Abstract:
The aim of this research was to develop an antibacterial product from betel nut extracts. The bacteria of interest was food poisoning bacteria including Bacillus cereus ATCC 1729, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Salmonella Typhimurium ATCC 13811. The effects shape and age of betel nut as well as solvent used for extraction (water, 95% ethanol, acetone and ethyl acetate) on % yield and antibacterial activity were determined. The water extract of ripe oblong-shape nut and 95% ethanol extract of ripe round-shape nut had % yield of 15.01±4.59 and 27.11±9.18, respectively. Their Minimum Inhibitory Concentration (MIC) was 7.81 x 10-1 mg/ml for B. cereus, S. aureus, and E. coli and 1.56 mg/ml for S. Typhimurium. All acetone extracts had MIC of 7.81 x 10-1 mg/ml for all bacteria used in this study. However, its water solubility was low and it did not dissolve in soybean oil. Therefore, the mixture of water extract of ripe oblong-shape nut and 95% ethanol extract of ripe round-shape nut was selected to be active ingredient in the product. To enhance the antibacterial activity of the product, essential oils from basil, peppermint, lemon and orange were tested for their antibacterial activity, and then selected to be used as an active ingredient in the product. Peppermint oil was selected as it gave the largest clear zone of diameter of 10.00±0.00, 17.00±2.65, 15.33±4.16 and 17.33±3.06 mm. for B. cereus, S. aureus, E. coli and S. Typhimurium, respectively. The MICs of peppermint oil in water emulsion having Tween 20 (1 %wt) as emulsifier were 56, 56, 56 and 225 mg/ml for B. cereus E. coli S. Typhimurium and S. aureus, respectively. Products were prepared by mixing 5.60 %wt peppermint oil into water or aqueous solution of the betel nut extract mixture (0.15 %wt of water extract of ripe oval-shape nut and 0.15 %wt of 95% ethanol extract of young round-shape nut) using Tween 20 (15-30 %wt) as emulsifier. The mixtures were ultrasonicated at 300 watt and 20 kHz for 30 min. Samples containing > 20 %wt Tween 20 were clear solution and stable against phase separation. After 1 day, phase separation was observed for samples containing 20 %wt Tween 20. However, upon remixing with ultrasonication for 15 min after 7 day storage, they became clear solution and stable against phase separation. The average diameter of oil particles in these products was 0.068±0.007 and 0.136±0.074 µm in the presence and in the absence of the betel nut extract mixture, respectively. The range of oil particle size was 6.503x10-3-5.56 x10-1 and 7.531x10-3-1.990 µm, respectively. The Minimum Bactericidal Concentration (MBC) of these products was 60, 30 and 30 µl/ml for B. cereus, E. coli and
S. Typhimurium, respectively. At 500 µl/ml, they could inhibit growth of S. aureus.