Progress 01/15/08 to 01/14/13
Outputs
OUTPUTS: The primary objective of this research project is to elucidate the physicochemical mechanism of free radical-mediated protein modification in muscle fibers and the impact on water-binding and hydration properties of meat at different ionic strength conditions. Four graduate students (3 Ph.D. and 1 M.S.) were trained through this project, all of whom have presented research findings at professional meetings - the Institute of Food technologists (IFT) and the American Meat Science Association (AMSA) - and published in scientific journals. One Ph.D. student is now a research scientist in a food company (COFCO) and another is a postdoctoral researcher in a university (Wisconsin). Of special note is that all four graduate participants received national awards for their research presentations: two 1st-Place Awards (2010, 2012) and two 3rd-Place Awards (2011, 2012) in the IFT Muscle Food Division Graduate Paper Competition. In addition, the PD of the project has attended six national meetings (IFT, AMSA, and American Chemical Society) and one international conference (International Congress of Meat Science and Technology) to present major findings from the study. The PD also visited three countries (China, France, and Canada) to interact and communicate through seminars and discussions with scientists from diverse sectors of the food industry, academia, government, and consumer groups. In these meetings, the PD shared major discoveries from this research project and fostered international collaboration as related to the protein oxidation research. Resulting from these contacts and seminars, four international scientists and 4 outstanding graduate students were attracted to the University of Kentucky to conduct collaborative research as related to this project. PARTICIPANTS: Y.L. Xiong, Project Director. Provided training for graduate students and postdoctoral researchers and oversaw the project. R.M. Delles, Graduate Student (M.S. then Ph.D.). Conducted the experiments on meat hydration when packaged under high-oxygen atmosphere conditions. Z. Liu, Graduate Student (Ph.D.). Studied the mechanism of water absorption in muscle fibers under oxidative stress. C. Li, Graduate Studnet (Ph.D.). Investigated cross-linking of oxidatively stressed myosin at low and high salt concentrations and the impact on water-holding capacity of gels in the presence of microbial transglutaminase. C. Liu, Graduate Student (M.S.). Studied radical-induced cross-linking of myosin from white and dark muscle fibers. TARGET AUDIENCES: Meat processors; scientists who work with muscle foods. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results from this study show that water-binding by proteins, entrapping by myofibrils and myofilaments, and imbibing by muscle during marination are critically influenced by the oxidative state of meat. Experiments under artificially created oxidative stress conditions with hydroxyl radicals, as well as under in situ conditions with oxygen-enriched atmosphere (80% O2/20% CO2), on both intact and minced muscle tissues produced consistent evidence that mild oxidation promotes hydration of salted and non-salted marinades. Electron microscopy and light microscopy of stained muscle tissue show that the canals generated between muscle fibers (cells) from oxidative stress serve as the mechanism of water diffusion and hydration in meat. However, the bulk of the absorbed moisture is lost upon cooking. This is explained by the poor protein-water interaction and swelling of myofibrils as shown by phase contrast microscopy. The incongruous effects of protein oxidation on hydration and water holding capacity appear to stem from the radical modification of amino acid side chain groups and the resulting formation of carbonyl and disulfide derivatives. Moreover, the structural changes in myosin is a main factor invovled. The lost ability of myosin head to effectively bind with pyrophosphate leads to the desensitization of actomyosin to magnesium pyrophosphate, therefore, a reduced fiber swelling potential during marination. Further experiments of hydroxyl radical stress of fresh meat and myofibrils in different ionic strength conditions (0.15, 0.45, 0.60 M NaCl), which mimic no-salt, low-salt, and regular-salt meat processing, reveal more extensive protein structural modifications at increasing ionic strengths. Results show that oxidatively stressed myofibrillar proteins at high salt concentrations are favorable substrates for microbial transglutaminase (which is an excellent cross-linking agent for structured meat such as boneless hams). Overall, the findings from this project, which are reported in 11 refereed journal publications, contribute to the understanding of the physicochemical mechanisms of water binding, hydration, and retention as related to protein oxidation. The practical significance is that meat processors can use the information to tailor the specific product formulation and processing, based on the quality (oxidative status) of the raw meat materials, to produce nutritious and consistently palatable meat products.
