## 1 Introduction  
Polyphenols are a diverse group of naturally occurring compounds found in fruits, but in other parts of plants, they are widely known for their antioxidant, anti-inflammatory, antimicrobial, and other bioactivities. As bioactive compounds, polyphenols have gained significant attention due to their potential health benefits and protective effects against non-communicable chronic diseases [1, 2]. Citrus fruit is a rich source of polyphenols (phenolicacids, flavanones, flavanol, and flavones) [3]. Citrus fruit processing generates a significant number of byproducts, including peels, pulp, and rag, which are usually discarded. Despite the processing conditions, these byproducts are rich in polyphenols, which present an opportunity for their utilization. Transforming these byproducts into new products or materials both addresses environmental issues and produces new economic value [4,5]. Stability and bioavailability are recognized as one of the main challenges in utilizing polyphenols delivered from industry byproducts. Some phenolic compounds can easily degrade when exposed to elevated temperature, light, oxygen, and other non-desirable environmental conditions [6,7]. An increased number of authors recognized encapsulation as a possible solution to enhance the stability and preserve the bioactivity of polyphenol compounds [5,8,9,10]. Moreover, different combinations and modifications of encapsulating agents (coating) enable controlled, targeted, or postponed release of polyphenols from microcapsules or mask the unpleasant bitter and as stringent taste [11,12,13]. On top of that, our previous results [12] showed that encapsulation using spray or freeze-drying can enhance the solubility and stability of phenolic compounds (hesperidin) and therefore broaden applications of phenolic compounds in food, food supplements, or pharmaceuticals. Many well-known techniques can serve as encapsulation techniques including spray drying, particle from gas-saturated solution processes, fluidized bed coating, coacervation, and freeze-drying [13,14,15]. Between various encapsulation techniques, freeze-drying has been recognized for effectively preserving heat-sensitive compounds [16]. Freeze-drying is an encapsulation technique based on the dehydration by sublimation of a liquid and semi-liquid mixture of core and carrier material. Carrier material (encapsulant) may be selected among various natural or synthetic materials, like Maltodext, dextrins, other polysaccharides, and gums. There are several requirements for compounds to be suitable for carrier material. Some of them are the ability to form films, desirable viscosity, safety, availability, low price, biocompatibility, and biodegradability [17,18]. The key feature of freeze-drying as an encapsulation technique is its performance at low temperatures where encapsulated compounds are not exposed to high temperatures, unlike spray-drying [19]. Despite the potential benefits, there is a lack of data on the encapsulation of polyphenols derived from mandarin juice byproducts using freeze-drying. [PERSON] et al. [20] used a nanoencapsulation process to encapsulate mandarin peel polyphenols into whey protein coatings, while [PERSON] et al. [21] used the same process for the encapsulation of mandarin essential oil. In an earlier study, [PERSON] et al. [22] proved that during the encapsulation process, a synergistic effect between citrus peel extract and coating material (pectin) can occur and increase the bioaccessibility of phenolic compounds.  
The aim of this study is to address this gap by conducting the encapsulation freeze-drying process to maximize polyphenol retention and evaluate the efficiency of encapsulation. For the first time, three encapsulating agents were compared and evaluated for valorization of underutilized byproducts. By exploring this approach, the study contributes to sustainable practices within the food industry, offering a novel method to enhance the value of mandarin juice byproducts.