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.