5/17/2023 0 Comments Beijing duck chef chen georgiaAccording to experience, the roast duck chef determined that the roasting time of the experimental duck was 60 min. The top and bottom temperatures of the oven were between 202 and 203 ☌, and the center temperature was 224 ☌ during roasting. Finally, the ducks were hung in the traditional oven (Gua-lu) for roasting by the experienced roast duck chef. Before roasting, the ducks were thawed at 2~4 ☌ and heated to room temperature. Afterward, the ducks were frozen at −5 ☌ for 2–3 days to make the skin of the duck thicker and more delicious. The mass ratio of caramel and maltose to water was 1:8. To make the body color acceptable, caramel and maltose were used before freezing. After blanching, the duck was dried for 2~4 h in a room at 2~4 ☌. Then, boiling water (100 ☌) was poured onto the surface of the duck 3 times, and the time of this procedure was controlled to 3~5 s. Air inflation was a necessary step in which air was pumped into the duck between the skin and subcutaneously, making the duck look appealing. The ducks were processed according to traditional techniques at Dongxinglou restaurant in Beijing (located in Dongzhimen, Chaoyang District). After slaughter, the ducks were cooled and then transported to the restaurant for processing. The same batch of Beijing four-series stuffed ducks, 42 days old, were used as experimental materials, and the weight of each duck was 2000 ± 300 g. (Jiugong Town, Daxing District, Beijing, China). The raw duck was supplied by Beijing Jinxing Ducks Co., Ltd. The duck is hung on an iron hook in the oven, and fruitwood is used to roast the duck by fire. The traditional hanging ovens (Gua-lu) differ greatly from other ovens in that they have an arched mouth but no door. Beijing ducks were processed according to traditional techniques, such as air inflation, blanching, drying, coloring, etc., and finally hung in the oven for roasting by the experienced roast duck chef. However, the thermal denaturation of meat proteins and its influence on the texture properties of processed products during roasting, such as Beijing roast duck, are still not well-understood. No noticeable degradation of myosin has been observed at 80 ☌, and actin did not degrade during heating. Whereas myosin light chain and tropomyosin are heat-stable and the polymerization of proteins is increased, and heating induces the cleavage of proteins near aspartic acid residues. Actin, myosin heavy chain, and sarcoplasmic protein are aggregated after roasting. The hydrophobicity and aggregation of proteins in meat increased after heat treatment. The temperature and time of roasting had a great influence on the denaturation and contraction of the myofibril. The muscle fiber was found to be broken, and the connective tissue was intact after roasting. Hydrolysates produced by protein degradation are abundant in meat, and some of these tenderness-related proteins differ greatly between tender and tough samples. The turning points were at 20 and 40 min, and the main proteins were denatured, leading to the formation of tenderness of Beijing roast duck. Muscle fibers were damaged and shrunken, accompanied by the formation of hydrophobic interactions and the reduction of ionic bonds. Thirdly, roasting induced protein thermal denaturation, which was correlated with interprotein forces, texture profile, and the shear force. The formation of hydrophobic interactions and the reduction of ionic bonds were observed. Secondly, the main myofibrillar proteins were denatured at 20 and 40 min, respectively. The sarcomere considerably contracted within 30 min. Firstly, Band I was broken and twisted, Band A was overstruck, and Z-line was diffused and finally disappeared, resulting in a blurred myofibril structure. Shear force decreased significantly during the first 20 min, and the texture profile largely changed at 20 and 40 min. Results indicated that the surface temperature of Beijing roast duck increased from 23.9 to 174.4 ☌, while the center temperature rose from 20.6 to 99.3 ☌ during roasting. To investigate the mechanism of the texture formed by protein thermal denaturation, the profile and formation of texture and thermal denaturation of protein were evaluated using texture profile analysis (TPA) and transmission electron microscopy (TEM) combined with differential scanning calorimeter (DSC).
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