In the present study, the physicochemical, antioxidant and antimicrobial properties of three medicinal plants - thyme, cotton thistle and hawthorn fruit from the Western Rhodope Mountains, Bulgaria were investigated. In the first stage, the physicochemical characteristics (moisture, ash, carbohydrates, proteins and vitamin C) of the three herbs were determined. In the second stage, four types of extracts (aqueous, oil, methanolic and ethanolic) from them were prepared and the total phenolic content, presence of phenolic compounds (flavonoids and phenolic acids), antioxidant activity and their antimicrobial properties were determined. Thyme was characterized by the highest ash, proteins and vitamin C contents. The hawthorn fruit was characterized by the highest moisture and carbohydrate contents. The 70% ethanolic extracts of the three herbs exhibited the highest levels of phenolics and consequently a pronounced antioxidant activity, compared to the other three types of extracts. The flavonoid quercetin-3-ß-glucoside was in highest concentration in the thyme and hawthorn fruit, while myricetin dominated in the cotton thistle. The phenolic acid content analysis showed a prevalence of rosmaric acid in thyme, whereas chlorogenic acid was detected in highest concentration in hawthorn fruit and cotton thistle. High antimicrobial potential of the ethanolic and methanolic extracts was observed.

In this experimental work, the microbiological, physicochemical, organoleptic and rheological characteristics of probiotic Bulgarian yoghurts produced by ultrafiltration of goat’s milk using different volume reduction ratio (2 and 3) and several probiotic starters (MZ2f, MZ2f + Bifidobacterium bifidum BB – 87, MZ2f + Lactobacillus acidophilus LAB – 8) were studied. It was established that the dry matter, protein, fat contents, the number of lactic acid bacteria, titratable acidity and the dynamic viscosity increased and the pH decreased with the rise of volume reduction ratio during ultrafiltration. All yoghurts exhibited Bingham plastic flow behavior. We recommend to use a volume reduction ratio of 3 and MZ2f + Bifidobacterium bifidum BB – 87 to produce probiotic Bulgarian yoghurts with the highest dry matter, protein, fat contents; counts of viable lactic acid cells, viscosity and the best sensory characteristics in the range of this experiment.