Carmela Conidi

Recovery and concentration of polyphenols from olive mill wastewaters by integrated membrane system.

The purpose of this work was to analyse the potentialities of an integrated membrane system for the recovery, purification and concentration of polyphenols from olive mill wastewater (OMW). The proposed system included some well-known membrane operations such as microfiltration (MF) and nanofiltration (NF), as well as others not yet investigated for this specific application, such as osmotic distillation (OD) and vacuum membrane distillation (VMD). The OMW was directly submitted to a MF operation without preliminary centrifugation. This step allowed to achieve a 91% and 26% reduction of suspended solids and total organic carbon (TOC), respectively. Moreover, 78% of the initial content of polyphenols was recovered in the permeate stream. The MF permeate was then submitted to a NF treatment. Almost all polyphenols were recovered in the produced permeate solution, while TOC was reduced from 15 g/L to 5.6 g/L. A concentrated solution enriched in polyphenols was obtained by treating the NF permeate by OD. In particular, a solution containing about 0.5 g/L of free low molecular weight polyphenols, with hydroxytyrosol representing 56% of the total, was produced by using a calcium chloride dihydrate solution as brine. The obtained solution is of interest for preparing formulations to be used in food, cosmetic and pharmaceutical industry. Besides the OD process, VMD was applied as another way for concentrating the NF permeate and the performance of both processes was compared in terms of evaporation fluxes.

Fractionation of olive mill wastewaters by membrane separation techniques

This study aims to evaluate the potential of an integrated membrane system in the treatment of olive mill wastewaters (OMWs) to produce a purified fraction enriched in low molecular weight polyphenols, a concentrated fraction of organic substances and a water stream which can be reused in the extractive process of olive oil. In particular, a sequence of two ultrafiltration (UF) processes followed by a final nanofiltration (NF) step was investigated on laboratory scale operating in selected process parameters. The produced fractions were analyzed for their total content of polyphenols, total antioxidant activity (TAA), free low molecular weight polyphenols and total organic carbon (TOC). The performance of selected membranes in terms of productivity, fouling index and selectivity toward compounds of interest was also evaluated and discussed. An integrated membrane process was proposed to achieve high levels of purification of OMWs and a water fraction which can be discharged in aquatic systems or to be reused in the olive oil extraction process.

Comparison of the performance of UF membranes in olive mill wastewaters treatment

Olives are known to contain an appreciate amount of phenols with good antioxidant properties which are lost in large part in olive mill wastewaters (OMWs) during olive oil production. Membrane technology offers several advantages (low energy consumption, no additive requirements, no phase change) over traditional techniques to recover phenolic compounds from OMWs. The aim of this work was to evaluate the performance of different UF membranes in the treatment of OMWs finalized to the recovery of polyphenols. For this purpose, OMWs were processed, in selected operating conditions, with four flat-sheet UF membranes characterized by different molecular weight cut-off (MWCO) (4, 5 and 10 kDa) and polymeric material (regenerated cellulose and polyethersulphone). Permeate fluxes, fouling index and retention coefficients towards phenolic compounds, total antioxidant activity (TAA) and total organic carbon (TOC) were evaluated. Regenerated cellulose membranes exhibited lower rejections towards phenolic compounds, higher permeate fluxes and lower fouling index if compared with PES membranes.

