BACKGROUND: Different legume seeds may have different protein compositions and properties, thereby affecting applications in food systems. This study aimed to extract and characterize protein isolates from legumes grown in Thailand, including mung bean (MBPI), black bean (BBPI) and bambara groundnut (BGPI). RESULTS: All protein isolates had a protein content in the range of 85.2 –88.2%. The highest trypsin inhibitory activity was found in BGPI. All protein isolates exhibited satisfactory balanced amino acids with respect to the FAO/WHO pattern. MBPI and BBPI had three predominant proteins with a molecular weight (MW) range of 42 – 54 kDa, whereas BGPI had two dominant proteins with MW of 52 and 62 kDa. Based on differential scanning calorimetric analysis, MBPI and BGPI had two endothermic peaks, whereas three peaks were found for BBPI. All protein isolates exhibited similar FTIR spectra, indicating similarity in functional group and structure. All protein isolates showed a minimum protein solubility at around pH 4 – 5. CONCLUSION: All protein isolates were important sources of proteins with high lysine content. Isolates from different legumes showed slight differences in physiochemical and thermal properties. Those isolates can be used as proteinaceous ingredients in a variety of food products such as salad dressing, meat products and desserts. c � 2013 Society of Chemical Industry

Comparative study on chemical compositions and properties of protein isolates from mung bean, black bean and bambara groundnut

Effect of steam explosion on dietary fiber, polysaccharide, protein and physicochemical properties of okara

Germinated legumes and sprouts can be potential dietary sources of bioactive compounds. In this study, selected commercially available legumes grains (chickpea, red lentil, mung bean, kidney bean and soybean), were germinated at 30 and 40 °C for 5 days and the antioxidant and ACE inhibitory activities were measured by the DPPH radical scavenging and in vitro ACE inhibition assay, respectively. Significant differences (p  82% ACE inhibition reaching an IC50 value of 0.025 mg/mL.

Effect of germination on antioxidant and ACE inhibitory activities of legumes

Protein quality in six soybean varieties, based on subunit composition of their protein, was correlated with quality of the produced tofu. Also, protein changes due to a pilot plant processing method involving high temperature/pressure and commercial rennet as coagulant were assessed. In each soybean variety, glycinin (11S) and β-conglycinin (7S) as well as 11S/7S ratio significantly changed from beans to tofu. Between varieties, the 11S/7S protein ratio in seed indicated genotypic influence on tofu yield and gel hardness (r = 0.91 and r = 0.99, respectively; p < 0.05). Also, the 11S/7S ratio correlated with soymilk pH (r = 0.89, p < 0.05), leading to a relationship between soymilk pH with protein recovery and yield of tofu (r = 0.94 and r = 0.91, respectively; p < 0.05). The soybean β'-subunit of 7S protein negatively influenced tofu hardness (r = -0.91, p < 0.05). Seed protein composition and proportion of 7S protein subunits under the applied production method had an important role in defining tofu quality.

Assessment of Soy Genotype and Processing Method on Quality of Soybean Tofu

Evaluation of protein digestibility of fermented soybeans and changes in biochemical characteristics of digested fractions

Protein extracts of 640 soybean cultivars and landraces, mainly from China and a few from the US, were analyzed for their components and subunits based on distribution patterns of bands with varying molecular weights (MW) under SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). The number and molecular weight of the bands in SDS-PAGE varied among materials and showed a tendency of continuous distribution. Accordingly, the SDS-PAGE patterns of the soybean protein extracts were divided into two regions: the region of bands with MW < 44 KDa and that with MW ≥ 44 KDa. The first region containing mainly 11S proteins was divided into four parts, called subunit groups, i.e. 11S-1 (14.4–22 KDa), 11S-2 (22–26 KDa), 11S-3 (26–34 KDa) and 11S-4 (34–44 KDa). The second region containing mainly 7S protein was divided into six subunit groups, i.e. 7S-1 (44–49 KDa), 7S-2 (49–55 KDa), 7S-3 (55–67 KDa), 7S-4 (67–73 KDa), 7S-5 (73–82 KDa) and 7S-6 (82–91 KDa). The sum of relative contents of 11S-1–11S-4 was obtained as the relative content of 11S protein, those of 7S-1–7S-6 as that of 7S protein, and therefore, the 11S/7S ratio obtained. The proposed criteria were demonstrated to be simple, stable and feasible. Among the 640 tested materials, 39 lacked 11S-1 but none lacked the other 11S subunit groups, while deficiencies existed in all the six subunit groups of 7S, indicating a great potential for the genetic variation of protein components and subunits for breeding for the improvement of protein qualities.

Shunhu Liu

Papers

A Study on Subunit Groups of Soybean Protein Extracts under SDS-PAGE