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Caspase-3 does not enhance in vitro bovine myofibril degradation by Μu-calpain
468
Abstracts
objective of this study was to identify the relationships between consumer preference and the FA composition. Materials and methods: Strip loins (n = 4; WBSF value ≤ 3.4 kg) of 10 categories USDA Prime (PR), High Choice (HC; upper 1/3 choice), Low Choice (LC; lower 1/3 Choice), Select (SE), Standard (ST), USDA High Choice and Select from Holstein cattle (HOLTC and HOLSEL, respectively), Australian Wagyu (AUWA), American Wagyu (AMWA), and Grass-finished (GR) were selected (all aged 28 days, except 48 days for GR). Strip loins were fabricated into 2.5-cm thick steaks and further processed into 5 × 5 cm pieces. Each steak was cooked on an electric clamshell grill for 5 min at a grill surface temperature of 225 °C. Consumers were served one sample from each treatment. Each sample was evaluated for tenderness, juiciness, flavor and overall liking on a 10-cm, verbally anchored line-scale. Lipids were extracted from raw steaks, fractionated into NL and PL, derivatized to FAME and determined by gas chromatography. Principle component analysis (PCA) on consumer palatability rankings was performed, which resulted in two PCs – PC1 and PC2 explaining 98% and 2% of variances, respectively. PC1 and PC2 were used to determine treatment scores, which were subsequently correlated with lipid variables. The treatment PC scores and variable correlation coefficients were plotted together (x coordinate = PC1 scores or correlation coefficients; y coordinate = PC2 scores or correlation coefficients) to evaluate relationships among variables and treatment rankings. Results: Tenderness, juiciness, flavor and overall palatability were all positively correlated to PC1 (r = 0.98 to 0.99; P b 0.001) and plotted near PR, AMWA and AUWA. Treatment PR, AMWA and AUWA were highly scored by PC1, compared to lower PC1 scores of ST, SE, HOLSEL and GR. However, AUWA and GR (0.58 and 1.00, respectively) had similar PC2 scores. Percentage of MUFA was more greatly related to PR, AMWA and AUWA. Percentage of PUFA was more closely related to SE, HOLSEL, ST and GR treatments. Fatty acids from NL were related to PR, AMWA and AUWA, except arachadonic acid (C20:4n6). The MUFA and SFA from PL were located closely to PR, AMWA and AUWA. Conclusion: The variances of consumer preference were primarily explained by one PC and can be used to explain the relationships of lipid fraction among ten treatments. These results indicate that FA composition of NL and PL were highly correlated to consumer preference, including beef flavor. Keywords: Beef quality, Flavor, Lipid, Principal component analysis, Strip loin steaks doi:10.1016/j.meatsci.2013.07.097
60 Caspase-3 does not enhance in vitro bovine myofibril degradation by Μu-calpain D. Mohrhauser⁎, S. Kern, K. Underwood, A. Weaver, Department of Animal Science, South Dakota State University, Brookings, United States Objectives: Tenderness is a key component of palatability which influences consumers' perception of meat quality. There are a variety of factors that contribute to the tenderness of beef carcasses including postmortem proteolysis. A more complete understanding of this biological mechanism regulating tenderness is needed to ensure consistently tender beef. Numerous reports indicate μ-calpain is primarily responsible for the degradation of proteins postmortem. Meanwhile, it has been shown that caspase-3 can cleave calpastatin, the inhibitor of μ-calpain. Therefore, the objective of this study was to determine if in vitro degradation of calpastatin by caspase-3 can enhance the postmortem breakdown of myofibrillar proteins by μ-calpain. Materials and methods: Bovine semitendinosus muscles were excised from two carcasses 20 min postmortem. Muscle strips were dissected
from the semitendinosus, restrained to maintain length, and placed in a neutral buffer containing protease inhibitors. Upon rigor completion, myofibrils were isolated from each strip and sarcomere length was determined. Samples with similar sarcomere lengths were selected to minimize the effect of sarcomere length on proteolysis. Myofibrils were then incubated at 22°C with either μ-calpain, μ-calpain + calpastatin, μ-calpain + caspase-3 + calpastatin, or caspase-3 +calpastatin for 0.25, 1, 3, 24, 48, or 72 h at a pH of 6.8. Proteolysis of troponin T (TnT) and calpastatin was evaluated using SDS-PAGE and western blotting techniques. Results: Analysis of western blots confirmed significant degradation of calpastatin by caspase-3. Additionally, western blots revealed that intact calpastatin disappeared rapidly as a result of digestion by μcalpain. While caspase-3 did not significantly degrade TnT, all μ-calpain digestion treatments resulted in substantial TnT breakdown. Degradation of TnT did not differ between the μ-calpain + calpastatin and μ-calpain + caspase-3 + calpastatin digestions. Conclusion: Results of this study indicate that caspase-3 cleavage of calpastatin does not enhance in vitro degradation of troponin T by μ-calpain. Keywords: Calpastatin, Caspase, Proteolysis, Tenderness, μ–Calpain doi:10.1016/j.meatsci.2013.07.098
