Uticaj odabranih faktora koagulacije na hemijski sastav seruma dobijenog centrifugiranjem slatkog kazeinskog gela

Technological operations applied during curd processing influence syneresis and total solids content of cheese. Syneresis is not a simple physical process representing whey segregation due to curd contractions. Numerous factors can influence the process of syneresis. The aim of this work was to investigate the influence of various parameters (pH, quantity of CaCl2 added, temperature of coagulation and heat treatment) on induced syneresis. Reconstituted instant skim milk (control samples) and reconstituted instant skim milk heated at 87ºC for 10 min (experimental samples) were coagulated at 30ºC and 35ºC, and pH of 5.8 and 6.2 with 100, 200 and 400 mg/l of CaCl2 added. According to our results, these parameters had significant influence on nitrogen content of serum as well as on the distribution of nitrogen matter from gel into sera. Due to the formation of coaggregates the best rheological properties of gel were obtained for experimental samples coagulated with 400 mg/l of CaCl2 added at pH 5.8 and temperature of 35ºC.Tehnološke operacije koje se primenjuju za vreme obrade gruša, utiču na brzinu sinerezisa i na sadržaj suve materije sira. Sinerezis predstavlja izdvajanje surutke usled kontrakcija gruša i ne predstavlja jednostavan fizički proces. Na brzinu izdvajanja surutke odnosno sinerezis utiče veći broj faktora. U ovom radu je ispitivan uticaj različitih faktora primenjenog termičkog tretmana mleka, pH, količine dodatog CaCl2 i temperature koagulacije na količinu izdvojenog seruma odnosno sinerezis. Rekonstituisano obrano mleko (kontrolni uzorak) i rekonstituisano obrano mleko termički tretirano na 87ºC/10 minuta (ogledni uzorak) je koagulisalo pri različitim temperaturama 30ºC i 35ºC, pH vrednostima 5.8 i 6.2, kao i pri dodatku 100, 200 i 400 mg/l CaCl2. Na osnovu dobijenih rezultata može se zaključiti da ispitivani faktori koagulacije utiču na sadržaj azotnih materija u izdvojenom serumu. Kod oglednog uzorka u kojem je došlo do obrazovanja koagregata proteina mleka najbolje reološke osobine slatkog kazeinskog gela su dobijene pri sledećim uslovima koagulacije: 35ºC, pH 5.8 i dodatku 400 mg/l CaCl2

