In this review study, it is aimed to give an information about the current situation and characteristics of the Traditional Turkish Fermented Soudjouk which has been known since ancient times and consumed with appreciation by the people of our country.

For this reason, the information was gathered on the importance for health and nutrition of traditional Turkish fermented soudjouk and its production technology, sensory, physico-chemical, microbiological characteristics and its current situation and was given in accordance with a certain plan.

According to this, in soudjouks produced without heat treatment, it was determined that its characteristics which subject consumer liking of soudjouk was formed the result of fermentation that occured in completely natural conditions.

In parallel with the information gathered, it has been concluded that the traditional Turkish Fermented soudjouk is a useful product for nutrition and health due to valuable nutrients and probiotic microorganisms included and so the presence of the product should be protected and its geographical marking as a national product should be made in Turkey.

Introduction

In food technology, food production and preservation methods such as fermentation, fumigation, drying and salting have been used for years to conserve food and consume more varied flavors and aromas [1].

The fermentation is a natural method that enhancing the nutritional value of foods by the synthesis of essential amino acids and vitamins and it is a metabolic process that there energy is release biochemically with partially oxidized of carbohydrates and related compounds in the absence of any electron acceptor [2].

Traditional Turkish Fermented soudjouk is a fermented meat product produced usually in the autumn season, by adding animal fat, spices, garlic and salt to cattle and buffalo meat, after thoroughly mixing, filled into natural intestines and left to natural fermentation for 15-20 days [3,4].

During fermentation under natural conditions the natural microflora of meat, fat and spices origin evolves over time depending on ambient conditions and causes to shape the desired properties specific to fermented soudjouk due to the enzymatic activities of microorganisms [5]. In particular, the natural taste, odor, flavor and aroma characteristics formed by fermentation are greatly appreciated by the consumers and increase the demand for the product.In the studies on fermented soudjouk ripened under natural conditions, it was determined that lactobacilli, micrococci, pediococci and some molds and yeasts were dominant in fermented soudjouks [6-8].

These microorganisms started to be used as starter cultures and probiotics in fermented products due to their desirable characteristics [9]. In fermented soudjouks, it is reported that Lactobacilli is efffective directly in pH reduction and aroma formation and indiretly color formation with lactic acid making up, Micrococci and staphylococci play a role in the formation of color and aroma by reducing the nitrate. Therefore, in many countries these microorganisms are used extensively as starter cultures, to control fermentation in soudjouks, shorten the ripening period, and obtain product of standard type and quality at the desired level [10]. It has been determined that the lactic acid bacteria commonly detected in Turkish soudjouks are L.sakei, L. plantarum, L.curvatus and L. Brevis [11,12].

In Turkey, despite the production of natural soudjouk is wide spread, the production is usually carried out in small-scale enterprises. On the other hand, medium and large scale enterprises prefer to produce semi-fermented soudjouks or the soudjouk-like products heat-processed due to high production cost and longer time. Some companies are selling heat-processed soudjouk-like products to the market with a natural fermented soudjouk label, which causes consumer deceptiondue to product imitation and adulteration [13].

The consumers are looking for natural flavors that they like and are used to. If the fat compositionis well adjusted,the natural fermented soudjouk is a valuable meat product in nutrition due to its useful microorganisms and its metabolism products that are contained. However, in recent years, the Traditional Turkish Fermented Soudjouk has been reduced to extinction due to the rapid development of technology and the increase in population [14,15].

This review study was carried out with the aim of revealing the characteristic of the Traditional Turkish Fermented Soudjouk consumed in Turkey and its current situation.

Definition and Importance of Traditional Turkish Fermented Soudjouk

Traditional Turkish fermented soudjouk is a fermented meat product that is produced by simply drying soudjouk under natural conditions without using starter cultures or heat treatments [16]. Generally, it is mostly produced in the autumn months when the air temperature, air flow and humidity are most suitable. It is filled with natural spices, salt and sugar into the meat-fat mixture and then ripened by natural fermentation and dried for 15-20 days in the open air [6,12,17].

According to Turkish Standards Institute (TS-1070), Turkey, soudjouk is defined as a traditional meat product for which, thermal processing is not applied. The major steps in this process include the separation of fat, bone, tendon, fascia, cartilage, lymph ovules and large nerves and veins from bovine and ovine meat, (ii) mincing by meat grinder or cutter, (iii) addition of salt, red pepper, black pepper, cumin, a variety of spices, condiments, starter cultures, body fat, internal fat, tail fat, kidney fat and one or more additives that are allowed by the legislation (iv) to be mixed into minced meat and filled in natural and artificial intestine casing and subjected to fermentation [18].

