|Title of Invention||
PRODUCTION OF SUGAR ESTERS FROM VINYL FATTY ACID ESTERS
|Abstract||A process for manufacturing sucrose-fatty acid esters comprising the steps of: (a) dissolving sucrose in an organic solvent to form a sugar-solvent mixture; (b) mixing an alkali metal hydroxide and/or carbonate catalyst into the sugar solvent mixture; (c) mixing in a vinyl ester of a fatty acid; (d) reacting the resulting mixture at a temperature between 40 °C and 60 °C for five to fifteen minutes to yield a reaction product containing the organic solvent, the alkali metal hydroxide and/or carbonate catalyst, unreacted sugar, unreacted vinyl ester, sugar ester and acetaldehyde; (e) forming an emulsion by adding brine whereupon the unreacted sugar and the metal carbonate catalyst dissolve into the brine; (f) breaking the emulsion by adding an organic solvent after which phase separation occurs into an organic phase which contains crude sucrose fatty acid ester and unreacted vinyl ester; and (g) purifying the sucrose fatty acid ester from the organic phase.|
|Full Text||Cross-reference to Prior Applications
 This application is a non-provisional filing based on and claiming the benefit
and priority of Provisional Application No. 60/757097 filed on 06 January 2006.
U.S. Government Support
Background of the Invention
Area of the Art
 This invention relates to a process for producing sugar esters with high
efficiency and high purity.
Description of the Related Art
 Starting around the end of the Second World War "natural" surfactants such as
soaps (alkali metal salts of fatty acids) were increasingly replaced with petroleum-
derived "detergents." However, most of these materials were not suitable for use in
food and drug products. In the search for surfactants suitable for food and drug use the
sugar detergents or surfactants namely fatty acid esters of sugars and sugar
derivatives were discovered. Because of the relatively large number of natural sugars
and the variety of possible fatty acids, a very large number of different sugar
detergents are possible.
 Sugar esters can be classified both by the type of sugar and also by the chain
length of the fatty acid esterIfied to the sugar. Sucrose, glucose, maltose and other
sugars have been reacted with a variety of fatty acids including stearic acid (18
carbons), oleic acid (18 carbons), palmitic acid (16 carbons), myristic acid (14 carbons)
and lauric acid (12 carbons). Sucrose esters are surfactants or emulsifiers that have
several desirable properties for use In the food industry. These include the ability to
produce excellent emulsification of oils and water, anti-bacterial properties, freezing
damage protection of dough and baked breads, complex formation with starch, and
even preservation of fresh fruit. One of the advantages of sugar esters for these tasks
is that both the hydrophilic portion of the molecule (the sugar) and the lipophilic portion
of the molecule (the fatty acid) can be readily varied thus providing a wide variety of
different compounds each having slightly different properties.
 Probably the most common sugar detergents are those based on sucrose
(table sugar) which is actually a disaccharide consisting of one molecule of the six
carbon aldo-sugar glucose linked to a molecule of the five carbon keto-sugar fructose.
When sucrose and fatty acid are reacted to form an ester there are eight positions
(four on each of the constituent sugars) on the sucrose molecule where the fatty acid
can be esterified. Typically, monoesters, diesters and triesters are formed with only a
small quantity of higher esters probably because of steric hindrance. When the
reaction is with a single fatty acid, such as lauric acid, analysis shows that there are
many different esters that form, typically 2-4 different monoesters and up to 6-8
different diesters. If fatty acid mixtures are used as starting materials, the products are
even more complex. It will readily be appreciated that the chain length (as well as
degree of saturation) of the fatty acid can have significant effects on the properties of
the resulting sugar ester. Longer chain fatty acids produce esters that are solid or
semi-solid at room temperature. Longer chain esters are also less readily soluble in
water. The hydrophilic properties of the amphiphilic surfactant molecules are largely
contributed by the sugar moiety while the hydrophobic properties are contributed by
the fatty acid moiety with longer chain length acids being increasingly hydrophobic.
 The United States Food and Drug Agency (FDA) has set standards for sugar
detergents in foods, drugs and cosmetics. The food additive standards are found at 21
CFR 172.859, pages 95-96. The standards set requirements for the composition of the
sucrose esters which must be 80% or more by weight of mono, di and tri esters
produced from edible fatty acids (animal fats and vegetable oils) with less than 5% by
weight free sucrose. In addition only "safe" organic solvents may be used in the
synthesis of the esters and the residue levels of these solvents are controlled by the
 Perhaps as a result of these standards, there are only a few commercial
sources of these materials that meet the Food and Drug Administration requirements.