Publications
- Li, C., Xiong, Y.L., and Chen, J. 2012. Oxidation-induced unfolding facilitates myosin cross-linking by microbial transglutaminase. Journal of Agricultural and Food Chemistry 60:8020-8027.
- Xiong, Y.L. 2012. Protein oxidation in meat processing: mechanism and implications. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 068-01).
- Xiong, Y.L., Li, C., and Liu, Z. 2012. Oxidation desensitizes actomyosin to pyrophosphate-induced dissociation but facilitates myosin cross-linking by microbial transglutaminase. 58th International Congress of Meat Science and Technology.
- Li, C., Xiong, Y.L., and Chen, J. 2012. Protein oxidation at different salt concentrations affects the cross-linking and gelation of pork myofibrillar proteins catalyzed by microbial transglutaminase. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 193-139).
- Delles, R.M. and Xiong, Y.L. 2012. Antioxidant supplementation minimizes the negative impact of dietary oxidized oil on chicken broiler meat quality through promoting antioxidant enzyme activity. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 277-03).
- Liu, C. and Xiong, Y.L. 2012. Variations in the pattern of transglutaminase-induced cross-linking between chicken myosin isoforms due to muscle fiber types. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 277-11).
|
Progress 01/15/11 to 01/14/12
Outputs
OUTPUTS: In 2011, four graduate students (3 Ph.D., 1 M.S.) participated in this project. Progressive results were summarized in two refereed journal articles and in four abstracts presented at the 2011 Institute of Food Technologists (IFT) annual meeting in New Orleans. One of the abstracts received the Third-place prize award at the graduate paper competition of Muscle Foods Division of IFT. One graduate student who worked on this project completed his M.S. degree with a written thesis. In addition, an update of the research progress was presented at the 2011 NRI (NIFA) Project Directors (PD) annual meeting held in conjunction with the annual IFT conference. The PDs' meeting provided a unique forum for the interaction and idea exchange among researchers and clienteles representing food companies, government agencies, consumer groups, and other universities to share major discoveries from this research project. In 2011, the PD visited a research lab in a university in China that was also studying meat protein oxidation. One Ph.D. student from that lab who was working on a related project joined the University of Kentucky as a visiting student to conduct collaborative research. PARTICIPANTS: Y.L. Xiong, Project Director, directed the project and provided training for graduate students; Z. Liu (Ph.D. student), R. Delles (Ph.D. student), C. Li (Ph.D. student), and C. Liu (M.S. student) participated in the project; A.D. True, Research Specialist, assisted graduate students in this work through technical support. TARGET AUDIENCES: Meat processors; scientists who work with muscle foods. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Two experiments were conducted. In experiment 1, pork longissimus muscle samples were subjected to the following three marination conditions: A) oxidation (40 min) in hydroxyl radical-generating solutions (HRGS: 10 uM FeCl3/100 uM ascorbate with 5 or 20 mM H2O2, pH 6.2) containing 0.1 M NaCl, then marination (40 min) in 0.6 M NaCl with 15 mM pyrophosphate (PP); B) simultaneous oxidation/marination (40 min) in the HRGS containing 0.6 M NaCl and 15 mM PP; or C) same as B except that PP was omitted. Protein oxidation, measured by the carbonyl and tryptophan fluorescence changes, enhanced hydration but increased cooking loss of meat. Light microscopy revealed a dense muscle structure characterized by swollen fibers and reduced intercellular spacing in intermediately oxidized muscle samples marinated with 0.6 M NaCl and 15 mM PP. However, oxidized fibers were more susceptible to transverse shrinkage upon cooking than non-oxidized fibers, which was supported by the dynamic ultrastructural changes in myofibrils observed using phase contrast microscopy. These findings provide a further understanding of the complex impact of oxidation on meat hydration and