Content Table

• Comparing GEGR and GEWR
• Applications of Food-Grade GEGR
• What are the food safety risks of GEGR?
• Alternatives to ester gum
• References

Comparing GEGR and GEWR

Glycerol ester of gum rosin is an industrial-grade glyceride. It is made primarily from oleoresin and glycerol through esterification and refining^【1】. It is synonymous with “glyceryl rosinate”. In everyday English, people often simply call it “resin ester” or “ester gum”.

This material is a traditional ingredient for industrial adhesives and film-forming agents. Meanwhile, food-grade ester gum has many uses in the food industry. It acts as a weighting agent in citrus-flavoured drinks. It is also a stabiliser for cloudy liquid systems, and it works as a tackifier or softener in chewing gum bases.

When looking at the manufacturing process, food-grade ester gum must meet very strict specifications. The process tightly controls the levels of heavy metals, such as lead. It also strictly limits the acid value of free resin acids. More importantly, it focuses on achieving a specific proportion of triglycerides.

This strict control does more than just ensure chemical stability and a consistent softening point. There is a deeper reason for these limits, which relates to how molecular size interacts with biological membrane barriers.

High-purity triglycerides have a large molecular weight and significant steric hindrance. As a result, their absorption rate in the intestine is extremely low. This significantly reduces any potential risk of systemic toxicity.

In contrast, smaller molecules such as monoesters have clear hydrophilic-lipophilic balance (HLB) properties. They can act as surfactants and alter cell membrane permeability, which increases the unwanted penetration of other substances.

Therefore, the esterification process must convert monoesters and diesters into triglycerides to the greatest extent possible. This maximum conversion is the core theoretical basis for ensuring the biological safety of ester gum as a food additive.

At the same time, food-grade specifications set extremely low limits for other oxides and neutral substances. This helps to further eliminate any potential health risks.

Glycerol ester of gum rosin refers specifically to a glycerol ester of resin acids derived from gum rosin. Depending on the raw material source, common types of ester gum also include Glycerol ester of wood rosin (E445), Glycerol ester of tall oil rosin, Glycerol ester of polymerised rosin, and Glycerol ester of hydrogenated gum rosin.

When used as food additives, the most authoritative certifications come from the ADI assessments conducted by JECFA under FAO. These assessments established an ADI of 0–12.5 mg/kg bw for Glycerol ester of gum rosin, and 0–25 mg/kg bw for Glycerol ester of wood rosin^【2,3】.

	GEGR	GEWR
Solubility	Insoluble in water; soluble in acetone
Specific Gravity, d2025, @50% solution in d-limonene	Not less than 0.935
Softening Point, @R&B, °C	Not less than 82	Not less than 82
Acid Value	3 to 9	3 to 9
Lead, @AAS/ICP-AES	Not more than 1 mg/kg
ADI, @mg/kg bw	0 to 12.5	0 to 25
Table 1. The datas was established at the 74th JECFA (2011) and published in FAO JECFA Monographs 11 (2011).

Although Glycerol ester of wood rosin and Glycerol ester of gum rosin share many similarities in physicochemical properties and characterisation, international authorities have established a clear and specific definition for Glycerol ester of wood rosin. It is formally defined as a mixture comprising resin acids (90%) and neutral substances (10%), obtained by extracting and refining aged stumps of longleaf pine (P. palustris) or slash pine (P. elliottii) using organic solvents.

In contrast, Glycerol ester of gum rosin refers specifically to ester gum produced from gum rosin tapped from living pine trees. As the resin acid composition of wood rosin obtained from aged stumps differs from that of fresh gum rosin, its degree of oxidation and isomerisation also differs. In particular, the proportion of the specific free isomer, neoabietic acid, is not the same. For this reason, the ADI data for Glycerol ester of wood rosin are not generally considered directly applicable to Glycerol ester of gum rosin on a global basis. However, under national standards, and in China in particular, Glycerol ester of gum rosin may be used as a food additive provided that it complies with the national standard GB 10287-2012.

By the end of 2025, the original Association Standard for Glycerol ester of gum rosin had been withdrawn^【4】. A new Association Standard is expected to be released soon.

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Applications of Food-Grade GEGR

The applications of food-grade Glycerol ester of gum rosin and food-grade Glycerol ester of wood rosin are broadly similar. In beverages, both are used to provide weighting and stabilisation for flavouring oils. In chewing gum, both are used to increase tack and improve the plasticity of the gum base. Overall, they function as resins for adjusting physical properties.

Weighting agents

In soft drink production, flavouring oils are used as highly concentrated hydrophobic liquids that provide aroma and characteristic taste, such as cold-pressed orange oil, lemon oil and lime oil. Because these flavouring oils are less dense than water and do not dissolve in water, they tend to float, form separate layers, or even cling to the inside of the bottle. In such cases, a weighting agent (density adjustment agent) is needed to adjust the density of the flavouring oil so it becomes closer to that of water.

