# Cellulose as a Delivery System of Raspberry Juice Volatiles and Their Stability
## 1 Introduction  
Flavor is one of the most important quality attributes of fruit products composed of a complex mixture of volatile organic compounds [1]. Volatile organic compounds are organic molecules with appreciable vapor pressure at ordinary room temperature. They are usually small molecules with a molecular weight lower than 300 Daltons. People often associate scents with volatiles that can be perceived by the human nose and have a pleasant smell and flavor [2]. Raspberries (_Rubus ideas_ L.) are a member of the Rosaceae family which red fruits possess a sweet but tart flavor. Their typical flavor makes these fruits easily recognizable and appreciated [3] and it is caused by a complex combination of hundreds of volatile compounds [4]. The major classes of compounds include aliphatic and aromatic hydrocarbons, aldehydes, ketones, alcohols, esters, C13-norisoprenoids, monoterpenes and sesquiterpenenes [5]. Flavor has become an essential characteristic for food developers. In the marketplace there is a growing demand for reduced use of artificial preparations thus natural flavor preparations are getting more attention in the food industry. Those preparations can contribute to a variety of foods, restore the flavoring lost during processing and allow the development of new products with novel tastes. Manufacturing processes, packaging, storage conditions and ingredients in foods often cause modifications and loss of flavor compounds and/or production of off-flavor components [6]. To limit flavor degradation or loss during processing and storage, it is beneficial to encapsulate volatilecompounds prior to use in foods or beverages. Encapsulation refers to techniques by which a material is coated within another material forming a protective shell or wall [7,8]. The most common wall materials are carbohydrates (e.g., maltodext, modified starches, gum acacia etc. ), proteins (e.g., gelatin or whey protein) or combinations of these materials. Several literature reviews detail the various encapsulation methods along with their respective strengths and weaknesses [9, 10, 11]. Encapsulation of flavors has been attempted and commercialized using many different methods such as spray drying, spray chilling or spray cooling, extrusion, freeze-drying, coaervation and molecular inclusion [8]. Freeze-drying is one of the most commonly used encapsulation techniques, especially for drying of thermosensitive substances that are unstable in aqueous solutions. The nature of delivery systems varies and it has a huge impact on the entrapment of volatiles during drying. This effect can be attributed to physical entrapment of volatiles within the matrix used (texture-specific effect) or to the binding to the polymer present in the matrix (agent-specific effect). As the result volatile molecule interactions with the matrix, which mainly involve binding, adsorption, complexation and encapsulation, are of critical importance, as well as the physicochemical properties of volatiles (like hydrophobicity, pressure, solubility and structure) [12, 13, 14, 15, 16]. Incorporation of small amounts of flavors into foods can influence the final quality of the product, cost, and consumer satisfaction. The food industry is continuously developing ingredients, processing methods, and packaging materials to improve flavor preservation and delivery [17]. The ability of carbohydrates to bind flavors is complemented by their diversity, low cost, and widespread use in foods and makes them the preferred choice for encapsulation [18,19]. Through drying, retention of volatiles on carbohydrates is a complex phenomenon that depends on several factors. These include the chemical and physical properties of the carbohydrates as well as the volatile compounds such as molecular weight and structure, stereochemistry and other characteristics which are related to different diffusion and sorption within the microstructure of the encapsulation material [15, 20, 21, 22, 23]. Retention of some native compounds after drying can be due to their low volatility.