Rapid measurement of moisture content of cheese analogs and process cheese products using low-field proton magnetic resonance
Abstract
The dairy industry would benefit from rapid and non-destructive determination of moisture content of cheese products. The two components primarily responsible for the low-field magnetic resonance (MR) spin-spin relaxation (T2) signal of cheese products are fat and restricted water in a protein matrix. If the moisture component of the signal can be distinguished from the fat component, it should be possible to measure moisture using an MR sensor. Therefore, a key aspect of the development of MR moisture measurement method is examining the T2 decay behavior of cheese products. Carr-Purcell-Meiboom-Gill (CPMG) tests were conducted on samples of vegetable oil, milkfat, cheese analogs, and process cheese products. The resulting T2 decay curves were analyzed using multi-term exponential and stretched exponential models. Multi-term exponential models containing one or more exponential terms are commonly used to analyze T2 curves. The stretched models are appropriate when there is a distribution of relaxation times. The results of the analyses of the relaxation decay curves using these models were compared on the basis of their standard errors of fit and their sensitivity to changes in moisture content. The number of unknown parameters in the three-term exponential and two-term stretched exponential models was reduced by assuming that the relaxation time of the fat component was the same as the relaxation time of pure fat. At least one parameter of each model was linearly correlated with moisture content of cheese analog and process cheese samples. For cheese analogs, the three-term exponential model and two-term stretched exponential model gave the lowest standard errors of fit and the highest coefficients of correlation. The two-term stretched exponential model proved to be sufficiently versatile to give good moisture content predictions for a data set consisting of four brands of process cheese products having distinctly different compositions.
Degree
Ph.D.
Advisors
Stroshine, Purdue University.
Subject Area
Agricultural engineering|Food science
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