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Title: Rehydration of starchy foods during heat treatment
Author: Cunningham, Sharon Elizabeth
Awarding Body: Queen's University of Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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Drying is one of the main unit operations employed within the food industry as a method of preservation and extended shelf life. Rehydration is a process aimed at the restoration of the raw material properties, where the degree of rehydration may be considered as a measure of the physical degradation of the material caused by drying. A need has been recognised by the food industry for a thorough knowledge of the rehydration process in order to produce better quality products that are acceptable from a safety perspective, whilst conserving energy. The influence of processing variables on the rehydration characteristics were quantified using moisture diffusivity coefficients, evaluated by Fick's second law of diffusion. Processing parameters which improved rehydration characteristics included temperature, microwave drying, blanching and pretreatment with ionic surfactants. Microwave power and mixing had a limited effect on rehydration kinetics. Solute addition reduced the effective diffusion coefficient, with the extent of the decrease being dependent on concentration. Empirical models were utilised in order to predict the process. of water sorption as a function of temperature and time. Product quality was assessed by examining the texture degradation and volumetric changes which occurred during the rehydration process. Parameters, which influenced moisture content and morphological properties of the dried material, were recognised as key determinants that have an affect on the quality ofthe product during reconstitution. The thermal resistance of bacterial spores associated with this class of food were evaluated at various levels of moisture content. Thermal resistance decreased with increasing moisture content and, therefore, if complete rehydration is not achieved, the severity of the intended thermal process may be reduced. Supplied by The British Library - 'The world's knowledge'
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available