Cowpea Protein Isolates Research Articles

Enhanced characterization and utilization of cowpea protein isolate: rheological and textural properties of heat-induced gels for plant-based egg omelet formulation

This study aimed to evaluate the potential of cowpea isolate (CPI) as an effective plant-based egg substitute by comparing its composition and physicochemical properties with those of commercial isolates, including mung bean, soy, and pea proteins. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis identified a distinctive vicilin-like globulin in CPI that is critical for the unique functional properties of CPI. CPI has a smaller particle size, resulting in superior gelation capacity and water retention, which are essential for egg substitute applications. Thermal analysis revealed the high stability of CPI, which is advantageous for food processing. Notably, the unique heat-induced gelation behavior of CPI, characterized by a smooth transition from solid- to liquid-like states, provided a strength not observed in its commercial counterparts. Microstructural analysis showed that the CPI gel closely resembled the egg gel, underscoring the potential of CPI to mimic the texture of eggs, particularly in omelets.

Effect of pH on Foaming Properties (FC and FS) of Protein Isolates from Two Varieties (DAS & BS) of Nigerian Cultivated Solojo Cowpea (Vigna Unguiculata L. Walp)

Effect of pH on the foaming properties (FC and FS) of protein isolates from two Varieties (DAS & BS) of Nigerian cultivated Solojo cowpea (Vigna Unguiculata L. Walp) was investigated. Results show that the foaming capacity (FC) followed the solubility trend, with a high foaming capacity at pH 2, which slowly reduced between pH 4 - 6 and gradual increase again with pH as the pH approached 10, where it had another high value. As shown in Figures 1-6 noticeable changes in FC were detected as the pH of the protein solution progressed from pH 2 to 10, with minimum foaming capacity at pH 4 in all cases except for DFDAS flour and BS protein isolate (pH 6). The foaming capacity value for 6 h soaked and 48 hr germinated flours, at pH 4 were observed to be greater than at pH 2 and 6. While the maximum was observed in some cases at pH 8 and some pH 10 but FFDAS Raw, 36 and 48 hr; FFBS, 6 hr; DFBS, Raw and 72 hr; BS, 6 and 24 hr germinated, all had their own max values at pH 2. Defatting was also observed to improve the foaming capacity values of all the treatment. The foaming capacity ranged between 15.19 to 121.16%; 44.76 to 127.36%; 31.23 to 110.93%; 30.84 to 121.16%; 64.97 to 210.00%; 62.67 to 222.00% for FFDAS, DFDAS, FFBS, DFBS, DAS, and BS, respectively. The pattern of FC change followed the pH dependent solubility flow of the test material, showing the importance of solubility on foam formation which confirms that solubility of protein has a great influence on the activities of foam also increasing the pH from 4 to 10 improved the foaming characteristics of flour. This observation proved the authenticity that foaming property depends on protein solubility. The foaming capacity of cowpea protein isolates was pH dependent and high at alkaline pH in comparison to acid region.

Emulsifying Capacity of Cowpea Protein Isolates. Effect of Thermal and Hydrolytic Treatment.

In this work, modifications due to the effect of thermal treatments (TT 70 and 90°C) and partial hydrolysis by digestion with alcalase (LH) on the emulsifying properties of cowpea protein isolates (CPIs) extracted at pH 8 and 10 were analyzed. In addition, the influence of protein concentration [0.1 and 1% (w/v)] was evaluated. Emulsions (O:W) were prepared and particle size, stability, interfacial composition, and microstructure were studied. Fresh emulsions formulated with TT CPIs presented lower values of volume-weighted mean droplet size (D4.3), with the increase in temperature and treatment time, compared to the untreated CPIs. After seven days of storage, D4.3 and the indexes of flocculation (FI) and coalescence (CI) increased, mainly at 90°C. On the other hand, the emulsions with LH CPIs presented lower D4.3 values compared to all the conditions tested, remaining unchanged during the storage time. The destabilization process in the TT CPIs emulsions revealed coalescence at 0.1% (w/v) and cremated-flocculation at 1% (w/v). The presence of polypeptides of low molecular mass (MM) at the interface would be responsible for the better stability found in emulsions with LH CPIs, compared to those formulated with untreated and TT CPIs. Increasing the protein concentration resulted in a significant improvement of all emulsifying properties.

