Effects of Lactobacillus plantarum and Staphylococcus xylosus on the Quality Characteristics of Dry Fermented Sausage “Sucuk”

Authors


Abstract

ABSTRACT:  The effect of starter culture, containing the strains Lactobacillus plantarum GM77 and Staphylococcus xylosus GM92, isolated from traditional sucuk, on the quality characteristics of dry fermented sausage (sucuk) during ripening period was studied. The microbiological (lactic acid bacteria, Micrococcus/Staphylococcus, Enterobacteriaceae) and physicochemical (pH, aw, NPN, TBARS) properties and volatile compounds, extracted by solid phase microextraction and analyzed by gas chromatography-mass spectrometry, were determined in sucuk samples with starter culture and in the control group (without starter culture). Both starter culture and ripening period had significant effects on lactic acid bacteria, Micrococcus/Staphylococcus counts, and pH and aw values (P < 0.01). The highest value for nonprotein nitrogen (NPN) was observed to occur in samples with starter culture (P < 0.05). TBARS value increased during ripening, the highest value was determined at 14th day in samples with starter culture. Among volatile compounds, terpenes were the major group in sucuk. Other volatile compounds (aldehydes, ketones, sulfur compounds, acids, esters, aliphatic hydrocarbons, aromatic hydrocarbons, and alcohols) can be found in fewer amounts. While the use of starter culture was affecting a few compounds, ripening period had affected most of the compounds.

Introduction

Sucuk is a type of dry fermented sausage commonly produced and consumed in Turkey. Beef meat and/or sheep/water buffalo meat and sheep tail fat and/or beef fat are used as raw material in the production of sucuk. Sucuk batters are filled into air-dried bovine small intestines or small casings of similar characteristics. Initial fermentation temperature and ripening time vary between 12 and 26 °C and 6 and 20 d, respectively (Ertaş and Göğüş 1980; Gökalp and Ockerman 1985; Soyer and others 2005). Smoking is not used in sucuk production. Starter culture usage is increasing in the industry day by day; however, traditionally produced sucuk is widely preferred by the consumers because of its sensory characteristics.

There are many studies on the effects of starter culture on various quality characteristics of sucuk (Ertaş and Göğüş 1980; Gökalp and Ockerman 1985; Vural 1998). However, there is only 1 study about volatile compounds. Ercoşkun (1999) investigated the effects of commercial starter cultures on the volatile profile of sucuk. Berdagué and others (1993) studied the effects of different starter cultures on the formation of volatile compounds in dry sausage. Stahnke (1994, 1999) described volatile compounds from dry fermented sausage containing Staphylococcus xylosus or S. carnosus. Moreover, Johansson and others (1994) determined volatile compounds during the ripening of a fermented sausage with Pediococcus pentosaceus and S. xylosus. Sondergaard and Stahnke (2002) investigated aroma production by S. xylosus, S. carnosus, and S. equorum in a sausage mince inoculated with P. pentosaceus. A study by Olesen and others (2004) showed major differences in the development of volatile compounds between sausages with S. xylosus and S. carnosus.

Lactobacillus plantarum was frequently isolated as the main Lactobacillus species in sucuk and, as well as, S. xylosus, dominated the population of coagulase-negative cocci (Staphylococcus and Kocuria) (Kaban and Kaya 2008). This study was aimed to determine the effect of strains, Staphylococcus xylosus GM92 and Lactobacillus plantarum GM77 isolated from traditional sucuk (Kaban and Kaya 2008), on the formation of volatile compounds during the ripening of dry fermented sausage (sucuk) and to define the microbiological and physicochemical changes occurring in sucuk.

Materials and Methods

Preparation of starter culture

In this study, Lactobacillus plantarum GM77 and Staphylococcus xylosus GM92, isolated from traditional Turkish dry fermented sausage (sucuk), were used as starter culture. L. plantarum GM77 can grow in both 15 and 45 °C and, on the other hand, in the presence of 6.5% and 10% NaCl, and it did not cause the formation of ammonia from arginine. S. xylosus GM92 is a facultative anaerobe, and showed lipolytic, proteolytic, and nitrate reductase activities (Kaban 2007). L. plantarum GM77 was grown in MRS broth (Oxoid) and S. xylosus GM92 was grown in TSB (Oxoid) at 30 °C for 24 h. L. plantarum GM77 and S. xylosus GM92 were added to the sucuk mix to attain 107 and 106 CFU/g, respectively.

