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.     

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.     

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.     

In search of a maize ideotype for cell wall enzymatic degradability using histological and biochemical lignin characterization

Grass cell wall degradability is conventionally related to the lignin content and to the ferulic-mediated cross-linking of lignins to polysaccharides. To better understand the variations in degradability, 22 maize inbred lines were subjected to image analyses of Fasga- and M?ule-stained stem sections and to chemical analyses of lignins and p-hydroxycinnamic acids. For the first time, the nearness of biochemical and histological estimates of lignin levels was established. Combination of histological and biochemical traits could explain 89% of the variations for cell wall degradability and define a maize ideotype for cell wall degradability. In addition to a reduced lignin level, such an ideotype would contain lignins richer in syringyl than in guaiacyl units and preferentially localized in the cortical region rather than in the pith. Such enrichment in syringyl units would favor wall degradability in grasses, contrary to dicots, and could be related to the fact that grass syringyl units are noticeably p-coumaroylated. This might affect the interaction capabilities of lignins and polysaccharides.     

Marker-assisted backcross selection in an interspecific <Emphasis Type="Italic">Cucumis</Emphasis> population broadens the genetic base of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.)

Cucumber (Cucumis sativus L.) is a major cucurbit vegetable species whose genetic base has been drastically reduced during its domestication. The crop’s narrow genetic base (3–12% DNA polymorphism) has resulted from the use of limited genetic material and intense selection during plant improvement. Recently, however, interspecific hybridization has been successful in Cucumis via mating of C. hystrix Chakr. and C. sativus, which resulted in the amphidiploid C. hytivus. We report herein a marker-assisted strategy for increasing genetic diversity in cucumber through introgression backcrossing employing C. hytivus. The comparatively late-flowering but high-yielding, indeterminate, monoecious line WI 7012A (P₁; donor parent) derived from a C. hytivus × C. sativus-derived line (long-fruited Chinese C. sativus cv. Beijingjietou) was initially crossed to the determinate, gynoecious C. sativus line WI 7023A (P₂; recurrent parent 1), and then advanced backcross generation progeny (BC₂) were crossed with the gynoecious indeterminate line WI 9-6A (P₃; recurrent parent 2). More specifically, a single F₁ individual (P₁ × P₂) was backcrossed to P₂, and then BC progeny were crossed to P₂ and P₃, where marker-assisted selection (MAS) for genetic diversity (8 mapped and 16 unmapped markers; designated Sel) or no selection (designated NSel) was applied to produce BC₃P₂ (Sel) and BC₃P₃ (Sel), and BC₂P₂ (NSel) and BC₂P₂S₁ (NSel) progeny. Relative vegetative growth, number of lateral branches (LB), days to flowering (DF), yield (fruit number), and fruit quality [as measured by length:diameter (L:D) and endocarp:total diameter (E:T) ratios] were assessed in parents and cross-progeny. DF varied from ~20 (BC₃P₂Sel) to ~25 days (BC₂P₃Sel) among the populations examined, where progeny derived from P₂ possessed the shortest DF. Differences in cumulative yield among the populations over six harvests were detected, varying from ~8 fruits per plant in BC₃P₂ (Sel) to ~39 fruits per plant in BC₂P₃ (Sel). Although the vigorous vegetative growth of line P₁ was observed in its backcross progeny, highly heterozygous and polymorphic backcross progeny derived from P₃ were comparatively more vigorous and bore many high-quality fruit. Response to selection was detected for LB, DF, L:D, and E:T, but the effectiveness of MAS depended upon the parental lines used. Data indicate that the genetic diversity of commercial cucumber can be increased by introgression of the C. hystrix genome through backcrossing.     

Chiral amplification of oligopeptides in two-dimensional crystalline self-assemblies on water

Differences in the two-dimensional packing arrangements of racemic and enantiomeric crystalline self-assemblies on the water surface of amphiphilic activated analogs of lysine and glutamic acid have been used to prepare oligopeptides of homochiral sequence and oligopeptides of single handedness from chiral nonracemic mixtures. The crystalline structures on the water surface were determined by grazing incidence x-ray diffraction and the diastereomeric composition of the oligopeptides by matrix-assisted laser desorption time-of-flight mass spectrometry with enantio-labeling. These results suggest that reactivity of ordered clusters at interfaces might have played a role in the generation of early homochiral biopolymers.     

Detection of GTP-tubulin conformation in vivo reveals a role for GTP remnants in microtubule rescues

Microtubules display dynamic instability, with alternating phases of growth and shrinkage separated by catastrophe and rescue events. The guanosine triphosphate (GTP) cap at the growing end of microtubules, whose presence is essential to prevent microtubule catastrophes in vitro, has been difficult to observe in vivo. We selected a recombinant antibody that specifically recognizes GTP-bound tubulin in microtubules and found that GTP-tubulin was indeed present at the plus end of growing microtubules. Unexpectedly, GTP-tubulin remnants were also present in older parts of microtubules, which suggests that GTP hydrolysis is sometimes incomplete during polymerization. Observations in living cells suggested that these GTP remnants may be responsible for the rescue events in which microtubules recover from catastrophe.     

Comparison of the pig and feline models for full thickness corneal transplantation

Purpose The goal of this study was to report on the advantages and limitations of the pig and feline models for experimental in vivo corneal transplantation. Methods Ten healthy domestic pigs and ten healthy cats were used. Full thickness penetrating keratoplasty was performed using autologous (eight cases), allogeneic (seven cases) or human xenogeneic (three cases) tissue. In two other cases, the inflammatory response to partial thickness trephination (without transplantation) was evaluated. Eyes were assessed daily before and after surgery by slit‐lamp, pachymetry, and tonometry. A transparency score ranging from 0 (opaque graft) to 4 (clear graft) was used, based on the slit‐lamp examination. Optical coherence tomography, histology, and electron microscopy were performed postmortem. Results In the pig, the mean (±SD) transparency score for the eight full thickness grafts was 0.88 ± 0.99, ranging from 0 to 3. In the feline model, the mean transparency score for the seven uncomplicated grafts was 3.93 ± 0.19, ranging from 3.5 to 4. Both negative controls without endothelium remained opaque at all time. Intraoperative tendency for iris incarceration into the wound, rapid corneal swelling, suture cheese wiring, and postoperative intraocular inflammation were the main factors jeopardizing the functional success of the corneal transplant in the pig model. Conclusion Suboptimal functional results were obtained after full thickness corneal transplantation in the pig model, while in the feline model, the same protocol yielded uneventful surgeries and clear transplants, with functional results similar to those achieved in human subjects.     

Changes in physicochemical characteristics and volatile constituents of strawberry (Cv. Cigaline) during maturation

Changes in the volatile composition of strawberries (cv. Cigaline) at six stages of maturity, from 28 to 44 days after anthesis, were investigated over two harvesting seasons. Volatiles were isolated by direct solvent extraction and analyzed by means of GC-FID and GC-MS, with special attention to the quantification of furanones. Firmness, skin color, soluble solids (SS), titratable acidity (TA), SS/TA ratio, organic acids, and sugars were also determined. With increasing maturity, soluble solids, SS/TA ratio, Minolta a value, and levels of sucrose, glucose, fructose, and malic acid increased, whereas Minolta L value, hue angle (), titratable acidity, and levels of citric acid decreased. Furanones and esters were generally not detected before half-red fruits, whereas C(6) compounds were the main compounds in immature fruits. During maturation, levels of these so-called green components decreased drastically, whereas levels of key flavor compounds increased significantly and were closely correlated with skin color development. Maximum volatile production was observed in fully red fruits.