Utjecaj visokog hidrostatskog tlaka na viskozitet otopina β-laktoglobulina

In this research new experimental data for the pressure dependence of the viscosity of β-lactoglobulin solution are presented. The experimental investigation is based on in-situ viscometric measurement technique which provides an observation of the high-pressure-induced changes of β-lactoglobulin solution during the treatment. This method refers to a rolling ball viscometer that is adapted for the use at high pressures and has a variable inclination angle. The estimation of the viscosity has been done in order to detect reversible and irreversible conformational changes of β-lactoglobulin. For investigation protein solutions concentration 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 g/g were used. The sample solutions are exposed to pressure of 0.1-600 MPa. The results showed that there is no significant effect of 100 MPa pressure on the viscosity of β-lactoglobulin solutions. With increasing pressure, between 100 and 300 MPa, the viscosity of β-lactoglobulin solutions increase. Pressure above 300 MPa causes further increase of the viscosity due to nonreversible and more extensive effects on protein, e.g. unfolding of monomeric proteins and aggregation. The structural changes of the β-lactoglobulin under high pressure affect the hydration of the β-lactoglobulin molecules. At pressure between 100 and 300 MPa there is a significant increase in relative hydration due to structural changes and increase in number of water molecules which are associated with protein molecules. Higher pressure cause protein aggregation due to formation of intermolecular disulfide bonds and irreversible denaturation and aggregation occurs. Because of that, there is no changes in protein hydration, moreover, the hydration of β-lactoglobulin molecules have a small decreases at pressure between 400 and 600 MPa.U radu su prikazani novi eksperimentalni podaci o viskozitetu vodene otopine β-laktoglobulina na visokim tlakovima. Eksperimentalno ispitivanje temeljeno je na primjeni in-situ tehnike mjerenja viskoziteta otopine. Za mjerenja korišten je Rolling ball viskozimetar s različitim kutovima nagiba koji je prilagođen radu na visokim tlakovima. Određivanje viskoziteta otopine vršeno je s ciljem utvrđivanja reverzibilnih i ireverzibilnih promjena strukture molekula β-laktoglobulina. Za eksperimentalna mjerenja korištene su otopine koncentracije 0.01, 0.02, 0.03, 0.04, 0.05 i 0.06 g/g, a izložene su tlakovima od 0.1 do 600 MPa. Rezultati ispitivanja pokazuju da tlakovi do 100 MPa ne utječu bitnije na viskozitet otopine β-laktoglobulina. S povišenjem tlaka, između 100 i 300 MPa, viskozitet otopine značajno raste ukazujući na promjene strukture molekula β-laktoglobulina. Daljnji porast tlaka iznad 300 MPa dovodi do daljnjeg povećanja viskoziteta uslijed nereverzibilnih i izraženijih promjena proteina, denaturacije i agregacije. Strukturne promjene β-laktoglobulina koje su izazvane visokim tlakovima utječu i na hidrataciju molekula β-laktoglobulina. Na tlakovima između 100 i 300 MPa zapaženo je značajno povećanje relativne hidratacije, što može biti posljedica strukturnih promjena s jedne, i povećanja broja molekula vode koje su asocirane s molekulama proteina - s druge strane. Na višim tlakovima javljaju se ireverzibilna denaturacija i agregacija proteina, koja nastaje kao posljedica uspostavljanja intermolekularnih disulfidnih veza. Uslijed toga ne dolazi do povećanja hidratacije molekula β-laktoglobulina, naprotiv na tlakovima između 400 i 600 MPa hidratacija proteina blago se smanjuje

Sadržaj holesterola u mesu pojedinih Cyprinidae

The aim of this paper was to examine cholesterol content in meat of five Cyprinidae species: white bream (Bllica bjoerkna L.), carp bream (Abramis brama L.), baltic vimba (Vimba vimba carinata Pallas), zope (Abramis balerus L.) and crucian carp (Carassius carassius gibelio Bloch) from the river Danube. Cholesterol content was examined in the function of season factor and individual weight. Cholesterol concentration in meat of white bream carp bream, baltic vimba, zope and crucian carp is on average level below 20 mg/100 g of meat, which makes meat of these fish species nutritively very valuable. Cholesterol content is variable during the season. Its concentration in meat and in lipids is lowest during spring, during summer it increases and during autumn decreases, except in meat of white bream. Body weight has influence on cholesterol content when its concentration is expressed as % of cholesterol in lipids. Its content in lipids decreases with increasing of individual weight, except in meat of carp bream.Jedan od najznačajnijih faktora rizika koji dovodi do razvoja ateroskleroze i bolesti srca i krvnih sudova je povišen nivo holesterola u krvi. Stoga je cilj ovog rada bio da se ispita sadržaj holesterola u mesu pet vrsta Ciprinida poreklom iz reke Dunav, u funkciji sezonskog faktora i mase jedinki. Sadržaj holesterola u mesu, svih ispitivanih vrsta riba, je na niskom nivou. Njegova prosečna vrednost tokom perioda proleće-jesen kreće se od 14.85 mg/100g u mesu špicera, do 31.40 mg/100g u mesu krupatice. Sadržaj holesterola, u mesu deverike, plavonosa, špicera i babuške je ispod 20 mg/100g mesa, što su znatno niže vrednosti no u mesu toplokrvnih životinja. Koncentracija holesterola u mesu i u masti najmanja je tokom proleća, tokom leta se povećava, a u toku jeseni smanjuje, osim u mesu krupatice. Masa trupa utiče na sadržaj holesterola u slučaju kada je njegova koncentracija iskazana kao % holesterola u masti. Njegov sadržaj u masti smanjuje se sa povećanjem mase jedinki, osim u mesu deverike