Production of sucuk

The sausage consisted of beef meat (80%) and beef meat fat (20%), to which the following ingredients (in g/kg of meat–fat mixture) were added: salt (25), garlic (10), sucrose (4), red pepper (7), black pepper (5), cumin (9), pimento (2.5), and NaNO2 (0.15). Two batches were prepared for both the control group and group containing starter culture. The sucuk batters were prepared in a laboratory-type cutter (MADO Typ MTK 662, Dornhan, Schwarzwald, Germany). First, a control group batter (without starter culture) was prepared. Then, batter containing starter culture (Lactobacillus plantarum GM77 +Staphylococcus xylosus GM92) was prepared. The mixture of each batter was stuffed into collagen casings (38 mm, Naturin Darm, Germany) with a laboratory-type filling machine (MADO Typ MTK 591, Dornhan, Schwarzwald), the final mass of each sausage being 200 g. The ripening procedures were as follows: 3 d at 24 ± 1 °C and relative humidity (RH) 90 ± 2%, 4 d at 22 ± 1 °C and RH 85 ± 2%, and 7 d at 18 ± 1 °C and RH 80 ± 2%.

Sampling procedures

Sampling was performed by randomly selecting 2 samples of each batch of sausage after 0, 1, 3, 7, 9, and 14 d for volatile compounds, microbiological, and physicochemical analysis. Two replicates were carried out for microbiological and physicochemical analyses and 3 replicates were carried out for volatile compounds analyses.

Microbiological analysis

For microbiological analysis, the sausage casing was removed aseptically. Sausage was cut using a sterile knife. Twenty-five-gram samples from each sausage were transferred into a sterile stomacher bag and 225 mL of sterile physiological water (0.85% NaCl) were added and homogenized for 1.5 min in a stomacher (Lab Stomacher Blender 400-BA 7021, Seward Medical, London, U.K.). Serial decimal dilutions were prepared in the same diluent and 0.1 mL samples of appropriate dilutions were spread in duplicate on selective agar plates.

Lactic acid bacteria were enumerated on de Man, Rogosa, Sharpe, Agar (MRS, Oxoid, Hampshire, U.K.) in anaerobic conditions (Aneorocult A, Merck, Damstadt, Germany) after 48 h at 30 °C; micrococci and staphylococci on Mannitol Salt Phenol-Red Agar (MSA, Merck) after 48 h at 30 °C. Enterobacteriacea were determined on Violet Red Bile Dextrose Agar (VRBD, Merck), incubation was carried out at 30 °C for 48 h in anaerobic conditions.

Physicochemical analysis

The pH was measured in a homogenate of the samples with distilled water (1: 10, w/v) using a pH meter (ATI ORION 420, Boston, Mass., U.S.A.). Water activity (aw) was determined using a TH-500 aw sprint apparatus (Novasina). Nonprotein nitrogen (NPN) was determined by the Kjeldahl method after protein precipitation with trichloroacetic acid, the results were expressed as g/100 g of sausage (Anonymous 1989). Thiobarbituric acid-reactive substances (TBARS) values of samples were determined according to the methods of Lemon (1975) and were expressed as μmol MDA/kg.