Prediction and Evaluation of Bioactive Properties of Cowpea Protein Hydrolysates

Cowpea protein hydrolysates were prepared using thermolysin, alcalase, and trypsin and analysed for bioactive properties, and then, the release of bioactive peptides was investigated in silico. It was found that the degree of hydrolysis reached 48% after 24 h hydrolysis with alcalase. The hydrolysate prepared using alcalase showed higher ACE inhibitory (62%) and DPPH scavenging activity (19%). SDS-PAGE analysis revealed that vignin was the major protein in cowpea protein isolate. In silico analysis indicated the presence of potential bioactive peptides with potent bioactivity in the primary structure of proteins. The 3D structure of proteins was built, upon which bioactive peptides were mapped using their location in the primary structure. The secondary structure and solvent accessible surface around each bioactive peptide were then calculated. On this basis, the higher degree of hydrolysis and bioactive properties of cowpea protein hydrolysate prepared by alcalase were explained, and structural factors influencing the release of bioactive peptides were investigated.

Indigestible cowpea proteins reduced plasma cholesterol after long-term oral administration to Sprague-Dawley rats

Cowpea protein isolate (CPI) was subjected to various dry and wet heat pretreatments followed by sequential digestion with pepsin and pancreatin; the undigested residues were isolated as the indigestible cowpea proteins (ICPs). All the ICPs exhibited in vitro bile acid-binding capacity but ICP from the slow cooling-induced gelation had the highest yield (68%) and was used for rat feeding experiments to determine effect on plasma total cholesterol (TC). Groups consisting of 3 male and 3 female Sprague-Dawley rats each were fed hypercholesterolemic diets that contained casein only or casein that was partially substituted with ICP of CPI for 6 weeks. Results showed diet that contained 5% (w/w) ICP was more effective in preventing TC increase (1.8 mmol/L) when compared to increases of 9.34 and 4.15 mmol/L for CPI and casein only diets, respectively.Graphical abstract

Structural and antioxidant properties of cowpea protein hydrolysates

Cowpea protein isolates extracted at pH 8.0 (I8) and pH 10.0 (I10) were hydrolysed by alcalase to obtain limited (I8LH and I10LH) and extensive (I8HH and I10HH) hydrolysates. Hydrolysis degree was 2.3% for I8LH, 4.6% for I10LH, 25.8% for I8HH and 24.1% for I10HH. The effect of hydrolysis was assessed by using solubility-pH profile assay, exclusion chromatography, gel electrophoresis, infrared and fluorescence spectroscopy and surface hydrophobicity. Subsequently, ABTS.+, ORAC and HORAC methods were applied to measure antioxidant activity in all samples. Electrophoresis, chromatography and surface hydrophobicity showed different profiles for I8LH and I10LH, presumably, due to the initial extraction pH of protein isolates. Limited hydrolysis increased antioxidant activity in both I8LH and I10LH with values higher than 70% for ABTS.+, 60% for ORAC and 45% for HORAC when compared to their respective isolates. Concerning extensive hydrolysis, I8HH and I10HH yielded similar effects when considering physicochemical, functional and antioxidant properties. Both I8HH and I10HH showed increments above 80% for ABTS.+, 80% for ORAC and 70% for HORAC in comparison to their respective isolates. These results indicate that limited and extensive alcalase hydrolysis of both isolates increases antioxidant activity regardless of the pH for initial protein extraction. Finally, peptides with a molecular weight between 1.8 and 6.5 kDa (I8HH and I10HH from FPLC soluble fractions) exhibited the highest ORAC activity. Thus, cowpea alcalase hydrolysates emerge as viable ingredients to formulate foods with antioxidant properties.

A Comprehensive Review on Protein Isolates from Legumes

Legumes play an vital function in human body due to dietary fiber, protein, minerals and vitamins and well-balanced essential amino acid. Legume proteins have gained increasing significance because of preferred functional properties, including gelling and emulsifying properties. Legumes contains anti nutritional compounds like Trypsin inhibitor(TIs), Phytic acid(PA), Tannin, Saponin, Lectins, They are not a major concern for most people, but may become a problem during periods of malnutrition, these can be easily removed by dehulled, cooking, thermal process, germination after soaking. Protein isolates are advanced form of protein containing the greater amount of protein with greater digestibility. There are different types of protein isolates like chickpea, whey protein Pea protein, cowpea protein isolates .The extraction methods of protein isolates are Iso electric extraction and alkaline extraction, citric acid extraction. Our aim of this paper is to optimize the protein isolate for diet people and innovate research in this field to produce some protein enriched food formulations.

