The Quality And Detection Of Thawed Pork And Water Injected Pork

China has a big consumption of pork. It is of great significant to pay attention to pork quality which is including sensory characteristics, technical indexes, nutritive values and sanitary conditions. Different processing and storage methods can influence the water content of pork leading to the change of its sensory characteristics and technical indexes which has attracted domestic and international scholars’ attention and many studies have been done. However, there are few studies about nutritive values and sanitary conditions of pork with different water content. In the pork markets of our country, pork with different treatments has no labels and problems of water injection may be found which may harm peoples’ health. A rapid method of detecting pork with different water content is needed urgently for consumers.On account of the scientific problems above and in combination with the practical situation of pork consumption market in China, this study chose fresh longissimus muscles as experimental samples to investigate the influence of water injection and thaw on nutritive values and sanitary conditions of pork. The method of detecting water injected and thawed pork quickly by LF-NMR technology was explored and the software about detecting water injected and thawed pork was made to provide technical support for detection of water injected and thawed pork.The main contents are as follows:1. Nutritional quality of thawed pork and its LF-NMR-based detectionThis study was designed to investigate the influence of thawing on pork nutrition and the feasibility of detecting thawed pork by LF-NMR technology. Five pieces weighing 100 g respectively were removed from pork longissimus dorsi muscle along the direction of perpendicular to the muscle fibers of which four pieces were frozen at-20℃ for 1 d,3 d, 5 d and 7 d respectively and then thawed at 0-4℃ for 24 h and the other one was treated as a control. The lost juice was collected to determine the content of proteins, amino acids and mineral elements. Pork longissimus dorsi muscle was divided into 82.5 cm-thick pieces along the direction of perpendicular to the muscle fibers at 5 h postmortem. These pieces were divided into four groups averagely which were stored at 0-4℃ for 0 h,24 h, 48 h and 72 h respectively. One piece in each group was frozen for 24 h at-18℃ and then thawed for 12 h at 0-4℃ and the other one was not treated. The color parameters L*, a* and b* and NMR T2 were measured; The result showed that thaw would significantly increase the total loss of proteins, mineral elements and amino acids, reduce the peak time (t21), area (A21) and area ratio (P21) of the second peak (T21) of LF-NMR T2 relaxation time and increase the redness (a*). These four indexes of t21、A21、P21、a* can be used to detect thawed pork.2. The quality of water injected pork and its LF-NMR-based detectionThis study was designed to investigate the influence of water injection on pork’s nutritive values, shelf life and the feasibility of detecting water-injected pork by LF-NMR. Pork longissimus dorsi muscle was injected with distilled water at doses of 0%,8.72%, 14.23% and 17.03% respectively at 5 h postmortem. The color parameters L*, a* and b* and LF-NMR T2 relaxation time were measured at 0,12 and 24 h respectively after injection; Three pieces weighing 100 g respectively were removed from pork longissimus dorsi muscle along the direction of perpendicular to the muscle fibers of which two pieces were injected with distilled water at doses of 5% and 10% and the other one was treated as a control. These pieces were stored at 0-4℃ for 24 h and then the lost juice was collected to determine the content of proteins, amino acids and mineral elements. The results showed that water injection would significantly increase the total loss of proteins, mineral elements and amino acids and shorten the shelf life of pork. With the increase of water injection rate, the peak time (t21), area (A21) and area ratio (P21) of the second peak (T21) of LF-NMR T2 relaxation time decreased and the lightness (L*) increased. These four indexes of t21、A21、 P21、L* can be used to detect water injected pork.3. Investigation and statistics of commercially available pork and exploitation of detecting and analysis softwareNine hundred of commercially available fresh meat samples were investigated in different seasons. The result revealed that seasons had significant influence on the color of pork while no remarkable effect was determined on t21 and A21. It was dependable to take the immobilized water parameter as the detecting index. In addition, a software prototype of testing and analysis for water-injected and thawy pork was developed according to the statistical analysis results and the standard databases of water-injected and thawy pork mentioned in the first two chapters.