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In this work the influence of temperature and solid matter content on the viscosity of model systems prepared with tribomechanicaly treated as well as untreated whey proteins and skim milk powder was investigated. The rheological properties of model systems were determined using a rotational rheometer Rheometric Scientific RM-180, and described by the Ostwald de Waele &laquo ; ; ; power law&raquo ; ; ; . Signigicantly higher viscosity was found for model systems prepared with tribomechanicaly treated materials compared to those prepared with untreated materials. Systems with higher protein content (WPC-80) exihibited greated viscosity than those with lower protein content (WPC-60). The lowest viscosity was found for systems prepared with skim milk powder. The correlation between viscosity and temperature (0-600C) was determined by an Arrhenius model. Because of a very high regression coefficient (0.91 to 0.98) achieved for the investigated systems, the Arrhenius model can completely describe the viscosity change in the given temperature range. Activation energy of viscous flow was significantly higher for all tribomechanicaly treated systems, because tribomechanical micronisation decreases particles size and enables their better hydration.

Ultrasound is non-thermal food processing technique that has been used in food processing very extensively for the last 10 years. The objective of this study was to investigate the effect of high power ultrasound and pasteurization on rheological properties (n and k) of apple, cranberry and blueberry juice and nectar. Samples were treated according the experimental design, with high power sonicator at ultrasound frequency of 20 kHz under various conditions (treatment time, temperature of sample and amplitude). Thermosonication and sonicaton of juice and nectar samples have been performed. It was found that all samples of untreated, pasteurized and ultrasonically treated apple, cranberry and blueberry juices and nectars shows non-Newtonian dilatant fluid characteristics (n > 1). The interaction of treatment time and temperature of sample (BC) and temperature (C) of sample of apple juice had statistically significant effect on flow behavior index (n) for ultrasound treated apple juice. Interaction of treatment time and temperature of sample (BC) has statistically significant effect on the flow behavior index (n) for blueberry nectar. Also, there is statistically significant effect of temperature (C) of sample on consistency coefficient (k) for ultrasound treated apple juice.

Ultrasound represents a non-thermal food processing technique and has great potential to be used in the food industry. The objective of this research was to observe ultrasound impact on physical properties of model systems prepared with whey protein isolates (WPI) or whey protein concentrates (WPC) with or without sucrose or milk powder addition. This kind of systems is often used in milk beverages and milk based products. Model systems with protein and milk powder or sucrose addition were treated with high power ultrasound (HPU) probe of 30 kHz frequency for 5 and 10 minutes. After sonication several properties were determined and examined: solubility, emulsifying and foaming properties, rheological and thermophysical properties. Ultrasound treatment showed severe influence on all examined properties, caused by protein denaturation as a consequence of cavitation and microstreaming effects. Ultrasound treatment caused decrease in protein solubility for whey protein isolate and whey protein concentrates model systems, compared to untreated sample. There was statistically significant increase in foam volume of model systems, prepared with sucrose or milk powder and WPI after ultrasound treatment. Statistically significant decrease in emulsion activity and emulsion stability indices was observed for model systems prepared solely with isolates and concentrates. After treatment of whey protein model systems (with or without milk powder or sucrose) with 30 kHz ultrasound, the changes in consistency coefficients (k) were observed, but there were no significant changes in flow behaviour indices (n). After addition of milk powder or sucrose, statistically significant decrease in initial freezing and melting temperatures was observed due to the ultrasound treatment., Ultrazvuk je novija