Volatile compounds analysis

The extraction of headspace volatile compounds was done using a SPME device (Supelco, Bellefonte, Pa., U.S.A.), using fibers of 75 μm, carboxen/polydimethylsiloxane (CAR/PDMS). Before the analysis, the fibers were preconditioned in the injection port of the GC as indicated by the manufacturer. For each analysis, 5 g of sucuk samples were minced and weighed into a 40 mL headspace vial and sealed with a PTFE-faced silicone septum (Supelco). The vial was left at 30 °C in a thermo block (Supelco) for 1 h to equilibrate its headspace. Subsequently, a SPME fiber was exposed to the headspace while maintaining the sample at 30 °C for 2 h. The compounds absorbed by the fibers were identified by gas chromatographic analysis using MS detectors. The compounds adsorbed by the fiber were desorbed from the injection port of the gas chromatography (GC, Agilent Technologies 6890N, Santa Clara, Calif., U.S.A.) for 6 min at 250 °C with the purge valve off (splitless mode). The compounds were separated in a BD-624 (J&W Scientific, 30 m, 0.25 mm i.d., 1.4 μm film, Folsom, Calif., U.S.A.) capillary column. The GC was equipped with a mass selective detector (MS, Agilent Technologies 5973). Helium was used as carrier gas. The GC oven temperature program was started when the fiber was inserted and held at 40 °C for 5 min and subsequently programmed from 40 to 110 °C at 3 °C/min and at a rate of 4 °C/min from 150 °C, then at a rate of 10 °C/min from 210 °C where it was held for another 15 min. The total run time was 56.33 min and the GC-MS interface was maintained at 240 °C. Mass spectra were obtained by electron impact at 70 eV, and data were acquired across the range 50 to 500 uma.

The compounds were determined by comparing the results with mass spectra from a database developed by NIST and WILEY or standards molecules (for calculation kovats index; Supelco 44585-U) and by matching their retention indices with those in the literature. Quantification was based on either a total or single ion chromatogram on an arbitrary scale (eV). The results are expressed as means of 3 replicates.

Statistical analysis

The experimental design was completely randomized having 2 factors. The factors were starter culture (the control and starter culture) and ripening period (0, 1, 3, 7, 9, and 14 d). The experiment was carried out in duplicate. The data were analyzed by variance analysis and differences between means were evaluated by Duncan's multiple range test using SPSS 13.0.0.246 for Windows (SPSS, Inc., Chicago, Ill., U.S.A.). The results of statistical analyses are shown in the tables.

Results and Discussion

Lactic acid bacteria, Micrococcus/Staphylococcus, Enterobacteriaceae

The effects of starter culture and the ripening period on the microbiological and physicochemical properties of sucuk are shown in Table 1. Both starter culture and the ripening period had very significant effects (P < 0.01) on counts of lactic acid bacteria and Micrococcus/Staphylococcus (Table 1). Lactic acid bacteria counts reached 105 CFU/g at the end of 24 h fermentation in the control group while it was approximately 108 CFU/g in sucuk with starter culture (Figure 1). As it can be seen from Figure 1, L. plantarum GM77 has adapted well to the ripening conditions, and lactic acid bacteria counts remained high in sucuk with starter culture to the end of the ripening period. S. xylosus GM92, which was added to sucuk batter at 106 CFU/g level, increased approximately 1 log unit within the first 3 d of the fermentation. There were no significant differences in the number S. xylosus GM92 in the following days of the ripening (Figure 2). In the control group without starter culture, Micrococcus/Staphylococcus showed a rapid increase in the first 3 days of fermentation, and then their counts remained quite stable in number throughout the ripening period (Figure 2). However, in some cases it has been reported that fast growth of lactic acid bacteria, with the consequence of deep acidification of the substrate, could result in inhibition toward these microorganisms that exhibit a slow growth (Rantsiou and Cocolin 2006). The major functions of these microorganisms comprise color formation and stabilization and aroma development by means of their catalase and nitrate and nitrite reductase activities and implication in lipid metabolism (Lücke 1998; Toldra and others 2001). Enterobacteriaceae, which are sensitive to acid and water activity, were progressively eliminated from the ripened sucuk, the initial Enterobacteriaceae counts were detected at 103 CFU/g level, and it dropped to nondetectable levels at the 7th day in the control group and at 3rd day in sucuk with starter culture.

Table 1—.  The effects of starter culture and ripening period on the microbiological and physicochemical properties of sucuk (mean ± SD).
FactornLactic acid bacteria (log CFU/g)Micrococcus/Staphylococcus (log CFU/g)pHawNPN (g/100 g)TBARS (μmol MDA/kg)
  1. Different letters indicate statistical difference (P < 0.05) in each column. **P < 0.01; *P < 0.05.

