Stability Mechanism of Two Soybean Protein-Phosphatidylcholine Nanoemulsion Preparation Methods from a Structural Perspective: A Raman Spectroscopy Analysis

Ying Zhu,Yang Li,Shuang Zhang,Xiaonan Zhang,Zhongjiang Wang,Linyi Zhou,Fei Teng,Guoping Yu,Huan Wang,Changling Wu,Baokun Qi,Lianzhou Jiang

doi:10.1038/s41598-019-43439-5

Ying Zhu, Yang Li + Show 10 more

Open Access

https://doi.org/10.1038/s41598-019-43439-5

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Journal: Scientific Reports	Publication Date: May 6, 2019
Citations: 18	License type: open-access

Affiliation: Northeast Agricultural University

Abstract

Ultrasound treatment and high-pressure homogenization were used to prepare soybean protein (SP)-phosphatidylcholine (PC) nanoemulsions in this study. Nanoemulsions prepared by high-pressure homogenization were more stable. The structural changes of SP and PC under ultrasound treatment and high-pressure homogenization treatment were investigated by Raman spectroscopy. It could be concluded that ultrasound and high-pressure homogenization treatments increased both the content of α-helix and unordered structure but decreased that of β-structures of SP, while the interaction between SP and PC decreased α-helix content and also reduced unordered structure and β-sheet structure. Ultrasound treatment and high-pressure homogenization exposed more tryptophan and tyrosine residues to promote hydrophobic interaction between SP and PC, which was beneficial for stabilizing the nanoemulsion. The SP-PC interaction exerted a more significant effect on side chain structure than those observed under ultrasound treatment and high-pressure homogenization. The dominant g-g-t vibrational mode of the disulfide bond of soybean protein was not appreciably changed by the two preparations. High-pressure homogenization increased the disorder of lipid chains of PC, promoting SP-PC interaction and thereby increasing the stability of the nanoemulsion. The structural change provided a theoretical basis for preparation of two nanoemulsions.

Highlights

Nanoemulsions have smaller droplet sizes and higher stability, enabling widespread use in foods and beverages[10]
This study aimed at analyzing the interaction and structural changes of soybean protein (SP)-PC complexes induced by ultrasound treatment and high-pressure homogenization using Raman spectroscopy to provide a better understanding of the preparation and properties of SP-PC nanoemulsions
It could be seen that the mean particle size of nanoemulsions prepared by ultrasound treatment increased from 282.4 nm to 309.8 nm during 30 days of storage, while the mean particle size of nanoemulsions prepared by homogenization slightly increased from 217.4 nm to 223.8 nm

Summary

Introduction

Nanoemulsions have smaller droplet sizes (average droplet diameter less than 200 nm) and higher stability, enabling widespread use in foods and beverages[10]. The emulsifying properties of soybean protein isolate stabilized by phospholipid were improved by ultrasound treatments[11]. Raman spectroscopy is a novel technology which is unaffected by the presence of water. It can be applied and represents an excellent approach to protein surveillance within solid or aqueous samples and for detecting the interaction between samples, providing information on the protein structure, the environment of some side chains and the local conformations of disulfide bonds[16,17,18]. This study aimed at analyzing the interaction and structural changes of SP-PC complexes induced by ultrasound treatment and high-pressure homogenization using Raman spectroscopy to provide a better understanding of the preparation and properties of SP-PC nanoemulsions

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Conclusion