According to the Turkish Food Codex Meat and Meat Products Communique, the fermented soudjoukis defined as a fermented meat product which is not heat treated and its cross-section isof mosaic apperance.In these products minced bovine and/ or ovine meat and/ or fats are mixed with flavorings and are filled into the natural or artificial casing and the humidity is reduced to 40% or less through controlled fermentation and drying process [19].

These definitions are not specific to the Traditional Turkish Fermented Soudjouk and generally specify all sausages/soudjouks produced in Turkey. There is still no standard for traditional Turkish fermented soudjouk and in our opinion, legal regulations on meat products are insufficient.On the other hand, there are published scientific studies on Traditional Turkish Fermented Soudjouks in Turkey [10,20-24].

Fermented soudjouks constitute a significant portion of ready to serve meat products in our country and their share in meat products is approximately 42% in the market which demonstrates the importance of fermented soudjouks in the diets of Turkish people [25].

The soudjouks produced by natural fermentation have superior properties compared to the soudjouks produced by controlled fermentation using industrial starters. The reason for this is the quality of the raw meat used, the nature of the technology used and the specific structure of the natural flora [5,26].

Fermented soudjouks produced by natural fermentation without heat treatment are nutritionally valuable due to their high quality protein contents, B group vitamins, minerals, trace elements and other bioactive compounds [27]. The technological processes applied to meat products, especially heat treatments, can reduce the nutritional value of meat products by reducing the bioavailability of amino acids [28].

Fermented soudjouks in addition to their nutritive properties are considered probiotic meat products due to the beneficial bacteria they contain. Probiotic meat products are among the health-related products which have increasing importance in today’s food sector. These products have positive effects on health as well as features such as imparting flavor and aroma to the product, improving physical structure and influencing on microbiological flora [29].

Probiotics are defined as live microorganisms that, when taken at a sufficient level, have positive effects on host health and provide microbial balance of the intestinal tract [30,31]. The dominant microclora of the traditional Turkish Fermented soudjoukis Lactobacilli that is being accepted as the most important probiotic. Lactobacilli that develop in completely natural conditions has great importance for product safety and consumer health.The studies are conducted to protect these microorganisms against adverse effects of external influences and stomach digestion condıtions [11,32,33].

On the other hand, in natural conditions, it is difficult to reproduce soudjouk of the same quality and standard. Moreover, due to the increasing population, technological developments and increases in demand, soudjouk production in the standard and the same quality has become mandatory in every season of the year [34].

Consequently, the production of heat treated soudjouk-like products, which has a low production cost and short production time, has become very popular in Turkey due to the ever increasing demand from the consumers [15,35].

These emulsified products are subjected to heat treatment without using starter cultures and by the addition of some chemical substances. They can be presented to the market within 2-3 days as soudjouk-like products. In fact, these products are sausages and salami which artificially gained sensory qualities of femented soudjouk. The consumers can choose these products knowing they were not naturally produced which are also more economically available in the market place [13,36].

However, some companies are launching these products to the market with the more expensive and more desirable fermented soudjouk label which lead to consumer deception. In addition such companies taking risks in terms of health due to imitation and adulteration.

For example, in a study conducted by Pehlivanoglu et al. [13] 30 soudjouk samples present in the Istanbul market with fermented soudjouk label were examined and it was determined that 8 samples (26.6%) were fermented soudjouk products, 9 samples (30%) were semi-fermented and 13 samples (43.3%) were heat-treated non-fermented soudjouk in terms of sensory, physico-chemical and microbiological properties.

On the other hand, in this study, it was observed that soudjouks produced using starter culture did not fully reflect the characteristics of traditional Turkish fermented soudjouk. Because these soudjouk were produced in a shorter time using starter culture and heat treatment. In general, they are transformed into different products in terms of flavor characteristics and health implications when compared to traditional Turkish fermented soudjouk.

In this sense, in the first meat products “Sucuk” workshop report made in 2010, it was expressed that the heat-treated soudjouk-like products caused unfair competition among producers, that these products could mislead the consumer and that legal regulations and standards about soudjouks were not clear and sufficient. Finally, the reports stated that the inspections were inadequate and the legislation was interpreted differently by different units of government and companies [15].

