612. Steam distillation of taints from cream: II. Investigations on commercial equipment with use of diacetyl and acetoin as reference substances

Abstract

The extent of removal of the reference substances diacetyl and acetoin from water and cream in the Vacreator under varied conditions of operation has been investigated.1. It was not affected by change in diameter or length of the uptake-pipe, or, with water, by changing the position of the equilibrium-valve to the top of the uptake-pipe or by introduction of the steam at the bottom of the pasteurizer bend instead of at the normal steam inlet.2. It was affected only slightly by inclusion of baffles in the uptake-pipe, to provide a more intimate contact of steam and cream.3. With diacetyl in water it was not affected by introduction of the major proportion of the steam via the infuser connexion, and with diacetyl in cream it was not affected until the proportion of steam introduced via the infuser was greater than 50% of the total amount of steam used. With acetoin in both water and cream there was a progressive slight reduction in extent of reference substance removal with increase in proportion of steam introduced via the infuser.4. With diacetyl and acetoin in water it was not affected by increase in rate of flow of steam and cream at constant intensity of treatment.5. With diacetyl it was not affected by temperature of steam distillation over the range 138–197°F., but with acetoin there was a progressive reduction in extent of removal with decrease in distillation temperature.6. Steam is most effectively used if it is applied in separate stages instead of in one stage, i.e., a multiple Vacreator uses steam more efficiently than a single-unit machine. This effect is more marked with diacetyl, which has a high equilibrium coefficient, than with acetoin, which has a low coefficient.7. The equilibrium coefficient computed from steam treatment of diacetyl solutions in the Vacreator is of the same order as that determined by the laboratory continuous equilibrium vaporization apparatus.8. The efficiency of cream-deodorization equipment may be lowered by condensation of vapour back into the liquid, e.g. by use of excess cooling water in the Vacreator jackets.9. There are indications that removal of diacetyl from cream is somewhat slower than from water.The thanks of the author are due to Mr J. K. Scott for helpful discussion, to Mr E. R. Elley who did the analytical work, and to Mr B. Le Heron for assistance in the operation of the Vacreator and collection of samples.