Properties of poly(vinyl alcohol)–borax gel doped with neodymium and praseodymium

Neodymium and praseodymium ions, singly and in combination, have been doped into a poly(vinyl alcohol)–borax matrix. X-ray diffraction shows structural correlations from 2 to 6 Å and 15 Å, while small angle neutron scattering indicates that the rare-earth ions do not affect the nanoscale structures of the gels. Differential scanning calorimetry shows the glass transition temperature to increase with concentration of Pr in the gel. Excitation in the ultraviolet region leads to luminescent emission in the visible region. Simultaneous absorption in the visible region then leads to luminescent emission in the near infra-red region. The spectral qualities of the emission bands can be varied by choosing appropriate relative ratios of rare-earth species.     

A MODEL FOR C-CALCULUS

C-calculus was introduced by the first author as a technique for the analysis of complex hierarchical systems.² It has been further applied as a versatile tool in pattern recognition.^1,3 Our present aim is to exhibit a model for C-calculus, and deal with its convergence and filtering properties.     

POSTMORTEM CHANGES IN CYTOSKELETAL ELEMENTS OF FISH MUSCLE1

Transmission electron microscopic examination of samples from fresh and 7 days-cold-stored white croaker skeletal muscle did not reveal apparent changes in overall structure of contractile elements of muscle. However, when purified myofibrils obtained from fresh and stored muscles were extracted with 0.6 M KI and the residues were examined in the scanning electron microscope, a progressive disappearance of exosarcomeric longitudinal filaments connecting successive Z structures was observed. Electrophoretic analysis of myofibrillar proteins obtained from fresh and stored muscles showed a marked degradation of nebulin, a major component of the endosarcomeric cytoskeletal network, whereas the other protein constituents of myofibrils remained practically unchanged. These alterations in elements of both cytoskeletal lattices of muscle may have important effects on physical properties of fish meat.     

MICROFLORA CHANGES IN MODIFIED-ATMOSPHERE-PACKAGED BROCCOLI FLORETS STORED AT REFRIGERATED TEMPERATURE

Changes in the microflora of packaged (Resinite VF-71 film) and nonpackaged broccoli florets held at 8C for 7 days were analyzed. Oxygen and carbon dioxide concentrations, aerobic plate, coliform yeast/mold counts, and overall quality were determined. Level of O₂ decreased from 15.58 to 5.15%, while CO₂ increased from 2.88 to 8.22% after 94 h of storage. Within each microorganism group, similar growth trends were observed between the packaged and nonpackaged samples; however, the packaged samples consistently exhibited a statistically significant (p ≤ 0.05) lower microbial count compared with nonpackaged samples throughout the storage period. Packaged and nonpackaged florets retained their green color and no off-odor was detected; however, the nonpackaged florets were found to be less crispy than the packaged samples.     

Cryopreservation of <i>Cyrtopodium hatschbachii</i> Pabst (Orchidaceae) immature seeds by encapsulation-dehydration

The aim of the present study was to investigate the efficiency of the encapsulation-dehydration technique for cryopreservation of Cyrtopodium hastchbachii Pabst seeds. Immature seeds of this species were cryopreserved by an encapsulation-dehydration technique. Seeds of five immature pods, 120 days after pollination, were encapsulated in 3% calcium alginate matrix and pretreated in liquid medium supplemented with 0.08 M sucrose (24 h), 0.15 M sucrose (24 h), 0.25 M sucrose (48 h), 0.5 M sucrose (24 h) and 0.75 M sucrose (24 h) in shaker at 60 rpm. Alginate beads were dehydrated 5 h in silicagel and immersed in liquid nitrogen for 12 h. Cryopreserved beads were thawed at 30°C for 1 min, rehydrated using the same liquid mediums [0.75 M sucrose (24 h), 0.5 M sucrose (24 h), 0.25 M sucrose (48 h) and 0.15 M sucrose (24 h)] and cultivated in half strength Murashige & Skoog medium (1962) with the addition of 2 g/L activated charcoal. Sixty four percent of seeds survived and developed into acclimatized plants after being cryopreserved. In this work, the encapsulation-dehydration technique was employed for first time in Cyrtopodium hatschbachii.     

Effect of heat treatment on the antibacterial activity of bovine lactoferrin against three foodborne pathogens

The effect of different heat treatments on the antimicrobial activity of bovine lactoferrin against Escherichia coli O157:H7, Salmonella enteritidis and Listeria monocytogenes has been studied. We have observed that the heat treatments lower than 85°C for 10 min did not affect the antibacterial activity of the protein. Hydrolysates of bovine lactoferrin were found to be more active than the native protein against the three pathogens. Moreover, the antibacterial effect of bovine lactoferrin was also assayed in milk and whey, and although we found a reduction in the number of viable cells, this reduction was lower than in culture media.     

Proteolytic activity among psychrotrophic bacteria isolated from refrigerated raw milk

Psychrotrophic bacteria were isolated from refrigerated raw milk from a processing plant in Southern Brazil. Psychrotrophic counts were between 4.9 and 7.8 log cfu/mL, and 5.3 to 7.2 log cfu/mL, for samples collected at the truck and the milk storage silo, respectively. Among the bacterial isolates, 90% were Gram-negative. Most strains presented low proteolytic activity, but strains of Burkholderia cepacia, Klebsiella oxytoca and Aeromonas sp. showed higher than 20 U/mL on azocasein as substrate. Crude proteases from selected strains were resistant to conventional heat treatments and caused coagulation of UHT milk after 5 days storage at room temperature.     

THERMAL INACTIVATION OF SALMONELLA ENTERITIDIS BY BOILING AND FRYING EGG METHODS

Salmonella enteritidis was cultivated in egg yolks and submitted to boiling and frying methods commonly used in domestic conditions in the south of Brazil. The results have demonstrated a rapid growth of the microorganism reaching counts of 9.0 log₁₀at 168 h. When contaminated shell eggs were placed in water and slowly heated, a population of approximately 7.0 log₁₀was completely inactivated after boiling for 1 min. However, in eggs placed directly in boiling water, the reduction was only 1.35 log₁₀after 1 min, and the entire population was eliminated after 3 min. A reduction of approximately 2.78 log₁₀was observed after frying for 1.5, 2.0 and 2.5 min. Even though the solidification of yolk has been pointed out as an indicator of S. enteritidis elimination in egg yolks, attention should be given to frying procedures, as considerable high levels of this microorganism could be recovered even from solidified yolks.     

Seasonal and Storage Effects on Color of Red-Fleshed Grapefruit Juice

Seasonal and storage characteristics of the juice from four red-fleshed grapefruit (citrus paradisi macf.) cultivars; Ruby Red, Henderson, Ray, and Star Ruby were determined and compared in a search for cultivars having juice with less tendency to fade as the fruit matures and on juice storage. Analyses of the single strength processed juice showed the cultivars to be similar except for lycopene and carotene values. Lycopene, the major pigment in pink and red grapefruit, declined 0.75–0.68 mg/100g, 0.36–0.25 mg/100g, 0.36–0.30 mg/100g and 0.14–0.08 mg/100g for Star Ruby, Henderson, Ray, and Ruby Red, respectively, as the season progressed. Storage of processed juice for 12 months revealed no major decrease in lycopene.