How to measure the water content in pasta

05-Feb-2010 - Last updated on 12-Feb-2024 at 15:06 GMT

The water content of pasta can be determined by volumetric Karl Fischer titration, a technique that is commonly used in the analysis of food, pharmaceuticals and chemicals.

The water content of pasta in food production is important. Pasta with a low water content of about 10% can be stored for many years, whereas pasta containing much more than 12% of moisture has a considerably shortened shelf-life as it can become musty and mouldy.

What is volumetric Karl Fischer titration?

Volumetric Karl Fischer titration is a widely used technique to determine the precise water content in various substances. Named after the German chemist Karl Fischer who developed the method in the 1930s, this titration method has become the gold standard in moisture analysis due to its sensitivity and accuracy. The basic principle involves the reaction between water and a specialised reagent, typically iodine, sulfur dioxide, and a base. The reaction takes place in a solvent medium, usually a mixture of methanol and an appropriate base. The titration process is carried out by titrating the sample with the Karl Fischer reagent until all the water is consumed in the reaction. The endpoint is determined by a colour change indicator, indicating the precise point at which the water content in the sample has been fully neutralised.

How to measure the water content of pasta

Advancements in instrumentation have led to automated titration systems, improving efficiency and reducing human error in the analysis process. The 841 Titrando has the sophisticated control algorithm of the Titrando, which has been adapted to the characteristics of the Karl Fischer reaction and guarantees precise results.

Prior to analysis, the pasta is ground up as finely as possible in a cooled laboratory mill. As the sample could heat up during grinding (resulting in water loss), cooling is crucial for correct results. Extraction of the water from the powdery sample is accelerated by adding formamide and working at 50°C. This considerably shortens the time required for the Karl Fischer titration.

You can choose between a polarised alternating current or a defined voltage to be applied to the electrode. Both working modes promise to yield fast and precise results.