20.500.12556/RUL-116001 Reološke lastnosti jogurta masovne in domače proizvodnje Rheological properties of yoghurt of mass and domestic production Jogurt spada med fermentirane mlečne izdelke. Pridobimo ga s fermentacijo mleka, kjer bakterije mlečni sladkor pretvarjajo v mlečno kislino. Pri tem mleko koagulira in dobimo značilno gel strukturo jogurta. Cilj diplomske naloge je bil ugotoviti, kako način proizvodnje jogurta vpliva na njegove reološke lastnosti. Eksperimentalno delo smo opravili na dveh vzorcih jogurta. Prvi je bil masovne proizvodnje, drugi pa domače izdelave. Izvedli smo rotacijske in oscilacijske teste, s katerimi smo vzorcema določili tokovne lastnosti, ter ugotavljali spreminjanje viskoelastičnih lastnosti med amplitudnim in frekvenčnim testom. Razlike med vzorcema jogurta so bile razvidne že iz tokovnega testa, kar smo nato potrdili še z ostalima dvema poskusoma. Izkazalo se je, da jogurt masovne proizvodnje prenese višje strižne napetosti kot jogurt domače izdelave preden ta steče. Oba vzorca sta imela ozko območje linearnega odziva, kar lahko pripišemo notranji strukturi materiala. Iz frekvenčne odvisnosti obeh dinamičnih modulov smo pri obeh vzorcih opazili, da je prevladujoč elastični doprinos nad viskoznim. Ob povečevanju obremenitve znotraj linearnega odziva s časom pri vzorcu ne pride do podiranja strukture. Dokazali smo, da spadata oba vzorca med zelo strukturirane viskoelastičene materiale, ki izkazujejo lastnosti bolj podobne tekočinam. Iz dobljenih rezultatov meritev tako lahko zaključimo, da način izdelave jogurta vpliva na njegove reološke lastnosti. Yogurt is a fermented dairy product. It is obtained by fermenting milk, where bacteria convert milk sugar into lactic acid. During this process, the milk coagulates and the characteristic gel structure of the yogurt is obtained. The aim of the diploma thesis was to determine how the production of yoghurt affects its rheological properties. Experimental work was performed on two yogurt samples. The first was obtained from a mass production, while the second one was home-made. We performed rotational and oscillation rheological tests to determine the flow characteristics of the samples, and to determine viscoelastic properties. The differences between the two yoghurt samples were already evident from the flow test, and were confirmed also by oscillatory amplitude and frequency test. It turned out that prior to flowing mass-produced yogurt withstands higher shear stresses compared to home-made yogurt. Both samples exhibited narrow range of linear viscoelastic response, which can be attributed to the internal structure of the material. From the frequency dependence of both dynamic modules, we observed that the elastic contribution dominated over the viscous one in both samples. It has been shown for both samples that they behave as highly structured viscoelastic materials with fluid-like properties. Thus, we can conclude from the results of the measurements that the method of manufacturing affects the rheological properties of the produced yogurt. reologija reološke lastnosti domači jogurt jogurt masovne proizvodnje rheology rheological properties homemade yogurt mass produced yogurt true false false Slovenski jezik Angleški jezik Diplomsko delo/naloga 2020-05-06 12:45:01 2020-05-06 12:45:12 2022-08-28 03:46:44 0000-00-00 00:00:00 2020 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 5990 14201091 Muzga_Nika_-_Reoloske_lastnosti_jogurta_masovne_in_domace_proizvodnje.pdf Muzga_Nika_-_Reoloske_lastnosti_jogurta_masovne_in_domace_proizvodnje.pdf 1 2693A8BC0ADDE92C6F46758901D175EB bccb7e0c4ebfb3b356084e9a6ba483ab165c891d7eb03e5a388d1c0f3c5f9680 cb2fda0d-a1b8-11eb-a523-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=129394 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0