Utjecaj visokog hidrostatskog tlaka na viskozitet otopina β-laktoglobulina

In this research new experimental data for the pressure dependence of the viscosity of β-lactoglobulin solution are presented. The experimental investigation is based on in-situ viscometric measurement technique which provides an observation of the high-pressure-induced changes of β-lactoglobulin solution during the treatment. This method refers to a rolling ball viscometer that is adapted for the use at high pressures and has a variable inclination angle. The estimation of the viscosity has been done in order to detect reversible and irreversible conformational changes of β-lactoglobulin. For investigation protein solutions concentration 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 g/g were used. The sample solutions are exposed to pressure of 0.1-600 MPa. The results showed that there is no significant effect of 100 MPa pressure on the viscosity of β-lactoglobulin solutions. With increasing pressure, between 100 and 300 MPa, the viscosity of β-lactoglobulin solutions increase. Pressure above 300 MPa causes further increase of the viscosity due to nonreversible and more extensive effects on protein, e.g. unfolding of monomeric proteins and aggregation. The structural changes of the β-lactoglobulin under high pressure affect the hydration of the β-lactoglobulin molecules. At pressure between 100 and 300 MPa there is a significant increase in relative hydration due to structural changes and increase in number of water molecules which are associated with protein molecules. Higher pressure cause protein aggregation due to formation of intermolecular disulfide bonds and irreversible denaturation and aggregation occurs. Because of that, there is no changes in protein hydration, moreover, the hydration of β-lactoglobulin molecules have a small decreases at pressure between 400 and 600 MPa.U radu su prikazani novi eksperimentalni podaci o viskozitetu vodene otopine β-laktoglobulina na visokim tlakovima. Eksperimentalno ispitivanje temeljeno je na primjeni in-situ tehnike mjerenja viskoziteta otopine. Za mjerenja korišten je Rolling ball viskozimetar s različitim kutovima nagiba koji je prilagođen radu na visokim tlakovima. Određivanje viskoziteta otopine vršeno je s ciljem utvrđivanja reverzibilnih i ireverzibilnih promjena strukture molekula β-laktoglobulina. Za eksperimentalna mjerenja korištene su otopine koncentracije 0.01, 0.02, 0.03, 0.04, 0.05 i 0.06 g/g, a izložene su tlakovima od 0.1 do 600 MPa. Rezultati ispitivanja pokazuju da tlakovi do 100 MPa ne utječu bitnije na viskozitet otopine β-laktoglobulina. S povišenjem tlaka, između 100 i 300 MPa, viskozitet otopine značajno raste ukazujući na promjene strukture molekula β-laktoglobulina. Daljnji porast tlaka iznad 300 MPa dovodi do daljnjeg povećanja viskoziteta uslijed nereverzibilnih i izraženijih promjena proteina, denaturacije i agregacije. Strukturne promjene β-laktoglobulina koje su izazvane visokim tlakovima utječu i na hidrataciju molekula β-laktoglobulina. Na tlakovima između 100 i 300 MPa zapaženo je značajno povećanje relativne hidratacije, što može biti posljedica strukturnih promjena s jedne, i povećanja broja molekula vode koje su asocirane s molekulama proteina - s druge strane. Na višim tlakovima javljaju se ireverzibilna denaturacija i agregacija proteina, koja nastaje kao posljedica uspostavljanja intermolekularnih disulfidnih veza. Uslijed toga ne dolazi do povećanja hidratacije molekula β-laktoglobulina, naprotiv na tlakovima između 400 i 600 MPa hidratacija proteina blago se smanjuje

Uticaj genotipa sojinog zrna i HTC proizvodnog postupka na aktivnost tripsin inhibitora sojinog mleka

