TY  - JOUR
AU  - Urošević, Tijana
AU  - Povrenović, Dragan
AU  - Vukosavljević, Predrag
AU  - Urošević, Ivan
PY  - 2018
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/4727
AB  - In this paper, the influence of operating parameters (transmembrane pressure, temperature, the flow rate of retentate) on the cross - flow microfiltration of synthetic fruit juice and periodic backwashing with air was examined. In the experiments, the Kerasep W5 ceramic membrane with a separation limit of 0.2 mu m was used. The results of experiments in which different transmembrane pressures were used showed that stationary fluxes, at stationary conditions, after 60 minutes, have similar values. So, it can be concluded that the value of the driving force is irrelevant at steady state conditions. However, until the steady state conditions are established, a positive effect of the increase in the driving force is opposed to the negative effect of the increased polarization resistance, as a result of the driving force increase. Thus, the optimal transmembrane pressure was determined amounting to 2 bars. The optimum temperature of the process of clearing the fruit juices by microfiltration is reported as 55 degrees C. Higher temperatures are not used due to a degrading effect on the chemical composition of the juice and a long microfiltration process. With an increase in the temperature of retentate from 22 degrees C to 55 degrees C, the permeate flux increased up to 60 %. Increasing the flow rate of retentate reduces the thickness of the formed layer on the surface of the membrane. Due to limitations of the experimental setup and the large surface area of the membrane, the specific velocity of the retentate was low, so that the effects of cross-flow filtration were absent. The use of cross-flow filtration is one of the main requirements for increasing permeate flux, but in the present case it was in overall insufficient, so we have applied periodic air backwashing for improving fruit juice flux during membrane clarification. With this technique, the deposited layer on the membrane is lifted and the permeate flux is maintained at high levels preventing establishment of the steady state in the low flux zone. The time spent for the periodic backwashing was low as compared to the benefits of the increase in the collected permeate quantity. In all experiments with periodic backwashing with air, the collected permeate quantity is higher for up to 72.5 % as compared to experiments without backwashing. By increasing the backwashing duration, the flux increase is up to 5 %, which can be significant for microfiltration at industrial scale. Therefore, this technique is certainly recommended for microfiltration in the production of fruit juices.
PB  - Savez hemijskih inženjera, Beograd
T2  - HEMIJSKA INDUSTRIJA
T1  - Microfiltration with periodic gas backwashing as an alternative technique for increasing permeate flux
EP  - 68
IS  - 2
SP  - 59
VL  - 72
DO  - 10.2298/HEMIND170814021U
ER  - 

@article{
author = "Urošević, Tijana and Povrenović, Dragan and Vukosavljević, Predrag and Urošević, Ivan",
year = "2018",
abstract = "In this paper, the influence of operating parameters (transmembrane pressure, temperature, the flow rate of retentate) on the cross - flow microfiltration of synthetic fruit juice and periodic backwashing with air was examined. In the experiments, the Kerasep W5 ceramic membrane with a separation limit of 0.2 mu m was used. The results of experiments in which different transmembrane pressures were used showed that stationary fluxes, at stationary conditions, after 60 minutes, have similar values. So, it can be concluded that the value of the driving force is irrelevant at steady state conditions. However, until the steady state conditions are established, a positive effect of the increase in the driving force is opposed to the negative effect of the increased polarization resistance, as a result of the driving force increase. Thus, the optimal transmembrane pressure was determined amounting to 2 bars. The optimum temperature of the process of clearing the fruit juices by microfiltration is reported as 55 degrees C. Higher temperatures are not used due to a degrading effect on the chemical composition of the juice and a long microfiltration process. With an increase in the temperature of retentate from 22 degrees C to 55 degrees C, the permeate flux increased up to 60 %. Increasing the flow rate of retentate reduces the thickness of the formed layer on the surface of the membrane. Due to limitations of the experimental setup and the large surface area of the membrane, the specific velocity of the retentate was low, so that the effects of cross-flow filtration were absent. The use of cross-flow filtration is one of the main requirements for increasing permeate flux, but in the present case it was in overall insufficient, so we have applied periodic air backwashing for improving fruit juice flux during membrane clarification. With this technique, the deposited layer on the membrane is lifted and the permeate flux is maintained at high levels preventing establishment of the steady state in the low flux zone. The time spent for the periodic backwashing was low as compared to the benefits of the increase in the collected permeate quantity. In all experiments with periodic backwashing with air, the collected permeate quantity is higher for up to 72.5 % as compared to experiments without backwashing. By increasing the backwashing duration, the flux increase is up to 5 %, which can be significant for microfiltration at industrial scale. Therefore, this technique is certainly recommended for microfiltration in the production of fruit juices.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "HEMIJSKA INDUSTRIJA",
title = "Microfiltration with periodic gas backwashing as an alternative technique for increasing permeate flux",
pages = "68-59",
number = "2",
volume = "72",
doi = "10.2298/HEMIND170814021U"
}

Urošević, T., Povrenović, D., Vukosavljević, P.,& Urošević, I.. (2018). Microfiltration with periodic gas backwashing as an alternative technique for increasing permeate flux. in HEMIJSKA INDUSTRIJA
Savez hemijskih inženjera, Beograd., 72(2), 59-68.
https://doi.org/10.2298/HEMIND170814021U

Urošević T, Povrenović D, Vukosavljević P, Urošević I. Microfiltration with periodic gas backwashing as an alternative technique for increasing permeate flux. in HEMIJSKA INDUSTRIJA. 2018;72(2):59-68.
doi:10.2298/HEMIND170814021U .

