80th JECFA - Chemical and Technical Assessment (CTA), 2015 © FAO 2015

MAGNESIUM STEARATE

Chemical and Technical Assessment (CTA)

Prepared by I. Stankovic and reviewed by Madduri V. Rao

1. Summary

This Chemical and Technical Assessment summarizes data and information on Magnesium stearate submitted to JECFA by the sponsor in December 2014. Magnesium stearate is used as anticaking agent, lubricant and release agent, emulsifier, binder, thickener and antifoaming agent. Typical applications in food industry include food supplement tablets, capsules and powders, compressed and granulated mints and candy, chewing gum, herbs and spices and, bakery ingredients. The use levels in these categories range from 0.05-3% w/w. Magnesium stearate is an off-white to white, fine, light powder that is greasy to the touch and practically insoluble in water and in anhydrous ethanol. The commercial form of food additive magnesium stearate is mainly composed of variable proportions of magnesium stearate and magnesium palmitate and minor proportions of other magnesium salts of fatty acids, obtained from edible fats and oils of animal or vegetable origin. Magnesium salts of fatty acids had been previously included in the INS number 470 (Salts of fatty acids). An Acceptable Daily Intake for its use in food has not been allocated by the 29th meeting of JECFA since there was no food uses reported to JECFA at that time. Their deletion from the Codex International Numbering System had been proposed at the 42nd Session of the CCFA in 2010. The International Alliance of Dietary/Food Supplement Associations (IADSA) offered technological justification for not deleting this additive and the CCFA assigned therefore the INS number 470(iii) at the 43rd Session in 2011.

2. Description

The commercial form of food additive magnesium stearate, as opposed to chemically pure magnesium stearate, is mainly composed of variable proportions of magnesium stearate [Mg(C18H35O2)2] and magnesium palmitate [Mg(C16H31O2)2] and minor proportions of other magnesium salts of fatty acids, obtained from edible fats and oils of animal or vegetable origin. Magnesium stearate is commonly described by the following CAS numbers: 557-04-0 (Magnesium stearate) and 91031-63-9 (Fatty acids, C16-18, magnesium salts). It has a characteristic faint odour and occurs as a white or almost white, fine, light powder that is greasy to the touch and practically insoluble in water and in anhydrous ethanol. The existence of various crystalline forms of magnesium stearate has been reported. A trihydrate, a dihydrate, and an anhydrate have been isolated, and an amorphous form has been identified. While the hydrate forms are stable in the presence of moisture, the anhydrous form adsorbs moisture at

Magnesium Stearate (CTA) 2015 - Page (1) of (6) © FAO 2015 relative humidity up to 50%, and at higher humidity rehydrates to form the trihydrate. The anhydrate can be formed by drying either of the hydrates at 105°C. Commercial lots of magnesium stearate generally consist of mixtures of crystalline forms (Rowe 2009). Physical properties of magnesium stearate can vary among batches from different manufacturers because the solid-state characteristics of the powder are influenced by manufacturing variables. Various physical properties of different batches of magnesium stearate such as specific surface area, particle size, crystalline structure, moisture content, and fatty acid composition have been correlated with lubricant efficacy (Rowe 2009).

3. Manufacturing process

Magnesium stearate for food applications is commonly manufactured by one of two following processes: the direct process, also called fusion process, or the precipitation process, also called indirect process. The fatty acids used as raw material are derived from edible fats and oils and consist mainly of stearic and palmitic acid. The fatty acids are referred to as HFA in the reactions below. In the direct process, fatty acids are directly reacted with a magnesium source such as magnesium oxide to form magnesium salts of the fatty acids:

2 HFA + MgO  Mg(FA)2 + H2O

The precipitation process is a two-step process. In a first step a sodium soap is produced by the reaction of the fatty acids and sodium hydroxide in water. In the second step magnesium salts are precipitated by adding magnesium salts:

Step 1: 2 HFA + 2 NaOH  2 NaFA + 2 H2O 2+ + Step 2: 2 NaFA + Mg  Mg(FA)2 + 2 Na

4. Chemical characterization

4.1 Composition

The commercial products consist of 95-99% magnesium salts of fatty acids on the dried basis of which 4-5% account for magnesium. The fatty acid fraction is composed of at least 90% of stearic and palmitic acid with a minimum of 40% stearic acid. This is reflected by representative certificates of analysis of 10 commercial batches provided by the sponsor.

