Dried Beetroots: Optimization of the Osmotic Dehydration Process and Storage Stability.

In this study, beetroots were osmotically dehydrated in sugar beet molasses. The input parameters of the drying process were varied: temperature (20 °C, 40 °C, and 60 °C), time (1 h, 3 h, and 5 h), and concentration of sugar beet molasses (40%, 60%, and 80%). Basic quality indicators were determined for the dried beetroot samples: dry matter content, water loss, solid gain, mineral and betaine content, and phenols and flavonoids, as well as antioxidant potential. After optimizing the results, favorable drying parameters were selected: temperature 60 °C, molasses concentration 70%, and processing time 5 h. According to the optimal drying conditions, the beetroots were dried and stored at 4 °C for 28 days. Half of the dried samples were coated with an edible biopolymer coating based on Camelina sativa oilcake, while the other half of the samples remained uncoated. The sustainability study aimed to confirm the effects of the biopolymer coating on the quality and sustainability of the osmotically dried beetroots.

Food grade disinfectants based on hydrogen peroxide/peracetic acid and sodium hypochlorite interfere with the adhesion of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes to stainless steel of differing surface roughness.

This study aimed to evaluate the potential of the bacterium Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes to adhere to stainless steel discs with differing degrees of surface roughness (Ra = 25.20-961.90 nm). Stainless steel is a material commonly used in the food industry for processing equipment, which is regularly exposed to cleaning procedures. The investigation included the commercial disinfectants hydrogen peroxide/peracetic acid and sodium hypochlorite which were evaluated for their antibacterial and anti-adhesion activity. The adhesion was assessed by the standard plate count method, while the broth microdilution method CLSI M07-A10 was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the disinfectants. Based on the MIC values, both disinfectants exerted significant inhibitory effects with MIC values for hydrogen peroxide/peracetic acid and sodium hypochlorite of 250 µg ml-1 and 500 µg ml-1, respectively. Whereas the MBC values were equal to the MIC for all bacteria except for E. coli with values 2-fold higher than the MIC. Obtained results also revealed that all tested bacteria were able to adhere to stainless steel surfaces, although differences were found for strains and surface roughness. The lowest adhesion rate of each strain was recorded on the roughest stainless steel disc at a Ra of 961.90 nm. Further, at a concentration of 1 MIC, the disinfectant sodium hypochlorite reduced initial bacterial adhesion to stainless steel surfaces to a significantly greater extent than the disinfectant hydrogen peroxide/peracetic acid. These findings are consistent with the results obtained by Scanning Electron Microscopy (SEM) analysis, which indicates the great applicability of the tested disinfectants for the control of bacterial adhesion in the food industry.

Influence of culture conditions on co-aggregation of probiotic yeast Saccharomyces boulardii with Candida spp. and their auto-aggregation.

Systemic infections caused by pathogenic Candida species pose a significant threat to public health in the past decades due to increasing resistance to existing antifungal drugs. Given this scenario, probiotics have been suggested as an alternative approach for managing Candida infections. Hence, the purpose of this study was to evaluate whether probiotic yeast Saccharomyces boulardii co-aggregate with Candida spp. as well as to determine their auto-aggregation ability in dependence on temperature (28 °C, 37 °C, 42 °C) and pH (4.5, 7.0, 8.5) after 5 h and 24 h. Our results revealed that the aggregation of tested yeasts was lower in the first 5 h but increased significantly after 24 h. All strains were able to auto-aggregate in different degrees ranging from 47.46 to 95.95% assessed at 24 h of incubation. Among them the highest auto-aggregation values had C. albicans and C. krusei strains followed by probiotic strain S. boulardii, while the less were observed in C. glabrata strains. In addition, co-aggregation between probiotic and Candida strains was strain-specific. It was evident that S. boulardii significantly inhibited the aggregation of C. albicans ATCC 10261, C. krusei ATCC 6258, and C. glabrata ZIM 2369. However, in C. glabrata ZIM 2382, the aggregation was even enhanced. Temperature and pH also affected the ability to aggregate in a different way only after 5 h of incubation, with the highest cell aggregation evidenced at temperature 37 °C in most cases and pH 4.5. These findings may be of importance when trying to establish probiotic use against pathogenic Candida species.

