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.     

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.     

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.     

Physiochemical, antioxidant and whitening properties of extract from root cortices of mulberry as affected by membrane process

Extract from root cortices of mulberry (Morus alba, L.) was separated into permeate and retentate fractions using a membrane system equipped with either a microfiltration membrane or one of four molecular weight cut-off ultrafiltration membranes. The effects of membrane process at volume concentration ratio (VCR)=4 on the physiochemical characteristics, the contents of active compounds, antioxidant ability, and whitening capability (tyrosinase inhibitory activity) in permeate and retentate were evaluated. The clarification degree, antioxidant effects, and whitening capability of the permeates increased as compared to those of feed. In addition, permeate treated with a 0.45 μm microfiltration membrane exhibited less fouling layer and specific resistance (αpC_B=622.8 m⁻²×10⁻⁶) and thus had a higher permeate flux than treated with other ultrafiltration membranes (αpC_B=786.1-1025.3 m⁻²×10⁻⁶). A higher content of active compounds, such as chlorogenoic acid and p-hydroxybenzoic acid may explain higher antioxidant and whitening capabilities in permeate of extracts from root cortices of mulberry.     

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.     

Low cross-flow velocity microfiltration of skim milk for removal of bacterial spores

The use of microfiltration membranes in the dairy industry to remove bacterial spores has been applied for some time using the so-called “bactocatch” process. However, these microfiltration units have high energy demands since high linear velocities are required during operation, to avoid problems related to fouling and concentration polarization. In this work, optimization of a backflushing technique combined with reverse asymmetric membranes (‘backshock’ technique) was used to avoid the fouling and concentration polarization problems, allowing the use of low linear velocities and resulting in low-energy costs. In the novel ‘backshock’ technique, the permeate is pressurized during a very short time interval (less than 1 s) and with a frequency around 0.2-1 s⁻¹. The benefit of using a reverse asymmetric membrane is related to the formation of a very open fouling layer just inside the porous support layer and the build-up of a concentration profile of the proteins inside the porous structures. The microfiltration of skim milk using ceramic and polymeric membranes was studied with different membrane structures. The backshock technique, combined with reverse asymmetric membranes of pore size of 0.87 μm, allows the effects of concentration polarization and fouling to be controlled, achieving very high (500 L h⁻¹ m⁻²) and stable fluxes with 100% casein transmission and a high retention of spores (reduction by a factor 10⁴-10⁵) even at low linear velocities (0.5-1 ms⁻¹).     

A physicochemical investigation of membrane fouling in cold microfiltration of skim milk

The main challenge in microfiltration (MF) is membrane fouling, which leads to a significant decline in permeate flux and a change in membrane selectivity over time. This work aims to elucidate the mechanisms of membrane fouling in cold MF of skim milk by identifying and quantifying the proteins and minerals involved in external and internal membrane fouling. Microfiltration was conducted using a 1.4-μm ceramic membrane, at a temperature of 6 ± 1°C, cross-flow velocity of 6 m/s, and transmembrane pressure of 159 kPa, for 90 min. Internal and external foulants were extracted from a ceramic membrane both after a brief contact between the membrane and skim milk, to evaluate instantaneous adsorption of foulants, and after MF. Four foulant streams were collected: weakly attached external foulants, weakly attached internal foulants, strongly attached external foulants, and strongly attached internal foulants. Liquid chromatography coupled with tandem mass spectrometry analysis showed that all major milk proteins were present in all foulant streams. Proteins did appear to be the major cause of membrane fouling. Proteomics analysis of the foulants indicated elevated levels of serum proteins as compared with milk in the foulant fractions collected from the adsorption study. Caseins were preferentially introduced into the fouling layer during MF, when transmembrane pressure was applied, as confirmed both by proteomics and mineral analyses. The knowledge generated in this study advances the understanding of fouling mechanisms in cold MF of skim milk and can be used to identify solutions for minimizing membrane fouling and increasing the efficiency of milk MF.     

