This study explores the development of smart packaging materials using whey protein isolate (WPI) and chitin nanofiber (CNF) as matrices to monitor fish freshness. The natural anthocyanin from red poppy (RPAs) is incorporated into these matrices to serve as a color-sensing agent. The research aims to enhance the packaging's barrier properties, mechanical strength, and sensitivity to pH changes, which are crucial for real-time monitoring of food spoilage. The WPI/CNF/RPAs indicator showed significant improvements in flexibility, strength, and water vapor permeability compared to the control. It also exhibited high sensitivity to acid, base, and ammonia. Colorimetric tests demonstrated that the indicator changed color from brownish-yellow to gray at 4°C, indicating fish spoilage. The study highlights the potential of pH-sensitive intelligent indicators for real-time monitoring of fish freshness before consumption, contributing to food safety and quality.This study explores the development of smart packaging materials using whey protein isolate (WPI) and chitin nanofiber (CNF) as matrices to monitor fish freshness. The natural anthocyanin from red poppy (RPAs) is incorporated into these matrices to serve as a color-sensing agent. The research aims to enhance the packaging's barrier properties, mechanical strength, and sensitivity to pH changes, which are crucial for real-time monitoring of food spoilage. The WPI/CNF/RPAs indicator showed significant improvements in flexibility, strength, and water vapor permeability compared to the control. It also exhibited high sensitivity to acid, base, and ammonia. Colorimetric tests demonstrated that the indicator changed color from brownish-yellow to gray at 4°C, indicating fish spoilage. The study highlights the potential of pH-sensitive intelligent indicators for real-time monitoring of fish freshness before consumption, contributing to food safety and quality.