ORIGINAL PAPER Freeze-Dried Fennel Oleoresin Products Formed by Biopolymers: Storage Stability and Characterization Charikleia Chranioti 1 & Alexia Karamberi 2 & Lamprini-Areti Tsakanika 2 & Constantina Tzia 1 Received: 10 June 2015 /Accepted: 10 July 2016 # Springer Science+Business Media New York 2016 Abstract In this work, fennel oleoresin (FO) was encapsulated through freeze drying of the so produced emulsions within dif- ferent edible biopolymeric carriers. Specifically, modified starch, maltodextrin, chitosan, and gum arabic were used as carriers both individually and in blends (binary and ternary ones). The freeze- dried FO products were characterized in terms of structure (X-ray diffraction (XRD) analysis), whereas their stability was studied by means of sorption isotherm analysis under various a w . Moreover, the formation of complexes was evaluated through Fourier transform infrared spectroscopy (FTIR) technique and ζ-potential analysis. The verification of the encapsulation process was also conducted by applying FTIR technique. Results showed that the final products presented an amorphous character, where- as the sorption isotherms could be described adequately by the Guggenheim-Anderson-de Boer (GAB) model. FTIR technique proved to be effective to confirm both the formation of com- plexes and the presence of FO into the studied carriers, verifying thus the success of the process. Keywords FTIR . Complex formation . Modified starch . Maltodextrin . Chitosan . Gum arabic Introduction Fennel oleoresin, as well as the herbal oleoresins, is suscepti- ble to light, heat, and oxygen (Shaikh et al. 2006) and there- fore needs to be encapsulated in order to be protected and used thereafter in foods. Encapsulation is, thus, a good method to prolong shelf life of herb oleoresins. A common encapsulation technique involves the preparation of an emulsion consisting of the core material and the encapsu- lation agent, which is then dried, using freeze or most commonly spray-drying technique (Lim et al. 2011). Few studies on freeze drying of flavor oil emulsions have been conducted (Kaasgaard and Keller 2010; Kaushik and Roos 2007; Lee et al. 2009; Tobitsuka et al. 2006); thus, the current understanding of freeze-drying encapsulation remains on a less solid ground than is the case of spray drying. Moreover, freeze drying, due to the absence of water and the low temperatures of the process, can lead to products of excellent quality (Calvo et al. 2010; Mimemoto et al. 2001). Therefore, the aforementioned method was selected as the drying step of the encapsulation process followed in the present study. Another parameter also very crucial for an encapsulation process is the material used as the encapsulation agent. As no single agent possesses all the properties required of an ideal one, approaches have been focused on mixing different mate- rials (Kaushik and Roos 2007). Therefore, materials with new properties can be investigated and used for biomedical and technical applications (Ludwiczak and Mucha 2010). Among the numerous materials (carbohydrate polymers, pro- teins, and lipids) available for food applications (Murugesan and Orsat 2012), gum arabic, modified starch, maltodextrin, and chitosan both plain and in combinations were studied in the present study. The abovementioned agents have already been examined in our previous studies (Chranioti and Tzia 2013, 2014a, b; * Constantina Tzia tzia@chemeng.ntua.gr 1 Laboratory of Food Chemistry and Technology, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou str., 15780 Polytechnioupoli Zografou, Athens, Greece 2 Laboratory of Inorganic and Analytical Chemistry, School of Chemical Engineering, National Technical University of Athens, Athens, Greece Food Bioprocess Technol DOI 10.1007/s11947-016-1773-3