Beer Clarification by Novel Ceramic Hollow‐Fiber Membranes: Effect of Pore Size on Product Quality

In this work, the crossflow microfiltration performance of rough beer samples was assessed using ceramic hollow‐fiber (HF) membrane modules with a nominal pore size ranging from 0.2 to 1.4 μm. Under constant operating conditions (that is, transmembrane pressure difference, TMP = 2.35 bar; feed superficial velocity, v_S = 2.5 m/s; temperature, T = 10 °C), quite small steady‐state permeation fluxes (J^*) of 32 or 37 L/m²/h were achieved using the 0.2‐ or 0.5‐μm symmetric membrane modules. Both permeates exhibited turbidity <1 EBC unit, but a significant reduction in density, viscosity, color, extract, and foam half‐life with respect to their corresponding retentates. The 0.8‐μm asymmetric membrane module might be selected, its corresponding permeate having quite a good turbidity and medium reduction in the aforementioned beer quality parameters. Moreover, it exhibited J^* values of the same order of magnitude of those claimed for the polyethersulfone HF membrane modules currently commercialized. The 1.4‐μm asymmetric membrane module yielded quite a high steady‐state permeation flux (196 ± 38 L/m²/h), and a minimum decline in permeate quality parameters, except for the high levels of turbidity at room temperature and chill haze. In the circumstances, such a membrane module might be regarded as a real valid alternative to conventional powder filters on condition that the resulting permeate were submitted to a final finishing step using 0.45‐ or 0.65‐μm microbially rated membrane cartridges prior to aseptic bottling. A novel combined beer clarification process was thus outlined.     

Influence of feed properties on membrane fouling in crossflow microfiltration of particulate suspensions

The effects of the feed concentration (C_feed) and particle size distribution (PSD) on the crossflow microfiltration (CFMF) of suspensions containing lactalbumin particles were investigated. Experiments were carried out in constant transmembrane pressure (TMP) mode using tubular ceramic membrane modules. All the important parameters: permeate flux, internal and surface fouling, cake mass, height, porosity, and PSD were estimated. The steady-state flux (J_ss) decreased, and internal as well surface fouling and cake mass and height all increased with an increase in C_feed from 0.65 to 2.5 gL⁻¹. This was due to the availability of more particles to foul the membrane at higher C_feed. However, above 2.5 gL⁻¹ there was no significant effect of C_feed on any of these parameters. The overall observed behaviour is attributed to steady-state membrane fouling resulting from the availability of sufficient particles for maximum possible deposition under the experimental conditions reached at 2.5 gL⁻¹. The larger the feed particles, the higher was the J_ss. However, the cake mass, height and porosity were not affected by the feed PSD. Significantly, addition of larger feed particles at the steady state increased the flux by about 6%. This behaviour is attributed to the scouring effect of the large particles on the cake surface. There is scope for looking at the possibility of using the scouring effect of large particles to improve the CFMF process performance.     

Fouling Analysis and Performance of Tubular Ultrafiltration on Pretreated Olive Mill Waste Water

This study deals with the performance of a tubular ultrafiltration system on sieved and centrifuged olive mill waste water. A generalized statistical model was developed describing the impact and the relative importance of major experimental parameters (membrane pore size, transmembrane pressure, feed flow rate, and feed temperature) on permeate flux. According to this model, process pressure appeared to have the largest impact on permeate flux, followed by process temperature. As membrane treatment of such a difficult material largely depends on fouling, a systematic analysis of prevailing fouling mechanisms was also run. Despite sieving and centrifugation of the original waste, membrane fouling caused a flux decline of 60–65% within 15–20 min. Internal fouling, pore blocking, and cake layer formation were all responsible for membrane fouling during the first 40 min of operation. After that period, cake formation appeared to play a predominant role. Based on the proposed generalized model, the relative importance of process parameters can be evaluated and process performance can be improved by proper interventions. Independent of membrane size, fouling is a serious problem to be resolved. The qualitative performance of this process, including chemical oxygen demand distribution, polyphenol profile, and antioxidant capacity, is discussed in a separate paper.     

