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.     

Preparation of galacto-oligosaccharides using membrane reactor

Galacto-oligosaccharides (GOS) have many biological functions. They are produced from lactose by a glycosyl transfer of one or more d-galactosyl units onto the d-galactose moiety of lactose catalysed by β-galactosidase. This reaction can proceed in batch or in continuous system. Membrane reactor with ultrafiltration ceramic membrane (150 kDa) was used and batch system as well. Lactose in phosphate buffer (197.9 g L⁻¹), recombined whey (197 g L⁻¹) and evaporated ultrafiltration permeate (200.7 g L⁻¹) were used as substrates. The used concentration of enzyme Maxilact LX 5000 was 6 U mL⁻¹. The highest concentration of GOS in buffer was reached after 30 min of batch reaction and it was 25.5 g L⁻¹, for recombined whey it was 31.1 g L⁻¹ and for ultrafiltration permeate it was 32.9 g L⁻¹. For continuous process was obtained 8.8 g L⁻¹ of GOS for buffer and 21.0 g L⁻¹ for recombined whey and 16.7 g L⁻¹ of GOS for ultrafiltration permeate.     

Identification of optimal membrane morphological parameters during microfiltration of mosambi juice using low cost ceramic membranes

In this work, experimental investigations were carried out for the identification of optimal membrane morphological parameters (pore size distribution, average pore size and porosity) during microfiltration (MF) of mosambi juice using low cost ceramic membranes. Four different low cost ceramic membranes with different pore diameters (d_m) and porosities (?) were subjected to MF studies to evaluate the effect of d_m and ? on permeation characteristics (permeate flux and juice quality) of centrifuged mosambi juice (CJ) and enzyme treated centrifuged mosambi juice (ETCJ). Subsequently, a convenient factor namely effective permeable area factor (?_md_m²) was evaluated to provide greater insights in the fouling phenomena. Various physio-chemical properties such as colour, clarity, pH, citric acid content, density, total soluble solid (TSS) and alcohol insoluble solids (AIS) were measured for both feed and permeate juice samples to evaluate the effect of ?_md_m² on juice quality. Typical permeate fluxes were observed to vary from 5.78 × 10⁻⁶ to 13.45 × 10⁻⁶ m³/m² s for CJ and 14.07 × 10⁻⁶ to 60.64 × 10⁻⁶ m³/m² s for ETCJ at 82.7 kPa (ΔP) for different membranes whose ?_md_m² varied from 0.249 to 0.783 μm². Among different membrane pore blocking models, flux decline by cake filtration was found to be the best fitted model. The cake filtration model constant (k_c) was found to vary with ΔP and ?_md_m² and was empirically correlated. Phenomenological models were proposed to illustrate the dependency of total hydraulic resistance of membrane on ?_md_m², ΔP and time (t). Based on experimental as well as theoretical investigations, membranes with ?_md_m² up to 0.443 μm² for CJ and 0.294 μm² for ETCJ and a ΔP of 82.7 kPa were recommended for MF of mosambi juice.     

Crossflow microfiltration for the cold stabilization of roselle (Hibiscus sabdariffa L.) extract

In this study, roselle extract was cold sterilized by crossflow microfiltration. At laboratory scale the optimal operating conditions at volumetric reduction ratio (VRR) 1 cannot be generalized when VRR is greater than 1. Indeed, at VRR 1 the optimal transmembrane pressure was 2.5 bar with a permeate flux of 185 L h⁻¹ m⁻², while at VRR 20 optimal pressure was 3.7 bar with a permeate flux of 95 L h⁻¹ m⁻². A simple model that allowed to represent the effect of VRR and transmembrane pressure on the permeate flux was adjusted with the experiments done at laboratory scale. This model used to predict the permeate flux using a semi-industrial pilot scale equipment gave a good match between the experimental and calculated performances. Permeate was collected aseptically and stored at 4, 20 and 37 °C for 90 days. A roselle extract storage at 4 and 20 °C was appropriate for consumption after a 3 month shelf life.     

