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Biomedical subjects

D L Fletcher

Publications and source records attributed to D L Fletcher.

At least 19 recordsLinked to original sources

Effects of raw broiler breast meat color variation on marination and cooked meat quality.

Three replicate trials were conducted to determine the effect of raw broiler breast meat color on marinated and cooked meat quality. In each trial, 90 fillets were collected from a commercial processing plant based on lightness (L*) values of breast meat as follows: light, L* > 53; normal, 48 < L* < 51; and, dark, L* < 46. For each fillet the color, pH, and weight were determined, and the fillets were marinated in three lots of 10 fillets from each color group (20% wt:wt of 5% salt and 2.5% sodium tripolyphosphate in a vacuum tumbler). Marination uptake was determined; the samples were held for 24 h at 2 C, and color, pH, and weight again were determined. Next, the samples were cooked, and the meat was subjected to color, pH, cooked yield, shear force, and moisture analyses. Results showed that absolute color values changed with marination and cooking, but that L* and pH differences by color group were maintained through marination and cooking. There were also significant differences in marinade absorption, cooked yield, and shear value, particularly among the extremes of light and dark meats. There was no significant difference in final cooked meat moisture. As expected, there were significant negative correlations between meat lightness and pH; however, raw muscle pH was not correlated to final product moisture or shear but was positively correlated to cooked meat yield and negatively correlated to marinade absorption. These results indicate that the pH variation associated with extreme raw breast meat color variation can affect breast meat marination and cooked meat quality.

Animals↗

The relationship between raw broiler breast meat color and composition.

Experiments were conducted to compare the chemical composition of broiler breast meat that was naturally lighter than normal, normal, and darker than normal. In each of three separate replicated trials (wk), fillets were obtained from three commercial processing plants. Approximately 25 fillets of each color group were selected based on International Commission on Illumination (CIE) lightness values as follows: lighter than normal (L* > 53), normal (48 < L* < 51), and darker than normal (L* < 46). The fillets from each replicate, plant, and color group were ground and mixed together, and samples for the 27 treatment groups subjected to color, pH, and chemical analyses (protein, ash, moisture, total lipids, iron, glycogen, and fatty acids profile). The whole fillets had significantly different color values for the three color groups at 0 and 24 h prior to grinding. Of the ground meat samples, there were significant treatment and plant differences in composition. There were no color treatment effects on moisture, lipid, glycogen, iron, ash, or fatty acid ratios. Meat from the light group had significantly lower protein values than the normal or dark meat and lower ash than the dark group. The light group also had significantly higher levels of C16:1 and lower levels of C18:0 and C20:4 fatty acids than the dark group. Among the three plants, there were significant effects for breast meat color and composition. Results indicated that, although plant had more effect on composition, differences by color group might indicate that extreme variation in color may be due to long-term genetic factors as well as short-term antemortem stress.

Animals↗

The effect of holding temperature on live shrink, processing yield, and breast meat quality of broiler chickens.

The effects of antemortem holding temperatures on live shrink, processing yields, and breast meat quality of broiler chickens were evaluated. A total of 462 broilers was reared to 45 d of age using conventional husbandry practices, removed from feed and water, and cooped 12 h prior to slaughter. During the 12-h feed withdrawal and holding time, the birds were held at 25, 29.5, or 34 C. Birds were individually weighed at cooping, prior to slaughter, and during processing to determine live shrink and processed carcass yields. The breast meat was removed at 2 or 24 h postmortem and was used to determine hot and cold boned meat pH, R-value, sarcomere length, meat color (lightness, redness, and yellowness), cooked yield, and shear value. The birds held at 34 C showed the significantly greatest live shrink, 5.7%, compared to those held at 29.5 or 25 C with 3.9 and 3.2% shrink, respectively. Birds held at 34 C exhibited significantly lower processed carcass yields based on initial catch weight, but when calculated using postshrink weights, there were no significant differences between treatment groups. For breast meat harvested at 2 h postmortem, the birds held at 25 C had higher R-values, redness, and yellowness values and lower cooked meat yield and shear values. For breast meat harvested at 24 h postmortem, the birds held at 25 C had higher pH, R-values, and redness. These results support earlier reports that holding conditions may dramatically effect live bird shrink and apparent yields (based on calculation denominator) but have relatively little effect on subsequent breast meat quality, regardless of postmortem deboning time.

Animals↗

The effect of broiler breast meat color on pH, moisture, water-holding capacity, and emulsification capacity.

