Određivanje slobodnih aminokiselina u vodenim ekstraktima Krčkog sira tijekom zrenja

master's thesis

• Title (english): Determination of the free amino acids in Krk cheese water extracts during ripening
• Author: Vlatka Knežević
• Mentor: Ivone Jakaša (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Chemistry and Biochemistry); (Laboratory for Analytical Chemistry); Zagreb
• Defense date and country: 2011-09-26, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Krčki sir pripada skupini tvrdih punomasnih otočkih, ovčjih sireva koji su proizvedeni od sirovog, toplinski neobrađenog ovčjeg mlijeka u kojemu je sačuvana aktivnost enzima i prirodna mikroflora nestarterskih bakterija mliječno kiselinske fermentacije. Ključna faza proizvodnog procesa polutvrdih i tvrdih sireva je zrenje, čiji tijek izravno utječe na kvalitetu gotovog proizvoda. Tijekom zrenja sira usljed proteolitičkih procesa dolazi do razgradnje kazeina pri čemu nastaju brojni produkti, između ostalih i slobodne aminokiseline koje utječu na formiranje mirisa, okusa i arome sira. U ovom radu određivane su slobodne aminokiseline u uzorcima Krčkog sira u različitim fazama zrenja. U tu svrhu razvijena i validirana je analitička metoda koja se bazira na, derivatizaciji s dabsil kloridom (dabsil-derivati aminokiselina) primjenom reverzno-fazne viokodjelotvorne tekućinske kromatografije uz detekciju u vidljivom području spektra. Razvijena metoda omogućila je kvantificiranje svih aminokiselina, osim lizina i asparaginske kiseline. Sadržaj ukupnih aminokiselina povećavao se s vremenom zrenja, što je u skladu s literaturnim podacima. U ovom radu također je dodatno ispitivana moguća prisutnost biogenih amina koji mogu služiti kao indikator svježine sira. Kvalitativnom kromatografskom analizom primjenom referentnih standarda u ispitivanim uzorcima sira u svim fazama zrenja nije potvrđena prisutnost biogenih amina.

Abstract (english)

Krk cheese belongs to the group of hard full cream island cheeses made of sheep's milk. Krk cheese is produced from raw thermally untreated sheep's milk in which enzyme activity and natural microflora of nonstarter acid bacteria are preserved. The key phase of the production process of the semi-hard and hard cheeses is the ripening phase, which directly affects the quality of the end product. During the ripening of the cheese due to proteolitic processes, degredation of casein occurs which forms numerous products including free amino acids which influence the formation of smell, taste and aroma of the cheese. The goal of this study was to determine free amino acids in Krk cheese samples during different ripening stages. For this purpose analytical method based on derivatisation with dabsil chloride (dabsil-derivative amino acid) and subsequent analysis using reversed-phase high performance liquid chromatography with detection in the visible range was developed and validated. The developed method enabled quantification of all amino acids, except lysine and aspartic acid. The total content of free amino acids increased with the ripening time which coincides with the literature data. Additionally, the presence of six biogenic amines was also tested which may be used as an indicator of the freshness of the cheese. Qualitative chromatographic analysis based on reference standards did not confirm the presence of biogenic amines in any cheese sample.

• Keywords: Krčki sir; slobodne aminokiseline; derivatizacija; HPLC analiza
• Keywords (english): Krk cheese; free amino acids; derivatisation; HPLC analysis
• Language: croatian
• URN:NBN: urn:nbn:hr:159:942396
• Study programme: Title: Food Safety Management; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka upravljanja sigurnošću hrane (magistar/magistra inženjer/inženjerka upravljanja sigurnošću hrane)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-05-31 10:59:01