Analysis of volatile compounds produced by 2 strains of Lactococcus lactis isolated from leben (Tunisian fermented milk) using solid-phase microextraction-gas chromatography.
The volatile compounds that characterize Leben during fermentation with 2 Lactococcus lactis strains (SLT6 and SLT10) in flasks, in a 100-L fermentor, and during storage at 4 degrees C, were investigated and compared to those from commercial Leben. Volatile compounds from Leben were concentrated by a Carboxen-PDMS fiber and analyzed by GC-MS. These compounds include acids, alcohols, aldehydes, ketones, sulfur compounds, and hydrocarbons. Commercial Leben presented a poor volatile profile compared to the laboratory-made Leben. The mixed culture of 2 Lactococcus lactis strains resulted in higher volatile compound formation than the single strain culture. The GC volatile profiles of Leben produced in flask and in the 100-L fermentor were similar. Changes in volatile compounds were observed during storage at 4 degrees C. The effect of culture conditions on production of volatiles by SLT6 strain was studied. Aeration (0.1 mL/min) and agitation enhanced the production of diacetyl, acetoin, 3-methylbutanal, and 3-methylbutanol. Fermentation at pH 5 had no effect on volatile production.
Ziadi
M
M
Laboratoire d'Ecologie et de Technologie Microbienne, Inst. Natl. des Sciences Appliquées et de Technologie, BP 876, 1080 Tunis, Tunisia.
Wathelet
J P
JP
Marlier
M
M
Hamdi
M
M
Thonart
P
P
D000093:Acetoin / Q000032:analysis; D000438:Alcohols / Q000032:analysis; D000447:Aldehydes / Q000032:analysis; D000818:Animals; D002849:Chromatography, Gas / Q000379:methods*; D003931:Diacetyl / Q000032:analysis; D005285:Fermentation; D005511:Food Handling / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D006838:Hydrocarbons / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007659:Ketones / Q000032:analysis; D013294:Lactococcus lactis / Q000737:chemistry / Q000378:metabolism*; D008892:Milk / Q000382:microbiology*; D052617:Solid Phase Microextraction; D013457:Sulfur Compounds / Q000032:analysis; D013696:Temperature; D013997:Time Factors; D014416:Tunisia; D014835:Volatilization
D000438:Alcohols; D000447:Aldehydes; D006838:Hydrocarbons; D007659:Ketones; D013457:Sulfur Compounds; D000093:Acetoin; D003931:Diacetyl