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Analysis of the inactivation kinetics of freeze-dried á-amylase from bacillus a...
Saraiva, J.; Oliveira, J. C.; Hendrickx, M.; Oliveira, F. A. R.; Tobback, P.The thermal inactivation kinetics of freeze-dried á-amylase in a solid matrix was studied at water contents ranging from 1.5 to 23.9 g water per 100 g dry solid. These conditions were obtained by equilibration in dry environments, with water activities ranging between 0.11 and 0.88. Isothermal inactivation experiments in the range 135 to 150 °C were performed. Results were analysed with both the Bigelow and Arr...
Inactivation of alpha-amylase from Bacillus amyloliquefaciens at low moisture c...
Saraiva, J.; De Cordt, S.; Hendrickx, M.; Oliveira, J.; Tobback, P.The thermal inactivation characteristics of dehydrated a-amylase in solid state at various moisture contents was studied at temperatures between 135 and 150°C. The inactivation kinetics show a first order decay. The enzyme was found to be more thermostable than in aqueous solution. The z-value dependency with moisture content has shown some fluctuactions, having an absolut minimum of 19°C at 23.9% moisture.
Changing the thermostability of Bacillus licheniformis a-amylase
De Cordt, S.; Saraiva, J.; Hendrickx, M.; Maesmans, G.; Tobback, P.We applied "solvent engineering" (i.e. variation of environmental conditions) to and/or irnrnobilized Baci//us licheniforrnis a-amylase covalently onto porous glass beads. In this way, important alterations in its thermostability characteristics (kinactrE Ainactw) ere achieved.
Generalized (semi)-empirical formulae for optimal sterilization temperatures of...
Hendrickx, M.; Silva, C.; Oliveira, F.; Tobback, P.A computer program was developed to model heat sterilization of one-dimensional conduction-heated foods with negligible surface resistance to heat transfer. The optimal sterilization temperature, defined as the processing temperature that results in a food product with minimum surface cook-value after achieving the desired degree of sterility, was calculated as a function of food properties (thermal diffusivity...
The influence of water activity on thermal stability of horseradish peroxidase
Hendrickx, M.; Saraiva, J.; Lyssens, J.; Oliveira, J.; Tobback, P.The thermal stability of horseradish peroxidase in the solid state was studied as a function of water activity, from 0.11 to 0.88. At all activities the enzyme was found to be much more stable in the solid state than in solution. Inactivation temperatures were in the range of 140–160°C. Inactivation curves show a biphasic behaviour which can be described by a model assuming two fractions (heat labile and heat s...
Critical evaluation of commonly used objective functions to optimize overall qu...
Silva, C.; Hendrickx, M.; Oliveira, F.; Tobback, P.Two objective functions—volume average retention and volume average cook-value—commonly used to optimize the overall quality and nutrient retention of heat-preserved foods, were studied and optimal processing conditions based on the two approaches were compared. Case studies from the literature were run and tested for the two objective functions. The influence of the decimal reduction time (at the reference tem...
Optimal sterilization temperatures for conduction heating foods considering fin...
Silva, C.; Hendrickx, M.; Oliveira, F.; Tobback, P.Optimal sterilization temperatures are defined as the processing temperatures which result in a minimum surface cook-value after achieving the desired degree of sterility. They were calculated as a function of product heating rate, surface heat transfer coefficient, initial food temperature, heating medium come-up-time, z-value for the quality factor and target Fo-value. Different one-dimensional heat transfer ...
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