Physical Properties of Egg White−Dialdehyde Starch Films

Abstract

Films were cast from heated (40 °C for 20 min) alkaline (pH 11.25) aqueous solutions of egg white (EW) solids (9 g/100 mL of water), polyethylene glycol 400 (60% w/w of EW), yolk solids (10% w/w of EW), and dialdehyde starch (DAS) at 0, 2.5, 5, 7.5, or 10% (w/w) of EW. For all types of films, tensile strength (TS), percentage elongation at break ( E ), Hunter color values ( L, a, and b ), total soluble matter (TSM) after immersion in water at 25 °C for 24 h, and protein solubility (PS) after immersion for 12 h in buffers (pH 8) containing urea and urea/2-mercaptoethanol were determined. DAS addition increased ( P < 0.05) film TS and yellowness (+ b values) and reduced ( P < 0.05) film TSM and PS in both buffer systems. These modifications in film properties suggested occurrence of cross-linking between EW protein and DAS. This was further supported by SDS−PAGE patterns. Such patterns for DAS-containing films revealed bands of aggregates, increasing in intensity with increasing amounts of DAS, which were absent from patterns of control EW films. Keywords: Egg albumen; protein films; dialdehyde starch; cross-linking