E425 - Konjac

At a glance

• What it is: A plant-based hydrocolloid (water‑binding gum) and soluble fiber from the konjac tuber.
• What it does: Thickens, gels, stabilizes, emulsifies, and holds moisture in foods.
• Common in: Noodles (shirataki/konnyaku), sauces, fillings, plant‑based meats, beverages, and fiber‑enriched foods.
• Label names: Konjac, konjac gum (E425i), konjac glucomannan (E425ii), glucomannan.
• Safety notes: Not allowed in jelly mini‑cups in the EU; small jelly cups with konjac have caused choking incidents.

Why is Konjac added to food?

Konjac is added because it binds water extremely well and creates smooth, stable textures. It can produce firm, elastic gels on its own or in blends, and it helps keep sauces from separating during shelf life. In EU law, E425 is specified as two forms—konjac gum (E425i) and konjac glucomannan (E425ii)—reflecting its use as a thickener, stabiliser, and gelling agent in foods.¹

What foods contain Konjac?

You’ll most often see konjac in:

• Traditional konnyaku blocks and shirataki noodles
• Reduced‑calorie and high‑fiber foods (for body and satiety)
• Sauces, soups, and gravies (for thickness and stability)
• Fruit fillings and bakery creams (to prevent weeping)
• Plant‑based meats and dairy alternatives (to improve bite and juiciness)
• Certain beverages and gels (to suspend particles and add mouthfeel)

Note: In the European Union, E425 is not permitted in jelly confectionery in mini‑cup form because of choking hazards.²

What can replace Konjac?

Depending on the job, food makers may swap in:

• xanthan gum for stable thickening at low levels
• guar gum for cold‑process viscosity
• locust bean gum or carrageenan for creamy, elastic textures
• gellan gum or agar for firm gels
• pectins for fruit systems and jams

Blends are common: for example, konjac with xanthan or carrageenan can fine‑tune body, gel strength, and freeze‑thaw stability.

How is Konjac made?

Konjac gum/glucomannan is obtained from the tubers of Amorphophallus konjac. The roots are cleaned, peeled, sliced, dried, and milled into flour. The material is then purified to concentrate glucomannan, yielding E425i (konjac gum) or E425ii (konjac glucomannan) as defined in EU additive specifications.¹ These specifications set identity and purity criteria (such as ash and moisture limits) for use in food.¹

Is Konjac safe to eat?

When used as intended in foods, konjac has established specifications in the European Union and is authorized in a variety of categories, with the notable exception of jelly mini‑cups.¹² Small, firm jelly cups made with konjac have been linked to choking incidents; the United States Food and Drug Administration (FDA) maintains an import alert for such jelly candies, and the EU prohibits E425 in jelly mini‑cups.³² As with other soluble fibers, large amounts can cause gas or bloating in some people.

Does Konjac have any benefits?

Glucomannan is a soluble dietary fiber. The European Food Safety Authority (EFSA) has evaluated health claims for glucomannan, concluding that:

• Glucomannan contributes to the maintenance of normal blood cholesterol levels when consumed under specified conditions.
• Glucomannan contributes to weight loss in the context of an energy‑restricted diet when consumed under specified conditions (for example, split doses totaling 3 g/day with plenty of water before meals).⁴

These opinions apply to glucomannan as a fiber ingredient, not specifically to every food use of E425, and they must be accompanied by directions for safe use (such as taking with water).⁴

Who should avoid Konjac?

• Children and anyone with swallowing difficulties should avoid jelly mini‑cups containing konjac and should not consume konjac tablets that can expand before swallowing.³⁵
• People with gastrointestinal narrowing (strictures) should avoid high‑swelling fiber supplements.
• If you take oral medicines, separate the timing because glucomannan fiber can reduce absorption; take medications at least one hour before or four hours after glucomannan supplements.⁵
• If you are new to soluble fiber, start with small amounts to reduce the chance of gas or bloating.

Myths & facts

• Myth: “Konjac jelly mini‑cups are safe for kids because they’re plant‑based.” Fact: The plant origin doesn’t remove choking risk; these products are restricted or banned in several jurisdictions.²³
• Myth: “More konjac is always better.” Fact: Excess fiber can cause digestive discomfort, and certain formats (like dry tablets) can be unsafe if not taken with enough water.⁵
• Myth: “Konjac works the same in every recipe.” Fact: Its texture depends on pH, temperature, ions, and partners like xanthan gum or carrageenan, so formulators adjust blends and use levels.

Konjac in branded foods

You’ll find konjac on labels as “konjac,” “konjac gum,” “glucomannan,” or “konjac flour.” It appears in:

• Shirataki noodles and konnyaku blocks
• Fiber‑enriched beverages and meal replacements
• Low‑calorie fruit gels and desserts (note: mini‑cup formats with konjac are restricted in the EU)
• Plant‑based meat and dairy alternatives
• Sauces, soups, and ready meals

To spot it quickly, scan the ingredient list for E‑numbers “E425,” “E425i,” or “E425ii.”

References

Footnotes

1. Commission Regulation (EU) No 231/2012 laying down specifications for food additives — European Commission. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32012R0231 ↩ ↩² ↩³ ↩⁴

2. Regulation (EC) No 1333/2008 on food additives (restrictions for jelly confectionery) — European Parliament and Council. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32008R1333 ↩ ↩² ↩³ ↩⁴

3. Import Alert 33-15: Detention Without Physical Examination of Jelly Cups Containing Konjac — U.S. FDA. https://www.accessdata.fda.gov/cms_ia/importalert_621.html ↩ ↩² ↩³

4. Scientific Opinion on the substantiation of health claims related to glucomannan (Article 13(1)) — EFSA Journal. https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2010.1798 ↩ ↩²

5. Glucomannan — MedlinePlus, National Library of Medicine (NIH). https://medlineplus.gov/druginfo/natural/1006.html ↩ ↩² ↩³