Valorization of artichoke wastewaters by integrated membrane process

In this work an integrated membrane system was developed on laboratory scale to fractionate artichoke wastewaters. In particular, a preliminary ultrafiltration (UF) step, based on the use of hollow fibre membranes, was investigated to remove suspended solids from an artichoke extract. The clarified solution was then submitted to a nanofiltration (NF) step. Two different 2.5 × 21 in. spiral-wound membranes (Desal DL and NP030) with different properties were investigated. Both membranes showed a high rejection towards the phenolic compounds analysed (chlorogenic acid, cynarin and apigenin-7-O-glucoside) and, consequently, towards the total antioxidant activity (TAA). On the other hand, the Desal DL membrane was characterized by a high rejection towards sugar compounds (glucose, fructose and sucrose) (100%) when compared with the NP030 membrane (4.02%). The performance of selected membranes in terms of permeate flux, fouling index and water permeability recovery was also evaluated. On the base of experimental results, an integrated membrane process for the fractionation of artichoke wastewaters was proposed. This conceptual process design permitted to obtain different valuable products: a retentate fraction (from the NP030 membrane) enriched in phenolic compounds suitable for nutraceutical, cosmeceutical or food application; a retentate fraction (from the Desal DL membrane), enriched in sugar compounds, of interest for food applications; a clear permeate (from the Desal DL membrane) which can be reused as process water or for membrane cleaning.

A new physical-chemical process for the efficient production of cellulose fibers from Spanish broom (Spartium junceum L.)

A novel and efficient method for the extraction of cellulose fibers from Spanish broom (Spartium junceum L.) is presented. The method is based on the sequential combination between an initial chemical stage (alkaline digestion) and a subsequent physical-chemical stage, consisting of compression with hot air in an autoclave followed by rapid decompression (DiCoDe process, digestion-compression-decompression). The alkaline mother liquor deriving from the initial digestion step can be conveniently recycled after centrifugation followed by ultrafiltration. The process is characterized by the production of fibers with excellent physical-chemical properties, such as high mechanical resistance and high elasticity, and rapid production times. The fibers obtained after the DiCoDe process can be further softened and whitened by means of enzymatic digestion. Fibers were morphologically characterized by scanning electron microscopy (SEM), while their composition and physical-chemical properties were determined by conventional methods, including colorimetry, TAPPI protocols, IR spectroscopy, and X-ray diffractometry.

Recovery of Flavonoids from Orange Press Liquor by an Integrated Membrane Process

Orange press liquor is a by-product generated by the citrus processing industry containing huge amounts of natural phenolic compounds with recognized antioxidant activity. In this work, an integrated membrane process for the recovery of flavonoids from orange press liquors was investigated on a laboratory scale. The liquor was previously clarified by ultrafiltration (UF) in selected operating conditions by using hollow fiber polysulfone membranes. Then, the clarified liquor with a total soluble solids (TSS) content of 10 g·100 g−1 was pre-concentrated by nanofiltration (NF) up to 32 g TSS 100 g−1 by using a polyethersulfone spiral-wound membrane. A final concentration step, up to 47 g TSS 100 g−1, was performed by using an osmotic distillation (OD) apparatus equipped with polypropylene hollow fiber membranes. Suspended solids were completely removed in the UF step producing a clarified liquor containing most part of the flavonoids of the original press liquor due to the low rejection of the UF membrane towards these compounds. Flavanones and anthocyanins were highly rejected by the NF membrane, producing a permeate stream with a TSS content of 4.5 g·100 g−1. An increasing of both the flavanones and anthocyanins concentration was observed in the NF retentate by increasing the volume reduction factor (VRF). The final concentration of flavonoids by OD produced a concentrated solution of interest for nutraceutical and pharmaceutical applications.

A Membrane-Based Process for the Valorization of the Bergamot Juice

An integrated membrane process for the production of highly concentrated bergamot juice was investigated. The depectinized bergamot juice, with an initial total soluble solids (TSS) content of 95 g kg−1 was previously clarified by ultrafiltration (UF) by using polysulphone hollow fibers membranes having a nominal molecular weight cut-off of 100 kDa. The analyses of flux decay, according to fouling models reported in literature, revealed that the resistance of a cake layer covering the entire surface of the UF membrane well describes the fouling phenomenon in the treatment of bergamot juice. The clarified juice was concentrated in an osmotic membrane distillation (OMD) system by using a hollow fiber membrane contactor and calcium chloride dehydrate as extraction brine. In isothermal conditions (25°C) transmembrane vapor water fluxes were between 0.4 and 1.45 kg m−2 h−1 producing a concentrated juice with a final TSS content of 540 g kg−1. Suspended solids were completely removed in the UF process. Flavonoids and ascorbic acid were recovered in the UF permeate and well preserved during the subsequent concentration process. The evaluation of the total antioxidant activity (TAA) in clarified and concentrated samples confirmed the assumption of a mild integrated membrane process able to produce a concentrated juice without modifying the main quality criteria of the fresh juice.

