Oratosquilla oratoria (O. oratoria) were treated with 300, 350, and 400 MPa for 5, 8, and 10 min, respectively. The myofibrillar protein (MP) content, sulfhydryl content, Ca2+‐ATPase activity, surface hydrophobicity and secondary structure of MP were determined to investigate the effects of ultra‐high pressure (UHP) on the biochemical properties and secondary structure of MP from O. oratoria muscle. Results showed that the relatively low pressures have no significant effects on the MP content. When the pressure and holding time increased, the MP content decreased significantly. However, when the pressure condition reached 400 MPa for 10 min, the relative sulfhydryl content and Ca2+‐ATPase activity reduced to 62.76 and 47.88%, respectively, while the relative surface hydrophobicity increased to 132.20%. Moreover, as pressure increased, the β‐Turn and α‐Helix gradually converted to β‐Sheet and Random coil of MP. In short, the biochemical properties and secondary structure of MP from O. oratoria had significant correlations and they interacted with each other. These findings can provide a reference for using UHP to assist the shelling of O. oratoria. Practical applications UHP is an emerging food processing technology that is widely used in the processing of aquatic products, such as shelling. While whether the choice of conditions will affect the meat quality of shelled aquatic products is still less studied. The purpose of this study was to investigate the effects of different UHP parameters on the biochemical characteristics and structure of myofibrillar protein in O. oratoria, and to determine the effects on the quality of O. oratoria meat. These results could provide theoretical guidance for determining the more suitable parameters of UHP, which was conducive to the development of O. oratoria products and the application of UHP technology in aquatic products processing.

Oratosquilla oratoria rich in myofibrillar protein is often shelled, but traditional methods of shelling have certain limitations. In order to better apply the ultra-high pressure (UHP) technology for shelling, the effects of UHP on rheological properties and structure of myofibrillar protein (MP) from O. oratoria treated with a pressure of 300-400 MPa were determined by rheometer and circular dichroism spectrometer. The results showed that in the frequency ramp tests using rheometer, the complex viscosity and G' of MP decreased by 59.08% and 73.70%, respectively, when the pressure reached 400 MPa with holding time of 8 min. As frequency increased, the MP exhibited shear thinning; meanwhile, its storage modulus (G') increased, and solid characteristics became more prominent. In the temperature ramp tests, the MP denatured and its fluidity increased with the increase of temperature. Moreover, the MP from O. oratoria treated with UHP was degraded, and the ionic bond and hydrogen bond were destroyed, while the hydrophobic interaction and disulfide bond increased; the structure of α-helix and β-sheet in the MP converted to β-turn with the increase of pressure and holding time. These findings can provide references for the application of UHP in food processing.

This study explored the effects of four drying methods, namely vacuum freeze-drying (VFD), hot-air drying (HD), microwave drying (MD) and shade drying (SD) on the sensory quality, amino acids composition, phycobiliproteins structure and rehydration rate of Porphyra haitanensis. It showed that VFD dried P. haitanensis had the highest protein (35.44 ± 0.87%), polysaccharide (18.91 ± 0.64%), umami amino acids (484.67 ± 5.03 mg/100 g, dry weight) and essential amino acids (9.89 ± 0.27 g/100 g, dry weight) than another three dried products. Drying affected secondary structure of phycobiliproteins, and the phycobiliproteins from VFD laver contained the most α-helix structure and the least random coil. In addition, VFD processed laver was rich in water-soluble polysaccharides and hydrophilic amino acids, which resulted in its quick rehydration and high-water absorption capacity. The results showed that VFD was suitable for producing high-quality P. haitanensis with excellent flavor and high contents of nutritional compounds.