Flavor droplets, encapsulated

In order to observe encapsulated flavor droplets (emulsion) inside a spray-dried particle, ethyl-n-butyrate was used as a model flavor. Nile red was dissolved in ethyl-n-butyrate and used as a fluorescein probe of the oil phase (ethyl-n-butyrate emulsion) of the solution. The labeled flavor was added to the carrier solution and was emulsified. 

Fig. 6.12 CLSM pictures of the morphology and the arrangement of encapsulated flavor droplets in the spray-dried powder merges of transmitted images with (a) CLSM images for sodium fluorescence in green color and for Nile Red in red color, (b) He-Ne laser CLSM images...

The photos of Fig. 6.12 visualize in a non-destructive manner the distribution of emulsion flavor droplets (red color) over the cross-section of the spray-dried powder and the internal morphology of the product (i.e., the presence, or not, of a vacuole). Therefore, they show that the CLSM is a new valuable tool for studying and observing the encapsulated flavor. The technique can even be applied to study the release characteristics of flavor from the powder in real time (Yoshii et al., 2007). 

A recent study has been performed on various spray dried orange flavors(20% oil fixed in the powder) encapsulated on various Acacia gums and on mixtures of Acacia gums and malto-dextrins. The aromas in powder were tested by chromatography and then examined by electronic microscopy. This clearly shows the regular and uniform film covering each particle 10 to 40 microns in diameter. Prints of broken particles reveal numerous oil droplets (1 micron in diameter) spread in a gum nucleus. Protection of the oil phase then becomes fully effective. 

To our knowledge, simple coacervation has essentially remained a technology described by academics and used for research rather than in pharmaceutical industry. Green first demonstrated the microencapsula-tion of oil droplets by simple coacervation of gelatin. In this study, gelatin coacervation was induced by sodium or ammonium sulfate. Since then, simple coacervation has been used to encapsulate foods, flavors, and pharmaceuticals. ... 

Another area of interest to optimize the encapsulation efficiency of food flavors and oils by SD is the submicronization of the droplets oil of the emulsion. It has been well documented that emulsion droplet size has a pronounced effect on the encapsulation efficiency of different core materials by SD (Jafari et al., 2008). The findings clearly show that reducing emulsion size can result in encapsulated powders with higher retention of volatiles and lower content of unencapsulated oil at the surface of powder particles. The presence of oil on the surface of the powder particles is the most undesirable property of encapsulated powders, and it has been pointed out as a frequent problem with the quality of spray-dried products. This surface oil not only deteriorates the wettability and dispersability of the powder, but it is also readily susceptible to oxidation and to the development of rancidity. 

Much of the work in this area has been done in emulsions having a droplet size of more than 1 pm, and the application of submicron (nano) emulsions in encapsulation of oils and flavors is relatively new in the literature. Some works have been carried out to determine the influence of submicron emulsions produced by different emulsification methods on encapsulation efficiency and to investigate the encapsulated powder properties after SD for different emulsion droplet sizes and surfactants. The process has been referred to as nanoparticle encapsulation since a core material in nanosize range is encapsulated into a matrix of micron-sized powder particles (Jafari et al., 2008). This area of research is developing. Some patents were filed in the past describing microemulsion formulations applied to flavor protection (Chung et al., 1994 Chmiel et al., 1997) and applications in flavored carbonated beverages (Wolf and Havekotte, 1989). However, there is no clear evidence on how submicron or nanoemulsions can improve the encapsulation efficiency and stability of food flavors and oils into spray-dried powders. 

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