1108 JOURNAL OF FOOD SCIENCE—Vol. 67, Nr. 3, 2002 © 2002 Institute of Food Technologists Food Engineering and Physical Properties JFS: Food Engineering and Physical Properties Introduction E NCAPSULATION IS THE PROCESS BY WHICH ONE MATERI- al or mixture of materials is coated with or entrapped within another material or system. The encapsulation of flavors serves to retain the aroma in a food product during storage, protect the flavor from undesirable interactions with food, minimize flavor/ flavor interactions, guard against light-induced reactions and/or oxidation, and to effect a controlled release (Anandaraman and Reineccius 1986) Spray drying is the major process employed to produce dry flavorings. The popularity of spray drying is partially historic be- cause it was the first process used in the flavor industry to obtain encapsulated flavorings. However, the merits of the process have ensured its dominance, including availability of equipment, low process cost, wide choice of carrier solids, good retention of vola- tiles, and good stability of the finished product (Reineccius 1989). There are many types of spray dryers used in the flavor in- dustry. They differ in size, shape, and type of atomization. Dry- ing chamber shape is either conical, flat-bottomed, or box. While the conical and flat-bottomed dryers predominate, there are still a few of the box dryers in use. The flat-bottomed and box dryers accumulate dry product on the floor of the dryer, which is re- moved during the drying process by either air conveyance or me- chanical scrapers. These dryers subject the product to signifi- cantly more heat than do the coned-bottomed dryers. While for many types of dry flavorings this additional heat is insignificant, thermally labile materials may suffer from the additional heat (Masters 1985). Virtually all spray dryers used in the flavor indus- try are co-current in design, that is, product enters the dryer flow- ing in the same direction as the drying air. This results in very rapid drying and does not subject the flavoring to as much heat as would a countercurrent system. In the co-current dryer, the flavoring never exceeds the exit air temperature of the dryer (Rei- neccius 1989). Atomization of the infeed material is typically accomplished by either a single-fluid high-pressure spray nozzle or a centrifu- gal wheel. The configurations of the drying chambers used with these 2 atomization processes are quite different. A nozzle atomi- zation spray dryer is narrow and tall (tower configuration; 3:1 to 4:1 width to height ratio) as opposed to short and wide for a wheel atomization dryer (0.6:1 to 1:1 width to height ratio) (Schmidt 1973). Flavor retention is influenced by inlet and exit air tempera- tures. In general, a high enough inlet air temperature should be used to allow rapid formation of a semipermeable membrane on the droplet surface but yet not so high as to cause heat damage to the dry product or “ballooning” of the drying droplet. Balloon- ing occurs when steam is formed in the interior of the drying droplet, causing the droplet to puff. The result is a thin-walled, hollow particle that will not retain flavor compounds as well as the non-ballooned counterpart. The ballooning temperature is primarily a function of carrier material and dryer design (Thijs- sen 1972; Rulkens and Thijssen 1972). The influence of dryer exit air temperature on flavor retention is not as well documented. Retention of small soluble flavorants such as diacetyl increases with increasing exit air temperatures, probably due to the fact that the dryer air is at a lower humidity, which implies a more rap- id drying and, therefore, a better retention (Reineccius and Coulter 1969). However, the influence of dryer air temperatures appears less significant in the drying of less volatile flavorants such as orange oil (Anker and Reineccius 1988). The objective of this study was to determine the influence of type of atomization coupled with processing temperatures on the physicochemical properties of encapsulated orange oil by spray drying. Materials and Methods Emulsion Preparation and Spray Drying N-Lok â , a modified food starch (derivatized, non cross- linked)(National Starch and Chemical Co., Bridgewater, N.J., U.S.A.), was added to deionized water to obtain a 40% (w/w) sol- ids slurry (40 g of dry starch per 100 g of dispersion) and allowed to hydrate overnight. The following day, the mixture was heated to 65 °C in a water bath in order to fully dissolve the carbohy- Effects of Type of Atomization and Processing Temperatures on the Physical Properties and Stability of Spray-Dried Flavors J. FINNEY, R. BUFFO, AND G.A. REINECCIUS ABSTRACT: Type of atomization (centrifugal wheel and spray nozzle) and processing temperatures (2 different sets of inlet and exit temperatures) of spray drying were investigated for their influence on the physical proper- ties and oxidative stability of encapsulated orange oil in a modified starch matrix. The former determined particle size and surface oil, whereas the latter affected density (both absolute and bulk) and moisture content. Total oil retention did not depend on either parameter. Processing temperatures had an effect on shelf life as they influ- enced parameters that determine oxygen porosity of the matrix. Keywords: flavors, encapsulation, spray drying