Search

The focus of this work is to assess the quality of porous membranes prepared from naturally occurring kaolin clays and to evaluate the performance of tubular ceramic membranes treating integrated raw effluents from seafood industry. This material has been chosen due to its natural abundance, its non-toxicity, low cost and its valuable properties. The preparation and characterization of porous tubular ceramic membranes, using kaolin powder with and without corn starch as poreforming agent, were reported. SEM photographs indicated that the membrane surface was homogeneous. The effects of material compositions, additives and the relatively lower sintering temperature, ranging from 1100° to 1250°C, on porosity, average pore size, pore-size distribution and mechanical strength of membranes have been investigated. A correlation between microstructure and mechanical properties of membranes has been discussed. The performance of the novel ceramic membranes thus obtained was determined by evaluating both the water permeability and rejection. The obtained membrane was used to treat cuttlefish effluents generated from the conditioning seawater product industry which consumes a great amount of water. Cross-flow microfiltration was performed then, in order to reduce the turbidity and chemical oxygen demand (COD). [ABSTRACT FROM AUTHOR]

Introduction. Ultrafiltration (UF) is a single-unit operation for the clarification and fining of fruit juices. The purpose of the UF is to remove suspended solids as well as haze-inducing and turbidity-causing substances to obtain a clear juice during storage. Specifically, the polymerization of phenolic compounds and their interaction with other components (e.g., proteins) could cause a haze complex and turbidity in fruit juices, which can foul the ultrafiltration membrane. Materials and methods. Fresh pomegranate juice was clarified by the ultrafiltration process on a laboratory scale. In experimental tests performed according to the total recycle and the batch concentration mode, the effects of transmembrane pressure (TMP) and enzyme pre-treatment on permeation flux and quality of juice were studied. Results. With the total recycle mode, the effect of TMP on the color and clarity of clarified pomegranate juice was significant. The initial color of the raw pomegranate juice was reduced from 74% to 33% and the clarity decreased from 77% to 42% by UF when the TMP increased from (1 to 3.6) bar. Total phenolic rejection decreased from 45% to 21% when the TMP rose from (1 to 2) bar and remained constant above this value. With the batch concentration mode at TMP = 2 bar and velocity 1 m·s–1, the enzymatic treatment (5 U·mL–1, 300 min, T = 20 °C) of pomegranate juice provided the highest permeate flux, a decrease in total phenolics of 50% and an increased clarity of 30%. Fouling of the UF membrane during pomegranate juice processing is mainly due to the retention of polyphenols and/or proteins; thus, several blocking mechanisms were studied, using a recently developed membrane-fouling model. Analysis revealed that the membrane separation process was controlled by the gel layer mechanism of raw pomegranate juice and complete pore blocking mechanism with enzymatic pre-treatment. [ABSTRACT FROM PUBLISHER]

BSTRACT Phenolic compounds of pomegranate juice, which are responsible for haze formation and browning during storage, could be selectively removed by combined enzyme-ultrafiltration process. The pomegranate juice was treated with Fomes fomentarius laccase at various enzyme concentrations (0.5-5 U/mL), temperatures (20-50C) and times (30-300 min). The effect of these enzymatic treatments on total phenol content and clarity of the juice were evaluated using a central composite design. The optimum treatment conditions were: enzyme concentration 5 U/mL; time 300 min; and temperature 20C. Their application led to a 40% reduction of total phenols but induced a threefold decrease of the juice clarity. This drawback was overcome by ultrafiltration of the laccase-treated juice. The pomegranate juice obtained was clear, stable and characterized by total phenolics = 864 mg/L, clarity (A 650 nm × 1,000) = 86 and color (A 420 nm × 1,000) = 236 versus 1,681, 127 and 382, respectively, for untreated juice. PRACTICAL APPLICATIONS The tendency for hazes to develop in pomegranate juices during storage is a persistent problem in the fruit juice industry. In this work, laccase treatment optimized by response surface methodology followed by ultrafiltration was used to clarify the pomegranate juice. The application of the optimum enzymatic treatment conditions (enzyme concentration 5 U/mL; time 300 min; and temperature 20C) followed by ultrafiltration (cutoff value 15 KDa) decreases the total phenolics of about 50% and the antioxidant capacity of about 20% and, increases the clarity of about 30% versus untreated juice. [ABSTRACT FROM AUTHOR]

Lemon juice was treated with Penicillium occitanis pectinase at various enzyme concentrations (0-1200 U/L), temperatures (25-50 C) and times (0-90 min). The effect of these enzymatic treatments on the viscosity of the juice was evaluated. The optimum treatment conditions were: enzyme concentration 600 U/L, time 45 min and temperature 30176;C. Their application led to a 77% and 47% reduction of viscosity and turbidity, respectively. The enzymatic treatment was followed by ultrafiltration (cutoff value = 15 kDa). Analysis of the clarified juice indicated that enzyme depectinization permitted a higher permeate flux and a higher juice quality. The lemon juice obtained was clear, stable and characterized by viscosity = 0.7 mPas, turbidity = 0.17 NTU, clarity (A65onm) = 0.063 and color (A420nm) = 0.232. Microbiological study showed that lemon juice was free from aerobes, molds, enterobacteriaceae and coliforms and was microbiologically stable during 3 months storage. Results suggested that enzymatic treatment coupled to ultrafiltration could be used for production of lemon juice with high commercial value [ABSTRACT FROM AUTHOR]