Amorphous Content Determination

Quantification of amorphous content in materials is an essential analysis method in pharma as well as in food research. Processing steps such as milling may create or increase the amorphous content in a predominantly crystalline powder. The degree of crystallinity plays a major role in the efficiency of drug delivery and physical stability. The interaction of water with the amorphous parts of a partial amorphous powder significantly influences the solid properties. Amorphous materials can adsorb more water than crystalline materials. Upon (re)crystallisation, the adsorbed water becomes available for the interaction with other constituents in a formulation. Quantification of the amorphous content, or the degree of disorder in crystalline powders, therefore is of special interest for pharmaceutical applications and in the field of food research. Here, DVS measurements are a sensitive method for the quantification and investigation of the crystallization kinetics of amorphous components.

Application Notes

Amorphous lactose in the pharmaceutical industry

Lactose powders are frequently used in pharmaceutical products. During the process of powder production as well as the subsequent processing to the final product, operations such as drying, milling or compaction often result in the formation of amorphous lactose.
Control and quantification of the amorphous content is of high interest in pharmaceutical research since even low amorphous amounts can lead to substantial changes of the product with respect to processing properties, physical and chemical stability and efficacy of drugs. This is attributed to the high hygroscopicity of the amorphous phase and its high water-binding capacity. Under unfavorable ambient conditions, this induces uncontrolled recrystallization.
Application Note 20-05 and White Paper 20-01 demonstrate the applicability of dynamic water vapor sorption analysis for the quantitative determination of amorphous lactose. A method for the evaluation of the measurement data and the generation of the calibration curve is presented.

Amorphous lactose in food

Milk- and milk based powdered products are used in many processed dry foods such as infant formulas, sweets, baked goods, sports nutrition or instant sauces and soups. Lactose, as sugar component of milk, partially changes to an amorphous state during production or processing instead of crystallizing. The high moisture sorption affinity of amorphous lactose favors uncontrolled crystallization. As a result, even small amounts of amorphous lactose can have a great influence on the processing properties of the product, such as the rheological properties of chocolate. The crystallization of amorphous lactose in the end product might lead to the formation of lumps, for example, and thus have a negative influence on handling and sensory quality. Therefore, knowledge of the amorphous portion is important in order to adapt products and processes specifically.
Application Note 20-01 and White Paper 20-01 show a method for determining the amorphous fraction of lactose in food products by means of DVS and explain the evaluation of the obtained results.

Amorphous fractions in sucrose and sucrose containing model food systems

Amorphous sucrose is often formed during processing of sucrose and sucrose containing food mixtures. The hygroscopicity of the amorphous parts favors the sorption of water vapor from the ambient which results in uncontrolled crystallization. The associated product changes, such as reduced flowability, caking and sensory characteristics lead to a loss of product quality. Therefore, investigation of the crystallization kinetics and and quantification the amorphous content is important to be able to draw conclusion on the product stability and performance. The Application Note 20-02 and the White paper 20-02 present a method for the determination of amorphous fractions in sucrose and sucrose containing food systems. A method for establishing a calibration curve as well as the influence of further ingredients on sucrose crystallization is demonstrated with the help of model food systems.

Literature references for amorphous content determination with the Proumid DVS instruments

Jasper Vollenbroek, et al. “Determination of low levels of amorphous content in inhalation grade lactose by moisture sorption isotherms.” International journal of pharmaceutics 395, 62-70, 2010. DOI

Matthias Gorny, et al. “Quantifying the degree of disorder in micronized salbutamol sulfate using moisture sorption analysis.” Drug development and industrial pharmacy 33, 235-243, 2007. DOI

Ronja Wittmann, Amorphe Laktose – Untersuchungen zur Quantifizierung und zum Einfluss auf die Stabilität von Pulvermischungen zur Inhalation, Dissertation Christian-Albrechts-Universität, Kiel, 2014. Link

Wolfgang Danzl and Gottfried Ziegleder. “Untersuchung der Kristallisation amorpher Lactose in Milchpulver anhand Dynamischer Wasserdampfsorption.” Chemie Ingenieur Technik 80, 351-357, 2008. DOI