water-binding. In experiment 2, myofibrillar proteins (PM) isolated from postrigor chicken Pectoralis major (predominantly white) and Gastrocnemius (predominantly red), were subjected to a hydroxyl radical (OH)-oxidizing system (10 uM FeCl3, 0.1 mM ascorbate, with 5, 10, or 20 mM H2O2) at pH 6.2, 4C for 18 h. Nonoxidized (control) and oxidized MPs were analyzed for sulfhydryls, disulfides, solubility, aggregation, and particle size (Z-average). Chymotryptic digestion followed by SDS-PAGE was conducted to identify the cross-linking site(s) in protein aggregates. The solubility of control white MP (63%) was higher than that of control red MP (44%). After oxidation with OH at 5 mM H2O2, the solubility decreased due to aggregation by 42% and 25%, for white and red fibers, respectively (P < 0.05). Chemical and electrophoretic analyses indicated H2O2-dose-dependent losses of sulfhydryls and the concomitant formation of disulfides in MP, which were more pronounced in white MP (P < 0.05). Oxidation favored cross-linking of myosin rod or tail in white MP, compared to an equal susceptibility of myosin subfragment-1 or head in red MP. Particles formed from oxidized white MP were 17% larger that those from the oxidized red MP counterpart. The predisposition of white fiber myosin to tail-tail cross-linking compared to tail/head random associations in red fiber myosin might explain the inferior network-forming and gelling properties of red MP during meat processing. Although the impact of the research results is not immediately known, it is expected that meat processors can use the research findings as guide for their product formulation and processing condition design so that an optimal product quality and yield can be achieved.
Publications
- Liu, Z., Xong, Y.L., and Chen, J. 2011. Morphological examinations of oxidatively stressed pork muscle and myofibrils upon salt marination and cooking to elucidate the water-binding potential. Journal of Agricultural and Food Chemistry 59:13026-13034.
- Delles, R.M., Xiong, Y.L., and True, A.D. 2011. Mild protein oxidation enhanced hydration and myofibril swelling capacity of fresh ground pork muscle packaged in high-oxygen atmospheres. Journal of Food Science 76:C760-C767.
- Delles, R.M. and Xiong, Y.L. 2011. The opposing effects of a high-oxygen atmosphere packaging system on hydration (enhanced) and water-holding (reduced) in fresh pork loins. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 152-34).
- Liu, Z., Xiong, Y.L., and Chen, J. 2011. Oxidation desensitizes actomyosin to dissociating pyrophosphate in the presence of magnesium chloride. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 240-06).
- Li, C. and Xiong, Y.L. 2011. Efficacy of microbial tansglutaminase mediated cross-linking of pork myofibrillar proteins as influenced by protein oxidative status. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 240-08).
- Liu, C. and Xiong, Y.L. 2011. Influence of muscle fiber types on oxidation-induced protein cross-linking in chicken myofibrils. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 240-09).
|
Progress 01/15/10 to 01/14/11
Outputs
OUTPUTS: In 2010, four graduate students (2 Ph.D., 2 M.S.) participated in this project. Progressive results were summarized in two refereed journal articles published and in one abstract presented at the 2010 Institute of Food Technologists (IFT) annual meeting in Chicago. The abstract received the first-place prize award at the graduate paper competition of Muscle Foods Division of IFT. One graduate student who worked on this project completed her M.S. degree with a written thesis. In addition, an update of the research progress was presented at the 2010 NRI Project Directors (PD) annual meeting held in conjunction with the annual IFT conference. One journal article resulting from the study was published during this period. The PDs' meeting provided a unique forum for the interaction and idea exchange among researchers and clienteles representing food companies, government agencies, consumer groups, and other universities to share major discoveries from this research project. In 2010, the PD visited a research lab in a university in China that was also studying protein oxidation. One Ph.D. student from that lab who was working on a related project joined the University of Kentucky as a visiting student to conduct collaborative research. PARTICIPANTS: Y.L. Xiong, Project Director, directed the project and provided training for graduate students; Z. Liu (Ph.D. student), C. Liu (M.S. student), and C. Li (Ph.D. student) conducted Experiment 1; R.M. Delles (M.S. student) conducted Experiment 2; A.D. True, Research Specialist, assisted graduate students in this work through technical support. TARGET AUDIENCES: Meat processors; scientists who work with muscle foods. