title: Application of Impedance Microbiology for Evaluating Potential Acidifying Performances of Starter Lactic Acid Bacteria to Employ in Milk Transformation.
abstract: Impedance microbiology is a method that enables tracing microbial growth by measuring the change in the electrical conductivity. Different systems, able to perform this measurement, are available in commerce and are commonly used for food control analysis by mean of measuring a point of the impedance curve, defined "time of detection." With this work we wanted to find an objective way to interpret the metabolic significance of impedance curves and propose it as a valid approach to evaluate the potential acidifying performances of starter lactic acid bacteria to be employed in milk transformation. To do this it was firstly investigated the possibility to use the Gompertz equation to describe the data coming from the impedance curve obtained by mean of BacTrac 4300®. Lag time (λ), maximum specific M% rate (μmax), and maximum value of M% (Yend) have been calculated and, given the similarity of the impedance fitted curve to the bacterial growth curve, their meaning has been interpreted. Potential acidifying performances of eighty strains belonging toLactobacillus helveticus, Lactobacillus delbrueckiisubsp.bulgaricus, Lactococcus lactis, andStreptococcus thermophilusspecies have been evaluated by using the kinetics parameters, obtained from Excel add-in DMFit version 2.1. The novelty and importance of our findings, obtained by means of BacTrac 4300®, is that they can also be applied to data obtained from other devices. Moreover, the meaning of λ, μmax, and Yend that we have extrapolated from Modified Gompertz equation and discussed for lactic acid bacteria in milk, can be exploited also to other food environment or other bacteria, assuming that they can give a curve and that curve is properly fitted with Gompertz equation.
authors: Laboratory of Food Microbiology, Department of Food Science, University of Parma Parma, Italy.
authors: Elena
authors: E
authors: Bancalari
authors: Laboratory of Food Microbiology, Department of Food Science, University of ParmaParma, Italy; Multidisciplinary Interdepartmental Dairy Cente, University of ParmaParma, Italy.
authors: Valentina
authors: V
authors: Bernini
authors: Laboratory of Food Microbiology, Department of Food Science, University of ParmaParma, Italy; Multidisciplinary Interdepartmental Dairy Cente, University of ParmaParma, Italy.
authors: Benedetta
authors: B
authors: Bottari
authors: Laboratory of Food Microbiology, Department of Food Science, University of ParmaParma, Italy; Multidisciplinary Interdepartmental Dairy Cente, University of ParmaParma, Italy.
authors: Erasmo
authors: E
authors: Neviani
authors: Laboratory of Food Microbiology, Department of Food Science, University of ParmaParma, Italy; Multidisciplinary Interdepartmental Dairy Cente, University of ParmaParma, Italy.
authors: Monica
authors: M
authors: Gatti
keywords: BacTrac; Gompertz model; impedance micorbiology; lactic acid bacteria; starter activity