| 1. |
- Kent, M., et al.
(författare)
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Composition of foods including added water using microwave dielectric spectra
- 2001
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Ingår i: Food Control. - 0956-7135 .- 1873-7129. ; 12:7, s. 467-482
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Alklint, Charlotte, et al.
(författare)
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Effects of modified atmosphere on shelf-life of carrot juice
- 2004
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Ingår i: Food Control. - 0956-7135. ; 15:2, s. 131-137
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Tidskriftsartikel (refereegranskat)abstract
- The effects of de-aeration and modification of the headspace atmosphere on carrot juice shelf-life were investigated. The shelf-life was defined by microbial growth, determined by isothermal calorimetry and plate counts. Compared with storage under air, de-aeration of carrot juice by helium or nitrogen bubbling, followed by flush packaging had no effects on shelf-life. Similar treatment with carbon dioxide, giving a carbonated drink, prolonged the shelf-life by up to 250%. This effect could not be explained by the change in pH to 5.6, since the shelf-life was not prolonged by the addition of hydrochloric acid until pH <4.5. Both the concentrations of H+ and of dissolved CO2 were correlated to the shelf-life of fresh carrot juice; higher concentrations giving shorter shelf-lives. The concentration of dissolved CO2 was also linearly correlated to the peak thermal power. (C) 2003 Elsevier Ltd. All rights reserved.
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| 3. |
- Jerrelind, Jenny, et al.
(författare)
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Nonlinear dynamics of parts in engineering systems
- 2000
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Ingår i: Chaos, Solitons & Fractals. - : Elsevier. - 0960-0779 .- 1873-2887. ; 11:15, s. 2413-2428
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Tidskriftsartikel (refereegranskat)abstract
- By definition, chaotic vibrations arise from nonlinear deterministic physical systems or non-random differential or difference equations. In numerous engineering systems there exist nonlinearities which might affect the dynamic behaviour of the system. The objectives in this work are to summarise previous work on nonlinear dynamics of engineering parts and products and to investigate if research on how nonlinear parts can effect the total behaviour of the products have been performed. It is found that common nonlinear parts are machine elements such as gears, bearings, brakes and suspension systems. The most studied part in a product is of impact hammer type. The products are ordinary products, from searing machines, drilling machines and printers to railway vehicles. In order to be able to design reliable products the methodology should be further developed to enable use by engineers. One can conclude that the effect of nonlinear parts on the total system behaviour is still a fairly uninvestigated area.
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