2. Materials and methods
2.1. Fish skin preparation
Whole fresh farmed striped catfish (P. hypophthalmus) (approximately 2 years old) weighing 1 ± 0.5 kg/fish stored on ice were procured from the fish market of Hat Yai, Songhkla, Thailand. Fish were stored in ice with a fish/ice ratio of 1:2 (w/w) and transported within 1 h to the Department of Food Technology, Prince of Songkla University, Hat Yai, Thailand. Upon arrival, fish were washed using tap water and deskinned. The skin was washed with cold water (5–8 C) and cut into small pieces (0.5 0.5 cm2). The prepared skin samples were packed in polyethylene bags and kept at 20 C until