Starch is a natural product. In order to optimally utilize and adapt its properties, it is important to know the exact composition and influencing factors. Here you will find explanations of the terms frequently used in the analysis and modification of starch products.
Alongside amylopectin, amylose is one of the two main components of starch. In contrast to amylopectin, amylose is a largely linear polymer in which the D-glucose monomers are mainly linked to each other α-1,4-glycosidically. The amylose content influences the gelling capacity of starch, but also has an influence on film formation or the stability of starch pastes, for example. We determine the amylose content using a titration method via the iodine binding capacity.
In its granular form, starch is a semi-crystalline solid. The crystallinity differs depending on the origin. The degree and type of crystallinity can be determined using wide-angle X-ray scattering.
The lipid content can influence the processing properties of starch. Lipids can inhibit or impair the formation of starch gels and lead to a change in texture and stability in starch-based products. The lipid content is generally determined by extraction with a lipophilic solvent.
Different solubilities lead to various viscosities and stabilities. They also influence properties such as adsorption and film formation. In addition to water, organic solvents can also play a role in special applications. We determine the solubility as a function of medium, concentration, stirring intensity and temperature.
The molecular weight distribution and the average molecular weight influence, for example, viscosity, film formation and adsorption, but also the processing properties of starch in general. Knowledge of the average molecular weight and molecular weight distribution is essential in order to establish specific structure-property relationships. The special composition of starch from amylose and amylopectin (amylopectin is the largest known non-crosslinked molecule) requires special equipment to determine the molar mass distribution.
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In addition to different morphologies of the starch granules, starches of different plant origins also have different particle sizes in the range of 1 - 100 micrometers. The particle size distribution can influence the texture, stability and processing properties of starch-based products. The particle size distribution is also an important parameter for the properties of so-called nano-starches - in this case, however, on the nanometer scale. Depending on the particle size, laser diffraction or scattering methods can be used for the determination of particle sizes.
Potato starch has naturally bound phosphate. Phosphorus can also come from crosslinkers in modified starches, from phospholipids or other sources. It is important to know the phosphorus content depending on the application, as this often influences the stability, structure, gelling properties and similar properties. We can determine the phosphorus content very sensitively using optical emission spectrometry.
The protein content can influence the viscosity and the texture of starch-based products. Proteins can support the formation of gel structures and contribute to increased viscosity. The protein content can be determined via the nitrogen determination of a sample in a CHNS-O analysis.
The substitution degree and the distribution of substituents on the polymer chains can influence the gelling ability, viscosity and processing properties of starch. However, the chemical introduction of special functionalities can also produce special properties such as hydrophobic or cationic starches. Depending on the type of substituent, the degree of substitution can be determined using titrimetric methods, elemental analysis or high-resolution 13C and 1H NMR spectroscopy.
The viscosity of most starch-containing products is highly dependent on the intensity of the shear stress. In some cases the products even exhibit a time-dependent change in structure and therefore viscosity (e.g. ketchup). In order to optimally adapt starch-containing products to the individual processing procedures, it is important to determine the flow behavior precisely.
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