Influence of β-lactoglobulin, pH and presence of other aroma compounds on the air/liquid partition coefficients of 20 aroma compounds varying in functional group and chain length

The air/water partition coefficients of 20 aroma compounds varying in functional group and chain length were determined as a function of β-lactoglobulin concentration (0, 0.5, 0.7, 1.0, 2.0%), pH (3, 6, 9) and presence of other aroma compounds in the matrix. Air/liquid partition coefficients of dimethyl sulphide, 1-propanol, diacetyl, 2-butanone, ethyl acetate, 1-butanol, 2-pentanol, propyl acetate, 3-methyl-1-butanol, ethyl butyrate, hexanal, butyl acetate, 1-hexanol, 2-heptanone, heptanal, α-pinene, 2-octanone, octanal, 2-nonanol and 2-decanone were determined by static headspace gas chromatography. The majority of the compounds' partition coefficients decreased with β-lactoglobulin concentration, although not proportionally. Air/liquid partition coefficients of aldehydes and esters demonstrated a decline up to 90%, whereas alcohols were hardly affected by β-lactoglobulin. Larger chain length coincided with lower partition coefficients and thus more efficient retention. Increase in pH generally resulted in a more pronounced decrease in headspace concentrations, although α-pinene and alcohols showed diverting behaviour. The β-lactoglobulin concentration and pH did not demonstrate complementary effects but interacted with each other. Propyl acetate, ethyl butyrate, hexanal, heptanal and octanal increased each other's air/liquid partition coefficients.