Formation of N-Nitrosopyrrolidine in Fried Bacon: Model System Studies

The kinetics of reactions such as the nitrosation of proline or pyrrolidine and the decarboxylation of proline or N-nitrosoproline in heated model systems simulating the pan-frying conditions of bacon were determined. The rate constants, half-life values and activation energy values of these reactions were calculated. The nitrosation of proline or pyrrolidine in adipose model systems occurs readily in the temperature range 80–160°C, while the decarboxylation of proline or N-nitrosoproline proceeds only at 100°C or above. The rates of the above reactions are such that nitrosation of proline > nitrosation of pyrrolidine > decarboxylation of proline or N-nitrosoproline. Results lend credence to the pathway involving N-nitrosoproline in the formation of N-nitrosopyrrolidine in bacon.     

EFFECT OF DIETARY COMPONENTS AND SURFACE APPLICATION OF OLEORESIN ROSEMARY ON LIPID STABILITY OF RAINBOW TROUT (Oncorhynchus mykiss) MUSCLE DURING REFRIGERATED AND FROZEN STORAGE

The effect of dietary supplementation with α-tocopherol and surface application of oleoresin rosemary on the lipid stability of rainbow trout ( Oncorhynchus mykiss ) muscle during refrigerated storage (4C) and frozen storage (−20C) for 8 days and 6 months, respectively, was investigated. A significant (p < 0.05) reduction in α-tocopherol concentrations in muscle tissue during frozen storage was observed. The 2-thiobarbituric acid-reactive substances (TBARS) values of muscle samples, with or without surface application of oleoresin rosemary, increased during storage for all dietary groups. A significant (P < 0.05) interaction between dietary treatments and the time of storage was observed. Muscle tissue from fish receiving a dietary supplement of 500 mg/kg diet had the lowest TBARS values. The oxidative stability of the lipids was further improved by applying oleoresin rosemary to the surface of the fish fillets.     

Segmentation of confocal microscope images of cell nuclei in thick tissue sections

Segmentation of intact cell nuclei from three-dimensional (3D) images of thick tissue sections is an important basic capability necessary for many biological research studies. However, segmentation is often difficult because of the tight clustering of nuclei in many specimen types. We present a 3D segmentation approach that combines the recognition capabilities of the human visual system with the efficiency of automatic image analysis algorithms. The approach first uses automatic algorithms to separate the 3D image into regions of fluorescence-stained nuclei and unstained background. This includes a novel step, based on the Hough transform and an automatic focusing algorithm to estimate the size of nuclei. Then, using an interactive display, each nuclear region is shown to the analyst, who classifies it as either an individual nucleus, a cluster of multiple nuclei, partial nucleus or debris. Next, automatic image analysis based on morphological reconstruction and the watershed algorithm divides clusters into smaller objects, which are reclassified by the analyst. Once no more clusters remain, the analyst indicates which partial nuclei should be joined to form complete nuclei. The approach was assessed by calculating the fraction of correctly segmented nuclei for a variety of tissue types: Caenorhabditis elegans embryos (839 correct out of a total of 848), normal human skin (343/362), benign human breast tissue (492/525), a human breast cancer cell line grown as a xenograft in mice (425/479) and invasive human breast carcinoma (260/335). Furthermore, due to the analyst's involvement in the segmentation process, it is always known which nuclei in a population are correctly segmented and which not, assuming that the analyst's visual judgement is correct.     

Atmospheric corrections for remotely-sensed thermal data in a cool humid temperate zone

Abstract

This research emphasizes the necessity of carrying out atmospheric corrections in order to obtain accurate absolute temperature values for terrestrial objects, from remotely-sensed data. Satellite data were available for thermal band 6 on Landsat-5. They were complemented by simultaneously-acquired airborne and ground-truth data. Radiosonde data were fed into the computer program LOWTRAN 6. The ground-based data indicated that the use of the LOWTRAN 6 model applied to low-level airborne measurements was very satisfactory (variations of only 0·01-0·61 deg K being noted). However, for the satellite-borne detector the results were much less satisfactory (variations of 0·26-2·05 deg K), because of lower radiometric and spatial resolving power.     

