Utjecaj ultrazvuka na fizikalna i funkcionalna svojstva proteina sirutke

doctoral thesis

• Title (english): Ultrasonic effect on physical and functional properties of whey proteins
• Author: Anet Režek Jambrak; MBZ: 277772
• Mentor: Vesna Lelas (mentor); MBZ: 75494
• Committee member: Branko Tripalo (predsjednik povjerenstva); MBZ: 50483
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; Zagreb
• Defense date and country: 2008-11-27, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology
• Universal decimal classification (UDC): 636/637 - Animal husbandry and breeding. Produce of domestic animals and game

Abstract

Primjena ultrazvuka predstavlja novu metodu ne-toplinske obrade hrane, te se zbog toga željela iskoristiti kao brza metoda, niske energetske potrošnje i vremena tretiranja u usporedbi s tradicionalnim metodama (nekoliko sati obrade). Obrada medija ovim postupkom traje nekoliko minuta i predstavlja novi način obrade sirovine koja se može iskoristiti u dobivanju novih proizvoda i unaprjeđenje tehnološkog postupka što je i svrha rada. U radu se željelo istražiti na koji način ultrazvuk različitih frekvencija, snaga i duljine trajanja tretiranja može utjecati na pojedina funkcionalna svojstva proteina sirutke te modelnih sustava pripremljenih sa proteinima sirutke i različitim dodacima kao što su guar guma, metil celuloza, saharoza te mlijeko u prahu. Ispitivanja su vršena na materijalima izolata, koncentrata, hidrolizata proteina sirutke i α-laktalbumina. Korištene su ultrazvučne sonde od 20 kHz i 30 kHz, te ultrazvučne kupelji od 40 kHz i 500 kHz. Vrijeme tretiranja sa ultrazvukom od 20 kHz, 40 kHz i 500 kHz bilo je 15 i 30 minuta, a sa sondom od 30 kHz 3, 5 i 10 minuta. Ispitivana su svojstva topljivosti, pjenjenja i emulgiranja proteina sirutke, promjene pH vrijednosti suspenzija, elektroprovodljivosti i temperature suspenzija nakon tretmana. Također je ispitan utjecaj ultrazvučnog vala na veličinu čestica, molekularnu masu proteina putem gel elektroforeze, te na viskoznost i termofizičke značajke suspenzija. Ispitivanjem je utvrđeno da tretmani ultrazvukom imaju različite utjecaje na fizikalna i funkcionalna svojstva istraživanih sustava. Na osnovu dobivenih rezultata tretiranjem ultrazvukom od 20 kHz i od 40 kHz kod svih uzoraka proteina, ultrazvuk je uzrokovao smanjenje veličine čestica, te suzio njihovu raspodjelu, osim kod hidrolizata proteina sirutke, a došlo je i do poboljšanja kapaciteta pjenjenja i stabilnosti pjena, te vrijednosti indeksa aktiviteta emulzija. Dodatak metil celuloze, guar gume, saharoze i mlijeka u prahu u modelne sustave, te tretman ultrazvukom od 30 kHz pokazao je različit utjecaj na pojedina ispitivana svojstva.

Abstract (english)

Application of ultrasound in food processing presents novel non-thermal method, with low energy consumption and short treatment time as compared to traditional technological processes. Treatment with this procedure takes few minutes and presents novel method for food processing that can be used for new product development as improvement of technological process what is the purpose of this thesis. The main aim of this thesis was to investigate in what way various ultrasound treatments, with usage of different ultrasound frequencies, power and treatment time, affects functional and physical properties of whey proteins and model systems prepared with whey proteins and diverse supplements like guar gum, methyl cellulose, sucrose and milk powder. The examinations were conducted on powdered whey protein isolates, concentrates, hydrolysates and α- lactalbumin samples. Ultrasound probes of 20 kHz and 30 kHz frequency were used, as well as ultrasound baths of 40 kHz and 500 kHz frequency. Treatment times with ultrasound of 20 kHz, 40 kHz and 500 kHz were 15 and 30 minutes, and with 30 kHz probe 3, 5 and 10 minutes. Investigated whey protein and model system properties were: solubility, foaming and emulsifying properties, pH, conductivity and temperature changes after treatments. Than, the effect of ultrasound on particle size, protein molecular weight using gel electrophoresis, and changes in viscosity and thermophysical properties of suspensions have been investigated. The obtained results showed that ultrasound treatments have different influence on physical and functional properties of investigated systems. Ultrasound treatment with 20 kHz and 40 kHz frequencies caused significant reduction in particle size, and narrowed their distribution, except for whey protein hydrolysates. The same treatment caused improvement in foam capacity and stability, and also increases emulsion activity indexes. Addition of methyl cellulose, guar gum, sucrose and milk powder in combination with ultrasound treatment with 30 kHz showed different influence on investigated properties.

• Keywords: ultrazvuk visoke snage; ultrazvuk niske snage; proteini sirutke; funkcionalna svojstva; fizikalna svojstva
• Keywords (english): high power ultrasound; low power ultrasound; whey proteins; functional properties; physical properties
• Language: croatian
• URN:NBN: urn:nbn:hr:159:327662
• Promotion: 2009-09-13
• Study programme: Title: Postgraduate PhD Study in Nutrition; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje biotehničkih znanosti, polje nutricionizam (doktor/doktorica znanosti, područje biotehničkih znanosti, polje nutricionizam)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2018-05-14 09:38:40