Max Reynes

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.

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.

Comparison of different methods for deacidification of clarified passion fruit juice

Abstract The high acidity of passion fruit limits its addition in food preparation. In order to easy the uses of this juice to formulate high aroma and flavour products, its citric acid content must be decreased. Various methods such as calcium salts precipitation, ion-exchange resins and electrodialysis with homopolar and bipolar membranes were investigated to increase the pH of a clarified passion fruit juice from 2.9 to 4.0. Each deacidification process was compared in terms of characteristics of deacidified juices such as concentration of inorganic and organic ions, colour and flavour. The deacidification by precipitation using CaCO 3 was not recommended because of CO 2 release. The ion-exchange process gave a poor quality juice in terms of organoleptic characteristics. Electrodialysis with homopolar membranes induced an increase in the sodium concentration. Precipitation with Ca(OH) 2 and electrodialysis with bipolar membrane were the most suitable processes in terms of sensorial properties of juices treated. The physico-chemical analyses showed an increase in the calcium concentration with the use of Ca(OH) 2 that could cause some precipitation problems in the final product. Inorganic anions were eliminated together with citrate by using electrodialysis and resins. Nevertheless, electrodialysis with bipolar membranes presented great advantages: it was a continuous process without reagent addition moreover allowing the production of a valuable solution of citric acid.

Differentiation between Cooking Bananas and Dessert Bananas. 1. Morphological and Compositional Characterization of Cultivated Colombian Musaceae (Musa sp.) in Relation to Consumer Preferences

The morphological, physical, and chemical characteristics of 23 unripe cultivated varieties of Colombian Musaceae were assessed. Fresh pulp dry matter helped to discriminate the following consumption subgroups: FHIA dessert hybrids (hydes: 24.6%) < dessert bananas (des: 29.4%) < nonplantain cooking bananas (cook: 32.0%) < FHIA cooking hybrids (hycook: 34.2%) < plantains (pl: 41.1%). Banana flour starch content on dry basis (db) varied from 74.2 to 88.2% among the varieties, with: pl: 86.5% > cook and hycook: 84% > des: 81.9% > hydes: 79.7% (p <or= 0.01). Flour pH varied in the range 4.8 to 6.2, with the highest pH for the plantain subgroup (5.6), which also had lower titratable acidity than those of the cooking banana and FHIA groups with 7.9, 13.6, and 15.6 mEq H(+)/100 g db, respectively (p <or= 0.05). pl and hycook presented the highest glucose and fructose contents at 0.8% and 1.5% (p <or= 0.05). No significant differences were observed between the groups in proteins (3.2%), total soluble sugars (1.7%), and crude fibers (3%). pl had lower ash, calcium, and magnesium contents (2.7%; 8.4 and 90.7 mg/100 g db) than des (3.2%; 9.3 and 117.9 mg/100 g db) and hydes (3.9%; 23.7 and 125 mg/100 g db) (p <or= 0.05). pl and des had significantly lower peel percentages (38%) than the other subgroups (42-45%). The principal components analysis (PCA) highlights the strong relationship between some of the varietal characteristics and the consumption pattern, which is especially marked for the plantain subgroup in relation to stakeholder and the consumer preferences.

Evaluating transfers of aroma compounds during the concentration of sucrose solutions by osmotic distillation in a batch-type pilot plant

The transfer of volatiles was studied during the batch concentration of a sucrose solution by osmotic distillation in a semi-industrial pilot plant. The transfer kinetics of four aroma compounds from fruits were measured by gas chromatography. Although significant adsorption phenomena on the membrane were notable; these can easily be limited by saturating the installation before concentration. A simple model, based on the definition of the apparent permeability, was developed to characterize transfer kinetics. Losses in volatiles during concentration are directly linked to the relative value of this permeability, compared with water flux. Decreasing circulation velocity and temperature of the solution to be concentrated slowed the transfer of aroma compounds down considerably. Limiting losses of volatiles by acting on operating conditions is thus possible. Compared with the classic evaporation process, osmotic distillation induces smaller losses in aroma compounds.

