Digitized by Kansas Correctional Industries

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Continuous thermal pasteurisation of various bulk liquid media is an important step in the food and allied industries. The design of a continuous flow pasteuriser is typically predicated on mathematical models developed from experimental data - usually batch, bench - scale, ethods. Of particular interest is the effect of combined pasteuriser temperature ( T ) and liquid pH on inactivation and survivor of contaminants. However, bench - scale thermal survivor data may not adequately mirror those in a continuous flow pasteuriser. This research presents the development and experimental validation of rigorous models for thermal pasteurisation of bacteria as affected by combined process T - pH in both batch, bench - scale capillary studies ( static ) and in a pilot continuous flow pasteuriser ( dynamic ), within a defined liquid and range of exposure time, temperature and pH ( t - T - pH ). Five integrated stages in synthesis and model analysis were undertaken using stringent criteria for goodness of fit of an adequate model established. First, four published predictive models were assessed against published static data ( n [subscript T] = 248 ) for the thermal inactivation of Escherichia coli ( ATCC 25922 ) in a Carbopol ® 941 liquid food simulant in batch capillaries over a range of t - T - pH. The models tested were the Classical Arrhenius, Davey Linear - Arrhenius ( D - LA ), Square - Root ( Belehradek ) and a third - order Polynomial model ( nOP ). Analysis showed the D - LA model best satisfied the criteria for model selection and explained 96.0 % V in the thermal inactivation rate coefficient. Second, the D - LA model was assessed against limited, published dynamic data ( n [subscript T] = 109 ) for the same E. coli strain in identical food simulant. The model explained 60 % V in the thermal inactivation rate coefficient. On average, model predictions of survivor numbers from the dynamic data were less than that predicted from the static data, i.e. for a given ( t - T - pH ) more bacterial cells were apparently inactivated in the continuous flow pasteuriser than in bench - scale, batch capillary studies. Overall, however it was not clear from extensive analyses of available data whether there is a statistically significant difference in survivor numbers of viable E. coli between batch static and continuous flow dynamic data. Third, although the D - LA model best satisfied the criteria for goodness of fit of a model, it failed to accurately predict the observed tails in the static survivor data. New models ( KDT and a modified KDT ) were synthesised to predict tails and shoulders in survivor data. The modified KDT ( MKDT ) form gave improved predictive capability over the KDT model when assessed against published static survivor data for E. coli and L. monocytogenes ( n [subscript T] = 355 ) in the Carbopol food simulant. This model, however, could not be readily integrated with equations describing the performance of a continuous flow pasteuriser. Analyses indicated that a greater density of dynamic survivor data for E. coli was needed. Fourth, a pilot continuous flow pasteuriser was constructed and used to generate a greater density of dynamic survivor data of E. coli ( ATCC 25922 ) in a Carbopol ® 941 carrier liquid for rigorous comparison with predictions from the Lin ( 1976 ) isothermal continuous laminar flow process model. Direct steam injection heating was used. Extensive dye and digital - video studies, in a section of glass holding tube confirmed the practical implementation of the assumptions of laminar flow and rapid condensation of steam. Extensive practical experiments highlighted a non - isothermal condition along the holding tube. A highly linear dependence ( R ² > 0.90 ) of exposure temperature with holding tube length, i.e. exposure time, was demonstrated. This was accounted for using mathematical approaches and quantitatively incorporated into a D - LA model for the rate coefficient in an extended Lin process model. A block experimental design of 4 T ( 54, 56, 58, 60 ° C ) x 4 pH ( 4.5, 5.5, 6.5, 7.5 ) x 3 replicates with a total of ( n [subscript T] = 834 ) exposure times ( 16 - 198 s ) was carried out in the pilot continuous flow pasteuriser. Findings highlighted that greater numbers of E. coli were thermally inactivated in the flow pasteuriser than predicted. From a practical operating view, the predictions from the extended Lin model were therefore conservative - with reduced risk to public health. Highly significant differences in the rates of heat - up of bacteria in the pilot pasteuriser ( dynamic ) ( 0.0104 s ) compared with that in the batch ( static ) capillary tubes ( 1.6 s ) and, mode of heat transfer, together with partial effects of dispersion with increasing length of pasteuriser holding tube, are postulated to be the controlling process influences for the difference between the experimental survivor data and the extended Lin model predictions. The lack of agreement between the continuous pasteuriser data and predictions from the extended Lin model indicated that this model cannot be practically applied. A direct comparison of the experimentally derived dynamic survivor data from the pilot pasteuriser ( as ln N / N [subscript 0] ) was also made with both the published static and dynamic data at a number of defined t - T - pH. This comparison revealed that overall, more E. coli were inactivated in the pilot continuous flow pasteuriser than described by published batch static capillary and dynamic data. Importantly, these comparisons showed that batch thermal survivor data for E. coli do not adequately mirror those obtained in continuous flow systems. Fifth, in a search for an improved model for the inactivation data, the newly derived MKDT model was assessed against the experimental pilot pasteuriser data. This model was rejected, however, because it could not account satisfactorily for all tails in survivor curves. A Weibull form model with two coefficients ( a scale factor ( α ) and a shape factor ( β ) ) also did not adequately predict tailing and could not be reliably extrapolated with holding time. However, a modified Weibull form, also with two model coefficients ( β [subscript 0], β [subscript 1] ), did give an improved fit to available experimental data. This research highlighted statistically significant differences between the dynamic thermal survivor data for E. coli and standard bench - scale static capillary data for a defined liquid and range of t - T - pH. It is likely that findings from this study can be generalised. However, validation should be carried out for a range of common indicator micro - organisms in a range of liquid foods. / Thesis (Ph.D.)--School of Chemical Engineering, 2006.