Kunitz inhibitor (KTI) and Bowman-Birk trypsin inhibitor (BBI) are inhibitors of digestive enzymes in raw soybeans. Due to their antinutritive properties in the active state, their inactivation by heat treatment is commonly used. Soymilk is a turbid and stable colloidal solution, obtained by thermal treatment of soybean. In this study soymilk was made on a pilot-plant scale from six soybean cultivars using hydrothermal cooking (HTC) as the production method. This procedure is significantly different from the traditional one. The aim of this investigation was to evaluate the impact of the HTC processing for soymilk production and different soybean genotypes on trypsin inhibitor content and activity. Obtained soymilk contained BBI in trace amounts, in the BBI-polymeric forms. The BBI monomeric forms were not detected. The soymilk of the investigated soybean genotypes had very similar KTI levels (2.34-2.99%). Results have suggested that the soybean genotype does not have substantial effects on the levels of KTI, as well as on the value of residual trypsin inhibitor activity (rTIA). The total content of TI and rTIA showed a strong dependence (r=0.91; p lt 0.05). HTC-soymilk rTIA was lt 20% (7.15-19.89%). These results have indicated that HTC processed soymilk is applicable for human consumption.U sirovoj soji Kunitz-ov (KTI) i Bowman-Birk-ov inhibitor tripsina (BBI) su inhibitori digestivnih enzima. Da bi se poboljšao nutritivni kvalitet hrane od soje, tripsin inhibitori (TI) se inaktiviraju uglavnom termickom obradom. Sojino mleko je mutni i koloidni rastvor, dobijen nakon termičkog tretmana sojinog zrna. U ovoj studiji sojino mleko je napravljeno od šest sorti soje u pilot postrojenju metodom koja uključuje hidrotermičko kuvanje (engl. hydrothermal cooking - HTC). Ovaj postupak se znatno razlikuje od tradicionalnog. Cilj ovog rada je bio da se proceni uticaj HTC postupka za proizvodnju sojinog mleka i različitih genotipova sojinog zrna na sadržaj i aktivnost tripsin inhibitora. Dobij eno sojino mleko je sadržalo BBI u tragovima, u formi BBI-polimera. BBI-monomerne forme nisu detektovane. Sojina mleka od ispitivanih genotipova soje imaju veoma slične sadržaj e KTI (2,34-2,99%). Rezultati su pokazali da genotip sojinog zrna nema značajne efekte na sadžaj KTI, kao i na vrednost rezidualne tripsin inhibitorske aktivnosti (rTIA). Ukupan sadržaj TI i vrednost rTIA je u snažnoj korelaciji (r= 0,91; p lt 0,05). HTC sojina mleka imala su vrednosti za rTIA lt 20% (7,15-19,89%). Ovi rezultati su pokazali da sojina mleka dobijena nakon HTC obrade mogu biti namenjena za ishranu ljudi

Serum proteini - osobine i mogućnost primjene

Whey protein fractions represents 18-20% of total milk nitrogen content. β-lactoglobulin is the major milk serum protein, while α-lactalbumin represents about 20% of total serum proteins or 2-5% of total milk nitrogen content. Whey proteins are highly susceptible to heat-induced denaturation; irreversibly denature and coagulate when exposed to high temperatures. Thermal treatment causes interaction between milk proteins, especially the interaction of α-lactalbumin, β-lactoglobulin and κ-casein. Complexes between them are known as coaggregates. Since the early 1980s, whey proteins have grown in popularity as nutritional and functional food ingredients. Serum proteins possess favorable functional characteristics such as gelling, water binding, emulsification and foaming ability. Due to the use of membrane fractionation techniques, it is possible to produce various whey-protein based products. The most important products based on the whey proteins are whey protein concentrate (WPC), whey protein isolate (WPI) and hydrolyzed whey protein (HWP). This review discusses the properties of major whey protein components and their possible use in dairy industry.Proteini mliječnog seruma predstavljaju 18-20% ukupnih dušikovih tvari mlijeka. Dominantni serum protein je β-laktoglobulin, dok je α-laktalbumin zastupljen s oko 20%, odnosno 2-5% od ukupnih dušikovih tvari mlijeka. Serum proteini su osjetljivi na djelovanje topline; ireverzibilno denaturiraju i koaguliraju pri djelovanju visokih temperatura. Djelovanje visokih temperatura uzrokuje kemijske interakcije među proteinima mlijeka, a posebno između α-laktalbumina, β-laktoglobulina i κ-kazeina. Kompleksi koji se ostvaruju među njima poznati su pod nazivom koagregati proteina mlijeka. Od osamdesetih godina prošlog stoljeća, serum proteini značajni su i kao nutritivni i kao funkcionalni aditivi. Serum proteini imaju dobre funkcionalne osobine. Mogu se koristiti kao sredstva za želiranje, za vezivanje vode, emulgiranje i obrazovanje pjene. Zahvaljujući primjeni membranskih tehnika frakcioniranja, danas je moguće proizvesti različite aditive na bazi serum proteina. Najvažniji proizvodi na bazi proteina sirutke su: proteinski koncentrati, izolati i hidrolizati proteina sirutke. U ovom su radu prikaz ane osobine dominantnih proteina sirutke i njihova moguća primjena u industriji mlijeka

