Mechanical, surface, and thermal properties of gelatin-collagen blend films with potential application to biodegradable packaging

Abstract

Gelatin and collagen are natural protein-based biopolymers with promising properties for biodegradable food packaging. This study presents the development and characterization of films composed of pure gelatin (G:C 100:0), pure collagen (G:C 0:100), and a gelatin-collagen blend (G:C 80:20). We evaluated their physicochemical, mechanical, surface, and thermal properties, including moisture content, Hydroxyproline [Hyp] content, thickness, color parameters, water contact angle (WCA), tensile properties, and thermal behavior using differential scanning calorimetry (DSC). The blend films exhibited 10% higher moisture content and 35% greater water absorption capacity compared to pure gelatin films. The inclusion of collagen increased yellowness (b*) without significantly affecting total color difference (∆E). All films showed partial wetting behavior pointed by a negative spreading factor (S) and a limited water contact angle (75° < WCA < 96°), with blend films presenting surface properties more similar to collagen films. Mechanical testing indicated a > 50% increase in toughness for the blend films, along with enhancements in tensile strength and elongation at break. Thermal analysis confirmed good thermal stability, with a melting point of 72°C and a glass transition at 150°C. These findings suggest that gelatin-collagen blend films could offer promising functional properties for sustainable food packaging. Future studies should evaluate their performance in contact with meat products during storage conditions.