Production Technology of Traditional Turkish Fermented Soudjouk Meat and Fat Choise

Cattle and buffalo meat kept under proper conditions and slaughtered when the animals were between the ages of 6-8, are generally used in production of fermented soudjouk. The carcasses that are obtained after slaugtering are stored at + 4°C for 48 hours. The pH value is reduced around the isoelectric point (pH 5.2-5.6) and meat is separated from bone. After ward, the meat parts are kept in cold storage at 80% relative humidity and at + 1°C temperature for 24 hours [12,37]. The obtained meat has low water retention properties, a lighter aroma and high coloring ability and have a pale and tight appearance [38].

Further addition of meat fats from other stokes is also carried out to increase the fat content of fermented soudjouks. For this purpose, body fat, inner fat, tail fat and kidney fat or mixtures there of are added to soudjouk at a rate of 20-40% [39]. The fat that are added to the fermented soudjouk are the ones that are added from the outside except the fat containing the meat. For this purpose, body fat, inner fat, tail fat and kidney fat or mixtures are added to soudjouk at a rate of 20-40% [39].

Soudjouk paste preparation and filling

The meat, which is used in preparing the soudjouk, is removed from the rough fat that is observed after separation from the bones. Then, it is cut into pieces the size of 6 x 8 cm and stored in cold storage for 8-12 hours at 0-4°C. The meats lose some of their weight due to the loss of water during the storage period. At the end of storage, first the meat and fats pass through the meat mincer and then meat, fat and spices are properly mixed [12,37].

Spices added to the soudjouks include red pepper (0.5-0.6%), black pepper (0.3-0.7%) and cumin (0.6-1.5%), garlic (0.4-1%), sugar (0.4-1%), salt (2.0-3.2%). Legal limits for nitrate (0.025%) and nitrite (0.015%) addition also have to be followed. The obtained soudjouk pasteis kept in cold storage at 0-4°C for 1 day [39].

The prepared soudjouk paste is filled into small intestines of cattle, and after the connection of the ends of the covers and small holes are opened to the cover surface for evaporation of water during drying [12].

Fermentation and ripening

After the filling process, the soudjouks are hanged in open areas called “Cardak” during autumn where they are exposed to heat (10-15°C), humidity (80-90%) and wind (1-1,5 m/ sn). Here, for 15-20 days, soudjouks gradually dry out, and the ripening during microbial fermentation influences both internal and external characteristics of the product [8, 21].

The drying in soudjouks takes place from inside to outside where the water comes out partly by the diffusion and partly from the small canals between the rough texture particles of soudjouk paste. The presence of ducts that provide drying in soudjouks depends on the amount of fat added and on the temperature of the meat and the fat as well as the sharpness of the instruments used for meat grinding [38,39].

The quality and storage stability of the fermented soudjouks is largely dependent on their moisture content that has been properly lost during ripening. The degree of drying rate, the content and degree of mincing the soudjouk paste, the thickness of the soudjouk coil, the temperature, humidity and air current applied during ripening are factors that influence the soudjouk quality [12].

In fermented soudjouks the ripening is characterized by the aroma, flavor, color and consistency characteristics which are developed as a result of the biochemical reactions formed by the enzymes of various microorganisms [5,7,40].

The presence of a desired microflora in fermented soudjouks is required for biochemical reactions. The role of these desired microorganisms in soudjouk ripening, are to create color, to reduce the pH, degrading the glycogen present in the meat, to provide an acidic environment, to form aroma and flavor degrading fats and to prevent the development of undesirable bacteria [17,41-43].

Characteristics of Traditional Turkish Fermented Soudjouk

Characteristics of fermented soudjouks consist of a series of biochemical, microbial, physical and sensory changes that occur during soudjouk ripening at a certain relative humidity, temperature and air flow conditions [44,45].

These changes, which are the result of fermentation, are defined as pH decrease, microflora change, reduction of nitrate to nitrite and nitrosomyoglobin formation, increased solubility and gelation of myofibrils and sarcoplasmic proteins, proteolytic, lipolytic and oxidative changes and acidification resulting from dehydration [43,46-48].

Sensorial properties

In traditional Turkish fermented soudjouks, the sensory properties such as appearance, color, consistency, cross-section, flavor and aroma are shaped depending on the applied technological processes and the microbial activities that occur during fermentation [49,50].

The soudjouk paste filled in the intestines should be in homogeneous appearance, there should be no folds, molds, salt stains and bacterial spots on the outer surface of the soudjouk casing. Especially fats should not flow out from the intestines. Good mixing of meat, fat and other materials in the soudjouk and proper filling of the intestines gives a homogeneous appearance and a smooth cross-section character [51].

