Steam distillation of taints from cream: V. Vapour/liquid equilibrium relationships for some α-diketones in lactose solution

Steam distillation of taints from cream: VII. Butterfat/water distribution coefficients in relation to vapour/liquid equilibrium coefficients for tainting substances in cream

1. The relationship between vapour/liquid equilibrium coefficient for a tainting substance in cream (mc) as compared with the coefficient for the substance in skim-milk (ms) at 100° C. is given by the formula

where F is the percentage fat content of the cream, and k is the butterfat/skim-milk distribution coefficient at 100° C.

2. The values for the vapour/liquid equilibrium coefficients for acetoin, diacetyl, acetylpropionyl, acetyl-iso-butyryl, acetylvaleryl, acetylcaproyl and acetylbenzoyl in cream, computed by the formula from the equilibrium coefficients for the substances in 4·5% lactose solutions and the distribution ratios at 100° C, were in good agreement with the experimental results for these substances in cream.

3. It was shown that high solubility of a substance in butterfat relative to solubility in skim-milk greatly reduces the steam volatility of the substance from cream.

4. It was concluded that steam volatility of a substance from cream may be affected by temperature of deodorization because of the effect of temperature on the butterfat'skim-milk distribution coefficient.

Steam distillation of taints from cream: VI. Butterfat/lactose-solution distribution coefficients of some reference substances

1. Coefficients of distribution for acetoin, diacetyl and acetylpropionyl between butterfat and skim-milk were measured over a range of temperatures up to 190° F. by passing preheated milk containing the reference substance through an hermetic cream separator and analysing the cream and skim-milk obtained.

2. The coefficients increased with rise in temperature, and the relationship between change in coefficient and change in temperature was linear for all three substances.

3. Coefficients of distribution for acetyl-iso-butyryl, acetylvaleryl, acetylcaproyl and acetylbenzoyl between butterfat and 4·5% lactose solution were measured at 40° and 60° C. by direct separation after equilibration, followed by estimation of the diketone in the lactose solution.

4. Coefficients of distribution at 100° C., obtained by linear extrapolation from these results, were: acetoin, 0·255; diacetyl, 1·27; acetylpropionyl, 5·9; acetyl-iso-butyryl, 20; acetylvaleryl, 23; acetylcaproyl, 152; acetylbenzoyl, 48.

5. The coefficients of distribution for diacetyl and acetylpropionyl between butterfat and 4·5% lactose solution were not affected by change in concentration of the diketone in the lactose solution.