CA1294629C - Stabilization of lauric fats and oils - Google Patents

Abstract

ABSTRACT

An improved process for the treatment of lauric fats and oils to reduce or prevent both hydrolytic and oxidative rancidity comprising adding to said fat or oil a sequestering amount of citric acid, and with said citric acid lecithin in the amount of at least about 30 ppm (parts per million) based on the weight of the fat or oil.

Description

Sl~BII.IZATION OF LAr~RIC FAIS AND OILS

The present invention relates to the stabilization of lauric fats and oils, and more particularly to the prevention of both oxidative and hydrolytic rancidity in fats and oils.

BACKGROUND OF THE PRESENT INVENTION
_ .

When an oil becomes oxidized, it first develops hydroperoxides.
Hydroperoxides have no flavor or odor. However, they break down rapidly to form aldehydes, which have a strong, disagreeable flavor and odor. The overall flavor defect is called oxidative rancidity.

It is well known to subject fats and oils to final deodorization in the process of preparing them for commercial use. Deodorization is the process whereby odors and flavors of fats and oils are removed, usually by blowing steam through hot oil at 200-275C (392-527F) under low~pressure (3-10 Torr).

It is a desirable practice in deodorization, as a final step, to add citric acid to the oil. It is usually added as a water solution under vacuum, so that the water is evaporated off. The 6;~

citric acid functions as a metal scavenger, especially for traces of copper and iron which act as pro-oxidants for oil. If citric acid is not added, the oil can revert and oxidize more rapidly Hydrolytic rancidity is the reaction of triglycerides with water, to produce glycerin and free fatty acids. The reaction can be exemplified by the following equation:
C3H5(00CR)3+3HO~1 = C311s~OHj3 + 3HOOCR
Prior to deodorization~ fats and oils are usually subjected to alkali refining. Alkali refining is effective to achieve almost complete removal of free fatty acids. The free fatty acid content is determined by titration of a sample with a standard solution of sodium hydroxide (AOCS method Ca5a-40).

However, after refining, oil is often held in storage tanks. Water vapor can get into these tanks through breather pipes and oondense on cooling. The free fatty acid content can increase again because of the presence of such water. De~dorization, the final process before the fat or oil is packaged, lowers free fatty acid and water to about 0.05% or less. However, moisture in pipe lines, feed tanks, beading towers, and flaking rolls as well as ~ank wagons and cars, can again cause subsequent increase in moisture, in turn causing again an increase in free fatty acid content.

Lauric fats and oils, such as coconut oil and palm kernel oil, are particularly subject to hydrolytic rancidity. Hydrolysis of cooonut oil or palm kernel oil, even to a small extent, liberates shDrt-chain fatty acids, which are highly flavored and have a very disagreeable soapy flavor.

The problem with the presence of citric-acid in lauric fats and oils, when acco~panied by isture, is that the citric acid, in effect, can function as a catalyst in the hydrolysis reaction, causing an increase in percent free fatty acid. Work carried out in connection with the present invention has demonstrated that the rancidity occurred a-t a rate proportional to the level of citric acid present. The most stable fractionated palm kernel oil samples obtained other than by the present invention were those containing no citric acid and low levels o~ water (below 0001%).
As a result, citric acid is normally added only to dome-stic fats and oils, and not lauric fats and oils.
Lecithin is a well-known additive to fats and oils for a number of purposes, mostly involving emulsification or viscosity reduction. For instance, lecithin is used to reduce the viscosity o-E confectionery coatings, or as an emusifier in such products as ice cream, bread, icings, paints, cosmetics, printing inks, and the like. Also, it is known to have a synergistic action with phenolic antioxidants and may be used for this purpose. In such uses, the amount employed can be characterized as an emulsifying amount or antioxidant amount. By way of example, in confectionery products a reduction in viscosity is achieved by the addi~ion of about 001-0.4% lecithin, based on the weight of the coating.
It is also known to package lauric hard butters with about 0.1~ lecithin added as a moisture scavenger. This is said to reduce the potential of developing hydrolytic rancidity in a stored, deodorized fat. This disclosure can be found in the book "Food Oils and Their Uses", Second Edition, Theodore J. Weiss, The Avi Publishing Co., Inc. copyright 1983 (page 289).
Prior patent to Black, V.S. No. 2,494,114, issued 10 January, 1950 to Swift & Co. describes the stabilization of fatty materials by the addition of an antioxidant known as "NDGA"
(dihydroguaiaretic acid). The patent suggests that improved ~:

~ 73390-3 stabillzation against ran~idity produced by oxidation can be a~hieved by the use of lecithin or citric acid in combination with NDGA. One sample reporkecl in the patent contains all three ingredients, NDGA, .002% citric acidr and .03~ lecithin. However, the data given with regard to rancidity produced by oxidation (xancid in 80 days) was no better than that obtained by the use of NDGA and citric acid alone (also 80 days). The patent makes no mention of hydrolytic rancidity, nor the particular problems associated with lauric fats and oils.
Appli~ants know of no disclosure that teaches treatin~
lauric fats or oils with citric acid, to sequester traces of copper and iron, and then further adding lecithin for the purpose : of achieving substantially complete resistance to not only oxidative rancidity but also hydrolytic rancidity as well.
BRIEF DISCLOSURE OF THE PRESENT INVENTION
The present invention resides in an improved process for the treatment of lauric fats and oils to reduce or prevent both hydrolytic and oxidative rancidity comprising adding to said fat or oil a sequestering amount of citric acid, and with said citri~
acid, lecithin in an amount effective to provide at least 30ppm and not more than 250 ppm active phospholipids based on the weight of ~at or oil.
The present invention is par-ticularly applicable to deodorized lauric fats and oils.
It is necessary that the citric acid be added subsequent to final deodorization, as the acid can decompose at deodoriza-tion temperatures. The lecithin can be added prior to or after final 4a 73390-3 deodorization. If added before, ~he le~ithin is preferably free of phosphatidyl ethanolamine (PE~. Alternatively, the leci~hin can be pretrea~ed with a strongly basic compound following the procedure '~

~g~ 9 of Purves U.S. patent No. 4,528,201, issued 9 July, 1985 to Procter ~ Gamble Co..
DETAILED DESCRIPTION OF THE PRESENT INVENTION
For purposes of the present invention~ the term "lauric fats and oils" means specifically those Eats and oils having a high content of lauric acid (40-60%). They contain smaller amounts of saturated acids having 8, 10, 14, 16 and 18 carbon atoms. Their unsaturated acids are all minor in amount and con-sist of oleic and linoleic acid. Commercially important fats and oils in this group include palm kernel oil, coconut oil~ babassu oil and tucum oil.
It is understood that the present invention broadly is also applicable to blends of fats where part of the blend is a so-called domestic fat (e.g., non-lauric soybean or cottonseed), and part of the blend is a lauric fat or oil. Such blends are particularly common in the confectionery field and can comprise from 5 to 95~ lauric fat or oil. For purposes of the present application, the term "lauric" includes such blends.
The lauric fats and oils of the present invention are ~0 primarily those which have been subjected to conventional alkali refining, and bleaching with an absorptive clay or typical physi-cal refining processes. These steps are conventional in the art, and form no part of the present invention. In addition, the fats and oils of the present invention may be subjected to fractiona-tion, hydrogenation, acidolysis, interesteriEication or rearrange-ment. The fats and oil may be prepared by a direct esterifica-tion ~9462~
5a 73390-3 of Eatty acids and glycerine. A final step in the processing usually is deodorization. With regard to those fats or oils which are fractionated, the present invention is applicable to both the low melting point Eractions and the high mel-ting point fractions.
Typical uses for the fats and oils of the present inven-tion are ice cream coatings, confectionery coatings or fillings, whipped ~29~6Z9 toppings, hard butters, plastic shortenings, cocoa butter extenders, and stearines.

Not all lauric oil or fat products require stabilization by the present invention. By way of example, a well processed coconut oil which melts at about 76F has, under normal circumstances, good ~OM
(Active Oxygen Method) stability and citric acid may not be needed. The same is true for hydrogenated ooconut oil (mp 76-100F~ or hydrogenated palm kernel oil (mp 87-115F).

IIowever, the present invention could have g~od applicability in those instances where the coconut oil or palm kernel oil, whether or not hydrogenated, is likely to undergo iron pick-up during processing or storage, and be subject to oxidative rancidity. The addition of citric acid in such instances would be useful.
Applications for these products are ice creams and whipped toppings.

The present invention has been very advantageously used with a fractionated palm kernel or coconut oil having a Wiley Melting Point in the range of about 89-93F, or one that is also hydrogenated having a Melting Point in the range of about 96-105~F.
A primary use for these products is confectionery coatings. The present invention has also been advantageously used with a hydrogenated rearranged coconut or palm kernel oil having a Melting Point in the range of about 93-104F. Primary uses for these products are confectionery coatings and vegetable dairy systems.
The present invention can also be used advantageously with a lauric stearine.

