Dry fractionation of fat molecules in a pseudo-steady state

Details Dry fractionation of fat molecules in a pseudo-steady state Dry fractionation of fat molecules in a pseudo-steady state

1997-06-11

1999-02-23

Geist, Gary

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

C11B 300

Patent

active

058745998

DESCRIPTION:

BRIEF SUMMARY
This application is the national phase of international application PCT/EP95/03035 filed Jul. 28, 1995 which designated the U.S.


BACKGROUND OF THE INVENTION

The dry fractionation processes for the fractionation of fats disclosed in the prior art are all based on the use of a system comprising a heat exchanger for the starting oil, a crystalliser for the oil obtained after the heat exchange and a filter press wherein crystals are separated from the liquid components.
Because of the conditions applied during these known dry fractionation processes the products contain large amounts of kinetically unstable crystals. Moreover those known processes require high levels of undercooling, which make the processes difficult to control. As a result of above the products are not optimal for filtering, which results in poor yields and poor separation efficiency.
It would be very beneficial if a dry fractionation could be found, that does not have above drawbacks.


SUMMARY OF THE INVENTION

We have conducted a study in order to find out whether such a process could be developed. This study resulted in an economically feasible (semi-)continuous dry fractionation process for the crystallisation of polymorphic fat molecules. Therefore, our invention concerns a process for the crystallisation of polymorphic fat molecules in a pseudo-steady state process, wherein the crystallisation is performed in a dry fractionation system in such a way that the crystal form of the product is a kinetically-stable crystal form, while during the crystallisation a .sigma.-value is maintained below 0.5, preferably below 0.3, more preferably between 0.001 and 0.2, during a period of at least 12 hrs, wherein: ##EQU2## S.sub.c being : percentage of solids in crystalliser at crystallisation temperature; S.sub.E being : percentage of solids after stabilisation for 48 hours at exit temperature of the crystalliser.
So in order to measure S.sub.E a sample is taken from the crystalliser at time is 0 hrs and kept for 48 hrs at final crystalliser temperature without stirring. At time t=48 hours the percentage of solids in the sample is measured by NMR-pulse. For the measurement of S.sub.C the solids are measured in the crystalliser immediately before material is taken out for pressing. Time t=0 hrs is taken as the point in time where for the first time material is taken from the crystalliser for pressing. If S.sub.C and S.sub.E are very close it can be, that the values obtained (due to experimental inaccuracy) are such, that S.sub.E <S.sub.C, so that .sigma. is negative. ##EQU3##


DESCRIPTION OF PREFERRED EMBODIMENTS

Above process according to our invention is conducted in such a way, that the system is always close to its equilibrium, therefore high levels of the more kinetically stable crystal form are obtained. The process is best achieved by performing a very slow stirring during the crystallisation step. Consequently the crystals are easier to filter and an optimal production in high yields and high separation efficiency can be achieved.
Kinetically stable crystal form being defined as any crystal form that at the process-conditions at steady-state does not change substantially during the process and thus may include the thermodynamically stable crystalform.
Another advantage is obtained by applying our novel process on polymorphic fats. The fats obtained according to our novel process do contain more of the stable .beta.-crystals, than the products of the conventional processes (which contain far more .beta..sup.1 -crystals) . Polymorphic fats being defined as fats, that can crystallise in different crystal-forms.
The above-mentioned process can be run as a pseudo-steady state process for more than 24 hours, preferably for more than 48 hours, while even a period of more than 60 hours can be achieved.
For the above-mentioned process to be carried out, a minimum residence time (.tau.) of the fat in the crystalliser should be maintained. Suitable residence times are .tau. of more than 1 hour, preferably more than 4 hours and more preferably m

REFERENCES:
patent: 4161484 (1979-07-01), Hendrikus
Whittam et al: "Etude microscopique dy vieillissement de la tripalmitine", Revue Francaise Des Corps Gras, vol. 21, No. 11, 1974 Paris Fr., pp. 605-610.

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