Impedimetric method for estimating the residual activity of freeze-dried Lactob...

• Author(s): Carvalho, A. Sofia ; Silva, Joana ; Ho, Peter ; Teixeira, Paula ; Malcata, F. Xavier ; Gibbs, Paul
• Date: 2003
• Persistent ID: http://hdl.handle.net/10400.14/6818
• Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
• Subject(s): Residual activity; Lactic acid bacteria; Instrumental methods
• Document Type: Article
• Language: English

Description

The residual activity of Lactobacillus delbrueckii ssp. bulgaricus cultures was analysed using pH and various impedimetric methods (impedance detection time (IDT), conductance and capacitance) to quantify the loss in activity following freeze-drying. The large variation recorded in IDT values for similar levels of activity suggests that IDT is not an adequate parameter for estimating the culture's fermentative activity. Comparison of the impedance signals generated revealed that capacitance yields values that are more reproducible than those of conductance, and also gives a better correlation with pH. Statistical analysis (p<0.05) indicated that there are no significant differences between the capacitance and the pH method when attempting to estimate residual activity.