Combined effect of cassava starch nanoparticles and protein isolate in properties of starch‐based nanocomposite films

AbstractThis study aimed to evaluate the effects of incorporation of cowpea protein isolate and cassava starch nanoparticles obtained by ultrasound on the properties of cassava starch:glycerol films. The cowpea bean protein isolate was successfully obtained with 72.5% of protein and solubility about 90%. The cassava starch nanoparticles yielded 97.85%. Increasing protein isolate concentration in starch:glycerol films resulted in a progressive reduction of water vapor permeability up to 27.0%. The cassava starch nanoparticles added films presented expressive increments in tensile strength (283.83%) as well as modulus of elasticity (204.31%), accompanied by decreasing in elongation at break (24.28%). The thermal stabilities of cassava starch films were affected by the addition of both protein isolate and cassava starch nanoparticles. The cassava starch nanoparticles obtained by ultrasound ensured the maintenance of film properties, optimizing the production time, with a higher yield, and without the need for chemical reagents. Thus, it could be useful for substitution of those obtained by acid hydrolysis. Therefore, giving rise to a trend of production of nanocomposite films suitable for reinforced packaging applications.

Physicochemical and pH-dependent functional properties of proteins isolated from eight traditional Chinese beans

Mung bean (MPI), black bean (BPI), adzuki bean (API), rice bean (RPI), black kidney bean (BKPI), speckled kidney bean (SKPI), chickpea (CPI) and cowpea (CPPI) protein isolates were assessed for their surface (charge, hydrophobicity: H0 and tension) and functional properties (solubility, water/oil holding capacity, WHC/OHC; foaming capacity/stability, FC/FS; emulsifying activity/stability indices, EAI/ESI and least gelling capacity, LGC) at pH 3.0, 5.0, 7.0 and 9.0, using soybean (SPI) and pea (PPI) protein isolates as controls. Physicochemical properties of these proteins, e.g., amino acid composition and colour (L*, a* &b*, WI: whiteness index), were also characterized. API, RPI, BKPI, SKPI and CCPI exhibited a better amino acid profile and protein digestibility than other isolates. BKPI (27.01) and SKPI (20.48) showed higher WI, while CPI (−21.92) was the lowest. For all isolates, H0 was the highest at pH 3.0, followed by pH 7.0 and 9.0, while surface tension was the highest at pH 5.0, followed by pH 3.0. Compared to other proteins, BKPI and SKPI showed lower solubility, but were more effective to reduce surface tension. Most of the traditional legume proteins had similar EAI. CCPI showed better WHC/OHC and API, RPI, BKPI and SKPI displayed excellent FC/FS. Interestingly, LGCs of MPI (8%), BKPI (4%), SKPI (4%) and CCPI (6%) at pH 3.0 were significantly lower than other isolates (12%). Overall, BKPI and SKPI have good nutritional profiles and also possess excellent functionalities (except for WHC/OHC), which are very promising as new alternative legume proteins to SPI and PPI.

Rheological characterization of the thermal gelation of cowpea protein isolates: Effect of pretreatments with high hydrostatic pressure or calcium addition

Pretreatments with high hydrostatic pressure (HHP) or calcium addition were assessed for thermal gelation of two cowpea protein isolates (protein extraction at pHs 8.0, standard (A8) or 10.0, pH-shifting-modified (A10). Maximum temperature of thermal processing and protein concentration (PC) on rheological behavior during and after gelling process were evaluated for pretreated isolates. The main effects of pretreatments occurred during heating since the proportion of heat-induced interactions that stabilized the matrixes increased. Those effects were due to partial denaturation (induced by HHP) and increase in Td (induced by CaCl2). HHP allowed gelation at temperatures (50–70 °C) lower than denaturation temperature and the obtaining of stronger gels at the highest PC (10.5 or 12.0 g/100 g). Calcium addition allowed gelation at low PC, but higher temperatures (80–95 °C) were required. Despite both pretreatments, A10 retained its ability to gel at lower PC than A8. Pressurized A10-gels were stronger than A8-gels. Calcium-added A10-gels were stronger than A8-gels at low PC (up to 7.5 g/100 g) or at high temperatures (90–95 °C), but no differences were found at high PC or at low temperatures. Thus, calcium-addition canceled those differences between A8 and A10 at high PC and at low temperatures.

Rheological characterization of thermal gelation of cowpea protein isolates: Effect of processing conditions.

