Disclosed is a composition comprising a mixture of acylated diesters of dl-malic acid corresponding to the formula: ##STR1## where P is palmityl and S is stearyl.

BACKGROUND OF THE INVENTION 
The present invention relates to edible fat mimetic materials which are 
solid at room temperature and have melting properties similar to those of 
natural cocoa butter. 
It is known that over 70% of cocoa butter triglycerides have the structure: 
##STR2## 
and that most of the remainder are other palmitate, stearate and oleate 
combinations. 
German Offenlegungschrift Patent No. 28 06 804, published Aug. 23, 1979 
discloses lipase inhibitory properties for certain fatty acyl 
hydroxydiacid diesters. 
U.S. Pat. No. 4,830,787 discloses fat mimetic materials which are esters of 
two or more fatty alcohols and at least one fatty acid with 
hydroxycarboxylic acids. More particularly, this patent discloses fat 
mimetic compounds of the formula: 
##STR3## 
where R' is an aliphatic group containing 4 to 30 carbons and the R' 
groups, which can be the same or different, are adapted to provide a 
perceptible fat-like character. In this patent there is expressed a 
preference for products with melting points below about 98.degree. F. 
(particularly those with relatively sharp melting points of from about 
90.degree. to 98.degree. F.) because such materials provide a mouth feel 
similar to that of natural fats and oils. The various examples in U.S. 
Pat. No. 4,830,787 and WO Patent No. 89/01293 which is related thereto, 
describe the preparation of materials which are oily liquids similar to 
vegetable oil. 
It is an object of the present invention to provide a fat mimetic material 
having crystallization and melting characteristics similar to those of 
good quality cocoa butter. Preferably, this material will have a melting 
range within 30.degree. to 39.degree. C. as determined by the method 
described later in this specification. 
SUMMARY OF THE INVENTION 
Disclosed is a composition of matter comprising a mixture of compounds 
corresponding to the formula: 
##STR4## 
wherein P is palmityl and S is stearyl and the ratio of P to S in the 
mixture is such that the composition is solid at normal room temperature 
and has melting characteristics which mimic those of natural cocoa butter. 
Also disclosed is a method for the preparation of this composition. 
DESCRIPTION OF THE INVENTION 
The composition which is the subject matter of the present invention is 
prepared by a two step procedure: 
step (1) 
##EQU1## 
step (2) 
##EQU2## 
Typically the palmityl-stearyl dl-malate diester mixture is prepared by 
reacting dl-malic acid with a 50/50 mixture of 1-hexadecanol and 
1-octadecanol. The products of this reaction are then converted to the 
structured fat analogue by oleoylation of the hydroxyl function. 
Step 1 is carried out neat or in a suitable solvent, e.g. methanol in which 
the esterification proceeds partially through temporarily formed methyl 
esters. The reaction proceeds well at ambient pressure and at the reflux 
temperature of methanol. Methanol is then displaced and removed from the 
system by stripping with temperatures up to 80.degree. and pressure down 
to 5 mm Hg. The dl-malate diester is recovered, such as by 
crystallization, and dissolved in a solvent suitable for the oleoylation 
reaction, e.g. pyridine or dichloromethane with triethylamine. Oleoylation 
preferably is accomplished by acylation with oleoyl chloride although 
oleoyl anhydride can also be used. 
Compositions were prepared using 1-hexadecanol and 1-octadecanol separately 
to provide palmityl/oleolyl/palmityl and stearyl/oleolyl/stearyl dl-malic 
acyl diesters, a one to one mixture of which was found to have a melting 
range of 41.0.degree. to 42.3.degree. C. Surprisingly, it was discovered 
that by mixing 1-hexadecanol and 1-octadecanol in reaction (1) to form the 
malate diester, a composition having the desired melting range resulted. 
This was especially unexpected in view of the discovery that acyl diesters 
of tartronic acid, i.e. palmityl/oleoyl/palmityl tartronic, which were 
expected to have melting properties most like cocoa butter, in fact, had 
melting points much too high to be of practical value for this 
application.

The method of practicing the present invention is further illustrated by 
the following examples: 
EXAMPLE I 
A. The palmityl/stearyl mixed diesters of dl-malic acid were prepared as 
follows 
Mixed 0.06 mole each of 1-hexadecanol (14.55 g) and 1-octadecanol (15.4 g) 
with 0.05 mole of dl-malic acid (6.7 g), 200 ml methanol, four "Chemfluor" 
boiling chips and 5 drops of methanesulfonic acid. Refluxed overnight. 
