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

Protein profiles and total antioxidant capacity of water soluble and insoluble protein fractions of white cow cheese at different stage of ripening

This research is focused on proteolysis and total antioxidant capacity of proteins of white brined cheese prepared from overheated (90 degrees C, 10 minutes) cow milk. White brined cow cheese of overheated milk went through specific proteolytic changes during ripening that were result of high level of whey proteins incorporated into the gel matrix. Specificity was reflected through the relatively low level of soluble nitrogen fractions, the intensive and continual decrease of alpha(s)-caseins up to 15.42 % of initial content, slow degradation of beta-casein throughout the whole ripening period and high level of proteolytic products tightly bounded into gel matrix. Strong negative correlations (-0.97, -0.98 and -0.91; p lt 0.05) between ripening time and resudual alpha(s)-caseins, beta-casein and low molecular weight products were observed. Proteolysis also affected the total antioxidant capacity of both water soluble and water insoluble nitrogen fractions, but to different extents and with different trends. Total antioxidant capacity of water insoluble fraction increased slowly during the whole ripening period, wherease significant improvement of total antioxidant capacity of water soluble fraction started after 30 days of ripening. These findings could be useful for better understanding and control of the white brined cow cheese production

Primarna proteoliza bijelog sira u salamuri proizvedenog od sirovog kravljeg mlijeka praćena visokomolarnim SDS-PAGE elektroforetskim sistemom

The aim of this work was to investigate primary proteolysis of white brined cow cheese prepared from raw milk by SDS-electrophoretic method based on high-molarity Tris buffer system and to correlate with the results of other commonly used parameters. Proteolytic changes of white brined cow cheese were monitored by three parameters: total protein, water soluble proteins and degree of proteolysis. Changes of major casein fractions were followed by SDS-electrophoretic system in reducing conditions. The total protein content and moisture content of white brined cow cheese were significantly affected by ripening. Ripening in brine increased water soluble proteins and degree of proteolysis. Major caseins were differently resistant to proteolysis; αs-CN was more susceptible than β-CN. The αs-CN content was highly and negatively correlated with time of ripening and water soluble proteins whereas no significant correlation (p<0.05) between β-CN content and these parameters was found. Also, a strong significant correlation (p<0.05) between the amount of low molecular weight products and time of ripening, water soluble proteins and αs-CN content was observed. SDS-PAGE method used in this study could be useful for monitoring the white cow cheese proteolysis.Cilj ovog rada bio je istražiti proces primarne proteolize bijelog sira u salamuri pripremljenog od sirovog kravljeg mlijeka metodom SDS-poliakrilamidne gel elektroforeze zasnovane na primjeni visoko molarnog sistema Tris pufera i korelirati s rezultatima uobičajeno korištenih parametara. Proteolitičke promjene bijelog sira u salamuri praćene su pomoću tri parametra: ukupnih proteina, proteina topljivih u vodi i stupnja proteolize. Promjena glavnih kazeinskih frakcija praćena je SDS-elektroforetskom metodom u reducirajućim uvjetima. Zrenje je značajno utjecalo na sadržaj ukupnih proteina i sadržaj vlage u kravljem bijelom siru. Ovaj proces povećao je sadržaj proteina topljivih u vodi i stupanj proteolize. Glavne kazeinske frakcije bile su različito otporne na proteolizu. αs-CN je bio mnogo osjetljiviji na djelovanje proteolitičkih enzima u odnosu na β-CN. Količina αs-CN u jakoj je negativnoj korelaciji sa trajanjem zrenja i proteinima topljivim u vodi, dok nije utvrđena značajna korelacija između sadržaja β-CN i ovih parametara. Također, značajna korelacija utvrđena je između količine produkata male molekulske mase i trajanja zrenja, sadržaja αs-CN i proteina topljivih u vodi. SDS-elektroforetska metoda korištena u ovim istraživanjima može biti korisna za praćenje proteolitičkih promjena tijekom zrenja kravljeg bijelog sira u salamuri

The Influence of Milk Type on the Proteolysis and Antioxidant Capacity of White-Brined Cheese Manufactured from High-Heat-Treated Milk Pretreated with Chymosin

We investigated the effect of milk type on the proteolysis and total antioxidant capacity (TEAC) of white-brined cheeses prepared from high-heat-treated (90 degrees C, 10 min) cow's and goat's milk, pretreated with chymosin at a low temperature (4 degrees C). The cheeses produced showed improved antioxidant characteristics and a high content of denatured whey proteins. However, these characteristics depend on the type of milk and the ripening time. Ripened cow's milk cheese had higher values of WSN/TN (water-soluble nitrogen per total nitrogen content) and TCA-SN/TN (nitrogen soluble in 12% trichloroacetic acid per total nitrogen), but similar PTA-SN/TN (nitrogen soluble in 5% phosphotungstic acid per total nitrogen) values were observed in ripened cheeses. The antioxidant potential of a WSF (water-soluble fraction) was higher in goat's milk cheese, but higher TEAC (total antioxidant capacity) values of WINF (water-insoluble fraction) were observed in matured cow's milk cheese. In vitro digestion slightly improved the radical scavenging capacity of WSF, whereas digested WINF had more than twice the capacity of their undigested counterparts. The cheeses prepared in this study could be a good source of antioxidant peptides. Further investigations of their in vitro and in vivo functionality need to be conducted