The sugar esters have been produced in Japan for over 50 years so that several
Japanese companies, one being Ryoto Sugar Esters made by the Mitsubishl-Kasal
Food Company, make products meeting the FDA criteria.
 The classic method for the production of the sucrose esters is best illustrated
by the production of sucrose stearate. In the early processes dimethyl formamide
(DMF) was used as the solvent. The methyl ester of the fatty acid was made and this
methyl ester was reacted with sucrose in the DMF in the presence of a catalyst such
as potassium carbonate for 4-6 hours at 83-95.°C. Typical recipes (all are parts by
weight) used 30 to 127 parts sucrose to 30 parts methyl stearate, 2 parts potassium
carbonate and 300 parts solvent. These methods achieved high yields of 60-75% by
weight. The basic problem has been in purifying the reaction mixture to yield a material
that meets FDA standards especially since DMF is toxic. In addition, the reaction
products are highly viscous containing partially decomposed sugars and solvents.
 These problems led to a series of attempted improvements. Due to concerns
about the use of DMF, Foster D. Snell developed a new method using dimethyl
sulfoxide (DMSO) instead of DMF as disclosed in U.S. Pat. No. 3,480,616. Another
example is found in U.S. Pat. No. 3,644,333 to Osipow et al which tried to eliminate the
use of an organic solvent by using an emulsion. In this process, sucrose was mixed
with methyl stearate and sodium stearate and a significant amount of previously
prepared sucrose ester. Potassium carbonate was used as the catalyst, and water
was used as the solvent. However, the yields are low, on the order of 30-35% by
weight. Further, there are considerable waste and degraded products so that the
desired product was much more difficult to remove from the reaction mixture.
 Alternative methods have been described by Feuge. For example, in U.S. Pat.
No. 3,714,144, he uses the sodium, potassium or lithium soap of the fatty acid in a
molten sugar solution. The reaction proceeds for 2-20 minutes under vacuum at 170-
190°C. Again, the product is made in very low yield and the destroyed sugar and alkali
metals are very difficult to remove. To help with the production of the esters, several
schemes have been devised to purify the reaction mixtures. For example, Kea et al in
U.S. Pat. No. 4,710,567 teach the use of the addition of an aqueous salt solution to
help purify the ester followed by a three phase separation.
 A number of patents assigned to Dai-lchi Kogyo Seiyaku Co. Ltd. (Kyoto,
Japan) covering sucrose ester synthesis were granted between 1990 and 1991. In
particular, U.S. Pat. Nos. 4,898,935, 4,996,309, 4,995,911, 5,011,922, and 5,017,697
all disclose methods for reacting, extracting and purifying sucrose fatty acid esters as
produced using chemical catalysis.
 Summary of the Invention
 The present invention is a process for synthesizing sugar esters of fatty acids
using vinyl esters of fatty acids. By sugar we mean any of the naturally occurring
sugars found primarily in plant sources. These include, for example, sucrose, ribose,
mannose, glucose, fructose, xylose, arabinose, lactose, melibiose, galactose,
mannose, raffinose and cellobiose. Appropriate fatty acids are those found in edible
fats, waxes and oils—again primarily of vegetable origin. The useful fatty acids include,
for example, hexanoic, octanoic, decanoic, lauric, myristic, myristoletic, palmitic,
stearic, oleic, ricinoleic, linoleic, linolenic, arachidic, eicosenoic, behenic, and erucic
acids. The inventive process combines a solution of an appropriate sugar in an
appropriate organic solvent with a metal carbonate catalyst and a vinyl ester of a fatty
acid as an acyl source for esterification. Suitable organic solvents are those solvents
that show at least slight solubility of the sugar in question. In addition, because these
sugar esters may be destined for food use, only FDA approved solvents can be used.
Such solvents include dimethyl sulfoxide, methyl ethyl ketone, ethyl acetate, and
isobutanol (2-methyl-1-propanol). The vinyl ester sugar mixture is reacted at a
temperature between about 30°C and about 90°C for a time between about five
minutes and twenty four hours. During the reaction the fatty acid groups esterify the
sugar and acetaldehyde is released as a byproduct. Because acetaldehyde is
reasonably volatile, the reaction can advantageously be conducted under reduced
atmospheric pressure so that the acetaldehyde is removed from the reaction mixture,
thereby "pulling" the reaction forward. At the end of the reaction time the product is
primarily sugar monoester with a relatively low level of unconsumed vinyl ester if the
starting ratio of sugar to vinyl ester is between about 2:1 and about 8:1.