The problem of membrane characterization for the process of osmotic distillation

Abstract The membrane used in the process of osmotic distillation (OD) is often considered passive as it simply provides a support for the vapour—liquid interfaces where evaporation and condensation take place and does not introduce any selectivity. However, the membrane is a major component of the system, not only because it constitutes one of the resistances to mass transfer but also because the non-wettability of this component conditions the viability of the process. The mass transfer as well as the non-wetting condition depend on the membrane structure, but the conventional characterization methods do not always provide adequate information. In this paper, scanning electronic microscopy, mercury porosimetry and contact angle measurements were used to observe the porous structure and to characterize the hydrophobicity of two commercial membranes. The two first methods gave access to the structural parameters of each individual layer of the composite material. The membrane thickness, volume porosity and pore diameters appeared to be quite different from the values specified by the manufacturer that are obviously referring to a microfiltration application. These results allowed understanding the membranes contribution to the mass transfer resistance in the process. The contact angle theory originally designed for smooth ideal surfaces did not provide a satisfactory representation of the wetting behaviour of porous membranes. The wettability of such materials has to be characterized experimentally under the operating process conditions. The results of this study emphasize the lack of appropriate physical methods specifically designed to characterize the microfiltration membranes employed for OD applications.

Differentiation between Cooking Bananas and Dessert Bananas. 2. Thermal and Functional Characterization of Cultivated Colombian Musaceae (Musa sp.)

The starch and flour thermal and functional characteristics of 23 cultivated varieties of bananas in Colombia were assessed. Onset temperature for gelatinization of starches measured by differential scanning calorimetry (DSC) varied from 59.7 to 67.8 degrees C, thereby significantly differentiating dessert bananas (63.2 degrees C) from nonplantain cooking bananas (65.7 degrees C) from FHIA hybrids (66.6 degrees C) and plantains (67.1 degrees C). FHIA hybrids are significantly discriminated from dessert banana landraces but not from the cooking group. The starch amylose contents varied from 15.4 to 24.9%; most dessert banana starch amylose contents were below 19%, whereas in cooking banana starches the contents were over 21%. Flour functional properties were assessed by Rapid ViscoAnalyser (RVA) using silver nitrate as alpha-amylase inhibitor. The flour pasting temperature was relevant to differentiate dessert bananas (69.5 degrees C) from FHIA dessert hybrids and nonplantain cooking bananas (72.8 degrees C) from cooking hybrids and plantains (75.8 degrees C). Among other criteria, the cooking ability also helped to differentiate dessert bananas and FHIA hybrids from cooking bananas. A close relation between cultivar genotypes and uses with the thermal and pasting properties were revealed.

Evolution of aroma compounds from orange juice stored in polyethylene terephthalate (PET)

The evolution of aroma compounds from orange juice made from concentrate and stored in glass, standard monolayer polyethylene terephthalate (PET 1), multilayer PET (PET 2) and plasma-treated PET (internal carbon coating) (PET 3) was investigated. Bottles were stored at room temperature (20°C) under artificial light. Volatile compounds in orange juice samples and corresponding packaging materials were analysed at zero time and after 2, 3 and 5 months of storage. After 5 months of storage, from 0.2 to 0.3% of the initial amounts of limonene and β-myrcene in the orange juice had been absorbed by the plastic packaging materials. Statistical analyses showed that the evolution of aroma compounds was strongly correlated to the duration of storage, but not to the type of packaging material. Indeed, whatever the stored orange juice samples, the same evolutions were observed, with a decrease in aldehydes and ketones, esters, aliphatic alcohols, sesquiterpene and monoterpene alcohols, and an increase in two aliphatic and monoterpene alcohols (i.e. furfural and 4-vinylguaicol). The results suggest that the losses of aroma compounds from the juice could be attributed to the high acidity of the matrix, implying acid-catalysed reactions. Finally, PET packaging materials and their corresponding oxygen permeabilities showed no correlation with the loss of aroma compounds.