Sucuk, a dry fermented sausage type, is produced in two ways; traditional and industrial. Traditional production is generally carried out in small-scale enterprises without starter cultures, and sucuk is ripened under natural conditions.
In industrial production, starter cultures are used for controlled fermentation. Air conditioning units that can automatically control temperature, air flow and relative humidity are used for fermentation and drying processes.
This product, produced using the main process steps of fermentation and drying, is called “fermented sucuk,” according to the Turkish Food Codex Meat and Meat Products Communiqué that came into force in 2012.
Fermented sucuk is defined as “a fermented meat product without heat treatment, with a cross-sectional surface having a mosaic appearance, where the moisture content is reduced to 40% or less by chopping bovine and ovine meat and fat, mixing it with flavorings, filling it in natural and artificial casings, applying drying and fermentation processes under certain conditions“.
In the same communiqué, the semi-dry fermented sausage type produced by applying the main process steps of fermentation, heat treatment and drying is called “heat-treated sucuk.”
After a short-term fermentation step in heat-treated sucuk, a heat treatment process is applied so that the core temperature is at least 68°C (at least 72°C for poultry meat).
Since heat treatment application facilitates the supply of reliable products, producing heat-treated products is preferred in the industry. However, starter cultures are also needed for controlled fermentation to produce heat-treated sausage. (For more detailed information about starter cultures, see Starter Cultures; Definition, Types and Characteristics)
In addition to the acid formation rate and degree of lactic acid bacterial strains used as starter cultures, their ability to produce bacteriocins or bacteriocin-like metabolites also plays an important role. (For more detailed information about lactic acid bacteria, see Lactic Acid Bacteria; Definition, Classification and Characteristics)
Since there is no heat treatment in fermented sucuk production, selecting lactic acid bacteria strains is more critical than heat-treated sucuk.
In other words, the acid formation rate and degree of lactic acid bacteria are critical in ensuring product safety in this product. However, the antagonistic activity of the strains to be used against foodborne pathogens is an additional factor in ensuring product safety.
In addition to product safety, the strains to be used also play an essential role in the development of the sensory properties of the product, mainly taste and aroma. The use of starter culture is also of great importance in terms of standard product production.
In many countries, strains isolated and identified from traditional products have been used in starter culture production, and research in this direction continues.
In addition to lactic acid bacteria, catalase-positive cocci, mold (Penicillum nalgiovense) and yeast are commonly used microorganisms as starter cultures in the meat industry.
While Lactobacillus and Pediococcus genus lactic acid bacteria and catalase-positive cocci are preferred as starter cultures in dry fermented sausages such as fermented sausages (salami, Rohwurst, Chorizo, etc.) in Europe, only Lactobacillus and Pediococcus genus lactic acid bacteria are preferred in the USA.
Fermented sucuks are characterized primarily by the decreasing pH value and the unique aroma obtained by the fermentation of lactic acid bacteria. Lactic acid bacteria are an important group that contributes to product safety by inhibiting foodborne pathogenic bacteria and improving the sensory properties of fermented foods.
Lactic acid bacteria, found spontaneously or as a starter culture in fermented meat products, create acid and contribute to both the drying of the product and the inhibition of pathogenic and spoilage microorganisms.
Today, unique strains selected for different fermented products are marketed as preparations and widely used in industrial production. The primary source of the strains in question is traditional products.
Many lactic acid bacterial strains have been isolated and identified from sucuk, a traditional fermented meat product. Lactobacilli, the largest group of lactic acid bacteria with more than fifty species, are widely found in traditional fermented products and industrial starter preparations.
In fermented meat products, the Lactobacillus plantarum species come to the fore due to its reliability among lactobacilli, ability to quickly adapt to various environments and use different sugars and probiotic properties.
Lactobacillus plantarum is isolated from fermented sucuks at different rates depending on the fermentation conditions. It is known that Lactobacillus plantarum is the dominant species in fermented sausages at ripening temperatures higher than 25°C, and Lactobacillus sakei and Lactobacillus curvatus are the dominant species at lower temperatures.
