Ľubomír Valík

This study aimed to quantify the weight loss of coffee cream (10 % fat) packaged in 10 g and 5 g polystyrene (PS) tubes over 316 days. A total of 13,760 weight measurements were performed across four production batches. Significant linear dependence between the absolute weight of coffee cream and time was observed, with negative slopes of –0.009 g/d and –0.007 g/d, and R² values of 0.990 and 0.996 for 10 g and 5 g tubes, respectively. Considering the surface area of the PS tube without its aluminium lid, water vapour transmission rates were calculated as 3.34 ±0.08 g/m²·d for 10 g tubes and 2.56 ±0.07 g/m²·d for 5 g tubes. Time required to decrease the weight of the cream by 10 % was 137.0 ±3.0 days for 10 g fillings and 84.0 ±1.9 days for 5 g fillings. Conversely, a loss of 1 g occurred over 110.7 ±2.4 days and 144 ±3.3 days in 10 g and 5 g tubes, respectively. These findings provide producers with an estimate of the excess amount of coffee cream needed to maintain the declared value in PS packaging material, depending on the intended shelf life.

The sorption isotherm (SI) of?dried tomatoes was studied at?three different temperatures, 15, 25, and 35 ?C, using a?static gravimetric method. The modified forms of?the Guggenheim-Anderson-de Boer (mGAB), Halsey (mHAL), Henderson (mHEN)...

Monitoring the microbiological quality of air in developing and least-developed countries, particularly in small and medium-sized food manufacturing enterprises, is a major challenge owing to economic and technical constraints. This study aimed to address the issue and observe the feasibility of using the gravimetric method as a less expensive and reliable alternative to the standard but the more expensive volumetric method. The gravimetric and volumetric methods were used to assess the microbiological quality of indoor air in the dairy industry. The gravimetric method was accomplished as per the index of microbiological air contamination (IMA) and the volumetric method using an aeroscope. Obtained results were compared using the statistical t-test and correlation test. Both methods produced quite similar results with a p-value > 0.210, which is much higher than the significance level of 0.05, and with Pearson’s correlation coefficient R > 0.996, which shows a strong positive association between the two data sets. The obtained data suggest that the gravimetric method can give results similar to the volumetric method and it can be used to monitor the microbiological quality of industrial air as a good alternative. However, a comprehensive standardization of the gravimetric method is recommended prior to its application.

The growth of two pairs of co-cultures (Escherichia coli/Geotrichum candidum and Staphylococcus aureus/Geotrichum candidum) with a starter culture of lactic acid bacteria was studied in milk at temperatures ranging from 15 °C to 21 °C, related to the ripening of artisanal cheese. For an inoculum of approximately 10⁶ CFU/mL, LAB not only induced an early stationary phase of E. coli (two isolates BR and PS2) and S. aureus (isolates 2064 and 14733) but also affected their death phase. In co-cultures with LAB and G. candidum, the numbers of E. coli and S. aureus increased in 2 logs and 1 log, respectively, reaching maximum population densities (MPDs) of less than 5 and 4 logs, respectively. After that, the populations of both bacteria represented with two isolates decreased in more than 2 logs and 3 logs within 2 days compared to their MPDs, respectively. G. candidum was found to be the subject of interactions with LAB within a given temperature range only partially. To develop a tertiary model for the growth curves of the populations, a one-step approach was used, combining the Huang-Gimenez and Dalgaard primary model with secondary square-root models for growth rate and lag time. Furthermore, the reparametrized Gompertz-inspired function with the Bigelow secondary model was used to describe the death phase of the E. coli and S. aureus isolates. The prediction ability of the growth of the H-GD tertiary model for co-cultures was cross-validated within the isolates and datasets in milk and milk medium with 1% NaCl. The study can be used as knowledge support for the hygiene guidelines of short-ripened raw milk cheeses, as was our case in Slovakia.

The growth of two pairs of co-cultures (Escherichia coli/Geotrichum candidum, and Staphylococcus aureus/Geotrichum candidum) with a starter culture of lactic acid bacteria was studied in milk at temperatures related to artisanal cheesemaking ripening. For an inoculum of approximately 106 CFU/mL, LAB not only induced an early stationary phase of E. coli (two strains BR and PS2) and S. aureus (strains 2064 and 14733) but affected their death phase. G. candidum was found to be the subject of interactions with LAB within a given temperature range only partially. To develop a tertiary model for the growth curves of the populations, a one-step approach was used, combining two types of primary models (Huang and Gimenez and Dalgaard) with secondary square root models for growth rate and lag time. Furthermore, the reparametrized Gompertz-inspired function with the Bigelow secondary model was used to describe the death phase of the E. coli and S. aureus strains. The prediction ability of the growth of the H-GD tertiary model for co-cultures was cross-validated within the strains and data sets in milk and milk medium with 1 % NaCl.