GB2123024A

GB2123024A - Antioxidant synergists

Info

Publication number: GB2123024A
Application number: GB08317095A
Authority: GB
Inventors: Betram James Frank Hudson
Original assignee: Cadbury Schweppes Ltd
Current assignee: Mondelez UK Holdings and Services Ltd
Priority date: 1982-06-23
Filing date: 1983-06-23
Publication date: 1984-01-25
Also published as: GB2123024B; GB8317095D0

Abstract

Phosphatidic acids (that is phosphorylation products of mono- and/or di- glycerides) or salts thereof are used, as anti-oxidant synergists, in combination with primary antioxidants in the stabilisation of unsaturated organic materials susceptible to oxidation. In one embodiment a primary antioxidant is added, together with a phosphatidic acid or salt thereof to the material to be stabilised, e.g. lard or tallow. In accordance with another embodiment the phosphatidic acid is added to a fat or oil containing a natural primary antioxidant, e.g. refined palm oil or soyabean oil. In a further embodiment a phosphatidic acid salt is added to a natural fat or oil (other than cocoa butter in chocolate), for instance palmitic acid, containing a primary antioxidant, which may be natural. The invention also provides a stabilising composition comprising a primary antioxidant together with phosphatidic acid or salt thereof, as antioxidant synergist.

Description

SPECIFICATION Antioxidant synergists This invention is concerned with improvements in and relating to synergists or potentiators for use with antioxidant materials and to compositions containing them.

Many organic materials, especially those containing an ethylenically unsaturated aliphatic chain, are susceptible to degradation by oxidation, for example by atmospheric oxygen. Antioxidants are frequently added to such materials in order to prevent or inhibit their oxidation and a wide variety of such antioxidants have been proposed or are used in practice. The effectiveness of such antioxidants (hereinafter referred to as "primary antioxidants") may be improved by using them in combination with synergists or potentiators, that is compounds which, while having substantially no antioxidant activity of their own, serve to improve the antioxidant effect of the primary antioxidants.

It has now been found, in accordance with the present invention, that phosphatidic acids, or salts thereof, may be used as synergists with primary antioxidants to prevent or inhibit autoxidation of the materials.

Phosphatidic acids are phosphorylation products of mono or di- glycerides or mixtures thereof and contain a group of formula:

in which one of the groups X' and X2 represents a groupCOR (in which R represents a long chain of aliphatic group, e.g. containing from 8 to 22 carbon atoms, more commonly from 10 to 18 carbon atoms), and the other of X' and X2 represents a hydrogen atom, a group --COR or a arnuo

Particularly suitable phosphatidic acids for use in accordance with the invention may be represented by the formula::

in which R has the meaning defined above, X3 is a hydrogen atom or a group -CO-R, and R' is a hydrogen atom or a group -CH2-CH (0X)-CH2-O-CO-R, (in which X represents a hydrogen atom, a group --COR or a group

Examples of phosphatidic acids which may suitably be employed are mono- phosphatidic acids (formula (I); R'=H; X3=COR); lyso phosphatidic acids (formula (I); R'=H; X3=H); and bisphosphatidic acids (formula (I); R1=-CH2-CH (OCOR)-CH2-O-CO-R; X3--C0-R).

The phosphatidic acids may be prepared by the phosphorylation, e.g. using phosphorus pentoxide, of mono- or di- glycerides or mixtures thereof or containing them. Thus, depending upon the nature of the starting material and the conditions of phosphorylation the product obtained may comprise a mixture of products and may well contain other, more complex species than the species of formula (I) above.The products obtained may be defined to yield purer phosphatidic acids but it has been found that the mixtures themselves are applicable as antioxidant synergists and, as will be appreciated, it is often more convenient to use such mixtures, from an economic point of view, than the purified phosphatidic acids, The reaction mixtures obtained may also contain inactive species such as non-phosphorylated partial glycerides or triglycerides or triphosphatides; however the presence of these can generally be tolerated provided that the mixture contains at least some, generally at least 5% by weight, of the desired phosphatidic acids.

According to one embodiment of the invention, there is provided a method of stabilising an unsaturated organic material, susceptible to oxidation, against oxidation which comprises adding thereto a primary antioxidant and a phosphatidic acid or salt thereof as antioxidant synergist. The invention also provides an unsaturated organic material stabilised against oxidation containing a primary antioxidant and, as antioxidant synergist, one or more phosphatidic acids or salts thereof. Further, the invention provides an antioxidant composition comprising a primary antioxidant and a phosphatidic acid or salt thereof.

