COMPARISON OF TWO SIMPLE METHODS FOR THE MEASUREMENT OF DETECTION THRESHOLDS FOR BASIC, UMAMI AND METALLIC TASTES

Two simple methods were followed to determine detection thresholds for the taste of substances in aqueous solution. The methods applied were: a modification of the ascending method of limits and a method based on the use of scales. Detection thresholds were calculated for the four basic tastes (sweet, salty, acid, and bitterness), umami and metallic. Reference substances for each taste were sucrose, sodium chloride, citric acid, caffeine, monosodium glutamate and iron (II) sulfate heptahydrate and the results of the two methods were compared. We found that the threshold values calculated by method ASTM-679 was within the range of concentrations identified with the scales method.     

Seasonal variation of carrageenans in tetrasporic,cystocarpic and ‘sterile’ stages of Gigartina skottsbergii S. et G. (Rhodophyta,Gigartinales)

Cystocarpic and sterile plants of Gigartina skottsbergii produce -carrageenans, while tetrasporophytes produce -carrageenans. No seasonal variation in the carrageenan yields in the three stages was evident. Yields were clearly higher in cystocarpic (34.1–64.7%) and sterile samples (32.3–71.8%) than in tetrasporic plants (10.1–34.0%). Chemical characteristics of the polysaccharides for any stage are the same throughout the year.The authors are Research Members of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.The authors are Research Members of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.     

Room temperature, low-field C-n.m.r. spectra of degraded carrageenans. Part II. On the specificity of the autohydrolysis reaction in kappa/iota and mu/nu structures

A kappa/iota carrageenan from Gigartina skottsbergii and a partially cyclized mu/nu carrageenan from Iridaea undulosa were submitted to autohydrolysis. The ¹³C-n.m.r. spectra of the degraded products give structural information on the polysaccharides and show clearly that besides the known splitting of 3,6-anhydrogalactosidic linkages, the linkage between - -galactose 2,6-disulphate and β- -galactose 4-sulphate is cleaved with similar specific reaction rate.     

Sulfated galactans from the red seaweed Nothogenia fastigiata (Nemaliales,Rhodophyta)

Fractionation of the cetrimide salts of the sulfated polysaccharides of Nothogenia fastigiata led to the isolation of a complex galactan sulfate. This product showed compositional and molecular weight heterodispersion together with composition-, temperature-, time-, and conformation-dependent molecular associations. In this sense, the behavior of the galactan sulfate is similar to that of the mannan sulfate previously isolated from the same seaweed.Formerly classified as Chaetangium fastigiatum.     

The structure of an α-D-glucan from Cyttaria harioti Fischer

A homogeneous glucan has been isolated from the fruiting bodies of Cyttaria harioti Fischer. Partial acid hydrolysis produced major amounts of isomaltose, whereas acetolysis gave maltose and maltotriose. Enzymic hydrolysis with amylo-glucosidase and pullulanase indicated a structure based on maltotriose residues connected by (1→6)-α-D linkages. This conclusion was supported by periodate-oxidation data which also showed that 3–7% of the glucose resisted oxidation. Methylation analysis confirmed the presence of (1→6) and (1→4) linkages in the ratio 1:2.4.     

Strain-specific differences in <Emphasis Type="Italic">Neisseria gonorrhoeae</Emphasis> associated with the phase variable gene repertoire

Background  

There are several differences associated with the behaviour of the four main experimental Neisseria gonorrhoeae strains, FA1090, FA19, MS11, and F62. Although there is data concerning the gene complements of these strains, the reasons for the behavioural differences are currently unknown. Phase variation is a mechanism that occurs commonly within the Neisseria spp. and leads to switching of genes ON and OFF. This mechanism may provide a means for strains to express different combinations of genes, and differences in the strain-specific repertoire of phase variable genes may underlie the strain differences.     

Genetic islands of <Emphasis Type="Italic">Streptococcus agalactiae</Emphasis> strains NEM316 and 2603VR and their presence in other Group B Streptococcal strains

Background  

Streptococcus agalactiae (Group B Streptococcus; GBS) is a major contributor to obstetric and neonatal bacterial sepsis. Serotype III strains cause the majority of late-onset sepsis and meningitis in babies, and thus appear to have an enhanced invasive capacity compared with the other serotypes that cause disease predominantly in immunocompromised pregnant women. We compared the serotype III and V whole genome sequences, strains NEM316 and 2603VR respectively, in an attempt to identify genetic attributes of strain NEM316 that might explain the propensity of strain NEM316 to cause late-onset disease in babies. Fourteen putative pathogenicity islands were described in the strain NEM316 whole genome sequence. Using PCR- and targeted microarray- strategies, the presence of these islands were assessed in a diverse strain collection including 18 colonizing isolates from healthy pregnant women, and 13 and 8 invasive isolates from infants with early- and late-onset sepsis, respectively.     

CHANGES IN CHEMICAL, SENSORY AND RHEOLOGICAL CHARACTERISTICS OF MANCHEGO CHEESES DURING RIPENING

Manchego cheese is a high-fat pressed ewe's-milk cheese made in Castilla-La Mancha (Spain) and produced by enzymatic coagulation. The minimum ripening time before marketing required by the Regulatory Board of the Manchego Cheese Appellation of Origin is 60 days.
This paper describes the physicochemical, proteolysis, sensory and texture characteristics of Manchego cheese, and the degree of homogeneity of cheeses made under the Manchego Appellation of Origin. The data gathered in this study indicate that sensory and instrumental analysis are useful tools for detecting changes in Manchego cheese during ripening. These changes were first detected by the instrumental analysis (2 months). The panelists detected differences after 4 months' ripening in all the factories. With physicochemical analysis, on the other hand, longer ripening times (6–8 months) are required before such changes become appreciated.     

Temporal bird community dynamics are strongly affected by landscape fragmentation in a Central American tropical forest region

Habitat loss and fragmentation are considered the main causes of species extinctions, particularly in tropical ecosystems. The objective of this work was to evaluate the temporal dynamics of tropical bird communities in landscapes with different levels of fragmentation in eastern Guatemala. We evaluated five bird community dynamic parameters for forest specialists and generalists: (1) species extinction, (2) species turnover, (3) number of colonizing species, (4) relative species richness, and (5) a homogeneity index. For each of 24 landscapes, community dynamic parameters were estimated from bird point count data, for the 1998–1999 and 2008–2009 periods, accounting for species’ detection probability. Forest specialists had higher extinction rates and a smaller number of colonizing species in landscapes with higher fragmentation, thus having lower species richness in both time periods. Alternatively, forest generalists elicited a completely different pattern, showing a curvilinear association to forest fragmentation for most parameters. Thus, greater community dynamism for forest generalists was shown in landscapes with intermediate levels of fragmentation. Our study supports general theory regarding the expected negative effects of habitat loss and fragmentation on the temporal dynamics of biotic communities, particularly for forest specialists, providing strong evidence from understudied tropical bird communities.