IN VITRO ANTIOXIDANT POTENTIAL OF SOYBEAN HULL EXTRACTS

Hull is the major by-product of soybean processing industry. Generally, it is regarded as „waste“ and used for animal feeding or discarded directly causing resource wastage and environmental pressure. However, soy hull can be a good source of bioactive compounds including isoflavones and other polyphenols, trypsin inhibitors and bioactive peptides. Most of these compounds are associated with antioxidant activity and it is believed that they can contribute to the reduction of oxidative stress, which is associated with the occurrence of a number of degenerative diseases. In this study we investigated in vitro antioxidant properties (ABTS radical scavenging activity, reducing power and iron (II) chelating ability), as well as total phenolic, flavonoid and dihydroxycinnamic acid derivates contents of water and methanol extracts of soybean hulls. For these purpose deffated commercial soy hulls were thermally pre-treated for 10 minutes using steam at 1.3 bars (wet heating) in oven at 120 ºC (dry heat treatment) during the same period. According to the results of this study both, thermal pre-treatment and extraction agent affect in vitro antioxidant potential, total content of phenolic and flavonoid compounds as well as the content of dihydroxycinnamic acid derivates. Water extracts had more than twice higher ABTS radical scavenging activity (4.57-4.91 mgETrolox/g) than the methanol extracts (2.03-2.16 mgETrolox/g), but similar Fe (II) chelating ability. Water extracts are characterized with higher content of total phenols, flavonoids and dihydroxycinnamic acid derivates compared to methanol extracts

Utjecaj zrenja u salamuri i pod vakuumom na udjele proteina, masnih kiselina i mineralnih tvari te antioksidacijski potencijal bijelog sira s manjim udjelom mliječne masti

