Impact of melting point of palm oil on mechanical and water barrier properties of gelatin-palm oil emulsion film

• Melting point shows strong effect on properties of gelatin-palm oil emulsion film.
• The influence is mainly related with size and phase state and of palm oil droplets.
• A satisfied performance of emulsion film can be achieved with optimization of oil degree.

In order to explore the effects of oil's melting points on film performance, a gelatin emulsion film with different degrees (8°, 18°, 24°, 33° and 44°, referring to different melting points) of commercial palm oils were fabricated and its properties were investigated. A variety of size distribution (d4,3 and d3,2) of oil droplets in film-forming emulsion was observed, with 24° oil being the smallest and most regular. As expected, the addition of palm oil obviously decreased film strength but increased elongation, depending upon oil degree. Among them, more importantly, strength of the film containing 24° palm oil was close to that of the pure gelatin film, coexisting with a satisfied elongation value. Furthermore, reducing water vapor permeability was observed in all emulsion films, wherein film containing 24° oil was lowest. Increasing degrees of palm oil led to an increase in film's opacity and a variation of film color, as well as thermal stability. The aforementioned different effects were consistent with microstructure of the emulsion films, where the film with 24° oil droplets was smoother and compact. In conclusion, the melting point of palm oil had a remarkable influence on properties of the resulting emulsion film, mainly being attributed to the differences in size and related state of oil droplets in emulsion during film processing.

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