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

<jats:title>Abstract</jats:title><jats:sec><jats:title>BACKGROUND</jats:title><jats:p><jats:bold>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 (<jats:styled-content style="fixed-case">MBPI</jats:styled-content>), black bean (<jats:styled-content style="fixed-case">BBPI</jats:styled-content>) and bambara groundnut (<jats:styled-content style="fixed-case">BGPI</jats:styled-content>).</jats:bold></jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p><jats:bold>All protein isolates had a protein content in the range of 85.2–88.2%. The highest trypsin inhibitory activity was found in <jats:styled-content style="fixed-case">BGPI</jats:styled-content>. All protein isolates exhibited satisfactory balanced amino acids with respect to the <jats:styled-content style="fixed-case">FAO</jats:styled-content>/<jats:styled-content style="fixed-case">WHO</jats:styled-content> pattern. <jats:styled-content style="fixed-case">MBPI</jats:styled-content> and <jats:styled-content style="fixed-case">BBPI</jats:styled-content> had three predominant proteins with a molecular weight (<jats:styled-content style="fixed-case">MW</jats:styled-content>) range of 42–54 <jats:styled-content style="fixed-case">kDa</jats:styled-content>, whereas <jats:styled-content style="fixed-case">BGPI</jats:styled-content> had two dominant proteins with <jats:styled-content style="fixed-case">MW</jats:styled-content> of 52 and 62 <jats:styled-content style="fixed-case">kDa</jats:styled-content>. Based on differential scanning calorimetric analysis, <jats:styled-content style="fixed-case">MBPI</jats:styled-content> and <jats:styled-content style="fixed-case">BGPI</jats:styled-content> had two endothermic peaks, whereas three peaks were found for <jats:styled-content style="fixed-case">BBPI</jats:styled-content>. All protein isolates exhibited similar <jats:styled-content style="fixed-case">FTIR</jats:styled-content> spectra, indicating similarity in functional group and structure. All protein isolates showed a minimum protein solubility at around <jats:styled-content style="fixed-case">pH</jats:styled-content> 4–5.</jats:bold></jats:p></jats:sec><jats:sec><jats:title>CONCLUSION</jats:title><jats:p><jats:bold>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. © 2013 Society of Chemical Industry</jats:bold></jats:p></jats:sec>