Effect of pH and addition of corn oil on the properties of gelatin-based biopolymer films

Response surface methodology (RSM) was used to investigate pH and corn oil (CO) addition on gelatin film properties. Test films were evaluated for thickness (T), tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), water vapour permeability (WVP) and oxygen permeability (OP). T, TS and PT increased linearly (P < 0.01) with increasing CO content, but were not significantly affected by pH. pH had both linear and quadratic effects on E values (P < 0.01), while CO content had a lesser effect. WVP decreased as the pH of the film-forming solutions was adjusted away from pH 7.0 or CO addition level increased above 27.25%. OP was affected in both a quadratic and linear manner by pH adjustment and CO addition, respectively. Optimal film-forming conditions were pH (10.54) and CO level (55.18%, w/w), as predicted by response surface methodology. Scanning electron microscopy (SEM) was performed to investigate the microstructures of gelatin films, and confocal scanning laser microscopy (CSLM) was used to investigate fat distributions and protein phase in gelatin films.