Chicory juice clarification by membrane filtration using rotating disk module

Clarification is the first step of inulin production from chicory juice, and membrane filtration as an alternative can greatly simplify this process, increase juice yield, improve product quality, and reduce the cost and waste volume. In this study, a rotating disk module (RDM) was used to investigate the clarification of chicory juice by four micro- and ultrafiltration membranes. Compared with dead end filtration, the RDM had a much higher permeate flux and product quality. High rotating speeds produced high permeate fluxes and reduced flux decline, because of the strong back transport of foulant from fouling layer to feed solution. At high rotating speeds of 1500–2000 rpm, the permeate flux increased with membrane pore size and transmembrane pressure (TMP), while at low rotating speeds (<1000 rpm), permeate flux was independent of membrane type and TMP due to a thick deposited fouling layer as a dominant filtration resistance, while carbohydrate transmission decreased at higher TMP because of denser cake layer as an additional selective membrane. The highest carbohydrate transmission (∼98%) and desirable permeate turbidity (2.4 NTU) was obtained at a TMP of 75 kPa and a rotating speed of 2000 rpm for FSM0.45PP membrane. With the RDM, the Volume Reduction Ratio (VRR) could reach 10 with a high permeate flux (106 L m⁻² h⁻¹) in the concentration test, and permeate was still rich in carbohydrate and well clarified. Chemical cleaning with 0.5% P3-ultrasil 10 detergent solution was able to recover 90% water flux of fouled membrane.     

Clarification of apple juice by electroflotation

Apple Juice industry is in search of a simplified technology which enables a quick clarification and stabilisation of apple juice. This study aimed to evaluate the potential of electroflotation as an alternative for the clarification of apple juice. Clarification of apple juice by electroflotation was first done at various current densities (10, 20 and 40 mA/cm²) with and without addition of gelatin (200 mg/l). Afterwards, the electroflotation treatments were done at a current density of 20 mA/cm² with various concentrations of added gelatin (0, 50, 100 and 200 mg/l). It was shown that electroflotation treatments alone was efficient to reduce the tannin and protein contents of apple juice. However, the decrease in the protein content was in large part due to the use of pectinases prior to the electroflotation treatments. The use of gelatin in combination with the electroflotation aided in the clarification process. The highest gelatin concentration used in this study (200 mg/l) resulted in a better reduction of tannin and protein levels, while a current density of 20 mA/cm² was found to be optimal. Turbidity observed in the juices clarified with electroflotation treatments was in average lower than 10 NTU but higher than 2 NTU which is generally required to produce a stable clarified juice. Brix degree and pH of the apple juice was not affected by the electroflotation treatments while the color was improved.

Industrial relevance

The production of clarified and stable apple juice is a subject of interest for the beverages industries. The clarification step which remained long and discontinuous implied the addition of a large quantity of pectolytic enzyme and of clarifying agents (such as gelatin) to the freshly pressed juice to induce the precipitation of proteins and other suspended matter in 15–20 h. Fining treatments were followed by a separation step usually consisting of decantation and classical filtration on filter-press, or flotation by dispersed gas. The development of membrane separation processes to replace the traditional approach has enabled the automation of the whole production resulting in lower labor requirement and a considerably shorter process time than the traditional process.However, the performance of membrane separation processes is influenced by the declining permeate flux with time, which is due to membrane fouling. In some instances, permeate flux decline makes membrane separation processes unattractive for the clarification of apple juice. To our knowledge, we are the first research group to use electroflotation (EF) for clarification of apple juice. It was shown that EF treatments alone were efficient to reduce the tannin and protein contents of apple juice. In addition, the use of gelatin in combination with the EF aided in the clarification process. Turbidity observed in the juices clarified with EF treatments for 30 min was in average lower than 10 NTU. Brix degree and pH of the apple juice were not affected by the EF treatments while the color was improved.When compared to the values reported in the literature for flotation by dispersed gas, it seems that EF shows better efficiency than flotation in decreasing the juice turbidity (99% decrease for EF as compared to 90% decrease for flotation). In addition, for experiments carried out by conventional flotation larger amount of fining agent are used (70–150 mg of gelatin/l, 400–800 mg/l of silica sol and 200–500 mg/l of bentonite). For these reasons, the new process we propose is advantageous when compared to the traditional flotation approach and it should have a measurable impact on the advancements in the production of clarified apple juice. If used as a pre-treatment to ultrafiltration clarification, it is expected that it would reduce membrane fouling resulting in higher productivity.     

