Using Microwave Radiation in Water Content Determination

In the determination of water content in food and other products containing 8% - 100% water, the latest solution for moisture analysis is manufactured by Radwag and uses microwave radiation. Absorption of the microwave radiation by polar compounds of the product (mainly water) increases the product temperature.

As a consequence of radiation absorption, molecular friction is caused by the occurrence of the reorientation of dipoles of polar compounds (Al-Harahsheh M, Al-Muhtaseb and Magee 2009).

A fast increase in temperature within the whole product volume is brought about by this. The power and frequency of the emitted microwaves, as well as the product structure and its chemical content, dictate the drying process efficiency (Soysal 2004; Kamińska and Ciesielczyk 2011).

Features of the PMV Microwave Moisture Analyzer

As a modern and productive piece of weighing equipment, PMV microwave moisture analyzer offers:

  • Short drying time (maximum of 2 – 5 minutes)
  • products, drying programs, completed drying procedures databases
  • statistical analysis for water content determination in selected product
  • Interactive menu with definable buttons, info fields, permission levels, etc.
  • Interactive proximity sensors
  • Drying process visualization displayed as a drying curve
  • Export / import of products and drying programs databases, remaining data
  • Communication via RS 232, USB, Ethernet, Wi-Fi

PMV 50 microwave moisture analyzer.

Figure 1. PMV 50 microwave moisture analyzer. Image Credit: Radwag Balances & Scales

Figure 2 presents a diagram of PMV 50 microwave moisture analyzer manufactured by Radwag Wagi Elektroniczne, Poland, showing the main subassemblies.

Diagram of PMV 50 microwave moisture analyzer.

Figure 2. Diagram of PMV 50 microwave moisture analyzer. Image Credit: Radwag Balances & Scales

Means of Operation of the Microwave Moisture Analyzer

Electromagnetic system (1), comprising carefully selected monoblock components, is used to carry out measurements of the analyzed product mass. This allows the weighing system to remain stable even when operating in unstable ambient conditions. There is a weighing pan (4) inside the drying chamber (2), which is loaded with a product (6) before being placed between two glass fiber filters (5).

Microwaves are emitted by a magnetron (3) that result from the dipole effect of water molecules in a product (6). This increases the product temperature. An infrared sensor is used to monitor the temperature (7). This is installed in the top part of the drying chamber (2).  An individual feature of each product is maximum product temperature. This is one of the drying parameters. The current product’s temperature is registered with the temperature sensor (7) and any information obtained is used by a system controlling the power of the magnetron (3). The analyzed product temperature drops (desorption of water from the product results with lower molecular friction), the emitted microwaves' power changes and its intensity matches dynamics of the process.

Up until the condition of product mass stability over time is met, the product water content is analyzed. The MA 50.X2.A moisture analyzer uses the same approach, which in this case, means complete desorption of water from the product structure.

PMV 50 moisture analyzers are used to determine water content (%M) in the analyzed products, i.e.: natural yogurt, milk, vanilla quark, creamy quark with olives, and margarine. This information is then used in the following equations:

Where:

%M – water content (relative humidity)
% D – dry mass content (absolute humidity)
m1 – wet product mass, prior analysis start
m2 – dry product mass, upon analysis completion

Bibliography

1. Adak N., N. Heybeli, C. Ertekin. 2017. ,,Infrared drying of strawberry”. Food Chemistry 219 : 109-116.

2. Al-Harahsheh M., A.H. Al-Muhtaseb, T.R.A. Magee. 2009. ,,Microwave drying kinetics of tomato pomace: Effect of osmotic dehydration”. Chemical Engineering and Processing  48 : 524–531.

3. Bradley R.L. Jr. 2010. ,,Moisture and total solids analysis”. In Food Analysis, Springer US, 85-104.

4. Ertekin C., S. Gozlekci, N. Heybeli, A. Gencer, N. Adak, B.S. Oksal. 2014. ,,Drying of Strawberries with Infrared Dryer”. Proceedings International Conference of Agricultural Engineering 1-7.

5. Isengard H.-D. 2001. ,,Water content, one of the most important properties of food”. Food Control 12(7) : 395-400.

6. Kamińska A., W. Ciesielczyk. 2011. ,,Kinetyka suszenia mikrofalowego wybranych warzyw i owoców”. Inżynieria i Aparatura Chemiczna 50 (1) : 19-20.

7. Kathiravan K., H.K. Khurana, S. Jun, J. Irudayaraj, A. Demirci. 2008. ,,Infraed Heating In Food Processing: An Overview”. Comprehensive Reviews in Food Science and Food Safety 7 : 2-13.

8. Kicińska J. 2009. „Psychologiczno-społeczne determinanty zachowań młodych nabywców na rynku dóbr konsumpcyjnych”. Journal of Agribusiness and Rural Development 4(14) : 85-94.

9. Nowak D. 2005. ,,Promieniowanie podczerwone jako źródło ciepła w procesach technologicznych. Część I”. Przemysł Spożywczy 5 : 42-43,51.

10. Pałacha Z. 2011. ,,Aktywność wody wybranych grup produktów spożywczych”. Postępy Techniki Przetwórstwa Spożywczego 2(2) : 24-29.

11. Ratti C., A.S. Mujumdar. 2006. ,,Infrared Drying” in Handbook of Industrial Drying, Fourth Edition pod redakcją A.S. Mujumdar. Taylor & Francis Group, LLC.

12. Riadh M.H., S.A.B. Ahmad, M.H. Marhaban, A. Che Soh. 2015. ,,Infrared Heating in Food Drying: An Overview”. Drying Technology 33 : 322-335.

13. Rozporządzenie Ministra Zdrowia z dnia 9 listopada 2015 r. w sprawie wymagań Dobrej Praktyki Wytwarzania, poz. 1979.

14. Sakai N., T. Hanzawa. 1994. ,,Applications and advances in far-infrared heating in Japan”. Trends in Food Science & Technology 5(11) : 357-362

15. Shrama G.P., R.C. Verma, P.B. Pathare. 2005. ,,Thin-layer infrared radiation drying of onion slices”. Journal of Food Engineering 67 : 361-366.

16. Soysal Y. 2004. ,,Microwave Drying Characteristics of Parsley”. Biosystems Engineering 89 (2) : 167-173.

17. Togrul H. 2006. ,,Suitable drying model for infrared drying of carrot”. Journal of Food Engineering 77 : 610-619.

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Last updated: Nov 29, 2019 at 9:53 AM

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