Elsevier

Food Chemistry

Volume 321, 15 August 2020, 126706
Food Chemistry

Development of high methoxyl pectin-surfactant-pea protein isolate ternary complexes: Fabrication, characterization and delivery of resveratrol

https://doi.org/10.1016/j.foodchem.2020.126706Get rights and content

Highlights

  • HMP-surfactants-PPI ternary complexes were successfully fabricated.

  • The ternary complexes became better delivery vehicles for Res.

  • HMP-Rha-PPI ternary complex exhibited better protective effect on Res.

  • HMP-Rha-PPI ternary complex delay the release of Res in in vitro digestion.

Abstract

The purpose of this study was to fabricate ternary complexes composed of pea protein isolate (PPI), high methoxyl pectin (HMP) and individual surfactants including rhamnolipid (Rha), tea saponin (TS) and Ethyl lauroyl arginate (LAE), for the delivery of resveratrol (Res). A combination of electrostatic attraction and hydrophobic interaction was dominantly responsible for the formation of HMP-surfactant-PPI complexes. The physicochemical properties of the ternary complexes were affected by surfactant types as well as mass ratios of individual surfactant to PPI. HMP-Rha-PPI1:1, HMP-TS-PPI1:1 and HMP-LAE-PPI1:25 complexes had higher denaturation temperatures of 82.78 ± 0.31, 80.21 ± 0.02 and 79.98 ± 0.86 ℃, respectively. The HMP-Rha-PPI1:1 ternary complex could be an effective delivery system, which were effective to retard photo- and thermal- degradation of Res as well as delayed the release of Res in in vitro digestion.

Introduction

Resveratrol (Res) is a natural bioactive compound, which has pharmacological activities against many chronic diseases. However, it has unstable properties, such as poor solubility and low bioavailability, which greatly limit its utilization in functional food products. In order to break these limitations, delivery systems are designed and applied. Among the delivery systems, nano complexes have been widely employed in food fields relying on their advantages, such as effective targeting and sustained release. Proteins are usually utilized to fabricate nano complexes, and most of these proteins are of animal origins. However, plenty of studies have identified that these proteins are common food allergens (O'Sullivan, Murray, Flynn, & Norton, 2016). Apart from this disadvantage, the dietary restrictions to these proteins, which are caused by religious beliefs, are also raising concerns. Therefore, researchers tried to seek kinds of consumer-friendly proteins of plant origins to replace those of animal origins.

To date, soy protein isolate (SPI) is the most widely used protein of plant origins in the world. However, recent studies have shown that pea protein isolate (PPI) seems to be much more promising as the replacement of proteins of animal origins than SPI. Not only due to its high nutritional value, availability, and low cost (Lam, Can Karaca, Tyler, & Nickerson, 2016), but also, comparing to SPI, it is less connected to GMO questions, and is not listed as an allergenic ingredient (Schreuders et al., 2019). Despite aforementioned advantages, the application of PPI is still limited by its poor solubility and high sensitivity to aggregation near the isoelectric point. One feasible method to solve these problems is to prepare protein-polysaccharide soluble complexes (Brando et al., 2001). At present, numerous studies have reported that the complexation with polysaccharides could improve the solubility and stability of PPI (Klemmer, Waldner, Stone, Low, & Nickerson, 2012).

Pectin is an anionic polysaccharide from plant cell walls, and it is widely used in food and pharmaceutical industries. Besides, pectin is usually used to interact with proteins to stabilize them. Therefore, many researchers have tried to use pectin to stabilize PPI. For example, Lan, Chen, and Rao (2018) have confirmed that HMP could interact with PPI and form soluble complexes with better stability than individual PPI. Pillai et al. (2019) also investigated that the influence of pH, type of pectin and the mass ratio of PPI to pectin on the phase behavior of PPI-pectin complexes. They indicated that the methylation degree of pectin could affect the phase behavior of PPI-pectin complexes. In general, pectin is divided into high-methoxyl pectin (HMP, DM > 50%) and low-methoxyl pectin (LMP, DM < 50%) according to the degree of methylation (Li et al., 2019). In our previous study, we found that the PPI-HMP complex exhibited better stability than the PPI-LMP complex. Based on this finding, HMP was selected in this study. Although the complexation with HMP could improve the solubility of PPI, we found that the PPI-HMP complex is still not a perfect delivery vehicle for water-insoluble functional components, which is due to the fact that HMP is too hydrophilic to provide more hydrophobic sites for the functional components. Therefore, we have to incorporate more hydrophobic groups in the complex.