Certain natural materials, especially oils or fats of vegetable origin, contain natural primary antioxidants such as the tocopherols and in the case of such materials it may only be necessary to add a phosphatidic acid synergist to the fat or oil in order to obtain a product having an enhanced resistance to oxidation. In this connection, it may be noted that it has already been proposed (see British Patent Specification No. 1032465) to add materials obtained by the phosphorylation of mixtures containing mono- and di- glycerides and subsequent salification of the mixture obtained (thereby to obtain a mixture containing salts of phosphatidic acids) to chocolate as an emulsifier or emulsion stabiliser. There has been no suggestion that the phosphatidic acid salts so added act as antioxidant synergists.

Accordingly, another embodiment of the invention provides a process for improving the resistance to oxidation of a natural fat or oil containing natural primary antioxidant material which comprises adding a phosphatidic acid as antioxidant synergist, to the fat or oil. The invention also provides such a natural fat or oil to which a phosphatidic acid has been added as antioxidant synergist.

Further the invention provides a process for improving the resistance to oxidation of a natural fat or oil (other than cocoa butter in chocolate) containing natural primary antioxidant material which comprises adding a phosphatidic acid salt, as antioxidant synergist, to the fat or oil. The invention also provides the product of such process.

In addition to being synergists for primary antioxidants the phosphatidic acids or salts thereof have the important property of being soluble in or miscible with fats or oils and thus their incorporation in fatty or oily composition is readily accomplished.

In general it is preferred to use the phosphatidic acids in unsalified form, i.e. as the free acids, but where they are employed in salified form they may be employed, for example, as alkali metal, e.g. sodium or potassium or ammonium salts.

Where, as will generally be the case, the phosphatidic acid or salt is added together with a primary antioxidant, a wide variety of primary antioxidants may be employed.

As noted above, a composition stabilized in accordance with the invention may contain a naturally occurring primary antioxidant or have added thereto a primary antioxidant of natural or synthetic origin. Natural primary antioxidants (or their synthetic equivalents) include tocopherols (which are present in all vegetable oils and fats); tocotrienols (which are present in some vegetable oils and fats); polyphenols and derivatives thereof such as quercetin and gallic acid; and other phenolic substances such as sesamol, carnusic acid and ferulic acid. Such antioxidants may be present in the form of their esters or glycosides.

Synthetic antioxidants include phenolic compounds such as butyiated hydroxy-anisole (BHA), butylated hydroxy-toluene (BHT), tert.

butyl hydroquinone (TBHQ) and the propyl, octyl and dodecyl esters of gallic acid. Non-phenolic antioxidants include, for example, ascorbic acid, ascorbyl palmitate and thiodipropionic acid.

Other antioxidants, which are not in general suitable for use in foodstuffs include amines such as ethoxyquin. Antioxidants and their role in the preservation of foodstuffs are discussed in, for example, "A Review of the Technological Efficacy of some Antioxidants and Synergists", W. H. O.

Food Additives Series, No. 3, World Health Organisation, Geneva, 1972; and chapter 1 7-22 in the book "Antioxidation in Food and Biological Systems", M. G. Simil and M. Karel (Ed.) Plenum Press, London and New York, 1980.

The primary antioxidant will be incorporated in the material to be stabilised in conventional amounts used for that antioxidant. As is known, if an antioxidant is added in too great a quantity it loses it effectiveness and can, indeed, serve as an oxidant material. Thus, the primary antioxidant is, for example, suitably added to the material in an amount of from 0.001 to 1% by weight, preferably from 0.01 to 0.1% by weight, most preferably from 0.01 to 0.03% by weight. The phosphatidic acids or salts thereof are suitably added in similar amounts e.g. in amounts of up to 2% by weight, preferably from 0.2 to 1.04% by weight, more preferably from 0.2 to 0.6% by weight.

The combination of primary antioxidant and phosphatidic acid or salt thereof used in accordance with the invention may be used to stabilise a wide variety of organic materials such as oils or fats of vegetable or animal origin, fatty acids, waxes, lubricants and emulsifiers. The particular primary antioxidant synergist combinations of the invention are particularly useful for stabilising fats or oils for use in foodstuffs or in the preparation thereof and thus, for example, may be used to stabilise such fats or oils as lard, palm oil, soy bean oil, beef or mutton tallow, butter oil, rapeseed oil, cottonseed oil, groundnut oil, and sunflower oil; fatty acids such as stearines and oleines; derivatives of fatty acids such as emulsifiers, for example mono- and diglycerides of mixed fatty acids; and processed e.g.

hydrogenated, oils, fats or fatty acids.

In order that the invention may be well understood therollowing Examples are given by way of illustration only.

