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.     

Cross-flow Microfiltration with Gas Backwash of Apple Juice

Cross-flow microfiltration (MF) was applied for clarification of commercially pressed depectinized apple juices and pectin containing artificial apple juice suspensions under continuous low pressure inlet conditions (35 kPa - 209 kPa). Periodic gas backwash (air or N₂) removed solids from exteriors of 0.2 μm cut-off hollow fiber polypropylene membranes. Flux and nephelos turbidity units (NTU) of filtrates for both commercial juices and artificial juices were evaluated. Commercial juices after vacuum filtration and MF had 100–110 L/m²/hr flux during 2 hr operation. Low pectin (1%) artificial juices had ～70 L/m²/hr flux during 1.5 hr. NTUs of filtrates from all treatments were <0.69. All filtrates were commercially sterile.     

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 of Pear Juice by Hollow Fiber Ultrafiltration

Hollow fiber ultrafiltration was successfully applied to obtain a clear, amber-colored pear juice. For the three hollow fiber membrane cartridges tested (50,000, 30,000, and 10,000 dalton molecular weight cut-off), the process parameters were optimized and found to be similar. The permeate flux increased with increased transmembrane pressure and then declined. Flux reached a maximum at an average transmembrane pressure of 157 kPa with an average feed stream velocity of 0.15 meters/set at 50°C. Higher flux was obtained at higher temperatures within the temperature limitations of the membrane. Flux decreased linearly with the logarithm of the concentration.     

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.     

MICROFILTRATION OF RED BERRY JUICE WITH THREAD FILTERS: EFFECTS OF TEMPERATURE, FLOW AND FILTER PORE SIZE

A series of experiments was conducted to demonstrate the applicability of a new Filtomat® thread filtration principle for microfiltration of semiprocessed blackcurrant juice and cherry juice. The effect of juice temperature (3–20C), flow (20–80 L/h), and filter pore size (3–10 μm) on the transmembrane pressure, juice turbidity, protein, sugar, and total phenols levels was evaluated in a lab scale microfiltration unit employing statistically designed factorial experiments. Thread microfiltration reduced significantly the turbidity of both juices. For blackcurrant juice, in all experiments, the turbidity was immediately reduced to the level required for finished juice without compromising either the protein, the sugar or the phenols content. High flow rates increased the turbidity in blackcurrant juice, but did not affect cherry juice quality. Filtomat® thread microfiltration therefore appears suitable as a novel technology for berry juice processing, especially for blackcurrant juice filtration.     

陶瓷膜超滤净化石灰法制糖清汁

对孔径为0.04?μm的陶瓷超滤膜进一步净化石灰法制糖的清汁进行研究,在跨膜压差0.45～0.50?MPa、膜面流速4.0～4.5?m/s、过滤温度75～97?℃的条件下过滤甘蔗汁30?h,膜渗透通量从350.6?L/（m2·h）降低至160.2?L/（m2·h）,平均通量为177.8?L/（m2·h）,能满足工业化生产的需求。甘蔗汁经陶瓷膜过滤后品质被进一步提升,简纯度可提高2.01?个单位,色素去除率为20.20%,澄清度从79.18%提升至99.98%。研究膜污染形成发现,陶瓷膜过滤甘蔗汁会在膜表面形成一层污染层,膜污染物的主要成分为有机物（多糖、蛋白质、酯类及酚类等物质）,同时还含有少量的Na、Mg、Al、Si、P、Cl、K、Ca及Fe等无机成分。污染膜依次采用工业净水、1%?NaOH-0.5%?NaClO混合溶液、0.5%?HNO3溶液清洗,膜通量恢复率均高于95.5%,重复性较好,是一种有效的膜清洗方法。     

Mechanism of Permeate Flux Decline during Microfiltration of Watermelon (<Emphasis Type="Italic">Citrullus lanatus</Emphasis>) Juice

Flux decline mechanism during microfiltration of watermelon juice was studied in detail. Identification of the flux decline mechanism was carried out by conducting experiments in an unstirred batch cell. Using the identified mechanism, flux decline was predicted during stirred microfiltration in a continuous mode. The operating pressure range was from 137 to 276 kPa and that of Reynolds number was 1.40 × 10⁵ to 1.87 × 10⁵. Cake formation was identified as the main reason for flux decline. Prediction of flux decline during stirred continuous microfiltration using this mechanism was found adequate.     

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.     

