Physical, chemical and rheological parameters of pressurized swai-fish (Pangasius hypophthalmus) emulsion incorporating fermented soybeans

• Emulsion of swai-fish muscle incorporating fermented thua nao and natto.
• Pressure 400 MPa inducing denaturation of swai-fish emulsion.
• Storage and loss moduli increasing with the increase of pressure.
• Pressurization enabling interaction between fish and soy proteins.

The objective of this study was to investigate the effect of ultra-high pressure on the degree of denaturation of swai-fish emulsion. Accordingly, 90% swai-fish muscle was emulsified with 10% fermented soybeans (as a treatment) and was subjected to high pressure at 400, 500, and 600 MPa for 20 and 40 min at 25 °C. After that, their viscoelastic, physical, chemical and microbiological properties were examined in comparison with those of pressurized 100% swai-fish emulsion (as a control). The results showed that increase of pressure significantly augmented water holding capacity, gel strength and whiteness index of both controls and treatments, while DSC thermograms demonstrated that swai-fish protein was denatured at pressure 400 MPa. However, to eliminate most undesirable microorganism needed higher pressure level. The viscoelastic characterization showed that all storage and loss moduli increased according to the pressure severity which suggested that more cross-link densities were formed at higher levels of pressurization. Furthermore, the electrophoregrams had specified such linking as hydrophobic and disulphide interactions. Some evidences of interaction between fish and soy proteins also indicated by the electrophoregrams.