Urošević, Tijana, Povrenović, Dragan, Vukosavljević, Predrag, Urošević, Ivan, "Microfiltration with periodic gas backwashing as an alternative technique for increasing permeate flux" in HEMIJSKA INDUSTRIJA, 72, no. 2 (2018):59-68,
https://doi.org/10.2298/HEMIND170814021U . .

TY  - JOUR
AU  - Urošević, Tijana
AU  - Povrenović, Dragan
AU  - Vukosavljević, Predrag
AU  - Urošević, Ivan
AU  - Stevanović, Snežana
PY  - 2017
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/4413
AB  - This article provides an overview of recent developments and the published literature in microfiltration (MF) and ultrafiltration (UF) of fruit juices. In this review, we summarize studies by relating basic concepts of membrane filtration with reported results and outlining the important factors to consider in the practical use of MF and UF. The important factors influencing the filtration rate and product quality are type of feed solution (type of fruit juice), membrane selection and operating parameters (temperature, transmembrane pressure, cross-flow velocity and volume concentration ratio). According to physicochemical and sensory tests confirmed by many types of research, juices produced by membrane filtration are of an excellent quality. Membrane fouling is a critical issue and inhibits the wider application of membranes in the fruit juice industry. The use of cross-flow filtration is one of the main requirements for increasing permeate flux, but overall insufficient, so we considered various techniques (enzymatic pretreatment, mechanical and electrical techniques) for improving fruit juice flux during membrane clarification.
PB  - Elsevier, Amsterdam
T2  - Food and Bioproducts Processing
T1  - Recent developments in microfiltration and ultrafiltration of fruit juices
EP  - 161
SP  - 147
VL  - 106
DO  - 10.1016/j.fbp.2017.09.009
ER  - 

@article{
author = "Urošević, Tijana and Povrenović, Dragan and Vukosavljević, Predrag and Urošević, Ivan and Stevanović, Snežana",
year = "2017",
abstract = "This article provides an overview of recent developments and the published literature in microfiltration (MF) and ultrafiltration (UF) of fruit juices. In this review, we summarize studies by relating basic concepts of membrane filtration with reported results and outlining the important factors to consider in the practical use of MF and UF. The important factors influencing the filtration rate and product quality are type of feed solution (type of fruit juice), membrane selection and operating parameters (temperature, transmembrane pressure, cross-flow velocity and volume concentration ratio). According to physicochemical and sensory tests confirmed by many types of research, juices produced by membrane filtration are of an excellent quality. Membrane fouling is a critical issue and inhibits the wider application of membranes in the fruit juice industry. The use of cross-flow filtration is one of the main requirements for increasing permeate flux, but overall insufficient, so we considered various techniques (enzymatic pretreatment, mechanical and electrical techniques) for improving fruit juice flux during membrane clarification.",
publisher = "Elsevier, Amsterdam",
journal = "Food and Bioproducts Processing",
title = "Recent developments in microfiltration and ultrafiltration of fruit juices",
pages = "161-147",
volume = "106",
doi = "10.1016/j.fbp.2017.09.009"
}

Urošević, T., Povrenović, D., Vukosavljević, P., Urošević, I.,& Stevanović, S.. (2017). Recent developments in microfiltration and ultrafiltration of fruit juices. in Food and Bioproducts Processing
Elsevier, Amsterdam., 106, 147-161.
https://doi.org/10.1016/j.fbp.2017.09.009

Urošević T, Povrenović D, Vukosavljević P, Urošević I, Stevanović S. Recent developments in microfiltration and ultrafiltration of fruit juices. in Food and Bioproducts Processing. 2017;106:147-161.
doi:10.1016/j.fbp.2017.09.009 .

Urošević, Tijana, Povrenović, Dragan, Vukosavljević, Predrag, Urošević, Ivan, Stevanović, Snežana, "Recent developments in microfiltration and ultrafiltration of fruit juices" in Food and Bioproducts Processing, 106 (2017):147-161,
https://doi.org/10.1016/j.fbp.2017.09.009 . .

TY  - JOUR
AU  - Živković, Milovan
AU  - Rakić, Sveto
AU  - Maletić, Radojka
AU  - Povrenović, Dragan
AU  - Nikolić, Miloš
AU  - Kosanović, Nada
PY  - 2011
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/2570
AB  - In this study, drying kinetics of autochthonous variety Požegača plum was examined in a laboratory dryer at three temperatures. The whole plum fruits, together with the kernels were subjected to the drying process. The effect of drying has been examined at temperatures of 55, 60 and 75°C, with a constant air velocity of 1.1 m s-1. The corresponding experimental results were tested using six nonlinear regression models. Coefficient of determination (R2), standard regression error (SSE), model correlation coeficient (Vy), as well as the maximum absolute error (ΔY) showed that the logaritmic model was in good agreement with the experimental data obtained. During drying of plums, the effective diffusivity was found to be between 5.6×10-9 for 55°C and 8.9×10-9 m2 s-1 at 75°C, respectively. The physical characteristics of fresh (length 39.64 mm and width 29.15 mm) and dried (length 37.52 mm and width 22.85 mm) plum fruit were determined. Finally, by chemical analysis, the contents of micro- and macro-elements (Fe, Mn, Cu, B and N, F, K, Ca, Mg and S) in the skin and flesh of the dried product, prunes, has been established.
AB  - Predmet ispitivanja ove studije je kinetika sušenja šljive autohtone sorte Požegača u laboratorijskoj sušari na tri temperaturna režima. Tretirani su celi plodovi šljiva, zajedno sa košticom. Ispitivan je efekat sušenja pri različitim temperaturama 55; 60 i 75°C, praćenjem promene vlažnosti materijala u funkciji vremena sušenja pri stalnoj brzini vazduha od 1,1 m s-1. Eksperimentalni rezultati ovih ispitivanja sušenja testirani su na šest nelinearnih regresionih modela. Koeficijent determinacije (R2), standardna greška regresije (SSE), koeficijent varijacije modela (Vy), kao i maksimalna apsolutna greška ocenjenog modela (ΔY), su pokazali da je Logarithmic model najbolje prilagođen eksperimentalnim podacima. Tokom sušenja plodova šljiva, utvrđen je koeficient difuzije čija se vrednost kretala između 5,6×10-9 za 55°C i 8,9×10-9 m2 s-1 za 75°C, respektivno. Određene su fizičke karakteristike svežih (dužina 39,64 mm i širine 29,15 mm) i sušenih (dužina 37,52 mm i širine 22,85 mm) plodova šljive. Hemijskom analizom određen je sadržaj mikro-i makroelemenata (Fe, Mn, Cu, B i N, C, K, Ca, Mg i S) u koži i mesu kod sušenih plodova šljive.
PB  - Savez hemijskih inženjera, Beograd
T2  - Chemical Industry and Chemical Engineering Quarterly / CICEQ
T1  - Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety
T1  - Uticaj temperature na fizičke promene i kinetiku sušenja šljive (Prunus domestica L.) sorte požegača
EP  - 289
IS  - 3
SP  - 283
VL  - 17
DO  - 10.2298/CICEQ101109013Z
ER  - 

