Abstract
The profile of volatile compounds of a typical Turkish dry fermented sausage (sucuk) were analyzed by gas chromatography/mass spectrometry (GC-MS) using a solid phase microextraction (SPME). The significant differences were found in the volatile profiles obtained in the five commercial brands analyzed. A total 92 compounds were identified. The volatile compounds were consisted of 5 acids, 7 esters, 10 aliphatic hydrocarbons, 7 alcohols, 5 aldehydes, 11 sulphur compounds, 2 ketones, 7 aromatic hydrocarbons, 27 terpenes, 2 nitrogen compounds, 3 phenols, and 6 compounds BCH. Terpenes were the chemical family with the highest proportion in four brands, ranged 56–76% of the total area of volatiles. Acids were major compounds (32%) in only one brand.
INTRODUCTION
Sucuk is a typical dry-fermented meat product produced in Turkey. It is produced from beef meat and/or water buffalo meat, beef fat, sheep tail fat, salt, sugar, nitrite/nitrate and various spices such as garlic, red pepper, black pepper, cumin, allspice.Citation[1] In spite of increasing use of starter culture in production of sucuk in the industry, natural fermentation by the indigenous bacteria is still performed by some producers. Another feature of the sucuk is that it is not smoked like some typical European sausages. Small diameter casings are normally used in the production of sucuk, which has a short ripening period.Citation[2]
The acceptability of fermented meat products by the consumer is strongly influenced by the final flavor. The typical flavor and odor of dry-fermented sausages cannot be attributed to volatile substances alone, but to a large number of volatile and nonvolatile compounds present in the product in suitable proportions.Citation[3] The volatile compounds contribute to aroma of dry fermented sausage.Citation[4,Citation5] The enzymatic and chemical phenomena involved in flavor generation include carbohydrate fermentation, lipolysis, proteolysis, lipid oxidation and amino acid catabolism.Citation[6,Citation7] These processes are influenced by endogenous and microbial enzyme activities, and also chemical reactions dependent on the technological processing.Citation[8]
The volatile compounds of dry and semi–dry fermented sausages have been widely studied in recent years.Citation9–16 However, there are only two studies on the volatile compounds of sucuk. The first study involves the identification of aromatic components of sucuk (experimentally) which are produced by different commercial starter cultures, using steam distillation and GC.Citation[17] Another study determined the effects of Staphylococcus xylosus and Lactobacillus plantarum isolated from sucuk on the formation of volatile compounds during the ripening period.Citation[18] There is no information on the volatile compounds of sucuk (traditional or industrial) available in the market. This study aims to determine the volatile compounds of traditionally produced sucuk.
MATERIALS AND METHODS
Samples
Ten samples were taken from the sucuk produced by five different firms at two different times. After taking samples for pH and aw analyses, the samples were frozen and stored at −20°C until the volatile compounds analysis was performed. Samples from the first date were analyzed by two replicates and samples from the second date were analyzed by three replicates.
Determination of pH and Water Activity
The pH was measured in a homogenate of the sample with distilled water (1:10 w/v) using a pH meter (ATI ORION 420, USA). Water activity (aw) was determined using a TH-500 aw sprint apparatus (Novasina).
Analysis of Volatile Compounds
SPME fibers
The extraction of headspace volatile compounds was done using a SPME device (Supelco, Bellefonte, PA), 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.
Procedure
For each analysis, 5 g of sucuk were minced and weighed into a 40 ml headspace vial and sealed with a PTFE-faced silicone septum (Supelco, Bellefonte, PA, USA). The vial was left at 30°C in a thermo block (Supelco, Bellefonte PA, USA) during 1 h to equilibrate its headspace. Then, a SPME fiber was exposed to the headspace while maintaining the sample at 30°C during 2 h. The compounds absorbed by the fibers were identified by gas chromatographic analysis using MS detectors.
