Comparative study of the polypeptide profiles and functional properties of Sinapis alba and Brassica juncea seed meals and protein concentrates

Defatted meals and protein concentrates from six accessions of Sinapis alba and one accession of Brassica juncea mustard seeds were analysed for their polypeptide profile and functional properties. Two types of protein concentrates were prepared using acid‐induced and calcium‐induced protein precipitations. Meals from the S alba seeds had similar polypeptide composition, which was different from that of the B juncea meal. Non‐reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that two of the major polypeptides (50 and 55 kDa) in S alba seeds were susceptible to acid‐induced precipitation but resistant to calcium‐induced precipitation. The B juncea meal proteins were significantly (p ≤ 0.05) more susceptible to heat coagulation than the S alba meal proteins. Emulsifying activity index was significantly higher (p ≤ 0.05) in the B juncea meal and protein concentrates when compared with similar products from S alba. It was concluded that the presence of a high‐molecular‐weight (135 kDa) disulfide‐bonded polypeptide could have contributed to the lower emulsifying power of the S alba products when compared with the B juncea proteins that do not have this polypeptide. Copyright © 2005 Society of Chemical Industry     

Angiotensin‐converting enzyme‐inhibitory activity in protein hydrolysates from normal and anthracnose disease‐damaged Phaseolus vulgaris seeds

BACKGROUND: Bean seeds are an inexpensive source of protein. Anthracnose disease caused by the fungus Colletotrichum lindemuthianum results in serious losses in common bean (Phaseolus vulgaris L.) crops worldwide, affecting any above‐ground plant part, and protein dysfunction, inducing the synthesis of proteins that allow plants to improve their stress tolerance. The aim of this study was to evaluate the use of beans damaged by anthracnose disease as a source of peptides with angiotensin‐converting enzyme (ACE‐I)‐inhibitory activity. RESULTS: Protein concentrates from beans spoiled by anthracnose disease and from regular beans as controls were prepared by alkaline extraction and precipitation at isolelectric pH and hydrolysed using Alcalase 2.4 L. The hydrolysates from spoiled beans had ACE‐I‐inhibitory activity (IC₅₀ 0.0191 mg protein mL^?1) and were very similar to those from control beans in terms of ACE‐I inhibition, peptide electrophoretic profile and kinetics of hydrolysis. Thus preparation of hydrolysates using beans affected by anthracnose disease would allow for revalorisation of this otherwise wasted product. CONCLUSION: The present results suggest the use of spoiled bean seeds, e.g. anthracnose‐damaged beans, as an alternative for the isolation of ACE‐I‐inhibitory peptides to be further introduced as active ingredients in functional foods. © 2012 Society of Chemical Industry     

Physicochemical properties of soy protein prepared by enzyme‐assisted countercurrent extraction

Synchronous improvements of both nutritional properties and the flavour of protein by optimising preparation processes are highly challenging. The prehydrolysis of soy meals by cocktail enzyme (β‐glucosidase, phytase and acid protease) treatment and subsequent countercurrent extraction were designed based on similar hydrolysis conditions. The composition, flavour volatiles and physicochemical properties of soy proteins were investigated. Compared to alkaline extraction and acid precipitation, enzyme‐assisted countercurrent extraction significantly increased protein yield and carbohydrate content, accompanied by a decrease in protein purity. This protein exhibited larger molecular weight distribution, less flavour volatiles, higher thermal stability and surface hydrophobicity, as evidenced by higher denaturation temperature (T_d) and enthalpy change (ΔH) of protein. The conversion of isoflavone glycosides to aglycone and the partial degradation of phytic acid were observed for enzyme‐prepared soy proteins. These results suggest a feasible protocol for producing a nutrient‐improved soy protein with excellent flavour and thermal stability.     