Fourier wavelets from ultrasonic spectra: a new approach for detecting the onset of fouling during microfiltration of paper mill effluent

Nondestructive (NDT) and noninvasive ultrasonic techniques have long been used to evaluate the properties and especially the thickness of thin layers. Here, we use this technique adding a new approach to investigate microfiltration of paper mill wastewater, which gives an unexpected sensitivity in the detection of membrane fouling. In situ ultrasonic reflections data can indicate an early fouling deposition at about 30 s after filtration starts, evident by an initial decline in permeate flux. By producing differential signals, obtained by comparing reference and testwaveforms, the fouling process can be detected and monitored. A linear relationship between fouling resistance and the amplitude of differential signals exists. In the case of fouling layer thickness, the resolution exceeds the theoretical limit of h/lambda +/- 0.25, where h is the layer thickness and lambda is the wavelength. When using differential signals, excellent results for thickness measurements were obtained, down to h/lambda = 0.04. Measurements on wavelet transforms support the findings and add quantitative information on other physical properties such as density and porosity of fouling layers and the fouling process. Measurement of early fouling allows (automated) remedial methods to be applied so as to maintain a high flux and therefore improve the filtration process.     

Filtration of milk fat globule membrane fragments from acid buttermilk cheese whey

The proteins and polar lipids present in milk fat globule membrane (MFGM) fragments are gaining attention for their technological and nutritional properties. These MFGM fragments are preferentially enriched in side streams of the dairy industry, like butter serum, buttermilk, and whey. The objective of this study was to recover MFGM fragments from whey by tangential filtration techniques. Acid buttermilk cheese whey was chosen as a source for purification by tangential membrane filtration because it is relatively rich in MFGM-fragments and because casein micelles are absent. Polyethersulfone and cellulose acetate membranes of different pore sizes were evaluated on polar lipid and MFGM-protein retention upon filtration at 40°C. All fractions were analyzed for dry matter, ash, lipids, proteins, reducing sugars, polar lipid content by HPLC, and for the presence of MFGM proteins by sodium dodecyl sulfate-PAGE. A fouling coefficient was calculated. It was found that a thermocalcic aggregation whey pretreatment was very effective in the clarification of the whey, but resulted in low permeate fluxes and high retention of ash and whey proteins. By means of an experimental design, the influence of pH and temperature on the fouling and the retention of polar lipids (and thus MFGM fragments), proteins, and total lipids upon microfiltration with 0.15 μM cellulose acetate membrane was investigated. All models were highly significant, and no outliers were observed. By increasing the pH from 4.6 to 7.5, polar lipid retention at 50°C increased from 64 to 98%, whereas fouling of the filtration membrane was minimized. A 3-step diafiltration of acid whey under these conditions resulted in a polar lipid concentration of 6.79 g/100 g of dry matter. As such, this study shows that tangential filtration techniques are suited for the purification of MFGM fragments.     

Assessment of quality and production process of a non‐alcoholic stout beer using reverse osmosis

The market for low‐alcohol and non‐alcoholic beer has been increasing owing to factors such as health concerns, calorie content, strict traffic laws and religion, among others. Beer presents some good nutritional characteristics such as B‐complex vitamins, antioxidants, minerals, fibre, protein and carbohydrates. The availability of non‐alcoholic products is still very low in Brazil and worldwide. This study produced four samples of non‐alcoholic dark beer derived from a Foreign Extra Stout beer style with 6.6% v/v alcohol using the process of reverse osmosis. The membrane filtration processes showed that the fouling rate coefficient increases with time and permeate volume while the flow decreases. The values of colour, bitterness, pH, phenolic compounds and antioxidant activity were maintained close to the parameters of the standard beer (counter test) when the reverse osmosis process was conducted with a diluted sample at a temperature of 20 °C. Copyright © 2016 The Institute of Brewing & Distilling     

生啤酒膜滤除菌技术试验研究

针对生啤酒膜滤除菌技术。采用无机陶瓷膜、对膜孔径的选择、膜器结构优化、膜滤运行过程强化等方面进行了系统的试验研究,提出了一套新型高效的膜器结构与工艺设计的依据。     

Novel Procedure for Lager Beer Clarification and Stabilization Using Sequential Enzymatic,Centrifugal, Regenerable PVPP and Crossflow Microfiltration Processing

