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Drying Medium (drying + medium)
Selected AbstractsApplication of the accelerated shelf life testing method (ASLT) to study the survival rates of freeze-dried Lactococcus starter culturesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2001M Achour Abstract The survival rates of two freeze-dried strains, Lactococcus lactis var diacetylactis and Lactococcus lactis var lactis, were evaluated using the Accelerated Shelf Life Testing (ASLT) method. The strains were initially isolated from a brand of a Tunisian fermented milk product. Lactococcus cell survival observed at higher temperatures was used to extrapolate to shelf life at a lower storage temperature of 4,°C. The apparent kinetics of the survival rate loss were estimated and the effect of storage temperature was quantified by determining the inactivation energies for various samples. The work has shown an overall higher survival rate of the strain Lactococcus lactis var diacetylactis. An average half-life of a strain maintained at 25,°C was equal to about 7 days as compared with about 43 days at 4,°C. The addition of lyoprotectants such glycerol, saccharose and calcium carbonate to the drying medium, improved the survival of such bacteria. © 2001 Society of Chemical Industry [source] CONCENTRATION BOUNDARY CONDITIONS IN THE THEORETICAL ANALYSIS OF CONVECTIVE DRYING PROCESSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2007AHMET KAYA ABSTRACT In the theoretical analysis of convective drying process, two boundary conditions are common for concentration: constant concentration and convection. In this study, these two boundary conditions were comparatively examined by comparing theoretical results obtained with regard to experimental ones. Pumpkin (Cucurbita pepo) was considered as the product to be dried while air was the drying medium. The drying characteristics of pumpkin were determined for various values of drying air parameters, including temperature, velocity and relative humidity. Sorption isotherms of the dried pumpkin were also determined for different temperatures and water activities. The values of the effective moisture diffusivity, Deff, and the convective mass transfer coefficient, hm, were predicted, and these values were found to agree fairly well with those available in the existing literature. PRACTICAL APPLICATIONS Convective drying as well as other drying techniques are used in order to preserve and store agricultural products for longer periods by removing some of their moisture content. Drying is a complicated process involving simultaneous heat and mass transfer under transient conditions. Understanding the heat and mass transfer in the product will help to improve drying process parameters and hence the quality. [source] Fluidized Bed Air Drying: Experimental Study and Model DevelopmentTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2003Markus Henneberg Abstract The presented study describes the processes and mechanisms of batch fluidized bed drying. The influencing factors of hot air drying are theoretically and experimentally examined, in order to present the relations between temperature and humidity profiles and all other drying parameters. A physical model is presented to facilitate the calculation of the drying processes under defined conditions. Three succeeding drying stages are therefore modeled. Mass and energy balances including all components taking part in the process are formulated. The model clarities the drying process under the assumption of pure heat transfer mechanisms. It does not contain adaptive parameters and takes into account an inactive bypass fraction of the fluidization and drying medium. The evaluation of the model was successful for two fluidized bed plants with nominal widths of 100 mm and 400 mm. The experiments showed sufficient accuracy and transferability of the model to equipment of application-oriented dimensions. On décrit dans la présente étude les procédés et mécanismes de séchage en lit fluidisé discontinu. Les facteurs importants du séchage à air chaud sont examinés de façon théorique et expérimentale dans le but d'expliquer les relations entre les profils de température et d'humidité et tous les autres paramètres de séchage. On présente un modèle physique pour faciliter le calcul des procédés de séchage dans des conditions définies. Trois étapes de séchage consécutives sont modélisées. Les bilans de matière et d'énergie faisant intervenir tous les composants qui prennent part au procédé sont formulés. Le procédé de séchage est modélisé en supposant des mécanismes de transfert de chaleur purs. Il ne comporte pas de paramètres adaptatifs et prend en compte une fraction de dérivation inactive du milieu de fluidisation et de séchage. L'évaluation du modèle s'est avérée concluante pour deux lits fluidisés de largeur nominale de 100 mm et 400 mm. Les expériences montrent une précision et une transférabilité suffisantes du modèle à des équipements de dimensions industrielles. [source] Effects of Various Sugars Added to Growth and Drying Media upon Thermotolerance and Survival throughout Storage of Freeze-Dried lactobacillus delbrueckii ssp. bulgaricusBIOTECHNOLOGY PROGRESS, Issue 1 2004Ana S. Carvalho The aim of this research effort was to investigate the role of various sugar substrates in the growth medium upon thermotolerance and upon survival during storage after freeze-drying of Lactobacillus bulgaricus. Addition of the sugars tested to the growth medium, and of these and sorbitol to the drying medium (skim milk) was investigated so as to determine whether a relationship exists between growth and drying media, in terms of protection of freeze-dried cells throughout storage. The lowest decrease in viability of L. bulgaricuscells after freeze-drying was obtained when that organism was grown in the presence of mannose. However, L. bulgaricusclearly survived better during storage when cells had been grown in the presence of fructose, lactose or mannose rather than glucose (the standard sugar in the growth medium). A similar effect could not be observed in terms of thermotolerance; in this case, the growth medium supplemented with lactose was found to yield cells bearing the highest heat resistance. Supplementation of the drying medium with glucose, fructose, lactose, mannose or sorbitol led in most cases to enhancement of protection during storage, to a degree that was growth medium-dependent. [source] | ||||||||||