Glucono Delta-Lactone

Also known as GDL or D-gluconic acid-δ-lactone

What is Glucono Delta-Lactone (GDL)?

Glucono delta lactone (GDL) is a natural organic acid that is part of chemical leavening systems. It reacts slowly but steadily with sodium bicarbonate and is fully activated by oven heat.¹

It is also a key component in reduced sodium raising agents used in the production of sweet baked goods, such as cakes and muffins. Two main properties differentiate GDL from other acid leaveners:

• Its slow and progressive hydrolysis and pH drop make it a slow release acidifier
• Due to its initial sweet taste, hydrolysis of GDL results in lower tartness than other acidifiers.

Origin

Glucono-delta-lactone is an inner, neutral cyclic ester of gluconic acid produced by acid fermentation of glucose. It occurs naturally in honey, wine, fruit juices and many fermented products.

Function

GDL is a fine white powder which dissolves quickly in water. Upon hydration, GDL slowly breaks down into gluconic acid, which then reacts with baking soda to produce carbon dioxide. The hydrolysis process is slow at cold/low temperatures but is accelerated by heat during baking.¹

Leavening reaction of GDL with baking soda:

C6H12O7 + NaHCO3 → C6H11O7Na + H2O + CO2

Gluconic Acid + Baking Soda → Sodium Gluconate (salt) + Water + Carbon Dioxide

In food, glucono delta lactone functions as a curing, pickling and leavening agent. It also has the ability to control pH by increasing the acidity of the product. From a nutritional standpoint, GDL is completely metabolized in the body like any other carbohydrate, providing 4 kcal/g.

Commercial production

GDL is commercially manufactured from renewable carbohydrate sources by microbial fermentation followed by downstream processing. During the process, GDL is produced along with gluconic acid by glucose fermentation. The resulting product is a fine, white, crystalline powder freely soluble in water. GDL is practically odourless and has a slightly sweet taste.¹

Application

The delayed or slow rate of reaction of glucono delta lactone makes it ideal for:

• Refrigerated or frozen dough products
• Premium cookies
• Cake doughnuts
• Quick bread type products (e.g. canned dough and scones)

Using GDL can be cost-prohibitive in some applications. This weak organic acid has a low neutralizing value (45 grams of sodium bicarbonate neutralized by 100 g of the acid) implying that higher amounts of GDL are required to neutralize the baking soda completely and release optimum amounts of gas.

During conversion to gluconic acid, GDL becomes only slightly tart or acidic (about 33% of the sourness of citric acid). Therefore, it does not change the flavor profile of the formulated baked goods. The acidification effect also provides a preservative effect through pH drop, extending the mold-free shelf-life of the product.

Characteristics of GDL and other leavening acids

* Rate of Reaction (ROR) at 27°C from the start of batter/dough mixing

The ROR concept is used as a measure of how fast the leavening acid reacts with the base (e.g. sodium bicarbonate) to release carbon dioxide in a dough or batter under controlled conditions of temperature, pressure and water activity.^2,3

FDA regulation

Glucono delta lactone is recognized as a GRAS (generally regarded as safe) additive. The FDA permits the use of GDL in food without limitation other than current good manufacturing practice (GMP).⁴

References

1. Chung, F.H.Y. “Bakery Processes, Chemical Leavening Agents.” Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, Inc., 2000, pp. 1–8.
2. Figoni, P.I. “Leavening Agents.” How Baking Works: Exploring the Fundamentals of Baking Science, 3rd edition, John Wiley & Sons, Inc., 2011, pp. 300–322.
3. Heidolph, B. B. 1996. Designing chemical leavening systems. Cereal Foods World 41:118–126.
4. U.S. Food and Drug Administration, CFR – Code of Federal Regulations Title 21, Part 184 “Direct Food Substances Affirmed as Generally Recognized as Safe”, https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=184&showFR=1, Accessed 25 May 2020.