The influence of tempeh fermentation and conventional cooking on anti‐nutrient level and protein bioavailability (in vitro test) of grass‐pea seeds

BACKGROUND: The solid state fermentation tempeh type is known to result in the decomposition of anti‐nutrients and the improvement of nutritional value of legume seeds. The aim of the research was to study the influence of tempeh fermentation and conventional cooking on (1) levels of 3‐N‐oxalyl‐L ‐2,3‐diaminopropionic acid (ODAP), soluble phenols, trypsin inhibitors and inositol phosphates; and (2) the in vitro bioavailability of proteins in grass‐pea seeds. RESULTS: Tempeh fermentation reduced the level of ODAP, trypsin inhibitors and phytates by 93, 99 and 22%, respectively, and increased protein bioavailability by about 25%. Protein bioavailability from conventionally cooked seeds was higher than from fermented seeds. However, during the in vitro test more soluble protein (approx. 10%) was released from 100 g tempeh product than from cooked seeds. CONCLUSIONS: Solid state fermentation and cooking resulted in seeds of comparable quality but the tempeh contained much less ODAP, which is very promising in the context of popularising grass pea. Copyright © 2008 Society of Chemical Industry     

Effect of heat treatment on antinutrients and precaecal crude protein digestibility in broilers of four tropical crop seeds

Four tropical crop seeds, namely Vigna unguiculata (Cowpea), Mucuna pruriens, Manihot esculenta and Centrosema pubescens were thermally processed for 1 h at 100 °C and analysed for their antinutritional factors (ANF). Four hundred and forty‐eight 1‐day‐old broilers were used to determine the effect of heating the seeds on their precaecal crude protein (CP) digestibility. Total phenols, protein precipitable tannins and l ‐dopa were higher in the mucuna and centrosema seeds and diets than in the vigna and manihot seeds and diets. Phytic acid was of similar occurrence in all the raw seeds. Heat treatment resulted in reduction in all the ANF in the seeds. Precaecal CP digestibility, feed intake and growth rate were significantly (P < 0.01) increased in the heat‐treated mucuna and centrosema diets. There was no significant effect on the digestibility of CP, feed intake and growth rate in birds on the vigna and manihot diets owing to heat treatment of the seeds. The results showed that heating improved the nutritive quality of mucuna and centrosema seeds but was not of significant advantage with vigna and manihot seeds when used at levels of up to 150 g kg^?1 in diets.     

A novel antifungal peptide from foxtail millet seeds

BACKGROUND: Antifungal proteins (AFP) help plants to combat phytopathogenic fungi and thus protect plants from the devastating damage caused by fungal infections and prevent massive economic losses. To date, several proteins with antibacterial and/or antifungal properties have been isolated and characterized from different plant species and tissues; however, there are no reports concerning the antifungal peptide from foxtail millet seeds. RESULTS: An antifungal peptide with a molecular mass of 26.9 kDa was isolated from dry seeds of the foxtail millet (Setaria italica (L.) Beauv.), using a procedure that involved four chromatographic steps. The antifungal peptide was adsorbed on CM‐Sepharose, Affi‐gel blue gel and Superdex 75. It was further purified by C₁₈ reverse‐phase high‐performance liquid chromatography and submitted for analysis of peptide mass fingerprint. The Mascot peptide mass fingerprint of the isolated protein hit no existing protein (score > 60), and it was proved to be a novel antifungal peptide. It inhibited mycelial growth in Alternaria alternate with an IC₅₀ of 1.3 µmol L^?1, and it also exhibited antifungal activity against Trichoderma viride, Botrytis cinerea and Fusarium oxysporum. Transmission electron microscopy of mold forms of Alternaria alternate after incubation with 20 µg mL^?1 of the antifungal protein for 48 h revealed marked ultrastructural changes in the fungus. CONCLUSION: A novel antifungal peptide with high potency was isolated from foxtail millet seeds. Copyright © 2011 Society of Chemical Industry     

Chia Seed (Salvia hispanica L.) as a Source of Proteins and Bioactive Peptides with Health Benefits: A Review

The consumption of chia seed (Salvia hispanica L.) has increased in recent years due its high content of omega‐3 fatty acids and dietary fiber. This seed also has a high concentration of proteins and essential amino acids, becoming a promising source of bioactive peptides. The objective of this review was to identify the composition and the beneficial effects of chia seeds (S. hispanica L.), their proteins, peptides, and their potential impact on human health. The UniProt database was used to identify the chia proteins and their amino acid sequences. The BIOPEP database was used to analyze the peptides's bioactive potential. A total of 20 proteins were cataloged in chia seed, 12 of those were involved in the regular metabolic processes of the plant cells. However, eight proteins were specifically related to production and storage of plant lipids, thus explaining the high concentration of lipids in chia seeds (around 30%), especially omega‐3 fatty acids (around 20%). The analyses of amino acid sequences showed peptides with bioactive potential, including dipeptidyl peptidase‐IV inhibitors, angiotensin‐converting enzyme inhibitors, and antioxidant capacity. These results correlated with the main health benefits of whole chia seed in humans such as antioxidant capacity, and hypotensive, hypoglycemic, and anticholesterolemic effects. Such relation can be associated with chia protein and peptide compositions and therefore needs further investigation in vitro and in vivo.     