All of the above applications are food uses. It should be understood that the present invention also has applicability in oosmetic and pharmaceutical applications where both oxidative and hydrolytic rancidity must be avoided.

Citric acid has a decQmposition temperature of about 150C, so that it is necessarily added, as mentioned, subsequen-t to final deodorization. It can be anhydrous or dissolved in water or another carrier. For ease oE dispersibility, a solution is preferred. For food applications the citric acid must be food grade. The amount added is a sequestering amount. The exact amount added will depend upon use, type of fat or oil, type of storage, and other parameters well Xnown in the industry, and is not a part of the present inventionO In the examples of the present application, it is added at a level of 20 ppm based on the weight of fat. This is a conventional sequestering amount. Also in the examples of this application, it is added as a solution.
The carrier used was propylene glycol, with the concentration of citric acid in the carrier being about 10%; o-ther carriers such as water or ethyl alcohol could be used.
The lecithin can be added either prior to or subsequent to final deodorization. Any commercially available lecithin product can be used. Most commercially available lecithins are soybean derived; however, lecithins derived from other oils such as canola oil could be used. An hydroxylated lecithin can also be used.
The lecithin can be in liquid or granular form. All lecithins derived from soybean oil, even granular lecithins, have a characteristic flavor and odor, although in the case of granular lecithin the flavor is a relatively non-objectionable, nutty flavor. If the lecithin is added to the fat or oil prior to final deodorization, the flavor and odor can be improved by removal of volatiles.

~ X

It is known, however, that lecithin is subject to de-gradation from high -temperatures, causing darkening of the fat or oil to which it is added. Deodoriæation is conven-tionally carried out at 430-450F and will cause oil darkening if the lecithin is added prior to deodorization. This darkening can be prevented or minimized in several ways, one being by treatment of the lecithin with a s-trong base such as sodium hydroxide, magnesium hydroxide or potassium hydroxide, following the teachings of patent No.
4,528,201. Another is pretreatment of the lecithin dissolved in a small amoun-t of fat by the addition of water followed by heating and filtration, as disclosed in U.S. patent No. 4,524,085, issued 18 June 1985 to Procter & Gamble CoO
The pretreatment process of patent No. 4,524,085 invol-ves adding water to lecithin previously mixed with a small amount of fat. The lecithin is diluted with fat such that the lecithin is from about 5% to about 85%, preferably from about 5% to about 25%, by weight of the lecithin/fat mixture. Water is added in an amount such that it constitutes from about 5% to about Z5% by weight of the lecithin, preferably from about 5~ to about 50% by weight of the lecithin. The mixture is heated to a temperature of from about 130F. (54C) to about 170F (77C) with mixing. The mixture is fil-tered hot.
The treatment process of 4,528,201 involves adding the base as a water solution, either directly to the fat or as a pre-treatment of the lecithin. The amount of basic solution added will depend upon the concentration of the basic solution.

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8a 73390-3 Solutions of about 5% to about 50% base by weight are preferred.
For weaker bases, solutions of from about 20% by weigh-t base to saturated solutions can be employed. Addition as a solid often results in incomplete disso]ution and dispersal in the fat result-ing in uneven color development. To retard fat discoloration upon heating, a minimum base concentration of at least about 0.00005%
by weight of the fat is required. Preferably, for the composi-tions of the present invention, the base concentration comprises at least about 0.0003% by weight of the fat. Most preferably, the base concentration comprises a minimum of about 0.0015% by weight of the fat.
Further details on the amount of base required can be found in the '201 patent.

~2~

Any of several stabilization technigues for treatment of the lecithin or fat with a strong base can be employed. Each method is effective to prevent discoloration of the fat. One method to retard discoloration by base stabilization of the lecithin is to add the base directly to the fat either prior to or after addition of the lecithin. No pretreatment of the lecithin is required.

~n a pretreatment stabilization process for the lecithin, a strong base is added to lecithin optionally mixed with a small amount of fat, heated and mixed, and added to the lauric fat.

In a third alternative, the base can be added to lecithin optionally mixed with a small amount of fat, heated and filtered, and mixed with the lauric fat. Filtration of the lecithin in combination with the base treatment reduces color development more than the base treatment alone. Much of the lecithin is rem~ved by the filtration, thereby additionally reducing color development. A
final pretreatment stabilization process for the lecithin comprises: ~1) addition of a strong base to lecithin; (2) optional neutralization of the resulting solution; (3) extraction of the lecithin with a nonpolar solvent, and (4) addition of the lecithin to a lauric fat. The neutralization is usually accomplished by addition of an acid such as phosphoric acid. Hexane, or other similar nonpolar solvents are employed for the extraction step. The extracted lecithin can be heated to aid in its dispersion in the lauric fat. An equivalent procedure is to dissolve crude lecithin in a nonpolar solvent such as hexane with the strong base, neutralize with an acid/base titration, extract the lecithin, wash it with a solvent such as acetone, and add it to the desired fat.
.

