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Actin as a candidate quality marker for food of animal origin
Full text linkMost of the relevant meat and meat-product quality characteristics are the results of the chemistry of protein and peptides. Therefore, the inclusion of information on protein differences provided by protein markers can make a significant contribution to the improvement of meat and meat product quality.
Actins are a family of highly conserved proteins, which play fundamental roles in nearly all aspects of eukaryotic cell biology. In the skeletal muscle, in addition to the highly specialized contractile apparatus, there are both the actin-associated costameric complexes and the functionally distinct cytoskeletal actin-based filaments.
Ante mortem muscle biochemistry strongly influences post mortem biochemical processes which, in turn, are linked to final quality attributes, including texture which is one of the most important attributes of muscle foods. However, there is very little knowledge on the way in which ante mortem biochemistry changes the post mortem events and hence the resulting final quality. The understanding of post mortem mechanisms is essential for predicting the final quality in terms of texture.
The histochemical and biochemical evidence indicates that much of the tenderization associated with post mortem aging is due to the action of the enzymes, which are known to be endogenous to the muscle. Interestingly, the most abundant proteins of the myofibril, actin and myosin, are not significantly degraded during post mortem aging. However, an extensive apoptosis could lead to a progressive degradation of cytoskeletal and thin filaments of actin, resulting to meat tenderization.
The investigation on how actin degradation affects meat and meat product quality is still nascent, but the results reported in this PhD thesis seem promising. Indeed, the main activities have been directed to evaluate the potential use of actin as a biochemical marker for the prediction of muscle food quality in three Italian PDO dry-cured hams and in farmed sea bass.
In the first part of this thesis, a brief general introduction on the muscle composition in mammals and fish and on the post mortem events occurring in muscle is reported, followed by a description of the characteristics of dry-cured hams and sea bass like food products of animal origin. Therefore, the two papers related to the above reported topics are attached, accompanied by some conclusive remark
The caspase and calpain proteolytic systems in Longissimus dorsi and Infraspinatus muscles of Italian Simmental young bulls
No full textCalpains and capsases are two families of cytosolic proteases essential for a proper skeletal muscle function, which recognize specific target proteins for degradation. Moreover, μ-calpain is believed to play a major role in post mortem proteolysis and meat tenderization, which in turn depends on fibre type composition. Recent data also support the involvement of caspases in the development of tender meat. In fact, it is plausible that the hypoxic conditions occurring in post mortem may activate these proteases, which function as vital executioners of apoptosis in hypoxia/ischemia and degrade structural components of the cytosckeleton. The goal of this work was to evaluate the activities of μ-calpain and caspases in two different muscle types from bulls, immediately after slaughtering, by immunodetection of their specific proteolytic products and to compare such activities to their related mRNA expression level. In particular, caspases 9 and 3 have been analysed, which are an initiating and an executer caspase, respectively, to follow the entire cascade of events occurring during a hypoxic stress.
Samples of Longissimus dorsi (white/type IIB muscle) and Infraspinatus (red/type I muscle) muscles were collected within 20 minutes from slaughtering of 16 Italian Simmental young bulls, and stored at -80° until the analysis. By SDS-PAGE the alpha II spectrin and its degradation products 145kDa (from μ-calpain degradation) and 150kDda and 120kDda (from caspases degradation) were separated and then quantified in relative terms. Total RNA was extracted from the two muscles and cDNA was produced; the DNA was amplified by q-PCR technic. The genes analyzed were CAPN1 (coding for μ-calpain), CASP3 (caspase 3), CASP9 (caspase 9). Genes coding for GAPDH, β-Actin, RPLP0 and Cyclophilin was used as reference genes.
Both caspases and μ-calpain were found active, having been recognized their target degradation products. In particular no difference in the level of alpha II spectrin fragment, derived from the caspase-3 activity, was found between the Longissimus dorsi and Infraspinatus muscles, in agreement with gene expression results. On the other hand, the μ-calpain activity was influenced by the type of muscles
Effects of ozone processing on chemical, structural and functional properties of whey protein isolate
No full textHigh concentration of gaseous ozone was used to treat whey protein isolate (WPI) powder for different times ranging from 30 to 480. min. The aim of the present work was to study the changes in protein structure and evaluate their consequences on selected functional properties. Surface hydrophobicity, free sulphhydryl groups, turbidity, FTIR, SDS-PAGE, HPLC analysis are performed to evaluate the chemical and structural effects of ozone. The effect of ozonation on the solubility and the foaming properties of proteins are also determined. Results show a reduction of free sulphhydryl groups and an increase of surface hydrophobicity, indicating a self-rearrangement in the protein structure following ozonation. Thus, ozonation allows creation of a more flexible structure without formation of a strong network of disulphide bond or aggregations, which is corroborated by the turbidity analysis and SDS-PAGE. Ozone processing induces modifications that improve the foaming capacity and foam stability, however, a slight reduction in the solubility is encountere
Proteolytic resistance of actin but not of myosin heavy chain during processing of Italian PDO (protected designation of origin) dry-cured hams
No full textProteomics is the approach of choice to study the fate of specific proteins, and it is very useful in identifying quality molecular markers. A combination of immunochemical and mass spectrometry analysis was used to assess the occurrence of proteolytic changes of actin and myosin heavy chain (MHC) proteins in pig biceps femoris skeletal muscle during processing of three Italian PDO drycured hams. Early post-mortem muscle displayed low levels of actin and myosin fragments. In spite of a high proteolysis index and the presence of active cathepsin D until the final ripening phase, during dry-cured ham processing, very low actin proteolysis and no generation of fragments from α-skeletal muscle isoform were found, while the identified fragments derived mainly from the cardiac actin isoform. On the other hand, MHC showed a remarkable degradation of its catalytic head, generating a C-terminal 135-kDa fragment.
Based on its ability to interact with actin in vitro, this MHC fragment might have a role in stabilisation of actin.
In conclusion, these results suggest that maintenance of skeletal muscle α-actin could reflect limited dismantling of the sarcomeric structure and be a useful marker to monitor the events that result in the typical texture of dry-cured ham
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Proteolisi dell’actina nel biceps femoris durante la produzione del prosciutto di San Daniele
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