Science Letters

Food Sciences | Research article

Impact of Drying Methods on the Functional Properties of Peppermint (Mentha piperita L.) Leaves

Khizar Hayat*

Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, PO Box 2460, 11451, Riyadh, Saudi Arabia

Abstract

The microbes and enzymes responsible for the degradation of food materials are only active in the presence of suitable water content. Therefore, drying is a commonly used method to prolong the shelf life of food materials, especially herbs and spices. In this study, the effect of conventional hot-air oven drying and microwave oven drying was evaluated on the weight loss, total polyphenol content (TPC), total flavonoid content (TFC), antioxidant activity and reducing power of peppermint leaves. The maximum weight loss (87.1%) was found in peppermint leaves dried at 80°C for 180 min in the hot-air oven followed by the sample dried in the microwave oven at 900W for 3 min. Microwave oven drying at 900W yielded the highest TPC [406.7 mg GAE/100 g fresh weight (FW)] in peppermint leaves. While the lowest TPC (183.5 mg GAE/100 g FW) was found in the leaf sample dried in the hot-air oven at 80°C and it was even lower than that of the fresh leaf sample (229 mg GAE/100 g FW). Microwave oven drying at 900W showed the highest TFC (247 mg CE/100 g FW) of peppermint leaves followed by the hot-air oven drying at 50°C (181 mg CE/100 g FW). The least DPPH scavenging capacity (34%) was exhibited by the samples dried in the hot-air oven at 80°C followed by the fresh leaf sample (39.9%). While the highest DPPH scavenging capacity (86.8%) was obtained for the peppermint leaves dried in the microwave oven at 900W. In the present study, microwave drying yielded better results in a shorter time. Thus, the microwave drying could be a promising technique to enhance the shelf life and functional properties of peppermint leaves.