Chicory juice clarification by membrane filtration using rotating disk module

Clarification is the first step of inulin production from chicory juice, and membrane filtration as an alternative can greatly simplify this process, increase juice yield, improve product quality, and reduce the cost and waste volume. In this study, a rotating disk module (RDM) was used to investigate the clarification of chicory juice by four micro- and ultrafiltration membranes. Compared with dead end filtration, the RDM had a much higher permeate flux and product quality. High rotating speeds produced high permeate fluxes and reduced flux decline, because of the strong back transport of foulant from fouling layer to feed solution. At high rotating speeds of 1500–2000 rpm, the permeate flux increased with membrane pore size and transmembrane pressure (TMP), while at low rotating speeds (<1000 rpm), permeate flux was independent of membrane type and TMP due to a thick deposited fouling layer as a dominant filtration resistance, while carbohydrate transmission decreased at higher TMP because of denser cake layer as an additional selective membrane. The highest carbohydrate transmission (∼98%) and desirable permeate turbidity (2.4 NTU) was obtained at a TMP of 75 kPa and a rotating speed of 2000 rpm for FSM0.45PP membrane. With the RDM, the Volume Reduction Ratio (VRR) could reach 10 with a high permeate flux (106 L m⁻² h⁻¹) in the concentration test, and permeate was still rich in carbohydrate and well clarified. Chemical cleaning with 0.5% P3-ultrasil 10 detergent solution was able to recover 90% water flux of fouled membrane.     

Interaction of milk α- and β-caseins with tea polyphenols

The interaction of α- and β-caseins with tea polyphenols (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) was examined at a molecular level, using FTIR, UV–visible, CD and fluorescence spectroscopic methods as well as molecular modelling. The polyphenol binding mode, the binding constant and the effects of polyphenol complexation on casein stability and conformation were determined. Structural analysis showed that polyphenols bind casein via both hydrophilic and hydrophobic interactions with overall binding constants of K_C–α-cas = 1.8 (±0.8) × 10³ M⁻¹, K_EC–α-cas = 1.8 (±0.6) × 10³ M⁻¹, K_EGC–α-cas = 2.4 (±1.1) × 10³ M⁻¹ and K_{EGCG–α-cas} = 7.4 (±0.4) × 10³ M⁻¹, K_C–β-cas = 2.9 (±0.3) × 10³ M⁻¹, K_EC–β-cas = 2.5 (±0.6) × 10³ M⁻¹, K_EGC–β-cas = 3.5 (±0.7) × 10³ M⁻¹ and K_{EGCG–β-cas} = 1.59 (±0.2) × 10⁴ M⁻¹. The number of polyphenol bound per protein molecule (n) was 1.1 (C), 0.9 (EC), 1.1 (EGC), 1.5 (EGCG) for α-casien and 1.0 (C), 1.0 (EC), 1.1 (EGC) and 1.5 (EGCG) for β-casein. Structural modelling showed the participation of several amino acid residues in polyphenol–protein complexation with extended H-bonding network. Casein conformation was altered by polyphenol with a major reduction of α-helix and β-sheet and increase of random coil and turn structure suggesting further protein unfolding. These data can be used to explain the mechanism by which the antioxidant activity of tea compounds is affected by the addition of milk.     

Milk β-lactoglobulin complexes with tea polyphenols

The effect of milk on the antioxidant capacity of tea polyphenols is not fully understood. The complexation of tea polyphenols with milk proteins can alter the antioxidant activity of tea compounds and the protein secondary structure. This study was designed to examine the interaction of β-lactogolobulin (β-LG) with tea polyphenols (+)-catechin (C), (−)-epicatechin (EC), (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG) at molecular level, using FTIR, CD and fluorescence spectroscopic methods as well as molecular modelling. The polyphenol binding mode, the binding constant and the effects of polyphenol complexation on β-LG stability and secondary structure were determined. Structural analysis showed that polyphenols bind β-LG via both hydrophilic and hydrophobic interactions with overall binding constants of K_C–β-LG = 2.2 (±0.8) × 10³ M⁻¹, K_EC–β-LG = 3.2 (±1) × 10³ M⁻¹, K_ECG–β-LG = 1.1 (±0.6) × 10⁴ M⁻¹ and K_EGCG–β-LG = 1.3 (±0.8) × 10⁴ M⁻¹. The number of polyphenols bound per protein molecule (n) was 1.1 (C), 0.9 (EC), 0.9 (ECG) and 1.3 (EGCG). Molecular modelling showed the participation of several amino acid residues in polyphenol–protein complexation with extended H-bonding network. The β-LG conformation was altered in the presence of polyphenols with an increase in β-sheet and α-helix suggesting protein structural stabilisation. These data can be used to explain the mechanism by which the antioxidant activity of tea compounds is affected by the addition of milk.     