@article{
author = "Živković, Milovan and Rakić, Sveto and Maletić, Radojka and Povrenović, Dragan and Nikolić, Miloš and Kosanović, Nada",
year = "2011",
abstract = "In this study, drying kinetics of autochthonous variety Požegača plum was examined in a laboratory dryer at three temperatures. The whole plum fruits, together with the kernels were subjected to the drying process. The effect of drying has been examined at temperatures of 55, 60 and 75°C, with a constant air velocity of 1.1 m s-1. The corresponding experimental results were tested using six nonlinear regression models. Coefficient of determination (R2), standard regression error (SSE), model correlation coeficient (Vy), as well as the maximum absolute error (ΔY) showed that the logaritmic model was in good agreement with the experimental data obtained. During drying of plums, the effective diffusivity was found to be between 5.6×10-9 for 55°C and 8.9×10-9 m2 s-1 at 75°C, respectively. The physical characteristics of fresh (length 39.64 mm and width 29.15 mm) and dried (length 37.52 mm and width 22.85 mm) plum fruit were determined. Finally, by chemical analysis, the contents of micro- and macro-elements (Fe, Mn, Cu, B and N, F, K, Ca, Mg and S) in the skin and flesh of the dried product, prunes, has been established., Predmet ispitivanja ove studije je kinetika sušenja šljive autohtone sorte Požegača u laboratorijskoj sušari na tri temperaturna režima. Tretirani su celi plodovi šljiva, zajedno sa košticom. Ispitivan je efekat sušenja pri različitim temperaturama 55; 60 i 75°C, praćenjem promene vlažnosti materijala u funkciji vremena sušenja pri stalnoj brzini vazduha od 1,1 m s-1. Eksperimentalni rezultati ovih ispitivanja sušenja testirani su na šest nelinearnih regresionih modela. Koeficijent determinacije (R2), standardna greška regresije (SSE), koeficijent varijacije modela (Vy), kao i maksimalna apsolutna greška ocenjenog modela (ΔY), su pokazali da je Logarithmic model najbolje prilagođen eksperimentalnim podacima. Tokom sušenja plodova šljiva, utvrđen je koeficient difuzije čija se vrednost kretala između 5,6×10-9 za 55°C i 8,9×10-9 m2 s-1 za 75°C, respektivno. Određene su fizičke karakteristike svežih (dužina 39,64 mm i širine 29,15 mm) i sušenih (dužina 37,52 mm i širine 22,85 mm) plodova šljive. Hemijskom analizom određen je sadržaj mikro-i makroelemenata (Fe, Mn, Cu, B i N, C, K, Ca, Mg i S) u koži i mesu kod sušenih plodova šljive.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Chemical Industry and Chemical Engineering Quarterly / CICEQ",
title = "Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety, Uticaj temperature na fizičke promene i kinetiku sušenja šljive (Prunus domestica L.) sorte požegača",
pages = "289-283",
number = "3",
volume = "17",
doi = "10.2298/CICEQ101109013Z"
}

Živković, M., Rakić, S., Maletić, R., Povrenović, D., Nikolić, M.,& Kosanović, N.. (2011). Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety. in Chemical Industry and Chemical Engineering Quarterly / CICEQ
Savez hemijskih inženjera, Beograd., 17(3), 283-289.
https://doi.org/10.2298/CICEQ101109013Z

Živković M, Rakić S, Maletić R, Povrenović D, Nikolić M, Kosanović N. Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety. in Chemical Industry and Chemical Engineering Quarterly / CICEQ. 2011;17(3):283-289.
doi:10.2298/CICEQ101109013Z .

Živković, Milovan, Rakić, Sveto, Maletić, Radojka, Povrenović, Dragan, Nikolić, Miloš, Kosanović, Nada, "Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety" in Chemical Industry and Chemical Engineering Quarterly / CICEQ, 17, no. 3 (2011):283-289,
https://doi.org/10.2298/CICEQ101109013Z . .

