Effect of emulsifier on properties and microstructures of surimi protein/palm oil composite film

Effect of different types and concentrations of emulsifier on properties of surimi protein/palm oil composite film was investigated. Different emulsifiers including Hexadecylpyridinium Chloride Monohydrate (HCM), Tween-20, Tween-80 and Span-60 at various concentrations (5, 10 and 15% of palm oil) were incorporated in film from bigeye snapper surimi protein added with palm oil at 75% glycerol substitution. The composite films had decreased Water-Vapor Permeability (WVP), Young's modulus (EM), Tensile Strength (TS) and transparency but increased Elongation at Break (EAB) and yellowness (b*-value) as compared to the control surimi protein film (p<0.05), irrespective of emulsifier type and concentration. Increasing concentration of water-soluble emulsifiers (i.e., HCM, Tween-20 and Tween-80) resulted in increased EM and decreased WVP of the films. However, the concentration of oil-soluble emulsifier (i.e., Span-60) had no impact on mechanical properties and WVP of the composite films. At the same level used, films added with different types ofwatersoluble emulsifiers exhibited similar EM and TS (p>0.05). In general, mechanical properties as well as transparency of the composite films stabilized with oil-soluble emulsifier (Span-60) were poorer than those added with water-soluble emulsifiers. From the results, composite films added with Tween-20 at 10% generally had the highest mechanical properties, especially the EAB and water-vapor barrier property (p<0.05). The improved properties of composite film were related with the increased uniform dispersion of oil droplets in the matrix of film as evidenced by SEM morphologies, depending on types and concentrations of emulsifiers used. Therefore, emulsifier types and levels had an influence on properties of surimi protein/palm oil composite film which were governed by different microstructures during film formation.