Product category:
Materials Testing
News Release from: Metrohm UK | Subject: Automated water analysis of foodstuffs
Edited by the Manufacturingtalk Editorial
Team on 15 July 2005
Automated water analysis of foodstuffs
The water content of foodstuffs has significant importance since it affects the physical characteristics, technological processes, microbiological stability, and shelf life of foods.
The water content of foodstuffs has significant importance since it affects the physical characteristics, technological processes, microbiological stability, and shelf life of foods, as well as having legal and economic ramifications Determination of water content is one of the most frequent analyses performed on foodstuffs
This article was originally published on Manufacturingtalk on 29 Aug 2008 at 8.00am (UK)
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Water determination methods should not only be very accurate but also fast.
There are several methods for determining water in foods with Karl Fischer (KF) moisture analysis being the preferred method within the industry.
The nature and special characteristics of each sample, as well as the chemical state of the water in it, determine the appropriate method for the water measurement.
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Bulk or free water is easy to determine using several methods.
On the other hand, the determination of tightly bound water is very difficult and can only be achieved using a limited number of methods.
Certain samples must first be pulverized before the determination to release the substances of interest." One such method is by volumetric KF in conjunction with a high speed homogeniser".
"High-frequency homogenisation is the only method that can guarantee that even plant samples are thoroughly homogenized".
"In this method the cells are disrupted and the water present inside the cells is extracted".
"Homogenisation is usually carried out externally in a dry Erlenmeyer or round-bottom flask with the addition of a suitable solvent (mostly methanol)".
"Homogenisation in the titration vessel is also possible; the mixing head is commonly used as a stirrer (the magnetic stirrer bar from the titration vessel is removed)".
"Homogenizing a sample presents a challenge in an automated system, as frequently a propeller or magnetic stirrer is not able to mix and dissolve the sample completely".
"Metrohm, as market leaders for instrumentation for Karl Fisher analysis, have designed such a system which can be completely automated, with the ability to analyse up to 100 samples at a time".
"The system incorporates the flexibility and accuracy of the Metrohm Sample Processor Instruments".
"Sample size reduction and homogenization can be carried out, for example, with the Polytron 1300 D homogenizer from Kinematica".
"To trigger the required actions, transfer commands are used to send defined three-digit numerical codes from Metrohms very own tiamo titration software to the control unit of the homogenizer".
"Not only can the instrument be switched on and off, its speed can also be set in the range 7000 _ 30,000 rpm".
"It is also possible to vary the speed of rotation within the method sequence to adapt it to the particular conditions".
"For instance, the sample can be disintegrated at 25,000 rpm with the subsequent determination taking place at 7000 rpm".
If the 786 Swing Head of the Robotic Sample Processor is equipped with the Robotic Arm then the homogenizer can even be used with multiple-row sample racks.
This means that large sample series can be processed without any problem.
Between determinations the homogenizer can be cleaned automatically by one of two methods.
The stirrer is either immersed in a special beaker containing a rinsing solution (e.g water/ethanol mixture) and switched on briefly, or cleaning can be carried out using the spray nozzles built into the titration head of the Robotic Arm.
In both cases carryover is reliably prevented and accuracy and precision is improved since the analysis is performed in the same way each and every time. Request a free brochure from Metrohm UK ...
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