TY  - JOUR
AU  - Povrenović, Dragan
AU  - Nedović, Viktor
PY  - 2010
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/2219
AB  - Brewery yeast cells immobilized in Ca-alginate were dried in a laboratory scale spouted bed with a draft tube. The experiment was conducted under variable temperatures and air flow rates. The temperature and air velocity at the bottom of the column have been varied in the range from 30 to 60 °C and from 6 to 10 m/s in a duration of 60 min. The moisture of dried particles was in the interval of 10.00 to 21.00 g/g, while the water activity was in the range of 0.40 to 0.45 what ensures the preservation of immobilized yeast as a starter and provides the biological activity of dried particles. A rehidration process of dried particles proved that dried particles could completely restore their original shape and starting volume, while the mechanical resistance is somewhat reduced. The cells preserved in this way completely restore their catalytical activity after the rehidration.
AB  - Imobilisane ćelije pivskog kvasca u Ca-alginatu su sušene u laboratorijskoj sušnici sa konicnoim fontanskim slojem. Eksperiment je izvođen pri različitim temperaturama i protocima ulaznog vazduha. Temperatura je menjana u intervalu od 30 do 60 °C, a brzina vazduha na ulazu u kolonu je menjana od 6 do 10 m/s, pri konstantnom vremenu sušenja u svim eksperimentima u trajanju od 60 min. Početna vlažnost čestica koje su sušene, kretala se u intervalu od 10,00 do 21,00 g vlage/g suve materije, dok je aktivnost vode bila u opsegu od 0,40 do 0,45, koja obezbeđuje korišćenje osušenih čestica kao starter kultura, uz istovremeno sprečavanje bioloških procesa u osušenim imobilisanim česticama. Nakon rehidratacije, osušene čestice su vraćale svoju prvobitnu zapreminu i oblik, dok je njihova mehanička otpornost smanjena u odnosu na čestice pre sušenja. Ćelije, sačuvane na ovaj način su, nakon rehidratacije, zadržavale svoju katalitičku aktivnost. Dobijeni rezultati u ovom radu su polazni parametri za projektovanje pilot sušionika.
PB  - Savez hemijskih inženjera, Beograd
T2  - Chemical Industry and Chemical Engineering Quarterly / CICEQ
T1  - Drying of immobilized yeast cells in a spouted bed dryer with a moving draft tube
T1  - Sušenje imobilisanih ćelija pivskog kvasca u sušioniku sa fontanskim slojem i pokretnom centralnom cevi
EP  - 137
IS  - 2
SP  - 133
VL  - 16
DO  - 10.2298/CICEQ100123021P
ER  - 

@article{
author = "Povrenović, Dragan and Nedović, Viktor",
year = "2010",
abstract = "Brewery yeast cells immobilized in Ca-alginate were dried in a laboratory scale spouted bed with a draft tube. The experiment was conducted under variable temperatures and air flow rates. The temperature and air velocity at the bottom of the column have been varied in the range from 30 to 60 °C and from 6 to 10 m/s in a duration of 60 min. The moisture of dried particles was in the interval of 10.00 to 21.00 g/g, while the water activity was in the range of 0.40 to 0.45 what ensures the preservation of immobilized yeast as a starter and provides the biological activity of dried particles. A rehidration process of dried particles proved that dried particles could completely restore their original shape and starting volume, while the mechanical resistance is somewhat reduced. The cells preserved in this way completely restore their catalytical activity after the rehidration., Imobilisane ćelije pivskog kvasca u Ca-alginatu su sušene u laboratorijskoj sušnici sa konicnoim fontanskim slojem. Eksperiment je izvođen pri različitim temperaturama i protocima ulaznog vazduha. Temperatura je menjana u intervalu od 30 do 60 °C, a brzina vazduha na ulazu u kolonu je menjana od 6 do 10 m/s, pri konstantnom vremenu sušenja u svim eksperimentima u trajanju od 60 min. Početna vlažnost čestica koje su sušene, kretala se u intervalu od 10,00 do 21,00 g vlage/g suve materije, dok je aktivnost vode bila u opsegu od 0,40 do 0,45, koja obezbeđuje korišćenje osušenih čestica kao starter kultura, uz istovremeno sprečavanje bioloških procesa u osušenim imobilisanim česticama. Nakon rehidratacije, osušene čestice su vraćale svoju prvobitnu zapreminu i oblik, dok je njihova mehanička otpornost smanjena u odnosu na čestice pre sušenja. Ćelije, sačuvane na ovaj način su, nakon rehidratacije, zadržavale svoju katalitičku aktivnost. Dobijeni rezultati u ovom radu su polazni parametri za projektovanje pilot sušionika.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Chemical Industry and Chemical Engineering Quarterly / CICEQ",
title = "Drying of immobilized yeast cells in a spouted bed dryer with a moving draft tube, Sušenje imobilisanih ćelija pivskog kvasca u sušioniku sa fontanskim slojem i pokretnom centralnom cevi",
pages = "137-133",
number = "2",
volume = "16",
doi = "10.2298/CICEQ100123021P"
}

Povrenović, D.,& Nedović, V.. (2010). Drying of immobilized yeast cells in a spouted bed dryer with a moving draft tube. in Chemical Industry and Chemical Engineering Quarterly / CICEQ
Savez hemijskih inženjera, Beograd., 16(2), 133-137.
https://doi.org/10.2298/CICEQ100123021P

Povrenović D, Nedović V. Drying of immobilized yeast cells in a spouted bed dryer with a moving draft tube. in Chemical Industry and Chemical Engineering Quarterly / CICEQ. 2010;16(2):133-137.
doi:10.2298/CICEQ100123021P .

Povrenović, Dragan, Nedović, Viktor, "Drying of immobilized yeast cells in a spouted bed dryer with a moving draft tube" in Chemical Industry and Chemical Engineering Quarterly / CICEQ, 16, no. 2 (2010):133-137,
https://doi.org/10.2298/CICEQ100123021P . .

