Effect of pH on the preparation of edible films based on fish myofibrillar proteins

Transparent and flexible edible/biodegradable films were successfully made from myofibrillar proteins of blue marlin meat. The effect of pH of film-forming solutions on film formation, tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP), light transmission, transparency, film solubility, protein solubility and enzymatic hydrolysis was investigated. Myofibrillar protein-based films were formed within pH 2-3 and 7-12, whereas films were not formed between pH 4 and 6 because of the poor protein dispersion around the isoelectric point. TS of the films was higher when prepared at the acidic (pH 2, 3) and alkaline (pH 11, 12) conditions, whereas EAB was almost constant irrespective of pH. On the whole, the pH of film-forming solutions had no effect on WVP, light transmission, film solubility and enzymatic hydrolysis. WVP of myofibrillar protein films were slightly lower than those of other protein-based edible films and higher by one to three orders of magnitude than those of synthetic films. The films prepared at lower or higher pH, which had a more stable protein network, possessed superior transparency close to synthetic films.