Ethyl ester production by autochthonous Lactobacillus and Enterococcus strains in a goat milk cheese model

ABEIJÓN MUKDSI M. CLAUDIA ; WOLF I.VERÓNICA; PEROTTI M.CRISTINA; MARGALEF M.I; GONZÁLEZ S.N.; MEDINA R.B

Egmond aan Zee - The Netherlands

Simposio; 10th Symposium on Lactic Acid Bacteria; 2011

Abstract Esters are common volatile compounds of cheese that contribute significantly to the overall flavour. Among them, the ethyl esters of short-chain fatty acids confer fruity flavour notes desirable in Italian, Swiss-type, goat and ewe milk cheeses. Our aim was to evaluate the effect of autochthonous lactic acid bacteria (isolated from goat milk cheeses) on the production of ethyl esters in a goat milk cheese model, and the influence of ethanol on ester synthesis. Pasteurized milk cheeses were manufactured under controlled microbiological conditions. Lactobacillus fermentum CRL1446 and  Enterococcus faecium CRL1814, strains with ester-synthesizing ability in vitro, were used as adjunct culture. Cheeses containing only starter culture (mixture of L. delbrueckii subsp. bulgaricus and Streptococcus thermophilus) were used as control. To evaluate the influence of ethanol on ester synthesis, cheeses were elaborated with and without ethanol addition to milk. After 30 and 60 days of ripening at 10°C, the concentration of volatile compounds was determined by solid phase microextraction-gas chromatography (SPME-GC/FID), and sensory evaluation was performed. Higher levels of ethyl acetate, butanoate and hexanoate were detected in experimental cheeses compared to control cheeses, being ethyl butanoate (EtC4) the most abundant. The highest EtC4 levels were detected  in cheeses containing L. fermentum, whether ethanol was added to milk or not. However, in cheeses containing E. faecium, increases were only observed in those with ethanol addition, since this strain produced lower ethanol concentration than L. fermentum. Fruity flavour notes were perceived only in ethanol-added cheeses. Our results demonstrated that the autochthonous strains L. fermentum CRL1446 and E. faecium CRL1814 enhanced ester synthesis and fruity flavour development in a goat milk cheese model, being ethanol concentration a determinant factor.