Processing conditions such as protein concentration, maximum temperature, heating and cooling rates were analyzed for gelation of untreated (A8) and pH-shifting-modified (A10) cowpea protein isolates. Rheological measurements allowed characterization of finished gels as well as deeper understanding of gelling process.During thermal cycle, gelation started with a low denaturation degree, which reflects a good ability of cowpea proteins to interact with themselves and water. Gels were obtained at temperatures as low as 70 °C, a low temperature in the context of plant proteins.pH-shifting was a simple and inexpensive way to improve gel forming ability in terms of stiffness (G′) and minimum protein concentration and temperature required.Maximum temperature conditioned G′ and viscoelasticity (tan δ). Gels formed by A10 with treatments at 70–80 °C were more elastic than A8 ones, but differences were canceled when gels were formed at 90–95 °C.The highest increase of G′ occurred during cooling stage, which suggests a great contribution of hydrogen bonds. However, A10 gels had a greater contribution of heat-induced interactions, probably hydrophobic, than A8 gels, when thermal treatments were at 70–80 °C.The versatile gelling ability of cowpea protein isolates represents a way to introduce them as a replacement for animal proteins.

MOLECULAR PROFILE, PURITY AND PRESENCE OF TRYPSIN INHIBITORS IN COWPEA PROTEIN ISOLATES

ABSTRACT The most-used preparation process of protein isolates (PI) involves the isoelectric precipitation of the protein. Heating shortens the preparation time but this procedure may affect the purity, yield, molecular profile of the protein, and the activity of the trypsin inhibitor. This study aimed to investigate the effect of heating in the production of cowpea protein isolates. Crude whole beans (WB) were defatted with hexane, and the protein isolates obtained by isoelectric precipitation with (HPI), and without (NHPI) heating. The protein content of the WB and the PI was determined by the micro-Kjeldahl method, and the extraction yield estimated from the protein content at the end of extraction in relation to this content in the raw material. Possible losses of protein fractions were followed by SDS-PAGE, and the trypsin inhibitor activity determined by an enzymatic assay (BAPNA: benzoyl-DL-arginine-p-nitroanilide). Protein content in HPI was 83.3%, less than in the NHPI (92.2%). The HPI yield was lower (40.0%) as compared to the NHPI (42.3%). Electrophoresis indicated bands ranging from 13 to 262 kDa in WB; and the NHPI presented a protein fraction’s profile closer to that of the WB than to the HPI. The WB had the trypsin inhibitor activity, expressed as Trypsin Inhibitory Units (TIU), of 32.5±0.5 TIU /mg-protein; HPI showed 12.7±0.5 TIU /mg-protein (39% of that observed in WB) and the NHPI, 8.3±0.2 TIU /mg-protein (25.5%). Heating reduces the yield and purity of proteins in the isolates. However, the inhibitory activity of trypsin cowpea is most affected by the isolation procedure.

Calorimetric Study of Cowpea Protein Isolates. Effect of Calcium and High Hydrostatic Pressure

The thermal properties of cowpea protein isolates (CPI) were studied by differential scanning calorimetry under the influence of various conditions. An increase in the pH of protein extraction, from 8.0 to 10.0, during CPI preparation promoted a partial denaturation of cowpea proteins. Increases in enthalpy change of denaturation (ΔH) and temperature of denaturation (Td) were detected with increasing protein concentration from 7.5 to 10.5% (w/w). This behavior suggests that denaturation involves a first step of dissociation of protein aggregates. Calcium induced thermal stabilization in cowpea proteins, the increase in Td was ca. 0.3 °C/mM for protein dispersions of 7.5% (w/w) for 0 to 40 mM CaCl2. High hydrostatic pressure (HHP) induced denaturation in CPI in a pressure level dependent manner. The presence of calcium protected cowpea proteins towards HHP-induced denaturation when pressure level was 400 MPa, but not when it was 600 MPa. Thermal properties of cowpea protein isolates were very sensitive to processing conditions, these behaviors would have implications in processing of CPI-containing foodstuff.

Nutritional quality of the protein of Vigna unguiculata L. Walp and its protein isolate

