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Karakterizacija mleka in sira z uporabo stabilnih izotopov lahkih elementov
Vezjak, Urša (Author), Jeršek, Barbka (Mentor) More about this mentor... This link opens in a new window, Ogrinc, Nives (Co-mentor)

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Abstract
V nalogi smo se osredotočili na opis naravnih izotopskih variacij v mlečnih izdelkih iz kravjega, kozjega in ovčjega mleka iz štirih slovenskih makroregij. Kravje mleko je pokazalo statistično značilne razlike v porazdelitvi δ13Ck in δ15Nk iz štirih makroregij (p ⡤ 0,05). V povprečju smo najvišje vrednosti δ13Ck in δ15Nk določili v panonski regiji, najnižje v mediteranski regiji, alpska ter dinarska regija pa je pokazala širok interval δ13Ck in δ15Nk. Izotopska sestava kozjega in ovčjega mleka med geografskim regijami je pokazala manjše razlike kot kravje mleko. S primerjavo vrednosti δ13Ck in δ15Nk med kozjim in ovčjim sirom ter Tolmincem, večjih razlik nismo odkrili. Tolminc je pokazal zelo ozek interval vrednosti, kar povezujemo z geografskimi vplivi manjšega območja zgornjega Posočja. Kravje mleko se od mleka drobnice značilno razlikuje v porazdelitvi δ13Ck, δ15Nk ter δ18O (p ⡤ 0,05). Menimo, da razlike izhajajo iz različnega načina prireje molznih živali, izotopskih obogatitev vode v poletnih mesecih ter drugačnega načina vzorčenja. Z navzkrižnim preverjanjem smo v pravilno geografsko skupino uvrstili 47,8 % vzorcev kravjega, 71,4 % ovčjega in 66,7 % kozjega mleka. Zelo dobre rezultate navzkrižnega preverjanja je pokazalo mleko treh vrst živali, ki je bilo pravilno uvrščeno v 82,9 %. Iz rezultatov sklepamo, da na podlagi izotopske analize lahko mleko in sire le delno ločimo glede na geografsko poreklo ter različno vrsto mleka in sirov iz njih.

Language:Slovenian
Keywords:mleko, mlečni izdelki, sir, izotopi, izotopska sestava ogljika, izotopska sestava dušika, izotopska sestava kisika
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:BF - Biotechnical Faculty
Year:2019
Publisher:[U. Vezjak]
UDC:637.1/.3:544.02
COBISS.SI-ID:5141112 Link is opened in a new window
Views:133
Downloads:99
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Secondary language

Language:English
Title:Characterization of milk and cheese by using stable isotopes of light elements
Abstract:
The main goal of this work was to describe a natural variation of stable isotope ratio in a cow’s, goat and sheep dairy products from Slovenian geographical macroregions. Cow’s milk showed significant difference in the distribution of δ13Ck and δ15Nk in four regions (p ⡤ 0.05). The highest average values were determined in Pannonian region, the lowest in Mediterranean region, while Alpine and Dinaric region showed a great deviation in δ13Ck and δ15Nk values. Milk samples from goat and sheep milk showed smaller deviation in δ13Ck and δ15Nk than cow’s milk among the macroregions. Goat, sheep cheeses and cheese Tolminc didn't show significant difference in δ13Ck and δ15Nk values. Isotopic values of cheese Tolminc were distributed in a small interval, which might reflect geographic condition of upper Soča river region. Cow's milk compared with sheep and goat milk showed significant difference in the distribution of δ13Ck, δ15Nk and δ18O values (p ⡤ 0.05). These differences might originate from use of different farming system, enrichment of water due to evaporation and different sampling system. With cross classification tests 47.8% of cow's, 71.4% of sheep and 66.7% of goat milk samples were correctly classified according to Slovenian macrogeographic region. Milk samples from bovine, goat and sheep species were correctly classified in 82.9%. The results indicate that stable isotopes of bio-elements in dairy products can only partly distinguish between samples from different origin and animal species.

Keywords:milk, diary products, cheese, isotopes, isotopic composition of carbon, isotopic composition of nitrogen, isotopic composition of oxygen

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