Comparison Of Antimicrobial Activities Of Clove Oil & Its Extract On Some Food Borne Microbes

摘要

A study was carried out in the comparative analysis of ethanolic extract (50%) of clove & clove oil as natural antimicrobial agents on some food spoilage bacteria. The antibacterial activity of clove oil & its extract (50% ethanol) was tested against ten bacteria (seven Gram positive & three Gram negative) & seven fungi by agar well diffusion assays. The clove oil was found to be better antagonistic agent as compared to its extract counterpart by inhibiting both bacteria & fungi. The oil was found to be very effective with a lowest minimum inhibitory concentration (MIC) of 2.5% (v/v) against Staphylococcus epidermidis & Staphylococcus sp. Amongst the fungi, Aspergillus niger was found to be highly sensitive to the oil. Sodium propionate (standard food preservative) was used as a positive control. Clove oil was found to be more effective as compared to both clove extract & sodium propionate. This study shows the potential of clove oil to be used as food bio-preservative. Introduction The increase of food borne infections has resulted from the consumption of food contaminated with bacteria and/or their toxins. This has initiated considerable research interest towards the discovery of potent antimicrobial agents. Today the issue of food preservation has become more complex, with increasing concern over the presence of chemical residue in foods and the demand for non-toxic natural preservatives is increasing everyday because of harmful effects of food preservatives. The recent negative consumer perception against artificial preservatives, however, has shifted the research effort towards the development of alternatives that consumers perceive as naturals (Shelef, 1984). Antimicrobial properties of herbs and spices have been recognized and used since ancient times for food preservation as well as in medicinal use (Zaika, 1988; Conner, 1993; Dorman, 2000). A renewed interest in ‘natural preservation’ appears to be stimulated by present food safety concerns, growing problems with microbial resistance and rise in the production of minimal processed food joined with ‘green’ image policies of food industries.Cloves (Syzygium aromaticum, syn. Eugenia aromaticum or Eugenia caryophyllata) are the aromatic dried flower buds of a tree in the family Myrtaceae (Srivastava & Malhotra, 1991; Chaieb et al., 2007a). Cloves are used in Ayurveda, Chinese medicine and Western herbalism. Cloves are used as a carminative, to increase hydrochloric acid in the stomach and to improve peristalsis (Phyllis & James, 2000). It is also used in dentistry where the essential oil of clove is used for dental emergencies (Cai & Wu, 1996; Prashar et al., 2006). In addition, the cloves are anti-mutagenic (Miyazawa & Hisama, 2003), anti-inflammatory (Kim et al., 1998), antioxidant (Chaieb et al., 2007b), anti-ulcerogenic (Bae et al., 1998; Li et al., 2005), anti-thrombotic (Srivastava & Malhotra, 1991) and anti-parasitic (Yang et al., 2003).The chief significance of the above study was to carry out the comparative analysis of the antimicrobial activities of clove oil & extract as an alternative to chemical preservatives for improving the shelf life of food products. Materials And Methods Materials: All chemicals used were of analytical-reagent grade and obtained from E. Merck (Mumbai, India). Readymade clove oil & clove buds (Syzygium aromaticum) were purchased from local market of Meerut (Uttar Pradesh, India). Dr. C.M Govil, Professor, Botany Department, C.C.S University, Meerut, India confirmed the species.Bacterial and fungal test isolates: Ten bacterial isolates (seven Gram-positive and three Gram-negative), mostly food-borne pathogens, were selected for this study. The Gram-positive bacteria comprised Bacillus cereus, Bacillus subtilis, Bacillus sp., Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes and Micrococcus luteus, while the Gram-negative bacteria comprised Escherichia coli, Klebsiella sp. and Pseudomonas aeruginosa. The fungal iso