  2. SC = starter culture; RP = ripening period; SC × RP = interaction of starter culture and ripening period.

  3. SD = standard deviation; NS = not significant.

Starter culture (SC)
 Control126.26 ± 2.03a6.02 ± 1.14a5.57 ± 0.12a0.916 ± 0.047a2.86 ± 0.97a14.62 ± 2.35a
 Starter culture127.98 ± 0.49b6.66 ± 0.34b4.91 ± 0.41b0.904 ± 0.058b3.16 ± 1.06b15.50 ± 3.29b
 Significance **********
Ripening period (RP)
 0 d44.60 ± 2.38a5.04 ± 1.22a5.67 ± 0.01d0.966 ± 0.000e1.75 ± 0.17a10.77 ± 0.54a
 1 d46.84 ± 1.33b5.96 ± 0.99b5.47 ± 0.35c0.962 ± 0.002e1.93 ± 0.08a13.38 ± 0.80b
 3 d47.87 ± 0.57d6.93 ± 0.13e5.14 ± 0.49b0.944 ± 0.005d2.70 ± 0.18b14.56 ± 0.88c
 7 d47.91 ± 0.58d 6.82 ± 0.18de5.04 ± 0.46a0.883 ± 0.014c3.46 ± 0.40c16.45 ± 0.54d
 9 d47.89 ± 0.42d 6.68 ± 0.12cd5.07 ± 0.51a0.871 ± 0.012b4.01 ± 0.21e16.74 ± 1.10d
 14 d47.61 ± 0.32c6.61 ± 0.18c5.08 ± 0.50a0.833 ± 0.018a4.23 ± 0.28e18.48 ± 2.77e
Significance ************
SC × RP *******NS**
Figure 1—.

The effect of interaction of starter culture and ripening period on lactic acid bacteria.

Figure 2—.

The effect of interaction of starter culture and ripening period on Micrococcus/Staphylococcus.

pH and aw values

Starter culture and the ripening period had very significant effects (P < 0.01) on the pH value of sucuk. Mean pH value for the control group was 5.57 ± 0.12 while it was 4.91 ± 0.41 for the group with starter culture, and these 2 values are statistically different. The pH value dropped within the first 3 d, and differences were not statistically significant (P > 0.05) in the last 3 d of analysis (Table 1). An interaction (P < 0.01) of starter culture and ripening period was found for the pH value (Figure 3). As it can be seen from the figure, during the first 3 d, the pH values were higher in the control samples, as well as at 14th day when showed a relevant increase. The amino acids released during proteolysis can be decarboxylated, deaminated, or even further metabolized. Therefore, the generated ammonia and amines cause an increase in pH, which was observed during the last phase of ripening (Toldra and others 2001). The pH value of the group with starter culture dropped to below 5 at the 3rd day, in contrast, pH value of the control never dropped to under 5.4 (Figure 3). These findings are agreement with microbiological results. Lactic acid bacteria are one of the main groups of bacteria in fermented meat products. The major role of lactic acid bacteria is production of organic acid, primarily lactic acid, from carbohydrates. The acidification lowers pH value and ensures hygienic stability. The pH drop also causes coagulation of meat proteins and reduction in water holding capacity, and therefore facilitates the drying process (Lücke 1998; Toldra and others 2001). Lactic acid bacteria grew more slowly in the control group than in sucuk with starter culture, and, as a result, pH dropped slowly in the control group. Therefore, Micrococcus/Staphylococcus showed a good growth pattern in the control group at the first days of ripening.

Figure 3—.

The effect of interaction of starter culture and ripening period on pH.

Starter culture and the ripening period had very significant effects (P < 0.01) on the aw value of sucuk. The lowest aw value was observed in sucuk with starter culture. After 24 h fermentation, aw value showed no significant changes (Table 1). The interaction of starter culture and ripening period had a significant effect (P < 0.05) on aw value (Figure 4). Samples with starter culture showed lower aw values in comparison to that of the control after the 3rd day of ripening. The water activity decreases during prolonged fermentation and becomes inhibitory to lactic acid formation at values around 0.91 (Lücke 1998). The aw value was dropped to below 0.90 at the end of ripening, which is a good hurdle effect for sucuk.

