Electrochemical and Optical Microbiological Testing: a Comparative Study on Properties of Essential Oils

Abstract

Introduction. The national economy is currently developing a system for monitoring the quality and safety of goods. Food products, ingredients, and additives possess various pro- and antibiotic properties. Therefore, available express methods of quantitative assessment of microbiological contamination are a relevant aspect of domestic food industry. Study objects and methods. The study featured ten essential oils of plant origin that can be used as functional additives to various food products. Results and its discussion. The research introduced a new biotesting technique for repetitive recording of changes in the intensity of elastic light dispersion. The technique made it possible to measure pH and electrical conductivity of a liquid nutrient medium incubated in the presence and absence of viable test microorganisms and test samples. The paper describes the results of this technique applied to a comparative analysis of antibiotic activity of various essential oils in different concentrations. As the concentrations of the test extracts decreased, their antibiotic activity monotonically also went down, while the probiotic activity increased. The shortterm biological activity of test samples appeared to be significantly higher than their long-term activity. The medium-term biological activity of the test samples was mostly intermediate in value. Only rarely did it exceed both the long- and short-term biological activity of the same TE. The essential oils obtained from the leaves of Thuja occidentalis, Eucalyptus globulus, and Cupressus sempervirens exhibited the most active and long antibiotic properties. Conclusion. The biological activity of food products, including various plant extracts, depends not only on the raw material and the extraction method, but also on the concentration of the extract in the product. As a rule, the exact nature of these dependencies can only be established empirically and requires a set of various tests. The present article introduces a new highly objective and informative express methodology that simplifies this process. The technique is less labor-, time-, and material-consuming than standard visual microbiological methods. It can be used to assess the effect of test samples on the vital activity of microorganisms in various foods, ingredients, and additives.