The relationship between broiler breast meat color and pH, moisture content, water-holding capacity (WHC), and emulsification capacity (EC) was investigated. In each of three replicate trials, fillets were collected from three different commercial processing plants according to breast meat lightness (L*) values as follows: lighter than normal (light, L* > 53), normal (48 < L* < 53), and darker than normal (dark, L* < 46). Color values of lightness (L*), redness (a*), and yellowness (b*) were measured at 0 and 24 h after collection. Fillets were then ground and homogenized prior to determining color, pH, moisture, WHC, and EC of the ground meat. There was a significant difference among the three color groups (light, normal, and dark) in L*, a*, pH, WHC, and EC. The L* values of whole raw breast fillets had significant negative correlation coefficients with ground meat EC (-0.9237), pH (-0.9610), and a* (-0.6540). Emulsification capacity had significant positive correlations with pH (0.9572) and water-holding capacity (0.7080). WHC had significant correlations with a* (0.8143), moisture (-0.7647), and pH (0.7963). Lighter-than-normal meat was associated with low pH, high moisture, low EC, and low WHC. These results indicate that wide differences in raw breast meat color exist and that these differences may be used by poultry further processors as an indicator of fillets with altered functional properties.

Animals↗

Reactions of laying hens and broilers to different gases used for stunning poultry.

Observations of the behavioral reactions of laying hens and broilers to different gas stunning atmospheres were made. Sixty Hy-Line W-36 hens and 60 market-weight commercial broilers were placed individually into a plexiglass gas stunning unit and exposed to one of six gas atmospheres: air, concentrations of 30, 45, or 60% CO2 in air, a mixture of 70% argon and 30% CO2, and 100% argon. Video records were made during each test, which lasted until the subject became unconscious or for 2 min in the air treatment. Behavior in the 100% argon atmosphere resembled that in air, until birds became impaired by anoxia. All treatments involving CO2, including 70% argon/30% CO2, caused deep breathing and head shaking. The concentration of CO2 in air in the range tested did not affect the tendency to perform different actions, except that birds in 60% CO2 were more likely to exhibit a convulsive flip at the point of collapse. Chickens in 70% argon/30% CO2 tended to demonstrate less sedation and performed more sudden efforts to regain balance during tests than did chickens in CO2 mixtures in air and were more likely to perform a convulsive flip. Deep breathing and head shaking have been suggested as being indicative of respiratory distress and aversive reaction to CO2. The data in this study are consistent with the possibility that head shaking is an alerting response functioning to promote arousal in the face of reduced sensibility during exposure to CO2-enriched atmospheres. Nonetheless, if the view is correct that deep breathing and head shaking indicate distress, the 70% argon/30% CO2 gas mixture was at least as distressing as even 60% CO2 in air. The relative prevalence of sudden efforts to regain balance in 70% argon/30% CO2 suggest that this gas mixture might cause even more distress than up to 60% CO2 in air.

Abattoirs↗

The relationship of raw broiler breast meat color and pH to cooked meat color and pH.

Three replicate trials were conducted to determine the influence of raw breast meat color and pH on subsequent cooked meat color and pH. In each trial, approximately 50 breast fillets were obtained from a commercial processing plant based on being either normal, lighter than normal, or darker than normal. Color (L* = lightness, a* = redness, and b* = yellowness) of each fillet was determined in triplicate on the underside surface of the fillet (to avoid scalding effects), and the pH was determined on a tissue sample removed from the posterior portion of each fillet. Fillets were then cooked in steam at 98 C for 20 min and cooled to room temperature, and a second sample was removed from the posterior section for cooked meat pH. Cooked meat color was measured on an exposed surface, to avoid cooking-related discoloration. The data were subjected to linear regression analysis to determine the relationship between raw and cooked values. Results indicated a significant linear relationship between raw and cooked values for each color parameter as well as pH. Model R2 values were 0.43, 0.40, 0.64, and 0.78 for L*, a*, b*, and pH, respectively. There were also significant linear relationships between raw meat L* and raw muscle pH (R2 = 0.59) as well as cooked meat L* and raw meat pH (R2 = 0.36). These results indicate that raw breast meat color and pH affect cooked breast meat color and pH but that cooking reduces the degree of color variation. Moreover, cooked meat lightness is more closely associated with raw breast meat pH than with cooked meat pH.

Analysis of Variance↗

Slaughter technology.

Slaughter technology has changed dramatically over the past 30 yr. Methods of handling the live animal immediately prior to slaughter, methods of stunning, killing, early postmortem handling, and carcass treatment have all seen technological advancement. The primary factors driving changes in these technical aspects of poultry slaughter have been to increase efficiency of commercial operations and the improvement of carcass and meat quality. Paralleling these developments, changes in social and legal expectations regarding animal well-being have also had an impact on these technical developments. The purpose of this symposium is to review the developments of these changing technologies and how they are being implemented in commercial operations. Special emphasis is on the technologies of electrical stunning, gas stunning, and electrical stimulation and their effects on carcass and meat quality.