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Two experiments were conducted. In experiment 1, Pork longissimus muscle was oxidized at 4C by mixed 10 μM FeCl3/100 μM ascorbate with 1, 5, 10, 20, 30, 40, or 50 mM H2O2 (pH 6.2). Oxidation with > 1 mM H2O2 for 40 min significantly enhanced (P < 0.05) hydration of muscle samples, while oxidation with 40 and 50 mM H2O2 for 2 min or with 20 mM H2O2 for 40 min caused pronounced declines in water-holding capacity and product yield. The changes coincided with marked increases in the protein carbonyl content, TBARS formation, and cross-linking of both myofibrillar and sarcoplasmic proteins. Dye-tracing tests showed that the enhanced hydration at > 1 mM H2O2 was due to facilitated water diffusion into muscle tissue. This result was strongly corroborated by microscopic images that illustrated enlargements of intercellular spacing, i.e., gaps, in oxidized muscle tissue which served as canals for water diffusion. In experiment 2, boneless pork loin chops (longissimus) were packaged in an oxygen-enriched atmosphere packaging system (MAP: 80% O2/20% CO2), on Styrofoam trays with an air-permeable polyvinylchloride (PVCP) overwrap, or a partial vacuum (60%) packaging system and stored at 2C for 14, 7, and 21 days, respectively. Muscle sample stored in MAP had marked increases (P < 0.05) of TBARS and carbonyls, and a loss in sulfhydryls, indicating lipid and protein oxidation. PVCP and VP showed lesser or negligible effects on these oxidation parameters. On day 4, MAP samples had higher redness (a* value) than PVCP and VP samples. SDS-PAGE revealed major losses of myosin heavy chain (MHC) in MAP and PVCP samples from day 0 to day 4, but in VP samples no significant loss of MHC was noted until day 14. Microscopic images of muscle fiber cross-sections indicated an increase in extracellular spaces in all packaging systems during extended storage, which was most remarkable on day 14 MAP samples. Water-holding capacity decreased significantly (P < 0.10) in muscle stored in MAP but not in PVCP and VP samples. Day 4 and 7 MAP muscles, brine-marinated for 40 and 20 min, respectively, had a greater (P < 0.05) hydration capacity (brine pick-up) than PVCP and VP samples. The results were corroborated by the phase contrast data where extended storage in MAP produced the most extensive myofibril swelling upon brine irrigation. Despite enhanced hydration, MAP muscle samples were least capable of holding moisture upon cooking. The results suggested that enhanced protein oxidation in MAP system when compared with PVCP and VP was responsible for these altered hydration properties of pork loin muscle. Although the impact of the research results is not immediately known, it is expected that meat processors can use the research findings as guide for their product formulation and processing condition design so that an optimal product quality and yield can be achieved.
Publications
- Xiong, Y.L., Blanchard, S.P., Ooizumi, T., and Ma, Y. 2010. Hydroxyl radical and ferryl-generating systems promote gel network formation of myofibrillar protein. J. Food Sci. 75:C215-221.
- Liu, Z., Xiong, Y.L., and Chen, J. 2010. Protein oxidation enhances hydration but suppresses water-holding in porcine longissimus muscle. J. Agric. Food Chem. 58:10697-10704.
- Liu, Z., Xiong, Y.L., and Chen, J. 2010. Protein oxidation enhances hydration but suppress water-holding in porcine longissimus muscle: A possible mode of action. Book of Abstracts. Annual Meeting of the Institute of Food Technologists. (Abst. No. 192-05).