In this work, the crossflow microfiltration (CFMF) performance of different lots of lager beer, produced in a pilot scale at the Italian Brewing Research Centre (CERB, Perugia, Italy), was assessed in a bench-top plant, equipped with a 0.8-μm ceramic tubular membrane module, under constant crossflow velocity of 6 m s^?1, transmembrane pressure difference of 3.74 bar, temperature of ~10 °C, and periodic CO₂ backflushing. By feeding different beer samples (i.e., as such, precentrifuged (C), or pretreated with a commercial enzyme preparation to degrade the original arabinoxylans and β-glucans and then centrifuged (EC) to minimize the fouling contribution of yeast cells, aggregates, and polysaccharides), it was possible to increase the average permeation flux (expressed as mean value?±?standard deviation) from 112?±?13 to 199?±?17 or 330?±?22 L m^?2 h^?1, respectively. Only when using the EC-pretreated beer specimens, the permeate turbidity at 20 °C approached the limiting one (<0.6 EBC unit) recommended by the European Brewery Convention standards. As expected, the permeate chill haze at 0 °C was generally higher than the above haze target. By submitting EC-pretreated beer seeded with 0.5 g L^?1 of regenerable polyvinylpolypyrrolidone (PVPP) to CFMF, it was possible to reduce the initial total polyphenol content by 30 % and permeate chill haze to 0.60?±?0.01 EBC unit, but the average permeation flux fell to 84?±?4 L m^?2 h^?1. By performing sequentially EC pretreatments, PVPP stabilization, cartridge filtration, and CFMF, it was possible not only to re-enhance the average permeation flux at about 230 L m^?2 h^?1 near to those achievable with DE filters, but also to obtain a chill haze-free permeate ready for aseptic packaging.     

Effect of fractal flocculation behavior on fouling layer resistance during apple juice microfiltration

The colloidal material in juice obtained from Red Delicious apples held in cold storage for over 6 months was observed to spontaneously aggregate to form ordered flocculation patterns. These flocculation patterns could be altered by heat treatment and by gelatin or antioxidant addition. The specific resistance of the fouling layer produced by each juice during microfiltration could be qualitatively predicted by examining the structure of macroscopic flocculation patterns. Environmental scanning electron microscopy (ESEM) photos of the various hydrated fouling layers indicated that loose flocs appeared to compress and rearrange on the membrane surface, producing smooth, low porosity secondary membranes. Densely packed cross-linked aggregate networks also formed low porosity structures, once again creating a fouling layer with high resistance. The lowest resistance fouling layers were produced when the flocs were dense enough to resist compression but porous enough to provide pathways for permeate flow. Field emission scanning electron microscopy (FESEM) and ESEM images indicated that, in many cases, the spacial distribution of solids in the microscopic aggregates were reminiscent of those in the macroscopic flocs. Such scaling relationships are typical of fractal systems.     

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.     

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.     

ENZYMES IMMOBILIZED ON FORMED-IN-PLACE MEMBRANES FOR FOOD PROCESSING: PROCEDURES and PROPERTIES

The formation and properties of Formed-In-Place (FIP) membranes upon which enzymes had been immobilized were investigated to examine the potential of these reactive membranes in food processing applications. Enzymes were immobilized on two types of FIP membranes and their activities in appropriate fluids investigated. Flux was increased in the microfiltration of pectin solutions by immobilizing pectinase on titanium dioxide microfiltration membranes. A flux increase of 15% was obtained without permeate recycle and 112% with permeate recycle using a 0.1% solution of citrus pectin. Glucose production from dextrin was performed using glucoamylase (GA) immobilized on a zirconium hydrous oxide-polyacrylate nanofiltration membrane. Optimum activity occurred at pH 4.0 and 50C for the immobilized GA. the dextrose equivalent (DE) value of the membrane permeate was approximately ten times higher than the product obtained with free GA during the same time interval.     

Effect of Fouling on Flux and on Energy Requirements in Reverse Osmosis of Skim Milk

The effects of fouling on the permeate flux and on the power and energy required in the process of concentrating skim milk by a plate and frame type reverse osmosis unit with 990 type cellulose-acetate membranes were investigated. The permeate flow characteristics indicate that the fouling layer is rapidly formed and that its resistance is nearly constant over reasonable processing intervals. These fouling properties permit the correlation of permeate flow, overall mass transfer coefficient, and osmotic pressure difference in terms of the energy required per permeate volume versus time. This correlation shows a decrease in energy required per permeate volume with increasing mass transfer coefficient and time. These flow characteristics permit the estimation with confidence of the permeate flow energy requirements and the capacity of a full scale plant. Mass transfer coefficients were estimated for the membrane, the polarized layer, and the fouling layer. The overall mass transfer coefficient was then calculated. The polarized and fouling layers are films of components from the skim milk. Fouling was the controlling resistance.