Abrupt change in radiation-width distribution for 147Sm neutron resonances.

We obtained the total radiation widths of s-wave resonances through an R-matrix analysis of (147)Sm(n,γ) cross sections. Distributions of these widths differ markedly for resonances below and above E(n)=300 eV, which is in stark contrast to long-established theory. We show that this change, as well as a similar change in the neutron-width distribution reported previously, is reflected in abrupt increases in both the average (147)Sm(n,γ) cross section and fluctuations about the average near 300 eV. Such effects could have important consequences for applications such as nuclear astrophysics and nuclear criticality safety.

149Sm(n,α)146Nd cross sections in the MeV region.

We have measured the (149)Sm(n,α)(146)Nd cross section at 4.5, 5.0, 5.5, 6.0, and 6.5 MeV. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University with monoenergetic neutrons produced via the (2)H(d,n)(3)He reaction using a deuterium gas target. Alpha particles were detected with a double-section gridded ionization chamber having two back-to-back (149)Sm(2)O(3) samples attached to the common cathode. Absolute neutron flux was measured using a small (238)U fission chamber and monitored by a BF(3) long counter. These are the first reported cross sections for this reaction at these energies, except at 6.0 eV, where our new data are in good agreement with our earlier result. The present results help to much better constrain the (149)Sm(n,α)(146)Nd cross section in a region where its energy dependence is changing fairly rapidly and there are large differences between evaluated nuclear data libraries.

Anomalous fluctuations of s-wave reduced neutron widths of 192,194Pt resonances.

We obtained an unprecedentedly large number of s-wave neutron widths through R-matrix analysis of neutron cross-section measurements on enriched Pt samples. Careful analysis of these data rejects the validity of the Porter-Thomas distribution with a statistical significance of at least 99.997%.

Neutron cross section measurements at ORELA for improved nuclear data and their application.

To support the Nuclear Criticality Safety Program, the Oak Ridge Electron Linear Accelerator (ORELA) has been used to measure the total and capture neutron cross sections of several nuclides in the energy range from 100 eV to -600 keV. Concerns about the use of existing cross section data in nuclear criticality calculations have been a prime motivator for the new cross-section measurements. Our new capture cross sections of aluminium, silicon, chlorine, fluorine and potassium in the energy range from 100 eV to 600 keV are substantially different from the cross sections in evaluated nuclear data files of ENDF/B-VI and JENDL-3.2.

Evaluation of induced color changes in chicken breast meat during simulation of pink color defect.

The objective of the study was to establish a pink threshold and simulate the pink defect in cooked chicken breast meat with treatment combinations that would induce significant changes in the color of raw and cooked meat. The subjective pink threshold used in judging pink discoloration was established at a* = 3.8. Samples of three color groups (normal, lighter than normal, and darker than normal) of boneless, skinless chicken breast muscles were selected based on instrumental color values. The in situ changes were induced using sodium chloride, sodium tripolyphosphate, sodium erythorbate, and sodium nitrite at two levels: present and not present. Fillets in all treatments were subjected to individual injections, followed by tumbling, cooking, and chilling. Samples were analyzed for color [lightness (L*), red/green axis (a*), yellow/blue axis (b*)] and reflectance spectra. Simulation of the pink defect was achieved in eight of the 16 treatment combinations when sodium nitrite was present and in an additional two treatment combinations when it was absent. Pinking in cooked samples was affected (P < 0.05) by L* of raw meat color. Results confirmed that it was possible to simulate the undesired pinking in cooked chicken white meat when in situ conditions were induced by sodium chloride, sodium tripolyphosphate, and sodium nitrite. The continuation of the simulation study can aid in developing alternative processing methods to eliminate potential pink defects.

Cross section measurement for the (95)Mo(n, alpha)(92)Zr reaction at 4.0, 5.0 and 6.0MeV.