Evaluation of the fixed nitrogen-to-protein (N:P) conversion factor (6.25) versus ingredient specific N:P conversion factors in feedstuffs

BACKGROUND: The crude protein (CP) of feedstuffs is important as an indicator of essential and non‐essential amino acids for livestock. The protein (P) level needs to be known accurately, to minimize the feeding of excess nitrogen (N) and to reduce N pollution. Laboratory methods for determining N content report N from amino acids, but also N from ammonia and from non‐amino acid sources. The determined CP based on 6.25 × N level typically overestimates the true protein of feedstuffs. RESULTS: Determined ingredient‐specific N:P conversion factors k_A, k_P and k were not equal to the standard 6.25 factor. The k_A had the highest value in all ingredients, which leads to the estimation of specific crude protein (SCP), which is closer to true protein (the summation of the total amino acid residues from amino acid analyses). The SCP(k_A) was lower than CP and true protein in all ingredients, demonstrating that CP might overestimate the actual protein in feedstuffs. CONCLUSION: Based on data from 677 feedstuff samples from 2009, it is concluded that the mean k_A should be 5.68 for corn, 5.64 for soybean meal, 5.74 for corn DDGS, 5.45 for poultry by‐product meal and 5.37 for meat and bone meal. Copyright © 2011 Society of Chemical Industry     

Chemical composition,protein fractionation,essential amino acid potential and antimetabolic constituents of an unconventional legume,Gila bean (Entada phaseoloides Merrill) seed kernel

Physical characteristics of pods and seeds, proximate composition, different protein fractionation, SDS‐PAGE analysis of proteins, amino acid composition, starch content, fatty acid profiles and various antimetabolic substances of Gila bean (Entada phaseoloides Merrill) were studied. The pod length and the number of seeds per pod ranged from 55 to 90 cm and from 5 to 11 respectively. The kernel comprised 66.1% of the seed weight (18.41 ± 1.14 g). The seed kernels contained 256.7 g kg^?1 crude protein, 108.1 g kg^?1 lipid, 27.3 g kg^?1 ash and a high content of carbohydrate (585.7 g kg^?1). The levels of potassium, phosphorus, zinc and iron were similar to those in conventional pulses. Among the different protein fractions of seed kernels, albumins constituted the major storage proteins (69.7%). The kernel proteins were rich in essential amino acids, particularly sulphur‐containing amino acids, and their values appeared to be higher than the FAO/WHO (1990) reference protein for a 2–5‐year‐old growing child and soybean, and comparable to hen egg. Seed kernel lipids contained high levels of unsaturated fatty acids, oleic and linoleic acids, which accounted for 83% of the total fatty acid recovered. The kernel exhibited high trypsin and chymotrypsin inhibitor activities (96.65 mg TI g^?1 and 30.02 CIU mg^?1 sample respectively) in addition to containing phenolics, phytic acid, lectins and oligosaccharides. Another major toxic constituent was identified as a group of triterpenoid saponins (3.21%), which had high haemolytic activity (HeU) against cattle erythrocytes and caused high mortality in fish. The in vitro digestibility of the kernel protein was low (67%). © 2001 Society of Chemical Industry     

Identification and proteomic analysis of a novel gossypol-degrading fungal strain

BACKGROUND: Cottonseed meal, an important source of feed raw materials, has limited use in the feed industry because of the presence of the highly toxic gossypol. The aim of the current work was to isolate the gossypol‐degrading fungus from a soil microcosm and investigate the proteins involved in gossypol degradation. RESULTS: A fungal strain, AN‐1, that uses gossypol as its sole carbon source was isolated and identified as Aspergillus niger. A large number of intracellular proteins were detected using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, but no significant difference was observed between the glucose‐containing and gossypol‐containing mycelium extracts. Two‐dimensional gel electrophoresis results showed that the protein spots were concentrated in the 25.0–66.2 kDa range and distributed in different pI gradients. PDQuest software showed that 51 protein spots in the gels were differentially expressed. Of these, 20 differential protein spots, including six special spots expressed in gossypol, were analyzed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. CONCLUSION: The fungus AN‐1 biodegraded gossypol and the proteomic analysis results indicate that some proteins were involved in the gossypol biodegradation during fungus survival, using gossypol as its sole carbon source. Copyright © 2011 Society of Chemical Industry     

