Influence of the olive leaf extract addition (Olea europaea) on physico-chemical characteristics and fermentation of cow's milk

Fermentirani mliječni proizvodi danas su vrlo popularni zbog visoke nutritivne i zdravstvene vrijednosti. U svrhu poboljšanja njihovog djelovanja, mogu se obogaćivati različitim dodacima. Kako bi se iskoristili svi dijelovi biljnog materijala, iz otpada zaostalog nakon proizvodnje ekstrakcijskim se metodama izdvajaju potencijalno biološki aktivne komponente. Ekstrakt lista masline (Olea europaea) ima dokazane brojne pozitivne učinke na ljudsko zdravlje zahvaljujući prisutnim bioaktivnim kemijskim spojevima, ponajprije fenolima. Cilj ovog diplomskog rada bio je proizvesti jogurt obogaćen ekstraktom lista masline (1,5; 3 i 5 %, v/v) te ga usporediti s jogurtom bez dodanog ekstrakta. Svim uzorcima određeni su aktivna i titracijska kiselost, viskoznost, boja, sinereza i kapacitet zadržavanja vode, mikrobiološki parametri, senzorski profil, ukupni fenoli i antioksidacijska aktivnost DPPH i FRAP metodom. Dodatak ekstrakta lista masline uzrokovao je kraće trajanje fermentacije (za 6, 14 odnosno 36 min, ovisno o količini ekstrakta), nižu pH vrijednost (4,42; 4,35 tj. 4,45) u usporedbi s kontrolnim uzorkom (4,53), povećani udio ukupnih fenola te povećani antioksidacijski kapacitet jogurta. Uzimajući u obzir sve dobivene rezultate, dodatak 1,5 % ekstrakta lista masline pokazao se optimalnim.Fermented dairy products are very popular today due to their high nutritional and health value. In order to improve their action, they can be enriched with various additives. In order to use all parts of the plant material, potentially biologically active components are extracted from the waste remaining after production by extraction methods. Olive leaf extract (Olea europaea) has proven a number of positive effects on human health thanks to the bioactive chemical compounds present, primarily phenols. The aim of this thesis was to produce yoghurt enriched with olive leaf extract (1.5, 3 and 5 %, v/v) and compare it with yoghurt without its addition. In all the samples active and titratable acidity, viscosity, color, syneresis and water retention capacity, microbiological parameters, sensory profile, total phenols and antioxidant activity by DPPH and FRAP method were determined. The addition of olive leaf extract caused shorter fermentation (6, 14 and 36 min, depending on the amount of extract), lower pH (4.42, 4.35 or 4.45) compared to the control sample (4.53), increased proportion of total phenols and antioxidant capacity of yoghurt. Taking into account all the results obtained, the addition of 1.5 % olive leaf extract proved to be optimal