Evaluation of the fouling phenomenon in the membrane clarification of black mulberry juice

Mixed cellulose ester (MCE) flat membranes were used to clarify black mulberry juice, the yield of which was limited by fouling. The effects of membrane pore size (0.025, 0.1 and 0.22 μm), transmembrane pressure (0.5, 1, 1.5 and 200 kPa), and cross‐flow velocity (0.1, 0.2, 0.3 and 0.4 m s^?1) on membrane fouling were evaluated; the results showed that fouling increased with increased pore size and pressure, and decreased with increased velocity. Analysis of different resistances showed that both reversible and irreversible fouling resistances have an important role in fouling‐resistance changes. There is no cake resistance in all processes. Microstructure analysis of membrane using scanning electron microscopy confirmed the theory that intermediate blocking was the dominant fouling mechanism in MCE 0.025 μm, and standard blocking was the dominant mechanism in MCE 0.1 and 0.22 μm.     

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.     

Modeling flux behavior for membrane filtration of apple juice

The flux behavior of ceramic membranes with different pore sizes (0.2, 0.1 and 0.02 μm) was examined during dead-end membrane filtration of depectinized control (CTJ) and ascorbic acid treated (AAJ) apple juices. A new model based on an expanded exponential relationship was developed. The model represented the flux with precision over the entire filtration process for both juice types and all membrane pore sizes. Two parameters, A and B, provided a measure of the rate of flux decline. The same approach was used to model the permeate flux of CTJ for various 0.2 μm pore size polymeric membrane materials operated in a dead-end mode, and for tubular ultrafiltration membranes of different pore sizes (9, 20 and 100 kDa) operated in crossflow mode.     

陶瓷膜在甘油发酵液除菌中的应用

将陶瓷膜应用于甘油发酵液的除菌操作中,考察了操作参数和清洗方法对膜通量的影响。结果表明,在压差0.1MPa、温度30℃、pH值7.0和错流速度3.5m/s条件下操作,有利于提高膜通量;发酵液过滤后,先以质量浓度为1%的NaOH和质量浓度为0.2%的NaClO混合液清洗膜40min,再以质量浓度为0.5%的HNO3溶液清洗5min,膜通量可迅速恢复。因此,陶瓷膜在甘油发酵液的除菌中是高效可行的。     

Clarification of Apple Juice by Hollow Fiber Ultrafiltration: Fluxes and Retention of Odor-Active Volatiles

Fresh apple juice was clarified in a pilot scale ultrafiltration (UF) unit, with membranes made of polysulfone and polyamide and plate and frame and vacuum drum filters. Flux of apple juice (L/m² hr) vs UF transmembrane pressure data showed an optimum at a pressure of about 140 kPa. Retention of odor-active volatiles was highest in plate and frame filtered apple juice and lowest in vacuum drum filtered juice; the retention of odor-active volatiles in UF juice was intermediate to the two traditional filtration methods. Retention of odor-active volatiles in the permeate of a polyamide membrane was higher than that of a polysulfone membrane.     

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.     

Influence of gas sparging on clarification of pineapple wine by microfiltration

A microfiltration process with a tubular ceramic membrane was applied for clarification of pineapple wine. The process was operated with the membrane pore size of 0.2 μm at transmembrane pressure of 2 bar and crossflow velocity of 2.0 m/s. The effects of gas sparging on permeate flux, fouling and quality of clarified wine were studied. It was found that a relatively low gas sparging rate could increase permeate flux up to 138%. Further increase of the gas sparging rate did not improve permeate flux compared with that without gas sparging. Gas sparging affected the density of cake layer. Increasing gas sparging rate led to an increase in specific cake resistance. It was observed that increasing gas sparging rate could reduce reversible fouling rather than irreversible fouling. The turbidity of pineapple wine was reduced and a clear product with bright yellow color was obtained after microfiltration. The negative effect of gas sparging which caused a loss of alcohol content in the wine was also observed.     

Coupling of pressure-driven membrane technologies for concentrating,purifying and fractionizing betacyanins in cactus pear (Opuntia dillenii Haw.) juice