netoplinska metoda tretiranja hrane, te ima veliki potencijal primjene u prehrambenoj industriji. Svrha ovog istraživanja je utvrditi utjecaj ultrazvuka na fizikalna svojstva modelnih sustava pripremljenih s izolatima (WPI) i koncentratima proteina sirutke (WPC), sa ili bez dodataka saharoze ili mlijeka u prahu. Takvi se sustavi obično koriste kod mliječnih napitaka na bazi mlijeka. Modelni sustavi s proteinima sirutke i dodacima saharoze ili mlijeka u prahu tretirani su ultrazvukom visoke snage (HPU) frekvencije 30 kHz kroz 5 i 10 minuta. Različiti parametri su ispitivani kao što su: topljivost proteina, svojstva pjenjenja i emulgiranja, te termofizikalna svojstva. Tretman ultrazvukom pokazao je veliki utjecaj na sva ispitivana svojstva, zbog denaturacije proteina uzrokovane kavitacijom i učinkom mikrostrujanja. Pokazalo se smanjenje u topljivosti proteina kod WPI i WPC sustava, u usporedbi s netretiranim uzorcima. Pokazano je značajno povećanje u svojstvima pjenjenja nakon tretmana ultrazvukom kod sustava pripremljenih sa saharozom ili mlijekom u prahu, te WPI-a. Također je pokazano smanjenje emulgirajućih svojstava kod sustava pripremljenih samo s izolatima i koncentratima. Nakon tretmana sustava proteina sirutke (sa ili bez dodataka mlijeka u prahu ili saharoze), zamijećene su promjene u koeficijentu konzistencije (k), ali nisu uočene promjene u indeksu tečenja (n). Nakon dodataka mlijeka u prahu ili saharoze, primijećeno je značajno smanjenje inicijalnih temperatura smrzavanja i odmrzavanja uslijed tretmana ultrazvukom.

U radu je ispitivan utjecaj ultrazvuka visoke snage na reološka svojstva i značajke pjenjenja pojedinih modelnih sladolednih smjesa. Sladoledne smjese pripremljene su prema određenim recepturama, te podvrgnute različitim postupcima homogenizacije: mehaničkom miješanju, tretiranju ultrazvukom te kombinaciji miješanja i ultrazvučnog tretiranja. U radu je korištena ultrazvučna sonda promjera 12,7 mm, amplitude 100% u trajanju pet minuta pri stalnoj temperaturi. Reološka svojstva određivana su na rotacionom reometru i izražena kao indeks tečenja, koeficijent konzistencije i prividna viskoznost. Iz rezultata mjerenja zaključeno je da sve smjese imaju značajke nenewtonskih kapljevina dilatantnih svojstava. Najveću viskoznost imali su uzorci homogenizirani miješanjem u mikseru, a značajno manju oni tretirani ultrazvukom. Svojstva pjenjenja izražena su kao postotak povećanja volumena pjene, indeks stabilnosti pjene, te maksimalna viskoznost. Utvrđeno je da sladoledne smjese tretirane samo mehaničkim miješanjem pokazuju minimalano povećanje volumena pjene, dok je najveće povećanje volumena pjene zapaženo kod sladoledne smjese tretirane kombinacijom mehaničkog miješanja i ultrazvuka. Isto tako sladoledne smjese s većim udjelom proteina pokazale su veću stabilnost pjene. Optimalnim se pokazalo vrijeme tretiranja od 10 minuta., This paper presents research of the high power ultrasound effect on rheological and foaming properties of ice cream model mixtures. Ice cream model mixtures are prepared according to specific recipes, and afterward undergone through different homogenization techniques: mechanical mixing, ultrasound treatment and combination of mechanical and ultrasound treatment. Specific diameter (12.7 mm) of ultrasound probe tip has been used for ultrasound treatment that lasted 5 minutes at 100 percent amplitude. Rheological parameters have been determined using rotational rheometer and expressed as flow index, consistency coefficient and apparent viscosity. From the results it can be concluded that all model mixtures have non-newtonian, dilatant type behavior. The highest viscosities have been observed for model mixtures that were homogenizes with mechanical mixing, and significantly lower values of viscosity have been observed for ultrasound treated ones. Foaming properties are expressed as percentage of increase in foam volume, foam stability index and minimal viscosity. It has been determined that ice cream model mixtures treated only with ultrasound had minimal increase in foam volume, while the highest increase in foam volume has been observed for ice cream mixture that has been treated in combination with mechanical and ultrasound treatment. Also, ice cream mixtures having higher amount of proteins in composition had shown higher foam stability. It has been determined that optimal treatment time is 10 minutes.

