Abstract:
The objective for this research was to study the use of propolis in Thailand for improvement of antioxidant and antimicrobial properties of chitosan film. Firstly, the propolis extract was prepared by using solvent with different water to ethanol ratios including 70:30, 60:40, 50:50, 40:60 and 30:70. The total phenolic content using Folin-Ciocalteau method, the phenolic compound using high performance liquid chromatography (HPLC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the ability to inhibit Staphylococcus aureus (TISTR 118), Salmonella enteritidis (DMST 17368), Escherichia coli (TISTR 780) and Pseudomonas aeruginosa (ATCC 27853) using agar diffusion technique were determined in order to selected the optimum extraction condition. The results showed that the total phenolic contents were in the range of 5.56-41.00 mg gallic acid equivalent/g. The total phenolic contents, rutin, quercetin and DPPH increased with increasing ethanol concentration in the solvent. It was also found that the extract using 70 :30 solvent was able to inhibit S. aureus whereas those using 40:60 and 30:70 were ineffective. Therefore, the water to ethanol ratio of 70:30 was the optimum solvent and was used for further experiment. Secondly, the effect of adding propolis extract with different concentrations 0.5, 1.5, 2.5, 5 and 10% (w/v) to the chitosan film was determined by measuring the physical properties including surface colour (∆E), transparency (%T), water vapor permeability (WVP), oxygen gas transmission rate (OTR), tensile strength (TS), elongation at break (%E), chemical property including TPC, phenolic compound and DPPH radical scavenging activity. The interaction of functional group in the chitosan film containing propolis extract and glass transition temperature (Tg) were also determined using the Fourier Transform Infrared Spectrometer (FT-IR) and Differential Scanning Calorimeter (DSC), respectively. The results showed that ∆E, TS, %E, total phenolic contents and DPPH radical scavenging of the film increased, while %T and WVP, OTR decreased with increasing concentration of the propolis. Rutin was found in all samples. The FT-IR spectra indicated that there was hydrogen bond between functional groups of chitosan and phenolic compounds of propolis. It was also found that adding propolis extract affected the Tg of the of chitosan film, resulting changes in physical properties of the films. The antimicrobial property of all film samples indicated there was no inhibition zone of all 4 bacteria tested. However, there was no bacterial growth under the contact surface of the chitosan film containing propolis extract.