A protein’s true digestibility and amino acid composition are important characteristics for its nutritional characterisation. This study determined the true digestibility of the protein from cowpea (Vigna unguiculata L. Walp.) and of its protein isolate, and their nutritional values were estimated after correcting for the amino acid score. The protein was isolated from the defatted whole bean by its alkaline solubilisation and isoelectric precipitation. The amino acid composition of the protein from the whole bean and from the isolate was determined by ion-exchange chromatography. Protein digestibility was assessed by the nitrogen balance method. The amino acid score is the lowest value obtained from the ratio between the individual amount of each essential amino acid present within the protein and the recommendation of each one for preschool infants. Methionine was the limiting amino acid in both the whole bean and the isolate. The true digestibility of the protein corrected by the amino acid score is an estimate of its nutritional value. The amino acid score for the whole bean was 0.44, and protein digestibility was 86.7%. For the isolate, these values were 0.60 and 96.7%, respectively. Correcting each score by the digestibility resulted in an estimated nutritive value of 38% and 58% for the whole bean and the isolate, respectively. Therefore, by having higher digestibility and increasing the bioavailability of essential amino acids, cowpea protein isolate is of interest for inclusion in food products, especially cereal-based products, which contain lysine as a limiting amino acid and are rich in methionine.

Physico-chemical and functional properties of cowpea protein isolate as affected by the dehydration technique

Cowpea protein isolate (CPI) was extracted through salt assisted extraction technique and dehydrated by freeze drying, spray drying and vacuum drying. The effect of dehydration technique for preparation of cowpea protein isolate powder on the nutritive and functional properties was investigated. The x-ray crystallography, phase transition analysis and surface morphology established the variation in the agglomerates and nature of the particles formed upon dehydration. Freeze-dried and spray dried powders displayed least gelation capacity at 8% compared to 12% for vacuum dried isolates besides higher gel strength. The crossover point of storage and loss modulus for freeze-dried CPI was observed much earlier than for the spray and vacuum dried CPI. The emulsion capacity and creaming stability indices for freeze dried CPI were higher. Vacuum dried samples however showed highest emulsion activity index (94.88 m2/g) and good foaming ability (88.89%). Thus depending on the functional attribute intended for end-use, the most economic drying method can be considered as reasonable option for converting the protein isolates into powders.

Physicochemical and functional properties of cowpea protein isolates treated with temperature or high hydrostatic pressure

Abstract The effect of thermal (TT, 70 and 90 °C) and high hydrostatic pressure (HHPTs, 200, 400 and 600 MPa) treatments on physicochemical and functional properties of cowpea protein isolates (CPIs) extracted at pH 8.0 (A8) and pH 10.0 (A10) was analyzed. The pH of protein extraction affected some physicochemical properties (surface hydrophobicity (Ho) and denaturation temperature), without affecting the functional properties. Treatments led to the formation of soluble protein aggregates stabilized by disulfide bonds, especially with TT at 90 °C. TT and HHPTs shifted the wavelengths of maximum emission to red and to blue, respectively. All treatments induced unfolding and denaturation. HHPTs was more efficient than TT to enhance gelation and water holding capacities. Interestingly, treated and untreated CPIs exhibited high values of solubility (72–97%). TT and HHPT induced greater changes in physicochemical and functional properties of A8 than in those of A10. Remarkably, functional properties were improved from the less energetic treatments (70 °C, 200 MPa). Industrial relevance The comparison between treatments (one traditional and one corresponding to an emerging technology) gives information about the possibility of obtaining modified proteins for different functional purposes. The modified cowpea protein isolates may be used in beverages because of high solubility, in desserts because of gel formation capacity and/or as additives in other foodstuff because of improved water holding capacity. This knowledge would increase the added value of a local production currently marketed without processing.

Effect of addition of thermally modified cowpea protein on sensory acceptability and textural properties of wheat bread and sponge cake

This paper investigates the sensory acceptability and textural properties of leavened wheat bread and sponge cake fortified with cow protein isolates that had been denatured and glycated by thermal treatment. Defatted cowpea flour was prepared from cow pea beans and the protein isolate was prepared (CPI) and thermally denatured (DCPI). To prepare glycated cowpea protein isolate (GCPI) the cowpea flour slurry was heat treated before isolation of the protein. CPI was more susceptible to thermal denaturation than GCPI as determined by turbidity and sulphydryl groups resulting in greater loss of solubility. This is attributed to the higher glycation degree and higher carbohydrate content of GCPI as demonstrated by glycoprotein staining of SDS PAGE gels. Water absorption of bread dough was significantly enhanced by DCPI and to a larger extent GCPI compared to the control, resulting in softer texture. CPI resulted in significantly increased crumb hardness in baked bread than the control whereas DCPI or GCPI resulted in significantly softer crumb. Bread fortified with 4% DCPI or GCPI was similar to control as regards sensory and textural properties whereas 4% CPI was significantly different, limiting its inclusion level to 2%. There was a trend for higher sensory acceptability scores for GCPI containing bread compared DCPI. Whole egg was replaced by 20% by GCPI (3.5%) in sponge cake without affecting the sensory acceptability, whereas CPI and DCPI supplemented cakes were significantly different than the control.

