Is propylene glycol alginate a safe food additive?
Propylene glycol alginate (PGA) is an ester of alginic acid, derived from brown seaweed, and food additive used to stabilize, thicken, and emulsify [1]. Brown seaweeds have been used as a food for centuries but it is only since 1929 that alginates have been manufactured on an industrial scale [2].
Chemically, propylene glycol alginate is an ester of alginic acid, which is derived from kelp. Alginic acid, also referred to as algin or alginate, is a hydrophilic or anionic polysaccharide isolated from certain brown seaweed (Phacophycae) particularly from the genera Ascophyllum, Macrocystis, and Laminaria via alkaline extraction [3]. Algin is also made by some types of bacteria [4,5].
Alginic acid is present in cell walls of brown algae where it forms a viscous gel when binding with water. Alginic acid is a linear polymer that consists of L-glucuronic acid and D-mannuronic acid connected via 1,4-glycosidic linkages. Alginates have valuable rheological properties which can be varied to a great extent by varying the degree of polymerization of the polysaccharide or by changing the ionic environment. Thus alginates can provide solutions having a range of viscosities or gels of varying rigidities which may be used as texture modifiers in a wide range of food applications.
Propylene Alginate as a Food Additive
1. Propylene glycol alginate helps give products a smooth and natural texture and taste even under reduction conditions, such as in yogurt.
2. Propylene glycol alginate helps give products a glossy and smooth appearance.
3. Propylene glycol alginate can mix well with other ingredients and can be applied during the fermentation process in any range of pH value. Further, PGA improves dispersibility and solubility in products, and is heat stable.
4. Propylene glycol alginate not only acts as a stabilizing agent, but emulsifies.
Human Risk Characterization of Propylene Glycol Alginate
A study in five healthy men evaluated the effects of consuming PGA at doses of 175 mg/kg for 7 days followed by 200 mg/kg for 16 days [6]. To simulate how PGA would be consumed as a food additive, it was combined with orange juice and water to form a thick fluid gel and consumed across 3 daily servings. No effects were seen for hematological, biochemical, urinary, or fecal parameters. There were also no reports of subjective symptoms like GI disturbances.
There has been a single case study documenting poisoning from PGA, but it was due to drinking enough whiskey to push his BAC to 640 mg/dL (0.64 g/dL; the legal limit is 0.08 g/dL) and put him in a coma [7]. The patient suffered metabolic acidosis that could be accounted for, in part, from the large amount of PGA found in serum that apparently came from the cinnamon flavored whiskey. Later, his specific whiskey was found to be recalled due to PGA concentrations above the allowed 5% limit in foods.
Propylene glycol alginate exhibits low acute toxicity when administered by the oral route [8]. In animal studies, propylene glycol alginate did not cause developmental or reproductive toxicity at any of the tested doses. Carcinogenicity studies indicate it is not a carcinogen, and in vitro studies reveal an absence of genotoxic effects. The WHO concluded that reduced growth and loose stools are the predominant adverse health effects in animal studies owing to poor absorption via the gastrointestinal tract.
Exposure to propylene glycol alginate as a result of its use as an inert ingredient in products is possible through dietary exposure. The FDA allows for propylene glycol alginate to be added as an emulsifier, flavoring adjuvant, formulation aid, stabilizer, surfactant, or thickener. It should also be noted that the WHO’s Committee on Food Additives (Series 32, 1993) has allocated an acceptable daily intake for propylene glycol alginate of up to 70 mg/kg of body weight [9].
Propylene glycol alginate’s low toxicity, combined with the fact that it biodegrades readily and is not likely to bioaccumulate, will limit potential risk to human health. Should propylene glycol alginate be ingested by the human body, it will either be absorbed and hydrolyzed via a known metabolic pathway to form acetate, lactate, or glycogen, or excreted as the parent compound almost completely.
Therefore the risks to human health as a result of consumption are likely to be low.
Consideration for Propylene Glycol Alginate in Paleo and Keto Certification
Certified Paleo
Natural compound extracted from seaweed
Relatively safe food additive
KETO Certified
Provides zero calories and does not interfere with ketogenesis or hyperketonemia
References:
1. Propylene Glycol Alginate. Prepared at the 49th JECFA (1997) superseding specifications prepared at the 44th JECFA (1995), published in FNP 52 Addendum 3 (1995) FAO. http://www.fao.org/3/W6355E/w6355e0u.htm
2. Propylene Glycol Alginate. G.J.A. Speijers, M.E. van Apeldoorn. National Institute of Public Health and Environmental Protection Laboratory for Toxicology. Bilthoven, The Netherlands.
3. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
4. Skjåk-Bræk, G. (1992). Alginates: biosyntheses and some structure-function relationships relevant to biomedical and biotechnological applications. Biochemical Society Transactions, 20(1), 27–33. doi:10.1042/bst0200027
5. Leid, J. G., Willson, C. J., Shirtliff, M. E., Hassett, D. J., Parsek, M. R., & Jeffers, A. K. (2005). The Exopolysaccharide Alginate Protects Pseudomonas aeruginosa Biofilm Bacteria from IFN- -Mediated Macrophage Killing. The Journal of Immunology, 175(11), 7512–7518. doi:10.4049/jimmunol.175.11.7512
6. Anderson, D. M. W., Brydon, W. G., Eastwood, M. A., & Sedgwick, D. M. (1991). Dietary effects of propylene glycol alginate in humans. Food Additives and Contaminants, 8(3), 225–236. doi:10.1080/02652039109373973
7. Cunningham, C. A., Ku, K., & Sue, G. R. (2015). Propylene Glycol Poisoning From Excess Whiskey Ingestion. Journal of Investigative Medicine High Impact Case Reports, 3(3), 232470961560372. doi:10.1177/2324709615603722
8.Toxicological evaluation of certain food additives and contaminants / prepared by the forty-first meeting of the Joint FAO/WHO Expert Committee on Food Additives (JEFCA) [meeting held in Geneva, from 9 to 18 February 1993]
9. Propylene Glycol Alginate.(1993). World Health Organization. WHO Food Additive Series: 32, 159-169