A ripe soudjouk has a normal red meat color, and this color should be the same on the outer surface and along the cross-section of the fermented soudjouk. Nitrite and nitrate, which are used according to the legal limits play an important role in colour formation and stabilization. These chemical substances provide reliability in soudjouks. The formation of color in soudjouks is due to the reduction of nitrate to nitrites by bacteria and the formation of Nitroso-Myoglobin (NOMb) by combining the formed NO with myoglobin in the meat. Red pepper and sugar contribute to the desired colouring of soudjouks [12,52].

The consistency of fermented soudjouk should be medium; not too hard or too soft. For this reason, the meat used in production must be ripe meat and the meat fat mixture must be well-adjusted and well-chilled. In addition, a hard ring should not occur on the soudjouk surface which is an indication of drying faults. Fermented soudjouks should be easy to cut and the cross-section must be smooth. The fat on the cross section must be homogeneously dispersed and demonstrate marble-like appearance [26,51].

The flavour and aroma properties of fermented soudjouks due to formation of numerous volatile and non-volatile components during microbial fermentation. Amino acids, peptides, carbonic acid, sugar and their vicissitudes and organic salts are considered non-volatile aroma substances. Most of these compounds are considered to be the precursors of the volatile aroma substances that will be formed later towards the end of fermentation [46,53-55].

Spices such as red pepper, black pepper, cumin and garlic, and additives such as salt and sugar which are added to soudjouk paste play an important role in the formation of typical taste and aroma [12,39].

Physico-chemical properties

During the first days of fermentation, the pH value of the fermented soudjouk is between 5.6 and 5.8. due to the breakdown of carbohydrates by bacteria, the pH drops to 4.8-5.0. Likewise, in the first days of drying, the humidity 65-70% decreases gradually by 25-30% and drops to about 40% [12,56].

According to Turkish Standards Institute, TS-1070, pH value of Turkish soudjouk is between 4.7-5.4% and moisture content maximum is 40%, while the fat content can be up to 30% for the first grade, and up to 40% for the second grade. Protein concentration can be up to 20% for the first grade and up to 18% forthe second grade [18].

According to Turkish Food Codex Meat and Meat Products Communique, it is necessary that the total protein mass of soudjouk is at least 16%, the amount of collagen is not more than 20% by mass of total meat proteins, the ratio of the amount of moisture to the total amount of meat protein is less than 2.5, the ratio of the amount of fat to the total amount of meat protein is less than 2.5 and the highest pH value is 5.4 in fermented soudjouks [19].

In a study conducted by Oksuztepe, et al. [23] on 100 fermented soudjouk samples sold in Elazig, it was determined that the average pH value, the amount of moisture, the amount of fat, and the amount of protein were 5.18, 38.75%, 35.22% and 21.92%, respectively. Similarly; in a study conducted on 30 fermented soudoudjouk samples sold in Konya, it was determined that the average pH value, the amount of moisture, the amount of fat, and the amount of protein were 5.24, 29.49%, 30.9%, 22.73%, respectively [20].

In a study on soudjouks produced by classical type and heat treatment, it was determined that the mean amount of moisture was 50-55% in heat treated and 45% in fermented soudjouk, the fat amounts in heat treated soudjouk 36% and fermented soudjouk 35%, the protein amounts in heat treated % 28 and 28% in fermented soudjouk [14].

Microbiological properties

The basis of fermented soudjouk production are the microorganisms, and the microflora detected in the soudjouk reveals the microbiological quality. These microorganisms contribute to the formation of desirable sensory properties such as taste, aroma and color of the soudjouk with their metabolic products [5,22,48,57]. The biochemical activities of microorganisms such as lactobacilli, staphylococci, micrococci, molds and yeasts are important in the formation of these fermented soudjouk characteristics [12,39].

In studies on fermented soudjouk, it was determined that the total aerobic mesophile microorganisms, coliform microorganisms, lactic acid bacteria, Micrococcus, Staphylococcus, mold and yeast constitute the microflora of soudjouks [10,20,21,23,24]. According to Turkish Food Codex Meat and Meat Products Communique, fermented soudjouks should not contain Salmonella, Listeria monocytogenes and E. coli O157: H7 at 25 grams of the sample [19].

In many studies, the total number of aerobic microorganisms in fermented soudjouks is reported to be between 10⁶ and 10⁷ cfu/ g [22,12]. However, it is necessary to know from which microorganisms qualitatively the microflora detected in the samples are formed and whether they are desirable microorganisms to be present in fermented soudjouk [40,58].

Coliform group microorganisms which are members of Enterobacteriaceae, indicate a possible cross-contamination during production. These microorganisms produce lactic acid from carbohydrates, convert nitrates to nitrites and break down proteins [39]. However, these microorganisms are also an indication of poor hygiene and technological faults in riped and launched fermented soudjouks. Therefore, coliform microorganisms should not be at high numbers in soudjouk [6,12].

