Production of flavor compounds: aldehydes and alcohols from leucine by microencapsulated cell-free extracts of Streptococcus lactis var. maltigenes

Cell‐free extract (CFE) from Streptococcus lactis var. maltigenes was examined for its ability to catalyze the formation of 3‐methyl butanal and 3‐methyl butanol from leucine as affected by pH, substrate concentration and gradual addition of NADH. Pseudo Km and vmax, determined for CFE were 6.5 × 10‐3 M and 7.1 μmol/liter‐min when 3‐methyl butanal was measured and 9.4 × 10‐3 M and 2.4 μmol/liter‐min for 3‐methyl butanol. The CFE, leucine and cofactors were encapsulated in milkfat and incubated for 40 h at 22°, Rate of formation and final concentration of 3‐methyl butanal and 3‐methyl butanol were related to substrate concentration, indicating that flavor intensity can be controlled with encapsulated enzymes by limiting substrate concentration. Diffusion of 3‐methyl butanol and acetic acid from microcapsules was affected by concentration and their lipophilic/hydrophilic character. Altering the pH of fluid surrounding microcapsules containing CFE had limited effect on the internal pH, as indicated by enzyme probes, demonstrating that capsules provide an environment isolated from the bulk phase of foods.