Magnesium distearate as such has the chemical formula Mg(C18H35O2)2 and a molecular weight of 591.27 g/mol. The molecular structure of magnesium distearate is shown in Figure .

Figure 1: Molecular structure of magnesium distearate

Magnesium Stearate (CTA) 2015 - Page (2) of (6) © FAO 2015 Besides magnesium salts of stearic and palmitic acid, other magnesium salts with fatty acids such as lauric acid, myristic acid, pentadecanoic acid, margaric acid, oleic acid and arachic acid may be present in the additive as minor components. The composition and distribution of the fatty acid fraction of commercial magnesium stearate depends on the vegetable or animal source material of the fatty acid used as raw material for the production of the additive and the fractionation conditions to which the source material was subjected. The GC chromatograms from 22 commercial batches provided by the sponsor demonstrate the distribution of fatty acids in the fatty acid fraction of vegetable based (high and low palmitate types) and animal based magnesium stearate products. The analysis was performed with the method proposed in the additive specification which analyses fatty acids as methylesters and calculates the percent area of the fatty acids in the chromatogram. Table 1 summarises the quantitative data from these chromatograms as ranges of the identified fatty acids and includes also the sum of palmitic and stearic acid, a parameter which is part of the proposed specifications.

Table 1: Composition of the fatty acid fraction of 22 commercial magnesium stearate batches

Fatty acids Proportion in fatty acid fraction (%) Type Name Vegetable based Vegetable based Animal based (low palmitate) (high palmitate) C12 Lauric acid - 0.0−0.6 0.0−1.1 C14 Myristic acid 0.0−0.3 0.0−1.4 1.1−2.3 C15 Pentadecanoic acid - 0.0−1.2 0.2−0.3 C16 Palmitic acid 30.2−34.2 53.5−56.9 28−31 C17 Margaric acid 0.1−-0.2 0.2−0.3 0.9−1.0 C18 Stearic acid 65.1−69.5 41.1−44.8 64.2−67.0 C18:1 Oleic acid 0.0−0.1 0.0−0.1 0.0−0.2 C20 Arachidic acid 0.0−0.7 0.4−0.5 1.3−1.5 C16+C18 Palmitic+Stearic acid 98.8−99.5 97.1−99.4 92.1−95.2

In one batch of animal based magnesium stearate also 0.1% ketostearic acid, 0.1% palmitoleic acid and 0.2% nondecanoic acid was found. The amount of total fatty acids other than palmitic or stearic acid ranges from 0.5-8% in the batches analysed.

4.2 Impurities

Potential impurities of the final magnesium stearate product are limited to those that originate from the starting material and substances used in the production process and include chlorides, sulphates, cadmium, lead and nickel. The neutralisation reaction in the manufacturing process is controlled by acidity/alkalinity testing, whereby excess of magnesium oxide or free fatty acids is prevented. Impurities are controlled by specifications as demonstrated by representing certificates of analysis of 2 commercial batches of animal and vegetable based product provided by the sponsor. According to the sponsor, since the fatty acids used as raw material are obtained in a very pure form via distillation there are no further impurities in form of organic materials such as lecithin, gossypol, sterols, carotin, chlorophyll, proteins and other potential products synthesized by the animal or plant as well as any potential decomposition products of fats and oils. From an assessment on risk of dioxin contamination performed by the manufacturers the general conclusion has been drawn that no significant Dioxin/DLPCBs contamination is expected in fatty acid source material such as rendered animal fats and vegetable oils used by the oleochemical industry as they are coming from the food and feed chain for which legislation is already very strict and as the

Magnesium Stearate (CTA) 2015 - Page (3) of (6) © FAO 2015 production process would further decrease any potential natural existing contamination. A contamination could be theoretically caused only by intentional/unintentional blending with spent oils from mineral or synthetic origin.

