E388 - Thiodipropionic acid

At a glance

• Names: E388, thiodipropionic acid (often shortened to TDPA)
• What it does: Antioxidant that helps keep fats from going rancid
• Where it shows up: Rare on ingredient lists today; related esters are more typical in food packaging materials
• Source: Made synthetically
• Common stand‑ins: ascorbic acid, tocopherols, citric acid, extracts of rosemary, and synthetic antioxidants like BHA, BHT, or TBHQ
• Regulations: Allowed uses vary by country and by product type; always check local rules

Why is Thiodipropionic acid added to food?

Manufacturers use antioxidants to protect flavor, color, and texture during shelf life. When fats and oils react with oxygen, foods can develop off‑odors and taste “rancid.” Thiodipropionic acid can help slow these reactions, especially in fat‑rich products, by interfering with the chain reactions that drive oxidation.

What foods contain Thiodipropionic acid?

You are unlikely to see “thiodipropionic acid” on modern ingredient lists. Historically it has been discussed as an antioxidant for fat‑rich foods, but in practice other antioxidants are far more common on labels, such as BHA, BHT, TBHQ, ascorbic acid, tocopherols, or extracts of rosemary. Related esters of thiodipropionic acid—dilauryl thiodipropionate and distearyl thiodipropionate—are more often used in food‑contact plastics than as direct food ingredients.

What can replace Thiodipropionic acid?

• Natural options: ascorbic acid, tocopherols, citric acid, and extracts of rosemary
• Synthetic options: BHA, BHT, TBHQ, or propyl gallate
• Process choices: Excluding oxygen, using light‑proof packaging, lowering storage temperature, and controlling metal traces also reduce oxidation

How is Thiodipropionic acid made?

Thiodipropionic acid is a small organic molecule that links two propionic acid groups with a single sulfur atom, forming a “thioether” bridge. It is produced by chemical synthesis and sold as a fine solid for use in industrial applications. Chemical identity and synonyms are documented in public databases maintained by the U.S. National Institutes of Health (NIH).¹

Is Thiodipropionic acid safe to eat?

Safety and permitted uses depend on the country and the specific application. In the United States, closely related esters—dilauryl thiodipropionate (DLTDP) and distearyl thiodipropionate (DSTDP)—are authorized as antioxidants in certain food‑contact polymers under the Code of Federal Regulations (CFR).² Rules for specific plastics also point to the antioxidant list in 21 CFR 178.2010, tying allowable additives in those materials to that section.³ These authorizations for packaging do not automatically mean thiodipropionic acid itself, or its esters, are permitted as direct food ingredients in every food. Always check the current rules for your market and product type (for example, via FDA’s Food Additive Status List in the U.S.).⁴

Does Thiodipropionic acid have any benefits?

When used where allowed, thiodipropionic acid can:

• Help keep oils and fats from oxidizing, supporting flavor and aroma
• Protect sensitive vitamins, colors, and aromas from oxygen damage It is often paired with other antioxidants because combinations can work better than single ingredients in some foods.

Who should avoid Thiodipropionic acid?

• People who prefer to avoid less common additives may choose products that use alternatives such as ascorbic acid, tocopherols, or extracts of rosemary.
• If you must follow specific dietary or regulatory guidance (for example, during pregnancy, for infant foods, or for medical diets), check local rules and ask a healthcare professional.

Myths & facts

• Myth: Thiodipropionic acid is the same as DLTDP or DSTDP.
  Fact: They are different. DLTDP and DSTDP are esters of thiodipropionic acid and are commonly authorized as antioxidants in certain food‑contact plastics in the U.S., under a separate rule.²
• Myth: “Contains sulfur” means it is a sulfite.
  Fact: Thiodipropionic acid contains sulfur in an organic thioether; it is not a sulfite preservative.

Thiodipropionic acid in branded foods

You will rarely find E388 listed on retail ingredient labels today. If you are checking a specific product:

• Read the ingredient list for named antioxidants.
• Look on the brand’s technical or FAQ pages for details on antioxidants used.
• For packaging, suppliers may disclose the presence of DLTDP or DSTDP in technical data sheets rather than on the food label.

References

Footnotes

1. Thiodipropionic acid — PubChem, National Institutes of Health (NIH). https://pubchem.ncbi.nlm.nih.gov/compound/Thiodipropionic-acid ↩

2. Antioxidants and/or stabilizers for polymers — 21 CFR 178.2010, U.S. Food and Drug Administration (FDA). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-178/section-178.2010 ↩ ↩²

3. Olefin polymers — 21 CFR 177.1520, U.S. Food and Drug Administration (FDA). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-177/section-177.1520 ↩

4. Food Additive Status List — U.S. Food and Drug Administration (FDA). https://www.fda.gov/food/food-additives-petitions/food-additive-status-list ↩