Measurements of cross sections of the (95)Mo(n, alpha)(92)Zr reaction at E(n)=4.0, 5.0 and 6.0MeV were carried out at the 4.5MV Van de Graaff of Peking University, China. A twin gridded ionization chamber and two large-area (95)Mo samples were adopted. Fast neutrons were produced through the D(d, n)(3)He reaction by using a deuterium gas target. A small (238)U fission chamber was employed for absolute neutron flux determination. Present data are compared with existing evaluations and measurement.

Histamine in cat foods: survey and comparison of methodologies.

Histamine concentrations were determined in semi-moist and moist cat foods which listed fish or fish solubles as one of the ingredients using the AOAC fluorometic method and a TLC procedure. Percent recovery was 73% for the AOAC and 96% for the TLC procedure, although the coefficient of variation was lower for AOAC procedure. Moist cat foods contained an average of 11 ppm histamine while semi-moist cat foods had 23 ppm histamine. High histamine content of semi-moist cat food was probably due to condensed fish solubles even though it was not one of the major ingredients. The maximum amount of histamine observed was 88.8 ppm in a semi-moist cat food sample while the minimum was 3.8 ppm in a moist cat food sample. Results from both procedure compared well.

Effect of Salt Concentration and Incubation Temperature on Formation of Histamine, Phenethylamine, Tryptamine and Tyramine During Miso Fermentation.

Two factors, salt concentration and incubation temperature, were examined for their effect on the formation of histamine, phenethylamine, tryptamine and tyramine during miso (soybean paste) fermentation. Misos containing 5 and 10% NaCl were prepared and incubated at 25 and 35°C. The effect of each factor was determined from the chemical and microbiological changes in the misos during fermentation. Salt level was a significant factor in the formation of amines. Higher amine levels were found in low-salt (5% NaCl) formulations than in high-salt (10% NaCl) misos. Incubation temperature within the range of 25 to 35°C during fermentation had little effect on amine formation in misos.

Influence of temperature cycling on the production of aflatoxins B1 and G1 by Aspergillus parasiticus.

The effect of temperature cycling on the relative productions of aflatoxins B1 and G1 by Aspergillus parasiticus NRRL 2999 was studied. The cycling of temperature between 33 and 15 degrees C favored aflatoxin B1 accumulation, whereas cycling between 35 and 15 degrees C favored aflatoxin G1 production. Cultures subjected to temperature cycling between 33 and 25 degrees C at various time intervals changed the relative productions of aflatoxins B1 and G1 drastically. Results obtained with temperature cycling and yeast extract-sucrose medium with ethoxyquin to decrease aflatoxin G1 production suggest that the enzyme system responsible for the conversion of aflatoxin B1 to G1 might be more efficient at 25 degrees C than at 33 degrees C. The possible explanation of the effect of both constant and cycling temperatures on the relative accumulations of aflatoxins B1 and G2 might be through the control of the above enzyme system. The study also showed that greater than 57% of aflatoxin B1, greater than 47% of aflatoxin G1, and greater than 50% of total aflatoxins (B1 plus G1) were in the mycelium by day 10 under both constant and cyclic temperature conditions.

Production of aflatoxins B1 and G1 by Aspergillus flavus and Aspergillus parasiticus isolated from market pecans.

One hundred and forty-eight isolates of Aspergillus flavus and A. parasiticus were isolated from 5,608 pecans obtained from Chicago and Georgia markets. The percentage of internal contamination by these species was 7.3% in the Chicago market pecans and 1.7% in those from markets in Georgia. Of the 148 isolates, 93% of the A. parasiticus, but only 54% of the A. flavus, were capable of producing aflatoxin. Overall, 57% of the isolates were potentially aflatoxigenic. A. parasiticus isolates generally produced a greater amount of aflatoxins than A. flavus.

Toxigenic aspergilli and penicillia isolated from aged, cured meats.

