Purpose -This paper is aimed at food science or biology students planning a practical independent study into the antimicrobial properties of spices and academic staff wishing to develop a straightforward and reproducible practical activity. Design/methodology/approach -Disc-diffusion assays are used to investigate the antimicrobial activity of cinnamon and cloves against two bacteria Escherichia coli B and staphylococcus albus and a yeast Saccharomyces cerevisiae. Aqueous and alcoholic extracts of the spices and alcoholic extracts of their essential oils are examined. Minimum inhibitory concentrations of alcoholic extracts of both spices and oils are also determined. Findings -Both spices demonstrated microbial inhibitory effects; alcoholic extracts had greater activity than aqueous extracts. Additionally, essential oils had greater activity than the spices. Minimum inhibitory concentrations were smaller with the oils than with the spices. Research limitations/implications -Although the research for this paper involved just two spices, such is the size of the plant kingdom that there are wide opportunities for further investigations using this procedure. Practical implications -Disc-assays were found to be a simple, cheap and reproducible practical method. For this paper, micro-organisms available for educational purposes were used; however, other organisms could be investigated depending upon available microbiological expertise and facilities. Originality/value -The results demonstrate that the antimicrobial effects of spices and particularly their essential oils can be examined using disc-diffusion assay. The method provides many opportunities for student investigation.

PurposeThe purpose of this paper is to provide food science or biology students with a simple and reliable method of determining the antibacterial activity of a range of foods and biological materials that contain lysozyme.Design/methodology/approachThe antibacterial effects of the materials reported to contain lysozyme were assayed by gel‐diffusion using the lysozyme‐sensitive bacterium Micrococcus lysodeikticus. The antibacterial effects of the selected test materials, namely fresh hen egg‐white, human saliva, Brussels sprouts, papaya and figs were compared against standard solutions of proprietary analytical crystalline hen egg‐white lysozyme.FindingsThe antibacterial activity of the test substances was similar to the effects of their lysozyme concentrations as quoted by other workers.Research limitations/implicationsAntibacterial activity was higher in avian egg‐white and human saliva than in the assayed plant material. Measurement of the activity in the plant material was at the limits of the sensitivity of the method.Practical implicationsThe two main practical methods for measuring lysozyme are either a gel‐diffusion assay or a spectrophotometric procedure. Gel‐diffusion assay provides a convenient procedure for student investigative work as it has a limited requirement for method development. Additionally, it is simple, cheap, reproducible and does not require specialist equipment. Further possible investigations for students are suggested.Originality/valueThe paper builds on established techniques to provide a procedure that is appropriate for student use for determining lysozyme activity in a variety of biological materials.