The apoptosis of grass carp (Ctenopharyngodon idella) muscle during postmortem condition regulated by the cytokines via TOR and NF-κB signaling pathways.

Postmortem alteration by apoptosis has significant effects on flesh quality. Currently, the information necessary to understand the apoptotic behavior and the molecular mechanisms during postmortem alteration in fish muscle is still lacking. Activation of apoptosis and the cytokines involved in regulating apoptosis in fish muscle were evaluated during postmortem condition at 4 °C for 5 days in terms of apoptotic morphology changes, nucleus DNA fragmentation, caspases activation and related gene expressions. The triggering apoptotic mechanisms associated with multiple cytokines transcriptional levels showed that the up-regulated pro-apoptotic mediators [IFN-γ2, TNF-α, IL-6, IL-1ß, IL-17D, IL-12p35 and IL-10 (except IL-15)] and the down-regulated anti-apoptotic mediators of [IL-8 and IL-11 (except TGF-ß and IL-4)] both regulated apoptosis at early stage, which were regulated by NF-κB and TOR, respectively. Results suggested that transcriptional regulation of multiple cytokines produce a positive outcome on triggering apoptosis.

Preparation of High-Quality Fermented Fish Product.

This protocol provides a method for preparation of industrialized fermented fish product with sturgeon (Aquilaria sinensis) meat product. The procedures were: (1) pretreatment of farmed sturgeon including decapitation, evisceration, skinning-off, cleaning and cutting; (2) marinating fish cubes in 6-12% (w/v) salt solution (1:1, fish cube mass to solution volume); (3) drying fish cubes to a water content of 50-60% by hot air (40-60 °C) or by vacuum; (4) fermentation involving inoculating fish cubes with 0.4-1.6% (w/w) S. cerevisiae in flavor solution to fish cubes and fermenting at 25-35 °C for 6-10 h; (5) sealing fish cubes in vacuum packages with marinating and fermenting solutions; (6) sterilizing at 115-121 °C for 10-20 min. The sturgeon meat product prepared by this method has delicious taste which is mellow and thick, has various types and large amounts of volatile flavor compounds such as alcohols and esters which could mask musty and unpleasant odor from fish, has moderate salt content but good texture properties such as high springiness, gumminess and chewiness, and has bright russet color and attractive appearance. This new technique could also be applied in the processing of other fish to provide convenient fish snack foods which could be stored at room temperature. It is appropriate for both marine and freshwater fish.

A comparison of endogenous and microbial proteolytic activities during fast fermentation of silver carp inoculated with Lactobacillus plantarum.

The study was aimed to investigate different roles of endogenous and Lactobacillus plantarum proteases during fast fermentation of silver carp. The results show that endogenous proteases could degrade both sarcoplasmic and myofibrillar proteins. In contrast, L. plantarum had low proteinase activities and could only hydrolyze sarcoplasmic peptides. This indicates that gel properties could be mainly affected by endogenous proteolysis while microbial proteolysis contributed to the production of smaller peptides and free amino acids which may be related to flavor and taste. Texture and free amino acid analyses verified these hypotheses. It shows that endogenous lysosomal proteases were the major contributors for the decrease of gel strength while L. plantarum proteolytic activities could lead to the increase of aspartic acid, glutamic acid, and alanine, which may result in umami and sweet taste; and also lead to a rise in some amino acids which were volatile compounds precursors.

Effects of pure starter cultures on physico-chemical and sensory quality of dry fermented Chinese-style sausage.