TY  - JOUR
AU  - Rakić, Sveto
AU  - Petrović, Silvana
AU  - Kukić, Jelena
AU  - Jadranin, Milka
AU  - Tešević, Vele
AU  - Povrenović, Dragan
AU  - Siler-Marinković, Slavica
PY  - 2007
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/1493
AB  - The aim of the present work was to investigate and compare phenolic compounds and antioxidant activity of methanol extracts of Quercus robur and Quercus cerris acorn kernels obtained before and after thermal treatment. Content of total phenolics, tannins, non-tannin phenolics and flavonoids was determined spectrophotometrically and content of gallic acid with HPLC. Antioxidant activity of the samples was assayed through FRAP (Ferric Reducing Antioxidant Power), DPPH scavenging test and inhibition of Fe2+/ascorbate induced lipid peroxidation. Extracts of native and thermally treated kernels showed high antioxidant activity, with extracts of thermally treated kernels being more active than extracts of native ones. Hydrolysable tannins and gallic acid were identified in all samples. Non-tannin phenolics, including gallic acid, were present in significantly higher quantities in thermally treated samples, whilst tannin content decreased. This indicates that during thermal treatment hydrolysable tannins were degraded. As the result of this degradation and consequent increase of non-tannin phenolics content, and amongst them especially gallic acid, thermally treated samples possess higher antioxidant activity than do the native ones. The obtained results have provided further grounds for establishing Q. robur and Q. cerris acorn kernels as a source for functional food preparation,
PB  - Elsevier Sci Ltd, Oxford
T2  - Food Chemistry
T1  - Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia
EP  - 834
IS  - 2
SP  - 830
VL  - 104
DO  - 10.1016/j.foodchem.2007.01.025
ER  - 

@article{
author = "Rakić, Sveto and Petrović, Silvana and Kukić, Jelena and Jadranin, Milka and Tešević, Vele and Povrenović, Dragan and Siler-Marinković, Slavica",
year = "2007",
abstract = "The aim of the present work was to investigate and compare phenolic compounds and antioxidant activity of methanol extracts of Quercus robur and Quercus cerris acorn kernels obtained before and after thermal treatment. Content of total phenolics, tannins, non-tannin phenolics and flavonoids was determined spectrophotometrically and content of gallic acid with HPLC. Antioxidant activity of the samples was assayed through FRAP (Ferric Reducing Antioxidant Power), DPPH scavenging test and inhibition of Fe2+/ascorbate induced lipid peroxidation. Extracts of native and thermally treated kernels showed high antioxidant activity, with extracts of thermally treated kernels being more active than extracts of native ones. Hydrolysable tannins and gallic acid were identified in all samples. Non-tannin phenolics, including gallic acid, were present in significantly higher quantities in thermally treated samples, whilst tannin content decreased. This indicates that during thermal treatment hydrolysable tannins were degraded. As the result of this degradation and consequent increase of non-tannin phenolics content, and amongst them especially gallic acid, thermally treated samples possess higher antioxidant activity than do the native ones. The obtained results have provided further grounds for establishing Q. robur and Q. cerris acorn kernels as a source for functional food preparation,",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Food Chemistry",
title = "Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia",
pages = "834-830",
number = "2",
volume = "104",
doi = "10.1016/j.foodchem.2007.01.025"
}

Rakić, S., Petrović, S., Kukić, J., Jadranin, M., Tešević, V., Povrenović, D.,& Siler-Marinković, S.. (2007). Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia. in Food Chemistry
Elsevier Sci Ltd, Oxford., 104(2), 830-834.
https://doi.org/10.1016/j.foodchem.2007.01.025

Rakić S, Petrović S, Kukić J, Jadranin M, Tešević V, Povrenović D, Siler-Marinković S. Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia. in Food Chemistry. 2007;104(2):830-834.
doi:10.1016/j.foodchem.2007.01.025 .

Rakić, Sveto, Petrović, Silvana, Kukić, Jelena, Jadranin, Milka, Tešević, Vele, Povrenović, Dragan, Siler-Marinković, Slavica, "Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia" in Food Chemistry, 104, no. 2 (2007):830-834,
https://doi.org/10.1016/j.foodchem.2007.01.025 . .

TY  - JOUR
AU  - Rakić, Sveto
AU  - Povrenović, Dragan
AU  - Tešević, Vele
AU  - Simić, M
AU  - Maletić, Radojka
PY  - 2006
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/1329
AB  - In this paper, are presented the results of physical and chemical investigations of differently treated samples of oak acorn. The aim of this investigation is to estimate the influence of thermal treatment on physical and nutritive characteristics of investigated samples. Oak acorn, Quercus robur, (belonging to Fagaceae family) was investigated in native and thermally treated forms. By subsequent extraction of dry toasted oak acorn (Quercus semen tostum) the aqueous extract was obtained which is then dried in a spout-fluid bed. The content of total polyphenols, then polyphenols unadsorbed on hide powder and tannins was determined by spectrophotometric methods with phosphor-wolfram acid according to Ph. Yug. V. Galic acid was determined by HPLC. The total antioxidant activity (TAA) of the aqueous extract compared to the control samples of pigs fat and synthetic antioxidant butylated hydroxyanisole BHA was estimated by Schall-Oven test at 60 +/- 1 degrees C in dark, and oxidative changes were determined by measuring the Peroxide value (PV). For determination of macro- and microelements the method of AAS was used. By detecting the changes of PV it is established that aqueous extract was influencing the stability of pigs fat, that is, showing the antioxidant activity. The activity was increasing with increasing concentration in tested samples. The obtained results regarding the total polyphenols content, the content of galic acid, nitrogen compounds, macro and microelements show that acorn, after treatment, was retaining and in some cases improving its functional properties.
PB  - Elsevier Sci Ltd, Oxford
T2  - Journal of Food Engineering
T1  - Oak acorn, polyphenols and antioxidant activity in functional food
EP  - 423
IS  - 3
SP  - 416
VL  - 74
DO  - 10.1016/j.jfoodeng.2005.03.057
ER  - 

