Improved encapsulation efficiency and storage stability of lutein by soy protein isolate nanocarriers with thermal and trypsin treatments

BACKGROUND: Encapsulation of bioactive compounds within protein-based nanoparticles has garnered considerable attention in the food and pharmaceutical industries because of its potential to enhance stability and delivery. Soy protein isolate (SPI) has emerged as a promising candidate, prompting the present study aiming to modify its properties through controlled thermal and trypsin treatments for improved encapsulation efficiency (EE) of lutein and its storage stability. RESULTS: The EE of lutein nanoparticles encapsulated using SPI trypsin hydrolysates (SPIT) with three varying degrees of hydrolysis (4.11%, 6.91% and 10.61% for SPIT1, SPIT2 and SPIT3, respectively) increased by 12.00%, 15.78% and 18.59%, respectively, compared to SPI. Additionally, the photostability of SPIT2 showed a remarkable increase of 38.21% compared to SPI. The superior encapsulation efficiency and photostability of SPIT2 was attributed to increased exposure of hydrophobic groups, excellent antioxidant activity and uniform particle stability, despite exhibiting lower binding affinity to lutein compared to SPI. Furthermore, in SPIT2, the protein structure unfolded, with minimal impact on overall secondary structure upon lutein addition. CONCLUSION: The precise application of controlled thermal and trypsin treatments to SPI has been shown to effectively produce protein nanoparticles with substantially improved encapsulation efficiency for lutein and enhanced storage stability of the encapsulated lutein. These findings underscore the potential of controlled thermal and trypsin treatments to modify protein properties effectively and offer significant opportunities for expanding the applications of protein-based formulations across diverse fields. © 2024 Society of Chemical Industry.