Research background. Numerous factors affect the ripening of reduced-fat white cheese. The aim of this study is to investigate the influence of ripening environment (brine or vacuum plastic bags without brine) on the chemical composition, protein, fatty acid profile and mineral content as well as antioxidant properties of industrially produced reduced-fat white cheese. Experimental approach. A low-fat white cheese was manufactured on an industrial scale from milk that remained after the production of kajmak and ripened for 60 days at 4 °C after packaging in a polystyrene container with brine containing 6% salt or in vacuum-sealed polyethylene bags. The influence of ripening environment on proteolysis was monitored by the change of soluble nitrogen fractions as well as by sodium dodecyl sulphate–polyacrylamide gel electrophoresis of tris(hydroxymethyl) aminomethane-HCl extracts of cheese proteins under non-reducing conditions and water-soluble fractions under reducing conditions. An effect that ripening environment had on fatty acid and mineral content was also monitored. The change of antioxidant potential of the investigated cheese during ripening led to the change of iron(II) chelating ability, reducing power and free-radical scavenging activity. Results and conclusions. The ripening environment differently affected proteolysis, fatty acid composition, mineral profile and antioxidant properties of reduced-fat white cheese. White cheese ripened in brine had more intensive proteolytic changes than the cheese ripened in a vacuum, but also more intensive diffusion processes, especially between the 40th and 60th day of ripening. The brine-ripened cheese had higher values of water-soluble nitrogen content, but lower contents of trichloroacetic acid-soluble and phosphotungstic acid-soluble nitrogen than the vacuum-ripened cheese. Cheese ripened in brine had a lower content of almost all investigated macro- and microelements. After 60 days of ripening, in cheese ripened in brine only myristic (C14:0) and palmitic acid (C16:0) were detected, whereas in the vacuum-ripened cheese C10:0-C16:0 fatty acids dominated. Vacuum-ripened reduced-fat cheese had more favourable reducing power, while white brined reduced-fat cheese had better radical scavenging activity and iron(II) chelating activity. Novelty and scientific contribution. These results suggest significant influence of ripening conditions (immersion in brine or in vacuum-sealed polyethylene bags) on nutritive and functional properties of reduced-fat white cheese. Ripening in a vacuum has become a useful method for obtaining high-value reduced-fat white cheese.Pozadina istraživanja. Brojni faktori utječu na zrenje bijelog sira s manjim udjelom mliječne masti. Svrha je ovog istraživanja bila ispitati utjecaj uvjeta u kojima se odvija zrenje (u salamuri ili plastičnoj vakumiranoj vrećici bez salamure) na kemijski sastav, udjele proteina, masnih kiselina i mineralnih tvari te antioksidacijska svojstva industrijski proizvedenog bijelog sira s manjim udjelom mliječne masti. Eksperimentalni pristup. Bijeli sir s malim udjelom mliječne masti proizveden je u industrijskim mjerilima iz mlijeka preostalog nakon proizvodnje kajmaka, te je nakon pakiranja sazrijevao tijekom 60 dana na temperaturi od 4 °C u polistirenskim kutijama sa salamurom koja sadržava 6 % soli ili u vakumiranim polietilenskim vrećicama. Ispitan je utjecaj uvjeta zrenja na proteolizu, i to praćenjem promjene udjela topljivih dušikovih frakcija te SDS–poliakrilamid gel elektroforezom ekstrakata proteina sira dobivenih pomoću Tris(hidroksimetil)aminometana i HCl u nereducirajućim uvjetima te frakcija topljivih u vodi u reducirajućim uvjetima. Također je praćen utjecaj uvjeta zrenja na udjele masnih kiselina i mineralnih tvari. Promjena antioksidacijskog potencijala ispitanih uzoraka sira tijekom zrenja uzrokovala je promjenu svojstva keliranja Fe(II) iona, redukcijske snage i sposobnosti hvatanja slobodnih radikala. Rezultati i zaključci. Uvjeti u kojima je sazrijevao bijeli sir s manjim udjelom mliječne masti različito su utjecali na proteolizu, udjele masnih kiselina i mineralnih tvari te antioksidativna svojstva sira. U bijelom siru koji je sazrijevao u salamuri zamijećene su intenzivnije proteolitičke promjene, te su u njemu difuzijski procesi bili intenzivniji od onih u siru koji je sazrijevao pod vakuumom, naročito između četrdesetog i šezdesetog dana zrenja. Sir koji je sazrijevao u salamuri imao je veći udjel dušikovih spojeva topljivih u vodi, ali manji udjel dušikovih spojeva topljivih u trikloroctenoj i fosfovolframovoj kiselini. Sir koji je sazrijevao u salamuri imao je manji udjel skoro svih ispitanih makro- i mikroelemenata. Nakon 60 dana zrenja, u siru koji je sazrijevao u salamuri pronađene su samo miristinska (C14:0) i palmitinska kiselina (C16:0), dok su u siru koji je sazrijevao u vakuumu prevladavale C10:0-C16:0 masne kiseline. Sir s manjim udjelom mliječne masti koji je sazrijevao pod vakuumom imao je bolje reducirajuće svojstvo, dok je sir koji je sazrijevao u salamuri imao veću sposobnost hvatanja slobodnih radikala i veću moć keliranja Fe(II) iona. Novina i znanstveni doprinos. Ovi rezultati pokazuju bitan utjecaj uvjeta zrenja (u salamuri ili pod vakuumom) na hranjiva i funkcionalna svojstva bijelih sireva s manjim udjelom mliječne masti. Zrenje pod vakuumom se sve više smatra korisnom metodom dobivanja visokovrijednih bijelih sireva s manjim udjelom mliječne masti

Primarna proteoliza kozjeg bijelog sira u salamuri praćena SDS-PAGE sistemom visokog molariteta

The aim of this work was to investigate primary proteolysis of white brined goat cheese prepared from raw milk and to correlate with the results obtained with high-molarity Tris buffer electrophoretic system. Proteolytic changes of white brined cheese were monitored by three parameters, the total protein, the water soluble proteins and the degree of proteolysis, whereas the change of major casein fractions was followed by electrophoresis in reducing conditions. Ripening caused a decrease of the total protein content, whereas in the first forty days the water soluble protein and the degree of proteolysis increased. Both casein fractions (αs- and β-casein) of goat cheese were susceptible to primary proteolysis but to the different extent. αs1- casein disappeared during processing, whereas during 60-days of ripening the content of αs2 and β-casein was reduced by 38.90 %, and 30.72 %, respectively. Such trends of major casein fractions were strongly correlated with the degree of proteolysis and the moisture content, whereas no correlation was found between them and the water soluble protein content. The results of our investigation clearly suggested that SDS-PAGE method based on high-molarity Tris-buffer system could be a very useful for purposes of monitoring the white goat cheese proteolysis.Cilj ovog rada bio je ispitati proces primarne proteolize bijelog sira u salamuri pripremljenog od sirovog kozjeg mlijeka i staviti u korelaciju s rezultatima dobivenim SDS-elektroforetskom metodom koja se bazira na primjeni Tris pufernog sistema visokog molariteta. Proteolitičke promjene bijelog sira u salamuri praćene su pomoću tri parametra: ukupnih proteina, u vodi topljivih proteina i stupnja proteolize, dok je promjena glavnih kazeinskih frakcija praćena elektroforezom u reducirajućim uvjetima. Zrenje sira uzrokuje pad sadržaja ukupnih proteina, dok sadržaj u vodi topljivih proteina i stupanj proteolize raste tijekom 40 dana zrenja. Obje kazeinske frakcije (αs- i β-kazein) podliježu procesu proteolize, ali u različitom stupnju. αs1-kazein se razgrađuje tijekom pripreme sira, dok se tijekom zrenja sira sadržaji αs2- i β-kazeina reduciraju za 38.90 % i 30.72 %. Ovakva promjena glavnih kazeinskih frakcija u jakoj je korelaciji sa stupnjem proteolize, sadržajem ukupnih proteina i sadržajem vlage, dok nije uočena korelacija između ovih parametara i u vodi topljivih proteina. Rezultati naših istraživanja jasno pokazuju da SDSelektroforetski sistem zasnovan na visoko molarnim Tris- puferima može biti vrlo korisna metoda za praćenje proteolitičkih promjena tijekom zrenja kozjeg bijelog sira u salamuri

