Pre-emulsified Citral System

Citral (C₁₀H₁₆O), a natural monoterpene aldehyde compound, is widely found in the essential oils of plants such as Cymbopogon citratus, Melissa officinalis and Litsea cubeba. It serves as the primary volatile component responsible for the characteristic lemon aroma of these botanicals.

Current studies have demonstrated that citral exhibits notable biological activities including antibacterial, anti-inflammatory and anti-tumor effects, showing promising application potential in food preservation, pharmaceutical preparations, cosmetics and green agriculture. Nevertheless, the molecular structure of citral contains conjugated double bonds and aldehyde groups, resulting in poor chemical stability. Furthermore, its low polarity and limited water solubility (approximately 0.45 g/L at 25 °C) severely restrict its bioavailability and field application performance in practical use. Accordingly, developing efficient and stable aqueous delivery systems has become a key scientific challenge for citral application research.

The fabrication of a citral self-emulsifying system can improve citral stability to a certain extent and greatly enhance its water dispersibility. Using food-grade polyglycerol fatty acid esters as the primary emulsifier together with co-emulsifiers such as glycerol, a citral self-emulsifying delivery system (SEDS) can be successfully prepared via the low-energy emulsification method.

The system is a homogeneous, transparent pale yellow free-flowing liquid with a citral loading capacity exceeding 10% (w/w). Stability tests reveal no phase separation after 30 days of storage at room temperature, confirming excellent storage stability.

The polyglycerol fatty acid esters adopted in the formulation are food-grade raw materials complying with GB 1886.178-2016 National Food Safety Standard – Food Additive: Polyglycerol Fatty Acid Esters and GB 2760-2024 National Food Safety Standard – Standards for Use of Food Additives. All applied co-emulsifiers are also food-grade.

In practical applications, upon dilution in the aqueous phase with gentle stirring, this self-emulsifying system can spontaneously form a semi-transparent oil-in-water (O/W) emulsion with uniform particle sizes to meet diverse application requirements.

Citral has been classified as Generally Recognized As Safe (GRAS) by the U.S. Food and Drug Administration (FDA), granting it great application value in functional foods and natural preservatives. In the cosmetic industry, citral is mainly used as a fragrance ingredient, while its biological activity also enables important applications in functional skincare products. The self-emulsifying system improves the spreadability and permeability of citral on the skin surface, facilitating its penetration through the stratum corneum into the deep epidermis to exert antioxidant and photoprotective effects more efficiently. In addition, the self-emulsifying system reduces citral volatility and extends its residence time on the skin, thus boosting skincare efficacy.

Featuring simple preparation procedures and low energy consumption, this self-emulsifying system effectively addresses the technical limitations of poor water dispersibility and insufficient stability of citral. It holds broad application prospects in functional foods, cosmetics and green agriculture.

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