What is GDL?

GDL is a chemical that achieves what bacteria does in fermented meat products. In the end, it acidifies the meat which results in a quicker drying process and acts as an effective barrier against bacteria growth (Bertelsen et al., 1995). Both Juncher et al. (2000) and Samelis et al. (2002) found GdL effective in preventing growth of Listeria monocytogenes when used in combination with lactate in emulsion type meat products. Juncher et al. (2000) also found that the lowering of pH by GdL together with lactate significantly improved the oxidative stability of the meat product and resulted in higher a-values (red colour).”

A few days ago Kobus suggested he use GDL in bacon production. At first, I was sceptical, but the more I think about it, the more excited I become. I have for years maintained that bacon should be produced made in conjunction with an acidification of the meat matrix. My primary reasoning was that in micro-control, everything works better under slightly more acidic conditions. (Nitrite’s Anti-Microbial action) It will also accelerate drying.

Understanding its activity

“GDL is a cyclic compound that releases gluconic acid slowly when the GDL is hydrated with the meat moisture. When GDL is added to the meat mix, the product must be stuffed and processed immediately, before significant acid formation. The rate of acid generation is dependent upon moisture content and temperature.” (Processing Procedure)

Acidification of cured meats

The problem with a more acidic meat matrix is that it will cause an increased depletion of nitrites which will affect curing. In conventional bacon production way around that is to add the acidifiers at the end of the tumbling phase.

The slow-release nature of GDL offers an even better option than the organic acids that I initially worked with. Normally GDL is used, for example, when salami is made but without the right humidity control equipment.

Its action of slow acidification is due to “its slow hydrolysis to gluconic acid (which takes place gradually over the forty to sixty minutes after dissolution), it provides a gradual, progressive and continuous decrease of pH to equilibrium. Accordingly, it is used as a slow release acidulant.

During its hydrolysis, its initial sweet taste becomes only slightly acidic, making the final flavor of an aqueous solution much less tart than that of other acidulants Being acidic, it adds a tangy taste to foods, though it has roughly a third of the sourness of citric acid.” Heat speeds up its hydrolysis. (Biokimkimya)

When fermented products are made, it replaces starter cultures, which accelerate the process by eliminating the fermentation period. Chemical acidulants, therefore, provide a slower release of the specific acid (as opposed to addition of the straight acid) into the meat mix in order not to result in premature acidulation before the meat matrix is established. These types of acidified product are processes, direct heated and cooked following formulation. (Biokimkimya)

Alternatives to Gdl

Alternatives to Gdl are encapsulated acids. With encapsulated acidulants, “the active acid ingredient (e.g., lactic, citric, fumaric, GDL/gluconic acid) generally is encapsulated with fat material that melts at varying temperatures, thus releasing the acid. Thus, acidification occurs during the cooking process after the meat matrix has been established. The rate of acid release is dependent upon the specific particle size, fat coating, temperature, other fats in the formulation, physical processing, and processing temperature. (Processing Procedure)

A typical process for chemically acidified summer sausage would consist of formulation, followed by heating at 115°F (46.1°C), 74% RH, and then cooking to 165°F (73.9°C) internal temperature. The entire process takes 6-7 hours versus a 12-18 hour fermentation process. (Biokimkimya)

Insights from Igor

Igor offers the following insights.

“GDL is made from dextrose in microbial fermentation. It is also made by fermenting rice. In water, it hydrolyzes to gluconic acid very quickly. Inside our bodies, it is completely metabolized and is non-toxic. It is found in honey, fruit juice, wine and a number of fermented foods. A “natural” food acid, it is only about a third as sour as citric acid and lowers pH, helping to preserve food from deterioration by enzymes and various microorganisms. Today, it is used in making cottage cheese, tofu, bakery products, and yup… some fast-fermented sausages.”

He discusses it further in term if the production of Landjäger.

GdL causes a fermentation process that is easier to control if the user is less skilled or lack a climate chamber with possibility of thorough temperature and humidity control. And because Landjäger is a smaller calibre fermented sausage than the average calibre 60 salami there is also a better chance that things will work out as expected. Also because the GdL denatures the protein of the meat fibre in a rather effective (some would say brutal) way -depending on dosage, you may find it easier to obtain the rectangular shape which is the hallmark of this sausage (…together with the caraway :mrgreen: ).

GdL is a good helper though personally, I am not that much of an advocate of GdL as I frequently experience that high dosage/overdose leads to a woody and hard texture once the sausage becomes (too) dried out and at this point, an annoying metallic off-taste may be observed too, which is offensive for some people but indifferent for others.

For my taste buds, the GdL also seems to enhance the saltiness of the product if salt dosage is around 2,4% or higher.

But for some types of sausages, slight saltiness ain´t a drawback: After all Landjäger is a kind of backpackers snack-salami that goes well with a Bavarian-style beer. Try it with a Hefeweisse from Paulaner or Meisel.

