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

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.