HPTLC screening of taro hybrids (Colocasia esculenta (L.) Schott) with high flavonoids and antioxidants contents

Taro (Colocasia esculenta) is the tropical root crop species featuring the greatest flavonoids diversity. Their quantification is important for breeding programmes focusing on biofortification. This study aims at developing an HPTLC protocol to compare the flavonoids fingerprints of more than 1800 hybrids belonging to 24 full‐sib families and to select genotypes with high levels of antioxidants. Twenty different chemical markers were identified based on bands R_f and colour. Flavonoids differ among individuals both quantitatively and qualitatively. Marker ‘A’ yielded the strongest antioxidant response to DPPH, equivalent to the one with quercetin pure standard. Overall, 377 high flavonoids content (HFC) hybrids were selected from 14 different families. The mean corm weight of HFC hybrids always appeared higher than the mean corm weight of the family they belong to. This method allows unambiguous selection of HFC hybrids. It also contributes to taro genetic improvement for nutritional value and access to new markets and to strengthen corm tolerance to pests and diseases. It could be applied to other tropical root crop species.     

Chemical communication in Ceratophysella sigillata (Collembola: Hypogastruridae): intraspecific reaction to alarm substances

When disturbed or damaged, the winter-active collembolan Ceratophysella sigillata releases a strong aromatic odour, which can be perceived even by humans. The efficiency of the substances released as an intraspecific alarm substance was investigated. C. sigillata showed distinct reactions to chemicals released by conspecifics; crushed conspecifics, cuticle washings (with pentane) and whole body extracts (with methyl acetate) were tested. Our results demonstrate that a very sensitive intraspecific avoidance reaction is present to the substances released by crushed C. sigillata as well as to washings and extracts: extracts from as little as half a springtail induced a significant avoidance reaction in conspecifics. Alarm substances were present in all instars of C. sigillata including eggs, and all instars of C. sigillata tested showed similar reactions to the extracts or crushed conspecifics.     

Composition rather than viscosity modifies the aroma compound retention of flavored stirred yogurt

The influence of thickening agents (modified starch/pectin mixture 0 and 7 g/L) and mechanical treatment (low, medium, and high) on the retention of esters (pentyl acetate and ethyl pentanoate), aldehydes (hexanal and (E)-2-hexenal), and a lactone (gamma-octalactone) in low-fat flavored stirred yogurts were investigated under equilibrium conditions. In the range studied, the thickening agent and mechanical treatment had little influence on aroma compound retention compared to the decreasing effect of increasing dairy protein concentration on aldehyde retention and the "salting out" effect of carbohydrates on esters. Moreover, experiments in dynamic mode (study of the release of hexanal when yogurts were heated) showed, in the conditions studied, that heat and mass transfer coefficients were not influenced by any of the studied factors (thickening agents and mechanical treatment). These results under static and dynamic conditions are not related to the significant decreasing effect of thickening agents on apple sensory scores associated with hexanal, observed in a previous sensory study. Thus, this sensory effect of thickening agents may be due to sensory interactions between perceptions rather than physicochemical interactions.     

Oxidative stability of bovine serum albumin- and sodium caseinate-stabilized emulsions depends on metal availability

Proteins often stabilize food emulsions and are also able to promote or delay lipid oxidation in complex systems. The purpose of this work was to investigate the relationship between metal ion availability and oxidative stability of oil-in-water emulsions stabilized by bovine serum albumin (BSA) or sodium caseinate (NaCas). Emulsions with similar and stable droplet size distributions were prepared with stripped sunflower oil (30 vol %) and protein solutions (20 g L(-)(1); pH = 6.5). In the absence of the water-soluble metal chelator EDTA, oxygen uptake, conjugated dienes, and volatile compounds developed faster in NaCas-stabilized emulsions than in those prepared with BSA. This effect is attributed to the chelating properties of NaCas and to electrostatic interactions that attract some metal ions at the interface where they could initiate lipid oxidation. When EDTA (100 muM) was present, oxidation was delayed to a greater extent in emulsions made with NaCas than in BSA stabilized emulsions. These conditions probably enabled NaCas to exert free-radical-scavenging activity.     

Polyphenols from Honeybush tea (Cyclopia intermedia)

The fermented leaves and stems of Cyclopia intermedia are used to brew Honeybush tea, a herbal tea indigenous to South Africa. The plant is also used to manufacture a sweet herbal infusion used for restorative properties such as soothing coughs and alleviating bronchial complaints including tuberculosis, pneumonia, and catarrh. It is claimed to have a low tannin content and no caffeine and contains various antioxidants. Continued investigations into the phenolic content of the leaves and stems of C. intermedia yielded tyrosol and a methoxy analogue, 2-[4-[O-alpha-apiofuranosyl-(1' '-->6')-beta-d-glucopyranosyloxy]phenyl]ethanol, 4-[O-alpha-apiofuranosyl-(1' '-->2')-beta-d-glucopyranosyloxy]benzaldehyde, five glycosylated flavonols, two isoflavones, four flavanones, two isoflavones, and two flavones. Structure elucidation was done by NMR, CD, and MS methods. Because flavonoids are presumed to contribute significantly toward the scavenging effects of active oxygen species, our results indicate that the tentative claimed health-promoting properties may be attributed to the presence of these and other phenolics in C. intermedia.     