Identification and Quantification of Volatile Compounds
The compounds adsorbed by the fiber were desorbed from the injection port of the gas chromatography (GC, Agilent Technologies 6890N) for 6 min at 250°C with the purge valve off (splitless mode). The compounds were separated in a DB-624 (J&W Scientific, 30 m, 0.25 mm i.d., 1.4 μm film) 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 started to increase as programmed 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 50–500 uma. The compounds were determined by comparing the results with mass spectra from a database developed by NIST and WILEY or standards molecules (for calculating Kovats Index, Supelco 44585-U, Bellefonte PA, USA) 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 were expressed as means of five replicates for each firm.
Statistical Analysis
The analyses of data were tested by varience analysis (complete randomized design) and differences between means were evaluated by Duncan's multiple range test using SPSS statistic program.Citation[19]
RESULTS AND DISCUSSION
The pH values of the analyzed samples varied between 4.64 and 5.18. These values are in accordance with the pH values of traditionally produced sucuk.Citation[2] The water activity values of sucuk varied from 0.87 to 0.91. This variation was probably due to differences in ripening time. A total of 120 compounds were isolated and 92 of these were tentatively identified and estimated as 5 acids, 7 esters, 10 aliphatic hydrocarbons, 7 alcohols, 5 aldehydes, 11 sulfur compounds, 2 ketones, 7 aromatic hydrocarbons, 27 terpenes, 2 nitrogen compounds, and 3 phenols ().
Table 1 Profiles of volatile compounds in five brands of sucuk
Berger and co-workersCitation[9] identified 68 different compounds in salami whereas Mateo and ZumalacarreguiCitation[20] identified 115 different compounds in chorizo (traditional and industrial). One hundred ninety-three different compounds were isolated from the five analyzed commercial brands of chorizo de Pamplona.Citation[15] In another study on the effects of commercial starter cultures on aromatic compounds, 13 compounds were identified in control group (without starter culture), 16 compounds in sucuk samples containing lactic starter culture, and 29 compounds in samples with lactic acid bacteria and S. xylosus.Citation[17] These findings differed from the findings of this study. This may be a result of different methods employed in both studies.
Volatile acid compounds make up between 0.85–32% of the total area of volatiles. Acetic acid was detected in all samples. Moreover, significant differences among brands were observed (P < 0.01). Only acetic acid was determined in Brand A (). In dry fermented sausages, some studies showed the presence of acetic acid.Citation[12, Citation18] Ansorena and co-workers[15] and Meynier and co-workersCitation[13] did not determine this compound. Acetic acid produced by lactic acid bacteria and staphylococci contributes to aroma of dry sausage. This compound may also be formed by lipid oxidation and amino acid catabolism.Citation[8] Hexadecanoic acid was only detected in Brand B and butanoic acid was found in brand C. The amount of other acids was extremely low.