In the fermentation and ripening stages lactic acid bacteria firstly lower the pH value by converting glucose to lactic acid, thereby causing the inhibition of pathogens and undesirable bacteria on the one other hand causing the formation of the typical organoleptic properties of the fermented meat products [11, 59].

It is known that the dominant flora is generally lactobacilli [7,33]. The salt added to the soudjouk paste and the high ripening temperature cause a decrease in water activity as a result lactobacilli dominate the microflora. This decreases the soudjouk pH value while the taste and aroma are also affected [8,39,59].

Likewise, micrococci and staphylococci are responsible for the development of color by reducing nitrate to nitrite, at the same time they are also effective in the development of aroma in fermented meat products due to their lipolytic and proteolytic activities [60]. Micrococci and staphylococci that can survive at high salt and CO2 values at low pH and water activity values are associated with lactobacilli during ripening and contribute to the formation of color and aroma in soudjouks [10,41,56,60].

In the first days of ripening, the number of molds and yeasts increases rapidly and the number reaches up to 10⁶ cfu/ g depending on the environmental conditions. In the following days, the number of molds and yeasts is decreasing towards the end of ripening with decreasing pH, water activity and redox potential values, and they concentrate towards the outer parts of the soudjouk [6,8,12]. While some types of mold and yeast have an effect on color, aroma and odor properties in soudjouks, other types could lead to spoilage [39,61].

In a study conducted by Nazli [12] fermented soudjouk were produced without starter cultures and it was determined that the average number of total mesophilic aerobic microorganisms was 5 x 10⁶ cfu/ g, the number of coliform microorganisms was 3 x 10³ cfu/ g, the number of Staphylococcus was 2,4 x 10⁴ cfu/ g, the number of Lactobacillus was 1,3 x 10⁶ cfu/ g and the number of mold and yeast 1,2 x 10⁴ cfu/ g.

Similarly, in another study on 30 soudjouk samples obtained from the Konya market by Atasever, et al. [20] the average total aerobic microorganism, coliform group microorganism, microcoke-Staphylococcus and mold-yeast counts were reported as 5.7 x 10⁶, 7.4 x 10³, 3.2 x 10⁵ and 6.4 x 10⁴ cfu/ g, respectively.

Conclusıon

Traditional Turkish fermented soudjouk is a fermented meat product that is produced without heat treatment sor starter cultures. Fermented soudjouks are dried and ripened under completely natural conditions.

However, in such soudjouks, the structure, taste and other characteristics may be different from each other and it is not always possible to produce products with the same characteristics.In addition, due to increasing world population, technological developments and increasing demand, meat products with standardized properties has become mandatory in every season of the year. For this reason, in efforts to standardize the products produced by traditional methods have gained momentum [9,34].

Today, many countries in the world continue to utilize natural fermentation without the use of starter cultures by small businesses [62]. In the same way, traditional Turkish Fermented soudjouk production in Turkey is only carried out locally in some small enterprises and is therefore it has become extinct.

It is possible to make this product more useful in terms of food safety and consumer health by optimizing the bioactive functions of probiotic bacteria which are very important for public health in Turkish fermented soudjouks and strengthening them against adverse effects of external influences and stomach digestion conditions [16,63].

In accordance with the information given above, fermented soudjouks produced according to the specified procedures, the following results have been reached. The sensory properties such ascolor, consistency, taste and aroma that are preferred by consumers develop during ripening with microbial fermentation. Due to having low pH and low water activity values which occurs due to the ripening process, fermented soudjouk is a reliable product and has a long shelf life.

In ripe soudjouks, lactobacilli can demonstrate probiotic properties and dominate to the microflora. Therefore fermenfed soudjouks should be considered as a probiotic meat product. In Turkey, there are very modern and high capacity facilities which were built in accordance with global standards. In these facilities, it is possible to produce soudjouks in a shorter time by using starter cultures unique to Turkish fermented soudjouk, by controlled fermentation and drying.

Therefore, it is necessary that the traditional Turkish Fermented soudjouk characteristics should not be lost, the production of this product be encouraged, developed and popularized. Finally, geographical marking of soudjouk needs to be completed rendering fermented soudjouk a national product.

Acknowledgements

We would like to thanks to Asistant Professor. Dr. Ibrahim Gulseren and Researcher Asistant Marin Neio Demirci from Istanbul Sabahattin Zaim University, Istanbul, Turkey because they have reviewed the manuscript and agreed with the content.

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