The estimation of the possibility of using horseradish (Armoracia rusticana) when preserving the fern

The aim of the research was to evaluate the possibility of using horseradish (Armoracia rusticana) as an antimicrobial agent to increase the shelf life of ferns preserved by the method of pickling. In model experiments, halophilic archaea cultures causing spoilage of salted ferns was used, previously isolated by the authors. The cultures were grown aerobically in liquid nutrient medium under the optimum temperature with the addition of crushed root or crushed horseradish leaves. Starting titer of the cultures before the addition of horseradish was equal to 2 · 107 cells /ml, which was 10 times higher than the maximum recorded number of the indicated halophilic archaea in the salted fern. The cultures of the same archaea without adding horseradish were used as the control. It was found that both the leaves and the root of horseradish had reduced the number of halophilic archaea. Depending on the organs of horseradish used as an antimicrobial additive, and on the applied dose, the population of archaea was reduced by 45-93 %. Antimicrobial effect was temporary. After initial decline in the numbers, the archaea population returned to exponential growth due to surviving cells. Additional experiments showed that the resumption of growth had not been associated with the adaptation of archaea to the antimicrobial substances of horseradish, but with the disappearance of these substances in the nutrient medium. Horseradish leaves had a significantly higher antimicrobial activity against halophilic archaea than the root. Mathematical models have been proposed for predicting the duration of antimicrobial effect and reducing the population of halophilic archaea depending on the dose of applied horseradish. The models show high agreement with the experimental data (the coefficients of determination R2 are equal to 0.992-0.999).