4.3 Analytical methods

Assay method, identification tests and individual purity tests proposed are taken from the European Pharmacopoeia (7.4) Monograph on Magnesium Stearate (Council of Europe, 2010) and standard methods published in the Combined Compendium of Food Additive Specifications (FAO JECFA Monographs 1, 2006: Volume 4). The assay method for the fatty acids involve saponification of the salt followed by esterification of the fatty acids in the presence of boron trifluoride and anhydrous-alkaline methanol and subsequent gas liquid chromatography of the fatty acid methyl esters. While the method description and procedure is taken from European Pharmacopoeia (7.4) the expression of results is based on the assay method in JECFA specifications on salts of fatty acids (FAO JECFA Monographs 2005) which is based on the same principle. Identification tests involve identification and determination of the fatty acid composition in the fatty acid fraction via the assay method and identification and quantification of the magnesium content. Purity tests include quantification of cadmium, lead and nickel as well as determination of acidity or alkalinity, unsaponifiable matter and loss on drying using standard methods described in the Combined Compendium of Food Additive Specifications (FAO JECFA Monographs 1, 2006: Vol. 4). Analytical data provided by the sponsor for five non-consecutive lots of magnesium stearate support the applicability of the proposed methods for analysing the products of commerce.

5. Functional uses

5.1 Technological function

Magnesium stearate is used as food additive in the following technological functions: Lubricant / Release agent Magnesium stearate is mainly used in the food industry for the production of food supplements and confectionery compressed tablets. In tablet technology, when added to the powder before compression, it acts as a lubricant and assists in the ejection of the tablet from the punch and die. It prevents parts of the tablet sticking to the punches. The magnesium stearate also provides a smooth surface to the tablet. The amount of magnesium stearate used in a tablet formula is dependent on the ‘stickiness’ of the pre-compression granule, but would normally not exceed 3% w/w. Anticaking agent Magnesium stearate improves the flowability and continuity with its anti-caking effect in certain dry powdered foods (e.g. spices and herbs) to extend the shelf life of these powders. Emulsifier / Binder Magnesium stearate can be used as an emulsifier in bakery ware such as rusks and baking powder. It is also used to bind sugar in hard candies like mints.

5.2 Food categories and use levels

Magnesium Stearate (CTA) 2015 - Page (4) of (6) © FAO 2015 A survey on current food applications of magnesium stearate provided by the sponsor has been performed in 2013 based on information provided by IADSA (International Alliance of Dietary/Food Supplement Associations), APAG (European Oleochemicals and Allied Products Group), NCA (The National Confectioners Association) and ICGA (International Chewing Gum Association). The summary is shown in Table 2.

Table 2: Survey on use levels and food applications of magnesium stearate

Food Category Technical Proposed Average use Max. use level Cat. # (GSFA) functions food uses level (mg/kg) (mg/kg) 0.5.2 Confectionery Anticaking agent, Hard candy, 10 000 13 000 including hard lubricant, binder pressed mint and soft candy, (0.5.2.1) nougats, etc. Mint pastille 5 000 9 500 other than food (0.5.2.1) categories 05.1, 05.3 and 05.4 0.5.3 Chewing gum Emulsifier, Chewing 100-10 000 20 000 anticaking agent, gums drying agent 13.6 Food Lubricant, Food 13 000 30 000 Supplements anticaking agent, supplements: emulsifier, (chewable) thickener tablets, capsules, powders 07.0 Bakery wares Foaming agent, Rusks, baking >500 2 500 emulsifier powder 12.2.1 Herbs and spices Anticaking agent, Spices, herbs >500 10 000 hydrophobation