FORMATION OF N-NITROSAMINES IN LOW MOISTURE SYSTEMS

Experiments have shown that N-nitrosamines can be formed when sodium nitrite and dialkylamines are heated in low-moisture model systems. Parameters which may influence the reaction were investigated. Results revealed that maximum N-nitrosamine formation depended on temperature and time of heating, sodium nitrite-amine ratio and pH of the system.     

Extrudates of Starch-Xanthan Gum Mixtures as Affected by Chemical Agents and Irradiation

Mixtures of starch, xanthan gum and either polyvinyl alcohol, epichlorohydrin, valeric acid or adipoyl chloride were extruded. Properties of extrudates including apparent viscosity, water solubility, water absorption indices and exrudate expansion were measured for different proportions of xanthan gum, 70% amylose starch (with or without irradiation) and chemical agents. Extrusion with chemical agents and irradiation changed physical properties of both starch and xanthan gum. Expansions of extrudates were higher than that of starch. Viscosity of extrudates increased with xanthan gum concentration. The addition of 1% (w/w) polyvinyl alcohol had the greatest effect of the chemical agents. Irradiation increased the apparent viscosity of starchxanthan gum mixtures.     

Inhibition of N-Nitrosopyrrolidine in Dry Cured Bacon by α-Tocopherol-Coated Salt Systems

Dry cured bacon was made under carefully controlled processing conditions in a pilot plant study using α-tocopherol-coated salt as part of the dry cure. Approximately, a 96% reduction in N-nitrosopyrrolidine (NPYR) levels in the fried bacon was achieved with an ingoing α-tocopherol level of 500 mg/kg. NPYR levels in the cookout fat were reduced approximately 92% using the same level of α-tocopherol. Bacon, prepared by a small scale commercial operation, also contained reduced levels of NPYR when processed with α-tocopherol-coated salt, despite high levels (>100 mg/kg) of residual sodium nitrite in the finished bacon. Results comparing effectiveness of α-tocopherol and mixed tocopherols as nitrosamine blocking agents were inconclusive. Although, α-tocopherol appeared to be more effective as a blocking agent (91% versus 73% inhibition of NPYR), the difference in percent inhibition achieved could possibly be attributed to apparently lower levels of residual mixed tocopherols in the finished bacon.     

Detection of irradiation in scampi tails — effects of sample preparation, irradiation dose and storage on ESR response in the cuticle

This paper describes the potential of using ESR spectroscopy for the identification of irradiated scampi (Norway lobster) using the signal induced in the cuticle at 349.5 mT. Freeze-drying the cuticle gave a larger signal than air-drying, and peak height was found to be a more reliable method of quantification than double integration of the peak. There was a linear response with increasing irradiation dose. Samples were stored intact at –20°C and +5°C and as dry shell at room temperature for up to 84 d and it was observed that signal intensity was reduced with increased storage time and higher temperature, especially at the higher doses. Thus ESR spectroscopy can be used to detect irradiation in scampi cuticle and has potential for the estimation of irradiation dose.     

Evaluation of a Water Jet Cutting System for Slicing Potatoes

A water jet cutting machine was used to slice potato tubers, and characteristics of the cut surfaces were studied. Irregularities on the cut face were visualized by staining with a nonspecific protein stain. The amount of protein extractable from the cut face was measured and used to quantitate the cellular damage resulting from different water jet operational conditions. Observations were confirmed with scanning electron microscopy. A wide range of water jet settings could be used to cut potato slices. French fries cut with the water jet set to cause intermediate subsurface damage had increased color irregularities but no extreme taste or textural differences compared to conventionally cut controls.