Nutrient composition and the use of solubility to estimate rumen degradability of food proteins in cattle

The use of protein solubility to estimate protein degradability in cattle was tested using 12 by‐products representing agricultural and distillers' food raw materials (RM). Agricultural RM included cereals (rice bran, maize gluten feed), legumes (field beans, soybean hulls) and oil‐seeds (rape meal, sunflower meal). Distillers' RM involved dark grains (DG1, DG2, DG3) and malts (MT1, MT2, MT3). Soluble proteins, as proportions of total soluble N (TSN), were extracted from RM and their undegraded residues (RU) after 18 h of in sacco rumen incubation in cattle (dg₁₈) by using water (albumin), salt (globulin), acid (glutalin 1) and alkali (glutalin 2) in succession. RM and RU differed significantly for all soluble proteins (P < 0.001). While albumin was the major protein in legume RM (0.74TSN), glutalin 1 was the major protein in legume RU (0.54TSN). Cereals were the most variable group, where maize gluten contained five times more albumin and two times more TSN in RM and three times more glutalin 1 + 2 in RU than those in rice bran. Distillers' RM contained slightly less albumin (0.53 vs 0.56TSN) but over twice as much glutalin 1 (0.29 vs 0.12TSN) as agricultural RM. Albumins were the most (0.55TSN, RM; 0.16TSN, RU) and glutalin 1 the least (0.21TSN, RM; 0.48TSN, RU) degradable proteins. There were moderate to strong correlations between protein solubility, dg₁₈ and acid detergent‐insoluble N (ADIN). ADIN correlated satisfactorily with glutalin 1 + 2 (r = ?0.55, RM and ?0.70, RU), TSN (r = ?0.75, RM and RU) and slowly degradable N, (SDN; r = ?0.70, all). TSN in all RM related well with SDN (r = 0.65) and dUN (r = 0.72). TSN in distillers' RM correlated closely with SDN (r = 0.91) and dUN (r = 0.96). Glutalin 1 in distillers' foods correlated extremely well (r = 0.94, RM and 0.93, RU) with dUN. Globulins correlated most consistently with SDN (r = 0.82, all; r = 0.77, agricultural; r = 0.92, distillers' RM). It is possible to predict protein degradability from the presence or absence of soluble proteins in various foods. While ADIN may be more suitable to predict DUN, globulins showed more potential to predict SDN in various foods. However, it may be necessary to be selective in choosing solvents for various foods. Further studies must validate this method by using a greater range of foods before suggesting its routine use for food evaluation. © 2001 Society of Chemical Industry     

Effect of phenolic acids on the rheological properties and proteins of hard wheat flour dough and bread

BACKGROUND: The effects of different phenolic acids on the rheological properties and gluten proteins of hard wheat flour dough and bread were investigated. Caffeic, ferulic, syringic and gallic acids were each blended with hard wheat flour at a concentration of 4.44 µmol L^?1 g^?1 flour. RESULTS: Mixing time and tolerance were reduced with the addition of phenolic acids. The phenolic acids reduced the maximum resistance to extension (R_max) and increased the extensibility of dough, with effects in the following order: gallic < syringic < ferulic < caffeic acid. The effect on R_max was more pronounced in overmixed dough. Loaf volume was most significantly decreased with the addition of caffeic acid. Extraction of sodium dodecyl sulfate‐soluble high‐molecular‐weight proteins was increased in both mixed and fermented doughs by the addition of ferulic and caffeic acids. The order of influence of the phenolic acids on the rheological properties and protein structure of dough and bread was consistent with that of their antioxidant activity. CONCLUSION: The addition of caffeic and ferulic acids reduced R_max and increased the extensibility of hard wheat flour dough by modifying the high‐molecular‐weight gluten, which resulted in decreased bread volume. Copyright © 2011 Society of Chemical Industry     

Chemical, Physical, and Gel-forming Properties of Oxidized Myofibrils and Whey- and Soy-protein Isolates

Myofibrils, oxidized with FeCl₃/H₂O₂/ascorbate, exhibited an increase in carbonyls and amines, SH→SS conversion, peptide scission, myosin polymerization, and a decrease in thermal stability and gel‐formation ability. Amino‐acid side chains of whey‐protein isolates (WPI) and soy‐protein isolates (SPI) were also modified during oxidation, but the thermal stability of WPI or SPI was not significantly altered. Oxidation increased elasticity of SPI gel but not that of WPI gel. Similarly, oxidation promoted interactions of myofibrils with SPI but not with WPI, resulting in > 30% increases in elasticity of the myofibril/SPI composite gel over its nonoxidized control. Hence, in processed meats where oxidation occurs, the presence of soy proteins may enhance the functionality of myofibrillar proteins.     