Stripped of methanol at partial vacuum for 4-5 hours/80.degree. C., 
stripped at 5 mm Hg vacuum for 8 hours. Dissolved in 400 ml warm hexane 
and decanted from boiling chips. Obtained a crystal crop by cooling to 
15.degree. to 20.degree. C. Filtered and washed with about 50 ml of cold 
hexane (about 5.degree. C.). A small amount of second crop of crystals was 
obtained by evaporation of the filtrate. TLC indicated that both products 
were mostly a single spot with a small amount of slower migrating spot and 
trace of yet slower spot. After recrystallization of the combined crops 
from 225 ml hexane at about 15.degree. C. and washing the filtered 
crystals with cold hexane, 16.79 g of purified material migrating as a 
single spot by TLC was obtained. GC and mass spec analysis was obtained 
and results were as follows: 
______________________________________ 
Wt % Molar % 
______________________________________ 
diplamityl 20.66 21.60 
1-palmityl, 4-stearyl 
50.60 50.73 
1-stearyl, 4-palmityl 
distearyl 28.74 27.68 
______________________________________ 
Nearly equal reactivities of the alcohols were indicated. Recovery by 
crystallization caused partial enrichment of the stearyl content in the 
recovered diester. 
B. The diester prepared in step A was oleoylated as follows 
Mixed malate diester (16.0 g) was dissolved in 160 ml of pyridine. Oleoyl 
chloride, purified by vacuum distillation of practical grade (9.52 g), was 
added slowly with stirring in one portion. Stirring was continued 64 
hours. Water (50 ml) was added and stirred a few hours to quench any 
unreacted acyl chloride. Hexane (400 ml) was added and the hexane solution 
was washed with twelve to fifteen portions of warm water (about 400 ml). 
The hexane solution was dehydrated with anhydrous MgSO.sub.4 and filtered. 
Hexane was evaporated under vacuum and 24.08 g dry material free of 
pyridine odor was obtained. Hexane (100 ml) was added and the resulting 
solution (133 ml) was free of crystallization of any kind (product or 
impurity) after standing several days. 
The product was purified by flash chromatography on mix of 50 g 230-400 
mesh and 130 g 70-270 mesh silica gel (60.ANG., Aldrich) using 
hexane:ethyl acetate mixtures from 100:1 to 100:2 for elution. Two 
applications were made: (1) 18.0 g of the initial material in 100 ml 
hexane solution, and (2) 14.5 g comprised of 8.5 g partially purified 
fractions from the first application combined with 6 g remaining initial 
material in total 83 ml solution with hexane. A total of 7.08 g of final 
purified acyl diester was obtained by vacuum stripping of solvent at up to 
80.degree. C. This material gave a single spot by TLC on silica gel with 
50:3 hexane:ethyl acetate irrigant and iodine/iodide/sulfuric acid 
detection. 
C. The melting properties of the material prepared as described above were 
determined as follows 
Melting point specimen slides were prepared by smearing (1) or melting (2) 
small portions of the acyl diester on 1.times.11/2" glass slides and 
covering with a thin glass cover slip. Melting properties were observed by 
PLM (polarized light microscopy) with a microscope fitted with crossed 
polarizer filters. The slides were aged at room temperature (20.degree. to 
25.degree. C.) for several days to ensure transition to higher melting 
polymorphic forms. The slides were clipped on to a temperature controlled 
holder (Sensortek model TS-4ER thermal microscope stage) capable of 
control between -20.degree. and +60.degree. C. at 0.1.degree. resolution. 
Temperature is sensed at the stage and rapid control is obtained by 
piezoelectric effect. Transfer of heat to the slide preparation is at a 
metal/glass surface contact interface which is relatively efficient. The 
slide preparation temperature will slightly lag the set temperature when 
heating or cooling the slide above or below ambient temperature. After the 
sample melts, the temperature is increased another 10.degree. C. for about 
20 seconds and then rapidly cooled to obtain a quickly frozen crystal 
morphology which is observed for melting behavior as was the original, 
aged preparation. 
A reference material (1-tetradecanol, 97%) was used to compare this method 
of melting point determination to capillary tube observation procedure 
using a digital melting point apparatus (Electrothermal, Model 8101). 
The average melting ranges for these replicate runs were: 
______________________________________ 
Capillary Method 
PLM Method 
______________________________________ 
37.3-39.0.degree. C. 