Ester gum has a higher density than flavouring oils and is soluble in them. Once dissolved, it increases the density of the oil phase so that it approaches that of the aqueous phase. When combined with emulsifiers, such as gum arabic or modified starch, to form a fine oil-in-water emulsion, this approach can significantly reduce the upward movement of oil droplets and minimise phase separation.

Stabilisers

Some non-alcoholic cloudy flavoured beverages aim for a heavier, more opaque appearance that gives the impression of real fruit juice. Ester gum is composed primarily of diglycerides and triglycerides, which together account for approximately 90% of its composition. As a whole, it consists of large molecules with strong hydrophobicity and forms a glassy state. Once dissolved into the flavouring oil, it can significantly increase the density of the oil phase without migrating into the aqueous phase, which is a risk commonly associated with low-molecular-weight weighting agents.

Ester gum can therefore be used as a stabiliser to ensure that fine suspended solids do not settle to the bottom of the beverage, but instead remain permanently and evenly distributed throughout the drink.

Gum base tackifier and plasticiser

Chewing gum base needs a certain level of tack so that it can bind with the coating sugars and flavours, and it must also provide elasticity and a cohesive, non-sticky texture during chewing. Ester gum is a thermoplastic resin and, when used together with the gum base, it increases both the tackiness and elasticity of the base system. This mechanism is essentially the same as the way industrial-grade ester gum is used in rubber compounding.

While providing tack to the chewing gum base, ester gum also acts as a plasticiser. By inserting itself between polymer chains, it increases the free volume of the molecules and thus lowers the glass transition temperature (Tg) of the gum base system. As a result, at oral temperature (around 37 ℃), the chewing gum maintains an appropriate softness and elasticity, shifting from a glassy state to a highly elastic state, so it does not feel too hard or too sticky on the teeth.

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What are the food safety risks of GEGR?

Ester gum is one of the food additives approved under the regulations of many countries, so it may be used as a food additive provided that it meets the relevant national specifications. For both Glycerol ester of gum rosin and Glycerol ester of wood rosin, the main focus of food safety debate has been on certain components with potential toxicological relevance. Specifically, these are glycerol monoesters, free resin acids and other neutral substances, for which expert panels have highlighted the lack of robust stability data and toxicological data.

		Glycerol ester of gum rosin	Glycerol ester of wood rosin (E445)
United States	Regulatory instrument	21 CFR § 172.735 – Glycerol ester of rosin	21 CFR § 172.735 – Glycerol ester of rosin & 21 CFR § 172.615 – Chewing gum base
	Status	Permitted (food additive)	Permitted (food additive)
European Union	Regulatory instrument	Not listed in Annex II to Regulation (EC) No 1333/2008	Annex II to Regulation (EC) No 1333/2008
	Status	N/A	Commission Regulation (EU) No 231/2012
Japan	Regulatory instrument	Food Sanitation Act (食品衛生法) / Consumer Affairs Agency (CAA) ; List of Designated Additives, Enforcement Regulations, Appended Table 1	Same framework; MHLW / CAA new-designation procedure
	Status	Permitted under the designation “Ester Gum” (No. 69 in Designated Additives list); covers glycerol esters of rosin broadly	Not separately designated; a petition was filed in 2006 but the FSCJ risk assessment was withdrawn on 3 February 2009
United Arab Emirates	Regulatory instrument	UAE.S 192:2019 (ESMA), by Codex GSFA reference	UAE.S 192:2019 (ESMA), by [Codex GSFA INS 445(iii)]
	Status	Uncertain — no Codex ADI; JECFA ADI withdrawn 2013	Permitted under Codex GSFA
Table 2. Regulatory Status of GEGR/GEWR as a Food Additive, read the full report.

In 2008, the EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS Panel) carried out a follow-up evaluation of Glycerol ester of wood rosin (E445) as a food additive^【5】. At that time, the Panel considered that it was not possible to complete a full safety assessment of GEWR. However, it also noted that the acceptable daily intake (ADI) previously established by JECFA was supported by the available experimental results.

In 2023, the EFSA Panel on Food Additives and Flavourings (FAF Panel) again assessed Glycerol esters of wood rosin (E445) as a food additive^【6】. The Panel concluded that there was no safety concern for the use of GEWR (E445), whether at the maximum permitted levels or at the reported use levels in foods.

Skin sensitiser classification

Ester gum is sometimes grouped together with skin sensitisers. This is because rosin acids and their oxidation products can trigger allergy through radical pathways or by forming hydroperoxides. Studies have shown that 7‑oxodehydroabietic acid is a key contact allergen in this group of substances^【7】.

