diplomsko delo
Lara Krašna (Author), Helena Brodnik Žugelj (Mentor)

Abstract

Sladoled velja za eno najbolj priljubljenih živil po celem svetu. Gre za kompleksno živilo, kjer vsaka komponenta igra pomembno vlogo pri zagotavljanju in oblikovanju kakovostnega produkta. Eno izmed pomembnejših komponent sladoledne mase predstavljajo proteini. Glavni vir proteinov v sladoledni industriji predstavljajo mlečni proteini. Mleko vsebuje kazeine in sirotkine proteine, ki imajo pri proizvodnji kakovostnega sladolednega izdelka številne pomembne vloge za zagotavljanje ustrezne strukture. Zato je za proizvajalce pomembno, da izberejo ustrezen vir proteinov za zagotavljanje želenih funkcionalnih lastnosti končnega izdelka. V diplomskem delu smo želeli semi-kvalitativno določiti vsebnost posameznih proteinov, ki so prisotni v različnih mlečnih surovinah. Za ločevanje tovrstnih proteinov sirotkinih surovin smo uporabili nativno poliakrilamidno gelsko elektroforezo, za ločevanje kazeinskih frakcij mlečnih surovin pa SDS poliakrilamidno gelsko elektroforezo brez uporabe reducenta.Analizirali smo več različnih vzorcev kazeinskih in sirotkinih surovin, kjer smo na podlagi intenzitete lis in relativne vsebnosti posameznih vrst proteinov določili primerno koncentracijo surovin za dosego ustrezne ločljivosti ločbe. Določili smo naslednje približne koncentracije surovin za dosego primerne ločbe: 5 mg/mL za surovino posnetega mleka v prahu, 8 mg/mL za surovino sirotke v prahu, 5 mg/mL za surovino nadomestka mleka v prahu, 3 mg/mL za surovino polnomastnega mleka in 1 mg/mL za surovine koncentrata sirotkinih proteinov 80, koncentrata sirotkinih proteinov 80 z reducirano laktozo, izolata sirotkinih proteinov 90 in micelarnega koncentrat kazeinov 80. Poleg standardizacije ločevanja posameznih proteinov smo analizirali tudi kako se proteini obnašajo pri različni časovni izpostavljenosti visoki temperaturi in spremembi pH vrednosti okolja. Za analizo smo uporabili nativno poliakrilamidno gelsko elektroforezo. Denaturacija sirotkinih proteinov se z daljšanjem toplotne obdelave povečuje. Pri izpostavljenost 85 °C, daljši od 5 minut, večina proteinov ireverzibilno zdenaturira. Denaturacija je opažena pri vzorcih, ki niso toplotno obstojni. Pri toplotno obstojnih vzorcih denaturacija, ne glede na časovno izpostavljenost, ni opazna. Analizirali smo tudi vpliv spremembe pH vrednosti. Pri kisanju okolja proteinov med pH vrednostima 5,0 in 4,0 pride do pojava obarjanja proteinov. Proteini se v okolici izoelektrične točke (okrog pH 4,6) oborijo in ne vstopajo v gel.

Keywords

sladoled;kazeini;sirotkini proteini;poliakrilamidna gelska elektroforeza;bližnja infrardeča spektroskopija;NIR;diplomska dela;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher: [L. Krašna]
UDC: 547.96:543.545.2(043.2)
COBISS: 185834755 Link will open in a new window
Views: 18
Downloads: 3
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Other data

Secondary language: English
Secondary title: Optimization of the separation of milk and whey proteins by PAGE analysis
Secondary abstract: Ice cream is considered as one of the most popular foods around the world. It is a complex food in which each component plays an important role in ensuring and creating a quality product. Proteins are one of the most important components in ice cream. The main source of proteins are milk proteins. Milk contains caseins as well as whey proteins, which have several important structural roles in the production of quality ice cream products. Therefore, it is important that manufacturers choose the appropriate protein source of the final product. In this thesis we wanted to semi-qualitatively determine the type of proteins present in various dairy raw materials. Native polyacrylamide gel electrophoresis method was used for the separation of whey proteins and native SDS polyacrylamide gel electrophoresis was used to separate proteins from casein raw materials. We analysed several different samples of dairy raw materials where we determined the appropriate concentration to achieve the optimal separation resolution. We determined the following approximate concentrations: 5 mg/mLforskimmed milk powder, 8 mg/mL for whey powder, 5 mg/mL for milk substitute powder, 3 mg/mL for whole milk powder and 1 mg/mL for whey protein concentrate 80, whey protein concentrate 80 with reduced lactose, whey protein isolate 90 and micellar casein concentrate 80. In addition to determining the optimized standard conditions for the separation of individual proteins, we also analysed how the proteins behave during different periods of exposure of high temperature and changes in the pH value of the protein environment. Native polyacrylamide gel electrophoresis was used for analysis. Denaturation of whey proteins increases with longer heat treatment. When exposed to 85 °C for longer than 5 minutes, most proteins are irreversibly denatured. Denaturation is observed in samples that are not heat stable. In heat stable samples, denaturation is not noticeable. We also analysed the influence of the change in pH value. When the protein environment is acidified between pH values 5.0 and 4.0, protein precipitation occurs. Proteins precipitate around the isoelectric point (around pH 4.6) and do not enter the gel.
Secondary keywords: ice cream;caseins;whey proteins;polyacrylamide gel electrophoresis;Mlečne beljakovine;Univerzitetna in visokošolska dela;
Type (COBISS): Bachelor thesis/paper
Study programme: 1000373
Thesis comment: Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, UNI Kemija
Pages: 1 spletni vir (1 datoteka PDF (30 str.))
ID: 22925925