Production and characterisation of protein isolates from Chilean granado beans (Phaseolus vulgaris L.)

Abstract

Granado beans, widely cultivated in Chile, offer plant-based proteins with functional benefits for healthier food formulations. These legumes have a 28% protein content (dry basis) with peptides called lectins that have the potential of reducing type-II diabetes. Our lab has developed a membrane-based method to produce protein isolates from oilseeds. This method was adapted for granado beans. The process involves alkaline extraction at pH 10, followed by ultrafiltration, diafiltration, acid precipitation at pH 4 and freeze-drying. The resulting precipitated protein isolate contains 81% protein, comparable to other legumes. However, the acid-soluble protein isolate (SPI) has a protein content of only 53% due to co-recovery of high molecular weight carbohydrates. The total phenolic compound contents of the protein products were low resulting in both products having an attractive light colour with no astringent taste. The characterisation of the SPI by High-Performance Liquid Chromatography found that it contained about 40% starch and other carbohydrates. To increase the protein content of SPI to ~90%, further purification steps to remove the carbohydrates are necessary.