Abattoirs↗

The effects of antemortem electrical stunning and postmortem electrical stimulation on biochemical and textural properties of broiler breast meat.

Experiments were conducted to determine the combined effects of antemortem electrical stunning (STUN) and postmortem electrical stimulation (STIM) on breast muscle rigor development and meat quality attributes. Birds were either unstunned, stunned with low voltage (LV), or stunned with high current (HC) prior to conventional killing. Immediately after exsanguination, birds were either unstimulated, or were subjected to electrical stimulation with 12 1s on/1s off pulses of 440 V AC and allowed to bleed for 90 s to determine the effect of treatment on blood loss. Breast fillets (Pectoralis major) were removed from carcasses immediately after evisceration (0.25 h) or after aging in a static ice-water slush for 1 or 2 h, and analyzed for muscle pH, R-value (ratio of inosine to adenosine nucleotides), and sarcomere length. Raw breast meat color (CIELAB), cook loss, and shear values were determined on samples held at 2 C for 24 h. Results showed both STUN and STIM significantly affected blood loss, pH, R-value, sarcomere length, color, and shear, and there were significant STUN by STIM interactions. Blood loss was significantly lower for the HC STUN and all the STIM treatments. STIM at 440 V resulted in accelerated rigor development as measured by pH, R-value, and sarcomere length, similar to the unstunned or LV STUN samples, but different from the HC STUN birds. These results indicate that electrical stimulation may accelerate rigor most effectively following high current stunning, which tends to delay early rigor development.

Animals↗

Broiler breast meat color variation, pH, and texture.

Four experiments were conducted to determine the range of breast meat color variation observed in commercial processing plants and its relationship to muscle pH and texture. Boneless, skinless breast fillets were collected weekly from the deboning lines of five commercial processing plants over a 4-wk period. Plant personnel selected breast fillets based on their appearance as being "lighter than normal," "normal," or "darker than normal" in color. Five representative fillets of each appearance classification were transported to a central laboratory for analyses of visual score (1 to 5 with 1 = light, 3 = normal, or 5 = dark), instrumental color, muscle pH, and Allo-Kramer shear (n = 300). Visual scores, lightness (L*), redness (a*), and pH were different (P<0.05) among the three appearance groups, with no significant differences in yellowness (b*). Visual scores averaged 2.4, 3.0, and 3.6, L* was 48.8, 45.6, and 43.1, and pH was 5.63, 5.70, and 5.81 for the lighter, normal, and darker fillets, respectively. There were no significant effects of color group on breast meat texture. Correlations between the color values and pH, however, were all highly significant. These results not only indicate that there are wide variations in breast meat color in commercial production, but they also demonstrate a strong relationship between breast meat color and muscle pH.

Animals↗

Effect of chemical cleaning agents and commercial sanitizers on ATP bioluminescence measurements.

Nine chemical cleaning agents at three concentrations were studied to determine the effect on ATP bioluminescence measurements from pure ATP (PATP) and ATP from chicken exudate (CJATP). The nine commercial cleaning and sanitizing chemicals were concentrated foaming acid (FA), acid sanitizer (AS), iodine cleaner-disinfectant (ZI), alkaline cleaner-degreaser (PC), chlorinated alkaline cleaner (CA), chlorinated sanitizer (CS), quaternary ammonium (QA), antibiofilm agent (AB), and acidic peroxygen sanitizer (HP). Effect was reported as a percent change from the log10 relative light unit (LRLU) measurements of the control groups. All cleaners and sanitizers were tested at one-tenth of the manufacturer's recommended level (MRL), MRL, and two times MRL. FA, PC, and CA at all three concentrations significantly decreased PATP and CJATP LRLU. AS decreased PATP and CJATP LRLU at 200 and 400 ppm quaternary ammonium. ZI decreased PATP LRLU at MRL or greater, while CJATP LRLU were decreased by all concentrations of ZI tested. CS decreased PATP LRLU in a dose-dependent manner; however, for CJATP, LRLU decreased slightly at the two lower concentrations but were not affected by 1,200 ppm CS. QA at MRL or above for PATP or at all concentrations for CJATP significantly increased LRLU. AB decreased LRLU at all concentrations tested for PATP or at MRL or greater for CJATP. HPA at MRL or greater for PATP or at all concentrations for CJATP significantly reduced LRLU. These results demonstrate that commercial sanitizers and cleansers may squelch or increase LRLU measurements when the chemical comes into direct contact with the ATP bioluminescence reagents. Hence, when using ATP bioluminescence as a means of determining sanitary quality of food-processing equipment, it is essential to consider the type and concentration of chemical cleaner or sanitizer being used on the equipment prior to testing.

