Comparison Study on Antimicrobial Activity and Antimicrobial Agent Release of Virgin Coconut Oil (VCO) and Lauric Acid Modified Pullulan/Starch Based Films
Antimicrobial (AM) packaging is a type of packaging that can reduce or inhibit the growth of spoilage microorganisms by the release of AM agent to the packaged food, and thus extending the shelf life of food. Virgin coconut oil (VCO) is one of the AM agent, which is easily available in Malaysia and having potential to be applied in food packaging due to its AM, antiviral and antifungal properties. The AM property of VCO majorly contributed by its free fatty acids and their monoglycerides, especially lauric acid and monolaurin. Thus, the aim of this study is to evaluate the AM activity of VCO and lauric acid as AM agent. The VCO and lauric acid modified pullulan/starch-based films were prepared by casting technique. The AM activity of VCO and lauric acid against Escherichia coli (E.coli) were tested by agar diffusion test. The inhibition zone was observed on disks containing lauric acid modified pullulan/starch-based film solution only. It indicates that only lauric acid had inhibitory effect on E.coli. Lauric acid modified pullulan/starch-based film at 9:1 ratio had the highest inhibition zone diameter (1.7 mm) due to the presence of the highest concentration of lauric acid, which was 3.6 mg/mL. The release of AM agent from modified pullulan/starch-based film was evaluated by liquid culture test. The result showed that lauric acid modified pullulan/starch-based film had longer AM agent release period than VCO, particularly at 9:1 ratio. It had the longest duration of AM agent release which was 13 hours. Consequently, lauric acid is able to inhibit the growth of bacteria for a longer time than VCO. It can be concluded that lauric acid is more effective as AM agent compared to VCO. Additionally, lauric acid modified pullulan/starch-based film at 9:1 ratio is the most effective formulation for the AM film.