Microfiltration and Reverse Osmosis Affect Recovery of Mango Puree Flavor Compounds

Flavor compounds from ripe mango puree were studied upon cross-flow microfiltration on microporous alumina membrane and subsequent concentration of the permeate by reverse osmosis. Terpene hydrocarbons, the major (?98%) volatiles of the puree, were qualitatively and quantitatively recovered in the pulpy microfiltration retentate. The more polar volatiles (?2%) were diversely affected. Most of the oxygenated terpene derivatives were also retained in the microfiltration retentate. C₁₃ norisoprenoids and phenols increased, likely by chemical degradation of carotenoids and phenolic acids, respectively.     

Structural characterization of water-soluble polysaccharides from Opuntia monacantha cladodes in relation to their anti-glycated activities

An aqueous extract of polysaccharides from Opuntia monacantha cladodes (POMC) was preliminarily purified by 5 kDa molecular weight cut-off ultrafiltration membrane to remove impurities with low molecular weight. Then the retentate was fractionated by ethanol solution and chromatographed on a DEAE Sepharose Fast Flow anion-exchange column to yield a major fraction (POMC IV) which was eluted by 0.5 M NaCl. POMC IV was subjected to further purification on a Sephadex G-50 gel filtration column. Two major fractions, POMC V and VI, were collected. By analyses using gel permeation chromatography (GPC), high-performance liquid chromatography (HPLC) and gas chromatography (GC), POMC V, which had a molecular weight of 28.7 kDa, was comprised mainly of rhamnose, arabinose and glucose in the molar ratio of 9.15:1.00:6.84, with 3.07% (w/w) of glucuronic acid, while POMC VI, which had a molecular weight of 10.8 kDa, was comprised mainly of rhamnose, mannose and glucose in the molar ratio of 8.72:1.00:6.19, with 4.68% (w/w) of glucuronic acid. Six distinct-absorbance peaks, at 1742, 1633 and 1417 cm⁻¹ in the infrared (IR) spectra of POMC V, and at 1729, 1596 and 1407 cm⁻¹ in the IR spectra of POMC VI, resulted from the presence of uronic acids. The peaks at 1043 and 890 cm⁻¹ were characteristic of rhamonse and β-d-glucose, respectively. From the profiles of ¹³C and ¹H nuclear magnetic-resonance (NMR) spectra, the main (1 → 2)-α-l-rhamnopyranose units were obviously characterized by six strong signals at 99.24 (C-1), 77.52 (C-2), 70.19 (C-3), 71.33 (C-4), 69.81 (C-5) and 17.45 ppm (C-6). The signal at 175.92 ppm was due to C-6 of β-d-glucuronic acid units. The ¹H spectrum signal at 1.20 ppm was assigned to the CH₃ of α-l-rhamnopyranose units. The evaluation of anti-glycation activity suggested that POMC had good potential for inhibiting the formation of advanced glycation endproducts. Time- and dose-dependent effects were also observed for all POMC samples.     

Binding of vitamin A with milk α- and β-caseins

The binding sites of retinol and retinoic acid with milk α- and β-caseins were determined, using constant protein concentration and various retinoid contents. FTIR, UV–visible and fluorescence spectroscopic methods as well as molecular modelling were used to analyse retinol and retinoic acid binding sites, the binding constant and the effect of retinoid complexation on the stability and conformation of caseins. Structural analysis showed that retinoids bind caseins via both hydrophilic and hydrophobic contacts with overall binding constants of K_{retinol-α-caseins} = 1.21 (±0.4) × 10⁵ M⁻¹ and K_{retinol-β-caseins} = 1.11 (±0.5) × 10⁵ M⁻¹ and K_{retinoic acid-α-caseins} = 6.2 (±0.6) × 10⁴ M⁻¹ and K_{retinoic acid-β-caseins} = 6.3 (±0.6) × 10⁴ M⁻¹. The number of bound retinol molecules per protein (n) was 1.5 (±0.1) for α-casein and 1.0 (±0.1) for β-casein, while 1 molecule of retinoic acid was bound in the α- and β-casein complexes. Molecular modelling showed different binding sites for retinol and retinoic acid on α- and β-caseins with more stable complexes formed with α-casein. Retinoid–casein complexation induced minor alterations of protein conformation. Caseins might act as carriers for transportation of retinoids to target molecules.     

