Characterization of composite sarcoplasmic protein films with acid- and alkaline-isolated myofibrillar protein and red water lily petal extract for edible seafood packaging

• pH-treated myofibrillar protein affected physicochemical properties of sarcoplasmic protein film. • Alkaline-treated myofibrillar protein improve flexibility of sarcoplasmic protein film. • The extract from red water lily petal improves antioxidant capacity of sarcoplasmic protein film. In this study, sarcoplasmic protein (SP) was extracted to represent its washed out to concentrate the myofibrillar protein (MP) during surimi production. Recovery of SP to produce edible film for application in seafood products would maximally utilize fish resources. Therefore, characteristics of SP film composited with myofibrillar protein isolated by either acid (MPA) or alkaline (MPB) were investigated. Composited SP film with protein isolated resulted in an increase film thickness, lightness, and moisture content, while their redness, yellowness, and solubility were reduced. The water vapor permeability of SP film was increased by MPA. The tensile strength of film was reduced by compositing with MP for 1.5 folds, while elongation was improved for 3.3 folds by that with MPB. FT-IR revealed that MP affected the secondary structure of SP film. In addition, the surface properties of film assessed by SEM revealed a smooth when MP was added regardless pH-treatment. Thermal gravitation of film was not affected by any MP. Addition of the red water lily petal extract (0.5%) enhanced the antioxidant activity of SP films composited with MP for 48.37–49.42%. When all types of films were used to wrap imitation crab sticks at 4°C for 9 days, microbial counts remained below 2 log CFU/g. Based on the TBARS assay, oxidative rancidity of samples increased upon increasing storage time, that of sample wrapped with SPAE was found as the lowest extent. In addition, the least color change also was found in this sample. Thus, SP could be used as alternative protein for producing edible film and its properties and antioxidant activity could be modified by protein isolate and natural extract from red water lily petal. Based on this study, SP film with protein isolated by acid exhibited a potential for being edible casing for surimi seafoods.