The effect of ultrasound waves on the efficiency of membrane clarification of pomegranate juice

Pomegranate juice has a turbid appearance, which poses difficulties in its concentration process. Membrane clarification can be used to clarify pomegranate juice; however, membrane fouling reduces the permeate flux, limiting its effectiveness. Ultrasound at 30 kHz was used to reduce membrane fouling. Results were compared with the data obtained for membrane clarification without ultrasonic treatment at the same temperature. Results showed that permeate flux increased with ultrasonic treatment. Evaluation of different membrane fouling characteristics showed that the total membrane resistance fell due to the reduction in irreversible fouling and cake resistance. However, ultrasound did not affect the thick caking produced in membrane processing at low feed‐flow rates. Evaluation of the physicochemical properties of pomegranate juice showed that ultrasound can decrease antioxidant activity due to the reduction in total anthocyanin content. Also, total soluble solid content and acidity of pomegranate juice changed with ultrasonic treatment.     

Effect of membrane property and operating conditions on phytochemical properties and permeate flux during clarification of pineapple juice

The effects of membrane property on the permeate flux, membrane fouling and quality of clarified pineapple juice were studied. Both microfiltration (membrane pore size of 0.1 and 0.2 μm) and ultrafiltration (membrane molecular weight cut-off (MWCO) of 30 and 100 kDa) membranes were employed. Membrane filtration did not have significant effects on the pH, reducing sugar and acidity of clarified juice whereas the suspended solids and microorganism were completely removed. The 0.2 μm membrane gave the highest permeate flux, total vitamin C content, total phenolic content and antioxidant capacity as well as the highest value of irreversible fouling. Based on these results, the membrane with pore size of 0.2 μm was considered to be the most suitable membrane for the clarification of pineapple juice. The optimum operating conditions for the clarification pineapple juice by membrane filtration was a cross-flow velocity of 3.4 ms⁻¹ and transmembrane pressure (TMP) of 0.7 bar. An average flux of about 37 lm⁻² h⁻¹ was obtained during the microfiltration of pineapple juice under the optimum conditions using batch concentration mode.     

Clarification and sterilization of raw depectinized apple juice by ceramic ultrafiltration membranes

Raw depectinized apple juice was clarified and sterilized in a cross‐flow pilot scale ultrafiltration system using ceramic tubular membranes (MEMBRALOX^®, Pall) with mean pore size of 100 nm. The permeate flux significantly decreased with time until a steady‐state was established. An increase in filtration pressure increased the permeate flux while there is an optimum pressure (about 0.85 bar) above which the increase of pressure does not increase the flux significantly. The higher the cross‐flow velocity was, the higher was the transmembrane flux. When the operating temperature increased, the permeation rate increased subsequently. Analytical measurement showed that suspended solids and turbidity could almost be removed by the ceramic ultrafiltration membrane, but pH, acidity, sugar and soluble solid content of the juices showed no significant change. The bacteria challenge tests with Micrococcus flavus showed that the logarithm value of the bacteria reduction rate came up to above 9 in the cross‐flow tubular ceramic system. When the permeate was collected in sterile bottles in a laminar flow shell and kept at 4 °C, 8 °C, 25 °C and 35 °C, for 28 days, the apple juice experienced minimal changes in physicochemical properties at lower temperatures of 4 °C, or 8 °C. Copyright © 2005 Society of Chemical Industry     

Analysis of the fouling mechanisms during cross-flow ultrafiltration of apple juice

The purpose of this work was to study the fouling mechanisms of a Carbosep^® M8 membrane during the cross-flow ultrafiltration of apple juice. A new fouling model has been developed that simultaneously considers membrane blocking within the pores, at the pore mouths and by cake formation at the membrane surface. Membrane fouling by apple juice was due to internal pore blocking as well as cake formation. When operating ultrafiltration at a transmembrane pressure of 150 kPa and a cross-flow velocity of 7 m/s, fouling was minimal with a gradual decrease of the relative contribution of cake formation; however, transmembrane pressure still exceeds critical pressure. The fouling model predicts no cake formation at a cross-flow velocity of 7.4 m/s and a transmembrane pressure of 150 kPa or at a cross-flow velocity of 7.0 m/s and a transmembrane pressure of 120 kPa. Under these conditions, internal membrane blocking would be the only mechanism responsible for the decrease of permeate flux.     

