Determination of the bioactive properties and volatile compounds of Izmir tulum cheese produced from sheep and goat milk

In this study, İzmir Tulum cheeses were produced from sheep and goat milk with the traditional method and matured at 4±1 °C for 150 days. General composition analysis of cheeses during ripening, proteolysis levels, rheological properties, antioxidant and angiotensin I-converting enzyme (ACE) inhibitory activities of peptides (<3kDa), ureaelectrophoresis and reverse phase-high performance liquid chromatography (RP-HPLC) peptide profiles and gas chromatography-mass spectrometry (GC-MS) volatile compounds were determined. In the first day composition analysis, no significant difference was observed between the cheese varieties, except for the amount of fat and total protein. However, significant differences were determined between cheeses in terms of composition properties during storage (P<0.05). The proteolysis levels of the cheeses were also different from each other during the ripening period. Nitrogen fractions soluble at pH 4.6- and 12% trichloroacetic acid and total free amino acid values of İzmir Tulum cheese produced from goat milk were lower than those produced using sheep milk. Urea-gel electrophoretograms and RP-HPLC peptide profile analyzes of both cheeses were different for all analysis days. In addition, a higher peak numbers and heights were seen in the peptide chromatograms of İzmir Tulum cheese produced from sheep's milk than goat's milk type. While the antioxidant activity of 2,2-azinio-bis-(3ethyl)-benzothiazoline-6-sulfonic acid (ABTS) increased as the ripening progressed for both cheese types, fluctuations were observed in the scavenging capacity of 2,2-diphenyl-1-picrylhydrazil (DPPH) radicals for the cheese Izmir Tulum. It was observed that the interaction of cheese type and ripening time affected the antioxidant capacity of both cheeses (P<0.001). A total of 83 volatile compounds were detected during storage in İzmir Tulum cheeses produced from sheep or goat milk. At the end of ripening, esters were found at the level of 27.62% and alcohols at the level of 30.34% in İzmir Tulum cheese produced from sheep milk, while esters were determined at the level of 44.55% and acids at the level of 22.61% in İzmir Tulum cheese produced from goat milk. It was determined that the type of milk used in the production of İzmir Tulum cheese and the ripening period caused significant changes in the proteolysis, volatile composition, rheological and bioactive properties of İzmir Tulum cheeses. Keywords: Sheep milk, Goat milk, Tulum cheese, Bioactive peptide, Volatile profile