35.5-39.2.degree. C. 
______________________________________ 
A bias toward broadening the melting range is obtained with the PLM method. 
This is the case because observation of small details is much easier with 
the high magnification (typically 100.times.) and so onset of any liquid 
formation is generally observed sooner at a lower temperature. Likewise, 
last remnants of remaining crystals are easily seen and may require 
further temperature increase to complete melting. 
Cocoa butter is a polymorphic material which can exist in different 
crystalline forms. When used in confection coatings, it is desirable that 
the most stable, highest melting crystalline forms predominate. To achieve 
this goal, the preparation containing cocoa butter is kept at a 
temperature at which a small amount of the stable desired crystal form can 
exist. This will be near the high end of its total melting range. After 
the confection is formed and set by cooling, a gradual temperature 
increase may be necessary to allow undesired low melting crystalline forms 
to change into the more stable forms. A desirable mimetic for cocoa butter 
should have crystalline characteristics similar to cocoa butter for 
maximum compatibility. It should also have a melting range similar to, but 
not wider than, that of cocoa butter so that problems with crystallization 
will not be increased. It is also desirable that its setting temperature 
not be lower than that of cocoa butter to provide rapid confection 
formation. 
By the PLM method progression of the melting of cocoa butter is indicated 
initially by liquid formation resulting in a wetted appearance of some of 
the crystals present. Next, actual flow of liquid carrying with it 
observable crystals occurs. Finally complete disappearance of bright 
crystals results in a plain dark field with no bright spots. 
The following individual observations were made using slide specimens 
prepared from the material prepared in Example I and natural cocoa butter. 
__________________________________________________________________________ 
Quickly Refrozen 
Melting Range Melting 
(.degree.C.) (.degree.C.) 
__________________________________________________________________________ 
Melt Specimens 
(1) 38.7 - 39.3 29.2 
(2) 38.6 29.4 
Smear Specimens 
(1) 31.6 (partial flow) - 38.7 
28 - 29.1 
(2) 32.2 (partial melt) - 36.7 
27.4 - 28.7 
(3) 31.0 (partial flow) - 37.0 
28.8 - 29.1 
Slide specimens prepared from a fresh sample of good quality cocoa 
butter 
(Ambrosia Chocolate Co.) 
Melt Specimens 
(1) 30 (start) - 33.5 (flow) - 41.2 (most*) 
27.1 
(2) 31 (start) - 33.4 (flow) - 38.4 (most) 
27.6 
Smear Specimens 
(1) 33.1 (start) - 34.9 (flow) - 37.9 (most) 
24.3 - 27.7 
(2) 32.6 (start) - 33.5 (flow) - 38.4 (most) 
23.8 - 29.7 
(3) 32.4 (start) - 33.8 (flow) - 37.4 (most) 
24.5 - 27.7 
__________________________________________________________________________ 
*"Most" indicates that almost all material is melted although some 
crystals, estimated to be less than 1% of the total material, remain. 
Very small amounts of both types of cocoa butter specimen remained unmelted 
until temperatures as high as 63.degree. C. Similar polymorph melting was 
observed by quick cooling the completely melted specimen and rapidly 
determining its melting range. 
From the above data, it can be concluded that crystallizing and melting 
characteristics very similar to those of natural cocoa butter were 
obtained. 
EXAMPLE II 
Preparation of 50/50 mixture of dipalmitoyloleoyl dl-malate and 
distearyl-oleolyl dl-malate 
A. Dihexadecyl dl-malate 
1-Hexadecanol (87.4 g, 0.36 mole), dl-malic acid (20.1 g, 0.15 mole), 
methanol (600 ml), methane sulfonic acid (15 drops) and several 
"Chemfluor" boiling chips were placed in a 1000-ml round-bottomed flask. 
The mixture was refluxed for 16 hours. Most of the methanol was stripped 
from the mixture at a pressure of about 250 mm Hg. Stripping was then 
continued at 5 mm Hg and 80.degree. C. for 6 hours. Final weight was 
104.41 g. TLC indicated the composition was about 5:3:2 dihexadecyl ester: 
methyl hexadecyl ester: hexadecanol. Hexane (500 ml) was added and warmed 
to dissolve all solids. On slow cooling to about 22.degree. C., a first 
crystalline crop of 38.91 g was obtained after filtration. By further 
cooling to about 17.degree. C., a second crystalline crop of 27.21 g was 
obtained. Residuals of 37.81 g were reserved for recycle. Both crystal 
crops contained considerable impurity; the second crop, about 50%. 