Clarification of tomato juice by cross‐flow microfiltration

Clarification of fruit and vegetable juice is one of the integrated parts of modern industrial juice processing. This paper describes the clarification of tomato juice through microfiltration process. In this regard, the influence of transmembrane pressure (1, 2 and 3 bar), cross‐flow velocity which corresponds with Reynolds number (300, 1500 and 2500) and temperature (30, 40 and 50 °C) on permeate flux and some properties of clarified juice such as colour, turbidity, density, viscosity, pH and total soluble solid have been studied. The results revealed that the investigated parameters had an increasing effect on the permeate flux and colour and the greatest effect on the permeate flux and colour was supplied by cross‐flow velocity. The other permeate properties did not significantly change with variations of the operating parameters. Eventually, the statistical analysis indicated that the interactional effect of cross‐flow velocity and TMP on the permeate flux was significant.     

ALTERNATIVE PRETREATMENT METHODS TO ENZYMATIC TREATMENT FOR CLARIFICATION OF MOSAMBI JUICE USING ULTRAFILTRATION

A series of pretreatment methods to mosambi juice were undertaken and results were compared to pectinase treatment for clarification of the treated juice using ultrafiltration. The pretreatment methods attempted were centrifugation, centrifugation followed by addition of gelatin, centrifugation followed by addition of bentonite, centrifugation followed by fining using both bentonite and gelatin and enzymatic treatment, using pectinase as the enzyme. A systematic study was undertaken to select the operating centrifugation speed and time. The permeate flux and quality of the permeate were comparable to the enzyme‐treated juice.     

Optimising operating conditions in ultrafiltration fouling of pomegranate juice by response surface methodology

The resistance‐in‐series model was used to analyse flux behaviour, which involved the resistances of membrane itself, the fouling and solute concentration polarisation. Response surface methodology was used to establish the relationships between operating parameters and ultrafiltration (UF) efficiency and thus to determine optimal conditions. Experiments were performed according to Box–Behnken design by changing the levels of three parameters, namely transmembrane pressure, feed flow rate and temperature. The fitted mathematical models allowed us to plot isoresponse curves. It was shown that the resistance due to solute concentration polarisation (R_cp) dominated the flux decline (40–74%). The fouling resistance (R_f) varied from 12 to 46%. To optimise simultaneously the three responses studied (R_f, R_cp and permeate limit flux), we applied the desirability function approach which allowed us to determine the best acceptable compromise. The selected UF conditions of the compromise were as follows: three bars, 0.95 L min^?1 and 30 °C. Optimal values of R_f, R_cp and permeate limit flux were equal to 18%, 72% and 19 L h^?1 m^?2, respectively.     

Carotenoids Concentration of Gac (Momordica cochinchinensis Spreng.) Fruit Oil Using Cross‐Flow Filtration Technology

Gac (Momordica cochinchinensis Spreng.) fruit, a traditional fruit in Vietnam and other countries of eastern Asia, contains an oil rich in carotenoids, especially lycopene and β‐carotene. Carotenoids in gac fruit oil were concentrated using cross‐flow filtration. In total recycle mode, effect of membrane pore size, temperature, and transmembrane pressure (TMP) on permeate flux and on retention coefficients has been exploited. Resistance of membrane, polarization concentration, and fouling were also analyzed. Optimum conditions for a high permeate flux and a good carotenoids retention are 5 nm, 2 bars, and 40 °C of membrane pore size, TMP, and temperature, respectively. In batch mode, retentate was analyzed through index of acid, phospholipids, total carotenoids content (TCC), total antioxidant activity, total soluble solids, total solid content, color measurement, and viscosity. TCC in retentate is higher 8.6 times than that in feeding oil. Lipophilic antioxidant activities increase 6.8 times, while hydrophilic antioxidant activities reduce 40%. The major part of total resistance is due to polarization (55%) while fouling and intrinsic membrane contribute about 30% and 24%, respectively.     