In a paper entitled "A Process for the Separation of Phosphatide Mixtures: The Preparation o Phosphatidyl Ethanolamine-Free Phosphatides from Soya Lecithin", R. Aneja et al~ it is disclosed that phosphatidyl choline tPC~, phosphatidyl ethanolamine (PE) and phosphatidyl inositol (PI) are the three major phosphatide con-s-tituents of soya lecithin. This paper discloses a process for separation of phosphatidyl choline and phosphatidyl inositol from commercial soya lecithin, to give a product which is free of phos-phatidyl ethanolamine. The three chief phosphatides, PC, PE and PI, are yenerally present in approximately equal amounts in soy-bean lecithin. In this paper, it is disclosed that PE has a dele-terious affect on the anti-spattering properties of PC and would best be removed completely from the mixture. There is no reference in this paper to the processing of fats, particularly lauric fats and oils, or to the use of lecithin prior to deodorization.
The present invention, in part, resides in the discovery that removal of PE from lecithin is also effective in minimizing thermal darkening of lauric fats and oils during deodorization.
In the following Examples, parts expressed are parts by weight, and percentages are percentages by weigh-t.

This Example illustrates the effect of treating a hydro-genated and rearranged lauric fat with both citric acid and leci-thin. The citric acid was added in a sequestering amount. ~oth the lecithin and citric acid were added subsequent to final deodorization.
The particular fat treated was Paramount B (trademark SCM Corporation), a partially hydrogenated rearranged palm kernel oil having a Wiley Melting Point of about 93-96F, an IV of about 3 maximum, a free fatty acid content of about 0.05 maximum and an SFI profile as follows:

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Temperature Solids 50F 64 min.
70F 51 min.
80F 35 min.
92F 6 min.
100F 1 max.
Th0 fat is conventionally used in confectioner's coat-ings, vegetable dairy systems, candy centers, icings, cosmetics and pharmaceutical products.
The lecithin treatment was carried out in one series of runs with a typical natural, fluid, soybean lecithin marketed under the trademark Actiflo 68-SB by Central Soya. This lecithin is in solution form comprising about 66-68% active phospholipids (about 23~ PC, 30% PE and 14% PI). It is marketed as an amber fluid.
; In a second series of runs, the lecithin treatment was ; carried out with a hydroxylated soybean lecithin marketed by Cen-tral Soya under the trademark Centrolene A. This product has been 58% active phospholipids and is marketed as a heavy bodied fluid.
In the treatment process, the citric acid was added as a 10% propylene glycoL solution. It was added in an amount necess-ary to give the oils a citric acid concentration of 20 ppm. There is no criticality with regard to order of addition.
Water also was added to all samples, except control samples, to apply a simulated stress to the lauric fat. The water was added at percent levels of 0.05 and 0.10. The lecithin was added in the amounts of zero and 250 ppm. No advantage was seen ~ in exceeding a concentration of 250 ppm.
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The procedure followed was adding warm distilled water directly to the oil, which was heated to about 50C. A nitrogen atmosphere was maintained over the oil while it was mixed for 15 minutes with a mechanical stirrer (3000 RPM). The samples requiring no added water were still subjected to the 15 minute mixing under nitrogen at 50C. The results obtained are given in the following Table 1 (for the addition of Actiflo lecithin) and Table 2 (for the addition of hydroxylated lecithin). Storage results in terms of free fatty acid and flavor develo~nent were obtained at intervals of two months, four months, and six rnonths.

SE2 FOLLOWING P~OES FOR TABLES

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The data of Table 1 shows that in a hydrogenated rearranged lauric fat the free fatty acid content, with no lecithin added tsamPles 1, 3 and 5) increased substantially even with no water present. In sample 1, with no water added, the increase was from 0.02 to 0.15%
over the storage period. In s~mple 3, having 0.05~ added water, the increase was to 0.38%~ and in sample S, the increase was to 0.56~.

All samples showed corresponding decreases in flavor. A lower flavor value indicates poorer flavor, with optimum being about B, plus or minus, wi~h an acceptible flavor rated about a 7. The flavor score is a subjective panel evaluation only and is subject to substantial error or deviation. However, the data does show a flavor deterioration for the lecithin-free samples from a mean of about 6.8 to a mean of about 5.