Primary proteolysis of white brined cheese prepared from raw cow milk monitored by high-molarity Tris buffer SDS-PAGE system

The aim of this work was to investigate primary proteolysis of white brined cow cheese prepared from raw milk by SDS-electrophoretic method based on high-molarity Tris buffer system and to correlate with the results of other commonly used parameters. Proteolytic changes of white brined cow cheese were monitored by three parameters: total protein, water soluble proteins and degree of proteolysis. Changes of major casein fractions were followed by SDS-electrophoretic system in reducing conditions. The total protein content and moisture content of white brined cow cheese were significantly affected by ripening. Ripening in brine increased water soluble proteins and degree of proteolysis. Major caseins were differently resistant to proteolysis; alpha(s)-CN was more susceptible than beta-CN. The alpha(s)-CN content was highly and negatively correlated with time of ripening and water soluble proteins whereas no significant correlation (p lt 0.05) between beta-CN content and these parameters was found. Also, a strong significant correlation (p lt 0.05) between the amount of low molecular weight products and time of ripening, water soluble proteins and alpha(s)-CN content was observed. SDS-PAGE method used in this study could be useful for monitoring the white cow cheese proteolysis

NOVI PRILAZ ODREĐIVANJU MINIMALNE ZAPREMINE REZERVOARA ZA KOMPRIMOVANI VAZDUH

U radu je, na osnovu relacije za maksimalan rad kod zatvorenih termodinamičkih sistema, izvedenopšti model za određivanje minimalne zapremine rezervoara za komprimovani vazduh. S obzirom,da u posmatranom sistemu postoji mehanička i termodinamička neravnoteža, ispunjeni su uslovi zadobijanje maksimalnog rada. Dobijena relacija, koja predstalja novi model, može se direktnokoristiti u tehničkoj praksi za slučaj da su poznati parametri koji definišu početno stanje urezervoaru, parametri okoline, kao i energija koju je potrebno dobiti od komprimovanog vazduha.Radi potpunijeg predstavljanja posmatranog procesa, isti je predstavljen u radnom p-v i toplotnomT-s dijagramu. Pored analitičkog, u radu je predstvljeno i grafičko rešenje postavljenog problema,koje može poslužiti i za kontrolu dobijenih rezultata. Takođe, ilustrovana je primena izvedenogmodela na praktičnom primeru, gdje je određena minimalna zapremina sfernog rezervoara u kojemse nalazi vazduh

Primary proteolysis of white brined goat cheese monitored by high molarity Tris buffer SDS- PAGE system

The aim of this work was to investigate primary proteolysis of white brined goat cheese prepared from raw milk and to correlate with the results obtained with high-molarity Tris buffer electrophoretic system. Proteolytic changes of white brined cheese were monitored by three parameters, the total protein, the water soluble proteins and the degree of proteolysis, whereas the change of major casein fractions was followed by electrophoresis in reducing conditions. Ripening caused a decrease of the total protein content, whereas in the first forty days the water soluble protein and the degree of proteolysis increased. Both casein fractions (alpha(s)- and beta-casein) of goat cheese were susceptible to primary proteolysis but to the different extent. alpha(s1)-casein disappeared during processing, whereas during 60-days of ripening the content of alpha(s2) and beta-casein was reduced by 38.90 %, and 30.72 %, respectively. Such trends of major casein fractions were strongly correlated with the degree of proteolysis and the moisture content, whereas no correlation was found between them and the water soluble protein content. The results of our investigation clearly suggested that SDS-PAGE method based on high-molarity Tris-buffer system could be a very useful for purposes of monitoring the white goat cheese proteolysis