Katarina Lukić

Differentiation of dry-cured hams from different processing methods by means of volatile compounds, physico-chemical and sensory analysis

The aim of this study was to characterize dry-cured hams from four different processing methods (differences in primary leg treatment, salting and smoking phase). Volatile compounds were isolated by using headspace-solid phase microextraction and analysed by gas chromatography/mass spectrometry (GC/MS). Samples were also evaluated by sensory and physico-chemical characteristics (moisture, protein, fat and NaCl content, aw, colour). 149 volatile compounds of dry-cured hams were identified and 15 of them were quantified. Identified volatile compounds belonged to several classes of chemical: 25 aldehydes, 18 phenols, 12 alcohols, 16 terpenes, 27 aromatic hydrocarbons, 18 aliphatic hydrocarbons, 17 ketones, 9 esters and 7 acids. Most abundant volatiles in ham samples were aldehydes (34.46-49.78%). Principal component analysis showed a good separation among groups. Smoked dry-cured hams showed a higher content of phenols, aromatic hydrocarbons, and acids and were characterized by smoky aroma, while non-smoked dry-cured hams showed higher content of terpenes, ketones, alcohols, esters, aliphatic hydrocarbons and were characterized with spicy aroma.

Comparison of Proteomic, Metabolic, and Growth Profiles for Brettanomyces bruxellensis Isolates from Croatian Wines

Brettanomyces bruxellensis is one of the most important spoilage yeasts in red wine production. The aim of this paper was to investigate the diversity of B. bruxellensis isolates in regard to their proteomic, growth, and metabolic profiles. Ten isolates were obtained from several wineries in Croatian winegrowing regions during different phases of wine production. Proteomic analysis revealed 12 proteins that were expressed by all tested isolates and the reference strain. These proteins could be used as biomarkers in Dekkera/B. bruxellensis yeast identification. Five of these proteins were involved in carbohydrate metabolism (enolase, hxk2p, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, and pyruvate decarboxylase), and four were involved in protein biosynthesis (elongation factor 1-alpha, eukaryotic translation initiation factor 5a, 60s ribosomal protein 13, and putative cytosolic ribosomal protein s24). One each was involved in cellular stress responses to glucose starvation (heat shock protein ssb1); ubiquitin conjugation pathways such as transcription, proteolysis trafficking, and kinase activation (ubiquitin); or nitrogen metabolism (peptidyl-prolyl cis-trans isomerase). Isolates identified as B. bruxellensis and taken during malolactic fermentation expressed 18 similar proteins, and isolates from aging in steel vessels/wood barrels or bottled wine expressed 23 and 24 similar proteins, respectively. Growth and metabolic profiles of these isolates were evaluated in two growth media (glucose complex and wine-mimicking media). The growth profiles of the tested isolates and conversion of hydroxycinnamic acids varied among the investigated media in that the use of glucose complex medium resulted in faster growth and consumption of hydroxycinnamic acids and in higher production of volatile phenols and esters. The results obtained suggest the possibility of applying proteomic fingerprinting for the identification and differentiation of B. bruxellensis wine isolates and reveal different spoilage capacities, such as growth and metabolic profiles, of the tested isolates.