61 Influence of an antioxidant on the shelf-life and quality of ground beef stored in a high-oxygen master package prior to display J. Martin⁎, C. Moon, T.R. Brown, P.R. Broadway, T. Dinh, J.C. Brooks, Animal and Food Sciences, Texas Tech University, Lubbock, United States Objectives: Master packaging allows for the utilization of caseready packaging while balancing the consumers' preference for overwrapped fresh meat. Limited information regarding the use of high-oxygen (HI-OX) master packaging is available; furthermore, the efficacy of an antioxidant in this system is unknown. Therefore, we aimed to evaluate the effects of HI-OX master packaging on the shelflife, color stability, and quality traits of overwrapped ground beef treated with a natural antioxidant blend. Materials and methods: Finely ground beef chubs (80:20; lean: fat) were obtained from a commercial processing facility. At 7 d postprocessing, chubs were removed from storage, finely ground, and portioned onto black expanded polystyrene trays. After portioning, one-half of the trays were randomly assigned to an antioxidant application (AOX) and one-half were left untreated (CON). AOX trays were topically sprayed with a 10% solution of a natural antioxidant blend applied at a level not to exceed 0.494% of the total package weight. All trays were overwrapped using a micro-perforated polyvinyl chloride film before placement into high-barrier master bags. Residual atmosphere was evacuated from the bag prior to flushing with a premixed 80% O2/20% CO2 atmosphere and sealing. Master packs were stored at 0 to 2 °C for 5, 8, 10, 12, or 15 d postpackaging prior to lighted retail display for 5 d. Myoglobin forms (as calculated by spectrophotometric reflectance data), pH, metmyoglobin reducing activity, thiobarbituric acid reactive substances (TBARs), and microbiological activity were assessed after 0, 3, and 5 d of retail display while instrument color (L*, a* b*, and saturation) were measured daily. Objective color and palatability characteristics were evaluated by trained sensory panelists daily (color) or after 0, 3, and 5 d of display (palatability). Results: As expected, all subjective and objective color measurements indicated that ground beef color stability decreased (P b 0.05) as storage and display length increased. Antioxidant application generally resulted in a delayed loss of lean redness when compared
Abstracts
objective of this study was to identify the relationships between consumer preference and the FA composition. Materials and methods: Strip loins (n = 4; WBSF value ≤ 3.4 kg) of 10 categories USDA Prime (PR), High Choice (HC; upper 1/3 choice), Low Choice (LC; lower 1/3 Choice), Select (SE), Standard (ST), USDA High Choice and Select from Holstein cattle (HOLTC and HOLSEL, respectively), Australian Wagyu (AUWA), American Wagyu (AMWA), and Grass-finished (GR) were selected (all aged 28 days, except 48 days for GR). Strip loins were fabricated into 2.5-cm thick steaks and further processed into 5 × 5 cm pieces. Each steak was cooked on an electric clamshell grill for 5 min at a grill surface temperature of 225 °C. Consumers were served one sample from each treatment. Each sample was evaluated for tenderness, juiciness, flavor and overall liking on a 10-cm, verbally anchored line-scale. Lipids were extracted from raw steaks, fractionated into NL and PL, derivatized to FAME and determined by gas chromatography. Principle component analysis (PCA) on consumer palatability rankings was performed, which resulted in two PCs – PC1 and PC2 explaining 98% and 2% of variances, respectively. PC1 and PC2 were used to determine treatment scores, which were subsequently correlated with lipid variables. The treatment PC scores and variable correlation coefficients were plotted together (x coordinate = PC1 scores or correlation coefficients; y coordinate = PC2 scores or correlation coefficients) to evaluate relationships among variables and treatment rankings. Results: Tenderness, juiciness, flavor and overall palatability were all positively correlated to PC1 (r = 0.98 to 0.99; P b 0.001) and plotted near PR, AMWA and AUWA. Treatment PR, AMWA and AUWA were highly scored by PC1, compared to lower PC1 scores of ST, SE, HOLSEL and GR. However, AUWA and GR (0.58 and 1.00, respectively) had similar PC2 scores. Percentage of MUFA was more greatly related to PR, AMWA and AUWA. Percentage of PUFA was more closely related to SE, HOLSEL, ST and GR treatments. Fatty acids from NL were related to PR, AMWA and AUWA, except arachadonic acid (C20:4n6). The MUFA and SFA from PL were located closely to PR, AMWA and AUWA. Conclusion: The variances of consumer preference were primarily explained by one PC and can be used to explain the relationships of lipid fraction among ten treatments. These results indicate that FA composition of NL and PL were highly correlated to consumer preference, including beef flavor. Keywords: Beef quality, Flavor, Lipid, Principal component analysis, Strip loin steaks doi:10.1016/j.meatsci.2013.07.097