Svrha ovog rada je ispitati utjecaj tretiranja visokim hidrostatskim tlakom na reološka i termofizička svojstva modelnih sustava β-laktoglobulina i karagenana. Suspenzije β-laktoglobulina tretirane su visokim hidrostatskim tlakom od 300 do 600 MPa. Vrijeme tretiranja bilo je 5 i 10 minuta. Mjerenja reoloških svojstava modelnih sustava karagenana i β-laktoglobulina provedena su rotacionim reometrom, Rheometric Scientific RM-180 (Rheometric Scientific, Inc., Piscataway, USA), na temperaturi od 20 ºC. Reološki parametri određeni su upotrebom Ostwald de Waele-ovog zakona. Rezultati ispitivanja pokazuju da su svi ispitivani sustavi imali ne-newtonski, pseudoplastični karakter, te da uzorci tretirani visokim hidrostatskim tlakom imaju promijenjene reološke značajke uslijed djelomične denaturacije proteina proporcionalne primijenjenom tlaku i vremenu tretiranja. Temperature faznih promjena određene su metodom diferencijalne termičke analize (DTA). Utvrđeno je da visoki hidrostatski tlak značajno snižava temperaturu zamrzavanja i odmrzavanja modelnih sustava β-laktoglobulina, te da karagenan posjeduje određena krioprotektorska svojstva., The aim of this paper is to examine the influence of high hydrostatic pressure treatment on the rheological and thermophisical properties of β-lactoglobulin and carragenan model systems. Suspensions of β-lactoglobulin were treated with a high hydrostatic pressure in a range of 300 to 600 MPa. Holding period was 5 and 10 minutes. Measurements were performed using rotational viscosimeter Rheometric Scientific RM-180 at 20 oC. The rheological parameters were determined by the Ostwald de Waele law. The results of the investigation have shown that all investigated systems are non-Newtonian – pseudoplastic. All samples treated with high hydrostatic pressure have changed rheological characteristics. The extent of protein denaturation was proportional to the intensity of applied pressure and holding time. The phase transition temperatures were determined by differential thermal analysis (DTA). High pressure treatment caused depression of freezing point and melting point, respectively. Carragenan acts as a crioprotectant.

Investigations with powdered whey protein concentrates containing 60 % (WPC-60) or 80 % (WPC-80) of proteins were carried out. In this work proteins were treated using the laboratory equipment for tribomechanical micronisation with three different rotor speeds. Before and after the tribomechanical treatment, the analyses of the particle size and particle distribution as well as the specific area and scanning microscopy were carried out. The influence of tribomechanical treatment as well as hydrocolloid addition on the rheological properties of model systems of whey protein concentrate (10 % of total solid) was studied. Rheological parameters, flow behavior index (n) and consistency coefficient (k) were determined by the power-law model. The results obtained showed that the tribomechanical treatment involves a significant decrease in particle size, a change in particle distribution and an increase in specific area of powdered whey proteins. Systems without hydrocolloid addition were Newtonian, but those with hydrocolloid addition exhibited pseudoplastic properties. The viscosity of model systems containingn tribomechanically treated whey protein concentrates (TWPC) was greater in comparison with the same systems prepared with untreated WPC. Systems with greater amount of proteins (WPC-80) had higher viscosity than the same systems containing lower amount of proteins. Hydrocolloid addition affected an increase of viscosity of model systems prepared with untreated WPC. The most significant increase of consistency coefficient (k) was observed in systems with carboxymethylcellulose (CMC) and addition of a special type of carboxymethylcellulose (CMC E466) known as DIKO, icecream binder 0911-E. In systems containing tribomechanically treated TWPC hydrocolloids had various effects. In systems with guar gum, carragenan, inulin, pectin or amid pectin, viscosity increased in comparison with those prepared with untreated WPC. CMC and DIKO affected a significant viscosity decrease of TWPC model systems, which is the consequence of the interaction between proteins and (CMC) hydrocolloids. The found effects were pronounced more strongly as the rotor speed of TMA equipment was greater., U ovom su radu istraživanja provedena s praškastim koncentratima proteina sirutke koji su sadržavali 60 % (WPC-60) ili 80 % (WPC-80) proteina. Uzorci