Predrag Vukosavljević

Permeate flux and fouling resistance in ultrafiltration of depectinized apple juice using ceramic membranes

Raw depectinized apple juice was clarified in a laboratory scale ultrafiltration system using ceramic tubular membranes (Tech-Sep Carbosep) with a molecular weight cut-off of 300,000, 50,000, and 30,000 Da. The experiments have been carried out over a wide range of transmembrane pressures (100–400 kPa), temperatures (20–55 °C), and feed flow rates (100–900 ml/min). Permeate flux significantly decreased with time until a steady-state was established. The steady-state permeate flux reached a maximum at a transmembrane pressure of about 200 kPa. Higher permeate flux was obtained at higher temperatures due to lower permeate viscosity. The steady-state permeate flux was proportional to the feed flow rate raised to powers ranging between 0.22 and 0.31. All the membranes studied produced the clarified juice with a satisfactory clarity and color intensity value.

Physicochemical, Antioxidant and Sensory Properties of Peach Wine Made from Redhaven Cultivar

Physicochemical, sensory, and health-related characteristics of peach wine produced from Redhaven variety and selected white wines produced from various grape varieties were determined and compared. The alcohol content, titratable acidity, and total extract of peach wine was significantly lower compared with that of white wines, while its pH value was higher. The content of total phenolics (TPC) and flavonoids (TFC) of peach wine (402.53 mg/L GAE and 332.67 mg CAE/L, respectively) have been found significantly higher in comparison with that of white wines (TPC range 243.67-319.00 mg/L GAE, TFC range 129.67-175.17 mg CAE/L). The main phenolic compounds found in peach wine were chlorogenic acid, caffeic acid, and catechin (3.59, 0.87, and 0.60 mg/L, respectively). Antioxidant capacities were strongly correlated with total phenolics with correlation coefficients over 0.99. The highest antioxidant capacity was ascribed to peach wine. The results of sensory analysis indicated that the peach wine was very well accepted by the regular consumers of wine and can be a very interesting product in the market.

ANTIOXIDANT ACTIVITIES OF HERBS, FRUIT AND MEDICINAL MUSHROOM Ganoderma lucidum EXTRACTS PRODUCED BY MICROFILTRATION PROCESS

This paper presents kinds of extraction and cross-flow filtration of composition of 46 healthful and aromatic herbs, 8 fruits and fungi Ganoderma lucidum. Those extracts are part of Bitter 55, which have significant antioxidant capacity. Antioxidative activities of plant extracts have been determined by DPPH test using method of Blois. Bitter 55 which was kept at the green bottle in the dark has EC50 = 141.07 μl/ml and it was stable during 150 days. Synthetic anti-oxidants BHT (ditertbutilhydroxytoluen, EC50 = 6.2 μgml-1), trolox (vitamin E analog soluble in water, EC50 = 6.8 μgml-1) were used for comparison. EC50 values were calculated as concentration of the extract necessary to decrease DPPH radical concentration for 50 %. Bitter 55 contents 35% vol of alcohol (wheat origin), 88.22 g/l total extract and slice of medicinal mushroom Ganoderma lucidum (1 % w/v) which was extracted 30 days before analyses. The main problem in practical applications of MF is the reduction of permeate flux with time, caused by the accumulation of feed components in the pores. During microfiltration bitter herbal liquor, the function of filtrate flux is decreased with VCR. Dependence of decreasing flux with VCR can be separated in three periods. For the first, starting period, rapid decrease of filtrate flux is characteristic. Second period is defined with much smaller decrease of the flux than in the first phase. Third period has as characteristic minor decrease of flux and can be defined as steady state. Steady state emerges after τs = 80 min.

Mikrofiltracija sa periodičnim povratnim ispiranjem kao alternativna tehnika za povećanje fluksa permeata

U ovom radu je ispitan uticaj radnih parametara (transmembranski prtisak, temperatura, brzina strujanja retentata) na unakrsnu ( cross – flow ) mikrofiltraciju model rastvora vocnog soka i periodicno povratno ispiranje vazduhom. U eksperimentima je koriscena keramicka Kerasep W5 membrana sa granicom separacije od 0,2 µm. Određen je optimalni transmembranski pritisak, koji iznosi 2 bara. Optimalna temperatura procesa bistrenja vocnih sokova mikrofiltracijom je 55°C. Vise temperature se ne koriste zbog degradativnog efekta na hemijski sastav soka i dugog procesa mikrofiltracije. Sa porastom temperature retentata od 22°C do 55°C ostvaruje se porast fluksa permeata do 60 %. Povecanjem brzine strujanja retentata smanjuje se debljina formiranog sloja na povrsini membrane. Zbog ogranicenja koriscene aparature i velike povrsine membrane, postignute specificne brzine strujanja retentata su male, pa efekat unakrsne filtracije izostaje. Periodicnim povratnim ispiranjem se nataloženi sloj na membrani podiže, fluks permeata je u visokoj zoni i sprecava se uspostavljanje stacionarnog stanja u zoni niskih flukseva. Vreme utroseno na povratno ispiranje je malo u odnosu na povecanje sakupljene mase permeata. U svim eksperimentima sa povratnim ispiranjem sakupljena masa permeata je veca do 72,5 % u odnosu na eksperimente bez povratnog ispiranja. Povecanjem vremena trajanja povratnog ispiranja povecanje fluksa je do 5 %, sto može biti znacajno za mikrofiltraciju u industrijskim uslovima.