Study on the protein fractions extracted from the muscle tissue of Pinctada martensii and their hydrolysis by pancreatin

Pinctada martensii muscle proteins were separated into water‐soluble, salt‐soluble and insoluble protein fractions. The salt‐soluble protein fraction was the most abundant, comprising approximately 66.3% of the protein, followed by the water‐soluble and insoluble protein fractions in decreasing order. sodium dodecyl sulphate polyacrylamide gel electrophoresis profiles showed that 35‐ and 97‐kDa peptides represented the highest proportions of the water‐soluble and salt‐soluble protein fractions, respectively. The three protein fractions contained high levels of flavourful amino acids (Glu, Asp, Ala and Lys), with the water‐soluble protein fraction having the highest level (47.1%). The size exclusion chromatography profiles of the water‐soluble and salt‐soluble protein pancreatin hydrolysate demonstrated no significant differences in the molecular weight distributions in the >20 000, 5000–10 000 and 2000–5000 Da fractions, while those of the insoluble protein pancreatin hydrolysate were different. In conclusion, the results provided some basic information that would contribute to the utilisation of these protein fractions.     

Study on inactivation mechanisms of Listeria grayi affected by pulse magnetic field via morphological structure,Ca2+ transmembrane transport and proteomic analysis

The inactivation mechanism of PMF on Listeria grayi (L. grayi) was investigated through the analysis of biological effects as well as the monitoring of morphology, membrane permeability and intracellular proteins of cells. Under the optimal inactivation conditions of PMF (2.5 T and 25 pulses), the analysis of transmission electron microscopy (TEM) and laser scanning confocal microscopy (LSCM) showed that PMF‐treated cells membranes were damaged, resulting in the increase in intracellular Ca²⁺ fluorescence intensities. A significant (P < 0.01) negative correlation between intracellular Ca²⁺ fluorescence intensities and the amount of colonies was found. Proteomic analysis showed that the mode‐of‐action of cells outer membrane, the stability of intracellular proteins and the metabolism‐related proteins might be affected by PMF. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that PMF treatment could affect the nitrogen, organic and energy metabolisms of L. grayi, inducing the death of cells finally.     

Separation and identification of hen egg protein isoforms using SDS–PAGE and 2D gel electrophoresis with MALDI-TOF mass spectrometry

Knowledge of the chemical composition and physicochemical properties of native egg white and yolk is necessary to interpret the functional and biological properties attributed to specific egg components. To date, many of the proteins located in this complex biological fluid remain uncharacterised, if not unknown. High-resolution techniques for proteome analysis, including SDS–PAGE and 2-dimensional (2D) gel electrophoresis, combined with mass spectrometry, were employed to separate and identify several protein components in hen’s egg. An advanced and sensitive glycoprotein staining kit was used to detect the presence of glycosylated proteins in the egg samples. Numerous spots were revealed when a mixture of egg white and yolk was subjected to 2D gel electrophoresis. Several of the already known egg proteins were identified. Isoforms of ovalbumin and conalbumin were visualised. The presence of FLJ 10305 and Fatso proteins in the proteome of Gallus domesticus was also confirmed.     

Studies of the effect of hydrostatic pressure pretreatment on thermal gelation of chicken myofibrils and pork meat patty

The structures and characteristics of pressure–heat-induced gels of chicken myofibrils and pork patty were investigated. The M-line and Z-line in the chicken myofibril in 0.2 M NaCl were disrupted, and both of the thin and thick filaments were dissociated by pressure treatment. The microstructure of pressure–heat-induced chicken myofibrillar gel was composed of three-dimensional fine strands. Pressurization, at 200 MPa, prior to heating, increased the apparent elasticities of chicken myofibrillar gel and pork patty; however, pressure treatment above 200 MPa decreased it. The apparent elasticity of the pressure-treated (200 MPa) thermal myofibrillar gel was three times higher, and that of pork patty was twice higher than those of the unpressurized ones. The rheological properties of the low salt (1% NaCl) pork sausage can be improved by pressure treatment at 200 MPa prior to heating.