su obrađeni u laboratorijskom uređaju za tribomehaničku mikronizaciju i aktivaciju pri trima različitim brzinama okretaja rotora. Prije i nakon tribomehaničke obradbe određena im je veličina i razdioba veličine čestica, te specifična površina, a provedena je i pretražna mikroskopija. Utjecaj tribomehaničke obradbe te dodatka hidrokoloida na reološka svojstva koncentrata proteina sirutke ispitivan je na modelnim sustavima koji su sadržavali 10 % suhe tvari. Reološki parametri, indeks tečenja (n) i koeficijent konzistencije (k), određeni su pomo}u modela potencijalne funkcije. Dobiveni su rezultati pokazali da se tribomehaničkom obradbom bitno smanjuje veličina čestica, mijenja njihova razdioba, te povećava slobodna površina praškastih koncentrata proteina sirutke. Sustavi bez dodatka hidrokoloida imali su newtonski karakter, a oni s dodanim hidrokoloidima uglavnom pseudoplastična svojstva. Utvrđeno je da je viskoznost modelnih sustava s dodatkom tribomehanički obra|enih WPC (TWPC) veća nego istih sustava s dodatkom neobrađenih WPC. Sustavi istog udjela suhe tvari, ali s većim udjelom proteina (WPC-80), imali su veću viskoznost od istih sustava s manjim udjelom proteina (WPC-60). Dodatak hidrokoloida utjecao je na povećanje viskoznosti modelnih sustava pripremljenih s neobrađenim WPC, pri čemu je najznačajnije povećanje viskoznosti izraženo koeficijentom konzistencije (k) utvrđeno u sustavu s dodatkom karboksimetilceluloze (CMC) i dodatka specijalnog tipa karboksimetilceluloze (CMC E466, poznate kao DIKO, vezivo za sladoled). U sustavu s tribomehanički obrađenim proteinima sirutke (TWPC) dodatak je hidrokoloida različito utjecao. U onima s guar gumom, karagenom, inulinom, pektinom i amidiranim pektinom viskoznost se pove}ala u usporedbi sa sustavima s neobrađenim WPC, a u onima s CMC i DIKO viskoznost se smanjila, što je posljedica međudjelovanja između proteina i hidrokoloida. Utvrđeni utjecaji bili su to jače izraženi što je bila veća brzina okretaja rotora pri obradbi WPC-a.

Hydrocolloids are long-chain polymers, used in food production at small quantities (from 0,05 to 5 %) to achieve appropriate rheological properties, prevent syneresis, increase the viscosity and stability of foodstuffs and for crystallization process control. The aim of this work was to investigate the influence of tribomechanical micronization of powdered whey protein concentrate on the rheological properties of whey proteins model systems as well as the influence of several carboxymethylcellulose hydrocolloids addition in such systems. Measurements were done using rotational viscosimeter, Brookfield DV-III at temperature 20 ºC. The rheological parameters were determined by powerlaw model. The results of investigation have shown that all investigated systems are non-Newtonian. Depending on the pretreatment of whey proteins and the mass fractions of hydrocolloids they exhibited pseudoplastic or dilatant properties. Particle size analysis was performed using Fritsch – laser particle sizer “analysette 22”. The operation of tribomechanical micronization caused the decreasing of particle size and incrasing specific area of whey proteins. Tribomechanical treatment of whey proteins had significant influence on the rheological parameters and the type of flowing., Hidrokoloidi su dugolančani polimeri, koji se upotrebljavaju u prehrambenoj industriji u malim količinama (0,05 do 5%) za postizanje odgovarajućih reoloških svojstava, sprečavanje sinereze, povećanje viskoznosti i stabilnosti prehrambenih proizvoda te kontrolu kristalizacije. Cilj ovog rada bio je ispitati utjecaj tribomehaničke mikronizacije koncentrata proteina sirutke u prahu na reološka svojstva modelnih otopina proteina sirutke kao i utjecaj dodatka nekoliko hidrokoloida na osnovi karboksimetilceluloze u takve sustave. Mjerenja su provedena rotacionim reometrom, Brookfield DV-III pri temperaturi od 20 ºC. Reološki parametri određeni su upotrebom zakona potencije. Rezultati ispitivanja pokazuju da su svi ispitivani sustavi ne- Newtonski. Svi sustavi ovisno o prethodnom tretmanu koncentrata proteina sirutke i udjelu hidrokoloida pokazuju pseudoplastična ili dilatantna svojstva. Raspodjela veličine čestica određena je upotrebom Fritsch – laser particle sizer “analysette 22”. Tribomehanička mikronizacija uzrokovala je smanjenje veličine čestica i povećanje specifične površine proteina sirutke. Tribomehanička obrada proteina sirutke imala je značajan utjecaj na reološke parametre i tip tečenja ispitivanih modelnih sustava.

