Praćenje kvalitativnih promjena mlijeka obrađenog različitim toplinskim režimima

master's thesis

• Title (english): Monitoring of qualitative changes in milk processed at different thermal treatments
• Author: Jakov David Milić
• Mentor: Irena Barukčić (mentor)
• Committee member: Tamara Jurina (član povjerenstva)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Food Engineering); (Laboratory for Technology of Milk and Milk Products); Zagreb
• Defense date and country: 2021-09-28, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Cilj ovog rada bio je odrediti kako različiti toplinski tretmani koji se primjenjuju u proizvodnji mlijeka utječu na kvalitetu kravljeg mlijeka; prije svega na formiranje hidroksimetilfurfurala (HMF), promjene u antioksidacijskoj aktivnosti (DPPH, FRAP) i sadržaju ukupnih fenola, stupanj denaturacije proteina, promjene u indeksu boje, vodljivosti, ukupne otopljene tvari. Istraživanje je provedeno na uzorcima sirovog mlijeka obrađenog različitim toplinskim režimima u laboratorijskim uvjetima (63-65 °C/15 sec; 63-65 °C/30 min; 72 °C/20 sec; 85 °C/30 sec; 90-95 °C/5-10 min; 116 °C/16 min; 120 °C/5 min), na uzorcima mlijeka u prahu te na uzorcima kupovnog konzumnog svježeg i trajnog mlijeka. Temeljem dobivenih rezultata može se zaključiti kako povišenjem temperature i trajanja obrade dolazi do povećanja koncentracije HMF-a, antioksidacijskog potencijala mjerenog FRAP metodom te izmjerenih vrijednosti ukupnih fenola, dok sposobnost redukcija radikala pomoću DPPH pada. Isto tako, povećanjem intenziteta toplinskog režima povećavaju se vrijednosti ukupnih otopljenih tvari i električna vodljivost. Povećanje temperature uzrokuje denaturaciju proteina što je vidljivo provođenjem SDS PAGE elektroforeze, a najveća promjena boje zabilježena je kod steriliziranih uzoraka. Primjenom analize glavnih komponenata (Principal Component Analysis, PCA) utvrđene su sličnosti među testiranim uzorcima u odnosu na primijenjen toplinski režim. Navedeni parametri mogu poslužiti kao indikatori intenziteta toplinske obrade mlijeka te poslužiti u detekciji patvorenja mlijeka dodatkom mlijeka u prahu.

Abstract (english)

The aim of this study was to investigate the effect of different heat treatments on the quality of milk; formation of hydroxymethylfurfural (HMF), to determine the effect of heat treatments on antioxidant activity (DPPH, FRAP), total phenols content, the degree of protein denaturation, color changes, electric conductivity, total dissolved solids. The research was conducted on samples of raw milk treated with different temperatures in laboratory conditions (63-65 °C/15 sec; 63-65 °C/30 min; 72 °C/20 sec; 85 °C/30 sec; 90-95 °C/5-10 min; 116 °C/16 min; 120 °C/5 min), on samples of milk powder and on samples of fresh and Ultra-High Temperature (UHT) milk from the supermarkets. Based on the conducted research, it can be concluded that by increasing the temperature and duration of processing, there is an increase in the concentrations of HMF, antioxidant activity (FRAP) and total phenols content, while DPPH values decrease. In addition, there is an increase in total dissolved solids and electrical conductivity. The degree of protein denaturation in different heat treatments of milk was determined by SDS-PAGE electrophoresis; due to higher heat treatment, protein denaturation occurred and the largest color change was measured on samples of UHT milk. Principal Component Analysis (PCA) revealed similarities between the tested samples in relation to the applied thermal regime. These parameters can be used as indicators of the intensity of heat treatment of milk and for determination of milk adulteration by the addition of powdered milk.

• Keywords: mlijeko; HMF; antioksidacijska aktivnost; fenolni spojevi; PCA
• Keywords (english): milk; HMF; antioxidant activity; phenolic compounds; PCA
• Language: croatian
• URN:NBN: urn:nbn:hr:159:994511
• Study programme: Title: Food Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka prehrambenog inženjerstva (magistar/magistra inženjer/inženjerka prehrambenog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-10-19 09:36:31