Development of a Colorimetric, Second Generation Nucleic Acid Hybridization Method For Detection of Salmonella in Foods and a Comparison With Conventional Culture Procedure

A new, highly specific colorimetric DNA hybridization method (cDNAH) for detection of Salmonella in foods was developed. It detected 355/362 strains representing 206/213 serovars of Salmonella, and showed no cross-reactivity with 32 different non-Salmonella species, including a variety of Enterobacter and Citrobacter species. The cDNAH method was compared with the BAM/AOAC culture method in two studies: (1) with 20 different inoculated and uninoculated foods overall agreement between the two methods was 99%. (2) with naturally contaminated foods at two independent sites agreement with culture was 99.8% where 9/404 samples were positive for Salmonella.     

Fluctuations in light intensity modulate ion fluxes from grape berry mesocarp: direct evidence from microelectrode ion flux estimations

Canopy architecture and light spectral composition have long been considered as important factors determining grape juice acidity and K+concentrations. In this study, we provide direct evidence that fluctuations in intensity of light incident on berry tissue may significantly modulate net ion fluxes from and into the berry mesocarp. The MIFE technique was used to quantify fluxes of K+, H+, and Ca²⁺in Pinot Noir and Emperor grape berries. Transition from dark to light induced complex multiphase kinetics of K+flux resulting in significant shift towards net K+uptake by the peripheral mesocarp tissue. When light intensity was modulated in a square-wave manner with a period of 5 to 15 min (mimicking periodicity of natural variations during a typical autumn day in Hobart), K+flux oscillated with the same frequency and a magnitude of about 100 nmol/m²s. Changes in H+and Ca²⁺fluxes showed high positive (R = 0.8) and negative (R = 0.9) correlation, respectively, with those in K+. To the best of our knowledge, these data from excised fruit provide the first reported evidence that light directly incident on bunches may modulate apoplasmic pH and K+concentration in grape. Possible underlying mechanisms are discussed.     

PORCINE LONGISSIMUS GLYCOLYTIC POTENTIAL LEVEL EFFECTS ON GROWTH PERFORMANCE, CARCASS, AND MEAT QUALITY CHARACTERISTICS

Animals (n = 72) with longissimus glycolytic potential (GP) values ranging from 113.8 to 301.1 μmol/g of tissue, were classified as having low (n = 24), moderate (n = 24), and high (n = 24) GP levels. Meat quality measurements such as longissimus ultimate pH and subjective color score decreased, while Hunter L* values, percentage drip loss and purge loss increased for animals classified as having either high or moderate GP levels compared to those with low GP values. Animals with higher GP had decreased longissimus protein content and improved taste panel tenderness scores and lower shear force indicating superior eating quality. Increasing aging time from 2 to 21 days decreased shear force and improved taste panel tenderness scores. These data indicate that both glycolytic potential level within the muscle and aging time can have significant effects on pork quality characteristics.     

QUANTITATIVE DETERMINATION OF COMPOSITION OF MODELS OF FOOD SYSTEMS BY THE INFRARED ATTENUATED TOTAL REFLECTANCE TECHNIQUE

SUMMARY– Attenuated total reflectance (ATR), offering a possible rapid infrared spectrophoto-metric method for quantitative measurements of major nutritional components in foods materials, was employed in this study for evaluating composition of model systems representing solid foods: system #1-starch and protein; system #2-starch, protein and fat. Using a band ratio technique, correlations were determined between the ratio of intensities for carbohydrate and protein peaks and their proportion in the systems studied. When the log of the ratio of these two peaks was plotted against the composition, correlation coefficients of .9699 and .9358 for systems #1 and #2 respectively were obtained. Errors assignable to the systems'composition and those inherent to the ATR technique are discussed.     

Temperature Effect on Binding of Volatile Flavor Compounds to Soy Protein in Aqueous Model Systems

The thermodynamics of binding was determined for soybean glycinin and β-conglycinin and flavor ligands butanal, pentanal, hexanal, octanal, 2- and 3-hexanone, 2- and 5-nonanone, hexanol, and hexane. Hexane had affinity for these proteins only at 5^oC. Affinities of binding for all flavor ligands were greater for glycinin than β-conglycinin. Affinity for aldehydes increased with increasing chain length for glycinin, but remained constant for β-conglycinin. ΔG^o, ΔH^o, and ΔS^o for binding were determined. ΔG^o was negative for all ligands and ranged from ?1.74 to ?4.16 Kcal/mol. All enthalpies of binding were positive except butanal and hexanol. Change in free energy of binding per CH₂ in homologous aldehydes was greater for glycinin than β-conglycinin.     

Magnetic Properties of an Amorphous Antiferromagnet

The magnetic and physical properties of the amorphous antiferromagnetic MnO-P₂O₅ glass system were investigated. The glasses were found to be microstructurally homogeneous and amorphous within the detection limit of vacuum Guinier-De Wolff X-ray tenchiques. The magnetic properties of the glasses are interpreted in terms of antiferromagnetically coupled Mn²⁺ ions, which experience negative exchange interactions with 1,2, or 3 near neighbors, and structurally isolated Mn²⁺ ions, which experience weak exchange interactions. The ions which experience weak exchange interactions produce a downward curvature of the inverse-susceptibility-vs-temperature plot at low temperatures. The magnetization-vs-field data exhibit curvature toward the field axis, and the magnetization increases as the temperature is decreased to 1.73°K. Below this temperature, the magnetization becomes weakly temperature-dependent, and the M-vs-H curves almost superimpose. These results are interpreted in terms of a 2-spin Heisenberg model of antiferromagnetism.     

Effects of Brain Destruction on Post Harvest Muscle Metabolism in the Fish Kahawai (Arripis trutta)

Brain destruction followed by immediate chilling of troll-caught kahawai delayed the onset of rigor by 73 min. It also resulted in the lowest measured pH in white muscle during rigor being reached after 1500 min compared with only 500 min for untreated fish. This difference in pH appeared to correlate with differences in lactic acid levels during rigor. Brain destruction also considerably increased the time at which significant amounts of ATP could be found in white muscle. High pH and ATP levels particularly during the chilling phase may contribute to retention of flesh translucency for longer periods.