Hidrokoloidi, makromolekularni spojevi uglavnom iz grupe ugljikohidrata, dodaju se pojedinim prehrambenim proizvodima u svrhu postizanja određenih reoloških svojstava, sprečavanja sinereze, povećanja viskoznosti i stabilnosti. U ovom radu ispitivan je utjecaj nekoliko hidrokoloida na osnovi karboksimetilceluloze na reološka svojstva modelnih otopina ultrafiltrirane kisele i slatke sirutke. Mjerenja su provedena pomoću rotacionog reometra Brookfield DV-III, na temperaturi od 20 °C. Reološki parametri određeni su upotrebom Ostwald-Reinerovog zakona. Rezultati ispitivanja su pokazali da svi ispitivani sustavi imaju nenewtonski karakter, te da ovisno o sastavu odnosno pH otopine te udjelu hidrokoloida pokazuju pseudoplastična ili dilatantna svojstva. Svi hidrokoloidi, a posebno YO-EH, značajno su utjecali na povećanje viskoznosti ispitivanih otopina. Uočeno je da su vodene otopine hidrokoloida imale znatno veće vrijednosti viskoziteta od otopina pripremljenih s ultrafiltriranom sirutkom. Modelne otopine pripremljene s ultrafiltriranom kiselom sirutkom imale su znatno manju viskoznost od otopina pripremljenih s ultrafiltriranom slatkom sirutkom., The hydrocolloids, macromolecular carbohydrates, are added in many foodstuffs with the aim to achieve the appropriate rheological properties, to prevent sineresis or to increase the viscosity and stability of food stufs. In this work, the influence of several carboxymetilcellulose hydrocolloids on the rheological properties of sour and sweet ultrafiltered whey model solutions, was investigated. Measurements were performed using viscosimeter, Brookfield DV-III at temperature of 20 °C. Rheological parameters were determined by Ostwald-Reiner's power-law model. The results of investigation have shown that all investigated systems are non-Newtonian. Depending on the chemical composition and pH, as well as, mass fraction of hydrocolloids they exhibited pseudoplastic or dilatant properties. All hydrocolloids, especially YO-EH, caused a significant increase of the solution viscosity. It was observed that aqueous hidrocolloid solutions have significantly higher viscosity values than solutions prepared using sour and sweet ultrafiltrated whey. Significantly lower viscosity was found in solutions prepared with sour ultrafiltrated whey than in model solutions prepared with sweet ultrafiltrated whey.

