Modelling the inactivation of Staphylococcus aureus at moderate heating temperatures

Abstract

The survival of bacterial contaminants at moderate processing temperatures is of interest to many food producers, especially in terms of the safety and quality of the final products. That is why the heat resistance of Staphylococcus aureus 2064, an isolate from artisanal Slovakian cheese, was studied in the moderate temperature range (57–61 °C) by the capillary method. The fourth decimal reduction time t<sub>4D</sub>- and z-values were estimated in two steps by traditional log-linear Bigelow and non-linear Weibull models. In addition, a one-step fitting procedure using the Weibull model was also applied. All the approaches provided comparable t<sub>4D</sub>-values resulting in the following z-values of 11.8 °C, 12.3 °C and 11.3 °C, respectively. Moreover, the one-step approach takes all the primary data into z-value calculation at once, thus providing a more representative output at the reasonable high coefficient of determination R<sub>2</sub> = 0.961

Decontamination Efficiency of Thermal, Photothermal, Microwave, and Steam Treatments for Biocontaminated Household Textiles

“…In our case, however, it should be pointed out that the test samples were impregnated with a suspension of microorganisms before the photothermal treatment, which may have further contributed to the irregular migration of moisture and the inhomogeneous heating of the fibre. This finding is consistent with previous studies [52,58,59].…”

“…Research on the applicability of a prediction model should be expanded to include other temperature-resistant microorganisms typically found on textiles in hospitals and nursing homes, such as temperature-resistant Enterococcus faecium. It is also necessary to consider the preparation and treatment conditions (pH, temperature, and moisture content) that could be used to predict the microorganism reduction efficiency of textile hygiene processes more reliably and eliminate long-term testing procedures [48][49][50][51][52].…”

Refined approach to the evaluation of heat resistance applied to Enterobacteriaceae in cheese stretching

“…To evade non-linearity at the beginning of inactivation curves, Lehotová et al (2021) suggested using t 4D -value (fourth decimal reduction time) as the time needed to lower the microbial density by ten-thousandfold. This attempt resembles our point of view in an effort to use the advantages of both log-linear and nonlinear models.…”

“…Nevertheless, in some cases, t 4D -values can be longer than the operating period of the studied technological process, which complicates the optimisation of the heating regime. For example, in Staphylococcus aureus, Lehotová et al (2021) determined t 4D -values at 55, 57, and 61 °C as long as 122.3, 71.9, and 37.0 min, respectively.…”

“…The presence of Enterobacteriaceae in a cookerstretcher seems appealing because cheese stretching can be the only heat treatment used. Typically, cooking water is kept at a temperature of 82-85 °C (Bylund 1995), while the temperature of stretched curd rises to about 60-70 °C (Lehotová et al 2021). These conditions are close to thermisation (about 57-68 °C for 5 s to 30 min) or pasteurisation (minimally 63 °C for 30 min or 72 °C for 15 s) (Dash et al 2022).…”