Characteristics of winged bean (Psophocarpus tetragonolobus) seeds during soaking and boiling

The effects of soaking small, medium and large seeds of Psophocarpus tetragonolobus (L) DC for up to 24h and then boiling the seeds for up to 30 min, or boiling the raw seeds for up to 120 min, were examined. Trends for hardness and water absorption of the beans were similar for all bean sizes. Soaking and/or boiling reduced the hardness of beans and increased the water absorption leached solids, water holding capacity and swelling power. Small beans were the hardest and showed the lowest level of the other characteristics. Medium sized beans were softer and had higher values of the above four parameters. Soaking for 24 h and then boiling for 30 min was more efficient in reducing the hardness of the beans than boiling for 2h. Linear regression showed high correlations among almost all the parameters measured.     

Volatiles derived from lipoxygenase-catalysed reactions in winged beans (Psophocarpus tetragonolobus)

Volatiles formed by the decomposition of hydroperoxides generated by lipoxygenase-catalysed oxidation of linoleic acid contribute a beany flavour to legumes. Eleven volatiles have been identified after treatment of linoleic acid by lipoxygenase extracted from winged bean seeds. Five of these volatiles; namely, hexanal, 2-heptanone, 2-pentyl furan, undecane and tridecane, have been detected in the headspace of a sample of winged bean flour after storage. Moisture levels below 10% appear to inhibit lipoxygenase activity, since headspace samples from raw and heat treated samples had very similar composition, and the peroxide value remained low after 10 months' storage at 37°C. Incubation of a lipoxygenase extract with linoleic acid gave rise to a larger concentration of volatiles at pH 9 than at pH 6·5 due to the increased lipoxygenase activity at the higher pH.     

Gel filtration fractionation of winged bean (Psophocarpus tetragonolobus) proteins

Winged bean proteins were extracted by a pH 9.5, 0.3M borate extraction medium. The extracted proteins were fractionated by Sepharose CL-6B gel filtration chromatography into four fractions. Fraction 2 (F2, mol. wt 200 000) and Fraction 3 (F3, mol. wt 35 000) are the two major protein fractions. F3 was further resolved into Fraction 3A (F3A, mol. wt 44 160) and Fraction 3B (F3B, mol. wt 23 700) by Sephadex G-75 gel filtration chromatography. Both F2 and F3 fractions were heterogeneous when examined by polyacrylamide gel electrophoresis method. There are some varietal variations in the distribution of winged bean protein fractions recovered by gel filtration chromatography. Trypsin inhibitor and chymotrypsin inhibitor activity were found only in F3B, whereas haemagglutinating activity was found only in F3A.     

Investigations of antinutritional factors of the winged bean (Psophocarpus tetragonolobus)

Twelve varieties of winged bean (Psophocarpus tetragonolobus) were analyzed for tannin, phytic acid, trypsin inhibitor, chymotrypsin inhibitor, α-amylase inhibitor and lectin. Tannin contents ranged from 1·35–6·75 mg/g of bean. Phytic acid contents ranged from 7·77–12·03 mg/g of bean and phytate-phosphorus represented a considerable percentage of the total phosphorus (44·3–54·8%). Chymotrypsin inhibitory activities were about twofold higher than trypsin inhibitory activities. α-amylase inhibitory activities could not be detected in any of the winged bean varieties used in this study. Hemagglutinating activities were observed with respect to all types of trypsinized human erythrocytes (A, B and O). However these activities disappeared completely after heating in a boiling water bath for 10 min.     

The extractability of winged bean (Psophocarpus tetragonolobus) seed trypsin inhibitors

The extractability of winged bean (Psophocarpus tetragonolobus) seed trypsin inhibitors by aqueous salt solution varies with pH as well as the ionic strength of the extraction medium. With a high ionic strength extraction medium, the extractability of the seed trypsin inhibitors increases with rising pH. With a low ionic strength extraction medium, however, a region of minimum extractability of trypsin inhibitors was observed at pH 4. At pH above 7, the same maximum amount of trypsin inhibitors (1.47 million inhibitor units (i.u.) per 100 g of seed meal) was extracted with both high and low ionic strength extraction media. The solution characteristics of winged bean seed proteins exhibited similar trends. Ninety-five per cent of the extracted seed trypsin inhibitors could be precipitated from 30–70% saturated ammonium sulphate solutions. The winged bean seed trypsin inhibitors isolated by ammonium sulphate fractionation lost all inhibitory activity when heated at 100°C for 10 min at alkaline pH.     

