Moisture content, as we have pointed out in many of our posts, is important for a variety of reasons, many of which have to do with quality control, product shelf life and fair pricing. Controlling moisture content can occur at several points along the processing line and usually involves the use of drying ovens, some of which are equipped with moisture sensing devices to reduce the percentage of moisture to target levels. Moisture levels are set by industry and trade associations, and by government agencies. It is up to manufacturers to verify moisture content.
Picking up on our opening sentence, an example of moisture’s effect on quality is exemplified by products as basic as sugar, table salt and bagged cement. All three are hygroscopic – exhibiting a tendency to absorb moisture. A target moisture standard for sugar is 11.9%, salt 4.9% and cement 0.8%. We all know what happens when these products are subjected to high humidity.
Product shelf life of dried vegetables, for example, is highly dependent on proper moisture content to avoid spoilage. At the other end of the scale, too much moisture means consumers are paying for water instead of the desired product. This can occur when purchasing meat and poultry. That’s why some packagers will indicate the amount of water retained or absorbed from processing the food.
It also works the other way. Processors or resellers marketing by weight will actually deliver more product if moisture content is too low.
Quality Control with a Halogen Moisture Analyzer
Benchtop halogen moisture analyzers such as the 400-watt Kern MLB 50-3N are excellent quality control tools to determine that bulk drying ovens are operating properly. Testing is quick and simple to accomplish. Moisture tests should be done right after the product exits the drying oven and before it is packaged. If results are not on spec, immediate corrective measures can be taken.
The MLB moisture balance operates on the thermogravimetric principle also called loss of weight on drying. It consists of the halogen heater mounted on a precision analytical balance.
Specific testing procedures depend on the product itself and guidelines promulgated by government agencies or industry trade associations. In summary, however, testing is accomplished by
- Programming the moisture analyzer based on what is being analyzed. Parameters include temperature, drying profile and shut-off criteria. The latter can be manual, at a set time period or when a constant weight is reached – that is no more moisture is being given off.
- Placing a sample pan on the sample pan holder and taring the balance
- Carefully spreading the correct sample weight on the pan. The balance records the weight.
- Closing the lid, which automatically starts the analysis
At the end of the cycle data are displayed on the control panel and can be recorded to a PC or printer for record keeping.
Operating and maintenance procedures are provided for the MLB 50-3N moisture analyzers as well as other models in the Tovatech product line. For a more detailed look at these precision devices please visit our post on how to set up a moisture analyzer.
Please feel free to contact the weighing and measuring professionals at Tovatech for additional details on moisture balances and other laboratory equipment.