THE EFFECT OF PARTIAL PROTEOLYSIS ON TECHNO - FUNCTIONAL AND ANTIOXIDANT PROPERTIES OF MODIFIED SOY PROTEIN ISOLATES

The partial enzymatic hydrolysis is effective and safe method which can be used to improve nutritive, techno-functional and functional properties of soy protein products. This method is affected by numerous factors. The objective of this work was to examine the effect of partial proteolysis on emulsifying and foaming properties of soy protein isolate. Also, the effect of proteolysis on ABTS-radical scavenging activity and iron (III) chelating ability was followed. Spray-dried soy protein isolate was prepared by isoelectric precipitation and modified using three different commercial proteases, Alcalase, Flavourzyme, and Papain. Initial isolate was hydrolyzed for 30, 60 and 90 minutes. Proteolysis was followed by the change of degree of hydrolysis (DH) and by native-PAGE, SDS-PAGE under reducing and non-reducing conditions. The effect of proteolysis on emulsifying properties was followed using emulsion stability index (ESI) and emulsion activity index (EAI). Also, foaming capacity and stability of foams formed using modified isolates were determined. Emulsifying and foaming properties was measured at pH 3, 5 and 7. Modified isolates were characterized with different DH values which were in the range of 11.75±0.08 (30 min, Papain) - 43.30±0.15 (Alcalase, 90 min). Limited proteolysis differently affected emulsifying properties of soy protein isolate. All modified isolates had improved emulsion stability at all investigated pH value whereas their ability to form emulsion was slightly lower or equal to initial isolate but in the range of commercial isolate used as standard. The highest stability had samples modified 30 min using Flavourzyme (366.94±48.85 min). Contrary, limited hydrolysis improved foaming capacity, but these foams were extremely unstable. The used enzymes differently affected the antioxidant properties of soy isolate. Only Alcalase improved radical scavenging activity of the initial isolate whereas the reducing power of all the investigated hydrolysates was lower than that of the initial isolate. Alcalase and Papain improved the ability of isolate to chelate iron (II) ions, whereas Flavourzyme-modified isolates had reduced iron (II) chelating ability. The initial IC50 of soy isolate was improved by 31.55-43.87% (Alcalase-modified) and by 21.08-60.40% (Papain-modified)

Bijeli sirevi u salamuri kao potencijalni izvor bioaktivnih peptida

In addition to the nutritional value, cheese and other fermented milk-based products are a good source of biologically active proteins and peptides. Bioactive peptides in cheese are mainly formed during cheese production, especially during ripening, which is one of the most important stages in cheese production. Since the ripening process differ significantly depending on the cheese type, it can be assumed that their bioactivity is also substantially different. White brined cheeses are specific for the region of South-Eastern Europe. They are characterized by relatively intensive proteolysis and as such may be of interest as products with favorable functional characteristics. Yet, their functionality is still insufficiently characterized. This paper presents an overview of the current knowledge on white brined cheese’s bioactive peptides.Sirevi kao i drugi fermentirani proizvodi na bazi mlijeka, osim izražene nutritivne vrijednosti, predstavljaju i dobar izvor biološki aktivnih proteina i peptida. Bioaktivni peptidi sira najvećim dijelom nastaju prilikom proizvodnje sira, a posebno tijekom zrenja, kao jedne od najznačajnijih faza u procesu proizvodnje. Kako se proces zrenja različitih tipova sira bitno razlikuje, može se pretpostaviti da se i njihova bioaktivnost bitno razlikuje. Bijeli sirevi u salamuri specifični su za podneblje Jugoistočne Europe, a odlikuju se dosta intenzivnim procesima proteolize te mogu biti zanimljivi kao proizvodi s povoljnim funkcionalnim karakteristikama. U tom smislu ovaj tip sira još uvijek nije dovoljno okarakteriziran. Ovaj rad predstavlja pregled dosadašnjih saznanja o bioaktivnim peptidima bijelih sireva u salamuri

