Ingvald Strømmen

Modeling of Sorption Isotherms of Various Kinds of Wood at Different Temperature Conditions

Adsorption and desorption isotherms of pine, spruce, birch, and willow Salix viminalis v. Orm (2-year stem) under three temperature conditions (20, 50, 75°C) in the range of water activity 0.0–0.9 were studied. In order to describe our experimental data, five models were implemented (GAB, Peleg, Chung-Pfost, Oswin, Halsey) and compared. It was found that GAB and Peleg models provide the best fit to the experimental data. On the basis of GAB modeling, the monolayer moisture content for each kind of wood was calculated. Moreover, the hysteresis phenomenon was investigated. The influence of temperature and wood variety on sorption isotherms was also tested.

A SIMULATION MODEL FOR HEAT PUMP DRYER PLANTS FOR FRUITS AND ROOTS

ABSTRACT Dryer design requires food properties, drying rate and mass-heat transfer coefficients. These values change continuously during drying due to changes in food fractions, particularly the water fraction. The high energy demand and costs allied to inefficient devices, creates a great need for new processing equipment. Along these guide-lines, several heat pump drying research projects were established at the Norwegian University of Science and Technology. The heat pump dryer provides high quality final product as its drying conditions can be controlled. Its efficiency and non-polluting operation come from closed air-refrigerant circuits and from its ability to fully recover the latent heat of moist air as it exits the drying chamber. Most of the above features are quite the opposite of the conventional dryer characteristics. Several experiments were made on heat pump drying of fruits and roots at temperatures from -22.5 to 40°C to obtain data and correlations on thermophysical properties, specific e...

Can Drying Be an Alternative Tissue Preservation Method in Cancer Research Biobanking

The currently available methods for conservation of biobank material are mainly based on formalin fixation or the use of different freezing techniques. For molecular biological analysis, it is common to use quick freezing and low-temperature storage of the tissue materiel. This is a very energy-intensive and expensive method that requires advanced infrastructure, including monitoring and control procedures. The purpose of this work has been to study drying as an alternative process to cryogenic storage of undried biobank material, especially for use in cancer research groups. Fast freezing has been shown to be suitable to preserve the integrity of RNAs, while traditional formalin fixation preserves proteins and thus morphology in a good way. Various fresh-harvested murine tissues, such as lung, heart, skeletal muscle, liver, and kidney, were quickly frozen in liquid nitrogen and then subsequently dried at +5°C and −10°C, respectively, in a heat pump dryer. After drying, the RNA integrity was measured. The dried material was then stored for five months at +4°C and −20°C in commercial refrigerators, with subsequent measurement of RNA integrity. Dried materials were also evaluated with light microscopy and by electron microscopy with respect to tissue and cell structure. The same pattern was found for all five murine tissues. We conclude that drying at temperatures below 0°C is most careful to preserve the RNA integrity, with approximately the same RIN score of dried and non-dried samples for all five tissues. What characterized the general pattern of stored samples is that drying leads to a preservation of RNA integrity. Moreover, architecture in tissue resembled normal sections prepared from fresh tissue. In some places in the rim of the tissue sample, the lung tissue revealed alveolar-like morphology. In the electron microscope, few organelles other than the nuclei could be identified. Drying of biological material is a promising and cost-effective method for biobanks that store tissue, compared to cryogenic storage of undried material. Degradation of RNA, measured by the RIN number, is a critical factor in storing biobank tissue. In low-temperature dried material, the RIN factor is at the same level as storage of undried material at cryogenic temperatures, which is the common way of storing biobank material today. In this study, a heat pump dryer was used successfully to establish drying temperatures below and above the freezing point of the material. Further work has to be done in order to study different drying methods, drying conditions, and drying costs.

Characteristics of Bovine Spermatozoa after Immobilization by Dehydration

Extension of storage time of living animal spermatozoa is of great scientific and economical interest for the breeding industry in Norway. The extension of storage time will leave room to maneuver due to the time limit of artificial insemination of the animals. The aim of this study was to dehydrate semen in order to immobilize the spermatozoa, due to the fact that removal of water molecules leads to higher concentrations of cells and thus might contribute to the physical limitation of motility. Water was removed from diluted semen by air drying in a convection oven at approximately 33°C. The drying process was continued until there were less than 5% motile spermatozoa. The amount of total solids in the samples increased from approximately 14 to 35% during drying. After immobilization, experiments showed that with specific rehydration temperature (20°C), rehydration medium (skim milk diluents or Beltsville thawing solution), and rehydration rate, the spermatozoa recovered so that up to 70% motility was reestablished. At the female reproductive organ temperature, motile bull spermatozoa, that was dried and rehydrated, was observed for up to 50% longer periods of time compared to the reference sample. Membrane destruction caused by drying and/or rehydration of the spermatozoa was detected using plasma membrane integrity. The histograms of reference spermatozoa showed two limited populations, one living and one dead. For the dried and rehydrated samples a third population seemed to emerge. It is presumed that the cell membranes of these spermatozoa might be injured. It has been demonstrated that spermatozoa immobilized by drying and subsequent rehydration before insemination can cause fertilization and normal embryonic development in cattle.