doktorska disertacija
Tanja Potočnik (Avtor), Iztok Jože Košir (Mentor), Nives Ogrinc (Član komisije za zagovor), Rajko Vidrih (Komentor)

Povzetek

Namen raziskave je bil določiti vpliv temperature praženja bučnih semen na kemijsko sestavo bučnega olja. Bučna olja smo pražili pri temperaturah od 90 do 200 °C, en vzorec je ostal nepražen kot kontrola. S pomočjo tekočinske kromatografije smo v vzorcih bučnega olja določili pet policikličnih aromatskih ogljikovodikov (PAHov), ki se tvorijo pri temperaturi 150 °C. Njihove koncentracije nato naraščajo z naraščanjem temperature praženja. Določili smo tudi komponente arome z mikroekstrakcijo na trdni fazi in nadaljno določitvijo s plinsko kromatografijo. Pri nižjih temperaturah praženja prevladujejo razni aldehidi in alkoholi, pri najvišjih uporabljenih temperaturah praženja pa razni derivati pirazina, ki so nosilci pražene arome. Vsebnosti α- in γ-tokoferolov se z naraščanjem temperature bistveno ne spreminjajo, medtem ko koncentracija identificiranih polifenolov se. S praženjem naraste, nato pa z nadaljnjim višanjem temperature njihova koncentracija znatno upade. Antioksidacijski potencial, določen s pomočjo radikala 2,2-difenil-1-pikrilhidrazil (DPPH), narašča do temperature praženja 110 °C in nato pada. Za določitev geografske pristnosti smo zbrali vzorce bučnih semen iz štirinajstih različnih držav, jim določili maščobnokislinsko ter sterolno sestavo s plinsko kromatografijo ter razmerja stabilnih izotopov ogljika z masnim spektrometrom. Na podlagi teh rezultatov in z uporabo kemometrije smo lahko ločili med sabo celo vzorce iz sosednjih držav (Slovenije, Avstrije ter Hrvaške). Enake analize smo opravili za določitev botanične pristnosti, kjer smo vzorcem bučnega olja dodali sojino, sončnično ter repično oljem, v količinah od 1 do 10 ut.%. Z uporabo kemometričnih metod, upoštevajoč rezultate maščobnokislinske sestave in razmerij stabilnih izotopov ogljika (13C/12C), smo dosegli 100% pravilno ločitev, in to celo pri najmanjšem dodatku, 1 %.

Ključne besede

bučno olje;bučna semena;Cucurbita pepo L.;praženje;vpliv temperature;PAH;HPLC-FLD;aroma;SPME;GC;MS;pirazini;ekstrakcija;barva;tokoferoli;polifenoli;antioksidacijski potencial;DPPH radikal;kislinsko število;jodno število;saponifikacijsko število;peroksidno število;avtentičnost;geografsko poreklo;botanična pristnost;maščobnokislinska sestava;steroli;izotopska razmerja ogljika;GC-C-IRMS;kemometrija;

Podatki

Jezik: Slovenski jezik
Leto izida:
Tipologija: 2.08 - Doktorska disertacija
Organizacija: UL BF - Biotehniška fakulteta
Založnik: [T. Potočnik]
UDK: 664.34:635.62:543.635.3
COBISS: 4916856 Povezava se bo odprla v novem oknu
Št. ogledov: 1633
Št. prenosov: 858
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

Sekundarni jezik: Angleški jezik
Sekundarni naslov: Determination of botanical and geographical origin and seeds roasting influence on chemical composition of pumpkin seed oil
Sekundarni povzetek: The purpose of this study was to determine the influence of seed roasting temperature on chemical composition of pumpkin seed oil. Pumpkin seeds were roasted at temperatures from 90 to 200 °C, one sample was left unrosted as control. In pumpkin seed oil samples five polycyclic aromatic hydrocarbons (PAHs) were determined by high performance liquid chromatography. The PAHs started to form at 150 °C and their concentrations increased with the increase of temperature. Volatile aroma compounds were also determined by means of solid phase microextraction (SPME), followed by gas chromatography. Aldehydes and alcohols prevailed at low roasting temperatures, while higher temperatures caused the formation of pyrazines, which resemble a roasted-like aroma. The concentrations of α- and γ-tocopherol did not change significantly with the increase of temperature, whereas polyphenol concentrations did change. At the beginning of roasting they increased and decreased as the temperature increased further. Antiradical activity was determined via 2,2-diphenyl-1-picrylhidrazyl (DPPH) method, its values were increasing till 110 °C and decreased afterwards. To verify the geographical origin, pumpkin seed samples from different countries were collected and analysed on fatty acid and sterol composition by gas chromatography as well as on stable isotope ratios by mass spectrometry. On the basis of these results and combination with chemometrics we were able to distinguish even the samples from neighbouring countries (Slovenia, Austria, Croatia). These analyses were also used to determine the botanical authenticity. For this purpose rapeseed, sunflower and soybean oil were added to pumpkin seed oil in varying ratios (1-10 %(w/w). The results confirmed that the combination of fatty acid profiles and δ13C values, combined with chemometrics, gave 100% correct classification even when only 1 % of foreign oil was added.
Sekundarne ključne besede: pumpkin oil;pumpkin seeds;Cucurbita pepo L.;roasting;effect of temperature;PAH;HPLC-FLD;aroma;SPME-GC;MS;pyrazines;extraction;colour;tocopherols;polyphenols;antioxidant activity;DPPH radical;acid value;iodine value;saponification value;peroxide value;authenticity;geographical origin;botanical genuiness;fatty acid composition;sterols;stable isotope carbon ratio;GC-C-IRMS;chemometry;
Vrsta dela (COBISS): Doktorsko delo/naloga
Študijski program: 0
Konec prepovedi (OpenAIRE): 1970-01-01
Komentar na gradivo: Univ. v Ljubljani, Biotehniška fak.
Strani: IX, 62 f.
ID: 10939776