Lactic streptococci and the fruity flavor defect of cheddar cheese

Graduation date: 1967The tendency for certain single- and mixed-strain lactic\ud starter cultures to develop a fruity and/or fermented off-flavor\ud in ripening Cheddar cheese was traced to certain strains of\ud Streptococcus lactis in the starter. A very intense fruity and/or\ud fermented flavor developed in experimental cheeses when one particular\ud S. lactis strain was used as a component microorganism\ud in the starter culture. Contrary to previous implications, strains\ud of Streptococcus diacetilactis did not produce a fruity and/or fermented\ud flavor in experimental cheeses made with starter cultures\ud containing these organisms. Mixed-strain cultures of Streptococcus\ud cremoris were used to produce control cheeses, which did not develop\ud the fruity and/or fermented flavor defect.\ud The starter culture and treatment of the cheese milk were\ud the only variables used in the cheesemaking trials. Results obtained indicate that the specific species and/or strain of lactic streptococci\ud contained in the starter culture affect the flavor score and type of\ud flavor in the resultant cheese, independent of the temperature of\ud the heat treatment or hydrogen peroxide-catalase treatment of\ud cheese milk.\ud There were no apparent correlations between "normal" and\ud "defective" starter cultures for the level of proteolytic activity or\ud production of acetaldehyde or diacetyl to the development of fruity\ud and/or fermented off-flavor in cheeses. Existing procedures for\ud the quantification of acetaldehyde, diacetyl and volatile esters were\ud adapted and modified for determining the concentration of these compounds\ud in cheese curd and ripened cheese. The method of slurry\ud preparation, type of diluent and the pH were factors found to affect\ud the recovery rate for acetaldehyde from cheese.\ud The relative flavor preference for typical experimental cheeses\ud was determined with the aid of a flavor panel. A sample of fermented-\ud unclean cheese received the lowest hedonic flavor score, whereas\ud the flavor score of a slight fruity and/or fermented sample compared\ud favorably with that of the reference sample