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Modeling of Shigella flexneri inactivation by combination of ultrasound, pH and nisin

Freitas, Leonardo Luiz de, Prudêncio, Cláudia Vieira, Peña, Wilmer Edgard Luera, Vanetti, Maria Cristina Dantas
Lebensmittel-Wissenschaft + [i.e. und] Technologie 2019 v.109 pp. 40-46
Shigella flexneri, adenosine triphosphate, cell viability, death, models, nisin, pH, pathogens, response surface methodology, storage conditions
The Response Surface Methodology (RSM) was used to establish a predictive model of inactivation of S. flexneri using ultrasound time of 5–20 min, pH of 4.0–7.0 and nisin concentration of 29.1–291.1 μM as independent variables. In addition, a survival of S. flexneri at 7 °C for 120 h after treatment with ultrasound and nisin was evaluated as well as the ATP leakage. The response surface model (RS model) had a goodness fit with R2 and Adj.R2 of 0.942 and 0.916, respectively. The parameters of the RS model had a good performance and can be considered validated. The results demonstrated that at pH below 5.0, microbial death increases when ultrasound combined with nisin was used. The results showed that the pathogen inactivation is most pronounced immediately after treatment with ultrasound and nisin, but the viable cell number continues to reduce under storage conditions at 7 °C for 120 h. The microbial inactivation had a correlation with the leakage of ATP to the extracellular medium after the treatment.