Valorization of egg-white byproducts into biodegradable hydrogels: Processing optimization and functional properties

The growing accumulation of inedible abnormal eggs and environmental concerns regarding petroleum-based superabsorbent polymers (SAPs) in food packaging underscore the need for sustainable, food-derived alternatives. In this study, biodegradable egg-white hydrogels were developed through controlled acylation and crosslinking to enhance absorbency and structural stability. Processing optimization of lyophilization, heating, and grinding reduced production time from 4 to 1.5 days and significantly improved water uptake (p < 0.05). Among protein concentrations tested, a 4% (w/w) egg-white solution achieved the optimal balance between gel stability and water uptake, exhibiting significantly higher swelling capacity than lower or higher concentrations (p < 0.05). Chemical modification using succinic anhydride (SA) or ethylenediaminetetraacetic dianhydride (EDTAD), combined with glycerol (G) or N,N'-methylenebisacrylamide (MBA), produced five hydrogel formulations. Although SG (SA + G) and EG (EDTAD + G) showed lower initial swelling capacity than EM (EDTAD + MBA), both SG and EG exhibited significantly higher water-holding and reswelling capacities compared with EM (p < 0.05). Rheological analysis indicated that SG possessed the highest storage modulus (G') and lowest tan δ, characteristic of a predominantly elastic network, whereas EG displayed increased viscosity and plasticity due to enhanced hydrophilicity. In contrast, MBA-crosslinked hydrogels showed weaker network formation and limited swelling performance. Soil burial tests demonstrated that SG and EG hydrogels degraded more rapidly than commercial water beads and promoted greater microbial growth within 7 days (p < 0.05). Overall, controlled chemical modification of egg-white proteins enables the production of sustainable, biodegradable hydrogels as promising alternatives to petroleum-based absorbent materials.