No description available.

The organisms in this study were chosen due to their associations with foods and their potential as food borne pathogens. Food borne diseases are an import public health problem in most countries. Bacteria of the genera Campylobacter, Salmonella and Listeria can be transported by poultry and poultry products to humans. Gastroenteritis, typhoid fever, diarrhea, dysentery may originate from the infection. This study was undertaken to determine the incidence of pathogens in a poultry processing plant using polymerase chain reaction and conventional tests and to determine the formation and survival of biofilm cells of food pathogens in trisodium phosphate.

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.

Diss. (sammanfattning) Linköping : Univ., 2003. / Härtill 4 uppsatser.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted.

There are few empirical studies of food quality within hospital food service systems. Although it is widely accepted that food quality is a multi-faceted phenomenon, much attention has been paid to single component explanations in the past. The aim of this study throughout has been two fold - to develop a model suitable for evaluating the quality of food in conventional hospital food service systems; and to evaluate food quality in selected hospitals in the Trent Regional Health Authority and West Midland Regional Health Authority using the model. A key outcome in this study has been the development of a multifaceted measurement of food quality to help catering managers deploy resources effectively, in conventional hospital food service systems. This approach was achieved using a variety of qualitative and quantitative information to score six food quality components and 15 influencing variables. Food quality was defined as a multi-dimensional measure to include measures of satisfaction of patients and catering staff, productivity, safety, and nutritional adequacy. Measures of influencing variables were chosen or adapted from those available in food service operations insofar as was possible. Where none was available, methods were developed. The variables were grouped into two major categories: human resources and system resources. A survey of 12 hospital conventional food service systems in the UK was undertaken and detailed information was collected from each, including surveys of 933 patients and 327 catering staff. Patient satisfaction with the quality of hospital food and food-related service was evaluated by patient questionnaires. It was measured by assessing 14variables. Patients seem to be generally satisfied with the food served. In the regression analysis none of the influencing variables explained the component of 'patient satisfaction' at the level of P < 0.05, suggesting that it is a different kind of component from the other 4. Importantly the component 'patient satisfaction' appears to be explained predominantly by patients' own demographic and emotional variables rather than by objective catering system factors. Age and appetite were found to significantly correlate with patient satisfaction scores. The component of food waste was found to have a high negative correlation with patients' satisfaction. It may be possible to use food waste as an index of patient satisfaction in future research. Catering staff - satisfaction was evaluated by measuring employee job attitudes towards five aspects of their job using the Job Description Index (JDI). The JDI is directed toward specific areas of satisfaction rather than global or general satisfaction and was easily administered. The food service workers surveyed in this research were less satisfied with their jobs than are other types of workers in other industries. In the regression analysis total number of patients explains around 36% of the variation in staff satisfaction. The productivity level was based upon the total meal equivalents divided by the total labour hours required to produce and serve them. The regression analysis suggests that around 77% of the variance in productivity is explained by labour cost. The safety component was based upon two elements which were microbiological control and temperature control. The results of regression analysis suggest that the number of menu items and the subsidizing meal ratio explain around 74% of the variation in the safety component. Nutritional adequacy was evaluated indirectly by measurement of food waste. In the regression analysis more than 68% of food waste component can be explained by the variable occupancy rate. Correlations between the food quality components show that a non-significant relationship existed between all but one of the components of food quality studied. A significant negative correlation existed between the patients'satisfaction with the hospital meal and service and the food waste; this was expected. The non-significant correlations between the components of food quality showed the independence of components, confirming the need for a multi-dimensional model of food quality. The findings of this research support the notion that food quality is a multi-faceted phenomenon and have led to the development of a practical way of measuring it.

Procedures associated with Quantitative Descriptive Analysis were used to identify and subsequently train a panel to quantify the perceived textural attributes of Cheddar cheese. Seventeen types of Cheddar were assessed by the panel for creaminess, crumbliness (fingers), crumbliness (chewing), firmness, graininess, hardness (first bite), hardness (cutting), and springiness. Cluster and Principal Component analyses of the sensory data revealed that the cheese samples could be subdivided into young, mature and extra mature Cheddars in terms of the textural attributes measured. The panel was also able to distinguish between the low fat and genuine Cheddars. The percentage fat, moisture and salt contents and the pH level of the seventeen Cheddar samples were established. An inverse correlation between fat and moisture content and a positive correlation between pH level and salt content were observed. The rheological properties were measured using three tests performed on an Instron Universal Testing Machine - a compression test, a cutting test and a stress relaxation test - and, where appropriate, were reported in terms of true stress and true (Hencky) strain curves. The viscoelastic properties of Cheddar observed during stress relaxation tests were modeled using a Generalised Maxwellian model consisting of two exponential elements and a residual term. Considerable variation in all the rheological properties was observed amongst the Cheddar samples. The rheological parameters did not distinguish between the samples to the same extent as the sensory assessment. However, Cluster Analysis of the rheological data did differentiate between the rheological profiles of the young (mild & medium) and the remaining mature/extra mature samples. The relationships between the textural attributes and the chemical and rheological parameters were investigated. No relationship between chemical composition and texture was identified, but correlations between the rheological parameters and the textural attributes were not uncommon. Multiple regression techniques were employed to construct mathematical models to predict the textural attributes from the rheological data. Successful models were constructed utilising parameters from the compression and cutting tests for all the attributes apart from creaminess. More precise models were constructed for firmness, springiness and crumbliness (fingers) where the action of the instrumental test from which the rheological parameters were obtained resembled the test method used by the panel. The chemical, textural and rheological properties of an English Cheddar were determined at various stages during its ripening period to investigate any changes that occurred. A slight increase in pH was the only chemical change recorded. Progressive changes in the majority of the textural attributes were observed. The most dramatic changes included a decrease in springiness and an increase in creaminess. A changing rheological profile was also observed during maturation, a decreasing strain at fracture being the most notable development. The sequence of changes in both the textural and rheological properties was divided into three fairly distinct phases, the initial stage reflecting the developments necessary before the cheese would be suitable for retail sale and the final stage including the development of the necessary textural attributes characteristic of a Mature English Cheddar. It was evident that the timing of the maturation period was pertinent to the development of textural attributes characteristic of particular maturities of Cheddar cheese. The textural attributes of the maturing Cheddar were also predicted at each stage of maturation using the mathematical models constructed in the initial study. Accurate predictions were made for all the attributes except crumbliness (chewing) and graininess.

A gas chromatographic method for the routine analysis of volatile and semi-volatile sulphur compounds in beer was developed. Various selective and specific detectors, capillary columns and methods of sample preparation were compared. The combination offering the best sensitivity and stability consisted of solid phase microextraction (SPME) as the sample preparation step; a combined polar/non-polar chromatographic column; and a pulsed flame photometric detector (PFPD). All parameters were optimised to achieve maximum sensitivity. The system was linear for the range of sulphur compound concentrations found in beer, and displayed good reproducibility. The calibrated SPME-GC-PFPD system was used to analyse several different varieties of beer from a range of breweries, and to investigate the change in the concentrations of sulphur compounds when beer is subjected to illumination.

In this work laboratory-scale experiments were carried out to determine and quantify the mechanisms by which water, sugar and other solutes are transferred from vegetable tissue to blanch water. Samples of commercial potato and carrot varieties were studied and Fick's law of diffusion was applied to describe the mass transfer of solutes during blanching of cylinders and cubes of the vegetable tissues.