Biomedical subjects

G R Ziegler

Publications and source records attributed to G R Ziegler.

5 recordsLinked to original sources

PubMed2005

Quantitative density profiling with pure phase encoding and a dedicated 1D gradient.

A new centric scan imaging methodology for density profiling of materials with short transverse relaxation times is presented. This method is shown to be more robust than our previously reported centric scan pure phase encode methodologies. The method is particularly well suited to density imaging of low gyro-magnetic ratio non-proton nuclei through the use of a novel dedicated one-dimensional magnetic field gradient coil. The design and construction of this multi-layer, water cooled, gradient coil is presented. Although of large diameter (7.62 cm) to maximize sample cross section, the gradient coil has an efficiency of several times that offered by conventional designs (6 mT/m/A). The application of these ideas is illustrated with high resolution density-weighted proton (1H) images of hazelnut oil penetration into chocolate, and lithium ion (7Li) penetration into cement paste. The methods described in this paper provide a straightforward and reliable means for imaging a class of samples that, until now, have been very difficult to image.

Cacao↗

PubMed2002

Fat, moisture, and ethanol migration through chocolates and confectionary coatings.

The migration of fat, moisture, and ethanol is a common problem with chocolate-coated confectionery products. Migration of one of these components into the coating leads to visual and sensory defects such as sugar or fat bloom, making the product unacceptable to the consumer. The migration rate depends on the structure and composition of the coating. The migration of each of these species can be slowed to a certain extent by proper tempering of the coating, because proper tempering will give a structure that resists migration. In the continuous lipid phase, these chemical species migrate mainly through the liquid portion. Thus, the migration rate depends on the amount of liquid oil present in the product. Migration can be delayed either by reducing the liquid fat content or by immobilizing the liquid phase. The actual mechanisms for the migration processes are speculative, and a more thorough understanding is necessary to better abate quality deterioration. Armed with this understanding, a manufacturer would know a priori the effect of changing the ingredient or process. A few methods for control have been suggested, but have found limited application. Mathematical models have been proposed to predict the migration behavior, but their application is hindered because of the simplified assumptions employed. There is a need for developing better models that combine mass transfer with the phase behavior to be able to accurately predict the migration process. This review discusses the current understanding of fat, moisture, and ethanol migration through chocolate coatings and also includes a brief description of the theoretical aspects governing migration.

Cacao↗

PubMed2001

Optimizing detection of heat-injured Listeria monocytogenes in pasteurized milk.

Optimal conditions for the detection of heat-injured cells of Listeria monocytogenes in modified Pennsylvania State University (mPSU) broth were determined using a response surface design generated by a computer program, EChip. Different combinations of incubation temperatures and lithium, magnesium, and D-serine concentrations were evaluated to determine the optimum conditions for the detection of heat-injured L. monocytogenes in filter-sterilized whole milk inoculated with selected problematic background microflora. A concentration of 212 mM lithium chloride completely inhibited the growth of Enterococcus faecium while permitting recovery and detection of L. monocytogenes. A concentration of 15.8 mM MgSO4 was found to be optimum for the recovery and detection of L. monocytogenes. A concentration of 140.2 mM D-serine was found to completely inhibit the germination of Bacillus subtilis var. globii spores but not recovery and detection of L. monocytogenes. Under optimum concentrations of LiCl, MgSO4, and D-serine and in the absence of background microflora, the effect of incubation temperature on percentage detection was described by a second-order polynomial model, and 28 degrees C was determined to be optimal. In the presence of background microflora, the effect of incubation temperature on percentage detection of heat-injured cells was described by a third-order polynomial model, and 30 degrees C was found to be optimal. Optimizing the levels of highly specific and selective agents, nutrients, and incubation temperature in one recovery enrichment system dramatically increased the Listeria/background microflora ratio. This resulting medium, optimized PSU (oPSU) broth, greatly improved the detection of heat-injured and nonheat-injured L. monocytogenes by both conventional and molecular methods (Oxoid's Listeria Rapid Test, Gen-Probe's Accuprobe Listeria monocytogenes Culture Identification Test, and Qualicon's BAX for screening Listeria monocytogenes).

Animals↗

PubMed1998

Optimization of exopolysaccharide production by Lactobacillus delbrueckii subsp. bulgaricus RR grown in a semidefined medium.

The optimal fermentation temperature, pH, and Bacto-casitone (Difco Laboratories, Detroit, Mich.) concentration for production of exopolysaccharide by Lactobacillus delbrueckii subsp. bulgaricus RR in a semidefined medium were determined by using response surface methods. The design consisted of 20 experiments, 15 unique combinations, and five replications. All fermentations were conducted in a fermentor with a 2.5-liter working volume and were terminated when 90% of the glucose in the medium had been consumed. The population of L. delbrueckii subsp. bulgaricus RR and exopolysaccharide content were measured at the end of each fermentation. The optimum temperature, pH, and Bacto-casitone concentration for exopolysaccharide production were 38 degrees C, 5, and 30 g/liter, respectively, with a predicted yield of 295 mg of exopolysaccharide/liter. The actual yield under these conditions was 354 mg of exopolysaccharide/liter, which was within the 95% confidence interval (217 to 374 mg of exopolysaccharide/liter). An additional experiment conducted under optimum conditions showed that exopolysaccharide production was growth associated, with a specific production at the endpoint of 101.4 mg/g of dry cells. Finally, to obtain material for further characterization, a 100-liter fermentation was conducted under optimum conditions. Twenty-nine grams of exopolysaccharide was isolated from centrifuged, ultrafiltered fermentation broth by ethanol precipitation.

Culture Media↗

PubMed1983

Functionality of muscle constituents in the processing of comminuted meat products.

Emulsification through the creation of a fat dispersion and formation of an interfacial protein membrane at the fat-water interface is not the sole aspect responsible for comminuted meat "emulsion" stability. In addition, water binding which occurs initially during myofibrillar protein extraction from tissue disruption, and later during entrapment within the heat-induced protein gel matrix, must be included. The criteria that affect formation of the gel matrix adds another aspect, in that conditions for optimum protein-protein interaction also influence ultimate water and fat stabilization. Rheological considerations are in their infancy and will require future study, particularly during the transformation of a "flowing" batter into a "nonflowing" solid product. This review has been aimed at emphasizing that the myofibrillar protein component is the predominant constituent involved in an interactive role with water, fat, and itself, in forming the ultimate stabilized comminuted meat matrix.

Actinin↗