THE SOURDOUGH MICROFLORA - CHARACTERIZATION OF HETEROFERMENTATIVE LACTIC-ACID BACTERIA BASED ON ACIDIFICATION KINETICS AND IMPEDANCE TEST

Forty strains of Lactobacillus brevis subsp. lindneri, L. brevis, L. f ructivorans, L. fermentum and L. cellobiosus isolated from Italian whe at sourdoughs and 5 ATCC type strains (one per species) were character ized on the basis of 7 parameters of acidification kinetics and 3 impe dance test parameters. The total change and the maximum rate of conduc tance were statistically correlated with several parameters of acidifi cation kinetics. The Principal Component Analysis (PCA) conducted on 6 parameters of acidification kinetics differentiated the strains and f ormed 5 groups according to species number. The differences between la ctic acid bacteria isolated from the sourdoughs and the type strains, and several strains that behaved differently from their representative group were shown. The characterization defined by the analytical proc edure, with a slight exception for L. cellobiosus, was confirmed durin g the sourdough fermentation with selected starters. A comparison betw een the acidification activities of sourdough hetero- and homo-ferment ative (previously characterized) lactic acid bacteria was given.