Mechanical, thermal and heat sealing properties of fish skin gelatin film containing palm oil and basil essential oil with different surfactants

Abstract

Fish skin gelatin films plasticized with glycerol and incorporated with basil essential oil, palm oil or a mixture of basil essential oil/palm oil (1:1), in the presence of different surfactants (soy lecithin and Tween-20) were characterized. Films incorporated with various oils had lower tensile strength (TS) and elastic modulus (EM) with the higher elongation at break (EAB) in comparison with the control film (without oil and surfactant incorporated) (p < 0.05). TS and EM of films varied with oils and surfactants used. Films prepared with Tween-20 as surfactant showed higher EAB than those added with soy lecithin, regardless of oil types (p < 0.05). DSC analysis revealed that the incorporation of oils resulted in gelatin-based films with the decreases in both glass transition temperature (Tg) and extent of ordered-phase. All films added with different oils and surfactants had lower seal strength than the control film (p < 0.05). Film containing palm oil exhibited the higher seal strength and seal efficiency than those with basil essential oil or the mixture (p < 0.05), regardless of surfactants. Tween-20 yielded the film with the higher heat sealability than soy lecithin (p < 0.05). Good quality seal (complete fusion) was observed via SEM in control film and films containing various oils using Tween-20 as surfactant. As evidenced by FTIR, partial degradation and covalent cross-link were observed in emulsified films upon heat sealing, contributing in part to varying strengths of the seals. Therefore, both oil and surfactants could affect the mechanical properties, thermal properties as well as heat sealability of resulting films.