Textural properties and their correlation to cell structure in porous food materials

This paper focuses on understanding the role of structural parameters and starch crystallization on the toughness of cake samples. Accurate mechanical measurements were performed to obtain toughness values, and these were related to structural parameters obtained from image analyses. Three-dimensional skeletons of food samples were generated by using X-ray tomography technique. The structural parameters (cell diameter, cell wall thickness, thickness to radius ratio (t/R), fragmentation index) were obtained after processing of the images with CTan software. The basic hypothesis of the paper is to show that the structural parameter t/R is a determinant for predicting toughness, which is a critical indicator of freshness. Freshness in cakes and other baked products is a leading factor in consumer perception. For this purpose three different cake formulations were stored at 37 and 50 °C. Cycling from these temperatures to lower storage temperatures of 25 and 4 °C was done to accelerate the starch retrogradation rate. Experimental results indicated that there was a strong interrelationship between morphological structure and the mechanical properties with regression coefficients of 0.68 and 0.95. Starch retrogradation, which was followed by X-ray diffractometry, was found to be directly proportional to toughness values, where the percent relative crystallinity increased with storage temperature.     

Effects of leaf age and tree size on stomatal and mesophyll limitations to photosynthesis in mountain beech (Nothofagus solandrii var. cliffortiodes)

Mesophyll conductance, g(m), was estimated from measurements of stomatal conductance to carbon dioxide transfer, g(s), photosynthesis, A, and chlorophyll fluorescence for Year 0 (current-year) and Year 1 (1-year-old) fully sunlit leaves from short (2 m tall, 10-year-old) and tall (15 m tall, 120-year-old) Nothofagus solandrii var. cliffortiodes trees growing in adjacent stands. Rates of photosynthesis at saturating irradiance and ambient CO(2) partial pressure, A(satQ), were 25% lower and maximum rates of carboxylation, V(cmax), were 44% lower in Year 1 leaves compared with Year 0 leaves across both tree sizes. Although g(s) and g(m) were not significantly different between Year 0 and Year 1 leaves and g(s) was not significantly different between tree heights, g(m) was significantly (19%) lower for leaves on tall trees compared with leaves on short trees. Overall, V(cmax) was 60% higher when expressed on the basis of CO(2) partial pressure at the chloroplasts, C(c), compared with V(cmax) on the basis of intercellular CO(2) partial pressure, C(i), but this varied with leaf age and tree size. To interpret the relative stomatal and mesophyll limitations to photosynthesis, we used a model of carbon isotopic composition for whole leaves incorporating g(m) effects to generate a surface of 'operating values' of A over the growing season for all leaf classes. Our analysis showed that A was slightly higher for leaves on short compared with tall trees, but lower g(m) apparently reduced actual A substantially compared with A(satQ). Our findings showed that lower rates of photosynthesis in Year 1 leaves compared with Year 0 leaves were attributable more to increased biochemical limitation to photosynthesis in Year 1 leaves than differences in g(m). However, lower A in leaves on tall trees compared with those on short trees could be attributed in part to lower g(m) and higher stomatal, L(s), and mesophyll, L(m), limitations to photosynthesis, consistent with steeper hydraulic gradients in tall trees.     

A Lateral Surgical Approach to the Equine Femoropatellar Joint

A surgical approach to the lateral trochlear ridge of the distal femur of the horse was developed to facilitate evaluation and curettage of osteochondral defects of the lateral trochlear ridge. Surgical exploration of the lateral trochlear ridge was achieved in 11 patients with osteochondral defects of the lateral trochlear ridge using a craniolateral arthrotomy between the middle and lateral patellar ligaments. The technique described allowed adequate exposure for evaluation, removal of loose osteochondral fragments, and curettage of cartilage abnormalities on the lateral trochlear ridge.     

Comparison of management techniques for evaluating Italian and hybrid ryegrass cultivars

The effect of management on dry matter yield and persistence of eight cultivars was assessed over a 3-year period (1978–80) under integration of sheep grazing and simulated sheep grazing with cutting for conservation, and the two cutting frequencies used in the National List trials. A high correlation was obtained in the first and second harvest years between managements in respect of annual production, the ranking order of yield being similar for the range of cultivars. In the third harvest year yield correlation and persistence between sheep grazing and simulated sheep grazing was high and similar to previous years, but all other yield and persistence correlations were considerably reduced. A major effect of frequent cutting management used in the National List trials was the increase in the proportion of unsown grasses (mainly Poa spp.) in the swards.     