Combinatorial optimality of membrane morphology and feedstock during microfiltration of bottle gourd juice

The combinatorial optimality of membrane morphology and process parameters during dead end microfiltration of bottle gourd juice have been addressed in this article. Saw dust and kaolin based low cost ceramic membranes with varied morphology have been chosen to evaluate upon their microfiltration performance. For the chosen membranes, fresh, paper filtered and centrifuged juice samples were considered along with transmembrane pressure differential as process parameters. Combinatorial optimality was based on flux decline trends, fitness of fouling models, irreversible and reversible fouling data, irreversible permeation resistance and nutritional analysis of the permeate samples. An interesting feature of the article had been with respect to feed constitution playing a critical role in influencing the optimal choice of membrane morphology and transmembrane pressure differentials. Among all cases, paper filtered bottle gourd juice, 0.75 μm membrane and 137.9 kPa transmembrane pressure were found to be the best choice in terms of minimal irreversible fouling, lowest protein content, good clarity, good polyphenol and antioxidant activity in the permeate and appropriate flux.     

Optimization and Modeling of Apple Juice Cross-flow Microfiltration with a Ceramic Membrane

The performance of a 0.2 μm ceramic membrane for clarification of depectinized apple juice was studied. The results showed that the flux was higher at high feed velocities (14.6 m/seC) and high temperatures (50°C), and the transmembrane pressure was a positive factor only at high temperatures. The juice flux at optimal conditions was between 400–500 kg/hr.m². Filtration of juice with pectin resulted in flux decreases of 40–50% compared to deoectinized juice. Periodic back-flushing during processing at optimal conditions, i.e., high temperature, high feed velocity and low pressure, did not significantly increase the juice flux.     

Apple Juice Clarification using Mineral Membranes: Fouling Control by Backwashing and Pulsating Flow

New mineral membranes of ceramic (Ceraflo) and carbon (Carbone Lorraine), were used for apple juice clarification using cross flow microfiltration. Effect on performance of the parameters transmembrane pressure, inlet flow velocity, membrane nature, and temperature were studied. Optimum permeate flux was at a transmembrane pressure of about 3.5 bar for both membranes. Formation of a concentration layer of rejected particles was reduced by using techniques backwashing and pulsating inlet flow. These techniques provided a major flux restoration and steady state permeate flux increased by 30–50% with backwash and up to 100% with pulsating inlet flow.     

STUDIES ON THE CLARIFICATION AND CONCENTRATION OF BEETROOT JUICE

Studies on the clarification and subsequent concentration of beetroot juice were carried out. The juice was clarified using enzyme, fining agent (FA), centrifugation and ultrafiltration (UF), while reverse osmosis (RO) and thermovacuum evaporation were used for concentration. The juices were concentrated to 23–25°Brix, and the physicochemical characteristics were evaluated at different stages of processing on the basis of clarity, permeate flux, °Brix, acidity, sugars, pigments and CIE L*, a* and b* (lightness, redness and yellowness, respectively) color values. Average permeate flux during RO was found to be highest (36.08 liters per square meter of membrane per hour [L/m²h]) in the case of enzyme treatment, followed by UF juice, and lowest (30.33 L/m ² h) in the case of enzyme and FA treatments. In terms of clarity of concentrate, the highest value was obtained for juices pretreated with enzyme and UF. Pigment content and L*, a* and b* values showed that pigment loss was higher in the case of RO‐concentrated juice pretreated with enzyme. Comparative evaluation in terms of clarity, color and chemical parameters showed that concentrates obtained using both techniques were comparable.     

