Comparison of antioxidative and synergistic effects of different antioxidants in emulsions

Namen diplomske naloge je bil določiti najučinkovitejši antioksidant oziroma kombinacijo antioksidantov v emulziji. Emulziji tipa (O/V) smo dodali različne antioksidante in tako dobili 13 vzorcev. Vzorce smo pospešeno starali tri mesece pri 50 °C. Vsak teden smo določili stopnjo oksidacije vzorcev. Stopnjo oksidacije smo določili s pomočjo dveh metod: peroksidnega in p-anisidinskega števila. Jodometrična določitev peroksidnega števila je titrimetrična metoda, s katero določamo primarne oksidacijske produkte hidroperokside. Hidroperoksidi so nestabilne spojine brez vonja in okusa. Določitev p-anisidinskega števila je spektrofotometrična metoda, s katero določamo sekundarne oksidacijske produkte. Sekundarni oksidacijski produkti, gre predvsem za aldehide in ketone, nastanejo z razpadom hidroperoksidov in dajejo maščobam značilne lastnosti žarkosti. Uporaba obeh metod nam omogoča celosten vpogled v oksidacijo emulzije. Ugotovili smo, da se je stopnja oksidacije v splošnem iz tedna v teden povečevala. Opazili smo tudi nekatera odstopanja, ki jih je mogoče pojasniti s pretvorbo primarnih produktov v sekundarne in nadalje z razpadom sekundarnih produktov. Najnižjo stopnjo oksidacije smo izmerili vzorcu, ki je vseboval komercialno dobavljivo mešanico antioksidantov. Zelo dobre rezultate smo opazili tudi pri slepem vzorcu. Menimo, da je razlog za to mandljevo olje v emulziji, ki je bogat vir vitamina E, ta pa je močan naravni antioksidant, ki očitno v kombinaciji z drugimi antioksidanti izgubi svojo učinkovitost. Najslabše se je odrezal vzorec, ki je vseboval oljetopne komponente ekstrakta rožmarina.The purpose of this diploma thesis was to determine the most efficient antioxidant or a combination of antioxidants in an emulsion. By adding various antioxidants to a type (O/V) emulsion, we obtained 13 samples. The samples were acceleratory aged for three months, at a temperature of 50°C. Every week we determined the rate of samples’ oxidation. We determined the oxidation rate by using two methods: a Peroxide Value and a p-Anisidine Value. An iodometric determination of Peroxide Value is a titrimetric method which we use to determine primary oxidation products – hydroperoxides. Hydroperoxides are unstable compounds without scent and taste. Determining a p-Anisidine Value is a spectrophotometric method which we use to determine secondary oxidation products. Secondary oxidation products, mostly aldehydes and ketones, result from hydroperoxide degradation and give fats distinctive characteristics of rancidity. Using both methods enables us with an overall insight in emulsion’s oxidation. We found out that, in general, the oxidation rate increased from week to week. We also observed some deviations that can be explained by transformation of primary products into secondary and further with degradation of secondary products. The lowest oxidation rate was measured in a sample which contained a commercially available antioxidant mixture. Very good results were also noticed in the blank sample. We believe that the cause for that is presence of almond oil in emulsion which is a rich source of vitamin E. The latter is a powerful natural antioxidant that, apparently, in combination with other antioxidants losses its efficiency. The sample with the worst performance was a sample which contained oil-soluble components of rosemary extract