MONITORING OF MICROBIAL CHANGES IN FRESH FRUIT BEVERAGES WITH THE ADDITION OF SELECTED MEDICINAL PLANTS

Abstract

In this study, we assessed the microbiological quality of fresh fruit smoothies made from three types of fruit, including versions with added medicinal plants. Our aim was to get closer to home conditions of smoothie preparation, so we did not use essential oils of medicinal plants but their whole parts. We quantified total microorganisms, coliform bacteria, yeasts, and filamentous fungi using the plate dilution method. Total microbial counts ranged from 5.12 to 6.67 log CFU/mL, with most samples showing a decrease after the addition of medicinal plants, particularly Thymus serpyllum. Coliform bacteria levels varied from 1.48 to 2.70 log CFU/mL, with the highest counts recorded in pear-based smoothies. A reduction in coliforms was observed only in samples containing apple and Thymus serpyllum, pear and Thymus vulgaris, and orange with Mentha piperita. Yeast counts ranged from 3.10 to 5.46 log CFU/mL, with medicinal plants influencing their abundance. Three samples showed no colonies and a low level of filamentous fungi contamination.. Morphological identification of microscopic fungi revealed four genera: Alternaria, Aspergillus, Cladosporium, and Penicillium. Cladosporium was the most frequently isolated genus (50% of samples), while potentially toxinogenic Aspergillus, Penicillium, and Alternaria did not exceed 25% occurrence. Among yeasts, Geotrichum candidum was dominant. MALDI-TOF MS analysis identified three genera and six species of coliform bacteria. Klebsiella oxytoca was the most common (48%), followed by Enterobacter cloacae (19%) and Raoultella ornithinolytica (14%). Our findings suggest that the addition of medicinal plants into smoothies may enhance microbiological quality by reducing microbial contamination, though further investigation is needed to determine their impact on coliform bacteria.