Percentages of esters ranged between 0.62% and 3.32% of the total area, with different profiles depending on the brands. In sucuk, typical ester was ethylacetate in all samples (P < 0.001). Butanoic acid, ethyl ester was found in four of the five brands. 11 ester compounds that contributed up to 10% of the total amount of volatiles were also isolated by Ansorena and co-workersCitation[15] from another type of dry fermented sausage, “Chorizo.” They may have originated from esterification of alcohols and acidsCitation[15], with certain microbial activities.Citation[15,Citation21] Esters were not always found in fermented sausage.Citation[9] However, StahnkeCitation[21] reported that certain ethyl esters were essential for sausage aroma. On other hand, the formation of ethyl esters were affected by the addition of nitrite and lactic acid bacteria.Citation[5]
Aliphatic hydrocarbons accounted for percentages referred to the total area that between 0.14% and 8.03%. Undecane, dodecane and tetradecane were detected in all sausages, but dodecane was not significant (P > 0.05). These compounds do not contribute significantly to the aroma of dry cured meat products because of their threshold value.Citation[22] Seven different alcohols were isolated from among the five analyzed brands. Benzenemethanol, 4- (1-methylethyl) was present in all sausages. This compound was higher in Brand B. It was also the only alcohol in brand A. In fermented dry sausage, lipid oxidation, carbohydrate metabolism, and amino acid catabolism could be the most important pathways accounting for the production of volatile alcohols.Citation[20]
Propanal-2-methyl-3-phenyl was determined in all samples with significant differences among compounds (P < 0.05). p-cumin aldehyde was identified in three brands. There are very significant differences (P < 0.0001) among brands. Cumin aldehyde is an important aldehyde originated from cumin. This was also identified by ErcoşkunCitation[17] in sucuk. On the other hand, benzaldehyde and nonanal were identified in sucuk ripened with starter culture (L. plantarum + P. pentosaceus + S. xylosus).Citation[17] Hexanal, which is considered as an indicator of lipid oxidation, was found to be present in all samples from four brands (). High concentrations of hexanal signal flavor deterioration in meat products often resulting in a rancid aroma.Citation[22]
Sulfide, allyl methyl, and 1-propene-3,3’thiobis were identified in all samples. Differences are statistically significant (P < 0.001). Propene 1,3, epithio and diallyl disulfide were determined in Brand A in significant amounts. Aliphatic sulfur compounds such as diallyl disulfide and dimethyl disulfide have been identified in garlic.Citation[13] A wide variety of sulfur compounds are derived from allicin, which is one of the major compounds in garlic.Citation[22,Citation23] Garlic is an important ingredient in sucuk production, which can be used in different amounts.Citation[18] The proportions of ketones were quite low. 2-butanone 4-hydroxy-3-methyl has been detected in one of the five brands. On the other hand, β- elemene was detected in one brand.
Toluene and p-xylene were aromatic hydrocarbons that were detected in all samples. Benzene,1,2,3,-trimethyl, Naphthalene and eugenol were detected in three brands. Toluene might result from the cyclization of unsaturated carbonylic chains produced by lipid degradation.Citation[13] Xylene and styrene, on the other hand, were present in plants liable to the eaten by animals.Citation[10,Citation13] Eugenol was essentially originated from pimento. This spice is known to have antioxidant activity and contains eugenol as its main active component.Citation[24]
Terpenes were the chemical group with the highest proportion (range between 56.11% and 76.32% of total area) in all samples from four brands. Major group was acids in one brand, followed by terpenes (25.56%). The variability observed among the brands in the content of terpenes showed that different amount of spices had been added in the production of the different brands.Citation[15] β- pinene, β- myrcene, α-phellandrene, 3-carene, D-limonene, 4-cymene, o-cymene, γ-terpinene and caryophyllene were detected in all samples. D-Limonene, 4-cymene, o-cymene, and γ–terpinene were found significantly in terms of area. Compounds such as α-thujene, α-pinene, camphene, sabinene, β-pinene, β–myrcene, α-phellendren, limonene, γ–terpinene, p-cymene, and linalol were detected in pepper.Citation[25] Spices are important ingredients in sucuk production. Total amount of spices in sucuk can sometimes be as high as 5%, which is normally 3%.Citation[2] The proportion of nitrogen compounds was low (0–1.99%). Percentage of phenolic compounds for the samples ranged between 0.04 and 3.13% of total area. This proportion is low since sucuk is an air-dried fermented sausage.
CONCLUSIONS
Sucuk contained higher level of terpenes from spices, which showed strong aromatic notes and could play an important role in the overall aroma notes of this meat product. Other important compounds were acids (especially acetic acid), sulfur compounds (diallyl disulfide, 1, propene 3-thiobis, disulfide methyl 2-phenyl) and aldehydes (p-cumic aldehyde). There are significant differences between brands. These differences in the volatile profiles of sucuk samples may be explained by the differences in raw materials, spices and other ingredients, and production conditions.
Related Research Data
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