60 Caspase-3 does not enhance in vitro bovine myofibril degradation by Μu-calpain D. Mohrhauser⁎, S. Kern, K. Underwood, A. Weaver, Department of Animal Science, South Dakota State University, Brookings, United States Objectives: Tenderness is a key component of palatability which influences consumers' perception of meat quality. There are a variety of factors that contribute to the tenderness of beef carcasses including postmortem proteolysis. A more complete understanding of this biological mechanism regulating tenderness is needed to ensure consistently tender beef. Numerous reports indicate μ-calpain is primarily responsible for the degradation of proteins postmortem. Meanwhile, it has been shown that caspase-3 can cleave calpastatin, the inhibitor of μ-calpain. Therefore, the objective of this study was to determine if in vitro degradation of calpastatin by caspase-3 can enhance the postmortem breakdown of myofibrillar proteins by μ-calpain. Materials and methods: Bovine semitendinosus muscles were excised from two carcasses 20 min postmortem. Muscle strips were dissected
from the semitendinosus, restrained to maintain length, and placed in a neutral buffer containing protease inhibitors. Upon rigor completion, myofibrils were isolated from each strip and sarcomere length was determined. Samples with similar sarcomere lengths were selected to minimize the effect of sarcomere length on proteolysis. Myofibrils were then incubated at 22°C with either μ-calpain, μ-calpain + calpastatin, μ-calpain + caspase-3 + calpastatin, or caspase-3 +calpastatin for 0.25, 1, 3, 24, 48, or 72 h at a pH of 6.8. Proteolysis of troponin T (TnT) and calpastatin was evaluated using SDS-PAGE and western blotting techniques. Results: Analysis of western blots confirmed significant degradation of calpastatin by caspase-3. Additionally, western blots revealed that intact calpastatin disappeared rapidly as a result of digestion by μcalpain. While caspase-3 did not significantly degrade TnT, all μ-calpain digestion treatments resulted in substantial TnT breakdown. Degradation of TnT did not differ between the μ-calpain + calpastatin and μ-calpain + caspase-3 + calpastatin digestions. Conclusion: Results of this study indicate that caspase-3 cleavage of calpastatin does not enhance in vitro degradation of troponin T by μ-calpain. Keywords: Calpastatin, Caspase, Proteolysis, Tenderness, μ–Calpain doi:10.1016/j.meatsci.2013.07.098
61 Influence of an antioxidant on the shelf-life and quality of ground beef stored in a high-oxygen master package prior to display J. Martin⁎, C. Moon, T.R. Brown, P.R. Broadway, T. Dinh, J.C. Brooks, Animal and Food Sciences, Texas Tech University, Lubbock, United States Objectives: Master packaging allows for the utilization of caseready packaging while balancing the consumers' preference for overwrapped fresh meat. Limited information regarding the use of high-oxygen (HI-OX) master packaging is available; furthermore, the efficacy of an antioxidant in this system is unknown. Therefore, we aimed to evaluate the effects of HI-OX master packaging on the shelflife, color stability, and quality traits of overwrapped ground beef treated with a natural antioxidant blend. Materials and methods: Finely ground beef chubs (80:20; lean: fat) were obtained from a commercial processing facility. At 7 d postprocessing, chubs were removed from storage, finely ground, and portioned onto black expanded polystyrene trays. After portioning, one-half of the trays were randomly assigned to an antioxidant application (AOX) and one-half were left untreated (CON). AOX trays were topically sprayed with a 10% solution of a natural antioxidant blend applied at a level not to exceed 0.494% of the total package weight. All trays were overwrapped using a micro-perforated polyvinyl chloride film before placement into high-barrier master bags. Residual atmosphere was evacuated from the bag prior to flushing with a premixed 80% O2/20% CO2 atmosphere and sealing. Master packs were stored at 0 to 2 °C for 5, 8, 10, 12, or 15 d postpackaging prior to lighted retail display for 5 d. Myoglobin forms (as calculated by spectrophotometric reflectance data), pH, metmyoglobin reducing activity, thiobarbituric acid reactive substances (TBARs), and microbiological activity were assessed after 0, 3, and 5 d of retail display while instrument color (L*, a* b*, and saturation) were measured daily. Objective color and palatability characteristics were evaluated by trained sensory panelists daily (color) or after 0, 3, and 5 d of display (palatability). Results: As expected, all subjective and objective color measurements indicated that ground beef color stability decreased (P b 0.05) as storage and display length increased. Antioxidant application generally resulted in a delayed loss of lean redness when compared