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- Aronsson, Kristina, et al.
(author)
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Growth of pulsed electric field exposed Escherichia coli in relation to inactivation and environmental factors
- 2004
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In: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 93:1, s. 1-10
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Journal article (peer-reviewed)abstract
- Pulsed electric fields (PEF) have been proven to inactivate microorganisms during nonthermal conditions and have the potential to replace thermal processing as a method for food preservation. However, there is a need to understand the recovery and growth of survivors and potentially injured microorganisms following PEF processing. The purpose of this investigation was to study the growth of Escherichia coli at 10°C following exposure to electrical field strengths (15, 22.5 and 30 kV/cm) in relation to inactivation and the amount of potentially sublethally injured cells. One medium was used as both a treatment medium and an incubation medium, to study the influence of environmental factors on the inactivation and the growth of the surviving population. The pH (5.0, 6.0 and 7.0) and water activity (1.00, 0.985 and 0.97) of the medium was varied by adding HCl and glycerol, respectively. Growth was followed continuously by measuring the optical density. The time-to-detection (td) and the maximum specific growth rate (?max) were calculated from these data. Results showed that the PEF process did not cause any obvious sublethal injury to the E. coli cells. The number of survivors was a consequence of the combination of electrical field strength and environmental factors, with pH being the most prominent. Interestingly, the ?max of subsequent growth was influenced by the applied electrical field strength during the process, with an increased ?max at more intense electrical field strengths. In addition, the ?max was also influenced by the pH and water activity. The td, which could theoretically be considered as an increase in shelf life, was found to depend on a complex correlation between electrical field strength, pH and water activity. That could be explained by the fact that the td is a combination of the number of survivors, the recovery of sublethal injured cells and the growth rate of the survivors. © 2003 Published by Elsevier B.V.
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| 2. |
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| 3. |
- Hansson, A., et al.
(author)
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Multivariate analysis of the influence of pectin, white syrup, and citric acid on aroma concentration in the headspace above pectin gels
- 2002
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In: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 50:13, s. 3803-3809
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Journal article (peer-reviewed)abstract
- Pectin gels consist of polysaccharide networks surrounded by water. The gel networks can prevent release of aroma molecules from the gel to the gas phase above. In this study static headspace measurements were performed to correlate aroma concentration in the gas phase above pectin gels to different amounts of the gel ingredients. As a consequence, aroma concentration in the headspace in relation to gel texture, as characterized by rheology measurements, was also studied. Aroma concentration in the headspace above strong gels was low, due to entrapment of aroma molecules within the gel structure. Viscous solutions generally gave a high aroma concentration in the headspace, but owing to a complex matrix, this was lowered when large amounts of the gel ingredients were added. However, a high correlation between interaction terms and square terms of design variables and rheology parameters with aroma compounds indicated nonlinear and complex relationships.
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| 4. |
- Lundin, Leif, et al.
(author)
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NIR spectra in relation to viscoelastic properties of mixtures of Na-?-Carrageenan, locust bean gum and casein
- 1998
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In: Food Hydrocolloids. - 0268-005X .- 1873-7137. ; 12:2, s. 189-193
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Journal article (peer-reviewed)abstract
- Near-infrared spectral data were correlated with the viscoelastic property storage modulus, G?, for mixtures of five biopolymers using multivariate analysis. Gels containing Na-?-carrageenan (0.5-1.0%) mixed with locust bean gums with two different mannose to galactose ratios, ?-casein and/or ?-casein (0-0.5%, polymer concentration) in 0.25 M NaCl were studied. Forty-two experiments based on a multivariate, central composite circumscribed design (CCC) were performed. Partial least square (PLS) regression was used to find a model relation between NIR transmittance spectra, recorded at 15°C in the wavelength interval 400-2500 nm, and the G? for the biopolymer gels at 15°C. Depending on sample composition, the G? varies between 0 and 3500Pa. Cross-validation using a designed data set led to a model based on 11 principal components with a correlation coefficient of 0.85 and a root mean square error of prediction of 540 Pa. © 1998 Published by Elsevier Science Ltd. All rights reserved.
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