Antioxidant properties of hot water extracts from Agrocybe cylindracea

Agrocybe cylindracea (DC: Fr.) Mre. was available in the form of fruit bodies, mycelia and fermentation filtrate. From these three forms, hot-water extracts were prepared and their antioxidant properties were studied. Antioxidant activities of hot-water extracts from fruit bodies, mycelia and filtrate were 63.6%, 81.6% and 56.8% at 20 mg ml⁻¹, respectively. EC₅₀ values in reducing power were 2.72, 3.97 and 3.09 mg ml⁻¹ whereas those in scavenging abilities of 1,1-diphenyl-2-picrylhydrazyl radicals were 0.62, 1.66 and 0.82 mg ml⁻¹ for fruit bodies, mycelia and filtrate, respectively. At 20 mg ml⁻¹, the scavenging abilities of hydroxyl radicals were 80.1%, 57.0% and 54.3% for fruit bodies, mycelia and filtrate, respectively. With regard to EC₅₀ values in chelating abilities on ferrous ions, the hot-water extract from filtrate was better than that from mycelia. Total phenols were the major naturally occurring antioxidant components found in hot-water extracts and in the range of 23.74–30.16 mg g⁻¹. From EC₅₀ values obtained, it can be concluded that hot-water extracts from three forms of A. cylindracea were good in antioxidant properties.     

The effect of pre-treatment on the anthocyanin and flavonol content of black currant juice (Ribes nigrum L.) in concentration by reverse osmosis

Reverse osmosis process for the concentration of black currant juice was carried using AFC-99 tubular membrane at 30 °C and 45 bar. The contents of selected flavonols and anthocyanins were analyzed after centrifugation; enzyme treatment by Panzym Super E and by Rohapect berry followed by centrifugation; and ultrafiltration black currant juices and juice concentrates. The total soluble solid (TSS) content of the juices increased from the initial 17.6–17.9 °Brix to 24–24.8 °Brix in the case of the centrifuged juice in the concentration process. Similarly, it increased from 14.5–15.5 °Brix to 23.1–23.4 °Brix for the Panzym Super E treated juice, and from 16.1–16.9 °Brix to 22.5–23.1 °Brix for the Rohapect berry treated black currant juices. The ultrafiltered juice had the lowest initial TSS content between 14.1 and 14.9 °Brix and it increased to 22.1–23.1 °Brix. The average permeate fluxes during the concentration process were 7.3 L m⁻² h⁻¹ for the centrifuged juice, 11.9 L m⁻² h⁻¹ for the Panzym Super E treated juice, 9.2 and 13.1 L m⁻² h⁻¹ for the Rohapect berry treated and ultrafiltered juice, respectively. Analysis indicated that the enzymatic treatment resulted in the increase of anthocyanin and flavonol content of the juices. The centrifugation process decreased the amount of anthocyanins and flavonols to some extent. The juice clarified by ultrafiltration had significantly lower concentrations of anthocyanins and flavonols, while the juices treated by Panzym Super E had the highest levels of these flavonoids. This study recommends enzymatic pre-treatment by Panzym Super E, since it improves the permeate flux in reverse osmosis during the concentration process, and results in a juice concentrates highest in anthocyanins and flavonols.     

