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In order to investigate the effect of low-temperature air cooling on the postmortem energy metabolism and meat quality of yellow-feathered broilers during mixed cooling (first water cooling and then air cooling), 85-day-old broilers were slaughtered and divided into three groups: treatment (water cooling at 0–4 ℃ followed by air cooling at −8, −18, −25 or −31 ℃), control (traditional water cooling at 0–4 ℃) and traditional mixed cooling (water cooling at 0–4 ℃ followed by air cooling at 0–4 ℃) groups. Finally, all carcasses were cooled to an internal temperature of 4 ℃, and the optimal air cooling temperature was determined by measuring cooling rate, pH, energy metabolism and quality indexes. The results showed that the cooling time of air cooling at −25 and −31 ℃ was 2 537 and 2 272 s, respectively, which was shortened by 27.78% and 35.33% compared with the traditional water cooling and by 51.87% and 56.90% compared with the traditional mixed cooling, respectively. Air cooling at −25 and −31 ℃ delayed the decrease in pH, reduced the drip loss and cooking loss of broiler breast muscle, significantly increased the shear force and the content of immobilized water compared with the control group (P < 0.05). Compared with the other groups, the activities of muscle hexokinases, phosphate-3-phosphate dehydrogenase and lactate dehydrogenase in the air cooling treatments at −25 and −31 ℃ were lower, and the consumptions of adenosine triphosphate (ATP) and glycogen, the production of lactic acid and adenosine monophosphate (AMP) and AMP/ATP ratio were the smallest (P < 0.05). The above findings showed that air cooling at −25 and −31 ℃ significantly inhibited the rate of anaerobic glycolysis during the early postmortem period in chicken meat, delayed the rate of pH decline, and effectively improved muscle water retention. From the perspective of industrial energy saving, −25 ℃ is determined as the best temperature for air cooling treatment.

To investigate the shelf life of eggs from different chicken breeds stored at various temperatures, Haugh unit, air cell depth, yolk index, albumen pH and mass loss of eggs from Jingfen 6 and Hy-Line Grey laying hens stored under refrigerated (4 ℃) or room temperature (25 ℃) conditions were examined. Taking Haugh unit below 60 as the end of shelf life, the shelf life of eggs from both breeds was found to be 12 and 83 days under ambient and refrigerated storage conditions, respectively. To develop prediction models for egg shelf life and storage time using back propagation artificial neural network (BP-ANN), Haugh unit, the most important indicator of egg freshness, was taken as an input parameter, and the other input parameters were selected based on the results of Pearson correlation analysis and used in descending order of correlation with Haugh unit. The specific input parameters were determined based on the performance of the models on the prediction set, and the BP-ANN models with optimized number of neurons in the hidden layer were compared with the other machine learning models partial least squares regression (PLSR) and support vector regression (SVR) models. The results showed that the BP-ANN models had higher accuracy in predicting the remaining shelf life and storage time of eggs compared to the PLSR and SVR models. This study provides a reference for determining the shelf life of eggs at different storage temperatures and technical support for the rapid, accurate and simultaneous prediction of the remaining shelf life and storage time.

To investigate the effects of ultra-high pressure (UHP) treatment and vegetable oil addition on its heat-induced gel properties, rabbit myosin was subjected to UHP treatments (10 ℃/2 min) at different pressure levels (100, 150 and 200 MPa), and then mixed with different amounts (0%, 10%, 20% and 30%) of soybean oil and phosphate buffer to prepare emulsion systems, whose heat-induced gelation was carried out at a programmed heating rate of 1 ℃/min. Myosin not treated by UHP served as control. The storage modulus G’, loss modulus G”, gel strength, water-holding capacity (WHC), microstructure and relaxation time spectra of heat-induced myosin gels were measured by rheometer, texture analyzer, scanning electron microscope (SEM) and low-field nuclear magnetic resonance spectroscopy (NMR). The results showed that compared with the control group, the storage modulus, loss modulus, gel strength and WHC of heat-induced myosin gels were increased significantly by high pressure treatment and the addition of soybean oil. SEM revealed that the three-dimensional network structure became denser and more compact. The NMR analysis showed that the relative content of free water in the gel matrix gradually decreased with an increase in pressure, and the degree of proton binding of immobilized water and the relative content of bound water significantly increased. Under the same pressure, the G’, G”, gel strength and WHC increased with increasing addition of soybean oil, showing significant differences among addition levels (P < 0.05). The 200 MPa + 30% soybean oil group had the best heat-induced gel properties. Therefore, appropriate high-pressure treatment combined with the addition of soybean oil enhanced the interaction between protein and fat, and changed the microstructure and water distribution state and consequently gel properties such as rheological properties, texture and WHC of heat-induced myosin gels, which played a positive role in improving the functional properties of heat-induced rabbit myosin gels.

A machine vision system was used to collect 948 three-dimensional images of chicken carcasses on the broiler slaughter line. This study aimed to develop a rapid method for the identification of primary dermatitis in chicken carcasses. The acquired images were preprocessed and segmented into 128 × 128 pixel pictures with grids. A total of 762 pictures of dermatitic skin and 775 pictures of normal skin were selected. A total of 24 feature values were extracted including third-order color moments, mean and variance of gray-level co-occurrence matrix features, Tamura texture features from the 1 537 pictures and the segmentation threshold and area of dermatitis region. Based on dimensionality reduction by principal component analysis (PCA), linear discriminant analysis model, quadratic discriminant analysis model, support vector machine, random forest, back propagation neural network (BPNN) and GoogLeNet models were established, and their classification performances were compared. Among these models, the GoogLeNet model was the most effective in classifying dermatitic skin samples with an overall accuracy of 90.5% and an average detection speed of 122.65 sheets per second. The prediction accuracy of the model for chicken carcasses with dermatitis was 100%, while that for qualified chicken carcasses was 90%.

In this study, the physiology, biochemistry, safety and functional properties of Staphylococcus used as a starter culture were analyzed. Among the 33 strains of Staphylococcus, 11 tested positive for catalase and negative for hydrogen sulfide and their safety was evaluated by hemolysis, plasma coagulase and heat-resistant nuclease tests. In the functional study, 8 of the 11 strains were able to produce lipase and decompose fat and had high cholesterol degradation capacity. In the acid tolerance test, 4 strains were selected for strong acid resistance. The 4 strains could degrade casein, myofibrillar protein, sodium nitrite and some bioamines. They were identified as S. warneri 5F’-2, S. vitulinus 8A-1, S. warneri 5F-2 and S. succinus A31. These strains were positive for catalase, unable to produce hydrogen sulfide, and negative for hemolysis, plasma coagulase negative and heat-resistant nuclease. They had the functional properties of lipase production, cholesterol degradation, acid tolerance, protease production, myofibrillar protein degradation, nitrite degradation, and inability to degrade amino acids to produce bioamines, and biogenic amine degradation. Therefore, they had excellent fermentation potential, and could be used as strains for meat product fermentation.