Polypeptide profile and functional properties of defatted meals and protein isolates of canola seeds

Laboratory‐defatted meals from four types of canola seeds were analysed for protein profile by reducing and non‐reducing forms of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). In the absence of a reducing agent (2‐mercaptoethanol), four major polypeptide bands (16, 18, 30 and 53 kDa) were prominent in similar ratios in all varieties. In the presence of mercaptoethanol, significant reductions in intensity of the major bands occurred, suggesting that the major polypeptides contained smaller units which were held together by disulphide bonds. Meals from Brassica napus seeds had higher protein solubilities than meals from Brassica rapa seeds. Meals with higher protein solubility values also had higher foaming capacity (FC) values. Generally, the acid‐precipitated (pH 4.0) protein isolates (APPIs) had higher FC values than the calcium‐precipitated isolates (CPPIs). On the other hand, the CPPIs formed emulsions with higher values of emulsifying activity index (EAI) when compared to the APPIs. The results indicate that variations in functional properties of protein isolates and meals between the four seed types were probably due to differences in protein conformation in aqueous solutions rather than differences in polypeptide composition. © 2001 Society of Chemical Industry     

Assessment of protein fractions of three cultivars of <Emphasis Type="Italic">Pisum sativum</Emphasis> L.: effect of germination

Protein composition, nitrogen and amino acid content of Osborne fractions in different cultivars of Pisum sativum L. (cv. ucero, cv. ramrod and cv. agra) seeds were investigated and the effect of germination on these parameters was also analysed. Albumins comprised the main protein fraction in raw seeds, globulins were constituted mainly by vicilin, with a smaller proportion of the glutelin and prolamine fractions. Regarding the amino acid profile of pea protein fractions, although differences among pea cultivars were found, in general albumin, glutelin and prolamine fractions presented Asp, Glu and Gly as the major non-essential amino acids (NEAA) and Lys as the main essential amino acid (EAA). The globulin fraction, however, presented Asp, Glu, Gly and Arg as the major NEAA and Leu, Phe, Lys, and Thr as the main EAA. In general, the albumin fraction accounted for more sulphur amino acids and Lys, followed by the glutelin + prolamine fraction. Germination caused an increase in the total protein content of P. sativum cv. ucero and P. sativum cv. ramrod. In the albumin fraction a wide number of proteins underwent degradation and convicilin disappeared from the globulin fraction of pea sprouts whilst vicilin and legumin decreased slightly. In general, all the Osborne fractions of pea sprouts presented higher EAA contents than raw seeds. The estimated essential amino acid indexes of protein fractions for P. sativum cv. ucero (EAAI_adult and EAAI_egg) improved with the germination process whilst for P. sativum cv. ramrod and P. sativum cv. agra depended on the Osborne fraction.     

Hypolipidemic effect of enzymatically extracted sunflower seed protein fraction

An attempt was made to enzymatically extract the protein fraction (PF) from sunflower seeds and investigate its dietary effect on the growth, plasma and tissue lipid profiles, plasma protein content, erythrocyte membrane lipid profile and organ weights of rats. Extraction of dehulled sunflower seeds in an aqueous medium in the presence of the enzyme pectinase at 50 ± 1 °C and pH 4.5 yielded a protein fraction with low residual chlorogenic acid and fibre contents. Rats fed the sunflower seed protein fraction showed a similar body weight gain and food efficiency ratio as rats fed casein. However, the different dietary proteins had different effects on plasma total cholesterol and triglyceride contents. The rats fed the sunflower seed protein fraction showed a significant decrease in plasma cholesterol (p < 0.02) and triglyceride (p < 0.02) concentrations compared to the casein‐fed rats. The PF‐fed rats also exhibited a significant difference in erythrocyte membrane phospholipids and phosphatidylcholine/phosphatidylethanolamine ratio. Rats fed the different dietary proteins did not show much variation in plasma protein content, liver and brain lipids and organ weights. These results demonstrate the hypolipidemic action of the sunflower seed protein fraction and that it can be considered a suitable edible protein like casein. © 2000 Society of Chemical Industry     