Detailed Description of the Invention.
 The following description is provided to enable any person skilled in the art to
make and use the invention and sets forth the best modes contemplated by the
inventor of carrying out his invention. Various modifications, however, will remain
readily apparent to those skilled in the art, since the general principles of the present
invention have been defined herein specifically to provide a method of producing
sucrose esters wherein the fatty acids are provided in the form of vinyl esters.
 Production of sucrose monostearate using vinyl esters of fatty acids
 Because sucrose monoesters are considered to be more valuable than the
other esters, the inventive reaction shown here has been optimized to produce the
highest monoester content instead of the highest reaction yield.
 Sucrose is first dissolved in DMSO at 60°C to a concentration of about 400
mM. To limit coloration of the reaction mixture, potassium carbonate is added to this
sucrose solution at an amount of 1.5g/L and stirred for about 30 min to activate the
sucrose molecules. After about 30 min, the undissolved potassium carbonate is
removed by either decanting or filtration and vinyl stearate is added such that its final
concentration is about 100 mM. With the addition of the vinyl fatty acid ester the
reaction begins and is allowed to proceed for about 15 min. The reaction can be
monitored by measuring the amount of remaining vinyl fatty acid ester. When this level
falls to no more than about 10% by weight of the starting amount, the reaction can be
considered to be complete. Using the above reaction conditions the monoester
content, measured as a percentage of total ester content, post reaction is about 90%,
and the calculated reaction yield based on vinyl stearate is about 90%. The acid value
post reaction is less than 1.
 Purification of sucrose monostearate
 The DMSO can be recovered from the reaction mixture by vacuum distillation.
Brine (sodium chloride) is added to the post distillation mixture to effect emulsification
of the sucrose stearate and vinyl stearate. The unreacted sucrose and potassium
carbonate dissolve in the brine solution. To recover the sucrose stearate, especially
sucrose monostearate, the emulsion is then broken by adding an organic solvent, for
example, isobutanol. The organic solvent separates from the aqueous brine to form
two separate liquid phases. One phase comprises organic solvent (isobutanol),
sucrose ester (stearate) and unreacted vinyl ester. The other phase comprises of
water, unreacted sucrose and potassium carbonate. After separation is complete, the
isobutanol phase is decanted from the aqueous layer and subjected to vacuum
distillation to recover the isobutanol. After the isobutanol is removed, the crude product
comprises of sucrose stearate, vinyl stearate and traces of sucrose. Spray drying of
the isobutanol product concentrate into supercritical carbon dioxide gave sucrose
stearate powder with around 500ppm DMSO. This powder can be dissolved in ethanol
again and subjected to two further sprays to reduce the DMSO content in the product
to less than 0.5ppm. In this way, the FDA purity criteria are met by the final sucrose
 Reaction variables
 Sucrose to vinyl ester ratio: Theoretically, higher sucrose to vinyl ester ratio
should yield higher monoester content. However, an exceedingly high ratio would
create downstream purification problems. Therefore, the optimal sucrose to vinyl ester
molar ratio is between about 2:1 to about 8:1.
 Catalyst: This reaction is catalyzed by bases. Suitable bases include metal
oxides, metal hydroxides and metal carbonates, in particularly alkali metal hydroxides
and carbonates. The higher the alkalinity of the metal hydroxides and carbonates, the
faster the reaction. Possible catalyst candidates include potassium hydroxide, sodium
hydroxide, potassium carbonate, sodium carbonate and lithium carbonate. Other
anions of weak acids that provide sufficient alkalinity are also useable.
 Catalyst concentration: It was found that excessive concentration of catalyst
leads to discoloration of the reaction mixture—probably due to side reactions.
Therefore, the optimum catalyst concentration lies between about 1.5 and about 6g/L
of total reaction volume with a potassium carbonate catalyst. When other alkali metals
and/or alternate metal salts are used, the catalyst concentration should be adjusted to
provide similar provide similar alkalinity.
 Reaction temperature: The byproduct of using a vinyl ester as the acyl donor
is acetaldehyde. Because acetaldehyde has a low boiling point, high reaction
temperature is not necessary to drive the reaction as is the case with conventional
methyl or ethyl esters. The minimum temperature for reasonable reaction rate is about
30°C. Although the reaction rate increases with increasing reaction temperature, high
reaction temperatures are not favored because they result in discoloration of the
reaction mixture, even at low catalyst concentration. A trade off between rate and
discoloration (side reactions) is reached at the moderate reaction temperatures of
between about 40°C and 60°C.