Figure 4—.

The effect of interaction of starter culture and ripening period on aw.

Nonprotein nitrogen (NPN) and thiobarbituric acid-reactive substances (TBARS)

According to the variance analysis results of the NPN values, both starter culture (P < 0.05) and the ripening period (P < 0.01) had very significant effects on NPN value. In contrast, there is no significant effect of the interaction of starter culture and ripening period (P > 0.05) (Table 1). In agreement with the results of this study, some other studies have shown that proteolysis during the ripening of fermented sausage is reflected by an increase in NPN value (Hughes and others 2002; Gençcelep and others 2007). Hughes and others (2002) reported that NPN values of the samples containing S. carnosus are higher than that of the control group. In the present study, the higher NPN value in sucuk with starter culture may result from the S. xylosus GM92 that has proteolytic activity. Proteolysis is one of the most important biochemical changes occurring during the ripening of dry fermented sausage. It was reported that the extent of proteolysis depends on the acidity of the sausage, and that the proteolytic activity is low in low-acidity sausage (Toldra and others 2001). Our findings are in agreement with these results (Table 1).

Use of starter culture affected TBARS value at P < 0.05 level. Mean TBARS values were determined as 14.62 ± 2.35 μmol MDA (malondialdehyde)/kg in the control group and 15.50 ± 3.29 μmol MDA/kg in sucuk with starter culture. As the ripening period progressed, TBARS value increased (Table 1). An interaction (P < 0.01) of starter culture and ripening period was found for the TBARS value, as shown in Figure 5. As it can be seen from the figure, a significant increase in the TBARS values of the sucuk with starter culture was observed after the 9th day. The probable cause of this increase may be the lipolytic activity of S. xylosus GM92. Free fatty acids that are the products of lipolysis are the precursors of the lipid oxidation (Toldra and others 2001). On the other hand, Stahnke (1994) detected elevated amounts of long-chain fatty acids in sausage fermented with a lipolytic S. xylosus, although it seems that this is not important in terms of flavor development.

Figure 5—.

The effect of interaction of starter culture and ripening period on TBARS value.

Volatile compounds

Forty compounds were selected from the volatile compounds identified from the control group and sucuk with starter culture, and mean peak areas and variance analysis results for these 40 compounds are shown in Table 2. Among volatile compounds, terpenes are important group in terms of amount and number. Although some of them (α-terpinene and limonene) have been in meat as a consequence of their presence in animal feedstuffs, the major scores are related to the use of spices in preparation of sausage (Ansorena and others 2001). Especially o-cymene was found in high amounts during ripening of sucuk. This compound and cumic alcohol are important compounds derived from cumin. (Iacobellis and others 2005). γ-terpinene, which can be found in pepper, cumin, and some other spices (Ansorena and others 2001; Luongo and others 2001), was also observed in high amounts in samples. Many other researchers also observed that the amount of terpenes generally increases with the ripening time (Mateo and Zumalacarregui 1996; Misharina and others 2001). β-myrcen, α-phellandrene, 3-carene, and α-terpinene were detected in samples with starter culture in high amounts at the last days of the ripening.

Table 2—.  The effects of starter culture and ripening period on the volatile compounds from sucuk samples.
Identified compoundsKIRIStarter culture (SC)SEMP valuesb
ControlStarter culture
Ripening period (RP)Ripening period (RP)
0 d1 d3 d7 d9 d14 d0 d1 d3 d7 d9 d14 dSCRPSC×RP
  1. aMean paek area; bsignificant levels from analysis of variance. Only significant values listed (P < 0.05); SEM = standard error of mean; RI = reliability of identification.

  2. KI = Kovats index calculated for DB-624 capillary column (J&W Scientific: 30 m, 0.25 mm i.d., 1.4 μm film thickness) installed on a gas chromatograph equipped with a mass-selective detector.

  3. A = mass spectrum and retention time identical with an authentic sample; B = mass spectrum and Kovats index from literature in accordance; C = tentative identification by mass spectrum.

