No description available.

No description available.

Commercial utilization of pollinizing varieties of pears is important both for pear growers and processors in Oregon. A study was made to determine the suitability of Comice, Packam's Triumph and Anjou, the three pollinizing varieties of pears, for dehydration, as compared to the Bartlett variety which is commercially used for dehydration. These four varieties were dehydrated using conventional and dry-blanch-dry methods and were subsequently stored at 70°F. The storage period of Bartlett, Comice, Anjou, and Packam's Triumph was 275, 212, 186 and 175 days, respectively. Both fresh and dehydrated pears were analyzed for moisture, total acid, and total sugar. The over-all drying ratio and rehydration percentage of each dehydrated lot was determined. After storage, the dehydrated pears were evaluated for flavor, texture, color, over-all appearance, and over-all desirability by a panel of eight judges. The results indicated the following conclusions. (1) There was no significant difference in the over-all drying ratio of the unpeeled dried pears of all four varieties and treatments. (2) Peeled dried Packam's Triumph had the highest over-all drying ratio followed by Anjou, Comice, and Bartlett, respectively. (3) Bartlett had the highest rehydration percentage followed by Anjou, Comice, and Packam's Triumph, respectively. (4) There was no significant difference in the rehydration percentage of conventionally dried unpeeled and dry-blanch-dry unpeeled pears. But dry-blanch-dry peeled pears had a significantly higher rehydration percentage than the conventionally dried peeled pears. (5) The dehydrated Anjou pears had the lowest total sugar content of all four varieties. Packam's Triumph had a higher total sugar content than Anjou but lower than Comice and Bartlett. The total sugar content of the latter two varieties did not vary significantly. (6) The dehydrated Anjou pears had the highest total acid content of all the four varieties. Packam's Triumph had lower total acid content than Comice and Bartlett. The total acid content of the latter two varieties did not vary significantly. (7) The flavor, texture, and over-all appearance of all dehydrated lots did not vary significantly. The flavor and texture of all lots were liked by the panel, but the over-all appearance of these lots was disliked by the panel. (8) The color of peeled dried pears was rated higher than unpeeled dried pears by the panel regardless of variety and method of dehydration. The panel liked the color of dry-blanch-dry unpeeled and peeled pears more than corresponding conventionally dried unpeeled and peeled pears. The color of Comice and Anjou was rated higher than Bartlett and Packam's Triumph by the panel. The color of the latter two varieties was disliked by the panel. (9) The over-all desirability of all four varieties was rated higher than average by the panel. / Graduation date: 1965

No description available.

No description available.

M. Tech. Mechanical Engineering / Discusses the main objective of this research was to perform an experimental investigation into the heat pump drying performance of biomaterials in South African environmental and climatic conditions.Specific objectives to meet the main goal are: to design and construct a heat pump dryer (HPD) according to local conditions; to set up experimental tests and examine the effect of other vital operating conditions such as relative humidity, drying air velocity and ambient temperature; and to analyse the data in terms of the thermal performance of the heat pump and the drying performance of the dryer

The motivation of the research presented in this thesis was to investigate the potential of using a commercial 2.3 kW heat pump dehumidifier (HPD) simultaneously as a dryer for high-moisture agricultural products and for other domestic dehumidification/heating applications. A drying system incorporating the HPD was designed and constructed, along with instrumentation to gather data on the properties of process air as well as real-time weight of the material being dried. The HPD was equipped with an external water-cooled condenser that rejected excess heat out of the system. The design of the system allowed for conducting drying with recirculation of air as well as use of electrical heaters. In an open mode, the drying could be carried out simultaneously with room dehumidification and water heating in the secondary condenser. / The drying experiments were conducted with apple, tomato and agar gels. The system was found to be more effective in drying of material with higher amount of free moisture such as tomato. Comparisons were made between HPD assisted drying (partial and complete) and hot air drying (at 45°C and 65°C) in the same system using apple as the test material. Colour changes (L*a*b* values) in the samples were compared between treatments. It was observed that the degree of undesirable colour change was least in case of the HPD assisted system. The HPD dried fruit exhibited better rehydration properties than the hot air dried samples. Water activity of the HPD dried samples was noticeably lower than that of the hot air dried samples at the same water content, indicating that the residual moisture was probably held under higher tension. Histological observation indicated that there was a lesser degree of damage to the cellular structure of apple when dried with the HPD than when dried with hot air alone. / In terms of energy consumption, the process of HPD assisted drying is more expensive. Much of the energy input is rejected at the secondary condenser as excess heat. Unless this heat is recovered for another purpose, or the system is modified to reuse it for drying, the drying process must carry this loss entirely. The specific moisture extraction rate (SMER) for apple was as low as 0.1 kg per kWh with the HPD assisted system. The SMER values for drying at 45°C was 0.5 kg per kWh and was almost 0.8 kg per kWh at 65°C. / The HPD assisted drying system demonstrated the ability of heat pumps to link different energy related activities viz., drying, space dehumidification and water heating. The energy expenditure is expected to be impressive when considered for all the related applications. The concept of utilizing heat pumps on farms to link up different energy streams for better utilization of the low-grade heat sources is discussed. A possible drying efficiency assessment in the form of energy-based evaluation is proposed.

The Republic of Guinea is located on the west coast of Africa at about 11° North latitude. A large portion of Guinea's supply of protein is dried fish. The actual drying method operates under open air, the foodstuff being unprotected from unexpected rains, windborne dirt and dust, and from infestation by insects, rodents, and other animals. More, the deforestation rate is increasing year after year, depleting the source of fuel for drying. Practical ways of drying fish cheaply and sanitarily would be welcome.The present work develops a prototype solar dryer on the basis of natural convection of air. The device is comprised of a glazed flat plate collector, a furnace with translucent walls, and an air tunnel adjoining the two. Air entering the collector is heated and flows into the furnace where energy is absorbed by pieces of fish placed on horizontal racks. The air exits through an opening in the top of the device carrying moisture with it.Using the prototype solar dryer, a fish drying experiment was conducted at the Center for Energy Research, Education, and Service (CERES) at Ball State University. The primary objectives were to investigate drying rates, times, and loads expected for a dryer constructed using simple techniques and materials readily available in the Republic of Guinea. The drying experimental results are in many ways similar to those reported by previous authors.The solar dried product appears to be superior to the product of current drying methods and the foodstuff is protected from infestation or contamination during drying.Future work suggested by the project experience includes refinement of the dryer design and additional fish drying experimentation. An economic analysis would also yield information on the feasibility of widespread use of solar dryers for drying of fish in the Republic of Guinea. / Department of Physics and Astronomy

Ph. D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nutrition and Food Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 153-157. / Ph.D.