Author
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LIU, YONGLIANG - VISITING SCIENTIST-CHINA |
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Chen, Yud |
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Submitted to: Journal of Applied Spectroscopy
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/7/2000 Publication Date: 10/1/2000 Citation: N/A Interpretive Summary: To be assured of healthful and safe meats, U.S. legislation requires that each poultry carcass at poultry slaughter plants be inspected by Food Safety and Inspection Service (FSIS) inspectors. Visual and manual inspection on-line is prone to human error and day-to-day and inspector-to-inspector variations. Hence, at the Instrumentation and Sensing Laboratory, we have developed a visible/near-infrared (Vis/NIR) spectrophotometer system aimed at reducing the workload of the inspectors in processing lines, improving the effectiveness of the U.S. federal safety inspection program, and increasing the productivity of processing plants. However, to further improve the mathematics model and select better characteristic spectral wavelengths, it is necessary to explore the fundamental visible/NIR spectral features of chicken meats, with the application of an advanced spectral data analysis technique, namely the newly-developed two-dimensional (2D) correlation method. This is the third report in a series for systematic research on chicken meats using the above strategy. Because storage is a routine process that may affect physical and chemical properties of meat, here we present the results of applying 2D correlation analysis in the characterization of visible/NIR spectral variation of cold-stored chicken meats. The outcome will not only strengthen the scientific understanding of meat structure, but also be able to elucidate the sequential changes occurring in meats such as discoloration and tenderization development, ultimately improving the effectiveness of poultry inspection program. Researchers working on Vis/NIR spectroscopy of food and agricultural products will benefit from the findings of this research. Technical Abstract: This paper reports the generalized 2-dimensional (2D) visible/near-infrared (Vis/NIR) correlation spectroscopy study of chicken meats in cold storage. The 2D visible correlation analysis revealed that, besides the previously reported three absorption bands around 445, 485, and 560 nm ascribed to DeoxyMb, MetMb, and OxyMb, there is an additional band around 635 nm, which could be assigned to sulphmyoglobin, a product from the reaction of MetMb and OxyMb with H2S generated by bacteria. Unlike the spectral intensity reduction of the 440 and 560 nm bands, the intensities of the 490 and 635 nm bands increase with storage time. The asynchronous 2D visible correlation spectra indicated that OxyMb and MetMb produce sulphmyoglobin first, then complicated reactions such as the oxygenation and oxidization of DeoxyMb and the oxidization of OxyMb follow as storage is prolonged. In addition, several close and separated bands appearing around 440, 490 and 560 coordinates could be a result of the changes in th molecular environment of the heme pigment portion. Hence, the intensity decreasing and the splitting of the 440 and 560 nm bands are responsible for the discoloration of meats. The 2D correlation spectra in the NIR region showed that the O-H/N-H bands change their spectral intensity before the C-H groups during the storage. It indicated two possibilities: (1) water species interact with other meat components and (2) the meat proteins undergo proteolysis and denaturation processes, which associated with the development of tenderization during storage (aging). In addition, the asynchronous spectra correlating the spectral bands both in the visible and NIR regions suggested that the discoloration phenomenon actually occurs earlier than other developments, such as tenderization process. |
