Effects of Drying on Polyphenol Oxidase and Antioxidant Activity of Morus alba Leaves. Issue 6 (2nd July 2015)

• Record Type: Journal Article
• Authors: Tan, Janet Jia Yin; Lim, Yau Yan; Siow, Lee Fong; Tan, Joash Ban Lee
• Is Part Of: Journal of food processing and preservation. Volume 39:Issue 6(2015:Dec.)
• Page Start: 2811
• Page End: 2819
• Publication Date: 2015-07-02
• Subjects: Food -- Preservation -- Periodicals; Food industry and trade -- Periodicals; 664.005
• DOI: 10.1111/jfpp.12532
• Languages: English
• ISSNs: 0145-8892

Abstract

Abstract: The effects of oven‐drying at 50 and 100C, sun‐drying and ambient air‐drying at 24 ± 1C on the antioxidant properties (AOPs) of mulberry ( M orus alba L.) leaves were studied. Except for leaves oven‐dried at 50C which showed minimal AOP changes, leaves dried under other conditions resulted in a significant decrease in AOP. Fresh mulberry leaves contained low oxidative enzyme activities (polyphenol oxidase [PPO]: 1.40 ± 0.58 ΔA435 /min/g of fresh leaves and peroxidase: 1.59 ± 0.42 ΔA418 /min/g of fresh leaves) which were reduced to nonmeasureable or lower values when they were dried at 50, 100C and blanched in boiling water. The major factor causing AOP decrease in thermally treated leaves (oven‐drying at 100C and sun‐drying) was due to thermal degradation but the decrease in AOP for ambient air‐dried leaves was associated with the presence of PPO. Overall, oven‐drying at 50C was the most preferred drying method. Practical Applications: Mulberry with excellent free radical scavenging, antioxidant, anticancer and anti‐hyperglycemic properties has long been used as traditional medicine and health food product. Generally, mulberry leaves are processed and consumed as tea. Drying, which helps preserve the nutrient contents of mulberry leaves, is an important method in mulberry tea processing. In order to exploit mulberry leaves more scientifically and efficiently for commercial purpose, the present study serves as an important work in providing insights into how oxidative enzymes and thermal stability of antioxidants in mulberry leaves affect the antioxidant properties when subjected to different drying conditions. The optimum drying condition found in this study will be beneficial to the tea processing industry.