@article{
author = "Rakić, Sveto and Povrenović, Dragan and Tešević, Vele and Simić, M and Maletić, Radojka",
year = "2006",
abstract = "In this paper, are presented the results of physical and chemical investigations of differently treated samples of oak acorn. The aim of this investigation is to estimate the influence of thermal treatment on physical and nutritive characteristics of investigated samples. Oak acorn, Quercus robur, (belonging to Fagaceae family) was investigated in native and thermally treated forms. By subsequent extraction of dry toasted oak acorn (Quercus semen tostum) the aqueous extract was obtained which is then dried in a spout-fluid bed. The content of total polyphenols, then polyphenols unadsorbed on hide powder and tannins was determined by spectrophotometric methods with phosphor-wolfram acid according to Ph. Yug. V. Galic acid was determined by HPLC. The total antioxidant activity (TAA) of the aqueous extract compared to the control samples of pigs fat and synthetic antioxidant butylated hydroxyanisole BHA was estimated by Schall-Oven test at 60 +/- 1 degrees C in dark, and oxidative changes were determined by measuring the Peroxide value (PV). For determination of macro- and microelements the method of AAS was used. By detecting the changes of PV it is established that aqueous extract was influencing the stability of pigs fat, that is, showing the antioxidant activity. The activity was increasing with increasing concentration in tested samples. The obtained results regarding the total polyphenols content, the content of galic acid, nitrogen compounds, macro and microelements show that acorn, after treatment, was retaining and in some cases improving its functional properties.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Journal of Food Engineering",
title = "Oak acorn, polyphenols and antioxidant activity in functional food",
pages = "423-416",
number = "3",
volume = "74",
doi = "10.1016/j.jfoodeng.2005.03.057"
}

Rakić, S., Povrenović, D., Tešević, V., Simić, M.,& Maletić, R.. (2006). Oak acorn, polyphenols and antioxidant activity in functional food. in Journal of Food Engineering
Elsevier Sci Ltd, Oxford., 74(3), 416-423.
https://doi.org/10.1016/j.jfoodeng.2005.03.057

Rakić S, Povrenović D, Tešević V, Simić M, Maletić R. Oak acorn, polyphenols and antioxidant activity in functional food. in Journal of Food Engineering. 2006;74(3):416-423.
doi:10.1016/j.jfoodeng.2005.03.057 .

Rakić, Sveto, Povrenović, Dragan, Tešević, Vele, Simić, M, Maletić, Radojka, "Oak acorn, polyphenols and antioxidant activity in functional food" in Journal of Food Engineering, 74, no. 3 (2006):416-423,
https://doi.org/10.1016/j.jfoodeng.2005.03.057 . .

TY  - JOUR
AU  - Rakić, Sveto
AU  - Povrenović, Dragan
AU  - Maletić, Radojka
AU  - Živković, Milovan
PY  - 2005
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/919
AB  - The results of the chemical investigations of variously treated acorn samples are presented in this paper with the aim of obtaining data on the amount of nutritious components and biologically active substances. The Quercus robur acorn, which belongs to the Fagaceae family, was investigated in a raw, thermally treated form and as an extract that was subsequently dried in a dryer with a fluidized bed. The obtained results regarding the content of tannin, nitrogen containing compounds, macro- and microelements indicate that acorn maintains its functional characteristics after the investigated treatments.
AB  - U ovom radu su predstavljeni rezultati hemijskih ispitivanja različito tretiranih uzoraka hrastovog žira, u cilju dobijanja podataka o količini hranljivih komponenti i supstanci sa biološki aktivnim dejstvom. Ispitivan je žir Quercus robur, koji pripada familiji Fagaceae, u sirovom, termički tretiranom obliku i ekstraktu koji je naknadno sušen u sušioniku sa fontansko-fluidizovanim slojem. Dobijeni rezultati u pogledu sadržaja, tanina, azotnih jedinjenja, makro i mikroelemenata pokazuju da hrastov žir, nakon ispitivanih tretmana, zadržava svoje funkcionalne karakteristike. Hemijski sastav nativnog hrastovog žira kao i proizvodi dobijeni opisanim postupcima u ovom radu, ukazuje na prihvatljivost ove sirovine sa aspekta njegove primene u ljudskoj ishrani. Hrastov žir Quercus robur se odlikuje raznovrsnošću hranljivih, energetskihe i funkcionalno-zaštitnih materija. Postupkom termičkog i hidrotermičkog tretmana kao i postupkom sušenja vodenog ekstrakta postižu se značajni rezultati u pogledu koncentrisanja materija koje imaju funkcionalna svojstva. Povećanje sadržaja je evidentno kod proteina, ukupnih mineralnih materija, makroelemenata (fosfor i kalijum), kao i mikroelemenata (gvožđe i bakar) s tim što se u u budućim istraživanjima mora definisati razlog pada koncentracije gvožđa pri sušenju tečnog ekstrakta. Hrastov žir je sirovina koja nije komercijalizovana, a kao jeftin i lako dostupan biljni materijal, predstavlja potencijalni izvor biološki aktivnih komponenti, čija je primena moguća u prehrambenoj , farmaceutskoj i drugim industrijama.
PB  - Univerzitet u Beogradu - Poljoprivredni fakultet, Beograd
T2  - Journal of Agricultural Sciences (Belgrade)
T1  - Drying of the aqueous extract of acorn Quercus robur in a spout-fluid bed
T1  - Sušenje vodenog ekstrakta hrastovog žira Quercus robur u sušioniku sa fontansko-fluidizovanim slojem
EP  - 182
IS  - 2
SP  - 173
VL  - 50
DO  - 10.2298/JAS0502173R
ER  - 

