| 1. |
- Piyasena, P, et al.
(author)
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Characterization of Apples and Apple Cider Producedby a Guelph Area Orchard
- 2002
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In: Lebensmittel-Wissenschaft und-Technologie. - : Elsevier BV. ; 35:4, s. 367-372
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Journal article (peer-reviewed)abstract
- Thermal stability of food-borne pathogens in apple cider is influenced by the composition of the product. As a preliminary step to determine the effect of pasteurization of apple cider on the survival of Escherichia coli O157:H7, a study was carried out to characterize apples and unpasteurized apple cider produced by a Guelph area orchard. Samples of commercial unpasteurized cider and the constituent apples were collected over 13 wk from August to November 1998, and unpasteurized laboratory cider was made from the individual apple varieties. pH, titratable acidity, turbidity, total microbial counts, total solids and 1Brix for filtered and unfiltered samples were measured. The maximum, minimum, and average values for all unpasteurized commercial cider samples were found as follows: pH, 3.71, 3.17, and 3.43; titratable acidity, 93.47, 49.46, and 69.95mL of 0.1N NaOH/100 mL; total solids, 13.21, 10.93, and 11.90%; 1Brix, 13.01, 11.17, and 12.02; turbidity, 238.1, 145.1, and 204.9 nephelometric turbidity units; and total plate count, 4.91, 2.61, 3.75 log cfu/mL. There were no significant differences (P40.05) between filtered and unfiltered samples. In addition, in commercial unpasteurized cider, there were no significant differences (P40.05) with respect to any of the factors with the time of processing. The composition of the unpasteurized laboratory cider made from individual apple varieties was dependent on the variety, but was generally within the ranges from the published literature values. McIntosh apples showed a significant (P>0.05) decrease in titratable acidity with time of harvest. The results suggest that it is necessary to take the composition of commercial apple cider into account when developing thermal inactivation models for food-borne pathogens.
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| 2. |
- Rayner, Marilyn, et al.
(author)
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Membrane emulsification modelling: how can we get from characterisation to design?
- 2002
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In: Desalination. - 1873-4464. ; 145, s. 165-172
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Journal article (peer-reviewed)abstract
- There has been an increasing interest in a new technique for making emulsions known as membrane emulsification, which uses a microporous membrane operated in cross-flow. The continuous phase is pumped along the membrane and sweeps away dispersed phase droplets forming from pore openings as shown in Fig. 1. The effects ofprocess parameters in membrane emulsification have been studied, especially on a quantitative level. However, the physical mechanisms of droplet formation are still under investigation to better elucidate the roles of operating parameters, and finally model the process. This work reviews current developments and deficiencies in the modelling membrane emulsification processes.
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| 3. |
- Rayner, Marilyn, et al.
(author)
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Transfer and adsorption of surfactants to an expanding oil water interface during membrane emulsification
- 2003
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In: SIK Proceedings. ; 162, s. 68-71
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Conference paper (peer-reviewed)abstract
- uses a microporous membrane operated in cross-flow. The continuous phase is pumped along the membrane and sweeps away dispersed phase droplets forming from pore openings as shown in Figure 1. The key feature of the membrane emulsification process, which sets it apart from conventional emulsification technologies, is that the size distribution of the resulting droplets is primarily governed by the choice of membrane and not by the development of turbulent drop break up [1]. The main advantages of membrane emulsification are the possibility to produce droplets of a defined size with a narrow size distribution, low shear stress, the potential for lower energy consumption, and simplicity of design [2]. The interfacial tension and applied dispersed phase pressure determine the flow rate through the microporous membrane. As a droplet is pressed into the continuous phase, a new interface is created and surfactant molecules act at this surface to reduce the tension over time. Membrane emulsification differs from conventional emulsification processes in that the droplet formation time is of the same order of magnitude as the dynamic interfacial tension of common food emulsifiers [3]. The effect of emulsifiers is further complicated by the fact that droplet deformation and adsorption at the interface are coupled, thus both the rate at which deformation and detachment forces act, as well as how fast surfactants adsorb to the growing interfacial area become relevant over the time scales involved. The objectives of this work were to describe the diffusion controlled adsorption of surfactants at the oil water interface, and secondly to model the flow of the dispersed phase through a pore and subsequent surface expansion rate as the drop grows into the continuous phase.
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| 4. |
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| 5. |
- Rayner, Marilyn, et al.
(author)
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Using the Surface Evolver to model droplet formation processes in membrane emulsification
- 2004
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 279:1, s. 175-185
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Journal article (peer-reviewed)abstract
- A model was developed to describe the droplet formation mechanism in membrane emulsification from the point of view of Gibbs free energy with the help of the Surface Evolver, which is an interactive finite element program for the study of interfaces shaped by Surface tension. A program to test the model was written and run which allows the user to track the droplet shape as it grows, to identify the point of instability due to free energy, and thus predict droplet size. The inputs of the program are pore geometry, oil-aqueous phase interfacial tension, and contact angle. The model reasonably predicted droplet sizes for oblong-shaped pores under quiescent conditions where the force balance approach is not applicable. The model was validated against experimental conditions from the literature where the average error of the predictions compared to the mean droplet sizes was 8%. (C) 2004 Elsevier Inc. All rights reserved.
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