EXTENDED VALIDATION OF A SIMPLIFIED EXTRACTION AND GRAVIMETRIC DETERMINATION OF TOTAL FAT TO SELECTED FOODS

A simplified method for chloroform/methanol extraction and gravimetric determination of total fat previously published for diet composites was tested on additional foods, including milk, cheese, fried snack foods, nuts/seeds, salad dressings, baked goods, meat, fish/shellfish and fruits/vegetables. Homogenized food composites and certified reference materials (CRMs) were analyzed using the existing method involving, briefly, orbital shaking of a subsample with chloroform/methanol/buffer in specific proportions, then recovery of total lipid in the chloroform extract. For meat, fish, shrimp, cheese and fried plantains, total fat recovery was low and/or variability was high with the unmodified assay versus results from other standard total fat methods (e.g., ether extraction, acid hydrolysis) or to CRM assigned values. Reducing the sample size or adding a homogenization step during extraction resulted in relative standard deviations of < 3% for all matrices and also values consistent with those generated by other standard total fat methods and within assigned ranges for total fat in most CRMs.

PRACTICAL APPLICATIONS

The method allows for routine batch analysis of multiple samples of a range of food types with minimized hands-on time, using commonly available laboratory equipment. The resulting total lipid extract can be subdivided for analysis of various specific lipid analytes as well as for gravimetric measurement of total fat.     

A COMPARISON OF PROTEIN ASSAYS FOR THE DETERMINATION OF THE PROTEIN CONCENTRATION OF BEER

Seven protein assays have been compared for determination of the protein content of beer. Dialysis and ultrafiltration have been used to investigate possible interference and the protein content of the samples has been simultaneously monitored by sodium dodecyl sulphate-polyacrylamide gel electro-phoresis. The Fisons NA2000 Nitrogen/Protein Analyzer gave identical results to the standard Kjeldahl method but both measure nitrogen-containing compounds rather than protein. Colorimetric methods based upon the biuret reaction (including the Lowry and bicinchoninic acid protein assays) are particularly prone to interference from reducing substances and gave protein concentration values dependent upon the sample volume. The protein dye-binding assays (Coomassie Brilliant Blue and pyrogallol red-molybdate methods) were optimal for beer protein analysis displaying minimal inter ference and giving reproducible protein concentration values consistent with the protein content of the beers as indicated by electrophoresis.     

SUBJECTIVE CONSTRUCTIONS OF NEIGHBORHOOD BOUNDARIES: LESSONS FROM A QUALITATIVE STUDY OF FOUR NEIGHBORHOODS

ABSTRACT: This article explores the boundaries of neighborhoods as subjectively constructed by 37 adolescents and 33 parents across four census‐defined block groups in a Western city. We examine the degree of consensus among participants on the spatial boundaries of their neighborhoods, the stability of participants' subjectively constructed neighborhood definitions, and the overlap between subjectively constructed definitions and census block group and tract definitions. Through an analysis of qualitative interviews, we isolate four factors that appear to influence how participants define their neighborhood boundaries: physical and institutional characteristics of the neighborhood, its class, race, and ethnic composition, perceived criminal threats from within and outside the neighborhood, and symbolic neighborhood identities. These factors can operate to facilitate or compromise consensus and stability about neighborhood boundaries and identity. The study findings are exploratory but suggest several avenues for further investigation into how parents and adolescents construct neighborhood boundaries and the possible influences that subjective neighborhood definitions have on families.     

Taking Stock: An Analysis of the Publishing Record as Represented by the Journal of Engineering Education

The Journal of Engineering Education emerged in the engineering education community in 1993 as a continuation of the American Society of Engineering Education's journal, Engineering Education. The Journal of Engineering Education was to play a role in the broadening of engineering education culture by helping to bring the scholarship of engineering education to the same level of respect and recognition in the faculty reward system as traditional scholarship in engineering sciences. In doing so, the journal hoped to keep pace with and encourage the significant changes in engineering education needed to prepare for the challenges of 21st century practice. This paper discusses the engineering education environment as reflected in six years of papers published in the Journal of Engineering Education from 1996 to 2001. Topics of papers are identified, along with changes and trends in these topics during the six‐year period. In addition, characteristics of particularly convincing papers are enumerated and discussed. This paper is offered as a summary and review of this six‐year body of work on engineering education and should aid the engineering education community in reflecting on the success of the Journal in promoting and encouraging the scholarship of teaching.     

Phytic Acid as a Food Antioxidant

Phytic acid has been shown previously to form an iron chelate that inhibits iron-catalyzed hydroxyl radical formation and lipid peroxidation. To further characterize its antioxidant properties in model food systems, we investigated the effects of phytic acid on ascorbic acid degradation in aqueous solution and on stability of oil-in-water emulsions. In both systems 1 mM phytic acid provided significant protection against oxidative damage and increased emulsion shelf-life fourfold. To test antioxidant efficacy of phytic acid in a whole food system, its effect on development of warmed-over flavor was determined. Phytic acid substantially inhibited oxygen uptake, malondialdehyde formation and warmed-over flavor development in refrigerated chicken.     

ANALYSIS OF SIMULTANEOUS RADIATIVE AND CONDUCTIVE HEAT TRANSFER IN FLUIDIZED BEDS

In the bubbling regime of operation for fluidized beds, the major mechanism for heat transfer is transient conduction to periodic packets of densely packed particles at the heat transfer surface. The well known Mickley and Fairbanks model, with various subsequently proposed modifications, adequately describes this transient conduction mechanism. However, no adequate theory exists for heat transfer in high-temperature fluidized beds where radiative contribution becomes significant.

Analysis of the radiative contribution is complicated by the nonlinear interaction of radiation with conduction/convection. This paper describes a differential formulation of the combined radiative/ conductive heat transfer process. The discrete flux method used by Churchill et al. for radiative transport in heterogeneous media is applied here to the problem of transient heat transfer to packets in fluidized beds. Packets are modeled as radiatively participating media with absorption, scattering, and emission of radiation. Simultaneous solution of the governing differential equations for temperature and forward and backward radiation fluxes permits calculation of instantaneous heat flux at the heat-transfer surface. Radiative transfer during bubble contact is added as a time-weighted contribution.

Using experimental data on radiative cross sections (from packed media experiments) and experimental data on packet residence times (from fluidized bed experiments), the combined conductive/radiative heat transfer to packets was obtained for examples of fluidized beds at different fluidizing velocities and wall temperatures. The analytical results indicate that the relative importance of radiation is affected by particle size, average packet residence time, and the radiative attenuation cross sections. For operating conditions representative of fluidized bed combustion, the model estimates a 10 to 20 percent contribution by radiation to the total heat transfer. Comparison to limited experimental data from the literature shows reasonable agreement.     

The aerobic microflora of the Scotch haggis

The aerobic microflora of freshly purchased Scotch haggis was dominated by organisms identified with Bacillus. Lactobacillus, Staphylococcus , yeasts and moulds were also detected in significant numbers. On storage at 5,30 or 37°C for 3 weeks, spoilage of the haggis was accompanied by a drop in pH and a tenfold increase in numbers of general contaminants and lactic acid bacteria.