|
Progress 01/15/09 to 01/14/10
Outputs
OUTPUTS: The overall objective of the proposed study is to elucidate the morphological/structural changes in oxidatively stressed myofibrils and in their main constituting proteins, and to understand how such modifications contribute to water-binding and hydration of meat. In 2009, three graduate students and one research associate participated in this project. Progressive results summarized in two abstracts were presented at the 2009 Institute of Food Technologists (IFT) annual meeting in Anaheim, California. In addition, an update of the research progress was presented at the 2009 NRI Project Director (PD) meeting in conjunction with the annual IFT conference. A significant output is the publication of one journal article resulting from the study. The PDs meeting provided a unique forum for the interaction and idea exchange among delegates and audiences representing food companies, government agencies, consumer groups, and other universities to share major discoveries from this research project. In 2009, the PD visited a research lab at a university in China that was also studying protein oxidation. A mutual agreement for collaboration was reached. PARTICIPANTS: This project, while exploring the fundamental mechanism for oxidation-induced changes in water-binding by myofibrils in fresh meat, offers a unique opportunity to train graduate students. Y.L. Xiong, Project Director, directed the whole project and provided training for graduate students. Z. Liu (Ph.D. student) and C. Liu (M.S. student) conducted Experiment 1. R.M. Delles (M.S. student) conducted Experiment 2. A.D. True, Research Specialist, played an important role by assisting participating graduate students with their work. TARGET AUDIENCES: Meat processors; scientists who work with muscle foods. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Two experiments were conducted. In experiment 1 (completed), myofibrils isolated from fresh pork longissimus muscle were exposed to a hydroxyl radical-generating system (0.01 mM iron chloride, 0.1 mM asorbate, 1 mM hydrogen peroxide) for up to 12 h at 2 C. In experiment 2 (in progress), myofibrils were extracted from commercial fresh ground pork stored at 2 C in an oxygen enriched packaging system (MAP, with 80% oxygen and 20% carbon dioxide). Packaging with polyvinylchloride (PVC) wrap was used as control for comparison. Oxidation-induced changes in the hydration properties of myofibrils was investigated by irrigation of myofibrils with brines (0.1-0.8 M NaCl, 10 mM pyrophosphate, 2 mM MgCl2, pH 6.0). Morphological changes and structural alterations, including the dissolution of myofibrils and the removal of myosin, in oxidation-stressed and control (nonoxidized) myofibril samples during hydration were examined by phase contrast microscopy. Results from Experiment 1 showed that irrigation with >0.4 M NaCl produced marked swelling of nonoxidized myofibrils and concomitant dissolution of the myosin filaments from both sides of the A-band. However, such structural changes were somewhat suppressed in oxidized myofibrils. Oxidized myofibrils had a reduced myosin and actin extractability and lost some contractability due to disulfide bond formation between myofilaments. Results from Experiment 2 demonstrated that drip loss increased during storage of all meat samples and there was no difference due to packaging conditions. The A-bands in myofibrils disintegrated more extensively upon brine irrigation at >0.4 M NaCl for fresh meat samples than for stored samples (7 days for PVC; 14 days for MAP) at 2 C, due to oxidation of both proteins (carbonyls) and lipids (TBARS). These findings indicated that reduced water-holding capacity of fresh pork stored in MAP or exposed to an oxidizing environment was due to reduced structural expandability and protein extractability of myofibrils. Oxidative modification of proteins was implicated. Although the impact of the research results is not immediately known, it is expected that meat processors can use the research findings as guide for their product formulation and processing condition design so that an optimal product quality and yield can be achieved.
Publications
- Xiong, Y.L., Park, D., and Ooizumi, T. 2009. Variation in the cross-linking pattern of porcine myofibrillar protein exposed to three oxidative environments. Journal of Agricultural and Food Chemistry 57:153-159.
- Ma, Y.Y., Xiong, Y.L., J. Zhai, H. Zhu, and Dziubla, T. 2010. Fractionation and evaluation of radical-scavenging peptides from in vitro digests of buckwheat protein. Food Chemistry 118:582-588.
