Investigation of the physico-chemical and antimicrobial properties of propolis extract as a natural food preservative

As a natural bioproduct obtained from beekeeping, propolis with its antimicrobial and antioxidative properties can be used in food production. The purpose of this study is to evaluate the application of propolis as a preservative in food. After preparation of propolis, the physicochemical properties of raw propolis and extract were evaluated with three repetitions. the results showed that amount of waxes, moisture, fat, protein, ash and pH of raw propolis were 35.10±0.89%, 4.2±0.14%, 64.78± 0.22%, 2.30± 0.13%, 1.25± 0.25%, 4.89 ± 0.06 respectively. Obtained results of propolis extract analysis indicated that antioxidant activity, turbidity, pH, brix, total phenolic and flavonoids content of the prepared propolis ethanolic extract were 94.5±0.02%, 1.091±0.03%a.u., 5.9±0/12 and 18.5±0.07 Bx°, 91.12±0.09 mg/g (gallic acid) and 87.94±0.03 mg/g (quercetin), respectively. The extracted propolis extract was evaluated by Gas chromatography / mass spectrometry to identify chemical compounds. The results showed that the main constituents of propolis extract were included Pinostrobinchalcone (22.90%), Pinocembrin (6.14%), 2,1,3-Benzothiadiazole (5.76%), Tectochrycin (4.83%), Phenethylalcohol (4.25%), Oleic acid (3.10%). Evaluation of antimicrobial activity of propolis extract showed that the prepared extract had high antibacterial activity against Staphylococcus aureus while it was ineffective on Escherichia coli. The extract also inhibited the growth of Aspergillus fluvus fungus, unlike the control sample, so that its mycelia diameter was reached 7 mm after 8 days incubation. In general, the results showed that the produced propolis extract can be used as an effective natural preservative in foods.