Characterization of the bacterial community of braised chicken, a specialty poultry product in China.

High-throughput sequencing of 16S rDNA and culture-dependent methods were applied to determine the bacterial communities of braised chicken during processing and storage. Environmental microorganisms were also evaluated using a sedimentation plate method. The results showed that airborne microbial counts in the braising room were higher than those in the control room (25°C, a space to lower the temperature of the chicken products) and storage rooms (4°C). The microbial identification technique 16S rDNA sequences has indicated that more than 229 operational bacterial species were associated with the microbiota present in braised chicken, largely involving Pseudomonas, Psychrobacter, Weissella, Kurthia, Brochothrix, and Lactobacillus in modified-atmosphere packing (MAP) products. The storage place and temperature during processing has great impact on the shelf life of the chicken. The microbes in MAP were significantly higher (P < 0.05) in 0 and 7th day, while the microbial activity in vacuum packaging (VP) was lower because the VP products were treated at higher temperature (100°C for 20 min). Within chicken products, Pseudomonas, Brochothrix, and Lactobacillus were most prevalent in MAP products. According to this research, in order to prolong the shelf life of meat products, proper storage places and packaging conditions are necessary to be improved to reduce the microbial load in the food products.

Effect of chopping time and heating on 1 H nuclear magnetic resonance and rheological behavior of meat batter matrix.

The effect of chopping time and heating on physicochemical properties of meat batters was investigated by low-field nuclear magnetic resonance and rheology technology. Cooking loss and L* increased while texture profile analysis index decreased between chopping 5 and 6 min. The relaxation time T21 (bound water) and its peak area ratio decreased, while the ratio of T22 peak area (immobilized water) in raw meat batters gradually increased with the extension of chopping time. However, T22 was opposite after being heated and a new component T23 (free water) appeared (T2i is the spin - spin relaxation time for the ith component.). The initial damping factor (Tan δ) gradually decreased and there were significant difference between 4 and 5 min of chopping time. There were significantly positive correlations between the ratio of peak area of T22 and chopping time, the storage modulus (G'), cooking loss, and L*, respectively. Continued chopping time could improve the peak area proportion of T22 in raw meat batters. Further, the higher the peak area proportion of T22 in raw meat batters, the cooking loss of heated meat gel was higher. Also, the stronger the mobility of immobilized water in meat batter, the higher the L* of the fresh meat batters. Thus, it is revealed that the physicochemical properties of meat batter are significantly influenced by chopping time which further affects the water holding capacity and the texture of emulsification gel.

Characteristic Flavor of Traditional Soup Made by Stewing Chinese Yellow-Feather Chickens.

The traditional recipe for Chinese chicken soup creates a popular taste of particular umami and aroma. The present study investigated the effects of stewing time (1, 2, and 3 h) on the principal taste-active and volatile compounds and the overall flavor profile of traditional Chinese chicken soup by measuring the contents of free amino acids (FAAs), 5'-nucleotides, minerals and volatile compounds and by evaluating the taste and aroma profiles using an electronic nose, an electronic tongue and a human panel. Results showed that the major umami-related compounds in the chicken soup were inosine 5'-monophosphate (IMP) and chloride, both of which increased significantly (P < 0.05) during stewing. The taste active values (TAVs) of the equivalent umami concentration (EUC) increased from 4.08 to 9.93 (P < 0.05) after stewing for 3 h. Although the FAA and mineral contents increased significantly (P < 0.05), their TAVs were less than 1. The volatile compounds were mainly hexanal, heptanal, octanal, nonanal, (E)-2-nonanal, (E)-2-decenal, (E,E)-2,4-decadienal, 1-hexanol, and 2-pentyl furan. With the prolonged stewing time, the aldehydes first increased and then decreased significantly (P < 0.05), while 1-hexanol and 2-pentyl furan increased steadily (P < 0.05). The aroma scores of the chicken soup reached the maximum after stewing for 3 h. The discrepancy in overall flavor characteristics tended to stabilize after 2 h of stewing. In general, stewing time has a positive effect on improving the flavor profiles of chicken soup, especially within the first 2 h.

Low-field NMR determination of water distribution in meat batters with NaCl and polyphosphate addition.

The objective was to elucidate the influence of NaCl and polyphosphates in the stage of protein swelling on the water-holding capacity (WHC) of meat batter. The meat batters were formulated with salt in different ways by adding established amounts of only NaCl, only polyphosphates, jointly adding NaCl and polyphosphates, and a control without any salt. An increase (p<0.05) in water retention was found when a combination of NaCl and polyphosphates was used. A high textural parameter was observed in the two treatments with NaCl, but not in the group with only polyphosphate. For the polyphosphate group, T22 was lower (p<0.05) than in the other three before heating; however, after heating, T21 and T22 were both significantly decreased, and a new component emerged, T23, which was significantly lower than the others. For the NaCl treatment, heated or not, T22 was always the highest. It was revealed that NaCl had affected the WHC by increasing the mobility and distribution of water, particularly with polyphosphate, but polyphosphate could not be an equal substitute for NaCl given its resulting lowest textural properties and poor microstructure. By presenting different hydration states in the protein swelling stage, the meat batter qualities were differentiated.

Nonvolatile taste compounds in cooked Chinese Nanjing duck meat following postproduction heat treatment.

UNLABELLED: Taste-active compounds, including free amino acids, succinic acid and 5'-nucleotides, and chemical components including moisture, pH, protein, crude fat, and sodium chloride were evaluated in cooked and packaged Chinese Nanjing ducks following heat treatments including control, 99 °C for 40 min, 108 °C for 20 min, 92 °C microwave followed by water heating, 95 °C for 30 min, 121 °C for 25 min. Heat treatment decreased (P < 0.05) the content of Alamine and moisture and reduced the pH value in muscle, but increased (P < 0.05) the protein and 5'-nucleotides content. The 99 °C group had a significantly lower crude fat content compared with other groups (P < 0.05). The succinic acid content in the control group was significantly higher than in the 121 °C group (P < 0.05). Groups treated at higher temperatures (108 °C, 121 °C, and microwave) had similar equivalent umami concentrations and 5'-nucleotides, free amino acids content, as well as the derived bitter and sweet taste components compared with the groups treated at lower temperatures. It can be speculated that these differences account for the enhanced flavor of the meat in the 99 °C, 108 °C, 121 °C, and microwave groups compared with the untreated control. Therefore, heat treatment at lower temperature after packaging may prolong product shelf life without any detrimental effects on taste. The results of this study indicate that it is important to use lower temperatures in this type of food processing. However, it may be possible to modify the primary processing steps to improve the content of umami-like taste compounds such as 5'-nucleotides. PRACTICAL APPLICATION: Heat treatment of packaged products is an effective method for eradication of microbes, therefore increasing the shelf-life. However, such treatment can result in major changes in the sensory perception of meat products, particularly the formation of off-flavors. This study investigated changes in taste-active compounds in duck meat following a number of types of heat treatment.