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

• Published in: Food science & technology 2019-07, Vol.109, p.40-46
• Main Authors: Freitas, Leonardo Luiz de, Prudêncio, Cláudia Vieira, Peña, Wilmer Edgard Luera, Vanetti, Maria Cristina Dantas
• Format: Article
• Language: English
• Subjects: Nisin; Response surface methodology; Shigella flexneri; Ultrasound
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2019.03.045

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. •The number of viable cells of S. flexneri reduces depending on the ultrasound time, pH of medium and nisin concentration.•The mathematical model for S. flexneri inactivation by ultrasound and nisin was validated.•Ultrasound treatment under conditions of low pH promotes greatest cell inactivation.•The bacterial inactivation continues under storage conditions at 7 °C in the presence of nisin.•ATP leakage was observed immediately after treatment with ultrasound and nisin.