Glucono delta-lactone
A naturally occurring acid derived from glucose, used to set tofu, cure meat, and gently acidify baked goods and dairy.
What is it?
Glucono delta-lactone (GDL) is a cyclic ester (lactone) of gluconic acid, which itself is produced by the oxidation of glucose. It occurs naturally in honey, fruit juice, and wine. Commercially it is made by fermenting glucose using the mould Aspergillus niger, then crystallising the product. When dissolved in water it hydrolyses slowly to gluconic acid, releasing acidity gradually.
What does it do?
GDL releases acid slowly and predictably as it dissolves. That gradual acidification is its main technical value. In tofu production it causes soy protein to coagulate evenly into a smooth curd without the graininess left by faster-acting mineral coagulants. In cured meats and fermented sausages it lowers pH quickly enough to inhibit spoilage bacteria and stabilise the pink colour from curing salts. In baking powders and self-raising flour it acts as a slow-release acid that reacts with bicarbonate to produce carbon dioxide, giving a more even rise than faster acids. In cheese and cream desserts it sets texture gently by acidifying at room temperature.
Where you will see it
Silken and soft tofu, frankfurters and cooked sausages, fresh and cured pork products, sourdough-style breads, baking powder, some cream-set cheeses, reduced-fat spreads, and certain fruit preparations. On a UK ingredient label it appears as glucono delta-lactone, glucono-delta-lactone, or E575.
What the science says
Metabolism and safety profile
Once GDL hydrolyses to gluconic acid in the body, it is metabolised through normal glucose pathways. Gluconic acid is a naturally occurring substance present in fruit and honey and is produced endogenously. Regulatory reviews have not identified organ-specific toxicity, carcinogenicity, genotoxicity, or reproductive effects at food-relevant intakes. There is no IARC classification for glucono delta-lactone.
No adverse effects were identified in repeated-dose animal studies at doses well above those achievable through food use; no genotoxicity was found in standard assays.
Gluconic acid and its salts are metabolised via normal carbohydrate pathways; the body also produces gluconic acid endogenously from glucose oxidation.
Ongoing EFSA re-evaluation
All food additives authorised in the EU before January 2009 are being systematically re-evaluated by EFSA. Glucono delta-lactone (E575) is included in the group covering gluconic acid and related gluconates (E574-E579). As of 2024 EFSA had issued a call for data on this group, meaning the formal opinion had not yet been published. No preliminary adverse signal has been publicly announced for this group.
EFSA issued a call for data on gluconic acid (E574) and related food additives including E575-E579 as part of the systematic re-evaluation of legacy food additives.
Where it stands with the regulators
Who should be careful
No specific population group is required by law to avoid E575. People managing very low-acid diets for dental erosion or acid reflux may wish to note that GDL acidifies food; they can look for glucono delta-lactone or E575 on the label.
The honest read
Glucono delta-lactone is one of the more chemically straightforward food additives. It is derived from glucose, breaks down to an acid the body already handles, and appears in published toxicology reviews without flagged concerns at food-relevant intakes. The ongoing EFSA re-evaluation is a routine regulatory process covering hundreds of legacy additives, not a response to a specific safety signal for this substance. The re-evaluation opinion has not yet been published, so the final regulatory picture is not closed.
Related additives
Common questions
Is E575 banned in the UK?
No. Glucono delta-lactone (E575) is an approved food additive in both the UK and the EU, permitted for use in a range of foods including meat products, tofu, baked goods, and dairy.
Is E575 currently under any safety review?
Yes, as a routine matter. EFSA is systematically re-evaluating all food additives authorised in the EU before 2009. E575 sits in the gluconic acid group (E574-E579), for which EFSA issued a call for scientific data in 2024. No adverse preliminary finding has been announced; the formal opinion has not yet been published as of mid-2026.
What foods contain E575?
Common sources include silken tofu, frankfurters and cooked sausages, baking powder, some cream-set cheeses, and certain fruit preparations. It appears on labels as glucono delta-lactone, glucono-delta-lactone, or E575.
Is E575 vegan?
The commercial production process uses glucose fermented by the mould Aspergillus niger, making it plant-derived and suitable for vegan diets. The foods it is used in, such as meat or dairy products, may not themselves be vegan.
Sources
- UK FSA regulated products database: E575 glucono delta-lactone
- UK Food Standards Agency: Approved additives and E numbers
- EFSA call for data: re-evaluation of gluconic acid (E574) and related food additives (E575-E579)
- EU Regulation 1333/2008 on food additives (Annex II)
- JECFA monograph: Glucono delta-lactone
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