Nanofiltration and Tight Ultrafiltration Membranes for the Recovery of Polyphenols from Agro-Food By-Products

Pressure-driven membrane-based technologies represent a valid approach to reduce the environmental pollution of several agro-food by-products. Recently, in relation to the major interest for natural compounds with biological activities, their use has been also addressed to the recovery, separation and fractionation of phenolic compounds from such by-products. In particular, tight ultrafiltration (UF) and nanolfiltration (NF) membranes have been recognized for their capability to recover phenolic compounds from several types of agro-food by-products. The separation capability of these membranes, as well as their productivity, depends on multiple factors such as membrane material, molecular weight cut-off (MWCO) and operating conditions (e.g., pressure, temperature, feed flow rate, volume reduction factor, etc.). This paper aims at providing a critical overview of the influence of these parameters on the recovery of phenolic compounds from agro-food by-products by using tight UF and NF membranes. The literature data are analyzed and discussed in relation to separation processes, molecule properties, membrane characteristics and other phenomena occurring in the process. Current extraction methodologies of phenolic compounds from raw materials are also introduced in order to drive the implementation of integrated systems for the production of actractive phenolic formulations of potential interest as food antioxidants.

Clarification of Orange Press Liquors by PVDF Hollow Fiber Membranes

Press liquors are typical by-products of the citrus juice processing characterized by a high content of organic compounds and associated problems of environmental impact, which imply high treatment costs. However, these wastes contain a great number of health promoting substances, including fibers, carotenoids and phenolic compounds (mainly flavonoids), whose recovery against waste-destruction technologies is very attractive for new business opportunities. In this work, the clarification of orange press liquor by using microfiltration (MF) membranes is studied as a preliminary step to obtain a permeate stream enriched in antioxidant compounds which can be further processed to produce extracts of nutraceutical and/or pharmaceutical interest. MF poly(vinylidene fluoride) (PVDF) hollow fibers were prepared by the dry/wet spinning technique. A series of fibers was produced from the same polymeric dope, in order to investigate the effect of selected spinning parameters, i.e., bore fluid composition and flowrate, on their properties. The morphology of the produced fibers was analyzed by Scanning Electron Microscopy (SEM). Fibers were further characterized for their mechanical properties, porosity, bubble point, pore size distribution and pure water permeability (PWP). Some of the produced fibers exhibited high permeability (pure water permeability ~530 L/m2·h·bar), coupled to good mechanical resistance and pore size in the range of MF membranes. These fibers were selected and used for the clarification of press liquor from orange peel processing. In optimized operating conditions, the selected fibers produced steady-state fluxes of about 41 L/m2·h with rejections towards polyphenols and total antioxidant activity of 4.1% and 1.4%, respectively.

Membrane-based technologies for meeting the recovery of biologically active compounds from foods and their by-products

ABSTRACT To date, according to the latest literature inputs, membranes-based technologies (microfiltration, ultrafiltration and nanofiltration) have demonstrated to meet the recovery of biologically active compounds, mainly phenolic compounds and their derivatives, from agro-food products and by-products. The goal of this paper is to provide a critical overview of the on ongoing development works aimed at improving the separation, fractionation and concentration of phenolic compounds and their derivatives from their original sources. The literature data are analyzed and discussed in relation to separation processes, molecule properties, membrane characteristics and key factors affecting the performance of such technologies. Technological advances and improvements over conventional technologies, as well as critical aspects to be further investigated are highlighted and discussed. Finally, a critical outlook about the current status for a large-scale application and the role of these processes from an environmental viewpoint is provided.