In unmodified natural rosin, non‑oxidised resin acids on their own play only a very minor role in rosin allergy. In contrast, the sensitising potential of 7‑oxodehydroabietic acid is higher than that of the parent resin acids themselves.

Dehydroabietic acid (DHA) is one of the more stable resin acids found in rosin. Structurally, DHA is a tricyclic diterpene with one aromatic ring and two alicyclic rings, carrying a single carboxyl group. The term 7‑oxodehydroabietic acid refers to a derivative in which the 7‑position (C‑7) on ring B of DHA has been oxidised to a carbonyl or carboxyl group. This “dehydroabietic acid skeleton plus an additional oxygen‑containing functional group adjacent to the aromatic ring” gives the molecule higher polarity and a more reactive electronic structure.

The common features of low‑molecular‑weight contact sensitisers are as follows:

• They have a hydrophobic backbone, which allows them to pass through the lipid layer of the skin.
• They carry local electrophilic or nucleophilic sites that can take part in chemical reactions. These reactive sites enable them to form covalent or quasi‑covalent bonds with skin proteins and thereby act as haptens, or “partial antigens”.

Studies have shown that^【8】 compounds bearing epoxy or hydroperoxide groups on ring A or ring B display marked sensitising potential. In particular, 15‑hydroperoxydehydroabietic acid (15‑HPDA) is regarded as the most powerful primary sensitiser found in rosin^【9】. Once the 7‑position on ring B of DHA is oxidised, the polarity of the molecule increases significantly, making it easier for it to pass through the skin lipid layer and reach the basal layer of the epidermis.

In terms of sensitisation mechanism, abietane-type substances readily form unstable hydroperoxide intermediates in air through radical reactions. These intermediates can then undergo further oxidation at the 7‑position on ring B to give carbonyl groups, which are typical electrophiles. Such electrophilic centres can undergo Michael addition with cysteine (Cys) residues in skin proteins, forming stable covalent thioether bonds, or react with lysine (Lys) residues via Schiff base formation to generate imine structures^【10】.

When these exogenous chemicals act as haptens and bind to endogenous proteins, they alter the protein structure and form hapten–protein complexes. The immune system then recognises these complexes as foreign, which can trigger T‑cell‑mediated allergic contact dermatitis^【11】.

Free neoabietic acid (Neoabietic acid)

From an ideal safety perspective, the higher the content of triglycerides and diglycerides in ester gum, the better. Triglycerides are the least polar species and have the largest molecular size. In the gastrointestinal tract, they hydrolyse more slowly than free acids and monoesters, and they also find it harder to pass directly through biological membranes to cause irritation or sensitisation. From a nutritional standpoint, ester gum is not absorbed in the same way as fatty acids and can be regarded as a poorly absorbed, inert component.

Within the family of resin acid glycerol esters, there is another group of substances that has started to attract particular attention, even though their levels are very low. Free neoabietic acid has now been singled out by regulatory bodies. This term refers to neoabietic acid present in its free carboxylic acid form, and it represents a specific isomer within the resin acid fraction. Like other abietane‑type resin acids, it shares a tricyclic diterpene skeleton, with a single carboxyl group attached to a highly hydrophobic three‑ring hydrocarbon framework, giving a “monocarboxylic acid plus rigid hydrophobic backbone” small‑molecule structure.

Under ideal conditions, ester gum would be esterified as fully as possible to form diglycerides and triglycerides. However, it is unavoidable that a small amount of neoabietic acid remains unesterified and therefore exists in the free carboxylic acid form. Compared with the corresponding glycerol esters, these free acids have distinct properties:

• They do not need to be cleaved by digestive enzymes, so the barrier to hydrolysis is low.
• They carry a free carboxyl group, which makes them more likely to take part in acid–base reactions and covalent binding.
• In scenarios involving contact with skin or mucous membranes, they have a higher potential to cause sensitisation or irritation.

According to existing genotoxicity studies on resin acids present in pulp and paper mill effluents, free neoabietic acid has shown positive results in multiple Salmonella strains and in yeast assays, and is the only resin acid clearly demonstrated to be genotoxic. In contrast, no mutagenic responses have been observed for abietic acid, dehydroabietic acid, levopimaric acid, 7‑oxodehydroabietic acid, monochlorodehydroabietic acid, dichlorodehydroabietic acid, pimaric acid, isopimaric acid or sandaracopimaric acid^【12,13】. As a result, the level of free neoabietic acid is restricted to 0.05 wt.%. EFSA considers that, below this limit, there is no safety concern with respect to genotoxicity.

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Alternatives to ester gum

Weighting agents

In the food processing sector, food-grade ester gum is primarily used as a weighting agent or stabiliser in beverage emulsion systems, and as a tackifier or plasticiser in chewing gum bases. Alongside developments in the food industry, a number of alternatives to ester gum have been developed.

