Application of Design of Experiments to the Analysis of Fruit Juice Deacidification Using Electrodialysis with Monopolar Membranes

Abstract

Despite the beneficial health effects of fruit juices, the high content of organic acids and low pH of some of them limit their consumption. The aim of this work was to study the deacidification of fruit juices using electrodialysis (ED) with monopolar membranes. Aqueous solutions of citric acid were used in ED deacidification experiments following a factorial design with citric acid concentration and electric current varying in the ranges of 5–25 g/L and 0.5–1 A, respectively. The design runs were characterized by a constant Faraday efficiency of 0.37 ± 0.03, suggesting that the triple-charged citrate ion (Cit3−) carried the electric charge through the anionic membranes. During deacidification, the pH increased in agreement with the decreasing concentration of the acid. Deacidification of pineapple juice or pineapple juice enriched with 20 g/L of citric acid using ED led to similar values of the Faraday efficiency, confirming that Cit3− is the main ion migrating through the anionic membrane. However, the decrease in titratable acidity during ED treatment was accompanied by a decrease in pH. Such behavior, already reported, was explained by considering proton generation during the transformation of the single (H2Cit−) and double-charged (HCit2−) citrate ions into the triple-charged ion (Cit3−) when entering the anionic membrane.

Phosphates Transfer in Pristine and Modified CJMA-2 Membrane during Electrodialysis Processing of NaxH(3−x)PO4 Solutions with pH from 4.5 to 9.9

“…The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/membranes13070647/s1, Figure S1: SEM images of (a) surfaces and cross-section of the heterogeneous MC-40 membrane (b). The heterogeneous membrane MA-41 has a structure similar to that of MC-40; Figure S2: The distribution of species of the orthophosphoric acid (in mole fractions) vs. the pH of the solution; Figure S3: Cross-section of the ion exchange membrane volume in the framework of microheterogeneous model; Figure S4: Schematic of the unit for measuring the diffusion permeability of membranes: (1) two-compartment cell, (2) membrane under study, (3,4) flow-through compartments of cell 1, (5) tank with distilled water, (6) tank with an electrolyte solution of the set concentration, (7) pumps, (8) conductometer, (9) immersion conductometric cell, (10-13) connecting hoses, ( 14) pH meter, and (15) combined glass electrode for pH measurements; Figure S5: Schematic design of the experimental setup (a) and plexiglass frames with special comb-shaped guides that separate the membranes (b): a flow-through four-compartment electrodialysis cell containing an anion-exchange membrane under study (AEM*) and two auxiliary membranes, an anion-exchange and a cation-exchange membranes; tank with 0.02 M electrolyte solutions (1); additional tank (2) for determination of ion transport numbers; valves (3,4); the Luggin capillaries (5); Ag/AgCl electrodes (6); platinum polarizing the working and counter electrodes (7); Autolab PGSTAT100N (8); flow-through cell with a pH combination electrode (9); pH meter pHM120 MeterLab (10) connected to computer; pH meter (10); combined electrode for pH measurements (11) connected to pH meter (10); conductivity cell (12) connected to a conductometer; titration device (13) for maintaining a constant pH in the solution circulating through tank (2); desalination compartment (14); the solid purple lines show schematic concentration profiles in two neighboring compartments separated by the membrane under study; Figure S6 S1: The values of pK a (at 25 • C) of the orthophosphoric acid various species, which may be present in the membrane systems under study; Table S2: The rate constants of proton-transfer reactions (5)- (10) for the weak acids under study; Table S3: Some of the characteri...…”

“…Already, these membrane technologies are promising for the processing of fermentation broths or waste fermentation effluent [ 1 , 2 , 3 , 4 ], agricultural, industrial streams and natural waters [ 5 , 6 , 7 , 8 , 9 ], the selective separation of various acids [ 10 ]; tartrate stabilization of wine; demineralization of milk whey; reagent-free correction of the pH of juices and wines [ 11 ], or conversion of salts to polybasic acids and vice versa [ 12 , 13 ]. Citrates [ 2 , 11 , 14 , 15 ], malates [ 10 , 14 ], tartrates [ 13 ], oxalates [ 7 ], chromates [ 16 , 17 ], vanadates [ 18 ], and sulfates [ 19 ] are the most common objects of the application of processes in which ion-exchange membranes are involved. Phosphates are of particular interest, which is accompanied by an avalanche-like increase in scientific publications in recent years ( Figure 1 ).…”

“…This feature distinguishes polybasic acid anion transport in AEM systems from the well-studied transport of Cl − and similar anions. For example, the implementation of the “acid dissociation” mechanism causes an increase in the electric charge of the polybasic acid anion (proton-containing phosphate) after its entry into AEM [ 11 , 31 ]. In addition, the generation of protons takes place in both underlimiting and overlimiting current modes.…”

“…Membrane bioreactors and modules for dialysis, electrodialysis (ED), and capacitive deionization contain these membranes. Already, these membrane technologies are promising for the processing of fermentation broths or waste fermentation effluent [1][2][3][4], agricultural, industrial streams and natural waters [5][6][7][8][9], the selective separation of various acids [10]; tartrate stabilization of wine; demineralization of milk whey; reagent-free correction of the pH of juices and wines [11], or conversion of salts to polybasic acids and vice versa [12,13].…”

“…Citrates [2,11,14,15], malates [10,14], tartrates [13], oxalates [7], chromates [16,17], vanadates [18], and sulfates [19] are the most common objects of the application of processes in which ion-exchange membranes are involved. Phosphates are of particular interest, which is accompanied by an avalanche-like increase in scientific publications in recent years (Figure 1).…”