The influence of drying methods on the stabilization of fish oil microcapsules: Comparison of spray granulation, spray drying, and freeze drying

The stability of microencapsulated fish oil prepared using various drying methods is investigated. The fish oil with ratio of 33/22, eicosapentaenoic acid (EPA):docosahexaenoic acid (DHA), is emulsified with four combinations of matrices, and emulsions are dried by spray granulation (SG), spray drying (SD), and freeze drying (FD) to produce 25% oil powders. The objective is to identify the most critical factors to determine powder stability and to further examine the superiority of the SG process compared to other drying processes. The stability is examined by measurement of peroxide values (PV) and GC-headspace propanal after 8-week's storage at room temperature (+/- 21 degrees C) The best matrices are a combination of 10% soybean soluble polysaccharide (SSPS) and 65% octenyl succinic anhydride (OSA-starch). Microencapsulation of 620 mg/g omega-3 fish oil with these matrices then dried by SG is able to produce powder having a very low propanal content and with a shelf life of 5 weeks at +/- 21 degrees C. The results indicate that microcapsules produced by SG are actually formed firstly by agglomeration of seed particles. These agglomerated particles are then covered by successive layers. The particle enlargement is determined by mechanism of the layer growth. Therefore, the SG process produces "multiple encapsulations" granules which provide maximum protection to the oil droplets. Comparison of the SG, SD, and FD processes confirms that combination of matrices, drying temperature, microcapsule morphology, and processing time are among the most critical factors governing stability. Exposure to heat is proved to be a limiting factor for drying unstable emulsion. (C) 2011 Elsevier Ltd. All rights reserved.