The Rapid Determination of Fat and Moisture in Foods by Microwave Drying and NMR Analysis

Abstract

Fat and moisture analysis by microwave drying and nuclear magnetic resonance (NMR) is a direct method that yields accurate results in minutes without solvents or the frequent calibration required by indirect methods such as near infrared (NIR) or Fourier transform infrared (FTIR). In the past, NMR was unreliable for determining fat content in foods because the signal from moisture present in the sample interfered with the fat reading. There is now a peer-verified, microwave drying and NMR analysis (AOAC PVM 1:2003) for quantification of the percentage of moisture and fat in meat products. The procedure involves determining the moisture value of meat samples by microwave drying and using the dried sample to determine the fat value by NMR analysis. Five meat products were analyzed using a CEM SMART System TM (Moisture) and the SMART Trac TM System (Fat). The samples, representing a range of products that meat processors commonly analyze in daily plant operations, included the following: (i) fresh ground beef, high fat; (ii) deboned chicken with skins; (iii) fresh pork, low fat; (iv) all beef hot dogs, and (v) NIST standard reference material samples. The results were compared with moisture and fat values derived from AOAC-approved methods, 950.46 Forced Air Oven Drying and 960.39 Soxhlet Ether Extraction. The chapter also discusses the analysis of dairy samples by microwave moisture analysis and NMR fat analysis. These samples include cream, ice cream, and milk with various levels of fat. Results are compared with the Mojonnier and Gerber techniques.