that freeze-drying retained maximum color, phenolic compounds, and, antioxidant capacity, however, it consumed the most time and energy. Conversely, microwave drying (960 W, 0.1 hr) used the least amount of time and energy yet retained the second-highest levels of phenolics and antioxidant capacity. In conclusion, microwave drying is suggested for large-scale drying. This method is economical and it is approximately 480 times and 1,700 times more time and energy efficient compared to freeze-drying. Novelty impact statement Microwave and freeze-drying is the most and least energy efficient method respectively There is a strong correlation between phytochemical and antioxidant capacity Freeze-drying retains maximum color properties, phenolic compounds, and antioxidant capacity

Automated summary

In this study, different drying methods for Leptospermum petersonii leaves were investigated. Results showed that microwave drying was the most energy-efficient method with good retention of phenolics and antioxidant capacity, while freeze-drying retained the most color properties, phenolic compounds, and antioxidant capacity but consumed more time and energy.