Acrylamide formation from asparagine under low moisture Maillard reaction conditions. 2. Crystalline vs amorphous model systems

The formation of acrylamide was investigated in model systems based on asparagine and glucose under low moisture Maillard reaction conditions as a function of reaction temperature, time, physical state, water activity, and glass transition temperature. Equimolar amorphous glucose/asparagine systems with different water activities were prepared by freeze drying and were shown to quickly move to the rubbery state already at room temperature and a water activity of above 0.15. The acrylamide amounts were correlated with physical changes occurring during the reaction. Pyrolysis and kinetics of acrylamide release in amorphous and crystalline glucose/asparagine models indicated the importance of the physical state in acrylamide formation. In amorphous systems, acrylamide was generated in higher concentrations and at lower temperatures as compared to the crystalline samples. Time and temperature are covariant parameters in both systems affecting the acrylamide formation by thermal processes. On the other side, the water activity and glass transition temperature do not seem to be critical parameters for acrylamide formation in the systems studied.     

The relative importance of dispersal limitation and habitat preference in shaping spatial distribution of saplings in a tropical moist forest: a case study along a combination of hydromorphic and canopy disturbance gradients

• Introduction   

Various processes contribute to shaping the local assemblage of species in hyperdiverse tropical forest. The relative contribution of environmental factors and dispersal limitation in determining the spatial distribution of saplings at local scale is unclear.     

Pathways and dynamics of NO3 and NH4 applied in a mountain Picea abies forest and in a nearby meadow in central Switzerland

To evaluate the pathways and dynamics of inorganic nitrogen (N) deposition in previously N-limited ecosystems, field additions of ¹⁵N tracers were conducted in two mountain ecosystems, a forest dominated by Norway spruce (Picea abies) and a nearby meadow, at the Alptal research site in central Switzerland. This site is moderately impacted by N from agricultural and combustion sources, with a bulk atmospheric deposition of 12 kg N ha⁻¹ y⁻¹ equally divided between NH₄⁺ and NO₃⁻. Pulses of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ were applied separately as tracers on plots of 2.25 m². Several ecosystem pools were sampled at short to longer-term intervals (from a few hours to 1 year), above and belowground biomass (excluding trees), litter layer, soil LF horizon (approx. 5-0 cm), A horizon (approx. 0-5 cm) and gleyic B horizon (5-20 cm). Furthermore, extractable inorganic N, and microbial N pools were analysed in the LF and A horizons. Tracer recovery patterns were quite similar in both ecosystems, with most of the tracer retained in the soil pool. At the short-term (up to 1 week), up to 16% of both tracers remained extractable or entered the microbial biomass. However, up to 30% of the added ¹⁵NO₃⁻ was immobilised just after 1 h, and probably chemically bound to soil organic matter. 16% of the NH₄⁺ tracer was also immobilised within hours, but it is not clear how much was bound to soil organic matter or fixed between layers of illite-type clay. While the extractable and microbial pools lost ¹⁵N over time, a long-term increase in ¹⁵N was measured in the roots. Otherwise, differences in recovery a few hours after labelling and 1 year later were surprisingly small. Overall, more NO₃⁻ tracer than NH₄⁺ tracer was recovered in the soil. This was due to a strong aboveground uptake of the deposited NH₄⁺ by the ground vegetation, especially by mosses.     

Determination of the conjugated linoleic acids in cow's milk fat by Fourier transform Raman spectroscopy

The collective term "conjugated linoleic acid" or "CLA" generally refers to a mixture of conjugated positional and geometric isomers of linoleic (cis-9,cis-12-octodecadienoic) acid. In nature, these isomers are mainly formed in the rumen by biohydrogenation of polyunsaturated fatty acids. This study concerns a first trial of CLA determination in cow's milk fat by Raman spectroscopy. The spectra of pure cis-9-oleic, cis-9,cis-12-linoleic, cis-9,trans-11-linoleic, and trans-10,cis-12-linoleic acids have been examined in comparison with the spectra of selected milk-fat samples containing between 0 and 3% of CLA. The trial of CLA determination by Raman spectroscopy on cow milk fat has reached its objective with the two following results. First, the examination of the Raman spectra allows to identify three specific Raman signals of the chemical bonds associated to the cis,trans conjugated C=C in the rumenic and trans-10,cis-12-octodecadienoic acids at 1652, 1438, and 3006 cm(-1). Second, the calibration of Raman spectrometer for the CLA determination has indicated that these three specific signals suit very well for the accurate and reliable measurement of CLA concentration in milk fat. To our knowledge, the present study is the first successful attempt to determine the CLA content of milk fat by a spectrophotometric method.