Electrophoresis to determine the molecular weight distribution in soluble proteins from various foods and their rumen‐resistant residues in cattle

Electrophoresis was used to visually identify and determine the molecular weight (MW) distribution of rumen‐degradable and rumen‐resistant or escape peptides in soluble proteins from 12 agricultural and distillers' food raw materials (RM) and their residues (RU) following 18 h of in sacco rumen incubation (dg₁₈) in cattle. Soluble proteins were extracted by using water, salt, acid and alkali in succession to represent albumins, globulins, glutalin 1 and glutalin 2 respectively. RM and RU differed substantially in the MW range, number and intensity of bands for various soluble proteins. The bands were mostly below the MW range of 66 kDa. Low‐MW (<25 kDa) peptides were greater in number than high‐MW (>25 kDa) peptides in almost all soluble proteins from RM. Individual peptides behaved differently during rumen incubation. Their resistance to or escape from rumen degradation varied with the class of food, type of soluble protein and their MW range. On average, low‐MW albumins in agricultural foods were more resistant to rumen degradation (0.41 RM vs 0.12 RU; 29%) than their high‐MW counterparts (0.12 RM vs 0.02 RU; 21%). In contrast, high‐MW glutalin 1 was more resistant (0.03 RM vs 0.22 RU) than low‐MW glutalin 1 (0.09 RM vs 0.26 RU) in most agricultural foods. Globulins contained the least and glutalins the most resistant peptides in distillers' foods. While this study reveals an association between dg₁₈ and protein type, structure and size, we do not recommend the immediate use of electrophoresis for routine food evaluation unless more studies are undertaken. It may, however, be suitable for further characterisation of the degradation of specific, selected peptides by specific micro‐organisms. © 2001 Society of Chemical Industry     

Nutritional study of raw and popped seed proteins of Amaranthus caudatus L and Amaranthuscruentus L

The nutritional value of raw and popped (similar to popcorn preparation) seed proteins of two amaranth species, Amaranthus caudatus L and A cruentus L, was investigated. After popping, the true protein content in A caudatus and A cruentus decreased by 9 and 13% respectively. Among the amino acids, the loss of tyrosine due to the popping effect was the highest, followed by phenylalanine and methionine. Leucine was the first limiting amino acid in the raw samples, followed by lysine, while the reverse order was observed in the popped samples. The in vivo protein quality of raw and popped seeds was tested with male weanling rats and compared with wheat flour and casein samples. There was no difference between the in vivo digestibility of the raw and the popped seeds, although the in vitro digestibility was slightly higher for the popped samples. The protein efficiency ratio (PER) for all the amaranth seed samples was higher than that for the wheat sample, while the PER for the raw amaranth seed samples was close to that for the casein reference protein. The rat blood serum levels of total cholesterol, triglycerides and high‐density lipoprotein cholesterol for all the amaranth samples were lower than those for the reference protein, while the wheat flour sample showed the lowest values. Copyright © 2004 Society of Chemical Industry     

PROTEIN EXTRACTABILITY, FRACTIONATION AND AMINO ACID COMPOSITION OF SOME LEGUMINOUS SEEDS FOUND IN NIGERIA

Protein content in eight minor legume seeds grown in Nigeria was determined, and protein was fractionated into albumin, globulin, prolamin and glutelin. Seed protein concentrates (SPC) were prepared from legume seeds; and extractabilities of protein N, total N content, yield and the amino acid profiles are reported. The globulins and glutelins were the major fractions. Mucuna seeds (velvet bean) appear to be the most promising species for obtaining SPC based on the high values for extractability of SPC, protein N and total N. Amino acid composition shows that the sulfur‐containing amino acids, methionine + cysteine, were the most limiting amino acids in the seed proteins. Lysine content (9.12 g/100 g) of Mucuna seeds was high. Prosopis africana (mesquite bean) contains remarkably high levels of methionine and lysine (3.55 and 6.50 g/100 g protein, respectively), which make it a good potential supplement to the starchy tuber and cereal diets of the local population. It was concluded that Milletia thonningii, Adenanthera pavonina (coral seeds), Lonchocarpus sericeus and Mucuna seeds have a promising potential as sources of low‐cost protein for possible use as food/feed supplements.