FLAVOR PRODUCTION IN EWES MILK AND EWES MILK YOGURT, BY SINGLE STRAINS AND COMBINATIONS OF STREPTOCOCCUS-THERMOPHILUS AND LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS, ISOLATED FROM TRADITIONAL GREEK YOGURT

The flavour production in ewe's milk by 5 Streptococcus thermophilus a nd 4 Lactobacillus delbrueckii subsp bulgaricus strains as well as by their 20 combinations in ewe's milk yoghurt was studied. Samples for a nalysis were taken after 24 h and 5 days of storage at 4 degrees C. Th e flavour compounds (acetaldehyde, acetone, diacetyl and ethanol) were extracted by ether microsteam distillation and were identified and qu antitatively estimated by gas chromatography. The concentrations of fl avour compounds varied considerably among the single strains and their combinations. Acetaldehyde was recognized as the major flavour compon ent, while acetone, diacetyl and ethanol were produced in lower concen trations. The Lb bulgaricus strains produced, generally, higher concen trations of acetaldehyde than the Str thermophilus ones. In the 24 h a s well as in the 5-days ewe's milk yoghurt, the combination ACA-DC 116 /ACA-DC 232 was found to produce the highest acetaldehyde concentratio n (13.14 mg kg(-1)). Changes in the concentrations of flavour compound s were also observed between the 24 h and 5-days samples.