Anne Karin Hemmingsen

Relationship of Product Structure, Sorption Characteristics, and Freezing Point of Atmospheric Freeze-Dried Foods

Drying is an important unit operation in processing of foods with a long shelf life. The drying process influences product properties and quality; the products may shrink, break, or undergo rheological, physical, and biochemical changes. Important parameters responsible for product quality changes during drying are temperature, relative humidity, and residence time. Studies of thermal and mass transfer properties during drying are essential for understanding the changes in product quality and for designing and dimensionalizing the drying process. Drying kinetics, sorption properties, shrinkage, and freezing point depression were determined during atmospheric freeze drying (AFD) of pieces of apple, turnip cabbage, and cod. Adsorption rate and sorption isotherms were determined in the end product. The drying temperature affected the physical properties. Drying at −5°C resulted in a larger shrinkage than drying at −11°C. GAB modeling was used to characterize the sorption properties of the products. No typical sigmoidal shape was found of the moisture sorption isotherms of the products, which is in accordance with the Guggenheim constant found from the same results. Experimental data on freezing point depression were used to find product constants E and b in the Schwartzberg equation for the freezing point depression. Freezing point depression, as a function of the dry matter content, was determined using Schwartzbergs equation and a component composition model (CCM). The result indicates an influence of structural effects on freezing point depression.

Water Adsorption in Feed Ingredients for Animal Pellets at Different Temperatures, Particle Size, and Ingredient Combinations

Production of animal feed pellets with uniform, predictable, and good technical pellet quality is challenging. The objective of this work was to investigate water adsorption in dry ingredients and in mixture of dry ingredients commonly used in animal feed. Rehydration at 20 and 80°C and water adsorption in moist air at 80°C were studied. Ingredients studied were soybean meal, wheat, barley, dehulled oats, rapeseed cake, sugar beet pulp, maize, and wheat bran. The ingredients were milled fine (< 0.5 mm) or coarse (> 0.5 mm). Results show that the chemical composition of ingredients and the physical state of water affect water adsorption. A combination of steam and water should be used to optimize production of pelletized feed. The combination of a fine degree of milling, high temperature, and a long residence time favor the water adsorption process for most of the dry ingredients. For mixtures of dry ingredients, the individual chemical composition of each ingredient could be as important as physical factors such as particle size, temperature, and residence time in water.

Energy-Efficiency Technologies for Reduction of Offshore CO2 Emissions

Summary This paper will discuss novel technologies for increasing the energy efficiency of offshore oil and gas platforms. Three case studies are in progress that are based on actual oil-producing platforms—two on the Norwegian Continental Shelf (NCS) and one in the Brazilian basin. The current focus is on developing compact, novel bottoming cycles for recovery of waste heat from the gas turbine and heat recovery from the compressor train for gas export. The technologies under investigation use steam and alternative working fluids, such as carbon dioxide (CO2) and hydrocarbons. All the fluids investigated in this project are natural working fluids; hence, they will not cause any unexpected environmental issues in the future. A case study was performed that considered an 18-year period of operation on an actual platform and a scenario in which one gas turbine was removed and replaced with a CO2 bottoming cycle by use of the exhaust heat from a different gas turbine. The beauty of this scenario is that it would not increase the weight on the platform because the crate containing the gas turbine to be removed was of a weight similar to that of the crate containing the CO2 bottoming cycle. The substitution would not affect the ability to cover the heat demand on the platform because a waste-heat-recovery unit (WHRU) could be installed on the platform’s other gas turbine. The case study indicates a significant reduction in CO2 emissions of 22% (63 000 t/a), and does not involve adding additional weight or volume to the platform. If operating on the NCS, the annual savings in reduced fuel costs and CO2 tax from implementing this scenario would be USD 17 million, although much lower in other territories.

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.