An integrated process coupling crossflow micro and ultra or nanofiltration was applied to separate the betacyanins in cactus pear juice (30 °C). Four microfiltration ceramic membranes (0.1–0.2 μm, 1.8–3.3 bar) and 4 ultra/nanofiltration organic membranes (0.2–4.0 kDa, 5–30 bar) were tested. Microfiltration was a first step to remove insoluble solids with low retention of soluble solids. By coupling with enzymatic liquefaction, permeate flux Jp was increased by 2 and the retention of betacyanins was limited. Ultra/nanofiltration was then used for solute separation. Retentions of solutes could be modulated by varying membrane/pressure combinations that favor rather the concentration of all the solutes or rather the purification of the betacyanins with respect to the total dry matter. Retention of individual betacyanins could be a little different which also made possible fractionation. Simulations using simple models allowed to evaluate the interest of the process for concentrating, purifying and fractionating betacyanins with a possible diafiltration step.Industrial relevanceBetacyanins are natural colorants that can be obtained from cactus pear juice, a crop of increasing interest for its agricultural potential in Sahelian regions. The aim of this study was to evaluate a new integrated process based on membrane separation allowing to concentrate or separate betacyanins from other solutes at low temperature and with a limited environmental impact. This process associates a first step to clarify the cactus pear juice by microfiltration after enzymatic liquefaction and a second step to concentrate or purify betacyanins by ultra or nanofiltration. By choosing different membrane/transmembrane pressure combinations in the 2nd step, solute retentions could be modulated in order to favor rather the concentration of all solutes or rather the separation of betacyanins from total soluble solids or even rather the fractionation of betacyanins themselves.     

Microfiltration of whey proteins adsorbed on yeast cells

Soluble whey proteins (WPs), adsorbed on yeast cells, were recovered by a crossflow microfiltration (MF) technique using a cellulose nitrate membrane with a pore size of 0.45 μm. The crossflow velocity was 1.5 m s^?1 with a transmembrane pressure of 200 kPa at 25 °C. A series of protein rejections occured at various pH values ranging from 2 to 8. WPs adsorbed more on to yeast cells at low pH (pH < 4) than at high pH values, probably because they were positively charged at low pH. It was also shown that permeate flux increased and Modified Membrane Fouling Index values decreased at low pH levels. When the yeast concentration was 50 g L^?1, the flux decreased five times compared with that in the absence of yeast. Protein recovery increased with increasing yeast concentrations. The highest protein recovery was found to be 85% at a yeast concentration of 50 g L^?1 at a steady state flux rate of 10^?6 m s^?1 at 25 °C. When diluted solutions of whey were used, the same rejection of protein, adsorbed on yeast cells, was achieved at ten times lower amounts of yeast cells. This technique not only provides for the recovery of protein but also may give rise to the direct use of yeast cells, which are rich in protein, in the baking industry. WPs absorbed by yeast cells can be used to produce nutritionally rich products in areas where yeasts have been already used.     

Crossflow microfiltration of gum arabic solutions: Comparison of the classical system with the co-current permeate flow system

Gum arabic is a natural gum exuded mainly by the trees Acacia senegal , currently used in the food industries for its emulsifying, thickening and stabilizing properties. Its present processing includes various operations providing a quite turbid product. Crossflow microfiltration could be interesting for the clarification and the cold-pasteurization of the gum arabic solutions. Several experiments were therefore made with the crossflow microfiltration unit at ENSIA, using two different systems: the classical one (without permeate circulation), and the co-current permeate flow system (CCPF) allowing the exploration of the low transmembrane pressures range. With gum arabic solutions of 0.17g solids g⁻¹ solution and 70°C, the best results after 60 min of filtration (105.7 L h⁻¹ m⁻², 4.4% of solids retention and 83.4% of clarification) were obtained with the CCPF system at low transmembrane pressure and high crossflow velocity (0.3 bar and 7.5ms⁻¹).     

Influence of operating conditions on membrane fouling in crossflow microfiltration of particulate suspensions

The effects of the operating conditions on the crossflow microfiltration (CFMF) of particulate suspensions were investigated. Lactalbumin particles were used as the feed material. Experiments were carried out in constant transmembrane pressure (TMP) mode using tubular ceramic membrane modules. All important parameters (internal and surface fouling, cake mass, height, porosity, and particle size distribution (PSD)) were estimated to provide a more complete understanding of the process than has been attempted before. Lactalbumin particles which are highly irregular in shape and widely size distributed formed an adhesive cake on the membrane surface during CFMF. The porosity and particle size of the deposited cake decreased with time of filtration. The value 100 kPa was found to be optimum with respect to the permeate flux in the studied range of TMP. Particle size classification effects of TMP and crossflow velocity (CFV) were demonstrated. The results of this study provided a possible explanation to the contradictory reports on the effect of CFV on the steady-state flux and the time required to obtain it. Significantly, the internal fouling first decreased with increasing CFV and then increased above 1.5 m s⁻¹. This is attributed to the particles size classification effect of CFV. A process was developed based on the observed effects of the operating parameters on the CFMF performance that enables operation at very low internal fouling and high flux for as long as 160 min. The developed process has the potential to become commercial if coupled with backflushing.