Adenosine Triphosphate↗

Comparison of a Modified Atmosphere Stunning-Killing System to conventional electrical stunning and killing on selected broiler breast muscle rigor development and meat quality attributes.

Two experiments were conducted to compare the effects of a 70:30 argon:carbon dioxide Modified Atmosphere Stun-Kill (MASK) system to both a low voltage (LV) and a high current (HC) electrical stunning and conventional killing system on broiler breast rigor development and meat quality. In Experiment 1, the effects on breast muscle pH and meat tenderness of the MASK system and the LV system were compared. In Experiment 2, the MASK system was compared to both HC and LV stunning for pH, R-value, C.I.E. L*, a*, b*, cooked yield, and tenderness of broiler breast meat. In Experiment 1, there were no significant differences in breast muscle pH between LV and MASK, except at 24 h. Only at 5 h post-mortem did the MASK system result in significantly tougher breast meat. In Experiment 2, there were no significant differences between treatments in breast muscle color or cooked yield at any sampling time. The breast muscle from birds subjected to the HC stun had consistently higher pH values until 5 h post-mortem, at which time the breast meat from birds subjected to the MASK system had higher pH. R-value data showed a similar trend, with the HC stunned birds having the lower R-values until 5 h post-mortem. Breast meat tenderness values for the three treatments were significantly different only at 3 and 5 h post-mortem, when birds stunned with HC had the highest shear values. The MASK system did not exhibit any rigor accelerating benefits when compared to LV stunning and conventional killing, and only minimal rigor acceleration when compared to HC killing.

Abattoirs↗

The relationship of broiler breast color to meat quality and shelf-life.

A total of three experiments were conducted to compare physical and microbiological properties of raw and marinated broiler breast fillets selected as being either lighter or darker than normal. Visibly light- and dark-colored breast fillets were divided into marinated and control groups, and vacuum-tumbled for 20 min at 4 C under 80 kPa pressure. Breast fillets from the four treatment groups were evaluated for shear values, raw and cooked meat pH, drip-loss, cook-loss, water-holding capacity, and 7 d psychrotrophic count. The light-colored fillets were significantly lighter, less red, and more yellow than the dark fillets. Lightness values increased when fillets were marinated. Moreover, the light fillets had a lower pH than dark fillets. The pH values of raw and cooked breast meat were related to meat color but not marination. Dark-colored fillets had significantly higher marination pick-up and a higher fraction of bound moisture and significantly lower drip and cook-loss. No differences were observed in shear values between color or marination treatments. There were no significant differences in psychrotrophic plate counts (PPC) or capacitance detection times (CDT) due to color or treatment at Day 1. After 7 d of storage at 4 C, PPC was significantly lower for marinated samples. No correlations were observed between pH and PPC, CDT, or odor. Based on these differences in physical and microbiological properties, further processors may consider separating breast fillets according to color.

Animals↗

Effect of chemical sanitizing agents on ATP bioluminescence measurements.

Experiments were conducted to determine the effects of sodium hypochlorite (SH), quaternary ammonium (QA), trisodium phosphate (TSP), lactic acid (LA), hydrogen peroxide (HP), and trichlosan (TR) on ATP bioluminescence measurements. Each sanitizer was tested at three different levels and compared to a control group containing no sanitizer. ATP from three sources was analyzed, Escherichia coli, chicken blood, and a pure ATP standard. The effect of each sanitizer was reported as a percent decrease in log10 relative light units (LRLU) for the treatment groups when compared to LRLU from the control groups. SH concentrations of 30, 50, and 70 ppm and quaternary ammonium at concentrations of 10, 20, and 30 ppm had no effect on LRLU measurements, regardless of the ATP source. LA concentrations of 0.5% and higher reduced LRLU by 75%. LRLU measurements were significantly (P < or = 0.05) reduced by approximately 60% when levels of TSP exceeded 1%. HP had no effect on LRLU measurements from any of the ATP sources at 0.1%; however, at 1% HP significantly (P < or = 0.05) decreased LRLU measurements by approximately 60% for all ATP sources. TR at 0.25% had no significant effect on LRLU measurements from any of the ATP sources. TR at 0.5 and 1% reduced LRLU measurements by 30 and 50%, respectively. These results indicate that commercial sanitizers containing LA, TSP, HP, or TR may negatively affect LRLU measurements if the sanitizer is allowed to come into direct contact with the ATP bioluminescence reagents.

