The effect of ultrasound treatments (40 kHz, 300 W) for different times (10, 20, 30 and 40 min) combined with different salt contents (1.0 %, 1.5 % and 2.0 %) on gel properties and water holding capacity (WHC) of chicken breast meat batter were investigated. Results showed salt level significantly (p < 0.05) affected the texture, storage modulus (G′), loss modulus (G″), cooking loss and WHC. Ultrasound treatments for 10 min and 20 min improved the texture and WHC, and had higher G′ values. Compared with the controls (2 % salt), ultrasound treatment for 20 min with reduced-salt (1.5 %) had not significant effect (p > 0.05) on texture, cooking loss or WHC. However, longer ultrasound (40 min) treatment resulted in a decrease in hardness, G′ value and WHC. Microstructural analysis revealed that gels treated with ultrasound for 20 min had a compact structure whereas those treated for 40 min contained more protein aggregations and more cavities. Low-field nuclear magnetic resonance (LF-NMR) indicated that ultrasound treatment for 20 min lowered the values of spin-spin relaxation time (T2) and increased the proportion of myofibillar water. Overall, high power ultrasound technology is a promising process which can improve the gelation properties and thereby allowing for a partial reduction in the salt levels in chicken meat gels.

•Phospholipase A2 and C retained most of their activity at the end of drying process.•Evaluation of the relationship between lipids and phospholipase in dry-cured duck.•Phospholipase A2 and C contribute to the degradation of intramuscular phospholipids.Phospholipid hydrolysis, as the main stage and cause of phopholipid degradation, is generally attributed to phospholipases. In this study, the changes of phospholipase A2 (PLA2) and C (PLC) activities, neutral lipid, free fatty acids and phospholipids in dry-cured duck leg muscles during processing, were examined. The composition of free fatty acids and neutral lipids increased significantly (P < 0.05) with extension of processing time while the phospholipids composition decreased. The PLA2 and PLC activity decreased in the final product, but retained 83.70% and 86.78% of their initial activities, respectively. The relative activities of both PLA2 and PLC highly correlated with the decline of phospholipids and the increase of free fatty acids. High correlations were also obtained between the relative activities of PLC and the increase of neutral lipid (P < 0.01). All these results suggest that PLA2 and PLC contribute to the degradation of intramuscular phospholipids during the processing of dry-cured duck.

The state of water in high-pressure-thawed and conventionally water bath-thawed chicken breasts was analyzed using low-field nuclear magnetic resonance. The influence of high-pressure thawing on water holding capacity, including thawing loss, cooking loss and expressible fluid, was evaluated. Thawing loss was significantly reduced (p < 0.05) compared to the conventional thawing method but neither cooking loss nor total expressible fluid changed significantly (p > 0.05). Higher thawing pressures lead to the T21 relaxation time being increased from 39.9 to 55.9 ms, and P21 increased from 89.5 to 94.9 %. Significant negative correlations (p < 0.01) were observed between the thawing loss and T21, T22, P21. These results indicate that high thawing pressures can transform the water from the loosely bound water fraction (T22) to a more tightly bound (T21) water fraction with the increase in water relaxation time.

In order to explore novel processing for modifying the functional properties of pale, soft, exudative (PSE)-like chicken breast meat, we investigated the effects of high-intensity ultrasound on the functional and rheological properties, particle size distribution, microstructure, and protein secondary structures of PSE-like meat batter suspension. Normal and PSE-like chicken breast meat batter suspensions (7.5 % meat proteins, w/w) were prepared and treated by ultrasound for either 0, 3, or 6 min (frequency 20 kHz and amplitude 60 %). Ultrasound treatment significantly increased pH, gel strength, and water holding capacity of normal and PSE-like meat gels (P < 0.05). Ultrasound treatment altered the rheological behavior of normal and PSE-like batter samples, which was accompanied with the increase of the elastic (G′) and viscous (G″) modulus. After ultrasound treatment, the microstructure of heated normal and PSE-like batter samples enabled the formation of a compact and more dense gel network. Ultrasound treatment reduced the salt solubility of myosin as indicated by its intensity in SDS-PAGE. However, the particle size of ultrasound-treated normal and PSE-like batter samples was reduced and became more uniform. Moreover, ultrasound decreased the α-helical content and increased the formation β-sheet, β-turns, and unordered contents of normal and PSE-like meat proteins. These results suggest that high-intensity ultrasound may be used to modify the functionality of PSE-like meat with the potential to increase economical benefits for the poultry industry.

In this study, intramuscular phospholipid classes and molecular species in Gaoyou duck meat were determined. Classes of phospholipids were identified and quantified by normal phase HPLC combined with UV and evaporative light scattering detectors (ELSD). The main phospholipid classes (phosphatidylcholine and phosphatidylethanolamine) were prepared on a semi-preparative silica gel column by HPLC. Reverse phase HPLC was coupled in parallel with both an ELSD and a mass spectrometry in order to characterise molecular species of phosphatidylcholine (PC) and phosphatidylethanolamine (PE). The results showed that Gaoyou duck meat had high quantities of PC and PE (64.66% and 28.10% of total phospholipids, respectively). Arachidonic acid was mainly present in PE and formed molecular species containing a saturated fatty acid, such as stearic or myristic acid; however, oleic acid together with palmitic or stearic acid formed the main molecular species in PC. The content of the molecular species with polyunsaturated fatty acids in PE accounted for 98.33%, while that in PC only 46.20%.