For the Lactobacillus plantarum strain to be effective in fermentation, it is essential to determine its technological properties and adapt it to production conditions. Although meat-derived L. plantarum isolates vary between strains, they generally grow at 15°C and 45°C, but cannot grow at 4°C.
It is stated that Lactobacillus plantarum species can survive in environments containing 6.5-10% NaCl. Lactobacillus plantarum strains that are weak in lipolytic activity are generally capable of hydrolyzing casein, although they show weak proteolytic activity.
In addition, the biogenic amine-forming ability of the lactic acid bacterial strains is an important factor in starter culture selection.
Studies conducted on Lactobacillus plantarum strains isolated from fermented sausages reported that the strains examined did not have decarboxylase activity.
Another feature sought for their use in meat products is the configuration of the lactic acid they produce. Since D(-)-lactic acid cannot be hydrolyzed by lactate dehydrogenase in humans, strains producing L(+)-lactic acid are preferred as starter cultures.
In addition, strains capable of producing acetoin from glucose are reported to cause undesirable aroma in the product.
Lactobacillus plantarum strains can increase product reliability when used as starter cultures, as they adapt better to the environment and have a higher probability of preventing possible microbial contamination, thanks to their antagonistic activities and suitable technological properties.
The antagonistic effects of lactic acid bacteria occur through some of the final metabolites they produce, antibiotic-like products, bacteriocins and bacteriocin-like metabolites.
Bacteriocins are bioactive compounds in protein structure produced by bacteria with bactericidal or bacteriostatic effects. It has been suggested that bacteriocins, which are effective on closely related strains, are also effective on foodborne Gram-negative pathogens.
The first bacteriocin whose use was legally permitted in 1988 was nisin, produced by Lactococcus lactis spp. lactis.
Today, pediocin PA-1/AcH, produced by a Pediococcus strain, and enterocin AS-48, produced by Enterococcus faecalis, are also used commercially.
After the discovery of nisin, produced by lactic acid bacteria, in the 1920s, many different bacteriocins were identified.
Bacteriocins and bacteriocin-like metabolites have gained importance as potential food preservatives because they generally have high-temperature stability, can maintain their activity at acidic and neutral pH values, and are sensitive to proteolytic enzymes in the digestive system.
Bacteriocins can be added directly to food, or this effect can be achieved by the starter cultures used in foods producing bacteriocins or bacteriocin-like metabolites at a level that prevents the development of spoilage microorganisms.
There are many studies examining meat-derived Lactobacillus plantarum isolates as bacteriocin producers. The literature has reported that using bacteriocin/bacteriocin-like metabolite-producing lactic acid bacteria such as Lactobacillus plantarum as starter culture/protective culture will contribute to product safety.
By choosing Lactobacillus plantarum strains originating from traditional products as starter culture or protective culture, significant advantages can be achieved regarding product quality and standardization, aroma and taste formation, and more effective ripening. Their better adaptation to the fermentation environment also supports this.
In addition, using protective/starter cultures with a bacteriocinogenic effect can effectively reduce the measures that can be taken against food pathogens. While the low pH and aw, spices, high salt content, nitrite and competitive flora in fermented sausages create an obstacle against pathogenic microorganisms, disease-causing microorganisms that can survive under these conditions can also be encountered.
Finally, in this article, where we include the effects of lactic acid bacteria on sausage formation, it must be said that to guarantee the production of a standard and reliable product, the need for starter cultures is inevitable for a standard and quality product, as the quality of raw materials, exceptionally hygienic quality, may vary.
Kamiloğlu, A., Kaban, G., & Kaya, M. (2019). Effects of autochthonous Lactobacillus plantarum strains on Listeria monocytogenes in sucuk during ripening. Journal of Food Safety, 39(3), e12618.
Kamiloğlu, A., Kaban, G., & Kaya, M. (2020). Technological properties of autochthonous Lactobacillus plantarum strains isolated from sucuk (Turkish dry-fermented sausage). Brazilian Journal of Microbiology, 51, 1279-1287.