By contrast, samples 2, 4 and 5 containing 250 ppm lecithin were koth free fatty acid and flavor stable, showing virtually no hydrolysis even with water levels of 0.05~ and 0.10% (samples 4 and 6). The flavor scores of the lecithin oontaining samples decreased slightly during storage from a mean soore of about 7.2 initially to a mean score of 6.4 at six months.

A~ain, there appeared to be no advantage in adding lecithin at a level m~re than 250 ppm, for instance 500 or 1000 ppm, although nothing precludes such higher addition, other than economics.

Similar data is given in Table 2, with those samples having hydroxylated lecithin showing little free fatty acid build-up, those without lecithin having substantial build-up, e.g., up to ~ .53%.

No flavor data is given since the hydroxylated lecithin itself tended to impart to the samples a "sour" off-flavor.

In this Example, the starting oil was fractionated palm kernel oil deodorized to a free fatty acid content of less than 0.01%. The oil had a Mettler Drop Point of about 33.3C, a calculated rv of about 5, and fatty acid and SFI data as follows:

Approximate FAC Va1ue 12:0 58 14:0 21 16:0 8.~
Others Remainder SFI

92F 4 max The procedure used was the same as in ~xample 1. The following data was obtained.

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D ~ o o o ~1 o o o ol o - -~ ~ ~ ~31 0 o o r~

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In Table 3, sample 1 was a control s~nple and shows that this oil inherently is very stable. With no water added, even with citric acid present, the sample showed little free fatty acid build-up.
However, with the addition of 0.10% waterl there was substantial free fatty acid build up, to about 0.21%. In the presence of lecithin, this build-up was held to about 0.02%.

Similar data was obtained with the use of hydroxylated lecithin.
With 0.05~ added water and no lecithin, the free fatty acid build-up after six months was about 0.27%. In the presence oE 250 ppm hydroxylated lecithin, the free fatty acid build-up was held at about 0.02%, from an initial value of about 0.02%.

In this example, the lecithin added was a granulated lecithin marketed by Riceland Foods under the trademark Lecigran F. An advantage in using a granulated lecithin is that it is generally free of the characteristic soybean odor. The lecithin was 97~
active phopholipids (about 23.5% PC, 20% PE, 14% PI and 39.5% other phospholipids).

The procedure used was the same as in Example 1. The data obtained in Table 4 shows that with as little as 50 ppm granulated lecithin the free fatty acid build-up is negligible.

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Granulated Citric Initial 1 month 2 months 3 nths Lecithin Acid Water %FFA %FFA %FFA _ ~FFA
200 ppm 20 ppm .1% .02 .02 .03 .03 100 ppm 20 ppm .1% .02 .02 .02 .02 50 ppm 20 pEm .1% .02 .02 .02 .02 O ppm 20 ppm .1% .03 .11 .16 .17 With up to 250 ppm granulated lecithin added, the same is non-detectable in tenms of odor and flavor.

Claims (12)

1. A process for reducing or preventing both hydrolytic and oxidative rancidity in lauric fats and oils comprising the steps of adding to said fat or oil a) a sequestering amount of citric acid; and b) lecithin in an amount effective to provide at least 30 parts per million and not more than 250 parts per million active phospholipids based on the weight of fat or oil.

2. The process of claim 1 wherein said fat or oil is deodorized prior to citric acid and lecithin addition.

3. The process of claim 1 wherein said lecithin is granular.

4. The process of claim 1 or 2 wherein said fat or oil is a fractionated palm kernel or coconut oil.

5. The process of claim 1 or 2 wherein said fat or oil is a hydrogenated, rearranged palm kernel oil having a Wiley Melting Point in the range of about 93-104°F.

6. The process of claim 1 or 2 wherein said fat or oil is prepared by esterification of fatty acids and glycerine.

7. The process of claim 1 wherein said fat or oil is a blend of a lauric fat or oil with a non-lauric fat or oil.

8. The process of claim 1 wherein the lecithin is added prior to deodorization and is substantially free of phosphatidyl ethanolamine.

9. The process of claim 1 wherein said lecithin is added prior to deodorization and is treated with a strong base.

10. The process of claim 1 wherein said lecithin is dissolved in a carrier oil.

11. The process of claim 1 wherein said lecithin is dissolved in coconut, palm kernel or soybean oil.

12. A lauric fat or oil treated by the process of any one of claims 1, 2, 3, 7, 8, 9, 10 and 11.