Martine Decloux

Concentration of passion fruit juice on an industrial pilot scale using osmotic evaporation

Osmotic evaporation to concentrate clarified passion fruit juice was tried out on an industrial scale. A pilot plant that was equipped with a module containing 10.2 m(2) of polypropylene hollow fibres was used to concentrate passion fruit juice up to a total soluble solids (TSS) content higher than 60 g/100 g at 30 degreesC. Tangential velocity, temperature and concentration of solutions significantly influenced evaporation flux. An average evaporation flux of almost 0.75 kg h(-1) m(-2) was obtained with water, 0.65 kg h(-1) m(-2) when juice was concentrated to 40 g TSS/100 g and 0.50 kg h(-1) m(-2) when it reached 60 g TSS/100 g. A long-term trial, lasting 28 m(-2), was successfully carried out without membrane fouling. Osmotic evaporation can be also conducted as a multistage procedure, giving a constant evaporation flux of around 0.62 kg h(-1) m(-2) when juice was concentrated from 14 to 60 g TSS/100 g. Sensory quality and vitamin C content were well preserved in the concentrated juice

Strategy for economical optimisation of the clarification of pulpy fruit juices using crossflow microfiltration

Abstract Microfiltration, using a mineral tubular membrane with nominal pore diameter of 0.2 μm, was applied to six tropical fruit juices (mango, pineapple, naranjilla, Castillas blackberry, passion fruit, tangerine) after partial enzymatic liquefaction. For passion fruit juice, it was found that, when estimating the total costs of producing clarified juice to volumetric reduction ratio (VRR) specifications, a VRR exists at which these costs are minimal. Nevertheless, for juices with a high pulp content, these optimal economic costs are reached at relatively low VRR, inducing a low processing yield and costs that are too high for the expected selling price. For the process to be more efficient, it was found that the retentate must have a commercial value close to that of the original raw juice. The kinetics of liquefying and concentrating the suspended solid (SS) during enzymatic treatment and microfiltration were monitored for all juices tested. It was shown that, by controlling the VRR, increasing the SS content was possible until it reached the same concentration level found in the raw juice. Under these conditions, the retentate is very similar to the initial juice and can be re-introduced into the pulpy juice processing line. This strategy was carried out on the pulpy juices, following a fully continuous processing with constant feeding and removal of retentate so as to keep the SS content constant in the emerging retentate. During these trials, the permeate flux fluctuated around an average value without showing signs of decreasing. Estimated production costs were also much more competitive.

Dynamic modeling of crossflow microfiltration using neural networks

The neural network theory was used to dynamically model membrane fouling for a raw cane sugar syrup feed stream. The use of neural networks enabled us to integrate the effects of hydrodynamic conditions on the time evolution of the total hydraulic resistance of the membrane under constant temperature and feed stream concentration. The results obtained satisfactorily model the effects of both constant and variable transmembrane pressure and crossflow velocity as the filtration was followed through time. The effects of the hidden network structure as well as the scatter of data on the quality of modeling are discussed in this paper.

Crossflow microfiltration of passion fruit juice after partial enzymatic liquefaction

To obtain clarified passion fruit juice, crossflow microfiltration after enzymatic liquefaction was studied using ceramic membranes with 0.2 μm pore size. The effect of a high-rate enzymatic treatment for the degradation of suspended solids was assessed, resulting in the selection of a commercial enzymatic preparation. Partial enzymatic liquefaction of cell-wall polysaccharides prior to microfiltration provided an unusual pattern of flux increase after a short decline when crossflow velocity was high (7 m s−1). It was found that a synergistic effect between pectinase and cellulase activities enhanced permeate flux increase. With total recycling at 36°C, the combination of low transmembrane pressure (150 kPa) and high enzyme concentration (1 ml l−1) provided the highest flux (113 l h−1 m−2). These conditions were then assessed with concentration in order to verify industrial feasibility and evaluate physico-chemical characteristics of final products. A volumetric reduction ratio of 3 was maintained during 18 h without any decrease in permeate flux, which fluctuated around 40 l h−1 m−2. The quality of permeate was satisfying even its aromatic strength was weakened. Retentate had similar characteristics of raw juice and could be recycled in order to use its residual enzyme activity.

