Reološka svojstva koncentrata proteina sirutke prije i nakon tribomehaničke mikronizacije

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

Emulgirajuća svojstva tribomehanički obrađenih proteina sirutke

Whey proteins are used in a wide range of food products because of their high nutritional value and the ability to contribute to the unique functional properties of the final products. The functional properties of whey proteins are affected not only by the whey origin, season dependent variations of protein and non-protein components amount, but also by the conditions of processes involved in their isolation, purification and modification (temperature, pH, pressure, chemicals). In this research, tribomechanical micronization (TM) was used as a technique that could be useful in modification of some functional properties of whey proteins. Therefore, two different commercial powdered whey protein isolates (WPI) were used for analysis. Surface hydrophobicity and emulsifying properties (emulsifying activity and emulsion stability) were determined before and after TM treatment. The results obtained showed increases in surface hydrophobicity of WPI after TM treatment indicating that TM could induce changes of protein conformation and increase exposure of the previously buried hydrophobic regions. Emulsions prepared with tribomechanically treated WPI showed higher emulsion activity and better emulsion stability. The results obtained suggest that TM can be useful and fast process technique for improvement of functional properties of WPI.Proteini sirutke upotrebljavaju se u velikom broju prehrambenih proizvoda zbog njihove visoke nutritivne vrijednosti i jedinstvenih funkcionalnih svojstava. Funkcionalna svojstva proteina sirutke ovise ne samo o podrijetlu sirutke, sezonski ovisnih količina proteinskih i neproteinskih komponenti, već i o uvjetima procesa koji su uključeni u njihovu izolaciju, pročišćavanje i modifikaciju (temperatura, pH, tlak, kemijski dodaci). U ovom radu, tribomehanička mikronizacija (TM) je korištena kao potencijalna tehnika za unapređenje pojedinih funkcionalnih svojstava proteina sirutke. Analizirana su dva različita komercijalna izolata proteina sirutke u prahu (WPI). Površinska hidrofobnost i emulgirajuća svojstva (sposobnost stvaranja emulzija i stabilnost emulzije) određena su prije i poslije TM obrade. Dobiveni rezultati su pokazali povećanje površinske hidrofobnosti WPI nakon TM obrade što ukazuje na činjenicu da TM može izazvati konformacijske promjene proteina i povećati izloženost prethodno skrivenih hidrofobnih područja. Emulzije pripremljene s tribomehanički obrađenim WPI pokazale su veću aktivnost i bolju stabilnost emulzija. Dobiveni rezultati ukazuju da TM može biti učinkovita tehnika za poboljšanje funkcionalnih svojstava WPI

Utjecaj dodataka stabilizatora na reološka svojstva modelnih sladolednih smjesa

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

Nutrition Labelling on Food Products

Obveza svih proizvođača hrane jest osigurati visoku razinu zaštite potrošača, što znači da proizvedena hrana mora biti zdravstveno ispravna i pravilno deklarirana te treba osigurati da potrošač dobije sve relevantne informacije o proizvodu kojega kupuje. Hrana na tržištu Europske unije će od prosinca 2016. morati biti označena podatcima o hranjivoj vrijednosti. Stvarne hranjive vrijednosti hrane mogu se razlikovati u odnosu na deklarirane vrijednosti, stoga je važno definirati i navoditi prosječnu hranjivu vrijednost na proizvodu. Prosječna vrijednost je vrijednost koja najbolje predstavlja količinu hranjivih tvari koju hrana sadrži, uključujući sve čimbenike koji dovode do odstupanja od stvarne vrijednosti. U najvećem broju zemalja prihvatljiva odstupanja navedenih hranjivih vrijednosti hrane u odnosu na analitičke vrijednosti nisu definirana propisima nego nacionalnim vodičima. Europska komisija je krajem 2012. godine pripremila vodič za hranu i dodatke prehrani radi primjene jedinstvenih kriterija za prihvatljiva odstupanja, a što je predviđeno i novom Uredbom (EU) br.1169/2011 Europskog Parlamenta i Vijeća od 25. listopada 2011. o pružanju potrošačima informacija o hrani i označavanju hrane. Vodič ima za cilj da kroz utvrđena dozvoljena odstupanja osigura potrošačima točne informacije o kvaliteti hrane te služi kao pomoć proizvođačima hrane i nadležnim institucijama prilikom službenih kontrola hrane. U radu su prikazani primjeri prihvatljivih odstupanja kod označavanja hranjive vrijednosti hrane koji vrijede u pojedinim zemljama s posebnim osvrtom na one iz Europske unije te rezultati istraživanja provedenih na nekim tržištima o sukladnosti stvarnih hranjivih vrijednosti hrane s onima navedenim na deklaraciji, uvažavajući dozvoljene tolerancije po pojedinim tržištima.Obligation of all food producers is to ensure a high level of consumer protection, which means that food must be produced as safe and properly declared and ensure that the consumers receive all relevant information about the products they buy. From December 2016 in the European Union food have to be labelled with nutrition data. Since the actual nutritional value of food can vary in relation to the declared value, it is important to define and specify the average nutritional value of the product. The average value is the quantity that best represents the amount of nutrients contained in food, including all factors that cause deviations from the true value. In most countries there is no clear definition of acceptable tolerances for nutritional values of food in relation to the analytical values in the appropriate regulations of national guidelines. At the end of 2012th European Commission prepared the guide for foods and food supplements to apply the uniform criteria for acceptable tolerances, which has been provided in the new Regulation (EU) No. 1169/2011. Through established tolerances the new guide aims to provide accurate information to consumers concerning the quality of food and to help food manufacturers and competent institutions during the official control work. This paper shows on the one hand some examples of acceptable tolerances for nutritional values on food labelling in several countries, with the special emphasis on those in the European Union, on the other hand presents research work conducted in some countries related to conformity of the real nutritional value with those listed on the label, taking into account the allowed tolerance by individual market

