Several cases of consumer complaints to the still soft beverages – fruit drinks and ice teas were analysed. The visible impurities and slight sensory changes were observed, sediment was formed by microbial cells. The bacteria were isolated and identified as <I>Asaia</I> sp. The identification was confirmed by PCR technique. The sensitivity of bacteria to preservative agents especially to the sodium benzoate, potassium sorbate and dimethyldicarbonate was evaluated in model samples and in the real conditions of the beverage. The minimal inhibitory concentrations were estimated as well as the factors affecting the sensitivity of bacteria. Besides the stabilisation of drinks the general possibilities of decay prevention were considered, the efficiency of cleaning and sanitation procedures were evaluated, including the comparison of various sanitation agents.

Sedláčková P., Čeřovský M., Horsáková I., Voldřich M. (2011): Cell surface characteristic of Asaia bogorensis -spoilage microorganism of bottled water. Czech J. Food Sci., 29: 457-461.The ability of bacteria to attach to a surface and develop a biofilm has been of considerable interest for many groups in the food industry. Biofilms may serve as a chronic source of microbial contamination and the research into biofilms and cells interactions might help to improve general understanding of the biofilm resistance mechanisms. Multitude of factors, including surface conditioning, surface charge and roughness and hydrophobicity, are thought to be involved in the initial attachment. Hydrophobic interactions have been widely suggested as responsible for much of the adherence of cells to surfaces. Cell-surface hydrophobicity is an important factor in the adherence and subsequent proliferation of microorganisms on solid surfaces and at interfaces. In the present study, we have estimated the cell-surface characteristics of Asaia bogorensis -isolated contamination of flavoured bottled water and compared its ability to colonise surfaces which are typical in the beverage production -stainless steel, glass and plastic materials.

During the last three seasons the specific softening of pickled cucumbers was observed. The defective samples were analysed, but no microbial contamination was confirmed and no residual enzyme activity as well. The hypothesis of residual activity of microbial pectinases and cellulases as the most probable softening cause was proposed. The cellulolytic and pectolytic activities of nineteen strains of moulds and yeasts isolated from the samples of soils, cucumbers and cucumber plants rests were compared. The inactivation parameters (D and z values) of pectolytic enzymes of the most active strains were determined. The inhibitory effect of Ca 2+ addition was evaluated within the model experiments. The residual enzyme activities were confirmed as the main cause of the defect, together with other factors such as the characteristic composition of microbial contamination, the stress or other damage of the cucumbers during the postharvest manipulation (chilling injury, humidity stress, etc.), microbial contamination of cucumbers before processing, conditions of washing, heat treatment parameters, etc. The practical recommendations for the prevention of the defect were formulated.Keywords: cucumbers; effect of Ca 2+ ; softening of sterilised vegetables; cellulolytic activity; pectolytic activity; mould Pasteurised cucumbers in acidic brine are one of the traditional Central European foodstuffs (e.g. Znojemské okurky and other brands). During the last three seasons the specific quality defect was observed. The products complied with specifications just after the production process (sorting, washing, pickling, sealing and pasteurisation) but after several months of storage the maceration of surface layers of cucumbers was observed. Similar phenomenon was described in fifties in the production of fermented cucumbers in brine, the softening was caused by fungal polygaracturonases and cellulases, which were introduced into the brine mainly by way of fungus laden flowers that remain attached to the green cucumbers (Raymond et al. 1959). Various inhibitory treatments including the use of plants rich in hydrolysable tannins (grape, persimmon, dog wood, blueberry, etc.) were described (Bell et al. 1962). Leafs of grapes are often used as a traditional part of the recipe also for the production of pasteurised pickled cucumbers, but more often the calcium is used to improve the texture. The mechanism of calcium effect is known and often studied, divalent cations form bonds with the dissociated free carboxyl groups of adjacent pectin molecules to form more rigid structure (e.g. Fleming et al. 1987). The firmness effect of calcium depends on the degree of pectin methylation and amount of calcium added (Hudson & Buescher 1986; Howard & Buescher 1990;Krall & McFeeters 1998), the hardening effect of calcium surprisingly increases with pH reduction, below pH 5 the relative effectiveness of calcium in reducing rate of softening increases as pH decreased (Hudson & Buescher 1985;McFeeters & Fleming 1989, 1990, 1991.The aim of this...

The protective effect of bacteriophage suspensions (Ds3CZ + Ds20CZ and PcCB7V + PcCB251) on phytopathogenic bacteria causing soft rot of potato tubers, namely Dickeya dianthicola (D50, D200) and Pectobacterium carotovorum (P87, P224), was observed in ex vivo and in vitro experiments. Ex vivo tests were performed (with air access) on potato slices, on cylindrical cuts from the center of the tubers, and directly in whole potato tubers. In vitro experiments were carried out in a liquid medium using RTS-8 bioreactors, where bacterial growth was monitored as optical density. In particular, the inhibitory effects of phages were confirmed in experiments on potato slices, where suppression of rot development was evident at first glance. Phage treatment against selected bacteria positively affected potato hardness. Hardness of samples treated with bacteria only was statistically significantly reduced (p < 0.05 for D50 and p < 0.001 for D200 and P87). Ex vivo experiments confirmed significant inhibition of P87 symptom development, partial inhibition of D200 and D50 in phage-treated tubers, and no effect was observed for P224. The inhibitory effect of phages against bacteria was not observed in the in vitro experiment.

After a general introduction and introduction to acetic acid bacteria, this work focuses on the genus Asaia, which causes sensory defects in non-alcoholic beverages. Asaia representatives have strong adhesive properties for materials used in the food industry, where they subsequently form biofilms and are highly resistant to chemical preservatives. After the basic characteristics of the genus Asaia and its influence on humans, the main part of the paper deals with microbial contamination of beverages by these bacteria. The paper summarizes the knowledge of the influence of packaging materials on the development of defects in beverages and the use of natural bioactive substances and plant extracts as an alternative to maintaining the microbiological stability of beverages.