@article{
author = "Rakić, Sveto and Povrenović, Dragan and Maletić, Radojka and Živković, Milovan",
year = "2005",
abstract = "The results of the chemical investigations of variously treated acorn samples are presented in this paper with the aim of obtaining data on the amount of nutritious components and biologically active substances. The Quercus robur acorn, which belongs to the Fagaceae family, was investigated in a raw, thermally treated form and as an extract that was subsequently dried in a dryer with a fluidized bed. The obtained results regarding the content of tannin, nitrogen containing compounds, macro- and microelements indicate that acorn maintains its functional characteristics after the investigated treatments., U ovom radu su predstavljeni rezultati hemijskih ispitivanja različito tretiranih uzoraka hrastovog žira, u cilju dobijanja podataka o količini hranljivih komponenti i supstanci sa biološki aktivnim dejstvom. Ispitivan je žir Quercus robur, koji pripada familiji Fagaceae, u sirovom, termički tretiranom obliku i ekstraktu koji je naknadno sušen u sušioniku sa fontansko-fluidizovanim slojem. Dobijeni rezultati u pogledu sadržaja, tanina, azotnih jedinjenja, makro i mikroelemenata pokazuju da hrastov žir, nakon ispitivanih tretmana, zadržava svoje funkcionalne karakteristike. Hemijski sastav nativnog hrastovog žira kao i proizvodi dobijeni opisanim postupcima u ovom radu, ukazuje na prihvatljivost ove sirovine sa aspekta njegove primene u ljudskoj ishrani. Hrastov žir Quercus robur se odlikuje raznovrsnošću hranljivih, energetskihe i funkcionalno-zaštitnih materija. Postupkom termičkog i hidrotermičkog tretmana kao i postupkom sušenja vodenog ekstrakta postižu se značajni rezultati u pogledu koncentrisanja materija koje imaju funkcionalna svojstva. Povećanje sadržaja je evidentno kod proteina, ukupnih mineralnih materija, makroelemenata (fosfor i kalijum), kao i mikroelemenata (gvožđe i bakar) s tim što se u u budućim istraživanjima mora definisati razlog pada koncentracije gvožđa pri sušenju tečnog ekstrakta. Hrastov žir je sirovina koja nije komercijalizovana, a kao jeftin i lako dostupan biljni materijal, predstavlja potencijalni izvor biološki aktivnih komponenti, čija je primena moguća u prehrambenoj , farmaceutskoj i drugim industrijama.",
publisher = "Univerzitet u Beogradu - Poljoprivredni fakultet, Beograd",
journal = "Journal of Agricultural Sciences (Belgrade)",
title = "Drying of the aqueous extract of acorn Quercus robur in a spout-fluid bed, Sušenje vodenog ekstrakta hrastovog žira Quercus robur u sušioniku sa fontansko-fluidizovanim slojem",
pages = "182-173",
number = "2",
volume = "50",
doi = "10.2298/JAS0502173R"
}

Rakić, S., Povrenović, D., Maletić, R.,& Živković, M.. (2005). Drying of the aqueous extract of acorn Quercus robur in a spout-fluid bed. in Journal of Agricultural Sciences (Belgrade)
Univerzitet u Beogradu - Poljoprivredni fakultet, Beograd., 50(2), 173-182.
https://doi.org/10.2298/JAS0502173R

Rakić S, Povrenović D, Maletić R, Živković M. Drying of the aqueous extract of acorn Quercus robur in a spout-fluid bed. in Journal of Agricultural Sciences (Belgrade). 2005;50(2):173-182.
doi:10.2298/JAS0502173R .

Rakić, Sveto, Povrenović, Dragan, Maletić, Radojka, Živković, Milovan, "Drying of the aqueous extract of acorn Quercus robur in a spout-fluid bed" in Journal of Agricultural Sciences (Belgrade), 50, no. 2 (2005):173-182,
https://doi.org/10.2298/JAS0502173R . .

TY  - JOUR
AU  - Laketić, Daniela A.
AU  - Povrenović, Dragan
AU  - Nedović, Viktor
AU  - Kokolj, Maja
AU  - Leskošek-Čukalović, Ida
PY  - 2002
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/471
AB  - The paper presents the results of testing of immobilized brewers yeast cells kilning in fluidized bed, under various temperature and air flow conditions. Yeast immobilization was carried out by method of cell retention inside the matrix of Ca-alginate support. Kilning was done by compressor air, at the temperatures t=30, 40, 50 and 60° С and at air flow rate of 3.14 m/s, during 90 minutes. Humidity of the kilned particles was within the interval of 0.1-0.2 kg/ kg, while water activity was within the range of 0.28 (t=60° C) to 0.45 (t=30° C). This level of water activity in the kilned samples prevented any biological activity and secured conservation of im- mobilized starters. Testing of the kilned particles rehydration process showed that the kilned particles can completely recover their original form and initial volume, but they expressed somewhat reduced mechanical resistance. Maximum percentage of humidity recovery was measured 24 hours after rehydration and it amounted to 92% of humidity before kilning, while particle volume increased up to four times in relation to the volume of the kilned sample. The particles conserved by the procedure of kilning after rehydration, recovered catalytic activity.
AB  - U radu su prikazani rezultati ispitivanja procesa sušenja imobilisanih ćelija pivskog kvasca u fluidizovanom sloju pri različitim režimima temperature i protoka vazduha. Imobilizacija kvasca je izvršena metodom zadržavanja delija unutar matrice nosača Ca-alginata. Sušenje je vršeno kompresorskim vaz- duhom, pri temperaturama t=30, 40, 50 i 60°C i brzini vazduha od 3.14 m/s, u trajanju od 90 minuta. Vlažnost osušenih čestica se kretala u intervalu od 0,1-0,2 kg/kg, dok se aktivnost vode nalazila u opsegu od 0.28 (t=60 °C) do 0.45 (t=30°C). Ovaj nivo aktivnosti vode u osušenim uzorcima onemogućava bilo kakvu biološku aktivnost i obezbeđuje konzervisanje imobilisanih startera. Ispitivanjem procesa rehidratacije osušenih čestica, utvrđeno je da osušene čestice mogu u potpunosti da povrate svoj prvobitni oblik i početnu zapreminu, ali ispoljavaju donekle smanjenu mehaničku otpornost. Maksimalno dostignut procenat povraćaju vlage je meren nakon 24 časa rehidratacije i iznosio je 92% vlažnosti pre sušenja, dok se zapremina čestica povećala i do 4 puta u odnosu na vrednosti osušenog uzorka. Čestice konzervisane ovim postupkom sušenja posle rehidratacije su povratile katalitičku aktivnost.
PB  - Poslovno udruženje industrije piva, Beograd
T2  - Pivarstvo
T1  - Kilning of immobilized brewers yeast cells in ca-alginate particles in fluidized bed
T1  - Sušenje imobilisanih ćelija pivskog kvasca u česticama ca-alginata u fluidizovanom sloju
EP  - 55
IS  - 1-2
SP  - 52
VL  - 35
UR  - https://hdl.handle.net/21.15107/rcub_agrospace_471
ER  - 

