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- Kent, M., et al.
(author)
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Composition of foods including added water using microwave dielectric spectra
- 2001
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In: Food Control. - 0956-7135 .- 1873-7129. ; 12:7, s. 467-482
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Journal article (peer-reviewed)abstract
- The added water content of fresh and untreated pork, poultry, fish and prawns was adjusted either by dipping in polyphosphate and salt solutions of known concentrations for controlled periods, or by injection (pork) with polyphosphate and salt solutions. Mixtures were prepared from treated and untreated fish and other foods (milk and flour). Liquid uptake was determined by the weight gain of samples. The proximate composition of the samples was determined: water, fat, protein, NaCl and phosphorus (for polyphosphate content). Complex dielectric spectra of each product were measured at known temperatures and at 31 frequencies in the range 0.2-12 GHz using an automatic network analyser (ANA) and a 3.0 mm open-ended coaxial sensor. The spectra were subjected to various procedures. Principal component analysis (PCA) using the individual complex components. Regression of the composition data against the principal components to obtain prediction formulae for composition including liquid uptake (internal cross-validation). Regression of the composition data against raw spectral data and against other composition variables to obtain similar formulae. In order to design a simpler instrument, the effect on accuracy was studied of reducing the number of frequencies in the spectrum and its range. The slight loss of accuracy engendered by using only five or six frequencies was acceptable. The accuracy of the method in predicting liquid uptake and composition was good. Using one of the compositional variables in the calibration made it equivalent to accuracy obtained by proximate analysis, which was the limiting factor. Measurements on solutions of glycerol, NaCl and water with precisely known composition demonstrated that the intrinsic accuracy of the instrument was far better. A prototype instrument was built and validated using samples of prawns and herring. © 2001 Elsevier Science Ltd.
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- Kent, M., et al.
(author)
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Composition of foods using microwave dielectric spectra
- 2000
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In: European Food Research and Technology. - 1438-2377 .- 1438-2385. ; 210:5, s. 359-366
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Journal article (peer-reviewed)abstract
- As part of a European Union project (FAIR CT97 3020) microwave dielectric spectra of processed prawns (Pandalus borealis), cod (Gadus morhua), pork and chicken were measured and the data transformed using the statistical method of principal component analysis. The principal components were regressed (principal component regression) against various compositional variables, notably added water, protein, water, total phosphorus and NaCl and the calibration was validated using the method of internal cross-validation. © Springer-Verlag 2000.
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- Kent, M., et al.
(author)
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Determination of prior treatment of fish and fish products using microwave dielectric spectra
- 2000
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In: European Food Research and Technology. - 1438-2377 .- 1438-2385. ; 210:6, s. 427-433
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Journal article (peer-reviewed)abstract
- Microwave dielectric spectra of fish products [processed prawns (Pandalus borealis), cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and saithe (Pollachus virens)] were transformed using the statistical method of principal component analysis. The principal components obtained were used as descriptors to construct discriminant functions for the separation of the samples into groups, e.g. added water or no added water, polyphosphate or no polyphosphate. The method was validated using internal cross-validation. © Springer-Verlag 2000.
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- Kent, M., et al.
(author)
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Intangible but not intractable : The prediction of fish 'quality' variables using dielectric spectroscopy
- 2007
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In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 18:4, s. 1029-1037
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Journal article (peer-reviewed)abstract
- In many fields the concept and measurement of quality is of prime importance. The fish industry is no exception to this and many sensory approaches have been devised to quantify this rather intangible property. The EU 5th framework project 'SEQUID' has concentrated on the measurement of the dielectric properties of fish tissue as a function of time both in frozen and chilled storage. The many deteriorative biochemical and microbiological processes that take place during the gradual spoilage of such materials have a subtle influence on the dielectric properties across the spectrum but notably in the microwave frequency region. In this region the complex interactions of water, solutes and structure-forming proteins are systematically changed by death and decay. Chilling or freezing may slow these processes but such preservation techniques do not halt them entirely. The SEQUID project has shown that it is possible, using a combination of time domain reflectometry and multivariate analysis, to predict certain quality-related variables, both sensory and biochemical, with comparable accuracy to existing methods. These results are presented in this paper. © 2007 IOP Publishing Ltd.
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