he large variety of cheeses is mainly due to the kind of microorganisms that develop during cheese ripening. Thus, the choice of the starter is very important to preserve the peculiarity of the final product. The principal characteristics of starter bacteria are acidifying, proteolytic, lipolytic, aromatic and reducing properties. In this study, the classical and alternative methods for determining the activities of lactic acid bacteria were used. Four strains: Enterococcus faecalis, Lactococcus lactis, Lactobacillus helveticus and Lactobacillus delbrueckii subsp. bulgaricus were studied. The initial total viable cell count was determined to evaluate the titratable acidity (analysed every 2 h for 24 h), the variation of pH and oxidation-reduction potential (measured every 30 min for 24 h) and the total metabolic activity by conductimetric technique using a Malthus AT instrument. All the tests were repeated 8 times. Some parameters were chosen for each activity in order to carry out statistical evaluation. The data were processed by STAT VIEW, verifying the eventual correlation to the number of inoculate cells using descriptive statistics. Moreover the correlation matrix between all the parameters was calculated in order to estimate which is the most influential on the conductimetric activity. The statistical evaluation of the data led to the following conclusions: the number of initial cells influences the conductimetric analysis; maximum values during the entire period of incubation are the most repeatable parameters for all the activities; the maximum value of conduction is highly correlated with the maximum values of the other metabolic properties; flex point, determined through the logistic curves, is highly repeatable.
Attività metaboliche dei batteri lattici di interesse caserio: valutazione mediante tecnica conduttimetrica e tecniche classiche
Brasca M;Lodi R
2001
Abstract
he large variety of cheeses is mainly due to the kind of microorganisms that develop during cheese ripening. Thus, the choice of the starter is very important to preserve the peculiarity of the final product. The principal characteristics of starter bacteria are acidifying, proteolytic, lipolytic, aromatic and reducing properties. In this study, the classical and alternative methods for determining the activities of lactic acid bacteria were used. Four strains: Enterococcus faecalis, Lactococcus lactis, Lactobacillus helveticus and Lactobacillus delbrueckii subsp. bulgaricus were studied. The initial total viable cell count was determined to evaluate the titratable acidity (analysed every 2 h for 24 h), the variation of pH and oxidation-reduction potential (measured every 30 min for 24 h) and the total metabolic activity by conductimetric technique using a Malthus AT instrument. All the tests were repeated 8 times. Some parameters were chosen for each activity in order to carry out statistical evaluation. The data were processed by STAT VIEW, verifying the eventual correlation to the number of inoculate cells using descriptive statistics. Moreover the correlation matrix between all the parameters was calculated in order to estimate which is the most influential on the conductimetric activity. The statistical evaluation of the data led to the following conclusions: the number of initial cells influences the conductimetric analysis; maximum values during the entire period of incubation are the most repeatable parameters for all the activities; the maximum value of conduction is highly correlated with the maximum values of the other metabolic properties; flex point, determined through the logistic curves, is highly repeatable.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