The quality of ice cream is in great extent determined by its sensoric properties. Therefore, it is important to know and to predict the effect of the hydrocolloid and emulsifier addition on the consistency of the ice cream mixtures. In this work, the influence of several carboxymetylcellulose hydrocolloids (DIKO, YO-EH, HVEP) and emulsifier E-420 (mixture of sorbitol, monoglicerids and diglicerids) on the rheological properties of the model ice cream mixture as well as their ability to prevent crystallization and recrystallization were examined. The rheological properties as well as electroconductivity before and after pasteurization were measured at 20 °C. The results of these investigations have shown that the viscosity of all ice cream mixtures significantly increased after pasteurization. All investigated systems exhibited non-Newtonian characteristics. Hydrocolloid YO-EH showed the greatest influence on the rheological properties of the model systems. After pasteurization conductivity increased for all investigated samples. Sensory evaluation have shown that the most acceptable product was that prepared with emulsifier E-420., Kakvoću sladoleda u velikoj mjeri određuju njegova senzorska svojstva, te je važno znati kakav će utjecaj na njih, posebno na konzistenciju, imati dodatak hidrokoloida odnosno emulgatora. U ovom radu ispitan je utjecaj hidrokoloida na bazi karboksimetilceluloze (DIKO, YO-EH, HVEP) i emulgatora (smjesa sorbitola, monoglicerida i diglicerida, E-420) na reološka svojstva modelnih sladolednih smjesa kao i njihova sposobnost da spriječe kristalizaciju i rekristalizaciju vode te u vodi otopljenih tvari. Reološka svojstva određena su u rotacionom reometru Brookßeld DV-IIl kod temperature od 20 °C prije i poslije pasterizacije. Nakon provedene pasterizacije i smrzavanja izmjerena je provodljivost na konduktometru "Iskra " Kranj pri temperaturi od 20 °C. Rezultati ispitivanja su pokazali da je nakon provedene pasterizacije došlo do značajnog povećanja viskoznosti svih modelnih smjesa. Svi sastavi su pokazali nenewtonski karakter. Najveći utjecaj na reološka svojstva modelnih sustava imao je hidrokoloid YO-EH. Mjerenje elektroprovodljivosti pokazalo je da tijekom pasterizacije te smrzavanja dolazi do kontinuiranog rasta provodljivosti. Ocjena senzorskih svojstava pokazala je da se upotrebom emulgatora E-420 dobiva senzorski najprihvatljiviji proizvod.

Sirutka je zbog svog značajnog udjela proteina, laktoze, vitamina i mineralnih tvari značajan nusprodukt proizvodnje sira. Ipak, još se uvijek ne koristi dovoljno u prehrani ljudi, iako se može upotrebljavati kao dodatak različitim vrstama hrane kao što su sladoled, kolači, keksi, kruh, pića i dr. U ovom istraživanju sirutka je upotrijebljena kao jedna od glavnih komponenti u pripremi mliječnih krema. Kako se te kreme obično konzerviraju smrzavanjem, u ovom radu su Istražena njihova termofizička i reološka svojstava. Reološka svojstva mjerena su pri 20 °Cu rotacionom viskozimetru, a temperature faznih promjena (smrzavanja i odmrzavanja) uz pomoć diferencijalne termičke analize. Njihove temperature smrzavanja bile su između -2 i -5 °C, a temperature odmrzavanja od -9 do -5 °C. Svi deserti bili su pseudoplastična karaktera, a njihova konzistencija je ovisila o udjelu i sastavu suhe tvari. Nakon smrzavanja i 30 dnevnog skladištenja pri -18 °C njihove temperature smrzavanja su se snizile, ali je pseudoplastičan karakter ostao nepromijenjen., Because of its significant amount of proteins, lactose, vitamins and minerals, whey is very Important byproduct In cheese technology. However, It isn't enough used in human nutrition although It could be used as a component of various food products like Ice cream, cakes, bread, drinks etc. In this Investigation it was used as one of the main Ingredients in dairy desserts preparation. As such products are usually preserved by freezing, and in this work were examined their thermophysical and rheological properties. Rheological properties were measured at 20 °C using rotational viscometer and phase transitions (freezing and thawing) temperatures were determined using differential thermal analysis. Freezing temperatures of desserts varied from -2 to -5 °C, and thawing temperatures from -9 to -5 °C. All desserts were pseudoplastic and their consistency depended on fraction and on the composition of solids. After freezing and 30 days' storage at -18 °C, their freezing temperatures decreased but melting temperatures did not change. Consistency Increased, but dairy desserts pseudoplascic character remained unchanged.