Characteristics of the proteins of the tubers of winged bean (Psophocarpus tetragonolobus (L.) DC)

The crude protein content (amino acid Nx6.25) of six varieties of Psophocarpus tetragonolobus tuber varied from 12.7 to 16.9%. Free amino acids and low molecular weight peptides account for about 40% of this crude protein value. The non-dialysable protein content of winged bean tuber is therefore less than previously assumed, but is still relatively high for a tuber crop. The amino acid contents of the tuber varieties were similar and nutritionally acceptable, except for the sulphur containing amino acids. Fresh tubers showed trypsin and chymotrypsin inhibitory activity and haemagglutinin activity. The inhibitor levels showed little variation but differences in the levels of haemagglutinin activity were found. On SDS-polyacrylamide gels the tuber proteins revealed a simple subunit pattern of two major polypeptides of M_r 30000 and 20000. Fractionation of the tuber proteins showed that the inhibitors and haemagglutinins comprise about 35% of the tuber protein. In addition, three acidic protein (about 12% of tuber protein), three basic proteins (ca. 34% of tuber protein) and a minor component (M_r～10000) with a high cystine content (11 residue %) were identified.     

Isolation of the acidic and basic lectins from winged bean seed (Psophocarpus tetragonolobus (L.) DC)

The acidic and basic lectins of the winged bean were isolated from seed extracts by affinity chromatography on lactose-Sepharose 6B and melibiose Bio-Gel P150, respectively. The lectins isolated from six varieties of Psophocarpus tetragonolobus, collected from different regions of south-east Asia, showed no significant differences in their properties; their subunit M_r and amino acid compositions were the same as those of the acidic and basic lectins isolated by non-affinity methods. On isoelectric focusing the affinity purified acidic lectins showed two major protein components (isolectins) while the affinity purified basic lectins had four protein components. The acidic lectins showed a preference for β-D-galactosides and they agglutinated trypsinised human type A, B and O erythrocytes but not trypsinised rabbit erythrocytes. The basic lectins showed a preference for α-D-galactosides and they agglutinated trypsinised rabbit and human type A and B erythrocytes but not trypsinised human type O erythrocytes.     

Carbohydrate Composition of Winged Bean (Psophocarpus tetragonolobus)

The carbohydrate composition of winged bean has been studied. The seeds contain about 42.2% total carbohydrates of which starch alone accounts for 36.2%. The total monosaccharides constituted 2.7% and were identified as glucose (1.17%) and fructose (1.5%); oligosaccharides amounted to only 0.61% and were identified as sucrose, raffinose, stachyose, and verbascose, on a dry defatted basis. The cold water soluble gum of winged bean contains glucose and xylose as the major sugars together with a small amount of arabinose while hot water soluble gum was found to be a glucantype polymer. Hemicellulose A consisted of glucose, xylose, and arabinose (15.5:9:1) whereas hemicellulose B consisted exclusively of glucose indicating that it is also a glucan-type polymer.     

Some characteristics of the roots of the winged bean [Psophocarpus tetragonolobus (L.) DC]

Three accessions of winged bean [Psophocarpus tetragonolobus (L.) DC] tuberous roots from Thailand were examined for their crude protein (N × 6.25), non-protein nitrogen and starch contents. The roots were further analysed for their trypsin inhibitor and urease activities and for the presence of tannins and cyanogenic compounds. Crude protein was found to be high in comparison with other root crops (5.7–6.7% fresh weight) and this contained a high proportion of non-protein nitrogen (7.4–15.0%). Amino acid content of the crude protein, when compared with mature winged bean seeds, revealed a deficiency in the sulphur-containing amino acids but an exceptionally high aspartic acid content. Starch was the major carbohydrate present in the flesh of the roots (21.7–32.1% fresh weight). Root samples were found to contain high levels of trypsin inhibitory activity (13.5–30.1 TIU mg^?1 fresh weight). No urease activity or cyanide could be detected in any of the root accessions studied.     

