Elsevier

Food Chemistry

Volume 386, 30 August 2022, 132671
Food Chemistry

Palmitoylethanolamide gels edible oils

https://doi.org/10.1016/j.foodchem.2022.132671Get rights and content

Highlights

  • Palmitoylethanolamide (PEA), an endogenous molecule, gels edible oils at conc. of 1 wt%

  • The corresponding gels have elastic moduli sufficiently high to texture lipid phases.

  • In the gel state, PEA forms solid lamellar particles connected into a 3D network.

  • The c-T PEA/rapeseed oil phase diagram was mapped.

  • The sol-to-gel transitions and the melting of the solid particles are distinct.

Abstract

Palmitoylethanolamide (PEA) is an endogenous compound with no adverse effect for oral intakes of a gram per day. We show that PEA gels edible oils at concentrations as low as 0.5 wt%. The elastic moduli values of the formed gels are 1400 Pa at 1 wt% and 9000 Pa at 2 wt%. The study of the gels by cryo-SEM, optical microscopy and WAXS show that PEA forms lamellar solid aggregates with widths of several tens of micrometers. Upon heating, the sample shows two transitions. The first one is the gel-to-sol transition, observed by rheology and defined by the switch from a solid to a liquid behavior. During this transition, the solid particles remain but do no longer form a network. The second transition, observed at higher temperature by DSC corresponds to the melting of the solid particles.

Introduction

Saturated and trans unsaturated fats are a public health issue because they represent a risk factor for cardiovascular diseases (Castelli et al., 1986, Martin et al., 1986, Hu et al., 2001, Mozaffarian et al., 2006, Brouwer et al., 2010, Clifton and Keogh, 2017). Public health authorities try to reduce their intake and tend to render the labelling of trans fat compulsory. Supported by this increasingly strengthening regulations, much research is now devoted to find replacement products of these solid fats. However, these fats play a major role to texture the food products: they form a network of microcrystals that endow the lipid phases with their mechanical properties. The sought substitution products should provide similar rheological properties. In this context, organogelators have gained increasing interest. These compounds self-associate in organic solvents to form 3D networks, which results in the formation of gels at mass fraction of a few percent. Gels made of such organogelators and vegetal liquid oils, comprising mainly cis-unsaturated acids and healthier, constitute good substitution products of solid fats (Scharfe and Flöter, 2020, Wesdorp et al., 2014, Zetzl and Marangoni, 2014). A few compounds are known for their ability to form edible oleogels: waxes (Toro-Vazquez et al., 2007, Dassanayake et al., 2009, Hwang et al., 2012), mixtures fatty alcohol and fatty acid (Gandolfo, Bot & Flöter, 2004), 12-hydroxystearic acid (12-HSA) (Elliger et al., 1972, Rogers, 2009, Rogers and Marangoni, 2008), mixtures of γ-oryzanol and sitosterol (Bot & Agterof, 2006) and ceramides (Rogers, Wright & Marangoni, 2009).

In this paper, we explore the possibility to form gels from edible oils and palmitoylethanolamide (PEA, Fig. 1). This simple molecule is endogenous, present in the mammalian brains, liver and muscles (Bachur, Masek, Melmon & Udenfriend, 1965). It was shown to have anti-inflammatory and analgesic properties (Bortolotti et al., 2012, Kuehl et al., 1957). In oral uptake by rats, it has a no effect level up to 1000 mg/body wt/day (Nestmann, 2017). This high level makes them interesting candidates to gel edible oils, especially if the concentration required to form a gel is a few weight percent. In the present contribution, we have explored the gelation ability of PEA was investigated in different solvents, including vegetable oils and found that it can form gels in the latter at concentration below 1 wt%. We have studied in details the gels of PEA in rapeseed oil. We have studied the transitions in this system by microDSC, turbidimetry and rheology and we have mapped the c-T binary phase diagram. Finally, the structure of the oleogels were investigated by scanning electron microscopy and FTIR.

Section snippets

Materials

Rapeseed Oil (Vita D’or), Olive oil (Carrefour) and Safflower oil (Mon-droguiste) were purchased in a local grocery shop. All the oils were refined. Palmitoyl chloride was purchased from Alfa Aesar (Thermo Fischer Scientific) and hydroxybenzotriazole from Acros Organics (Thermo Fischer Scientific). Ethanolamine was purchased from Sigma Aldrich. EDAC was purchased from Apollo Scientific.

Palmitoylethanolamide

A solution of palmitic acid (2.60 g, 10.12 mmol), hydroxybenzotriazole (140 mg, 1.01 mmol) and ethanolamine

Solubility and gelation

The structure of the studied compound is depicted in Fig. 1. PEA is able to form gels in alkanes (hexane, cyclohexane, trans-decalin and in several edible oils for wt. fraction of 0.5%. or higher: rapeseed, olive and safflower oil. At room temperature, PEA is insoluble in the oils; it is fully solubilized when the mixture is heated. When the solution is cooled back at room temperature, the gel forms. These gels are turbid and are stable for months. In this work, rapeseed oil was chosen for the

Conclusion

We have showed that PEA, a natural molecule well studied for its biological properties, is able to form stable gels in a variety of solvents, especially in rapeseed oil where, its binary phase diagram was established for a decade of concentration upon heating. The gel is made of large lamellar crystallites forming a network in the mixture and endowing it with its mechanical properties. These new organogels are of interest for food or cosmetics applications. The phase diagram shows a gap between

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

The facility of polymer characterization is acknowledged for the use of the UV and FTIR spectrometers. Anaïs de Maria is acknowledged for the FTIR measurements. Mélanie Legros is acknowledged for her help with microDSC. The electron microscopy facility and Marc Schmutz are acknowledged for their help. Thanks to Jean-Philippe Lamps for his help with syntheses. Guillaume Fleith is acknowledged for WAXS measurements. Funding This work was funded by the Institut Carnot MICA (Project Oleogel). D. S.

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