Influence of low temperatures on the viscosity and sensoric properties of dairy desserts

U ovom radu ispitivanje utjecaj brzine zamrzavanja te temperatura i vrijeme skladištenja na viskoznost i senzorska svojstva mliječnih deserata. Ispitivanje je provedeno napet mliječnih deserata pripremljenih miješanjem šećera, žutanjaka jaja, brašna, sirutke, koncentrata proteina sirutke i nekoliko hidrokoloida na osnovi karboksimetilceluloze. Uzorci su smrzavani na dva načina: a)sporo u hladnjaku pri temperaturi od -14° C, b)brzo s tekućim dušikom pri temperaturi od -196° C. Poslije zamrzavanja uzorci su skladištem u hladnjaku 60 dana, pri temperaturi od -14 °C i -28° C, nakon čega im je određena viskoznost pri temperaturi od --4°C i +20 °C. Nakon zamrzavanja i skladištenja viskoznost mliječnih deserata bila je znatno niža nego prije smrzavanja. Viskoznost smrznutih deserata skladištenih pri temperaturi od -14 °C bila je znatno niža nego onih skladištenih pri -28 °C. Viskoznost deserata mjerena pri +20° C bila je oko 30 % manja nego kod +4 °C. Udio hidrokoloida nije imao značajniji utjecaj na viskoznost deserata dok je koncentrat proteina sirutke pokazao značajan utjecaj na viskoznost mliječnih deserata. Ocjena senzorskih svojstava pokazala je, da je najbolja desertna krema pripremljena uz dodatak koncentrata proteina sirutke odmah nakon pripreme. Nakon provedenog zamrzavanja sve desertne kreme bile su slabije senzorski ocijenjene.In this work the influence of rate of freezing as well as storage temperatures and time of storage on the viscosity and senzoric properties of dairy desserts, was investigated. This investigation was carried out on five dairy desserts prepared by mixing sugar, egg yolk, flour, ultraflltrated whey, whey protein concentrate and several carboxymetylcellulose hydrocolloids. Samples were frozen with two different methods: a) slow freezing at the temperature of-14°C, b) quick freezing using liqiud nitrogen (-196 °C). Afler freezing, samples were stored at -14 °C, and - 28 °C. During 60 days afterwards, the viscosity of desserts at 4 °C and 20 °C was determined. After freezing and 60 days of cold storage the viscosity of dairy desserts decreased. Viscosity of frozen desserts stored at -14 °C was significant lower than those stored at -28 °C. Viscosity of dairy desserts measured at +20 °C was about 30 % lower than at +4 °C. Unlike the hidrocolloids the addition of whey protein concentrate had a significant influence on viscosity of dairy desserts. Sensoric evaluation of dairy dessert has shown that the most acceptable was cream preparing with whey protein concentrate immediately after preparation. After freezing lower scores for all dairy desserts were obtained

