Kaffir lime (Citrus hystrix D.C.) is a tropical plant grown in the Asian countries such as Laos, Indonesia, Malaysia, Vietnam and Thailand. The leaves are widely used as aromatic herb to add a distinctive aroma and flavor to food. Kaffir lime leaves are important ingredient in many Thai dishes such as soups and curries. In soupy dishes, whole leaves or leaves torn into smaller pieces are added, and especially, hot and sour shrimp soup (Tom Yum Kung) is the most popular of all Thai soups (Raksakantong et al., 2012).