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To investigate the effects of Lactobacillus casei on the fermentation and flavor of Cheddar cheese slurries, three slurries, i.e., CONTROL by blending Na-caseinate, cream, additives, and other minerals, CASEI by adding Lactobacillus casie AHU 1055 to the CONTROL, and CAGSH by adding the lactobacilli and glutathion to the CONTROL, were prepared. All the slurries were fermented at 30℃ for seven days, and the pH, viable cells, and viscosity were measured everyday during the fermentation. To characterize the flavor of the cheese slurries, free fatty acids, bitter peptides, and volatile aroma compounds were analyzed by gas chromatography and mass spectrometry after the 7-day fermentation. The addition of the lactobacilli increased the acid production and the number of viable cells. The total amount of free fatty acids in CASEI and CAGSH were 1.3 and 1.4 times higher than that of CONTROL, respectively, by accelerated lipolysis by Lb. casie AHU 1055. The composition of free fatty acids in all the slurries was similar to that of milk fat. The amount of bitter peptides in CASEI and CAGSH were much lower than that of CONTROL, presumably by that Lb. casie AHU 1055 produce enzyme degrade bitter peptides. Identified aroma compounds were mostly aldegydes, alcohols, ketones and esters. Propanal, 3-methyl-1-butanol and 3-methyl-2-butanol were identified in CONTROL, and 2-propanol, 3-methyl-1-butanol, 2-pentanol, 2-pentanone, 2-heptanone, ethyl butyrate, ethyl hexanoate and toluene in CASEI. The volatile aroma compounds in CAGSH were identical to those of CASEI, but the relative amounts were different; i.e., 2-propanol, 2-pentanol, and 2-heptanol were decreased while 2-pentanone and 2-heptaone were increased in CAGSH.
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