Determination of carbohydrates in foods

Write 3 methods to determine carbohydrate content in foods

Answer explanation

•Chromatographic methods.

  -Thin layer chromatography (TLC).

-Gas chromatography (GC).

-High-performance liquid chromatography (HPLC).

•Chemical methods.

-Gravimetric method.

-Colorimetric or fotometric methods.

-Titration method.

•Physical methods

-Polarimetry.

-Refractive index.

-Infrared spectroscopy.

-Density.

•Enzymatic methods.

What is the principle of thin-layer chromatography?

Answer explanation

Separation of carbohydrates depends on their affinity towards stationary phase and the mobile phase.

The compounds under the influence of the mobile phase (driven by capillary action) travel over the surface of the stationary phase (thin layer of silica gel coated). During this movement, the compounds with higher affinity to stationary phase travel slowly while the other travel faster achieving the separation of the mixture.

What are the limitations of gas chromatography for the analysis of carbohydrates in foods?

Answer explanation

The main limitations due to the low volatility of carbohydrates are:

- GC is generally limited to the analysis of low molecular weight carbohydrates.

• Carbohydrate derivatization is required because they must be converted to volatile derivatives before analysis by GC

What is the principle of enzymatic methods used to determine carbohydrates in foods?

Answer explanation

The principle of enzymatic methods used to determine carbohydrates relies on the ability of enzymes to catalyze specific reactions. The concentration of the end product of the enzyme-catalyzed reaction are used to determine carbohydrate concentration

What is the principle of polarimetry for the measurement of sugars in foods and beverages?

Answer explanation

•This method depend on that carbohydrate molecules contain an asymmetric carbon atom which can rotate plane polarized light.

•The concentration of the carbohydrate molecules in the sample is proportional to the rotational capacity of each sugar and can be determined by a calibration curve.