The effect of microbial transglutaminase (MTG) on nuclear magnetic resonance relaxation (NMR) behaviour, water holding capacity (WHC) and microstructure of pork myofibrillar protein (PMP) gel was studied. The enzymatic protein preparation had significantly lower values of spin–spin relaxation time (T2), higher WHC and more porous microstructure in comparison with the control system. T2 was reduced from 226 ms (peak value) of the PMP gel containing no MTG to 188 ms of the PMP gel containing 2 U/g protein. However, no further decrease was shown when the concentration of MTG increased. The reduction was attributed to reduced mobility of water protons in the system. Scanning electron micrographs (SEM) showed the mobility of water in the proteins gel network was related to gel microstructure.

N-nitrosamines, biogenic amines and residual nitrite are harmful substances and often present in cured meat. The effects of gamma-irradiation (γ-irradiation) on these chemicals in dry-cured Chinese Rugao ham during ripening and post-ripening were investigated. Rugao hams were irradiated at a dose of 5 kGy before ripening and were then ripened in an aging loft. Although γ-irradiation degraded tyramine, putrescine and spermine, on the other hand, it promoted the formation of spermidine, phenylethylamine, cadaverine and tryptamine. Residual nitrite was significantly reduced by γ-irradiation. N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA) and N-nitrosopyrrolidine (NPYR) were found in Chinese Rugao ham during ripening and post-ripening but could be degraded with γ-irradiation. The results suggest that γ-irradiation may be a potential decontamination measure for certain chemical compounds found in dry-cured meat.

In this study, culture-dependent and culture-independent approaches were used to reveal the microbial diversity and dynamic changes occurring in sliced vacuum-packed cooked ham after high pressure processing (HPP, 400 MPa or 600 MPa for 10 min at 22 °C) during refrigerated storage over 90 days. Direct extraction of genome DNA and total RNA from meat samples, followed by PCR-denaturing gradient gel electrophoresis (DGGE) and RT-PCR-DGGE on 16S rDNA V3 region, was performed to define the structure of the bacterial populations and active species in pressurized cooked ham. Results showed that HPP affected differently the various species detected. The predominant spoilage organisms of cooked ham, such as Lactobacillus sakei and Lactobacillus curvatus, were found to be very sensitive to pressure as they were unable to be detected in HPP samples at any time during refrigerated storage. Weissella viridescens and Leuconostoc mesenteroides survived HPP at 600 MPa for 10 min at 22 °C and were responsible for the final spoilage. An RNA-based DGGE approach clearly has potential for the analysis of active species that have survived in pressurized cooked ham. High pressure processing at 400 or 600 MPa for 10 min at room temperature (22 °C) has a powerful inhibitory effect on the major spoilage bacteria of sliced vacuum-packed cooked ham. High pressure treatment may lead to reduced microbial diversity and improve the products' safety.

•Biofilm formation in meat substrate was less and lower than that in TSB.•Salmonella showed different biofilm architectures in two tested media.•ATR-FTIR and Raman could differentiate biofilm from its planktonic cells.•Polysaccharide and proteins could be served as useful markers of biofilm formation.•Biofilm formation of Salmonella was achieved through four different steps.Salmonella biofilm on food-contact surfaces present on food processing facilities may serve as a source of cross-contamination. In our work, biofilm formation by multi-strains of meat-borne Salmonella incubated at 20 °C, as well as the composition and distribution of extracellular polymeric substances (EPS), were investigated in situ by combining confocal laser scanning microscopy (CLSM), scanning electron microscope (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy. A standard laboratory culture medium (tryptic soy broth, TSB) was used and compared with an actual meat substrate (meat thawing-loss broth, MTLB). The results indicated that Salmonella grown in both media were able to form biofilms on stainless steel surfaces via building a three-dimensional structure with multilayers of cells. Although the number of biofilm cells grown in MTLB was less than that in TSB, the cell numbers in MTLB was adequate to form a steady and mature biofilm. Salmonella grown in MTLB showed “cloud-shaped” morphology in the mature biofilm, whereas when grown in TSB appeared “reticular-shaped”. The ATR-FTIR and Raman analysis revealed a completely different chemical composition between biofilms and the corresponding planktonic cells, and some important differences in biofilms grown in MTLB and in TSB. Importantly, our findings suggested that the progress towards a mature Salmonella biofilm on stainless steel surfaces may be associated with the production of the EPS matrix, mainly consisting of polysaccharides and proteins, which may serve as useful markers of biofilm formation. Our work indicated that a combination of these non-destructive techniques provided new insights into the formation of Salmonella biofilm matrix.