@article{
author = "Laketić, Daniela A. and Povrenović, Dragan and Nedović, Viktor and Kokolj, Maja and Leskošek-Čukalović, Ida",
year = "2002",
abstract = "The paper presents the results of testing of immobilized brewers yeast cells kilning in fluidized bed, under various temperature and air flow conditions. Yeast immobilization was carried out by method of cell retention inside the matrix of Ca-alginate support. Kilning was done by compressor air, at the temperatures t=30, 40, 50 and 60° С and at air flow rate of 3.14 m/s, during 90 minutes. Humidity of the kilned particles was within the interval of 0.1-0.2 kg/ kg, while water activity was within the range of 0.28 (t=60° C) to 0.45 (t=30° C). This level of water activity in the kilned samples prevented any biological activity and secured conservation of im- mobilized starters. Testing of the kilned particles rehydration process showed that the kilned particles can completely recover their original form and initial volume, but they expressed somewhat reduced mechanical resistance. Maximum percentage of humidity recovery was measured 24 hours after rehydration and it amounted to 92% of humidity before kilning, while particle volume increased up to four times in relation to the volume of the kilned sample. The particles conserved by the procedure of kilning after rehydration, recovered catalytic activity., U radu su prikazani rezultati ispitivanja procesa sušenja imobilisanih ćelija pivskog kvasca u fluidizovanom sloju pri različitim režimima temperature i protoka vazduha. Imobilizacija kvasca je izvršena metodom zadržavanja delija unutar matrice nosača Ca-alginata. Sušenje je vršeno kompresorskim vaz- duhom, pri temperaturama t=30, 40, 50 i 60°C i brzini vazduha od 3.14 m/s, u trajanju od 90 minuta. Vlažnost osušenih čestica se kretala u intervalu od 0,1-0,2 kg/kg, dok se aktivnost vode nalazila u opsegu od 0.28 (t=60 °C) do 0.45 (t=30°C). Ovaj nivo aktivnosti vode u osušenim uzorcima onemogućava bilo kakvu biološku aktivnost i obezbeđuje konzervisanje imobilisanih startera. Ispitivanjem procesa rehidratacije osušenih čestica, utvrđeno je da osušene čestice mogu u potpunosti da povrate svoj prvobitni oblik i početnu zapreminu, ali ispoljavaju donekle smanjenu mehaničku otpornost. Maksimalno dostignut procenat povraćaju vlage je meren nakon 24 časa rehidratacije i iznosio je 92% vlažnosti pre sušenja, dok se zapremina čestica povećala i do 4 puta u odnosu na vrednosti osušenog uzorka. Čestice konzervisane ovim postupkom sušenja posle rehidratacije su povratile katalitičku aktivnost.",
publisher = "Poslovno udruženje industrije piva, Beograd",
journal = "Pivarstvo",
title = "Kilning of immobilized brewers yeast cells in ca-alginate particles in fluidized bed, Sušenje imobilisanih ćelija pivskog kvasca u česticama ca-alginata u fluidizovanom sloju",
pages = "55-52",
number = "1-2",
volume = "35",
url = "https://hdl.handle.net/21.15107/rcub_agrospace_471"
}

Laketić, D. A., Povrenović, D., Nedović, V., Kokolj, M.,& Leskošek-Čukalović, I.. (2002). Kilning of immobilized brewers yeast cells in ca-alginate particles in fluidized bed. in Pivarstvo
Poslovno udruženje industrije piva, Beograd., 35(1-2), 52-55.
https://hdl.handle.net/21.15107/rcub_agrospace_471

Laketić DA, Povrenović D, Nedović V, Kokolj M, Leskošek-Čukalović I. Kilning of immobilized brewers yeast cells in ca-alginate particles in fluidized bed. in Pivarstvo. 2002;35(1-2):52-55.
https://hdl.handle.net/21.15107/rcub_agrospace_471 .

Laketić, Daniela A., Povrenović, Dragan, Nedović, Viktor, Kokolj, Maja, Leskošek-Čukalović, Ida, "Kilning of immobilized brewers yeast cells in ca-alginate particles in fluidized bed" in Pivarstvo, 35, no. 1-2 (2002):52-55,
https://hdl.handle.net/21.15107/rcub_agrospace_471 .