<p>Promene komponenata i strukture mleka ispitane su tokom fermentacije korišćenjem inokuluma kombuhe kultivisane na crnom čaju zaslađenom saharozom<br />u koncentraciji 10%. Fermentacija mleka sa 2,2% mlečne masti izvršena je na dve različite temperature (37°C i 42°C) i uzorci su analizirani na sledećim pH vrednostima: 6,1; 5,8; 5,4; 5,1; 4,8 i 4,6. Urađena je determinacija i identifikacija produkata fermentacije laktoze kao što su: šećeri, organske kiseline i masne kiseline. Ispitane su teksturalne i reološke karakteristike i mikrostruktura uzoraka. Pored toga, utvrđene su sličnosti i razlike uticaja inokuluma kombuhe na proces fermentacije mleka u poređenju sa delovanjem jogurtne, odnosno probiotske starter kulture.<br />Tokom fermentacije mleka u različitim fazama procesa pri odabranim pH vrednostima na 42°C transformiše se 14,6% laktoze odnosno 18,2% na 37°C. Sadržaj galaktoze i glukoze koje nastaju fermentacijom i hidrolizom laktoze raste između prve i druge tačke fermentacije (pH=6,07 i pH=5,8). Dominantne organske kiseline tokom fermentacije su L–mlečna kiselina i sirćetna kiselina. Nije utvrđena značajna razlika u sadržaju masnih kiselina tokom fermentacije mleka kombuhom na 37°C i 42°C. Sadržaj palmitinske kiseline u mleku i uzorcima tokom fermentacije je najveći, zatim slede miristinska, stearinska i oleinska kiselina.<br />Praćenjem procesa fermentacije mleka uz primenu kombuhe na 37°C i 42°C od početne pH vrednosti 6,07 do završne 4,6, najznačajnije promene teksturalnih karakteristika (čvrstoće, konzistencije, kohezivnosti i indeksa viskoziteta) i reoloških svojstava zabeležene su između pH=5,4 i 5,1, što je u korelaciji sa mikrostrukturom. Promene viskoziteta u svim uzorcima pokazuju istu regresionu liniju, sa različitim koeficijentima i visokom vrednošću r2, osim uzorka proizvedenog primenom jogurtne kulture na pH 5,4. Uzorak dobijen korišćenjem inokuluma kombuhe imao je najveće vrednosti kompleksnog modula, što je rezultiralo boljim reološkim karakteristikama gotovog proizvoda.<br />Da bi se definisao empirijski model procesa fermentacije laktoze u mleku delovanjem kombuhe formulisana su prethodno dva matematička modela za kinetiku fermentacije saharoze u tradicionalnom kombuha napitku (na crnom čaju) – jedan koji opisuje promenu koncentracije saharoze tokom fermentacije, i drugi koji opisuje brzinu fermentacije. Promena koncentracije laktoze na ispitivanim temperaturama 37°C i 42°C sastoji se od dve lag faze između kojih je faza izraženog pada koncentracije. Krive zasićenja pokazuju sigmoidalnu kinetiku na nižim koncentracijama laktoze, ukazujući na kompleksni ne–Michaelis–Mentenov tip kinetike.<br />Generalno može se istaći da su primenom inokuluma kombuhe tokom fermentacije mleka u različitim fazama procesa ustanovljene specifične promene komponenata i strukture u poređenju sa efektima delovanja jogurtne odnosno probiotske starter kulture.</p><p> </p> / <p>Changes of milk components and structure were examined during fermentation by kombucha inoculum cultivated on black tea switened with saccharose in a concentration of 10%. The fermentation of milk with 2.2% of milk fat was carried out at two different temperatures (37°C i 42°C) and samples were analyzed at the following pH values: 6.1; 5.8; 5,4; 5.1; 4.8 and 4.6. Determination and identification of the lactose fermentation products, such as: sugars, organic acids and fatty acids were carried out. Textural and rheological characteristics and microstructure of the samples were investigated. Furthermore, the effect of kombucha on the milk fermentation process was compared with the effect of yoghurt and probiotic starter culture.<br />During milk fermentation at various stages of the process 14.6% of lactose content was transformed at 42°C and 18.2% at 37° C. The galactose and glucose content, which are formed by lactose hydrolyses and fermentation, increased between first and second pH point of fermentation (pH = 6.07 and pH = 5.8). Dominant organic acids during fermentation are L–lactic acid and acetic acid. There is no significant difference between samples in fatty acids content during fermentation on 37°C and 42°C. The level of palmitic acid in milk and samples was the highest of all fatty acids, followed by myristic, stearic, and oleic acid.<br />The most significant changes in textural properties (firmness, consistency, cohesiveness and viscosity index) and viscosity during milk fermentation by kombucha at 37ºC and 42°C, from the initial pH value 6.07 to a final 4.6, were recorded between pH=5.4 and 5.1, which is in correlation with microstructure.<br />Viscosity changes in all samples showed the same regression line with the different coefficients and a rather high r2 except for the sample produced with standard yoghurt culture at the pH 5.4. Samples produced with kombucha had the highest values of the complex modulus, which indicates better rheological characteristics of the final product.<br />In order to define an empirical model of lactose fermentation process in milk by kombucha, two mathematical models (one for the change of saccharose concentration, during its fermentation by kombucha, and the other for the rate of the mentioned fermentation) previously were formulated. Change of lactose concentrations at 37ºC and 42ºC consists of two retaining stages and very steep descend in-between. Saturation curves show a sigmoidal kinetics at low lactose concentrations, indicating a complex non–Michaelis–Menten type kinetics.<br />Generally it can be concluded that specific changes in the components and structure of milk by application of kombucha inoculum during fermentation at different stages of the process were established in comparison with the effects of yoghurt and probiotic starter culture.</p>
| Identifer | oai:union.ndltd.org:uns.ac.rs/oai:CRISUNS:(BISIS)90483 |
| Date | 29 December 2014 |
| Creators | Kanurić Katarina |
| Contributors | Milanović Spasenija, Carić Marijana, Lončar Eva, Maćej Ognjen |
| Publisher | Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, University of Novi Sad, Faculty of Technology at Novi Sad |
| Source Sets | University of Novi Sad |
| Language | Serbian |
| Detected Language | English |
| Type | PhD thesis |
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