Effects of Water Vapor on Oxidation of Silicon Carbide

The rate of oxidation of silicon carbide was studied at different partial pressures of water vapor. The diffusion-rate constant was found to vary with the logarithm of the partial pressure of water vapor according to the theory of thin-film oxidation as proposed by Engell and Hauffe. The products of oxidation were cristobalite and tridymite, depending on the temperature. The diffusing species appeared to be the same in the presence of partial pressures of water vapor and in the presence of partial pressures of oxygen.     

Osmotic-Convective Dehydrofreezing Process for Drying Kiwifruit

Osmotic and convective dehydrofreezing were studied to determine sugar concentration, ascorbic acid loss, and texture changes in dried and dehydrofrozen kiwifruit. Two concentrations of sucrose (60° and 72° Brix) were used as osmotic solutions after convective air drying. Time needed to reach desired moisture was reduced with combined drying compared with osmotic drying. Firmness was evaluated by the maximum force from a back extrusion test. A reduction in maximum force was observed after freezing, as compared with fresh and dried fruit. Addition of ascorbic and citric acid as antioxidants in the osmotic solution prevented browning, and significant loss of ascorbic acid during osmotic drying. Air drying at 30°C produced distinguishable color changes.     

SURFACE MORPHOLOGY OF TUMBLED CURED BEEF

Samples from bovine semimembranosus were injected to contain (1) 2.5% salt, 0.5% sodium tripolyphosphate (STPP), 156ppm sodium nitrite and 550 ppm ascorbic acid or (2) 156 ppm sodium nitrite and 550 ppm ascorbic acid. The product was then subjected to tumbling and heat processing. Treatment (1) produced a layer of coagulated protein on the surface of the meat and a layer of flattened fibers under the protein layer. Treatment (2) had a layer of protein, but exhibited less fiber flattening. Samples of treatment (1), but which were not tumbled, had neither a layer of protein nor flattened fibers. Measurement of water vapor loss from the meat surface revealed that there was no difference between tumbled and nontumbled treatments.     

ISSUES AND TECHNIQUES FOR FEDERAL GRANT-IN-AID ALLOCATIONS TO DISTRESSED CITIES*

Determining which cities are distressed and designing allocation systems for grant-in-aid programs to assist needy places are important issues in domestic policymaking. The authors present the view that techniques for measuring distress are primarily a task for analysis, while decisions on allocation issues are essentially political. The article examines grant a/location systems and makes an important distinction between the eligibility criteria for grant assistance and the formula factors used to determine how much money a community will receive. The point stressed is that, unless eligibility is based on need, the targeting effects of the formula itself may be diluted. Several approaches to establishing eligibility criteria based on need and having more targeted formulas are discussed. The authors also present several approaches to measuring community distress-socioeconomic distress, physical decay, and economic development. There is a general convergence in the findings; that is, the distressed communities tend to be the same, regardless of which standard of distress is used.     

EVALUATION OF INSTRUMENTAL METHODS FOR FIRMNESS MEASUREMENT OF FRESH AND CANNED CLINGSTONE PEACHES

The firmness of fresh and canned clingstone peaches was investigated using blade extrusion, back extrusion, and shear-compression instruments. The three techniques yielded results which correlated well among themselves and to sensory evaluation of peach firmness. Results indicate that high vacuum flame sterilization yields a canned product which is closer in firmness to fresh peaches than is the conventionally retorted product.     

Inverse Superposition for Calculating Food Product Temperatures during In-container Thermal Processing

A procedure was developed for theoretical calculation of internal product temperatures during in-container sterilization of foods. Experimental product temperatures were determined through traditional heat penetration tests (processing in a retort with come-up time of increasing temperature and holding time at constant temperature). These were used to produce, through a proposed inverse superposition solution, a “standardized,” normalized, dimensionless product temperature curve corresponding to the response of product temperature to a constant retort temperature profile. This “standardized” curve was then used, through Duhamel's superposition theorem, to calculate product temperatures for time-varying retort temperature profiles. Limitations associated with the application of Duhamel's theorem were also transferred to the proposed methodology. Theoretical, for perfect mixing, and experimental, for conduction heating, data were used in example calculations.