Traditional moisture analyzers
Traditional moisture balances use the gravimetric moisture measurement principle, also referred to as thermogravimetric or loss on drying (lod). A moisture analyzer is used for measuring moisture in most products including grains, pharmaceuticals, sludge and chemicals. The amount of moisture in a food product can greatly affect perceived quality or profit.
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Moisture balances with gravimetric moisture measurement rely on sample weight to determine moisture content. With the beginning of each measurement the sample is weighed with a precision weighing scale. During the measurement process the sample is heated, dried and weighed repeatedly in sample pans.
The decrease in moisture is shown as weight change on the moisture analyzer display. The sample’s weight after the drying process concluded is compared against the sample’s weight before drying. In addition, the weights recorded during the drying process are taken into account and a final moisture content or ratio for the material sample is obtained. Moisture balances provide results after approximately 15 to 90 minutes. The actual drying time depends on the moisture content and size of the respective sample.
Go beyond the specifications to find the right moisture analyzer for your food product
Trying to pick the perfect moisture analyzer out of the many options on the market? It can be daunting to choose the best moisture analyzer model for your food industry application. While you don’t want to ignore the specifications on manufacturer’s data sheets, focusing too much on the numbers may prevent you from seeing the whole picture. Here are some things you may want to consider:
- Speed—the value of a fast measurement goes beyond simple convenience. Faster instruments reduce bottlenecks, delays, and logistical snarls. And the faster the instrument, the fewer you’ll need to get your metrics.
- Precision/Accuracy—precision and accuracy claims are rampant. How do you tell the real from the hype?
- Ease of use—how much training is needed to run the moisture analyzer? You need to pick a moisture analyzer that gives repeatable results to different users in different locations.
- Sample preparation—does the instrument require different treatment for different samples? The best moisture analyzers achieve the same performance regardless of sample type.
- Effect of analysis—does the instrument destroy the sample as part of the measurement process? When the sample is changed as part of the analysis, the result may be affected.
- Data management—how do you get metrics to the right people as quickly as possible? Some instruments streamline both the measurement workflow and the reporting process.
- Audit verifications—You need to know—and prove—that your instrument is measuring correctly. The best instruments are approved by standards bodies and based on sound science.
- Uptime, service, and support—there’s no point saving money on the purchase if you have to spend it later servicing and replacing a cheap instrument. Reliability and support are a critical part of the purchase decision.
Why are some moisture analyzers 10 times faster? Am I sacrificing anything with a fast measurement?
It’s often a trade-off between speed and accuracy. The most accurate moisture measurement is low-temperature oven loss-on-drying. It’s simple, old school—and can take anywhere from several hours to several days. Some of the best moisture meters use strategies to get faster measurements. Do those involve higher heats? Predictive software? Part of evaluating the moisture analyzer is determining the robustness and accuracy/precision of these strategies.
Which precision/accuracy numbers should I believe? Does it matter?
Accuracy is determined by benchmarking an instrument against samples with a known and accepted standard value. Moisture content doesn’t have a proper zero (there is no such thing as a sample that contains no water). Specs for moisture meters should only report on precision—the ability of the instrument to consistently read the same sample at the same moisture content. Since accuracy and precision are often confused in non-scientific contexts, many moisture analyzer descriptions and spec sheets may use these terms interchangeably.
Does it matter if the moisture analyzer damages or destroys the sample?
You may not care if your cookies become toast, but it could matter to your results. When samples are heated at high temperatures to drive off water, more than water can be driven off. This results in an overestimate of moisture content.
How does the moisture analyzer get a measurement?
Many moisture analyzers heat a sample quickly at high heat to drive off water. Then the instruments use a model of the sample to guess what amount of water would be driven off if the sample were dried in an oven for a longer period at low temperatures. It’s important to ask what the moisture analyzer is actually measuring, how it gets the measurement, and how confident you are in the answer.
Does sample type matter?
Decide whether you can tolerate the need to prepare different samples differently or whether you prefer an instrument that simply takes the reading of whatever sample you put in the sample chamber.
Which moisture analyzer works best in the lab?
Consider the form factor. Solid, reliable bench-top instruments can be workhorses in the lab. Consider repair rates, build quality, and the costs and hassles involved in service and support.
Which moisture analyzer works best for food production?
Production needs a solid, reliable instrument that delivers quick moisture analysis at the line. A production moisture analyzer must be rapid, reliable, and repeatable. Many are. But what too many production moisture analyzers lack is good precision. A fast moisture analyzer that doesn’t deliver on precision means that production needs wide safety margins. This limits your ability to deliver on process and yield improvements.
How do I calibrate the device? What standards should I use? What do auditors expect to see?
Whether you’re taking measurements for internal audits or 3rd party/Government audits, make sure you can calibrate to a known standard to prove that your measurements are what they claim to be. Look for calibration and annual maintenance programs that are reasonably priced and low-hassle.