Differences in the Ability of Lactic Streptococci to Form Aldehydes from Certain Amino Acids
Year: 1958
Type: article
Abstract: Resting cells of five cultures of lactic streptococci were examined as to their ability to form flavorful aldehydes from four amino acids.Two strains of Streptococcus cremoris~ two strains of Streptococcus tactis, and one strain of Streptococcus lactis ear.maltigenes were incubated with isoleucine, valine, methionine, and phenylalanine, and the resulting aldehydes were isolated and identified as their 2,4-dinitrophenylhydrazones.The incubated mixtures of the amino acids and S. laetis ear.maltigenes cells were the only ones in which 2-methylbutanal~ 2-methylpropanal, ~-methylthiopropanM, and phenylacetaldehyde accumulated in sufficient quantities to allow isolation and identification of their derivatives.One of the strains of S. lactis formed trace quantities of these aldehydes; whereas, neither strain of S. cremoris, nor the freshly isolated strain of S. lactis, appeared to degrade the amino acids to aldehydes.The activity of the alpha-keto acid decarboxylase system present in some lactic streptococci and its possible role in the development of Cheddar cheese flavor are discussed.Streptococcus lactis and Streptococcus lactis ear.maltigenes are known to possess a transaminase system which effects the transfer of the amino group of leucine to alpha-ketoglutarie acid, resulting in the formation of glutamic acid and alpha-ketoisocaproic acid (13).S. lactis ear.maltige~es possesses, in addition, an enzyme which decarboxylates this keto acid to 3-methylbutanM, the compound responsible for the typical aroma and flavor of milk cultures of this variant (14).S. lactis cells, on the other hand, produce little or no 3-methylbutanal from the keto acid (13).Keeney and Day (11) suggest that the Strecker degradation of amino acids yielding various aldehydes may play a prominent role in Cheddar cheese flavor development.Bassett and Harper (2) reported the presence of pyruvic and alphaketoglutaric acids and trace quantities of oxalacetic and alpha-ketoisoeaproie acids in Cheddar cheese.They also found small quantities of acetone, acetaldehyde, and a five-carbon carbonyl compound.The foregoing reports have prompted an investigation of the abilities of various organisms associated with the ripening of Cheddar cheese to convert certain amino acids to flavorful aldehydes.The present report contributes further information on aldehyde formation from isoleucine, valine, methionine, and phenylalanine by cells of S. lactis ear.maltigenes, as well as by two nonmalty strains of S. lactis and two strains of S. cremoris. EXPERI]YIENTAL PROCEDURE Cultures.Two strains of S. lactis, designated as L2 and Lr, two strains of S. cremoris, C14 and Cs, and one strain of S. lactis var.maltigenes, designated as M1, were employed as the test cultures throughout this experiment.These
Source: Journal of Dairy Science
Authors: Patricia Mac Leod, M.E. Morgan
Institution: Storrs Agricultural Experiment Station
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W1978479193