Serum proteini mleka

Serum proteins present 18–20% of total milk nitrogen components. β-laktoglobulin (β-lg), α-laktalbumin (α-la), bovine serum albumin (BSA) and immunoglobulins (Ig) are the most important milk serum proteins. Also, milk serum contains low percent of other nitrogen components such as lactoferrin lactolin, glycoprotein, blood transferrin, proteose-peptone fraction (PP). β-lactoglobulin is the major milk serum protein. It is composed of 18300 Da molecular weight monomers. Molecule of β-lactoglobulin has two disulfide bonds, free –SH group at 121position. At pH near isoelectric point exists as a dimmer (M.W. about 36000). At pH 3.5–5.2 β-lactoglobulin expresses reversible tetramer-octamer association. These aggregates are based on hydrophobic interaction. At pH 3.7–6.5, these molecules aggregate as octamer. α-lactalbumin presents 20% of serum proteins or 2–5% of total milk nitrogen components. Molecular weight of α-lactalbumin is relatively small (14000). α-lactalbumin expresses high affinity to different ions especially to Ca- ions. The primary structure is characterized with 121 amino acid residues, high content of sulphur,, four disulphide bonds. There are no free –SH groups, phosphoric groups. The mechanism of serum protein precipitation depends on several factors: pH, temperature level ionic strength, dry matter, lactose content. These factors influence the degree of precipitation, weight of aggregates, the degree of major proteins denaturation as well as the nature of coagulum.U ukupnim azotnim materijama mleka, serum proteini učestvuju sa 18–20%. Najvažnije proteine mlečnog seruma čine β-laktoglobulin (β-lg) α-laktalbumin (α-la), goveđi serum albumin (BSA) i imunoglobulini (Ig). Pored ovih proteina, u mlečnom serumu prisutne su u malim količinama i druge azotne materije, kao što su laktoferin, laktolin, glikoprotein, krvni transferin, kao i proteozo-peptonska frakcija (PP). β-laktoglobulin je najviše zastupljen protein u mlečnom serumu, molekulske mase 18300 po monomeru. Molekul sadrži dva disulfidna mosta i jednu slobodnu sulfhidrilnu grupu na poziciji 121. Pri pH vrednosti blizu izoelektrične tačke β-laktoglobulin se nalazi u obliku dimera, čija je molekulska masa oko 36000. U pH intervalu 3.5–5.2, β-laktoglobulin reverzibilno obrazuje tetramer/oktamer asocijate, u kojima dominiraju hidrofobne interakcije. U pH intervalu 3.7–6.5, β-laktoglobulin obrazuje oktamere. α-laktalbumin čini 20% ukupnih serum proteina, ili 2–5% ukupnih azotnih materija mleka. Ima relativno malu molekulsku masu, 14000, i izražen afinitet prema različitim jonima, naročito prema kalcijumu. Primarnu strukturu karakteriše prisustvo 123 aminokiselinska ostatka, visok sadržaj sumpora, prisustvo četiri disulfidna mosta i odsustvo slobodnih tiolnih i fosfornih grupa. Mehanizam precipitacije serum proteina zavisi od više faktora: pH, visine temperature i dužine njenog delovanja, koncentracije dvovalentnih katjona, pre svega kalcijuma, jonske jačine sredine, sadržaja suve materije i sadržaja laktoze odnosno šećera. Ovi faktori utiču na obim precipitacije, veličinu obrazovanih agregata, stepen denaturacije između denaturisanih molekula α-laktalbumina i β-laktoglobulina, kao i na karakter obrazovanog koaguluma