Comparison of Traditional and Industrial Sausages Baranjski Kulen and Kulenova Seka Using Comprehensive Proteome, Peptidome and Metabolome Techniques

Abstract

Research background: Baranjski kulen is one of the most popular fermented meat sausages originating from Croatia. It has protected geographical indication, and is traditionally produced in the Baranja region of Croatia. Kulenova seka is a fermented sausage very similar to baranjski kulen, but it has a different calibre and consequently, a shorter time of production. In recent decades, due to the high demand and popularity of these products, industrially produced baranjski kulen and kulenova seka have become available on the market. This work aims to identify specific characteristics of traditional and industrial sausages baranjski kulen and kulenova seka on proteome, peptidome and metabolome level, which could potentially lead to better optimization of the industrial production process in order to obtain an equivalent to the traditional product.

Experimental approach: Protein profiles of baranjski kulen and kulenova seka (traditional and industrial) were analysed using two-dimensional gel electrophoresis followed by differential display analysis and protein identification by mass spectrometry. Peptidomic profile was analysed via liquid chromatography-tandem mass spectrometry. Furthermore, aroma profiles were investigated via headspace solid phase microextraction and gas chromatography-mass spectrometry.

Results and conclusions: The major identified characteristics of each product were: industrial baranjski kulen: specific degradation of myosin-1 and titin, overabundance of stress-related proteins and increased phenylalanine degradation; traditional baranjski kulen: decreased concentration of phenylalanine and overabundance of fructose-bisphosphate aldolase A and carbonic anhydrase 3; industrial kulenova seka - specific myosin-4 and haemoglobin subunit alpha degradation process; traditional kulenova seka - overabundance of dihydropyrimidine dehydrogenase [NADP(+)] and myosin light chain 1/3, skeletal muscle isoform, degradation of albumin and myoglobin, decreased concentrations of almost all free amino acids and increased amounts of smoke-derived volatile compounds. Presented results showed that potential product type-specific quality markers for each sausage could be found.

Novelty and scientific contribution: In this preliminary communication, the first insights into protein degradation processes and generation of peptides, free amino acids and aroma compounds of industrial and traditional baranjski kulen and kulenova seka are presented. Although further research is needed to draw general conclusions, the specific profile of proteins, peptides, amino acids and volatile compounds represents the first step in the industrial production of sausages that meet the characteristics of traditional flavour.

Keywords: aroma profile; baranjski kulen; industrial fermented sausage; kulenova seka; peptidomics; proteomics; traditional fermented sausage.

Fig. 1

A master gel from a 2-DE gel electrophoresis showing differentially expressed soluble protein fractions isolated from industrial and traditonal baranjski kulen, and industrial and traditonal kulenova seka. Black crosses show protein spots that are differentially expressed among products. Protein spots are identified after mass spectrometry analyses and gene names are linked to each spot. Number after gene name is attached to proteins identified in more than one spot. Densitometric values of each spot and mass spectrometry results are shown in Table 1. N.I.=not identifed spot

Fig. 2

Free amino acid composition of industrial and traditional baranjski kulen and kulenova seka. Error bars represent the standard deviation for each product. Different letters represent statistically significant differences among products. Asx=aspartic acid and asparagine, Ser=serine, Glx= glutamic acid and glutamine, Gly=glycine, His=histidine, Arg=arginine, Thr=threonine, Ala=alanine, Pro=proline, Val=valine, Met=methionine, Lys=lysine, Ile=isoleucine, Leu=leucine and Phe=phenylalanine