Eighty-nine cultures of Aspergillus and 54 cultures of Penicillium isolated from aged, cured meats were tested for toxicity to chicken embryos. Two of 22 isolates of A. ruber, 5 of 28 A. repens, 2 of 12 A. sydowi, 1 of 12 A. restrictus, 2 of 7 A. amstelodami, 1 of 2 A. chevalieri, and an A. fumigatus isolate exhibited toxicity. Similarly, 2 of 15 isolates of P. expansum, 1 of 3 P. notatum, 1 of 2 P. brevi-compactum, and 1 of 8 Penicillium spp. were found to be the most toxic. Among these fungi, the chloroform extract from the growth of an A. sydowi isolate showed the greatest toxicity. There was no direct or indirect evidence that aged, cured meats contain toxic metabolites.

Production of citrinin by Penicillium viridicatum on country-cured ham.

Seven strains of Penicillium viridicatum isolated from country-cured ham produced citrinin in potato dextrose broth and on country-cured ham. None of the strains produced detectable amounts of citrinin at 10 C. The optimal temperature range for citrinin production was 25 to 30 C.

Isolation and identification of xanthotoxin (8-methoxypsoralen) and bergapten (5-methoxypsoralen) from celery infected with Sclerotinia sclerotiorum.

Methods for the production, isolation, and identification of xanthotoxin and bergapten from celery diseased by Sclerotinia sclerotiorum (Libert) de Bary were investigated. The only conditions under which this mold was capable of producing xanthotoxin and bergapten occurred when the mold was actively growing on fresh (metabolizing) celery. Neither compound was found in uninfected celery, in the mold growing on nutrient media, on nutrient media fortified with 30% filter-sterilized celery juice, or on nonmetabolizing celery. Maximal xanthotoxin production of 320 mug per g of dry rotted celery occurred at 20 C, although mycelial growth increased until 30 C. Neither xanthotoxin nor bergapten was found when the mold grew on 11 agricultural commodities other than celery.

Identification and aflatoxin production of molds isolated from country cured hams.

Of 562 molds isolated from country cured hams, 403 isolates were of the genus Penicillium, 121 were Aspergillus, and 36 were Cladosporium, Alternaria, and other genera.

Persistence of aflatoxin during the fermentation of soy sauce.

Aflatoxin was produced by Aspergillus parasiticus NRRL 2999 but not by A. oryzae during fermentation of soy sauce. Little aflatoxin was degraded within 6 weeks unless Lactobacillus delbrueckii also was present.

Production of ochratoxins A and B on country cured ham.

Two strains of Aspergillus ochraceus and six of Penicillium viridicatum isolated from country cured hams were screened for production of ochratoxins A and B. None of the isolated P. viridicatum strains yielded detectable amounts of ochratoxin A or B, whereas both strains of A. ochraceus produced ochratoxins A and B on rice, defatted peanut meal, and country cured ham. After 21 days of incubation on ham, one-third of the toxin was found in the mycelial mat on the ham surface, whereas two-thirds had penetrated into the meat to a distance of 0.5 cm.

Influence of Temperature and Water Activity on Aflatoxin Production by Aspergillus flavus in Cowpea ( Vigna unguiculata ) Seeds and Meal.

Experiments were done to determine the influence of temperature (21, 30 and 37°C) and aw (0.76 to 0.98) on aflatoxin production by Aspergillus flavus on cowpea ( Vigna unguiculata ) seeds, meal and meal supplemented with onion. Larger quantities of aflatoxin were produced at 21 and 30°C than at 37°C. The highest amount of aflatoxin (2777 µg/20 g, dry weight basis) was observed in meal containing onion at aw 0.98 after 20 d of incubation at 21°C. A level of 870 |µg/20 g was detected in seeds at aw 0.95 after 14 d of incubation at 30°C. Meal at aw 0.96 supported production of 551 µg of aflatoxin per 20 g after 20 d at 30° C. Temperature had little influence on the optimal aw for aflatoxin production in cowpea meal. However, an increase in temperature resulted in a decreased optimal aw for aflatoxin production on whole cowpeas. When known quantities of aflatoxin were added to cowpea meal which was subsequently steamed for 5 min, only 29% was extractable using a variety of procedures, indicating that the toxin may be bound in some manner to cowpea constituents as a result of heat treatment.