Bovine skin gelatin hydrolysates as potential substitutes for polyphosphates: The role of degree of hydrolysis and pH on water-holding capacity.

The effects of adding bovine skin gelatin hydrolysate obtained with subtilisin, on water-holding capacity (WHC), in a thermally processed chicken meat model, were investigated. Hydrolysates with different degrees of hydrolysis (DH) (6.57%, 13.14%, and 26.28%) were prepared. The results showed that all the tested hydrolysates improved water retention in the meat matrix. The hydrolysate with 26.28% DH showed similar behavior throughout the full range of concentrations [0% to 5% w/w] compared to that of the positive control (sodium tripolyphosphate [STPP]). In addition, the other hydrolysates [6.57% DH and 13.14% DH at 3% and 2.5% w/w concentrations, respectively] showed behaviors that coincided with that of STPP at its maximum limit allowed. A correlation was observed between the WHC and the pH of the meat samples treated with each hydrolysate or STPP. In addition, it was found that the WHC of the hydrolysates was due to increases in pH and the specific effects of the hydrolysate beyond the typical effects of pH and ionic strength in meat systems. The solubility of all hydrolysates was high (>90%). In conclusion, bovine skin gelatin hydrolysates could serve as an alternative to polyphosphates to improve water retention and the functional properties of thermally processed meat products. PRACTICAL APPLICATION: This study investigated the effects of adding bovine skin gelatin hydrolysate obtained with subtilisin on water-holding capacity (WHC) in a thermally processed chicken meat model. It was found that the hydrolysis of bovine skin gelatin with subtilisin can replace chemical products harmful to health, such as STPP, in terms of water-holding capacity. Therefore, bovine skin gelatin hydrolysate can be used as an ingredient in the formulation of thermally processed meat products.

Immunological characterization of a bacterial protein isolated from salmonid fish naturally infected with Piscirickettsia salmonis.

The Salmon Rickettsia syndrome (SRS) remains a major infectious disease in the Chilean aquaculture. A limited number of Piscirickettsia salmonis proteins have been characterized so far for their use as potential candidates for vaccines studies. In this study, we identified and expressed a highly immunogenic protein of P. salmonis extracted by selective hydrophobicity from crude-cell macerates of naturally infected salmonid fish. One and two-D PAGE gels followed by Western blot analysis with a battery of polyclonal anti-P. salmonis antibodies have allowed the isolation of the target protein. Basic local alignment search (BLAST) done after partial sequencing of the pure protein identified it as a member of the heat-shock protein (HSP) family of prokaryotes. The protein, named ChaPs, was cloned as a single open reading frame encoding 545 amino acid residues with a predicted molecular mass of 57.3 kDa. The amplicon representing the entire novel gene was expressed in vitro in different heterologous systems: the PurePro Caulobacter crescentus expression system from where most of the characterization was attained, and also in the Escherichia coli BL-21 CodonPlus model for commercially potential purposes. The immunologic potential of ChaPs was determined with serum from naturally infected fish.