Characterization of the physicochemical properties of protein isolates obtained from lupin bean (lupinus mutabilis) cultivars and their application as micronutrient delivery systems

Abstract: Meeting the protein needs of a growing population sustainably is one of the key challenges of our time. Plant-based proteins are increasingly sought as substitutes for more expensive animal-based proteins due to environmental, health, economic, and ethical considerations. Legumes, cultivated globally for human and animal consumption, are valued for their nutrient density. Lupinus mutabilis (lupin bean), a high-value legume from the Andean region, offers a nutritional profile comparable to soybeans and serves as a sustainable, non-GMO protein source. Additionally, lupin beans provide a vital income stream for rural and indigenous communities, with significant potential for market expansion.
This study focused on isolating and characterizing lupin protein isolate (LPI) from lupin flour (INIAP 450 Andino) through alkaline water extraction and isoelectric precipitation. The resulting LPI contained over 95% protein. SDS-PAGE analysis revealed dominant protein bands between 20 and 76 kDa, primarily α- and β-conglutin, with lower concentrations of γ-conglutin. LPI solubility was lowest at its isoelectric point (pH 5) and highest under alkaline conditions (pH 10-12). Emulsifying capacity ranged from 23-25% across LPI concentrations (25 and 50 mg/mL) and pH levels (3-9). Foam showed stability (55%) even after an hour at room temperature, especially under low pH conditions.
To demonstrate LPI’s application as a micronutrient delivery system, LPI nanoparticles with vitamin D₃ (LPI-VD₃) were developed. These nanoparticles had a size range of 76-118 nm and a ζ-potential below -30, indicating good stability in solution. This research highlights the potential of lupin beans as a versatile ingredient for human consumption, broadening the understanding of protein functionality in underutilized food sources. Furthermore, it offers sustainable and economic opportunities for low-income farmers in the Andes. Future studies will evaluate the stability and bioavailability of LPI-VD₃ nanoparticles.