Dynamic liquid film crystallization (DLFC): An additive-free strategy for spherical curcumin particles with superior powder flowability for functional foods

Abstract

Curcumin’s application in functional foods is hindered by poor aqueous solubility, low bioavailability, and irregular particle aggregation. Existing strategies often compromise food safety with additives or require harsh processing. Herein, a novel dynamic liquid film crystallization (DLFC) method was developed for green, additive-free fabrication of relatively monodisperse, spherical curcumin particles. By regulating initial concentration, bead diameter, and cyclic processing, DLFC enabled two growth-dominated pathways yielding smooth (1004 nm) and rough spherical particles. X-ray diffraction confirmed the formation of metastable Form II, distinct from raw curcumin’s Form I, accompanied by a reddish hue. DLFC particles exhibited superior powder properties (bulk density 0.55 g/cm³, angle of repose 32.8°), enhancing solubility and processability. Compared to reported techniques, DLFC features ambient pressure/temperature operation, facile tunability and scalability. This additive-free and efficient method addresses curcumin’s bioavailability challenge, providing a promising route for its valorization as a high-performance functional food ingredient and pharmaceutical formulation.

Highlights

Introduction

Curcumin, a natural polyphenolic compound extracted from the rhizome of Curcuma longa L. (turmeric) (Liu et al., 2018), has attracted substantial attention in the food industry owing to its diverse bioactivities encompassing potent antioxidant (Purushothaman et al., 2022), anti-inflammatory (Yang et al., 2017) and antimicrobial (da Silva et al., 2018) properties. Classified as a Generally Recognized as Safe (GRAS) ingredient, curcumin is extensively explored for the formulation of functional foods including fortified beverages (Hu et al., 2026), nutraceutical tablets (Pandey et al., 2018) and functional snacks (Z. Li et al., 2024), in response to the escalating consumer demand for natural health-promoting food products. Despite its promising potential, the practical application of curcumin in food systems is severely impeded by inherent physicochemical constraints. These constraints include an extremely low aqueous solubility of merely 0.6 μg/mL at 25 °C, poor bioavailability and a tendency to form irregular aggregated particles (Nguyen et al., 2026; Song et al., 2021). Such drawbacks lead to inefficient dispersion in aqueous food matrices, insufficient gastrointestinal absorption and compromised functional efficacy, thereby restricting its role as a high-performance food additive (Xu et al., 2020).

To mitigate these challenges, various particle engineering strategies have been developed for curcumin, including nanocrystallization (Bianchi et al., 2022; Castillo Henríquez et al., 2024), encapsulation in polymers or lipids (Tan et al., 2026; Thongchai & Fukngoen, 2018) and cocrystallization with co-formers (Barik et al., 2025; Nisoa et al., 2025). While these approaches can enhance solubility to a certain extent, they often present critical limitations that hinder their widespread application in the food industry. Polymer or lipid encapsulation may introduce exogenous additives that raise safety concerns or alter the sensory properties of food products (Jacob et al., 2024). Supercritical fluid-based nanonization requires high-pressure equipment, which increases production costs and limits industrial scalability (Sharma et al., 2023). Cocrystallization relies on specific co-formers that may not be food-grade or compatible with diverse food matrices (Aw et al., 2022). Traditional antisolvent crystallization (TAC) typically suffers from the absence of spatial confinement during crystal growth, leading to a broad particle size distribution and uncontrolled random aggregation. Additionally, many existing techniques generate particles with irregular morphologies and poor powder flowability, resulting in processing difficulties during food manufacturing. These difficulties include uneven blending, poor compressibility for nutraceutical tablet production and sedimentation in beverage systems (P. Li et al., 2021; Lin et al., 2024). Thus, there is an urgent demand for a green, facile and food-compatible method to prepare curcumin particles with controlled morphology, enhanced solubility and excellent processability, without compromising food safety or sensory quality.

Herein, we propose a novel dynamic liquid film crystallization (DLFC) method for the controllable preparation of submicron curcumin particles tailored for food applications. The DLFC method leverages liquid film confinement and bead-loaded cyclic crystallization to regulate supersaturation dynamics, enabling the formation of relatively monodisperse spherical particles under ambient pressure and temperature conditions. These mild processing conditions are compatible with food manufacturing and avoid thermal degradation of the bioactive curcumin molecule (Masih & Iqbal, 2022).

This study systematically investigates the effects of critical process parameters (e.g., initial concentration, bead diameter, cycle number) on the morphology, size, and crystal structure of the resulting particles. Furthermore, we elucidate the crystallization mechanism for spherical particle formation. We also quantitatively evaluate key powder properties including flowability and packing density to verify their compatibility with food processing operations. By establishing DLFC as a scalable green strategy, this work provides a promising solution to overcome the inherent limitations of curcumin, facilitating its widespread integration into high-value functional food products.

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Materials

Curcumin (purity >98%) was purchased from Shaanxi Guanchen Biotechnology Co., Ltd. Methanol, ethanol, isopropanol, and 1-propanol (purity >99.7%) were supplied by Tianjin Fuyu Fine Chemicals Co., Ltd. All chemicals were used as received without further purification. Deionized water (conductivity <0.5 μS/cm) was produced in our laboratory. Four types of spherical beads with a nominal diameter of 3–4 mm were employed as liquid film carriers: glass beads, stainless steel beads, plastic beads.

Yingchen Wang, Jiaqi Luo, Mei Ma, Mingting Yuan, Yimin Jia, Qiushuo Yu, Dynamic liquid film crystallization (DLFC): An additive-free strategy for spherical curcumin particles with superior powder flowability for functional foods, Food Chemistry, Volume 522, 2026, 150075, ISSN 0308-8146, https://doi.org/10.1016/j.foodchem.2026.150075.

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