Recrystallization from hexane gave material which migrated as a single 
spot during TLC (80:18:2:2 hexane: ethyl acetate:1-butanol: formic acid 
irrigant, silica gel plates). This recrystallized product melted at 
61.4.degree.-62.7.degree. C. 
B. Acylation of dihexadecyl dl-malate with oleoyl chloride 
Dihexadecyl dl-malate (91.6 g., 0.157 mole), triethylamine (20.9 g., 0.207 
mole), and dichloromethane (500 ml) were placed in a 1000-ml 
round-bottomed flask and stirred at 20.degree. C. Oleoyl chloride (tech. 
75%, 69.4 g, 0.173 mole, assuming no other acyl chloride in the 25% 
remainder of composition) was added over 5 minutes. A mild exotherm to 
35.degree. C. occurred. The mixture was stirred for 64 hours and filtered 
to remove triethylamine hydrochloride. Dichloromethane was stripped at 
temperatures up to 75.degree. C. and pressures as low as 5 mm Hg. Crude 
product weighing 171.4 g. was obtained vs. a theoretical weight of 155.2 
g. Excess weight arises from excess acid chloride and impurities therein. 
C. HPLC Purification of palmityl/oleoyl/palmityl dl-malate 
Preparatory HPLC was performed on a Waters "Prep LC/System 500A" using four 
5.7 cm.times.30 cm "Porasil" column cartridges in series. "Porasil" is 
silica gel of 55-105.mu. particle size, 120 .ANG. pore size. 
The columns were equilibrated with 100:1.5 hexane: ethyl acetate, and this 
solvent mix used throughout. An injection of 35 g crude product dissolved 
in 150 ml of solvent mix was about maximum capacity. Injection and elution 
flow rate was 150 ml/minute. Fractions were monitored by refractive index 
and TLC. A typical run resulted in 67% pure product, 28.7% recyclable 
impure product, and 4.1% impurity left on the column. When "on column" 
impurity started to contaminate product fractions, the columns were 
flushed with 200 ml of ethyl acetate, which removed column contaminants. 
D. Stearyl/oleoyl/stearyl dl-malate was prepared in a similar manner 
A 50/50, wt/wt mixture of the POP and SOS dl-malates was prepared by mixing 
of their melts. 
The melting point characteristics of the materials prepared in this 
experiment are set out in TABLE I. 
TABLE I 
______________________________________ 
Quick Freeze 
MP (.degree.C.) of 
Structure Crystal MP, .degree.C. 
Tempered Material 
______________________________________ 
POP dl-malate 
20.5-22.5 39.8-41.7 
SOS dl-malate 
37-39 37.7-43.8 
POP/SOS dl-malate 
34.3 41.0-42.3 
______________________________________ 
Mixtures were made in other proportions without success in lowering the 
melting point below that of the POP dl-malate alone. 
EXAMPLE III 
To obtain about 1 pound of material for more complete evaluation of its 
physical properties, the following synthesis and purification were 
performed. 
Mixed Palmityl/Stearyl Diester of dl-malic Acid 
One mole of palmityl alcohol (1-hexadecanol, 95%, Aldrich, 242.45 g) was 
combined with one mole stearyl alcohol (1-octadecanol, 95%, Aldrich, 270.5 
g) and 0.8 mole dl-malic acid (99%, Aldrich, 107.27 g) and one liter of 
methanol. Fifty drops methanesulfonic acid and a few "Chemfluor" boiling 
chips were added and the mixture refluxed overnight. Methanol was removed 
under partial vacuum, then full aspirator vacuum stripped for 12 hours at 
about 80.degree. C. The mixture was dissolved in warm hexane and upon 
cooling obtained crystal crops totaling about 300 g. 
The mother liquor was evaporated free of hexane and further reacted with 
additional alcohol and acid without methanol. A half mole each of the two 
alcohols and dl-malic acid were added. Methane sulfonic acid (25 drops) 
was added and when heated under vacuum, the dl-malic acid became 
solubilized in the mixture within a couple hours. Full aspirator vacuum 
stripping (.apprxeq.261/2 in Hg gauge) was continued for 12 hours. Crystal 
crops were obtained from warm hexane solution of the mixture as before. 