An approximate shelf life prediction of elaborated lager beer in terms of degradation of its iso-α-acids

A 3-l laboratory-scale beer production protocol was designed and developed to produce beer. Concentrations of cis-/trans-iso-α-acids were quantified by HPLC. The trans-/cis-ratio varied from 0.62 to 0.49 after accelerated aging from 4 °C to 50 °C. The degradation of trans-iso-α-acids in elaborated pale lager beers followed first order reaction and this degradation conforms to the Arrhenius equation. The activation energy (E_a) and frequency factor (A) for trans-iso-α-acids in elaborated pale lager beer ranged from 69.2 kJ mol⁻¹ and 1.88 × 10¹⁰ days⁻¹ for trans-isocohumulone to 74.4 kJ mol⁻¹ and 1.3642 × 10¹¹ days⁻¹ for trans-isoadhumulone. The higher value of E_a demonstrated greater temperature sensitivity of trans-iso-α-acids during accelerated storage. The average half life of trans-iso-α-acids in elaborated pale lager beer was found to decrease from 471 days to 12 days when temperature increased from 4 °C to 40 °C. Using the activation energy of trans-α-acid degradation and the temperature profile of the accelerated aging, a mathematical model was employed to predict the loss of iso-α-acids, when the initial concentration of iso-α-acids in the product is known. The results obtained in the investigation can be of great importance to the industry in predicting the alteration of beer bitterness during warm periods and in tropical countries where summer temperature can reach 40 °C.     

Antioxidant properties of papain hydrolysates of wheat gluten in different oxidation systems

Enzymatic hydrolysis was used for preparing hydrolysates from wheat gluten which is by-product during production of wheat starch. The enzyme used for the hydrolysis was papain. The hydrolysate was separated based on the molecular weight of the peptides by membrane ultrafiltration (UF) with a molecular weight cut-off of 5 kDa into permeate (P) and retentate (5-K) fractions. The antioxidative activities of the hydrolysate and its UF fractions were investigated by using the TBA method and scavenging effect of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The three fractions showed strong antioxidative activities in the linoleic acid oxidation system, and exhibited DPPH radical scavenging activity. The antioxidative activity of the P fraction was almost the same as that of vitamin E at pH 7.0. The molecular weight distribution of the P fraction was concentrated in 4.2 kDa (86.5%) after gel permeation chromatography fractionation using an HPLC system.The P and 5-K fractions had higher surface hydrophobicities (H₀) at pH7.0 compared with the hydrolysate. The resulting UF fractions were superior to the hydrolysate in terms of antioxidative activities.     

Evaluation of commercially available, wide-pore ultrafiltration membranes for production of α-lactalbumin-enriched whey protein concentrate

Commercially available, wide-pore ultrafiltration membranes were evaluated for production of α-lactalbumin (α-LA)-enriched whey protein concentrate (WPC). In this study microfiltration was used to produce a prepurified feed that was devoid of casein fines, lipid materials, and aggregated proteins. This prepurified feed was subsequently subjected to a wide-pore ultrafiltration process that produced an α-LA-enriched fraction in the permeate. We evaluated the performance of 3 membrane types and a range of transmembrane pressures. We determined that the optimal process used a polyvinylidene fluoride membrane (molecular weight cut-off of 50 kDa) operated at transmembrane pressure (TMP) of 207 kPa. This membrane type and operating pressure resulted in α-LA purity of 0.63, α-LA:β-LG ratio of 1.41, α-LA yield of 21.27%, and overall flux of 49.46 L/m²·h. The manufacturing cost of the process for a hypothetical plant indicated that α-LA-enriched WPC 80 (i.e., with 80% protein) could be produced at $17.92/kg when the price of whey was considered as an input cost. This price came down to $16.46/kg when the price of whey was not considered as an input cost. The results of this study indicate that production of a commercially viable α-LA-enriched WPC is possible and the process developed can be used to meet worldwide demand for α-LA-enriched whey protein.     

Anti-oxidative characterisation of NaN3-induced common bean mutants

The contents of total phenolics, total anthocyanins, total proanthocyanidins and antioxidant activities were measured using 2,2-diphenyl-1-picrylhydrazyl radicals scavenging activity, ferric reducing antioxidant power, lipid peroxidation inhibition ability and ABTS⁻ radical-scavenging activity assays. These were compared in the seed coats of common bean (Phaseolus vulgaris L.) cultivar Hwachia and its eighteen NaN₃-induced mutants. NaN₃-induced mutants generally accumulated more total phenolics (19% more), total anthocyanins (65% more) and total proanthocyanidins (4% more) than Hwachia (containing 29.94 mg g⁻¹ total phenolics, 0.31 mg g⁻¹ total anthocyanins and 12.94 mg g⁻¹ total proanthocyanidins, respectively). Anthocyanidins including delphinine, cyanidin and pelargonidin were detectable in seed coat, each with different levels depending on the tested accessions. Significant correlations (average of 0.847 across all comparisons, p < 0.01) were found between the tested antioxidant activities, total phenolics, total anthocyanins and total proanthocyanidins. Mutants SA-11-2, SA-13-2 and SA-34-2 that are enriched with antioxidants may be useful in food and other applications.     

