Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1994-09-06
1996-12-03
Kunz, Gary L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536112, C07H 100, C07H 1304
Patent
active
055809669
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of polyol fatty acid polyesters wherein a reaction mixture of a polyol and/or fatty acid oligoesters thereof, a fatty acid lower alkyl ester, a transesterification catalyst and an alkali metal soap emulsifier is caused to react under transesterification conditions and the alkali metal soap level is reduced during the transesterification reaction.
By "polyol" is meant any aliphatic or aromatic compound which comprises at least four free hydroxyl groups. In particular such polyols include the group of sugar polyols, which comprise the sugars, i.e. the mono-, di- and polysaccharides, the corresponding sugar alcohols and the derivatives thereof having at least four free hydroxyl groups. Examples of sugar polyols include glucose, mannose, galactose, xylose, fructose, sorbose, tagatose, ribulose, xylulose, lactose, maltose, raffinose, cellobiose, sucrose, erythritol, mannitol, lactitol, sorbitol, xylitol and .alpha.-methylglucoside. A preferred sugar polyol is sucrose.
In this specification by "polyol fatty acid polyester" is meant any such polyesters or mixtures thereof having a degree of conversion of at least 80%, in particular at least 90%. The degree of conversion is defined as the percentage of polyol hydroxyl groups of the polyol fatty acid polyester that on an average have been esterified with fatty acids. Thus a degree of conversion of 100 % corresponds to the fully esterified polyol.
In this specification by "fatty acid" are meant C.sub.8 -C.sub.24 fatty acids which may be saturated or unsaturated, and may have straight or branched alkyl chains.
The polyol fatty acid polyesters are known to be suitable low-calorie fat-replacers in edible products. They are substantially indigestible for human beings while they have physical and organoleptic properties very similar to triglyceride oils and fats conventionally used in edible products. Polyol fatty acid polyesters are further reported to have use as pharmaceutical agents in view of their ability to absorb fat-soluble substances, such as in particular cholesterol, in the gastrointestinal tract, and remove these substances from the human body.
In general polyol fatty acid polyesters are synthesized by a process in which a polyol, such as a mono- or disaccharide, is reacted with a fatty acid lower alkyl ester, often the fatty acid methyl ester, in the presence of a transesterification catalyst, such as e.g. an alkali metal hydroxide or carbonate. In a first stage a polyol fatty acid mono- or oligoester is formed, which in a second stage or further stages is reacted to form polyesters of the desired degree of conversion. Under certain conditions the two stages of the reaction can be combined into a single reaction.
Processes of this type are described e.g. in U.S. Pat. No. 3,963,699, U.S. Pat. No. 4,517,360, U.S. Pat. No. 4,518,772, EP-A-254376, EP-A-256585 and EP-A-301634.
An often necessary component in the initially heterogeneous reaction mixture, also referred to as "premix", is an emulsifying or dispersing agent, such as in particular an alkali metal soap. Although it is essential in the initial phase of the transesterification reaction, soap causes a number of problems towards the end of the reaction, in particular when the reaction is carried out on a technical scale. A major problem is that with increasing degrees of conversion to polyester, soap tends to separate out resulting in a high viscosity of the reaction mixture and consequently poor mixing, slow release of the lower alkyl alcohol and therefore prolonged reaction times. A further problem connected to the separating out of the soap emulsifier is that of soap deposition on equipment parts, such as the reaction vessel.
Removal of the soap emulsifier from the crude fully converted (.gtoreq.90%) reaction mixture is a laborious and costly step because of the large amounts of expensive chemicals used, such as phosphoric acid or citric acid. Moreover, the soap removal is largely responsible for the effluent produced during the refining of
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patent: 3963699 (1976-06-01), Rizzi et al.
patent: 4517360 (1985-05-01), Volpenhein
patent: 4973682 (1990-11-01), Willemse
patent: 5043438 (1991-08-01), Buter
WO,A,9 204 360--Mar. 19, 1992--see p. 15, line 3--p. 16, line 10.
Barmentlo Bart
Buter Markus G.
Eicken Ulrich
Kunz Gary L.
Unilever Patent Holdings B.V.
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