Variation in protein and trypsin inhibitor activity with maturity and amino acid composition of winged bean (Psophocarpus tetragonolobus) seeds

The protein and trypsin inhibitor activity in pods and seeds of winged bean (Psophocarpus tetragonolobus (L) DC) increase, and in the pod hull decrease, with the maturity of plant. The seeds of 21 cultivars both exotic and of Indian origin cultivated on marginal alkaline soil (pH 8.7) were analysed for protein (36.4–45.3) and amino acid composition (lysine 4.8 to 6.7).     

The protein,trypsin inhibitor and lipid of the winged bean [Psophocarpus tetragonolobus (L) DC] seeds

The protein, trypsin inhibitor and lipid of the seeds from 15 New Guinea and 15 Thai winged bean varieties grown in Malaysia were analysed. The results show that winged bean seeds have a high protein content, ranging from 27.8 to 47.2% (based on dry seed wt). The trypsin inhibitor contents vary from 1.6 to 3.6 million i.u. 100 g^?1 of seeds; these trypsin inhibitor activities could be destroyed almost completely by a simple heat treatment. The oil content varies from 15.2 to 27.8% of the dry seed wt. Saturated fatty acids account for 31–37% of the total fatty acids and behenic acid (22:0) alone constitutes about 14–17% of the saturated fatty acid content. Unsaturated fatty acids account for 63–69% of total fatty acids; oleic and linoleic acids together constitute 57–64% of the unsaturated fatty acids.     

Chemical Composition Studies on Winged Bean (Psophocarpus tetragonolobus) Tubers

To add data to the very limited information on winged bean tubers, samples from 26 varieties were analyzed for proximate analysis, tannin, trypsin inhibitor activity (TIA) and nonprotein nitrogen (NPN). The averages obtained were: crude fat, 0.96%, ash, 2.94%; acid detergent fiber, 16.56%; crude protein, 16.4%; carbohydrate, 57.72%; tannin, 5.32 mg/g tubers; trypsin inhibitor, 1033 TIU/g tubers. NPN constituted only a small percentage (16.2%) of the total nitrogen indicating that most of the nitrogen is protein. A significant proportion of NPN (76%) was ninhydrin positive, indicating free amino adds, peptides and possibly other amines. Tannin concentration was higher than those present in seeds. The presence of TIA necessitates heat processing before consumption.     

Isolation and properties of the lectins from the tuberous roots of winged bean Psophocarpus tetragonolobus (L.) DC

The tuberous roots of winged bean (Psophocarpus tetragonolobus (L.) DC) contain two distinct groups of lectins corresponding to the acidic and basic lectins of the seed. The tuber isolectins were separated by chromatography on Ultrogel AcA44 and SP-Sephadex C-25, and purified by affinity chromatography. The acidic and basic lectins were also isolated from tuber extracts in a single step by affinity chromatography on lactose-Sepharose 6B and melibiose Bio-Gel P150, respectively. The lectins isolated from the tubers of six varieties of P. tetragonolobus showed no significant differences in their properties. The molecular and physicochemical properties of the tuber acidic and basic lectins were essentially identical to that of the corresponding winged bean seed lectins; the only exception was a small difference in the isoelectric points of the subunits of acidic lectins of seed and tuber as observed on isoelectric focusing in 8 m urea.     

Effect of Partial Proteolysis on the Functional Properties of Winged Bean (Psophocarpus tetragonolobus) Flour

The effect of partial proteolysis of winged bean flour with a protease from A. oryzae on its functional properties has been determined. At 45% hydrolysis, nitrogen solubility in water increased twofold and in 1M NaCl solution by 63%. Bulk density increased from 0.387 to 0.597 g/mL. Foam volume showed a maximum increase of 50% at 18% hydrolysis and then decreased. Emulsifying capacity did not show any change. Water absorption capacity decreased from 245g/100g to 135g/100g at 45% hydrolysis and oil absorption capacity from 190g/100g to 120g/100g.     