Co-immobilized pectinlyase and endocellulase on chitin and Nylon supports

Abstract Some factors influencing easy immobilization procedures on Nylon and chitin supports were optimized in terms of the highest activity of immobilized pectinlyase, using two experimental designs. Optimal procedures were applied to co-immobilized pectinlyase (Pl, EC 4.2.2.3) and endocellulase (Cx, EC 3.2.1.4), using a commercial enzyme but omitting preliminary purification steps. Purified enzyme solutions were not used. The kinetic characteristics of co-immobilized pectinlyase and endocellulase were assessed for both supports. Chitin was more suitable for applications to fruit juice liquefaction because both immobilized pectinlyase and endocellulase showed higher activity at low pH and low temperature. Furthermore, the half-life of pectinlyase bound to chitin was higher than with Nylon (407 h against 19 h). The immobilization procedure on chitin was not only inexpensive, but also very easy to carry out so that the potential for industrial application is considerable.

Treatment of sugar decolorizing resin regeneration waste using nanofiltration

In the sugar industry, ion-exchange resins have a problem with regeneration waste disposal since the regeneration effluent contains a high concentration of sodium chloride and colored organics. In the present work the recovery and recycling of waste brine previously used for decolorizing sugar liquor has been investigated using cost-effective organic spiral-wound nanofiltration membranes. A 74% reduction in salt consumption and an 89% reduction in water consumption were achieved in the batch configuration at VCF 9.

Influence of start-up procedure on crossflow microfiltration of raw cane sugar

Abstract Different start-up procedures have been applied on a crossflow microfiltration plant for the clarification of solutions from raw cane sugar. Compared to the abrupt start-up mode, a progressive setting-up of both transmembrane pressure and crossflow velocity allowed the permeate fluxes to increase significantly without any alteration of the clarifying effect. This result has been proved on three different lots of sugar under different operating conditions.

Optimal control of the microfiltration of sugar product using a controller combining fuzzy and genetic approaches

A SUGENO type fuzzy controller is proposed for the automatic control of the crossflow microfiltration process for raw cane sugar. This process is becoming a field of increasing importance in the food industry. In most cases, and especially for sugar products, widespread applications of crossflow microfiltration is limited by the low permeate fluxes usually obtained. This limitation is linked to the difficulty to reduce the degree of membrane fouling (settling of particles on the membrane), a phenomenon which is dependent on several variables and difficult to control. In the present work, human expertise of the process is used to set up the fuzzy controller. The fuzzy controller is validated through simulations using a neural network model of this process and by real time experimentation on a pilot plant. The results of simulations and pilot tests show that it becomes possible to impose dynamics to the process which permits to maintain the state variable close to a given reference and to limit membrane fouling considerably. An off-line optimization of the fuzzy controller is performed using genetic algorithms. The cost results obtained during a real experiment, after genetic optimization of the fuzzy controller are much better than those obtained previously. Furthermore, the tuning of the controller through optimization is realized under constraints which lead, after optimization, to a heuristic structure completely understandable by microfiltration experts.

Sugar refining process by coupling flocculation and crossflow filtration

Abstract Raw cane sugar solution at 50 brix was purified by combining flocculation with a cationic polymer and crossflow micro/ultrafiltration using tubular mineral membranes of porosities ranging from 0.2 μm to 15 kDa. The pilot tests indicated that the coupling of these two processes led successfully to a permeate decolorization of 50% at a 65 l h −1 m −2 permeate flux with the 300 kDa membrane which was found to be the most promising one. This result is considerably improved compared to the 39% decolorization rate and the 25 l h −1 m −2 flux given by the 15 kDa membrane alone. Ion exchange resin decolorization tests demonstrated the benefit of flocculation and ultrafiltration pretreatments on sugar liquor quality.

Interest of neural networks for the optimization of the crossflow filtration process

In order to build up a model representing the effect of transmembrane pressure and crossflow velocity on crossflow filtration results at quasi-steady state, an approach based on neural networks is proposed. For filtralions of various products (raw cane sugar remelt, natural gum solution) on different membranes (micro- and ultrafiltralion) with or without co-current permeate flow, the modelling of both permeate flux and retention rate could be obtained after only five experimental trials. Compared to more classical modelling techniques, the neural networks were showed to be sometimes better suited and are useful when the effects of hydrodynamical conditions on filtration results are strongly nonlinear. Thanks to established models, it was possible to determine, with a good safety margin, an optimum region in every case studied.