1,3,-epithio propene618B1.89a3.072.420.9750.670.571.632.917.0610.845.739.300.698<0.001<0.001<0.001
Acetic acid717A0.540.480.424.261.761.320.252<0.001<0.001<0.001
Allyl methyl sulphide730B1.901.101.030.331.010.841.222.411.120.832.111.630.1300.0300.0060.017
Toluene791A1.670.961.550.841.791.420.822.110.871.483.281.440.1530.0110.018
3,3′-thiobis-1-propene888B4.643.212.880.970.940.853.274.921.330.691.621.200.305<0.001<0.001
Styrene933B0.050.050.140.460.130.430.470.110.0390.040<0.001
α-thujene944B0.390.070.360.330.220.390.030.320.300.510.350.0340.016<0.001
1R-α-pinene957B0.350.370.490.790.800.740.420.510.530.950.760.900.0440.017<0.001
2-metil– propenyl disulfide955B1.781.530.971.380.901.240.182.020.810.210.300.270.136<0.0010.0030.008
β-pinene988B1.731.621.953.683.562.431.452.212.503.972.362.750.171<0.0010.008
β-myrcene1005B0.070.530.990.911.021.470.822.653.260.217<0.001<0.0010.008
α-phellandrene1019B0.990.460.710.650.800.860.521.300.750.831.441.190.063<0.0010.003<0.001
3-Carene1026B0.930.210.620.550.890.810.790.960.660.701.311.060.0620.0090.015
α-terpinene1030B0.390.150.230.140.170.220.310.120.130.570.370.0330.0110.0050.003
D-Limonene1054B2.501.172.181.171.742.011.882.382.031.483.963.100.165<0.001<0.001<0.001
o-cymene1059B29.1313.1116.7110.7015.2415.0716.5332.9216.6812.4933.3822.311.650<0.001<0.001<0.001
β-ocymene1066C0.120.050.110.030.080.120.140.080.030.110.090.0090.0460.015
Hexanoic acid1076A 0.050.030.050.090.0060.0280.001
γ-terpinene1079B7.475.056.435.555.646.105.157.707.267.399.559.590.317<0.0010.003<0.001
2-ethylhexanol1084B0.350.050.140.070.050.090.220.030.120.040.0230.0290.025
di-2-propenyl disulfide1138C6.188.946.054.533.174.046.485.573.721.980.392.340.474<0.001<0.0010.004
2,4-Hexadienoic acid, ethyl ester1154B0.090.200.300.1220.019
Linalol1161B6.696.037.384.644.894.976.365.836.725.225.155.460.183<0.001
Camphor1233C0.230.160.190.180.200.150.180.270.180.150.130.150.009
4-terpinenol1240B0.210.140.250.100.180.210.190.230.140.160.200.0140.017<0.001
2-buten-1-ol, 4-(1-cyclohexen-1-yl)1261C0.200.630.370.310.620.360.0690.011
α-terpineol1263C0.160.320.270.130.290.026<0.0010.0050.005
Benzene,1,3-bis (1,1dimethylethyl)1278B0.200.060.100.040.150.140.180.090.0160.001
2-methyl-3-phenyl propanal1334B10.4530.5125.9835.1028.4328.2329.649.4818.1412.613.766.672.256<0.001<0.001
Benzene,1-methoxy–4-(1-propenyl)1342C0.090.180.130.300.320.220.170.020.150.340.050.150.0220.0310.0040.011
α-2-propenyl,benzenemethanol,1357C0.341.980.910.130.081.430.291.470.600.130.143<0.0010.001
Cumic alcohol1371C0.040.090.150.510.470.480.100.102.765.300.772.180.319<0.001<0.001<0.001
β-elemene1453B0.030.030.060.130.110.110.080.030.090.130.040.120.0080.001
Eugenol1460B0.090.610.330.920.880.600.240.080.601.330.180.460.078<0.001<0.001
Benzene, 1,2-dimethoxy-4-(2-propenyl)1466C0.311.850.953.453.491.961.170.272.104.720.591.580.016<0.0010.004
Pentadecane1500A0.210.110.110.210.340.250.2940.017<0.0010.035
Caryophyllene1490B0.971.391.662.842.412.391.250.762.593.681.532.550.177<0.001<0.001
α-caryophyllene1504B0.190.110.120.190.150.190.120.070.140.250.210.220.0110.039<0.001
Benzene, 1,2-dimethoxy-4-(1-propenyl)1558C0.050.150.140.140.180.380.200.030.200.240.010.250.021<0.0010.003
Hexadecane1600A0.040.520.960.050.811.640.008<0.001

