Elsevier

Food Chemistry

Volume 310, 25 April 2020, 125976
Food Chemistry

Short communication
Role of maltodextrin and inulin as encapsulating agents on the protection of oleuropein during in vitro gastrointestinal digestion

https://doi.org/10.1016/j.foodchem.2019.125976Get rights and content

Highlights

  • Olive leaves extract (OLE) was spray-dried with inulin (IN) or maltodextrin (MD).

  • Encapsulation of OLE protected oleuropein (OE) from gastrointestinal conditions.

  • OE reached the colon when OLE–MD and OLE–IN microparticles were digested.

  • OE bioaccessibility was higher in OLE–MD than in OLE–IN microparticles.

  • Encapsulation of OLE did not increase the OE potential bioavailability.

Abstract

Olive leaves extract (OLE) was spray-dried with maltodextrin (MD) or inulin (IN) to study the evolution of oleuropein (OE) during in vitro gastrointestinal digestion, its bioaccessibility and potential bioavailability. In the case of OLE–MD, OE was partially degraded in gastric and intestinal conditions; whereas in OLE–IN, OE was released under gastric conditions and partially degraded under intestinal conditions. In both cases, the encapsulation of OLE led to higher OE contents at the end of digestion, compared with non-encapsulated OLE, suggesting a protective role of the polysaccharides by the formation of non-covalent polysaccharides–OE complexes. OE bioaccessibility was ten times higher (p ≤ 0.05) in OLE–MD and OLE–IN than in non-encapsulated OLE. However, OE potential bioavailability, evaluated by tangential filtration, was not detected. Encapsulation technology and the encapsulant agent used may determine the release of the encapsulated compounds at a specific-site and their effect on health.

Introduction

Pruning of olive trees (Olea europaea L.) during olive oil production gives great amounts of leaves as waste (Şahin & Bilgin, 2018). However, olive leaves are a potential source of bioactive compounds (Rahmanian, Jafari, & Wani, 2015). Secoiridoids are the main family of phenolic compounds in the olive leaves (~85%), and oleuropein (OE) is the major compound (Talhaoui et al., 2014). OE shows a very low toxicity (Fu et al., 2010) and several beneficial effects on human health such as antioxidant, cholesterol-lowering, cardioprotective, anti-inflammatory, hypoglycemic or antimicrobial (Şahin & Bilgin, 2018).

Once extracted from leaves, phenolic compounds are prone to degradation due to adverse environmental and gastrointestinal conditions, compromising their bioactivity, bioaccessibility and bioavailability (Carrera-González, Ramírez-Expósito, Mayas, & Martínez-Martos, 2013). Encapsulation is a viable technology for the protection of phenolic compounds during storage and gastrointestinal passage, allowing their release at specific sites of the gastrointestinal tract where their absorption or action is intended. Among the encapsulation methods, spray-drying is the most widely used for the encapsulation of bioactive compounds in the food industry (Gharsallaoui, Roudaut, Chambin, Voilley, & Saurel, 2007); however, there are few studies focused on the microencapsulation of OLE by spray-drying (González et al., 2019, Kiritsakis et al., 2018, Kosaraju et al., 2006, Urzúa et al., 2017). Encapsulation of OLE has also been reported by other methods such as freeze-drying (Ganje et al., 2016), nanoemulsions and double emulsions (Mohammadi et al., 2016, Mohammadi et al., 2016) or nanoliposomes (Tavakoli, Hosseini, Jafari, & Katouzian, 2018). Maltodextrins of different dextrose equivalents are commonly used as encapsulating agents due to their high-water solubility, low viscosity and colourless solutions (Robert, García, & Fredes, 2017). However, this is a digestible polymer and the encapsulated bioactive compounds may be quickly released from during digestion, leaving them exposed to the gastrointestinal conditions. Inulin is a slightly branched (<5%) fructo‐oligosaccharide, composed of β‐(2-1) linked fructose units. Although inulin is moderately water soluble, its β-(2-1) glycosidic bonds make it indigestible by humans, in contrast with maltodextrin, but largely digestible by certain microorganisms in the gut (Barclay, Ginic-Markovic, Cooper, & Petrovsky, 2010). Therefore, inulin has been reported as a colonic delivery biopolymer, since it can pass relatively intact through the upper part of the gastrointestinal tract, reaching the colon where the bioactive compounds can be released (De Vos, Faas, Spasojevic, & Sikkema, 2010).

The degradation mechanisms for OE during gastrointestinal digestion have been studied in several models (Corona et al., 2006, Kendall et al., 2012, Martín-Vertedor et al., 2016, Mosele et al., 2014). Most of these studies have been performed on OLE or polyphenolic mixtures from olive oil, but studies on encapsulated OLE are scarce (Pacheco, González, Robert, & Parada, 2018). However, encapsulation of OLE and the biopolymers used as encapsulating agents, may significantly influence both bioaccessibility and bioavailability of the polyphenols (González et al., 2019, Pacheco et al., 2018). In our previous research, encapsulation of OLE with sodium alginate protected OE under gastric conditions, allowing its controlled released under intestinal conditions, together with higher bioaccessibility and potential bioavailability, compared with non-encapsulated OLE (González et al., 2019). The objective of this work was to study the bioaccessibility and potential bioavailability of OE from OLE encapsulated with maltodextrin and inulin by spray-drying, during in vitro simulated gastrointestinal digestion.

Section snippets

Materials

Olive leaves cv. Arbequina were collected at Melipilla (Chile, May 2015). Inulin (IN) Raftilina HP (DP > 23) and maltodextrin (MD) (DE = 12–20) were purchased in Quimatic and Inducorn (Chile), respectively. Hydroxytyrosol (HT), lipase (from porcine pancreas, L3126, 100–500 AU/mg protein), pepsin (from porcine pancreas, P6867, 3200–4500 AU/mg protein), bile salts (B8756, Fluka) were purchased from Sigma-Aldrich (St. Louis, MO, USA), and oleuropein (OE) (purity ≥ 90%) from Extrasynthese (France).

Microparticles preparation

Results and discussion

Olive leaves extract (OLE) was encapsulated in MD and IN, in order to study the evolution of the oleuropein (OE) during in vitro simulated gastrointestinal digestion.

Conclusions

The encapsulation of the OLE allowed the protection of OE from gastrointestinal conditions, since OE bioaccessibility was several times higher in both OLE–MD (15%) and OLE–IN (12%) than in non-encapsulated sample (1.5%). However, the structural features of the biopolymers influenced the evolution of OE during gastrointestinal digestion, mainly the release-degradation mechanism, as evidenced by the statistically higher bioaccessibility reached using MD compared with IN, associated quiet possibly

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.

Acknowledgements

ACT project Grant No. 1105/2012 (CONICYT, Chile), CYTED No. 415RT0495, and CONICYT scholarship No. 21151673.

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