Recovery of bioactive compounds in kiwifruit juice by ultrafiltration

Food quality is not only a function of nutritional values but also of the presence of bioactive compounds exerting a positive effects on human health.This research was undertaken to study the influence of the ultrafiltration (UF) on the composition of some bioactive compounds of the kiwifruit juice in order to develop a natural product which can be used to fortify foods and beverages. At the same time the effect of transmembrane pressure (TMP) and temperature on the permeate flux was also investigated in order to identify the optimal operating conditions for the processing of the juice. An optimal TMP value occurred at 0.6–0.65 bar in different conditions of cross flow velocities. Steady-state permeate fluxes increased linearly with temperature in the range 20–30 °C.The kiwifruit juice was clarified in optimal operating conditions, according to the batch concentration mode, up to a final volume reduction factor (VRF) of 2.76.The analyses of flux decay according to fouling models reported in the literature revealed that the formation of a cake layer covering the entire surface of the membrane is the main cause of the membrane fouling.Most bioactive compounds of the depectinised kiwifruit juice were recovered in the clarified fraction of the UF process. The rejection of the UF membrane towards total phenolics was 13.5%. The recovery of glutamic, folic, ascorbic and citric acids, in the clarified juice, with respect to the initial feed, was dependent on the final VRF of the UF process: an increase of the VRF determines an increase of these compounds in the clarified juice. The rejections of the UF membrane towards these compounds were in the range 0–4.3%.

Industrial relevance

Among different substances contained in the kiwifruit a primary role, in the safeguard of the human health, is carried out by some bioactive compounds such as ascorbic, folic, citric, glutamic acids and polyphenols.This research was undertaken to study the influence of ultrafiltration on the composition of these compounds in order to develop a natural product which can be used to fortify foods and beverages.     

Effects of various clarification treatments on phenolic compounds and color of apple juice

The purpose of this study was to investigate the changes that occur during conventional clarification using gelatin, bentonite, silica sol, and water-soluble chitosan on the phenolic compounds, antioxidant activity, and color of apple juice. The apple material used in this study was of two varieties: Sampion and Idared. The changes in the polyphenols composition (procyanidins, hydroxycinnamic derivatives, and dihydrochalcones) were monitored through the clarification process. Sampion apple control juices contained more total polyphenols than do Idared apple juices. In Sampion variety apple juice, the dominant polyphenols are the flavan-3-ols (86% of total polyphenols), followed by hydroxycinnamic acids (9.7%), dihydrochalcones (3.0%), and flavonols (1.3%). In Idared apple juice the hydroxycinnamic acids (especially chlorogenic acid) are dominant (about 48% of total polyphenols), followed by flavan-3-ols (40%). However, the concentration of polymeric procyanidins in Sampion apple juices was 62.8 and 46.3% less when the Profloc (chitosan) and gelatin treatments were used, respectively. Aktivbentonit and Puranit (bentonite) supplementary added in juices clarification have some protective effect on polymeric procyanidins only with Profloc treatment. That kind of effect was not observed in Idared apple juices with almost eight times smaller polymeric procyanidins concentration than in Sampion apple juices. The antioxidant activity, measured by the DPPH (1,1-diphenyl-2-picrylhydrazyl radical) method, ranged from 0.20 mg TEAC/mL in Idared apple juice to 0.30 mg TEAC/mL in Sampion apple juice, measured by the ABTS method, from 0.17 to 0.48 mg TEAC/mL, respectively. Clarification of apple juices with chosen clarifying agents has statistically no significant (p>0.05) influence on antioxidant capacity. This study suggests that chitosan can be used as a conventional clarifying aid of apple juices and that treatment has no impact on their biochemical parameters.     

Hyperfiltration of Tomato Juice: Pilot Plant Scale High Temperature Testing

A two-stage tubular hyperfiltration (reverse osmosis) pilot plant equipped with 15.6 m² of aromatic polyamide thin film composite membrance (ZF 99) was studied with tomato juice (4–6% natural tomato soluble solids [NTSS]). It was operated over 100 hr in recirculation and single pass modes. The single pass mode was operated at33–38 bar (feed inlet pressure) and 70–93°C for 18.2 hr. Stage 1 flux was 48 to 34 Lm^?2hr^?1. Stage 2 flux was 30 to 20 Lm^?2hr^?1. Concentration went to 7.4–9.0% NTSS at 8.6 L/min, and to 6.3–6.4% NTSS at 18.6 L/min. NTSS rejection was >98%. Of permeate samples tested none showed detectable levels of sugars; only 25% showed detectable levels of organic acids.     

