Effects of Ethanol to Water Ratio in Feed Solution on the Crystallinity of Spray-Dried Lactose

Abstract

In the present study, the effects of ethanol to water ratio in feed solution on the physical properties of spray-dried alpha-lactose monohydrate were evaluated. Crystallinity of the spray-dried lactose was determined by isothermal microcalorimetry (IMC) and by differential scanning calorimetry (DSC). Water content of the spray-dried lactose was determined by thermogravimetric analysis and the surface area was evaluated by Brunauer, Emmett, and Teller (BET) method. The crystallinity of spray-dried lactose varied from 0% to 100%, depending on the ratio of ethanol to water in the feed solution. Lactose spray dried from pure ethanol was 100% crystalline and contained hydrate water. Lactose spray dried from pure water was 100% amorphous. The feed solution substantially affected the ratio of surface water to hydrate water, as the content of surface water increased and hydrate water decreased, while the crystallinity of spray-dried lactose decreased. Surface area of the spray-dried lactose increased as a function of amorphous content.

The effect of temperature on the crystallinity of lactose powders produced by spray drying

“…The results of Harjunen et al (2002) suggest that different solvents in the feed may affect the degree of crystallinity in the powder products, possibly due to different solubilities in the solvent and to the different glass-transition temperatures for the solvent affecting the glass-transition temperatures in the drying droplets, where the glasstransition temperatures are predicted to affect the crystallization rate, according to the Williams-Landel-Ferry theory (1955). The flow rate of the liquid feed and the feed concentration are shown to affect the degree of product crystallinity in the results of Chidavaenzi et al (1997), possibly due to different concentrations of solid material in the droplets being dried and to different drying rates.…”

Particle crystallization during spray drying in humid air

“…Most of the solid powdered lactose produced from spray drying has been found to be amorphous (Briggner et al, 1994;Faldt and Bergenstahl, 1994;White and Cakebread, 1966;King, 1965). Harjunen et al (2002) used ethanol to crystallize lactose, through exploiting the lower solubility of lactose in ethanol and the effect of ethanol in lowering the glass-transition temperature of the mixtures. However, many pharmaceutical companies would like to avoid using ethanol to crystallize lactose because of the possibility of leaving residues of ethanol in the final processed product.…”

Lactose characteristics and the generation of the aerosol

“…Lactose solution spray-dried from pure water is 100% amorphous, and the particles are spherical and small (<10 μm). Moreover, the feed solution substantially affects the ratio of surface water to hydrate water because the content of surface water increases and hydrate water decreases, while the crystallinity of spray-dried lactose decreases [74].…”