Breeding for Highly Fertile Isolates of Nectria haematococca MPVI that are Highly Virulent on Pea and In Planta Selection for Virulent Recombinants

ABSTRACT The heterothallic ascomycete Nectria haematococca mating population VI (anamorph Fusarium solani) is a broad host range pathogen. Field isolates of this fungus that are pathogenic on pea tend to be female sterile, of low fertility, and the same mating type (MAT-1), whereas female fertile isolates of either mating type that are highly fertile tend to be nonpathogenic on this plant. To facilitate genetic analysis of traits that may be important in the ability of N. haematococca to parasitize peas, a breeding project was undertaken to produce hermaphroditic isolates of each mating type that are highly fertile and highly virulent on peas. Although the association of high virulence on peas with female sterility and the MAT-1 mating type was not completely broken, isolates with high fertility and high virulence on peas were bred within two generations. Highly virulent progeny were also isolated by an alternative method in which pea plants were inoculated with a mixture of ascospores from a cross between two moderately virulent parents. Whereas all ascospores isolated without selection in planta had lower virulence than the parents, many isolates recovered from diseased tissue were more virulent than the parental isolates. Some of the recovered isolates were shown by restriction fragment length polymorphism analysis to be genetic recombinants of the parents, demonstrating that the pea tissue selected virulent recombinants. All highly virulent isolates tested had the ability to detoxify the pea phytoalexin pisatin, again showing a link between this trait and pathogenicity on the pea.     

Presettlement and modern disturbance regimes in coast redwood forests: Implications for the conservation of old-growth stands

Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.     

Current and historical inputs of mercury to high-latitude lakes in Canada and to Hudson Bay

Sediment cores collected from several lakes in northern Canada have been analyzed for mercury and several other chemical contaminants. Sites ranged from the Experimental Lakes Area of northwestern Ontario, north to Cornwallis Island, and west to the southern Yukon. Cores were sliced at sites of collection and individual slices were freeze dried and analyzed for Pb-210 and Cs-137 to estimate average time intervals of deposition. The earliest date estimated by Pb-210 was about 1850, and mercury concentrations in some lakes were clearly increasing before then, assuming no vertical movements of mercury within the sediments. Extrapolation of dates downward to deeper slices, assuming a constant sedimentation rate, indicated that in some lakes mercury inputs increased slowly even in the 1500's, more rapidly after 1750, and more rapidly yet over the current century. These increases are interpreted as increased fluxes of mercury to the lakes as a result of long-range transport of atmospheric mercury, since there are no local industrial sources of mercury. Slices taken near the bottom of a core are taken to estimate the geological component while elevations in excess of that in surface slices are taken to represent contamination from fallout. This partitioning suggests that sediments in the eastern Northwest Territories are dominated by pollution, while those from the western Northwest Territories are influenced more by their geological settings. Two cores from Hudson Bay suggest that mercury is increasing there too, but has not yet exceeded geological sources. Mercury shows little or no tendency to decline in the most recent slices; indicating that inputs of mercury remain at or near their historical maxima. Given relatively high and continuing inputs of mercury to northern lakes it seems likely that some portion of that mercury may find its way into the food chain, hence the long-term prospect is for increasing levels of mercury in northern fish.     

Wheat gluten used as a clarifying agent of red wines.

Bovine spongiform encephalopathy caused a situation of crisis leading the public and winemakers to lose their confidence in the use of gelatin as a fining agent and to reject animal proteins in general. Therefore, we started the search for a substitute for gelatin and egg protein by comparing gluten with these fining treatments currently used. This study concerned the fining of a Burgundy red wine (Rully, Controlled Appellation). For 6 g/hL, enzymatically hydrolyzed glutens (EHG) gave better efficiencies than deamidated glutens. The efficiency of the egg proteins treatment was situated between those of the hydrolyzed glutens and deamidated glutens. For 12 and 18 g/hL, turbidities of the wine treated by five glutens were 67 to 86% less than that of the control wine. Better results were obtained with egg proteins for short kinetics particularly. Wine fining with gluten was always better than gelatin treatments. The differences between the five glutens became very small when the dose incorporated in the wine increased. The volumes of lees generated by fining with gluten are situated between the values obtained with egg proteins and gelatin. After fining, immunodetection with gluten polyclonal antibodies failed to detect residual deamidated gluten.