In examples 3 and 4 there were used as test materials refined palm oil and refined soyabean oil respectively. Both of these are materials which contain natural primary anti-oxidants; palm oil typically containing from 0.03 to 0.05% by weight of alpha-tocopherol, together with alpha-tocotrienol, and about 0.04% by weight of gamma-tocophenol and gamma tocotrienoi; and soyabean oil typically containing about 0.01% by weight of alpha-tocopherol, about 0.05% by weight of gamma-tocopherol and about 0.02% by weight of delta-tocopherol.

Example 1 As determined by the rate of generation of volatile oxidation products on aeration at 1 000C, pure lard has an induction period of 1.4 hours.

which was not altered by the incorporation of 0.3% by weight of 1 :2-dipalmitoyl sn-glycerol phosphate (the synergist). The addition of 0.02% by weight of dl-a-tocophernl (the primary antioxidant) to lard extended the induction period to 21.8 hours. If, in addition to the primary antioxidant, 0.3% by weight of the synergist was also added to the pure lard the induction period further increased to 47.0 hours.

Example 2 Pure tallow showed an induction period of 1.45 hours on aeration at 1 200C. When 0.5% by weight of a mixture of ammonium phosphatides (defined in the Emulsifiers and Stabilisers in Food Regulations, S.l., 1980, No. 1833) was incorporated in the tallow, the induction period increased to 4.5 hours. The addition of 0.02% by weight of dl--tocopherol to tallow extended the induction period to 1 3.3 hours. If, in addition to the primary antioxidant, 0.5% by weight of the ammonium phosphatides were also added to tallow the induction period increased to 44.4 hours.

Example 3 Pure refined palm oil showed an induction period of 10.5 hours on aeration at 1200 C. When 0.5% by weight of a mixture of ammonium phosphatides (as defined in Example 2) was incorporated in the palm oil the induction period increased to 20.9 hours. At the end of the induction period the oil to which the synergist had been added was much paler than the untreated oil.

Example 4 A sample of refined soya bean oil in an active stage of autioxidation had a peroxide value of 25.0 and an unacceptable "oxidised" off-flavour.

On heating in open air, with agitation, at 1000C for one hour, the peroxide value rose to 26.4 and on standing for a further 20 hours at ambient temperature to 28.2. An identical sample of soya bean oil to which had been added 0.5% of the phosphatidic acids from which the aforementioned ammonium phosphatides were prepared was similarly treated. After one hour at 1000C the peroxide value fell to 22.5, and after a further 20 hours at ambient temperature it fell further, to 20.4, producing an oil in which the harsh "oxidised" flavour had been replaced by a slight, not unpleasant, "cucumbery" flavour.

Example 5 A sample of standard laboratory grade palmitic acid on aeration at 1 400C had an induction period of 0.25 hours. When 0.5% by weight of the aforementioned ammonium phosphatides were added to the palmitic acid, the induction period increased to 1.2 hours. When 0.02% of dl-a-toco- pherol was added to the palmitic acid the induction period recorded was 0.6 hours.

However, when both dl-cg-tocopherol (0.02% by weight) and the ammonium phosphatides (0.5% by weight) were added to the palmitic acid, the induction period increased to 27.5 hours.

Claims

1. A method of stabilising an unsaturated organic material susceptible to oxidation, against oxidation which method comprises adding to the unsaturated organic material a primary antioxidant together with, as antioxidant synergist, a phosphatidic acid or salt thereof.

2. A method for improving the resistance to oxidation of a fat or oil containing natural primary antioxidant material which comprises adding a phosphatidic acid, as antioxidant synergist, to the fat or oil.

3. A method for improving the resistance to oxidation of a natural fat or oil (other than cocoa butter in chocolate) containing natural or primary oxidant material which comprises adding a phosphatidic acid salt, as antioxidant synergist to the fat or oil.

4. A method as claimed in any one of the preceding claims in which the phosphatidic acid has the formula:

(in which R is a long chain aliphatic group), X3 is a hydrogen atom or a group -CO-R, and R' is a hydrogen atom or a group -CH2-CH (OX)-CH2-O-CO-R (in which X represents a hydrogen atom a group -COR or a group

5. A method as claimed in any one of the preceding claims in which the phosphatidic acid or salt thereof is added in an amount of up to 2% by weight, based on the weight of the material to be stabilised against oxidation.

6. A method of stabilising an unsaturated organic material against oxidation substantially as hereinbefore described with reference to the Examples.

7. Organic material stabilised against oxidation when obtained by a method as claimed in any one of the preceding claims.

8. A composition for stabilising ethylenically unsaturated material against oxidation comprising a primary antioxidant and, as antioxidant synergist, a phosphatidic acid or salt thereof.

9. A composition as claimed in claim 8 in which the phosphatidic acid is as defined in claim 4.