Further recrystallization included sodium carbonate treatment of the 
solutions in hexane or dichloromethane to remove any residual methane 
sulfonic acid catalyst. Final material going into two acylation batches 
contained some impurities estimated by TLC to be 2 to 4% fatty alcohols 
and about 0.5% of a lesser migrating spot material and 0.5% of substance 
remaining at the origin. The total crystal weight obtained was 405.45 g in 
two portions representing 51% of theoretical recoverable. Mother liquors 
were abandoned. GC assays of the two portions of diester gave the 
following proportions of dipalmityl:palmityl stearyl plus stearyl 
palmityl:distearyl weight ratios: 
EQU 1st portion 1:2.44:1.31 
EQU 2nd portion 1:3.34:2.27 
These compare to 1:2.45:1.39 obtained on the small batch reported 
previously (Example I). The greater stearyl content of the 2nd portion is 
believed to be the result of the additional crystallization which was 
needed for comparable purity of the diester which crystallization resulted 
in enrichment of the stearyl content. The desired proportion of palmityl 
and stearyl content will depend on obtainable knowledge from variations 
made in preparation and resulting properties of the product. Many 
properties secondary to melting range and crystalline form such as 
compatibility with other confectionary ingredients and ease of manufacture 
may require definite proportion ranges. 
Oleoylation of Diester 
Oleoylation was accomplished in two batches: In the first batch 0.314 mole 
of diester (192 g) was dissolved in 1110 g dichloromethane and 0.414 mole 
triethylamine (42 g) was added. Oleoyl chloride (70%, Aldrich) was added 
slowly over a fifteen to twenty minute period while a cool water bath was 
applied. A total of 148.2 g (0.345 mole minimum) was used. Temperature did 
not exceed 31.degree. C. Molar ratio was 1:1.1:1.32 diester:acyl 
chloride:amine. After mixing four hours, the mixture was filtered to 
remove triethylamine hydrochloride and stripped of dichloromethane. Hexane 
(400 ml) was added and the solution slurried with about 200 ml water a few 
hours. 
The second batch was done in like manner using 0.342 mole diester and 
corresponding amount of other reagents. The hexane solutions were combined 
and washed several times with warm water. Water remaining emulsified was 
removed by addition of magnesium sulfate (220 g) resulting in easily 
separable aqueous layer and crystals. 
The final hexane solution (1169.8 g) contained 56% residue on evaporation 
representing 655 g crude product. Theoretical recovery of 0.656 
mole.times.875.5 MW=574.3 g. The excess is readily accounted for by oleoyl 
chloride impurity and excess. 
Purification of Acyl diester 
The crude acyl di-ester solution in hexane was applied to prep HPLC in 30 g 
(solids) portions on the Waters prep LC/system 500A with 4-500 ml prep pak 
500 silica (55-105 .mu.m, 100.ANG.) cartridges in series. Elution was with 
1.6% ethyl acetate in hexane. Purges of 250 ml ethyl acetate were applied 
to the columns after every two runs. Twenty-two injections were made 
followed by four injections of recyclable fractions. A total of 450 g 
(17.3 g/run) purified analogue was obtained (78.4% of theory from 
acylation) and some recyclable fractions were abandoned. A small amount of 
impurity remained which is indicated by TLC with 50:3 hexane:ethyl acetate 
as remaining at the origin. 
This impurity was reduced somewhat but not eliminated (estimate content at 
about 0.5%) by batch (10 g) and column (60 g) treatment with Kieselgel 60 
G (EM Science). After treatment, 430 g of the acyl diester was obtained 
for further evaluation. 
Melting Data 
Smear slide preparations were observed for melting characteristics 40 hours 
after batching. Two types of crystal were observed. The lower melting form 
consisted of very fine crystals appearing translucent (crossed 
polarizers). The higher melting form (assumed to be the highest melting 
polymorph) appeared to be much brighter. Observed melting of three 
duplicates were: 
______________________________________ 
35.4 (flow) - 38.1.degree. C. 
33.7 (lessened - 37.5 (flow) - 38.3.degree. C. 
translucence) 
34.2 (lessened - 36.7 (flow) - 38.7.degree. C. 
translucence) 
______________________________________ 
Quickly frozen complete melts of the above gave other crystalline forms 
with the following melting ranges: 
EQU 26.6.degree.-29.0.degree. C. 
EQU 26.3.degree.-29.4.degree. C. 
EQU 27.3.degree.-28.9.degree. C. 
These melting characteristics are very similar to those reported previously 
on the 7 g batch first recovered.