The manufacturing of meat products like raw sausages, frankfurter-type cooked sausages and

variations of them, is one of the most complicated processes in food production today. The
slightest deviation of the raw materials or the conditions applied results in a quality variation of
final product.
The ripening process as well as the curing and red color formation process of sausages are highly
dependent upon the pH of the medium in which they take place. Under the influence of a lower pH,
these processes unwind faster and are more complete in the end. The ripening time greatly
increases the costs of manufacturing the product. This is why about 30 years ago the souring
agent GDL was introduced to accelerate the relatively slow bacteriological acidification.
In meat product GDL becomes hydrolysed to gluconic acid under the influence of meat's own
water content, gradually decreasing the pH of the system in a controlled manner. GDL reaches its
lowest pH after approx. 40 to 60 minutes or more, depending on the substrate, the concentration of
GDL and the temperature applied. The speed of hydrolysis and thus the speed of acidification can
be accelerated by increasing temperature.

Following figure shows the typical pH variation with time at various concentrations of GDL,
determined in water.

Typical pH variation with time of Gluconal® GDL solutions in water, depending on concentration
(1% and 5% w/w) and temperature (20 and 40oC).

GDL In Cooked Sausages

Cooked sausages are mainly known as "frankfurters", but there exists various types and variations
of these frankfurter-type meat sausages like knackwurst, wiener, thuringer, special types of salami
and mortadella, mettwurst, teawurst etc. Additionally, there are many regional variations, however
all of these frankfurter-type sausages are made from fresh meats, cured during processing, fully
cooked and smoked.
Cooked sausages consist mainly of raw meat, fat and water and various additives like salts,
phosphates, glycerides, proteins, food acidulants, spices and flavors. These additives have to
assure a safe and successful manufacturing process, a high-quality finished product, stability and
cut resistancy of the protein-fat-water emulsion even when scalded or cooked several times.
Most cooked sausages belong to the category of cured sausages, which means that they have
been cured for good red color development with nitrites. All reactions underlying the curing and
red color formation processes are highly dependent upon the pH of the medium in which they take
place. Under the influence of a lower pH, these processes unwind faster and are more complete at
the end.
Common frankfurter-type sausage preparations have a pH of 5.8 or slightly above. The addition of
agents promoting acidity has become a frequently adopted practice. The preferred choice for such
functional ingredients is GDL since it allows a well-controlled slow drop of the pH value.
GDL can be added together with all other additives directly to the grinded meat mass, before the
sausages are filled into casings, cooked and smoked. An addition of 0.1 to 0.2% GDL (max. 0.3%,
otherwise the final product becomes too sour) should be sufficient in order to reach the desired pH
value.
When GDL is used in frankfurters along with reducing compounds such as sodium erythorbate,
GDL promotes faster development of color during smoking. Smoking house time can be reduced
by as 50%, and the finished frankfurters are said to exhibit less shrinkage and longer shelf life.
The use of GDL
- permits the reduction of nitrites
- accelerates color development and improves color stability
- prolongs shelf-life

GDL In Raw Sausages

The production of raw sausages by drying and ripening are said to be one of the oldest methods
for the conservation of fresh meat. Today, raw sausages are made from fresh meats that are cured
during processing and may or may not be smoked. The most famous raw sausages are the salami,
pepperoni, landjaeger etc.
Raw sausages contain next to the fresh meat various additives like salts, sugars, spices, nitrites,
starter cultures and/or food acidulants like GDL which guarantees the production of a stable
product that meets consumer expectations.
The key to successful production of dry sausages depends on the timely lowering of the pH of the
sausages during processing. The pH of raw meat may be as high as 6.4 and the final pH of
fermented sausages will typically range from about 4.8 to 5.4. Traditionally the pH value for dry
sausage ripening is adjusted by lactic acid producing starter cultures which are added to the
sausage meat. This fermentation lasts several days depending on the temperature used. A quicker
dry sausage ripening can be obtained by using GDL. With GDL the pH can be lowered directly in
the sausage emulsion or mass and so the development of pathogen and spoilage causing
microorganisms can be reduced. For the ripening process of raw sausages, GDL can also be used
in combination with traditional starter cultures in order to get the specific aroma of a brand. The
low pH value obtained with GDL supports the development of these starter cultures. The low flavor
profile of GDL itself makes it possible to reach lower pH values withourt influencing the
characteristic aromatic flavors of sausages. Due to the low pH the shelf life of sausages can be
improved.
GDL can be added together with all other additives to the grinded meat mass before the sausages
are filled into casings, dried and eventually smoked. The addition of 0.5-1.0% GDL to the sausage
meat permits a sure and simple production of spread or cut resistant sausages.
To nearly all types of sausages, nitrite is added directly to the sausage batter in order to get the
characteristic cured-meat color, to improve the flavor and to provide bacteriostatic properties. In
an environment acidified with GDL, the nitrite is much better used and as a result the ripening
process to reach cut-resistancy is much earlier terminated and the color is more intensive than
would be the case without the addition of GDL. Furthermore the necessary quantity of nitrite can
be reduced which is desirable from the dietetic point of view.
The use of GDL ensures
- shortening of the ripening process resulting in higher yields
- significant reduction of risk of bacterial contamination
 - longer shelf-life
- reduction of necessary nitrite
- improved firmness and cutting characteristics
- improved color stability

Reference: Glucona America Inc.