Quercetin (3,3′,4′,5,7-pentahydroxyflavone), a natural flavonoid originated from plant sources like onions and tea, boasts an array of biological activities encompassing anti-cancer, anti-oxidation, anti-inflammatory, and cardiovascular disease prevention properties [1,2]. Its incorporation into functional foods as a commercial dietary supplement holds promise for the prevention and treatment of various ailments. However, the inherent phenolic hydroxyl structure of quercetin imparts a robust bitterness that hinders its palatability [3]. The discernible threshold for its bitterness (1 μmol/L) was confirmed through BitterDB [4], and 33 μmol/L of quercetin was the concentration of intolerable bitterness by our test. Currently, strategies to mask this bitterness predominantly encompass the addition of spices and sweeteners, increasing solution viscosity [5], utilization of bitterness blockers and bitterness receptor inhibitors [6], encapsulation techniques [7], inclusion of cyclodextrin [8], and ion exchange methods [9]. Among these, encapsulating bitter compounds within nanoliposomes stands out as a straightforward and appealing approach to produce taste-masked bioactive nanoparticles, causing minimal disruption to the food matrix and consumer experience [10].

Nanoliposomes are microscopic spherical vesicles composed of natural or synthetic phospholipids, known for their bio-compatible, biodegradable, and non-immunologic attributes [11]. Owing to their distinctive bilayer structure, nanoliposomes serve as physical barriers between the encapsulating agents and their external environment, inhibiting the dispersion of bitter bioactive substances within the oral cavity. This, in turn, reduces their interaction with taste receptors, thus mitigating the perception of unpleasant bitterness [9,12]. However, it is worth noting that nanoliposomes are susceptible to fusion, aggregation, and leakage of their contents during storage and application [13]. To enhance their stability, surface modification of nanoliposomes is achieved through polymer coatings, including polysaccharides and proteins. In a previous study, we successfully employed protein encapsulation to mitigate the bitterness of polyphenols [12].

Polymer coating was evidenced as a valuable strategy to mask the taste [9]. Anionic polysaccharides can exert their influence on negatively charged nanoliposomes by physical adsorption [14]. It is that the surface charge of nanoliposomes affects their aggregation and stability in different manners. The zeta potentials of three anionic polysaccharide solutions of carrageenan, trehalose, and pectin were −62.67 ± 1.85 mV, −20.73 ± 1.42 mV, and −4.47 ± 0.38 mV, respectively [15]. Polysaccharides with multiple sources and varying characteristics interacted differently while coating the nanoliposomes. Our previous investigations have revealed that three anionic polysaccharides namely, carrageenan, pectin, and trehalose behaved differently. The coating of highly charged polysaccharides formed more hydrogen bonds and compacted the inner chains of lipid molecules, increasing the stiffness of the lipid membrane [15].

The primary objective of this study is to develop anionic polysaccharide-coated nanoliposomes with distinct properties to mitigate the bitterness of quercetin, ultimately facilitating its application in gelatin gummy. Initially, we assessed the bitterness of both quercetin and nanoliposomes through sensory evaluation and an electronic tongue system. Subsequently, we characterized the physical attributes of the nanoliposomes, including particle size, polydispersity Index (PDI), and zeta potential. Simultaneously, we investigated potential interactions among carrageenan, pectin, trehalose, and nanoliposomes using turbidity and fluorescence characteristics. Additionally, we monitored the environmental stability of the nanoliposomes to preserve quercetin and enable its use in food applications. The outcomes of this study aim to serve as a valuable reference for masking the taste of quercetin and enhancing its applicability within the food industry.