ARS | Publication request: Use of Microcellular Foam Particles for Encapsulation of Viscous fluids

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 30, 2008
Publication Date: September 7, 2008
Citation: Glenn, G.M., Klamczynski, A., Imam, S.H., Chiou, B., Orts, W.J., Wood, D.F. 2008. Use of Microcellular Foam Particles for Encapsulation of Viscous fluids. Abstract. 2008.

Technical Abstract: A relatively new starch product with various novel applications is a porous microcellular foam [1,2]. The foam product is made by dehydrating a starch hydrogel in a solvent such as ethanol and then removing the solvent to form a foam product [1,2]. Starch microcellular foam has very small pores and unique physical properties. One potential new use for starch microcellular foam is in supplementing diets for beneficial insects such as honeybees. A number of oils may be beneficial in rearing healthy honeybees. The large pore volume and small pore size of microcellular starch foam enable the foam to absorb and hold up to seven times its weight in oils or other liquids [3]. The purpose of the present study was to develop starch microcellular foam particles in a size range of 20 µm or less (about the size of pollin grains) that could be used in making an effective insect diet. Foam particles were made in the present study using high amylose (70%) corn starch (Hylon VII, National Starch Inc.) The process involved heating an aqueous slurry of starch (8% w/w) in a reaction vessel to 140°C for 10 min. The melt temperature was lowered to 85°C and the melt was pumped through a spray nozzle. Atomized starch spheres were collected in a solution of 90% ethanol/water. The starch spheres were equilibrated in three changes of 100% ethanol. For homogenized samples, a melt was prepared in a reaction vessel as described above. The melt was cooled to 85°C and poured into a beaker. The slurry was chilled in a refrigerator (5°C) overnight to facilitate gelation. Two volumes of ethanol were added to the gel and the contents were homogenized for 5 min to form small particles. Particle size distribution of sprayed and homogenized particles was measured using a particle size analyzer and foam microstructure was observed using Scanning Electron Microscopy (SEM). Heating conditions used in the study effectively solubilized the starch granules to the point that no granule remnants were visible. Spray and homogenization methods were both effective in producing a fraction of starch particles in the desirable size range. Typical size distribution curves showed particle sizes ranging from 3 to 100 µm. The spray technique yielded particles with a slightly higher mean value compared to the homogenized sample but differences were not significant. Some of the larger sized particles appeared to be attributable to particle agglomeration. The starch particles had an open-cell matrix with pore sizes in the submicrometer range. The porous microcellular foam beads are currently being field tested in diet formulations in honeybee colonies.