However, as Baden-Württembergs seem to claim that the Ländjager of their region is especially good you could also try it with a Pinot Noir (as the German Spätburgunder wines might be hard to come by in your vicinity)

Landjäger is Swiss in origins.

So what is to be considered the right dosage of GdL?

The average dosage in Germany is app. 0,8% for salami type sausages of calibre 60 because with this much you are sure to ram down pH below 5.0 withing a short time.

Compared to starter cultures there is a shorter lag phase and the pH drop is steep (that´s why you should not use Cure#2). But you will probably also notice the aforementioned drawbacks in consistency and taste after some time of drying/maturing.

With 0,4 % GdL you will still have the drop-down well below pH 5,3, so I would recommend this as a starting point dosage for your first experiment with GdL in a small calibre. And my bet is that the off-taste will be so close to unnoticeable that no one will complain.

Actually during my time at Chr. Hansen we promoted the combination of 0,4% GdL and T-SPX for small scale producers who did not possess real climate chambers but could at least leave the sausages to hang in a closed smoking chamber with high humidity inside. And it usually worked well, though consistency eventually would become slightly less elastic and a bit woodier than with starter culture alone”

Thank you Igor, the Dane, for your insights.

Proposed tests for bacon

I propose starting with 0.1 and 0.4% of FP to be added in the last few minutes of tumbling. Remember Igor advised that at 0.4%, the pH will drop below 5.3 which is a threshold level. Test both. Pay close attention to the rate of drying.

While we are doing tests, why don’t we take Juncher, and colleagues up on their work which showed that lowering of pH by GdL together with lactate significantly improved the oxidative stability of the meat product and resulted in higher a-values (red colour). For sure we will now be in a region below 5.3 pH.

I suggest we buy a pH meter and test the meat before injection/ tumbling after the Gdl/ lactate has been added, and after smoking. I suggest we manipulate the pH of the meat to levels of around 5.3 since reducing the pH below this point will increase the rate of nitrite depletion  (private communication with Dr. Tompkin) and 5.3 has been shown to be a threshold. On the other hand, one could do the following for conventional bacon;

– Prepare a salami mix with spices and curing salt, excluding the Gdl

– Inject, paddle mix/ tumble

– Rest for 24 hours

– Paddle mix/ tumble again for 10 minutes and in this step, add Gdl. Test ratios of between 0.1 and 0.4%.

For dry curing, mix spices and Gdl together with curing salts and cure as normal.

– cure

– mature

– Short drying.

– Smoking

– Resting

Ising Gdl Should speed the process up quite a bit.

Alternatively, I would start with the Gdl and the curing mix and test different levels of Gdl in FP and measure the pH of the meat every day. I would try 0.1% in FP.

Testing pH will tell us if it drops below 5.3, and we can reasonably suspect that from there onwards, it is affecting curing, but curing may already be at an acceptable level. All will be revealed!

Care must be taken not to over dry the bacon.

For curing, I could simply add Prague Powder, sodium erythorbate and brown sugar with the Gdl with the spices. I would leave out the phosphate for the trails. The spice supplier should be able to provide a sample pack. Later, if need be and acidic phosphate can be considered, but I am sure its very expensive.

In the final step, I would regularly test the pH and take care that it does not drop so far as to give the pork an off acidity taste. I would adjust the Gdl levels to the total expected time before the process is complete.

Artisan Curers’ Objection Against Salami with Gdl

Fermentation in salami comes from 2 broad types of bacteria. Lactic acid bacteria, obviously, produce acid which lowers pH. However, many strains also produce bacteriocins that are effective in controlling the growth of pathogens and produce enzymes to combat rancidity. The other type of bacteria is micrococci that break down fats and proteins – the process that is critical to flavour. They also breakdown nitrate (in cure 2) into nitrite, which is critical to the formation of colour. So there is a lot more going on than just the pH drop for food safety. GDL is typically only used in mass production operations, where 24 hour saved production time increases profits. However, these, products are insipidly lacking in flavour and colour (think supermarket deli salami). My advice is to learn all you can about fermentation, and perfect your fermentation process. When you think about it, it’s only adding a couple of more days onto a process that is several weeks long anyway, and it is critical to making great salami.” (Josef Wantschik on the use of GDL)

Tommy Greiner, adds that he has “a biochem background and the flavour science makes him question the use of Gdl. He brews a lot of mixed fermentation sour beer (several bacteria strains and wild yeasts) that takes at least 8 to 12 months and there is a stark difference versus 2-day kettle-soured (and even some commercial beer that have lactic acid directly added).”


An overall exciting suggestion, Mr Kobus! 🙂


Søltoft-Jensen, J., Hansen, F.. 2005. New Chemical and Biochemical Hurdles, Emerging Technologies for Food Processing.

Josef Wantschik and Tommy Greiner on the use of GDL

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