The processing of surimi products requires the addition of high levels of salt, which makes it a high-salt food that poses a risk to human health. The search for exogenous additives to reduce the salt content of surimi products while ensuring their quality characteristics is crucial. Therefore, the effect of different species of cellulose on enhancing the quality characteristics of low-salt surimi gels was investigated and the best-modified cellulose was identified. Carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose (HPMC), and microcrystalline cellulose (MCC) were selected for this study to compare with high-salt control and low-salt control. The results showed that cellulose could induce conformational transitions of proteins and promote the formation of an ordered and dense surimi gel network and the minimum porosity of 15.935% was obtained in the MCC-treated group. The cellulose-treated group conferred good textural properties to the surimi gels, significantly improved gel strength and water retention capacity (<i>p</i> < 0.05), and reduced the amount of water lost after cooking treatment (<i>p</i> < 0.05). Low-field NMR results showed that cellulose reduced the release of water, converting more free water to immobile water, thus increasing the water proton density. The higher energy storage modulus G' in the presence of cellulose indicated a more stable surimi gel system dominated by springiness. In summary, cellulose could confer better quality characteristics to low-salt surimi gels and MCC performance was superior to other cellulose species. This study helps the understanding of the mechanism of cellulose-surimi action on the development of high-quality low-salt surimi gels.
Selective sweeps of variation caused by fixation of major genes may have a dramatic impact on the genetic gain from background polygenic variation, particularly in the genome regions closely linked to the major gene. The response to selection can be restrained because of the reduced selection intensity and the reduced effective population size caused by the increase in frequency of the major gene. In the context of a selected population where fixation of a known major gene is desired, the question arises as to which is the optimal path of increase in frequency of the gene so that the selective sweep of variation resulting from its fixation is minimized. Using basic theoretical arguments we propose a frequency path that maximizes simultaneously the effective population size applicable to the selected background and the selection intensity on the polygenic variation by minimizing the average squared selection intensity on the major gene over generations up to a given fixation time. We also propose the use of mating between carriers and non-carriers of the major gene, in order to promote the effective recombination between the major gene and its linked polygenic background. Using a locus-based computer simulation assuming different degrees of linkage, we show that the path proposed is more effective than a similar path recently published, and that the combination of the selection and mating methods provides an efficient way to palliate the negative effects of a selective sweep.
Flavor sensations in food are highly influenced by the aroma and taste compounds. Reviewing the extensive literature of recent years in this field has shown that the reconstitution of flavor based on aroma and taste compounds poses numerous problems. These are of different nature and include among others (a) chemical transformations among these compounds, (b) changes in the concentrations of the compounds responsible for the perceived flavor, (c) interactions among the chemical compounds that enhance or reduce a specific flavor sensation, and finally, (d) the complexity of the different food matrices and its influence in the flavor perception. Another difficulty that flavor scientists must face is how to properly model and visualize the complex relationships existing between the chemical composition of foods and the flavor perception. These problems have repercussions on the reconstitution of the flavor signature of food based on the natural concentrations of its key aroma and taste compounds. Therefore, the main aim of this review is to deal with all these issues to propose potential solutions for a robust transformation in a science-based quality approach.
Tea (Camellia sinensis) has a long history of medicinal use in the world. The chemical components of tea mainly consist of polyphenols (TPP), proteins, polysaccharides (TPS), chlorophyll, alkaloids, and so on. Great advances have been made in chemical and bioactive studies of catechins and TPP from tea in recent decades. However, the TPS from tea materials have received much less consideration than that of TPP. The number of relevant publications on the TPS from tea leaves and flowers has increased rapidly in recent years. This mini-review summarizes the structure-function relationship of TPS from tea leaves and flowers. The application of purified TPS from tea material as functional or nutritional foods was still little. It will help to develop the function foods with tea TPS and better understand the structure-bioactivity relationship of tea TPS.
Parallel speciation can occur when traits determining reproductive isolation evolve independently in different populations that experience a similar range of environments. However, a common problem in studies of parallel evolution is to distinguish this hypothesis from an alternative one in which different ecotypes arose only once in allopatry and now share a sympatric scenario with substantial gene flow between them. Here we show that the combination of a phylogenetic approach with life-history data is able to disentangle both hypotheses in the case of the intertidal marine snail Littorina saxatilis on the rocky shores of Galicia in northwestern Spain. In this system, numerous phenotypic and genetic differences have evolved between two sympatric ecotypes spanning a sharp ecological gradient, and as aside effect of the former have produced partial reproductive isolation. A mitochondrial phylogeny of these populations strongly suggests that the two sympatric ecotypes have originated independently several times. Building upon earlier work demonstrating size-based assortative mating as the main contributor to reproductive isolation among ecotypes, our analysis provides strong evidence that divergent selection across a sharp ecological gradient promoted the parallel divergence of body size and shape between two sympatric ecotypes. Thus, divergent selection occurring independently in different populations has produced the marine equivalent of host races, which may represent the first step in speciation.
Summary 1. Genetic variation at five microsatellite loci was investigated in six sea trout ( Salmo trutta ) populations to describe their spatio‐temporal genetic variation in north‐western Spain. We observed significant genetic variation between river basins, and isolation by distance with restricted gene flow between neighbouring rivers, which suggests an important homing behaviour. 2. Despite these populations suffering a serious demographic decline during 1998, we did not detect any reduction in their genetic variation, suggesting a reasonably high effective population size and temporal stability. 3. Genetic differences among rivers should be taken into account in future management activities. Given the high genetic variability and the temporal stability observed, we believe that no supportive breeding programmes are presently needed in these populations.
This ICES Techniques in Marine Environmental Sciences describes a sediment elutriate bioassay using embryos of the sea urchin Paracentrotus lividus, a species widely distributed in both Atlantic and European Mediterranean waters. The proposed method is directly applicable to other echinoid species used in ecotoxicology worldwide, such as the Strongylocentrotus and Arbacia genus. The bioassay endpoint is a quantitative, observer‐independent, automatically readable response. Statistical methods and assessment criteria to classify sediment samples according to their biological quality status are also included, consistent with the demands of the European Water Framework Directive.