Effect of Extraction Conditions on the Extractability of Winged Bean (Psophocarpus tetragonolobus (L) DC) Proteins

Protein extractability from defatted winged bean flour was studied under various conditions of pH (2, 4, 6, 8, 10, 12), temperature (15°, 30°, 45°C) and time (10, 20, 30 min). Results indicated that protein extractability was strongly pH dependent. Maximum protein extract-ability was attained at pH 12 while the minimum extractability occurred at pH 4. Protein extractability was not significantly affected at the various temperature and time combinations; however, when extraction time was extended (at 15 min increments) from 30 min to 120 min, significantly higher (15%) protein was extracted at 30°C after an additional 60 min. Increased solvent-to-flour ratios resulted in increased protein extractability, but increased salt (NaCl and CaCl₂) concentrations (1M) decreased extractability.     

Effect of Acetylation and Succinylation on the Functional Properties of Winged Bean (Psophocarpus tetragonolobus) Flour

Winged bean flour was acylated to various degrees and changes in functional properties were monitored. Nitrogen solubility in water increased up to ?80% acylation and then decreased. Water absorption capacity increased continuously with the extent of acylation. The fat absorption capacity of the acetylated flour increased up to ?30% acetylation and then decreased while that of the succinylated flour remained unchanged. Emulsion capacity showed the same trend as nitrogen solubility in water. Foam capacity increased due to acylation but foam stability decreased. Bulk density of the acetylated flour increased up to ?80% acetylation and then decreased. Succinylated flour had higher bulk density at all levels of succinylation.     

Response of intestinal proteinase activities to the feeding of isolated winged bean (Psophocarpus tetragonolobus) and soya bean (Glycine max) trypsin inhibitors in rats

The antinutritional activities of trypsin inhibitors (TIs) were compared between winged beans (Psophocarpus tetragonolobus) and soya beans (Glycine max). The inhibitors of the two beans were isolated by trypsin‐bound Sepharose 4B, and 50 mg of lyophilised powders were intubated intragastrically into 24 h fasted rats. The activities of trypsin and chymotrypsin were compared after 30, 60 and 180 min in the washings of the upper, middle and lower parts of the small intestine. The elution profiles of TI and non‐TI compounds in the affinity chromatography were similar in the two beans, and the antitryptic activities were concentrated 5.5 and 6.2 times (based on specific activity) for winged beans and soya beans respectively. Regardless of the TI fed to rats, trypsin activity in the upper intestine was suppressed to almost undetectable levels at 30 and 60 min after intubation. The activities in the middle and lower intestines were also substantially lowered when rats were fed winged bean TI, and significant differences were detected at 30 and 60 min after intubation when compared with rats fed soya bean TI. However, at 180 min after feeding, no differences were found in the trypsin activity in any gut segments. Similar inhibitory properties of isolated TIs were observed in chymotrypsin activities in the small intestine. The results suggest that winged bean TI may have greater inhibitory activity on the intestinal proteinase compared with soya bean TI. © 2001 Society of Chemical Industry     

Isolation and Physicochemical Properties of Starch from Winged Bean (Psophocarpus tetragonolobus)

Preparation and physicochemical properties of winged bean starch have been studied. Gelatinization temperature range was 60–70°C and it exhibited single stage swelling and low solubility. The extensive solubility in dimethylsulfoxide may be due to heterogeneous bonding forces within the granule. The amylolytic susceptibility of native and gelatinized starch with human salivary α-amylase and glucoamylase was studied. The starch was found to be non-ionic. The amylose content was 38.5%.     

四棱豆油脂的脂肪酸组成测定

选取4个四棱豆品种的种子,用甲醇和氯仿提取其中的油脂,并用毛细管柱测定脂肪酸组成.结果显示,四棱豆油中主要含有28种脂肪酸,其中单不饱和脂肪酸的平均含量为38.20%,主要为油酸;多不饱和脂肪酸平均含量为34.88%,主要为亚油酸、α-亚麻酸和EPA;饱和脂肪酸平均含量为25.76%,主要为棕榈酸和硬脂酸.