In traditional beverage emulsions, sucrose acetate isobutyrate (SAIB) can be used as a weighting agent ingredient. SAIB is a denser, viscous liquid with a neutral taste and odour that does not affect the flavour of the beverage. However, “weighting agent-free emulsion systems” are gradually replacing traditional beverage formulations.

Weighting agent-free emulsion systems no longer rely on weighting agents to adjust the density of the oil phase. Instead, they achieve long-term stability for cloudy beverages through emulsion structural design, particle size control, and the rheology of the continuous phase. By incorporating high-performance emulsifiers or hydrocolloids, such as gum arabic and modified starches, a thick adsorbed layer is formed at the oil-water interface, providing dual stabilisation through electrostatic repulsion and steric hindrance. Thickeners such as pectin and xanthan gum are also added appropriately to adjust the rheology.

Formulation characteristics of ester gum include the following:

• It increases the density of the oil phase.
• Its glassy resin structure enhances the mechanical stability of oil droplets.
• It contributes a slight cloudiness, which helps to create a cloudy visual appearance.

Tackifiers for gum base

Wrigley’s “Freedent” chewing gum range once attempted to avoid the use of ester gum as a tackifier^【14】. The aim was to reduce gum sticking to teeth, especially to minimise residues on dentures, so that denture wearers could also enjoy chewing gum. However, subsequent market feedback indicated that chewing gum made without ester gum showed a clear decline in both texture and flavour perception.

Today, gum base tackifiers can instead use more advanced modified rosins, such as Glycerol ester of hydrogenated gum rosin, pentaerythritol esters of rosin, or terpene resins. These food‑grade modified resins offer advantages over Glycerol ester of gum rosin in terms of stability, odour and sensitisation potential. For example, food‑grade Glycerol ester of hydrogenated gum rosin is characterised by a very light colour, high oxidative stability and low odour, and can deliver superior tack and heat resistance within the gum base system.

For example, terpene resins can be used together with microcrystalline wax to improve the “non‑stick to teeth” performance^【14】. This combination helps maintain a pleasant chewing texture. The terpene resin provides a stiff, low‑polarity resin backbone, while the microcrystalline wax contributes a low‑surface‑energy, easily slidable phase. Working together, they make the gum base surface feel drier and less prone to sticking to teeth. Compared with using ester gum, replacing ester gum with tannins and hardened oils tends to degrade the texture and flavour of the chewing gum.

Traditionally, chewing gum bases have used petroleum‑derived “plastic‑type” engineering polymers, such as polyisobutylene (PIB) and butyl rubber, as synthetic elastomers, combined with paraffin or microcrystalline wax to prepare the gum base. By 2026, the biggest global trend in the chewing gum market is the rapid shift towards biodegradable gum bases. Natural gum (chicle) combined with pine resin and beeswax, and other plant‑based ingredients, is expected to replace petroleum‑based rubber as the main component of gum base systems, especially under today’s increasingly tense geopolitical conditions.

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References

1. T/GXAS 001-2017 Resin ester.
2. GLYCEROL ESTER OF GUM ROSIN(TENTATIVE), FAO 74th JECFA (2011).
3. GLYCEROL ESTER OF WOOD ROSIN, Residue Monograph prepared by the meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 86th Meeting 2011.
4. 关于废止《松香甘油酯》等15项团体标准的公告，Guangxi Association For Standardization.
5. EFSA ANS Panel, Re-evaluation of glycerol esters of wood rosin (E 445) as a food additive, EFSA J, 2018.
6. EFSA FAF, Follow-up of the re-evaluation of glycerol esters of wood rosins (E 445) as a food additive, EFSA J, 2023.
7. S Sadhra et al., Identification of contact allergens in unmodified rosin using a combination of patch testing and analytical chemistry techniques, 1996.
8. B M Hausen et al., Contact allergy due to colophony (VII). Sensitizing studies with oxidation products of abietic and related acids, 1990.
9. A T Karlberg et al., Identification of 15-hydroperoxyabietic acid as a contact allergen in Portuguese colophony, 1988.
10. Steven James Enoch et al., Quantitative and mechanistic read across for predicting the skin sensitization potential of alkenes acting via Michael additio, 2008.
11. Itai Chipinda et al., Haptenation: Chemical Reactivity and Protein Binding, 2011.
12. Earle R. Nestmann et al., Mutagenicity of constituents identified in pulp and paper mill effluents using the Salmonella/mammalian-microsome assay, 1980.
13. E R Nestmann et al., Mutagenicity of resin acids identified in pulp and paper mill effluents using the Salmonella/mammalian-microsome assay, 1979.
14. 丸山孝 et al., Non-stick chewing gum containing terpene resin, JPS586454B2.