 The following claims are thus to be understood to include what is specifically
illustrated and described above, what is conceptually equivalent, what can be
obviously substituted and also what essentially incorporates the essential idea of the
invention. Those skilled in the art will appreciate that various adaptations and modifica-
tions of the just-described preferred embodiment can be configured without departing
from the scope of the invention. The illustrated embodiment has been set forth only for
the purposes of example and that should not be taken as limiting the invention.
Therefore, it is to be understood that, within the scope of the appended claims, the
invention may be practiced other than as specifically described herein.
1. A process for manufacturing sucrose-fatty acid esters comprising the
dissolving sucrose in an organic solvent selected from the group
consisting of dimethyl sulfoxide, methyl ethyl ketone, ethyl
acetate, and isobutanol to form a sugar-solvent mixture;
mixing an alkali metal hydroxide and/or carbonate catalyst into the
sugar solvent mixture;
mixing in a vinyl ester of a fatty acid;
reacting the resulting mixture at a temperature between 40 °C and
60 °C for five to fifteen minutes to yield a reaction product
containing the organic solvent, the alkali metal hydroxide and/or
carbonate catalyst, unreacted sugar, unreacted vinyl ester,
sugar ester and acetaldehyde;
forming an emulsion by adding brine whereupon the unreacted sugar
and the metal carbonate catalyst dissolve into the brine;
breaking the emulsion by adding an organic solvent after which phase
separation occurs into an organic phase which contains crude
sucrose fatty acid ester and unreacted vinyl ester; and
purifying the sucrose fatty acid ester from the organic phase.
2. The process as claimed in claim 1, wherein the vinyl ester of the fatty
acid is selected from the group consisting of vinyl esters of hexanoic, octanoic,
decanoic, lauric, myristic, myristoletic, palmitic, stearic, oleic, ricinoleic, linoleic,
linolenic, arachidic, eicosenoic, behenic, and erucic acids.
3. The process as claimed in claim 1, wherein said catalyst is selected
from the group consisting of sodium carbonate, potassium carbonate, lithium
carbonate, potassium hydroxide and sodium hydroxide.
4. The process as claimed in claim 1, wherein the sugar and the vinyl
ester are present at a molar ratio of between 2:1 and 8:1.
5. The process as claimed in claim 1, wherein the step of reacting occurs
at a temperature between 40 °C and 50 °C.
6. The process as claimed in claim 1 optionally comprising removing
acetaldehyde during the step of reacting.
7. The process as claimed in claim 1, wherein a level of the vinyl ester of
a fatty acid is monitored.
8. The process as claimed in claim 1 optionally comprising a step of
vacuum distillation to remove DMSO from the reaction product.
9. The process as claimed in claim 1 optionally comprising a step of
spray drying the organic phase into supercritical carbon dioxide to further purify the
crude sucrose fatty acid ester.
PRODUCTION OF SUGAR ESTERS FROM VINYL
FATTY ACID ESTERS
A process for manufacturing sucrose-fatty acid esters comprising the steps of: (a)
dissolving sucrose in an organic solvent to form a sugar-solvent mixture; (b) mixing
an alkali metal hydroxide and/or carbonate catalyst into the sugar solvent mixture; (c)
mixing in a vinyl ester of a fatty acid; (d) reacting the resulting mixture at a
temperature between 40 °C and 60 °C for five to fifteen minutes to yield a reaction
product containing the organic solvent, the alkali metal hydroxide and/or carbonate
catalyst, unreacted sugar, unreacted vinyl ester, sugar ester and acetaldehyde; (e)
forming an emulsion by adding brine whereupon the unreacted sugar and the metal
carbonate catalyst dissolve into the brine; (f) breaking the emulsion by adding an
organic solvent after which phase separation occurs into an organic phase which
contains crude sucrose fatty acid ester and unreacted vinyl ester; and (g) purifying
the sucrose fatty acid ester from the organic phase.
|Indian Patent Application Number||2994/KOLNP/2008|
|PG Journal Number||33/2012|
|Date of Filing||23-Jul-2008|
|Name of Patentee||COMSTOCK, BOB|
|Applicant Address||23 PRINCESS OF WALES ROAD SINGAPORE|
|PCT International Classification Number||C07H 1/00,C07H 13/06|
|PCT International Application Number||PCT/US2007/060140|
|PCT International Filing date||2007-01-05|