Modeling of Combined Processing Steps for Reducing Escherichia coli O157:H7 Populations in Apple Cider

Abstract

Probabilistic models were used as a systematic approach to describe the response of Escherichia coli O157:H7 populations to combinations of commonly used preservation methods in unpasteurized apple cider. Using a complete factorial experimental design, the effect of pH (3.1 to 4.3), storage temperature and time (5 to 35°C for 0 to 6 h or 12 h), preservatives (0, 0.05, or 0.1% potassium sorbate or sodium benzoate), and freeze-thaw (F-T; ؊20°C, 48 h and 4°C, 4 h) treatment combinations (a total of 1,600 treatments) on the probability of achieving a 5-log 10 -unit reduction in a three-strain E. coli O157:H7 mixture in cider was determined. Using logistic regression techniques, pH, temperature, time, and concentration were modeled in separate segments of the data set, resulting in prediction equations for: (i) no preservatives, before F-T; (ii) no preservatives, after F-T; (iii) sorbate, before F-T; (iv) sorbate, after F-T; (v) benzoate, before F-T; and (vi) benzoate, after F-T. Statistical analysis revealed a highly significant (P < 0.0001) effect of all four variables, with cider pH being the most important, followed by temperature and time, and finally by preservative concentration. All models predicted 92 to 99% of the responses correctly. To ensure safety, use of the models is most appropriate at a 0.9 probability level, where the percentage of false positives, i.e., falsely predicting a 5-log 10 -unit reduction, is the lowest (0 to 4.4%). The present study demonstrates the applicability of logistic regression approaches to describing the effectiveness of multiple treatment combinations in pathogen control in cider making. The resulting models can serve as valuable tools in designing safe apple cider processes.

Extractable Organic Components and Nutrients in Wastewater from Dairy Lagoons Influence the Growth and Survival of Escherichia coli O157:H7

“…However, these organisms were not killed when the pH of the effluent was raised to 6.8 (15). Acidification with organic acids is also an established practice for pathogen reduction in foods (5,(36)(37)(38). In contrast, our studies suggest that components of wastewater are inhibitory to the growth of E. coli O157:H7 at neutral pH.…”

Combined effect of mild heat and acetic acid treatment for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an asparagus puree

“…1983) and the accumulation of toxic anions (Eklund 1985). In addition, the inhibitory effects of OAs can be modulated by temperature, with increasing temperature enhancing the effectiveness of OA (Uljas et al. 2001).…”

“…2001). To obtain a 5‐log reduction of E. coli O157:H7 in apple cider, lower pH or higher storage temperature is desirable (Uljas et al. 2001) and may be explained by an alteration of the permeability of microbial membranes as a result of increasing temperature.…”

Antimicrobial Efficiency of Essential Oil and Freeze–Thaw Treatments against Escherichia coli O157:H7 and Salmonella enterica Ser. Enteritidis in Strawberry Juice

“…However, it is known that freezing and thawing cannot fully eliminate the pathogen populations. Other stresses, such as low pH and preservatives, are needed to combine with the freeze–thaw treatment to enhance the antimicrobial activity against the pertinent pathogens (Uljas and others 2001). …”