Utjecaj ultrazvuka visokog intenziteta na svojstva kravljeg i ovčjeg mlijeka

master's thesis

• Title (english): Influence of high intensity ultrasound on properties of cow and sheep milk
• Author: Ana Sabljić
• Mentor: Suzana Rimac Brnčić (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Process Engineering); (Laboratory for Unit Operations); Zagreb
• Defense date and country: 2010-10-05, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Cilj ovog istraživanja bio je ispitati utjecaj ultrazvuka visokog intenziteta konstantne frekvencije od 24 kHz na promjenu fizikalnih i reoloških svojstava kravljeg i ovčjeg mlijeka, kao i odrediti razlike u dobivenim rezultatima za oba mlijeka. Praćen je utjecaj ultrazvuka visokog intenziteta snage 400 W na temperaturu, pH – vrijednost i gustoću pri sljedećim procesnim parametrima ultrazvuka: amplituda (A = 37,5; 50; 62,5; 75; 87,5; 100 %); vrijeme obrade (t = 2, 6, 10, 15 minuta); primijenjeni ciklus (c = 0,6; 0,8; 1). Utjecaj ultrazvuka visokog intenziteta na prividnu viskoznost, indeks tečenja i koeficijent konzistencije praćen je pri ovim parametrima: amplituda (A = 37,5; 50; 62,5; 75; 87,5; 100 %); vrijeme obrade (t = 2, 15 minuta); primijenjeni ciklus (c = 1). Dobiveni rezultati statistički su obrađeni pomoću programskog paketa „Statistica 8“. Najznačajniji utjecaj ultrazvuka na promatrana svojstva kravljeg i ovčjeg mlijeka bio je na povišenje temperature. Nakon obrade ultrazvukom i u kravljem i u ovčjem mlijeku dolazi do sniženja pH. U kravljem mlijeku dolazi do smanjenja gustoće, a u ovčjem do povećanja. Utvrđeno je da nehomogenizirano, kao i ultrazvučno obrađeno kravlje i ovčje mlijeko imaju nenewtonovski karakter, odnosno da ih karakterizira dilatantan tip tečenja.

Abstract (english)

Main purpose of this research was to study the influence of high-intensity ultrasound with constant frequency of 24 kHz on physical and rheological properties of cow and sheep milk and to compare obtained results. The influence of high-intensity ultrasound (power 400 W) on temperature, pH and density was observed under following conditions: amplitude (A = 37,5; 50; 62,5; 75; 87,5; 100 %); processing time (t = 2, 6, 10, 15 minutes); applied cycle (c = 0,6; 0,8; 1). Also, the influence of high-intensity ultrasound on viscosity, flow index and consistency coefficient was observed under these conditions: amplitude (A = 37,5; 50; 62,5; 75; 87,5; 100 %); processing time (t = 2, 15 minutes); applied cycle (c=1). Obtained results are processed in the „Statistica 8“ software. The most significant influence of ultrasound on cow and sheep milk was observed in an increase of temperature. After ultrasound treatment pH increases in both, cow and sheep milk. Also, it was observed that density decreases in cow milk, but increases in sheep milk. It was found that unhomogenized and homogenized cow and sheep milk exhibit non-newtonian flow behaviour, they are characterized like shear thickening fluids, respectively.

• Keywords: ultrazvuk; kravlje mlijeko; ovčje mlijeko; fizikalna svojstva; reološka svojstva
• Keywords (english): ultrasound; cow milk; sheep milk; physical properties; rheological properties
• Language: croatian
• URN:NBN: urn:nbn:hr:159:278279
• Study programme: Title: Biotechnology; specializations in: Biochemical Engineering; Course: Biochemical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer biotehnologije; smjer biokemijsko inženjerstvo (diplomirani inženjer biotehnologije; smjer biokemijsko inženjerstvo)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-08-29 07:14:40