Surfactants are amphiphilic surface-active molecules that consist of a hydrophilic head group and a hydrophobic tail group. A wide variety of surfactants are available for utilization within food and beverage products. More importantly, surfactants could also interact with proteins and improve the stability of proteins (Feng, Wu, Wang, & Liu, 2017). Therefore, a new hypothesis was proposed that the incorporation of surfactants not only could provide more hydrophobic groups, but also worked with polysaccharides to stabilize proteins. A recent study verified our hypothesis, it showed that the caseinate as a kind of macromolecule surfactant worked with pectin to stabilize zein (Chang et al., 2017a, Chang et al., 2017b), and the loading capacity of the complex was significantly increased due to the presence of caseinate (Veneranda et al., 2018, Chang et al., 2017a, Chang et al., 2017b). Indeed, in addition to the macromolecule surfactant, the small molecule surfactant was also commonly found in food systems (such as ice cream). As far as we know, the small molecule surfactant has not been used in the water-soluble protein-based ternary complex systems. Hence, the principal purpose of this study was to determine whether the PPI-HMP-surfactant ternary complex with higher stability could be fabricated using small molecule surfactants, and explore whether Res could be successfully encapsulated, protected, and controlled release by the ternary complexes.

In general, surfactants can be classified into ionic and nonionic ones, while ionic surfactants can be further classified into cationic and anionic ones according to their electrical charge properties. Different types of surfactants have distinct characteristics, thus, there is no single surfactant that can be used to fabricate every kind of colloidal delivery system. Therefore, to screen the most suitable surfactant for the delivery system of resveratrol, we chose three types of surfactants according to the electrical charge properties of surfactants to fabricate ternary complexes. They are rhamnolipid (anionic surfactant), ethyl lauroyl arginate (cationic surfactant) and tea saponin (nonionic surfactant), respectively. We characterized the particle size, zeta potential, encapsulation efficiency, loading capacity, and stability of ternary complexes using a variety of analytical tools. We also examined the impact of invitro digestion on the complexes, as well as on the stability of Res in the complexes. We believed that this work will provide valuable information for the fabrication and application of the ternary delivery system, which was designed on the basis of PPI.

Section snippets

Materials

PPI (protein content of 85%) in powder was purchased from Yantai Oriental Protein Tech Co., Ltd. (Shandong, China). HMP (GENU pectin; type JMJ; DE value of 90%) was kindly provided by CP Kelco (Atlanta, Georgia, USA). Rha (with 90% purity) was purchased from Shaanxi Pioneer Biotech Co., Ltd. (Shaanxi, China). TS (with 95% purity) was obtained from Hunan Hanqing Biotech Co., Ltd. (Hunan, China). LAE was acquired from AF Biotech Co., Ltd. (Chengdu, China). Resveratrol (purity ≥98%) was sponsored

Complex characteristics

Particle size and zeta potential of the ternary complexes with different mass ratios of individual surfactants to PPI were shown in Fig. 1. The particle size of the ternary complexes was highly dependent on the mass ratio of surfactant to PPI. However, the zeta potential of the ternary complexes was almost unaffected by the mass ratio of surfactant to PPI, except for the HMP-LAE-PPI complex. For the samples of HMP-Rha-PPI and HMP-TS-PPI complexes (Fig. 1 A and B), when surfactants were

Conclusion

In this study, the HMP-surfactant-PPI ternary complexes were successfully fabricated. The physical and structural properties of the ternary complexes were mainly affected by the type and level of surfactants. The hydrogen bonding and electrostatic interaction were the main forces to induce the formation of HMP-Rha-PPI and HMP-TS-PPI complexes. The electrostatic attraction was the dominant force to induce the formation of the HMP-LAE-PPI complex. By comparison, HMP-Rha-PPI1:1, HMP-TS-PPI1:1 and

CRediT authorship contribution statement

Qing Guo: Conceptualization, Methodology, Software, Writing - original draft, Data curation. Jiaqi Su: Formal analysis, Investigation. Xin Shu: Formal analysis, Investigation. Fang Yuan: Writing - review & editing. Like Mao: Writing - review & editing. Yanxiang Gao: Conceptualization, Supervision, Project administration, Funding acquisition, Writing - review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

We acknowledge the testing support from Beijing Zhongkebaice Technology Service Co., Ltd.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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