Dry fermented Chinese-style sausages prepared in laboratory inoculating with Lactobacillus casei subsp. casei-1.001, Pediococcus pentosaceus-ATCC 33316, Staphylococcus xylosus-12 and without starter culture randomly sampled at 0, 3, 10, and 24 days of ripening were analyzed for physico-chemical and sensory qualities. A significant (p<0.05) decrease in moisture content of sausage during ripening was observed, whereas other major chemical parameters remained unchanged. The microbial fermentation resulted in decreased pH and nitrite but increased non protein nitrogen and total volatile basic nitrogen in the products. Starter cultures except P. Pentosaceous-ATCC 33316, used in the sausage failed to suppress rancidity in ripened product as indicated by a significant (p<0.05) rise in thiobarbituric acid. The lightness (L) and yellowness (b) in the colour of all sausages decreased with ripening time, meanwhile the redness (a) increased significantly (p<0.05) in sausages inoculated with cultures L. casei subsp. casei-1.001 and S. xylosus-12. The texture profile of sausages was almost similar except for P. Pentosaceous-ATCC 33316, which showed significantly (p<0.05) lower hardness and gumminess. Based on the sensory and physico-chemical quality criteria, S. xylosus-12 could be used as a starter culture to produce dry fermented Chinese-style sausage of high quality.

Enzymatic preparation of chitooligosaccharides by commercial lipase.

The effect of a commercial lipase on chitosan degradation was investigated. When four chitosans with various degrees of deacetylation were used as substrates, the lipase showed higher optimal pH toward chitosan with higher DD (degree of deacetylation). The optimal temperature of the lipase was 55°C for all chitosans. The enzyme exhibited higher activity to chitosans which were 82.8% and 73.2% deacetylated. Kinetics experiments show that chitosans with DD of 82.8% and 73.2% which resulted in lower Km values had stronger affinity for the lipase. The chitosan hydrolysis carried out at 37°C produced larger quantity of COS (chitooligosaccharides) than that at 55°C when the reaction time was longer than 6h, and COS yield of 24h hydrolysis at 37°C was 93.8%. Products analysis results demonstrate that the enzyme produced glucosamine and chitooligosaccharides with DP (degree of polymerization) of 2-6 and above, and it acted on chitosan in both exo- and endo-hydrolytic manner.

Purification and characterization of an immunomodulatory Peptide from bovine placenta water-soluble extract.

An immunomodulatory peptide was isolated from bovine placenta water-soluble extract and purified by consecutive chromatography on DEAE Sepharose CL-6B, Sephadex G-25, and Sephasil C18 column using lymphocyte proliferation assay to identify the active fractions. The immunomodulatory peptide showed a dose-dependent stimulating effect on lymphocyte proliferation. The isoelectric point of the immunodulatory peptide was determined to be 3.82 by capillary isoelectric focusing electrophoresis. The molecular mass of the immunomodulatory peptide was determined to be 2133.52 Da by mass spectrometry. The first 10 amino acid sequence of the immunomodulatory peptide was Tyr-X-Phe-Leu-Gly-Leu-Pro-Gly-X-Thr. This immunomodulatory peptide showed no significant homology with other immunomodulatory peptides. Additionally, it was thermostable, retaining about 60% of immune activity after incubating at 80 degrees C for 30 min.

Nutritional evaluation of caseins and whey proteins and their hydrolysates from Protamex.

Whey protein concentrate (WPC 80) and sodium caseinate were hydrolyzed by Protamex to 5%, 10%, 15%, and 20% degree of hydrolysis (DH). WPC 80, sodium caseinate and their hydrolysates were then analyzed, compared and evaluated for their nutritional qualities. Their chemical composition, protein solubility, amino acid composition, essential amino acid index (EAA index), biological value (BV), nutritional index (NI), chemical score, enzymic protein efficiency ratio (E-PER) and in vitro protein digestibility (IVPD) were determined. The results indicated that the enzymatic hydrolysis of WPC 80 and sodium caseinate by Protamex improved the solubility and IVPD of their hydrolysates. WPC 80, sodium caseinate and their hydrolysates were high-quality proteins and had a surplus of essential amino acids compared with the FAO/WHO/UNU (1985) reference standard. The nutritive value of WPC 80 and its hydrolysates was superior to that of sodium caseinate and its hydrolysates as indicated by some nutritional parameters such as the amino acid composition, chemical score, EAA index and predicted BV. However, the E-PER was lower for the WPC hydrolysates as compared to unhydrolyzed WPC 80 but sodium caseinate and its hydrolysates did not differ significantly. The nutritional qualities of WPC 80, sodium caseinate and their hydrolysates were good and make them appropriate for food formulations or as nutritional supplements.