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.     

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.     

Subject: 'Skim milk' Technology of skimmed milk evaporation

The paper seeks to show how the requirements of skimmed milk concentration are met in modern evaporators and how the type of plant used has developed over the years, the falling film tubular evaporator now being virtually standard. Very economical operation is now possible with sophisticated multiple-effect plants with thermocompression, and further economies are possible with mechanical vapour recompression. The importance of adequate wetting of heat transfer surfaces is discussed with regard to length of run and achievable concentration, and methods of maintaining correct wetting conditions are illustrated. Preheating is an important feature of such evaporators for both economy and control of final powder properties, and the methods adopted are described, Finally, the control of modern skimmed milk evaporators is considered briefly.     

Qualitative Aspects of Pear Flavor

Fire blight is th major disease affecting pear production in Ontario. Pear varieties which have been bied for resistance to this disease all lack the flavor quality of Bartlet pears. This study is the first in a series designed to generate information required to develop a fire blight resistant pear possessing acceptable flavor when processed. Sensory evaluation was utilized to select Bartlett, Magness, and Kieffer pears as the highly, intermediate, and poorly flavored varieties to be used for all subsequent analyses. Ultraviolet spectroscopy, liquid and gas chromatography confirmed distinct qualitative and quantitative differences in volatile flavor constituents. Production of flavor constituents by maturing Bartlett pear was also examined. Flavor compounds were synthesized when Bartlett pear puree was incubated with C₁₈-unsaturated fatty acids. A synthesis of some flavor constituents also occurred when a Kieffer pear puree was incubated with Bartlett pear enzymes.     

Effect of Antioxidants on Lipid Stability in Restructured Beef Steaks

Two natural antioxidant formulations–containing mixed tocopherols, ascorbyl palmitate and citric acid–and TBHQ were evaluated in restructured beef steaks formulated to contain 18% fat and 0.75% NaCl. Lipid oxidation was monitored over 12 months of frozen storage. TBHQ significantly (p < 0.05) lowered TBA numbers in raw and freshly cooked samples and in samples that were cooked and held 4 hr at 4°C. Natural antioxidants provided significant (p <0.05) protection in freshly cooked meat and were as effective as TBHQ in retarding lipid oxidation. Sensory evaluation and GC quantitation of hexanal were also used to monitor oxidation but the correlation between the three methods was not significant.     

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.     

Photooxidation of Cholesterol in Butter

The effect of exposure to fluorescent light on the oxidative stability of cholesterol in unpackaged butter was investigated. Oxidation of cholesterol in butter occurred, although the oxidation products were detectable only after prolonged exposure to light. Cholesterol oxides were more concentrated at the surface than throughout the entire butter block and were detectable after 8 days of exposure to light. 5-Cholesten-313, 7α-diol and its 7β-epimer, products of free radical attack on cholesterol, were detected among the oxidation products, along with a compound suspected to be 6-cholesten-3β, 5α-diol. This latter compound is only known to form following singlet oxygen attack on cholesterol.     

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.