6. Reactions and fate in food

Magnesium stearate is a stable product for which no decomposition products are expected under normal storage conditions. Auto-oxidation products, as common in fats and oils, can typically occur in unsaturated fatty acids (Belitz et al. 2008) and are not expected for saturated fatty acids such as stearic acid and palmitic acid. A moisture uptake during longer storage (> 12 months) may take place. There is no data available regarding stability of magnesium stearate in food applications, but based on the long history of use, magnesium stearate has been reported to be very stable under normal conditions of use. As pharmaceutical excipient, magnesium stearate has been reported to be incompatible with strong acids, alkalis and iron salts and should be avoided to be mixed with oxidizing materials. It should not be used in products containing aspirin and some vitamins and most alkaloidal salts (Rowe 2009).

7. References

Belitz, H.D., Grosch, W., Schieberle, P. (2008). Lehrbuch der Lebensmittelchemie, 6. Auflage, Berlin Heidelberg: Springer Verlag.

Magnesium Stearate (CTA) 2015 - Page (5) of (6) © FAO 2015 CFR (1985). Code of Federal Regulation. Title 21 I, B, Sec. 184.1440 Magnesium stearate.

Codex Alimentarius Committee (2012). Class names and the international numbering system for food additives. Adopted in 1989 [CAC/GL 36-1989] Revision 2008, last amendment 2012.

Commission Regulation (EU) No 231/2012 of 9 March 2012 laying down specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008 of the European Parliament and of the Council, OJ L 83, 22.03.2012 [E470b p. 187-188].

Council of Europe (Ed.) (2010). Magnesium Stearate. 07/2010:0229. European Pharmacopoeia. Supplement 7.4. 7th Edition. Nördlingen (Germany):C.H.Beck.

FAO JECFA Monographs 1 (2006). Combined Compendium of Food Additive Specifictations. Volume 4, Analytical methods, test procedures and laboratory solutions used by and referenced in the food additive specifications.

FAO JECFA Monographs 1(2005). Combined Compendium of Food Additive Specifictations. Volume 3 Food additives; Salts of fatty acids p.275 Prepared at 33rd JECFA (1988) published in FNP 38 (1988) and in FNP 52 (1992).

FCC (2010). Food Chemicals Codex (FCC 7). 2010-2011, 7th edition. The United States Pharmacopeial Convention. Monograph on magnesium stearate p. 609.

FDA SCOGS Database 2013. Conclusion of Report No. 60, regarding magnesium stearate by Select Committee on GRAS Substances (SCOGS, 1976):

JECFA (1973). Seventeenth report of the Joint FAO/WHO Expert Committee on Food Additives, WHO Food Additive Series 5 / FAO Nutrition Meetings Report Series No 53A [1973, FAS 5/NMRS 53A-JECFA 17/19];

JECFA (1986). Evaluation of certain food additives and contaminants. Twenty-ninth report of the Joint FAO/WHO Expert Committee on Food Additives. WHO Technical Report Series, No. 733, 1986. [1985, TRS 733-JECFA 29]; See also

Regulation (EC) No 1333/2008 of the European Parliament and of the council of 16 December 2008 on food additives, OJ L 354, 31.12.2008 [consolidated 03.06.2013].

Rowe, R. C. Sheskey, P. J., Quinn, M. E (2009). Handbook of pharmaceutical excipients. 6th edition. London: Pharmaceutical Press.

SCOGS (1976). Select Committee on GRAS Substances. Evaluation of the health aspects of magnesium salts as food ingredients. Prepared for Bureau of Foods Food and Drug Administration Department of Health, Education, and Welfare Washington, D. C. Contract No. FDA 223-75-2004 Life Sciences Research Office Federation of American Societies for Experimental Biology.

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