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Heat transfer in canned particulate system in Newtonian and non-Newtonian liquids was studied during end-over-end agitation thermal processing in a pilot scale rotary retort. Computational methods for conventional overall heat transfer coefficient (U) and fluid to particle heat transfer coefficient (hfp) were found unsuitable in high viscosity fluids. A methodology for evaluating an apparent heat transfer coefficient (hap) between retort medium and particle, and an apparent overall heat transfer coefficient Ua between retort medium and can fluid was proposed. Use of h ap and Ua concepts permitted direct predictions of particle temperature and lethality based on retort temperature. / An L-16 orthogonal experimental design of experiments was carried out to select system factors that significantly affected hap and U a values for particles in high viscosity non-Newtonian and Newtonian fluids. Experiments using central composite rotatable design and full factorial design were carried out to study the effects of selected significant factors on hap and Ua. / Using all data obtained, dimensionless correlations were developed for the prediction of hap and Ua values. The developed correlations showed a good agreement with the experimental data. More precise predictions were achieved with trained artificial neural network (ANN) models. The results of ANN models could be compiled using algebraic equations and were included so that hap and Ua values could be predicted without actually using the ANN software. A flow visualization study was conducted to better understand the heat transfer behavior in high viscosity fluids. Results showed that in particulate high viscosity fluids, the particle liquid relative movement was very weak, implying that the heat transfer between them could converge to conduction-conduction rather than convection-conduction, which results in erroneous and unusually large hfp values.

In light of its past eugenic use, and its often irreversible nature, non-therapeutic sterilization, the result of which is to deprive an individual of his/her capacity to procreate, has always enjoyed a particular status and its use and legal status engendered debate, discussion and controversy. / The purpose of this dissertation is to determine under which conditions non-therapeutic sterilization can lawfully be performed under Canadian law. / Whereas the legality of non-therapeutic sterilization when voluntarily consented to by a competent individual is today established in all Canadian provinces, it appears that Quebec is the only province to allow non-therapeutic sterilization to be performed on an individual lacking through age and/or disability the necessary capacity to consent, common law provinces denying any beneficial aspects to the procedure. The law on involuntary non-therapeutic sterilization however lacks clarity, certainty and consistency, a legislative reform is therefore advocated.

The storage life at 43°F of ground dover sole fillets (Microstomas pacificus) was determined microbiologically after treatment with ionizing radiation and antimicrobial agents. Sodium benzoate, potassium sorbate and the sodium salts of the methyl and propyl esters of parahydroxybenzoic acid (MPB and PPB) all approximately doubled the refrigerated storage life of irradiated dover sole. The dose levels employed were 0.1, 0.3, and 0.5 Mrad. The concentration of the agents used in each case was 0.1 percent. The normal spoilage of dover sole is caused predominately by the outgrowth of pseudomonads. After irradiation, however, the spoilage is due to the outgrowth of Achromobacter and certain Gram positive organisms. The spoilage pattern was not changed by the antimicrobial agents tested except at the higher dose level (0.5 Mrad), at which the spoilage was caused by yeasts. The additives had no effect on the growth rate of the microorganisms of dover sole. They merely prolonged the length of microbial dormancy that followed radiation exposure. Possible mechanisms involved in the combined effect of antimicrobial agents and irradiation are discussed. / Graduation date: 1965

Graduation date: 1962