Razvoj in aplikacija analitske metode za določanje vsebnosti proteinskih karbonilov v piščančjem mesu ; Development and application of an analytical method for determining the content of protein carbonyls in chicken meat

Namen magistrskega dela je bil razviti analitsko metodo za določanje vsebnosti produktov oksidacije beljakovin, t.j. proteinskih karbonilov. Znanih je več različnih metod za določanje proteinskih karbonilov, proučili smo njihove prednosti in pomanjkljivosti ter izbrano metodo (Soglia in sod., 2016) prilagodili naši analitski opremi in možnostim. Izbrana metoda je temeljila na spektrofotometričnem določanju vsebnosti karbonilov. Tvorbo karbonilov smo ovrednotili z merjenjem absorbance (370 nm) sproščenih hidrazonov, ki nastanejo zaradi reakcije karbonilnih skupin z 2,4-dinitrofenilhidrazinom (DNPH). Karbonili so med produkti oksidacije beljakovin najbolj zastopani produkti. Metodo za določanje proteinskih karbonilov smo preverili na mesu piščančjih beder, na katerih smo proučevali tudi vplive obogatitve z n-3 večkrat nenasičenimi maščobnimi kislinami (VNMK) ter vpliv časa skladiščenja in načina pakiranja (glede na vsebnost kisika) na oksidacijske produkte lipidov (peroksidno število in število tiobarbiturne kisline (TBK)) ter instrumentalne vrednosti barve CIE L*a*b*. Ugotovili smo, da ima meso, obogateno z n-3 VNMK, ožje razmerje n-6/n-3 (3,9) kot neobogateno (9,7). Na podlagi določanja produktov oksidacije ugotavljamo, da obogatitev mesa z n-3 VNMK vpliva na število TBK (1,6-krat večje kot pri neobogatenem mesu) in intenzivnost barve površine, ne pa na vsebnost proteinskih karbonilov. Med devetdnevnim skladiščenjem mesa beder sta se povečali vsebnost karbonilov in povišalo število TBK. Pri večji koncentraciji kisika v embalažni enoti se je od opazovanih parametrov povišalo le število TBK. ; The purpose of the master’s thesis was to develop and verify an analytical method for determination of the content of protein oxidation products, namely protein carbonyls. There are several different methods for the determination of protein carbonyls. Their advantages and disadvantages were studied and the method chosen. The selected method (Soglia et al., 2016) was based on the spectrophotometric determination of protein carbonyls. Carbonyl formation was determined by measuring the absorbance (370 nm) of the released hydrazones formed due to the reaction of carbonyl groups with 2,4-dinitrophenylhydrazine (DNPH). Carbonyls are among the most represented products of protein oxidation. The analytical method was verified on the meat from chicken legs. Meat enrichment with n-3 polyunsaturated fatty acids (PUFA n-3) and the influence of the time of storing and the method of packing (with regards to the content of oxygen) on the oxidation products of lipids (peroxide number and number of thiobarbituric acid (TBK)) and instrumentally measured color (CIE L*a*b*) were also studied. Meat enriched with n-3 FA was demonstrated narrower n-6/n-3 ratio (3.9) than the non-enriched meat (9.7). On the basis of oxidation product determination, it can be concluded that the meat enrichment with PUFA n-3 affects the TBK (1.6-times higher as in the case of non-enriched meat), the intensity of the color. However, it does not affect the content of protein carbonyls. In the time of nine-days storing of the meat of chicken legs, the content of carbonyls and TBK increased. Among all the observed parameters only the TBK increased at higher concentrations of oxygen in the packaging unit.