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Microwave Technology Optimizes Moisture and Fat Analysis

Author / Editor: Ulf Sengutta* / Dipl.-Chem. Marc Platthaus

In food production, every minute counts. Due to this fact, analytical techniques which quickly provide information about the composition of foodstuffs are the solution of choice. Read on to find out how moisture and fat analysis can be performed in three steps.

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Abb. 1: The sample, which has been pre-dried, is placed into the Oracle module for fat analysis.
Abb. 1: The sample, which has been pre-dried, is placed into the Oracle module for fat analysis.
(Source: CEM)

Moisture/solids content and fat content are important control parameters during ongoing food production and at incoming inspection. However, analysis can be time-consuming, and that causes problems. It takes hours to get the results, making rapid intervention in the production process impossible. The NMR Oracle fat analyzer in combination with a microwave dryer delivers fast, high-precision results without the need for solvents or calibration. The Oracle can analyze fat in ice cream, dairy products, cream, cheese, meat, sausage, fish, animal feed, dressings, mayonnaise, butter, margarine, sour cream, yogurt, ketchup, cookies, crackers, snacks and much more. All of these foods have one thing in common. They have an extremely high water content (often up to 70%), which in the past has made fat analysis difficult.

Keys for state-of-the-art analytical instrumentation

Faster throughput, higher speed, continuous process flows, automation and standardized product quality are characteristic features of modern production. This creates new challenges for analytical instrumentation used to support and monitor the process. The requirements profile includes active occupational safety, speed, networking capability, relocation of analysis from the lab to the production floor, rugged design (glove operation) and ease of use by semi-skilled workers. Obviously, the cost aspect is a major factor in calculating the payback period for instrumentation. Indirect analysis methods are often used to generate spectra or signals. This requires product-specific calibration which increases labor costs over a period of months [1]. CEM is a specialist supplier of process analytical instrumentation. The highly versatile Oracle fat analyzer was developed to handle a very wide range of samples. No time-consuming, product-specific calibration is needed to analyze a broad range of formulations. Immediately after installation, the Oracle is ready for daily use. The high-precision system quickly determines the fat content in food samples without calibration or solvents. Analysis with the Oracle is a three-step process:

Step 1: Dry the sample in a Smart 6 microwave dryer to remove all of the water in 2 - 3 minutes. Step 2: Place the dried sample in the NMR nuclear magnetic resonance spectrometer. Step 3: Determine the fat content of the sample in the Oracle module within 30 seconds.

All of the actions needed to operate the microwave dryer and the Oracle module take place on a touch-screen. The software was designed so that following the menu-driven work instructions is similar to using a smartphone. Complex spectra such as fat signals are processed directly by the software. With a PC workers can perform the analyses without the need for extensive training. Fat analysis using nuclear magnetic resonance spectroscopy is a reliable, versatile technique which can be used for a broad range of samples. It is a well-established method for dry samples, works without the need for toxic solvents, does not require time-consuming, product-specific calibration, delivers very fast results (in less than a minute) and is very easy to use.

Fat analysis: the sample must be dry

NMR technology for fat analysis is nothing new. It has been used for a number of years for dry samples such as nuts, chocolate and grain. However, early trials of fat analysis on very moist products such as meat & sausage, dairy products (ice cream, quark, yogurt, etc.), gourmet food, ketchup and mayonnaise were not successful. The reason was that water interfered with the fat signal. So, water must be removed from the sample priorly to fat analysis. However, drying in an oven can take several hours, making this idea unfeasible.

The logical way forward for the developers at CEM was first dry the samples in the Smart 6 microwave within 2 minutes before fat analysis. Microwave drying is the quickest drying method, and it is fast enough for process control. No calibration effort is needed for a large variety of products and product varieties at-line. The Smart 6 has been used for years as a microwave moisture/solids analysis system in various types of production. The sample is placed on special sample (glass fiber) pads and weighed on a balance which is built into the microwave dryer (see Fig. 2). The water molecules are heated in the microwave field and expelled without formation of crust on the surface which would prevent further evaporation of water.

The built-in temperature sensor provides controlled heating of the sample, minimizing the risk of sample decomposition. For high-precision moisture analysis, the microwave field must be uniform and continuously adjustable. The built-in balance constantly monitors the sample weight during the drying process and switches the dryer off when the weight no longer changes, often after only two minutes. Especially with substances for a high water content (up to 99.9%), this method is suitable for at-line process control because it is fast and accurate (precision ±0.1% dry weight). The dried sample is then placed into the NMR spectrometer (Oracle module). The sample is exposed to high-energy pulsed radiation in a magnetic field for 8 seconds.

The fat molecules emit a characteristic signal which the software directly converts into the fat content, and the value is displayed to the user. The results are not distorted by other ingredients such as sugar, salt, flavorings or preservatives. Color differences between the samples also do not affect the results, making the method suitable for general-purpose use. To make that possible, a universal calibration was carried out using a very wide variety of samples based on reference contents and reference methods. The results obtained from unknown samples are comparable with the results obtained using standard methods. As can be seen from Table 1, Oracle fat analysis produces results which are comparable with standard reference methods.

Fat analysis can be carried out directly on dry samples such as crackers, cookies, nuts, marzipan, whole milk powder, starch and baby food in the Oracle fat and moisture analysis systems.

Summary: Faster analysis increases throughput

The scope of what process control is expected to deliver has changed considerably in recent years. This is in part due to significant changes in laws and regulations. Demand has increased for analysis systems which can be operated right next to production (at-line). These applications place particular demands on safety and ease of use. Oracle fat and moisture analysis systems are the ideal choice. Skilled workers are not needed to operate the system. Fat analysis is fast and not dependent on the matrix, and the analyzer is ready to go as soon as it is installed. In contrast to organic measurement techniques, no elaborate product-specific calibration is necessary. Elimination of the need to handle acids and other solvents also enhances occupational safety. With high-speed moisture and fat analysis, food recipes can be kept very close to the allowable limits, increasing revenue generation.


[1] „Analytik im Wandel – zwischen Labor und Prozess, Mensch und Methode“, H.-D. Isengard, Kompetenzmeeting Innovationen der Prozessanalytik und Feuchtemesstechnik, May 1995, Göttingen/Germany

* U. Sengutta: CEM GmbH, 47475 Kamp-Lintfort/Germany