Starter culture, ripening period, and the interaction of starter culture and ripening period had significant effects (P < 0.001) on acetic acid, that was detected in the control group only at 9th and 14th days, and from 3rd day on in sucuk with starter culture. According to this result, the use of starter culture increased the amount of acetic acid. This compound produced by lactic acid bacteria and staphylococci contributes to aroma of dry sausage. Acetic acid may also be formed by lipid oxidation and amino acid catabolism (Montel and others 1998). In earlier studies, it was reported that different species of Staphylococcus produce different aroma compounds in different amounts (Berdagué and others 1993; Montel and others 1996; Stahnke 1999). In a study by Luongo and others (2001), the use of L. sakei as starter culture in fermented sausage influenced the aroma characteristics.

1,3,-epithio propene increased in sucuk with starter culture in general as ripening period progressed, and it decreased in the control group, especially at 7th, 9th, and 14th days (Table 2). Amount of 3,3-thiobis-1-propene in the control dropped as time passed by, and it is increased on the first day in sucuk with starter culture, and then dropped in the following days. Allyl methyl sulphide, 2-metil-propenyl disulfide, and di-2-propenyl disulfide are other sulfur compounds detected in sucuk. The peak area of di-2-propenyl disulfide is higher than the others'. Sulfur compounds may be originated from garlic used in sucuk. However, these compounds may be a result of the degradation of sulfur amino acids (Toldra and others 2001).

The characteristic flavor of fermented sausages mainly originates from the breakdown of carbohydrates, lipids, and proteins through the action of microbial and endogenous meat enzymes. The development of flavor is also influenced by several variables such as product formulation (especially spices), processing condition, and starter culture (Stahnke 1994; Lücke 1998; Toldra and others 2001). 2-metil-3-fenil propanal was detected in sucuk with or without starter culture (Table 2). In contrast, this compound was not detected in other studies of dry fermented sausages (Mateo and Zumalacarregui 1996; Misharina and others 2001). This compound was detected by Jalali-Heravi and others (2007) in cumin, which was an important ingredient in sucuk production. α-2-propenil-benzenemethanol and 2-ethyl,1-hexanol were detected in sucuk samples. However, the use of starter culture had no significant effects (P > 0.05) on these compounds. Lipid oxidation, carbohydrate catabolism, and amino acid catabolism could be the most important pathways accounting for the production of many volatile compounds including alcohols in dry fermented sausage (Mateo and Zumalacarregui 1996; Ansorena and others 2001).

Benzene, 1,2-dimethoxy-4-(2-propenyl) is the most abundant aromatic hydrocarbon in terms of peak area. This compound showed high peak area values at 7th and 9th days in the control group, and at 7th day in sucuk with starter culture. Eugenol, a nonterpenic compound originated from species, was generally increased with the progress of ripening period. Toluene was unaffected by the ripening time and the use of starter culture. This compound might result from the cyclization of unsaturated carbonylic chains produced by lipid degradation (Meynier and others 1999).

Conclusions

Both starter culture strains showed a good growth during the fermentation, and remained in high amounts during drying. NPN values are increased in the presence of these strains. TBARS value is increased with the ripening time; however, this increase occurred in higher amounts at the end of ripening in group with starter culture in comparison with the control. Terpenes are the major volatile compounds in sucuk. Other volatile compounds (aldehydes, ketones, sulfur compounds, acids, esters, aliphatic hydrocarbons, aromatic hydrocarbons, alcohols) can be found in less amounts. While the use of starter culture was affecting a few compounds, ripening period had affected most of the compounds. Starter culture did not show the expected effect, probably due to a rapid decrease in the pH.

Ancillary