- Liu, Z., Xiong, Y.L., and Chen, J. 2010. Identification of restricting factors that inhibit swelling of oxidized myofibrils during brine irrigation. Journal of Agricultural and Food Chemistry 57:10999-11007.
|
Progress 01/15/08 to 01/14/09
Outputs
OUTPUTS: The overall objective of the proposed study is to elucidate the morphological/structural changes in oxidatively stressed myofibrils and in their main constituting proteins, and to understand how such modifications contribute to water-binding and hydration of meat. Two graduate students (1 Ph.D. and 1 M.S.) and one research associate are assigned to this project. All three are actively engaged in the study, and the two graduate students have obtained enough preliminary data that are summarized in two separate abstracts to be presented at the 2009 Institute of Food Technologists (IFT) annual meeting in Anaheim, California. In addition, an update of the research progress was presented at the 2008 NRI Project Director meeting in conjunction with the annual IFT conference in June at New Orleans. The PDs meeting provided a unique forum for the interaction and idea exchange among delegates and audiences representing food companies, government agencies, consumer groups, and other universities to share major discoveries from this research project. As a part of outreach and promotion of the research, the PD visited two overseas collaborative labs (Japan, China) where he presented seminars and talks to over 200 students and faculty on subjects related to this NRI project. Resulting from the international collaboration, 2-3 outstanding international graduate students have been or will be recruited to the University of Kentucky. PARTICIPANTS: This project, while exploring the fundamental mechanism for oxidation-induced changes in water-binding by myofibrils in fresh meat, offers a unique opportunity to train graduate students. Youling L. Xiong, Project Director, directed the whole project and provided training for graduate students. Zelong Liu, Ph.D. student, conducted Experiment 1. Rebecca M. Delles, M.S. student, conducted Experiment 2. Alma D. True, Research Specialist, played an important role by assisting both participating graduate students with their work. TARGET AUDIENCES: Meat processors; scientists who work with muscle foods. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Two experiments were conducted. In experiment 1, myofibrils isolated from fresh pork longissimus muscle were exposed to a hydroxyl radical-generating system (0.01 mM iron chloride, 0.1 mM asorbate, 1 mM hydrogen peroxide) for 0, 1, 6, and 12 h at 2 C. In experiment 2, myofibrils were extracted from commercial fresh ground pork stored at 2 C in an oxygen enriched packaging system (MAP, with 80% oxygen and 20% carbon dioxide). Packaging with polyvinylchloride (PVC) wrap was used as control for comparison. The impact of protein oxidation on the hydration properties of myofibrils was investigated by irrigation of myofibrils with brines (0.1-0.8 M NaCl, 10 mM pyrophosphate, 2 mM MgCl2, pH 6.0). Dynamic morphological changes and structural alterations, including the dissolution of myofibrils and the removal of myosin, in oxidation-stressed and control (nonoxidized) myofibril samples during hydration were examined by phase contrast microscopy and SDS-PAGE. Preliminary results from Experiment 1 showed that irrigation with >0.4 M NaCl produced marked swelling of myofibrils and concomitant dissolution of the myosin filaments from both sides of the A-band. However, the rate and extent of such structural changes were notably less in oxidized myofibrils than in control samples. Oxidized myofibrils also tended to retain more A-band remnants. The oxidized samples had a reduced protein extractability than control samples, including that of myosin, the most tractable protein of all. The extractability difference gradually diminished at increasing NaCl concentrations until 0.8 M NaCl where control and oxidized samples had identical protein solubility. Moreover, the M-line and C-protein in control myofibrils appeared to be more extractable compared with oxidized myofibrils. Preliminary results from Experiment 2 demonstrated that drip loss increased during storage of all meat samples and there was no difference due to packaging conditions. Brine irrigation at >0.4 M NaCl caused major structural changes in myofibrils, and myofibril A-bands disintegrated more extensively in 0-day samples than in 7-day (PVC) and 14-day (MAP) samples stored at 2 C. TBARS (lipid oxidation) increased exponentially during storage, and the protein carbonyl (protein oxidation) content also increased during storage in both packaging systems. The preliminary results indicated that reduced water binding ability of fresh pork stored in MAP or exposed to an oxidizing environment was due to reduced structural expandability and protein extractability of myofibrils, which were caused by oxidative modification of proteins. These initial findings will be validated in repeated experiment trials, after which final conclusions will be reached. Although the impact of the research results is not immediately clear, it is expected that meat processors can use the research findings to guide their product formulation and processing condition design for an optimized product quality and yield.
Publications
- No publications reported this period
|
|