Influence of composition and freezing process on stability of dairy desserts

U ovom radu ispitivanje utjecaj sastava te procesa smrzavanja i skladištenja na stabilnost mliječnih deserata. Ispitivanje je provedeno sa 12 mliječnih deserata pripremljenih s ultrafiltriranom kiselom ili slatkom sirutkom, šećerom, brašnom, žutanjkom jaja te 6 različitih hidrokoloida na osnovi karboksimetilceluloze. Nakon pripreme uzorci su smrznuti u zamrzivaču pri temperaturi od - 28 °C, te skladištem 100 dana. Uočen je značajan utjecaj pH desertnih krema na viskoznost deserata. Viskoznost desertnih krema mjerena pri 4 °C bila je 30 - 35 % veća nego mjerena pri 20 °C. Nakon smrzavanja i skladištenja viskoznost mliječnih deserata bila je znatno niža nego prije smrzavanja. Elektroprovodnost svih ispitivanih uzoraka značajno je porasla nakon smrzavanja i skladištenja. Senzorska ocjena pokazala je da je najbolje ocijenjena desertna krema pripremljena sa slatkom ultrafiltriranom sirutkom i hidrokoloidom DIKO. Nakon smrzavanja i skladištenja svi deserti bili su slabije ocijenjeni.In this work the influence of composition as well as freezing and storage temperatures on the stability of dairy desserts, was investigated. This investigation was carried out on 12 dairy desserts prepared by mixing of acidic or sweet ultrafiltered whey, sugar, flour, egg yolk and several carboxymetylcellulose hydrocoloids. After preparation the samples were frozen and kept at -28 °C for 100 days. Significant influence of pH on the viscosity of dairy desserts was found. Viscosity of dairy desserts measured at +4 °C was about 30 -35 % higher than those measured at +20 °C. After freezing and 100 days storage, the viscosity of dairy desserts became quite lower than before freezing. Electroconductivity of all investigated samples were higher after freezing and cold storage. Sensoric evaluation has shown that the most accaptable was dessert prepared with sweet ultrafiltered whey and "DIKO" hydrocoloid . After freezing and storage lower scores for all dairy desserts were obtained

Colour stability and antioxidant activity of some berry extracts

The colour stability of the blackberry, mulberry and blueberry extracts by monitoring the changes in colour parameters and remaining absorbance as a result of increased temperature and heating time were examined. The knowledge of colour stability is important for optimization of production and storage of coloured food products. The aim of present study was also to determine and compare the total phenols content and antioxidant activity of these dark coloured berry fruits. The results showed that highest total phenols content was determined in blueberry extracts (3198.50 mg kg-1). Extracts were analyzed for antioxidant activity by the ABTS and DPPH methods. The heating time and temperature affected the colour stability of the berry fruit extracts. The maximum colour stability was determined for mulberry extract

Molecular basis of whey protein functionality

Proteini sirutke čine 18 - 20 % ukupnih proteina mlijeka. Njihova nutritivna vrijednost, uz raznolika fizikalno-kemijska i funkcionalna svojstva, čine proteine sirutke široko primjenjivima u prehrambenoj industriji. Povećani zahtjevi potrošača za ukusnijim, zdravijim, prikladnijim i prirodnijim prehrambenim proizvodima omogućili su mliječnoj industriji priliku za razvijanje i opskrbu prehrambenih proizvoda dodacima sirutkinih proteina kako bi im se povećala funkcionalna i nutritivna svojstva. Razvoj tih dodataka uvelike je ovisio i o prepoznavanju važnosti razumijevanja molekularne osnove funkcionalnosti proteina od strane prehrambenih znanstvenika. Stoga je cilj ovog rada bio na jednom mjestu izložiti osnove funkcionalnosti sirutkinih proteina kao važnog dodatka prehrambenim proizvodima.Whey proteins constitute 18-20% of total milk protein content. Their nutritive value, accompanied by diverse physico-chemical and functional properties, make whey proteins widely applicable in food industry. Highly risen demands of consumers for tastier, healthier, suitable and more natural food products have given dairy industry the opportunity for development and enrichment of food products with whey protein supplements in order to increase their functional and nutritive properties. Development of these supplements mainly depended on recognition of the importance in understanding molecular basis of whey protein functionality from food scientists. Thereby, the aim of this paper is to expose the basis of whey protein functionality at one place, as the important supplement for food products