Antioxidant and antiacetylcholinesterase activities of five plants used as Portuguese food spices

In the present work, we report the results of a study aimed at evaluating the antiradical activity, the antioxidant activity and the acetylcholinesterase (E.C. 3.1.1.7.) inhibitory capacity of essential oils, ethanol and boiling water extracts from five aromatic herbs growing wild in Portugal and used in traditional food preparations: fennel (Foeniculum vulgare), mint (Mentha spicata), pennyroyal (Mentha pulegium), rosemary (Rosmarinus officinalis) and wild thyme (Thymus serpyllum). The water extracts of M. spicata and M. pulegium showed the highest radical-scavenging activity (DPPH test) values (IC₅₀ = 5.7 ± 0.4 and 8.9 ± 0.2 μg ml⁻¹ respectively). This activity was higher than that found with the standard antioxidant BHT. The ethanol extracts of M. spicata, T. serpyllum and F. vulgare showed the highest antioxidant activities measured by the β-carotene/linoleic acid assay, IC₅₀ = 36.9 ± 0.1, 41.2 ± 0.1 and 68.7 ± 0.1 μg ml⁻¹, respectively. The inhibition of AChE was higher in the essential oil fraction. The highest activity was found for R. officinalis with an IC₅₀ = 69.8 ± 0.1 μg ml⁻¹.     

Potential use of antioxidative mungbean protein hydrolysate as an anticancer asiatic acid carrier

This study investigated the potential use of mungbean (Vigna radiata (L.) Wilczek) protein hydrolysate (MPH) prepared from tryptic hydrolysis as an antioxidative hydrolysate and as a carrier for anticancer asiatic acid (AA). The antioxidant capacity of MPH was 0.67 and 0.46 ??mol Trolox equivalent (TE)/mg protein, as measured by oxygen radical absorbance capacity-fluorescein (ORAC_FL) and Trolox equivalent antioxidant capacity (TEAC) assays, respectively. Freeze-drying in lactose excipient reduced the antioxidant capacity of MPH to 0.48 ??mol TE/mg protein in ORAC_FL assay (P < 0.05) but did not alter antioxidant capacity determined by TEAC assay (P ≥ 0.05). The genotoxicity of H₂O₂ (50 ??M, 30 min) on hepatoblastoma HepG2 could be alleviated after HepG2 cells had taken up MPH after H₂O₂ exposure (P < 0.05). Moreover, the inhibition concentration (IC₅₀) of AA in HepG2 was lowered from 58.5 ??g mL^− 1 of AA alone to 38.5 ??g mL^− 1 when AA was freeze-dried with MPH in lactose excipient (P < 0.05). This study suggested that the efficacy of anticancer pentacyclic triterpene AA against hepatoblastoma HepG2 could be increased by co-drying with antioxidative mungbean protein hydrolysate in lactose excipient.     

Emulsifying properties of chickpea protein isolates: Influence of pH and NaCl

Structure and emulsifying properties of chickpea protein isolates (CPI) as a function of protein concentration, oil volume, pH and ionic strength were studied. The optimum protein concentration 2 g l⁻¹ used to determine the emulsifying properties was obtained. Emulsifying activity index (EAI) increased from 244 to 376 m² g⁻¹ with pH from 3.0 to 11.0 except the protein isoelectric point (pI 5.0), where the EAI was 20 m² g⁻¹ and emulsion droplet size was the largest. At lower ionic strengths (0.0–0.1 M NaCl, pH 7.0), EAI decreased from 253 to 72.4 m² g⁻¹; however, it increased from 72.4 to 231.4 m² g⁻¹ at higher ionic strengths (0.1–1.0 M NaCl). A positive relation between EAI and surface hydrophobicity (S₀) of CPI at various ionic strengths was obtained, while EAI was independent of S₀ under different pH values. α-Helix was the major configuration of CPI at the pI or lower ionic strength.