Identification and Characterization of 33 Bacillus cereus sensu lato Isolates from Agricultural Fields from Eleven Widely Distributed Countries by Whole Genome Sequencing.

The phylogeny, identification, and characterization of 33 B. cereus sensu lato isolates originating from 17 agricultural soils from 11 countries were analyzed on the basis of whole genome sequencing. Phylogenetic analyses revealed all isolates are divided into six groups, which follows the generally accepted phylogenetic division of B. cereus sensu lato isolates. Four different identification methods resulted in a variation in the identity of the isolates, as none of the isolates were identified as the same species by all four methods-only the recent identification method proposed directly reflected the phylogeny of the isolates. This points to the importance of describing the basis and method used for the identification. The presence and percent identity of the protein product of 19 genes potentially involved in pathogenicity divided the 33 isolates into groups corresponding to phylogenetic division of the isolates. This suggests that different pathotypes exist and that it is possible to differentiate between them by comparing the percent identity of proteins potentially involved in pathogenicity. This also reveals that a basic link between phylogeny and pathogenicity is likely to exist. The geographical distribution of the isolates is not random: they are distributed in relation to their division into the six phylogenetic groups, which again relates to different ecotypes with different temperature growth ranges. This means that we find it easier to analyze and understand the results obtained from the 33 B. cereus sensu lato isolates in a phylogenetic, patho-type and ecotype-oriented context, than in a context based on uncertain identification at the species level.

Adhesion of Candida spp. and Pichia spp. to Wooden Surfaces.

Yeast adhesion to and biofilm formation on surfaces is present in many different environments. In food industry, biofilms may be a source of contaminations, causing food spoilage and reducing quality of products. Candida and Pichia are two common yeast genera involved in the spoilage of some food products. The aim of this study is to assess the potential of Candida and Pichia species to adhere to two types of wooden surfaces (smooth and rough), one of the materials typical for the food processing industry, and investigate the influence of surface roughness of wood on the degree of yeast adhesion. The adhesion of the cells to the wooden surfaces was determined by rinsing them from the surface, followed by methylene blue staining, and quantification after imaging under microscope by automatic counting of viable cells. The results showed that all Candida and Pichia strains were able to adhere to the wooden surfaces in a species- and strain-dependent manner. On the other hand, our data indicated that adhesion by these yeasts was not significantly affected by the roughness of the wood surfaces.

Influence of growth conditions on adhesion of yeast Candida spp. and Pichia spp. to stainless steel surfaces.

An understanding of adhesion behavior of Candida and Pichia yeast under different environmental conditions is key to the development of effective preventive measures against biofilm-associated infection. Hence in this study we investigated the impact of growth medium and temperature on Candida and Pichia adherence using stainless steel (AISI 304) discs with different degrees of surface roughness (Ra = 25.20-961.9 nm), material typical for the food processing industry as well as medical devices. The adhesion of the yeast strains to stainless steel surfaces grown in Malt Extract broth (MEB) or YPD broth at three temperatures (7 °C, 37 °C, 43 °C for Candida strains and 7 °C, 27 °C, 32 °C for Pichia strains) was assessed by crystal violet staining. The results showed that the nutrient content of medium significantly influenced the quantity of adhered cells by the tested yeasts. Adhesion of C. albicans and C. glabrata on stainless steel surfaces were significantly higher in MEB, whereas for C. parapsilosis and C. krusei it was YPD broth. In the case with P. pijperi and P. membranifaciens, YPD broth was more effective in promoting adhesion than MEB. On the other hand, our data indicated that temperature is a very important factor which considerably affects the adhesion of these yeast. There was also significant difference in cell adhesion on all types of stainless steel surfaces for all tested yeast.