Cowpea protein isolates: Functional properties and application in gluten-free rice muffins

The present work was undertaken to explore application of cowpea protein isolates in gluten-free rice muffins. Protein isolates from large-white and small-red cowpeas were evaluated for physicochemical and functional properties. These were incorporated at three levels (4, 8 and 12 g/100 g) in rice flour to see their effect on muffin-making properties. Chromatographic analysis revealed that proteins of 133–137 kDa (vicilins) contributed to 53–60 g/100 g of the isolates. Protein isolate from white cowpea (WCPI) showed higher solubility, foaming and emulsification but lower water absorption than that from red cowpea (RCPI). Incorporation of protein isolates decreased flour paste viscosities (peak, breakdown and final) and increased batter viscoelasticity (above 8 g/100 g incorporation level), wherein WCPI exerted greater effect than RCPI. WCPI influenced crumb colour parameters (L*, a* and b*) marginally whereas RCPI increased a* while decreased L* and b* significantly. Firmness, springiness, cohesiveness and chewiness of the muffins increased above 8 g/100 g incorporation levels for both the protein isolates. WCPI increased muffin volume whereas RCPI decreased. The results suggested that not only the level of proteins but also their properties influence characteristics of gluten-free muffins.

Cowpea protein reduces LDL-cholesterol and apolipoprotein B concentrations, but does not improve biomarkers of inflammation or endothelial dysfunction in adults with moderate hypercholesterolemia.

The risks of cardiovascular diseases, the leading cause of death in the world, can be reduced by diet. Cowpea protein has been shown to significantly reduce total cholesterol, LDL-cholesterol, and liver steatosis in hamsters. The objective of this proof-of-concept study was to verify whether the consumption of cowpea protein improves lipid profile and biomarkers of inflammation and endothelial dysfunction in adults with moderate hypercholesterolemia. In a randomized, double-blind, crossover design, 38 hypercholesterolemic subjects (LDL-cholesterol = 182.5 ± 2.7 mg/dL) consumed 25 g/day of cowpea protein isolate or 25 g/day of casein (control group) for 6 weeks each, separated by a 4-week washout interval. Fasting blood samples were collected at baseline and at the end of each diet period. Lipids (total cholesterol, LDL-cholesterol, triglycerides, HDL-cholesterol) were determined by enzymatic methods, apolipoproteins (apoA-I and apoB) by standardized immunoassays, inflammatory biomarkers (C-reactive protein) by turbidimetry, and biomarkers of endothelial dysfunction (intercellular adhesion molecule 1 and vascular cell adhesion molecule 1) by enzyme-linked immunosorbent assays. Consumption of cowpea protein significantly reduced total cholesterol ( 12 %), LDL cholesterol ( 18.9 %), non HDL-cholesterol ( 16 %) and apoB ( 14 %), and increased HDL cholesterol (+2.7 %). No significant differences between treatment groups were observed for any of the serum inflammatory or endothelial dysfunction biomarkers. The present findings demonstrated the favorable effect of cowpea protein consumption on proatherogenic serum lipids and apoB in subjects with moderate hypercholesterolemia, similar to what was observed in a previous studies on animals.

The Effect of pH on Foaming Properties of Cowpea (Vigna ungiculata L.walp) Flour and Protein Isolates

The effect of pH on foaming properties on cowpea (Vigna ungiculata) seeds as whole cowpea flour (WCF), dehulled cowpea flour (DCF), dehulled defatted cowpea flour (DDCF) and cowpea protein isolates (CPI) obtained from DDCF by isoelectric (CPIA) and micellization (CPIB) precipitation was studied. The protein % was found to be 22.3% in (WCF) and 26% in (DDCF) flour, while 75 and 76% for CPIA and CPIB respectively. The foaming capacity (FC) and foam stability (FS) were greatly affected by pH values. FC of DDCF and CPIB showed minimum level at pH 2.0 while CPIA at pH 4.0. However, the FS of DDCF was highest at pH 5.0 while CPIA and CPIB were less stable. CPIB have poor FS compared to CPIA at all pH ranges (2-12). Maximum FS was observed at pH 9.0 for DDCF which remain stable up to standing period of 2 hr. CPIA form foam with highest initial volume and maximum FS was observed at pH 9.0. FC of all products was found to be higher at alkaline region of pH compared to acidic side. Defattening markedly increase the FC in the flours.