Synergistic effect of particle size,shear rate and driving-force during microfiltration of fruit juices: Toward a relevant choice of pretreatments and filtration conditions

With an objective to recommend relevant operating conditions for fruit juice microfiltration, the combined effect of particle size, shear rate and driving-force on fouling was studied. The filterability of three orange juices with different granulometry was estimated at pilot scale under different shear rates and driving forces (flux or TMP, in immersed and side-stream membrane configuration respectively). In flux-driven filtrations, fluxes to avoid an intense fouling were identified (below 5–10 L.h⁻¹.m⁻² for studied juices) and the role of juice granulometry on fouling highlighted. In TMP-driven filtrations, whatever the juice granulometry, steady-state fluxes were TMP-independent but shear rate dependent (around 10 and 30 L.h⁻¹.m⁻², for 4500 s⁻¹ and 15500 s^-1 respectively). The results demonstrated that, whatever their granulometry, juice filterability was higher in low shear rate flux-driven filtrations, than in high shear rate TMP-driven ones, which relativizes the relevance of crossflow filtration.     

Beer Clarification Using Ceramic Tubular Membranes

In this work, laboratory-made green beers were produced using a commercial hopped malt extract and used to study their cross-flow microfiltration (CFMF) performance in a bench-top plant, appropriately designed and equipped with ceramic tubular membrane modules with nominal pore size of 0.4, 0.8, or 1.2 μm, under different values of the initial green beer turbidity (H?≡?0.7–61.9 European Brewery Convention (EBC) unit), feed superficial velocity (v _S?≡?2–6 m s^?1), and transmembrane pressure difference (TMPD?≡?0.97–4.73 bar) under constant temperature (~10 °C). Whatever the membrane pore size and rough beer turbidity, the minimum quasi-steady-state value of the overall membrane resistance \( \left({\mathrm{R}}_{\mathrm{T}}^{*}\right) \) was obtained at TMPD of 3 to 4 bar and v _S?=?6 m s^?1. The 0.8-μm pore membrane was selected for the loss in the permeate density, and color was limited, while the volumetric permeation flux was high enough. Then, it was used to assess a double logarithmic trend between the quasi-steady-state permeation flux (J*) and beer turbidity with a limiting flux of 63?±?6 L m^?2 h^?1 for H?>?21 EBC units. Precentrifuged beer feeding resulted in 2.7- to 4.1-fold increase in J* with respect to the above limiting flux, provided that the haze level of rough beer had been reduced to 1.0 or 0.7 EBC unit, respectively. The cake filtration fouling mechanism was identified as the main reason for flux decline by analyzing mathematically the time course of both the experimental permeate volume and permeation flux data. By operating with the aforementioned clarified green beers at TMPD of 3.73 bar, v _S of 6 m s^?1, and periodic CO₂ backflushing, the average permeation flux (300–385 L m^?2 h^?1) resulted to be from three to five times higher than that (80–100 L m^?2 h^?1) at 0–2 °C claimed by the three commercial CFMF processes currently available.     

ANALYSIS OF THE FOULING MECHANISM IN MICROFILTRATION OF ORANGE JUICE

The purpose of this work is theoretical and experimental evaluation of fouling effects on flux performance in clarification of freshly squeezed orange juice by cross-flow microfiltration. To identify optimum operating conditions to minimize fouling effects, juice was microfiltered on a laboratory scale plant varying axial velocity and transmembrane pressure difference. The observed flux decay was modeled using a modified form of the differential equation used to describe classical dead-end filtration processes. The mechanism of fouling during cross-flow microfiltration was identified by estimation of the model parameters according to a nonlinear regression optimization procedure. Analysis of the results revealed that the separation process is controlled by a cake filtration fouling mechanism as the juice is fed at relatively low velocity (i.e., Re = 5000) and the system is operated at low transmembrane pressure difference. In these operating conditions the permeate flux decays within the first 20–30 min to gradually achieve a limit value. At higher Reynolds number (Re = 15,000), an increase in applied transmembrane pressure (i.e., from 0.3 to 1 bar) allows the limit permeate flux to increase by a factor of about 4. In these conditions the filtration process is controlled by a complete pore blocking fouling mechanism, and the permeate flux becomes approximately invariant with respect to time, and a negligible decay may be observed. Evaluation of specific energy consumption involved in the filtration process is reported.