Adenosine Triphosphate↗

Hypercholesterolemia exacerbates transplant arteriosclerosis via increased neointimal smooth muscle cell accumulation: studies in apolipoprotein E knockout mice.

BACKGROUND: Hypercholesterolemia is thought to be a significant risk factor for coronary vasculopathy in cardiac transplant recipients. METHODS AND RESULTS: We examined the development of arteriosclerosis in mouse carotid artery loops allografted from B.10A(2R) (H-2h2) donors to normocholesterolemic C57BL/6J (H-2h) recipients and hypercholesterolemic C57BL/6J recipients in which the apolipoprotein (apo) E gene had been knocked out. Luminal occlusion and cross-sectional neointimal area were greater in arteries allografted into hypercholesterolemic recipients at 15 and 30 days after transplantation. We also measured cellular and extracellular matrix components of the neointima by computerized planimetry of the fractional areas subtended by smooth muscle cells (anti-alpha-actin stain), collagen (Masson's trichrome), lipid (oil red O), and leukocytes (anti-CD45). The neointimal area stained for smooth muscle cells was significantly greater in hypercholesterolemic recipients than in normocholesterolemic recipients at 15 and 30 days after allografting. Lipid contributed to neointimal area to a lesser degree, and there was no significant increase in the contribution of collagen or leukocytes. CONCLUSIONS: Smooth muscle cell accumulation appears to be the principal contributor to the increase in neointimal area observed in arteries allografted into hypercholesterolemic mice.

Animals↗

Effect of cloacal plugging on microbial recovery from partially processed broilers.

Experiments were performed to test the contribution of bacteria contained in the intestinal tract of broilers at the beginning of processing to counts on the exterior of modified New York-dressed carcasses. Thirty-two birds were processed for each of seven replications. Within each replication, batches of four birds were electrocuted, scalded, and picked, with batches alternating between treatment and control groups. Treated birds were cloacally plugged with rayon fiber tampons prior to electrocution to prevent escape of intestinal contents during scalding and picking. Control birds were processed in the same manner, except that cloacal plugs were inserted immediately after defeathering to reduce escape of intestinal contents during sampling. Gram-negative enteric bacteria and Campylobacter spp. were enumerated on carcasses by whole carcass rinse procedure and in cecal contents. Counts were converted to log10 and subjected to analysis of variance. Cecal levels of Gram-negative enterics were significantly higher for plugged birds, but there was not a significant difference between levels of cecal Campylobacter spp. between treatment groups. Plugging before electrocution resulted in significantly lower levels (2.5 vs 3.0 log10 cfu/mL) of Campylobacter spp. and Gram-negative enteric bacteria (3.0 vs 3.4 log10 cfu/mL) in carcass rinses of treatment birds than in those of controls. All carcasses were positive for Gram-negative enterics. Cloacal plugging resulted in significantly lower incidence of Campylobacter spp. carcass contamination as determined by chi-square. Intestinal carriage of both campylobacters and Gram-negative enteric bacteria appears to influence the microbial quality of the carcass during processing.

Analysis of Variance↗

The relationship of broiler breast meat color and pH to shelf-life and odor development.

Experiments were conducted to compare the shelf-life of dark-colored and light-colored broiler breast meat. In each of three trials, 100 breast fillets were obtained from a commercial processing plant and subjectively categorized as "dark" or "light". The 100 fillets were then objectively evaluated for C.I.E. color values (lightness, redness, and yellowness). The fillets were separated into five storage groups, with each group containing 10 dark and 10 light fillets, and the fillets were held at 3 C for 0, 3, 6, 9, and 12 d. On each sampling day, fillets were evaluated in duplicate for psychrotrophic plate count (PPC), capacitance detection time (CDT), pH, and subjective odor evaluation. Dark fillets had significantly (P < 0.05) lower lightness values (L*), higher redness values (a*), lower yellowness values (b*), and higher pH values. Regression coefficients for odor scores resulted in darker fillets having significantly (P < 0.05) higher slopes than lighter-colored fillets even though intercept values were similar. Significant correlations existed between pH and color as well as odor, CDT, and PPC. These data suggest that darker broiler breast meat fillets have a shorter shelf-life than lighter breast fillets; the shorter shelf-life may be due to differences in pH.

Animals↗

A comparison of high current and low voltage electrical stunning systems on broiler breast rigor development and meat quality.

Experiments were conducted to compare the effects of a high current (HC) stunning system to a low voltage (LV) stunning system on broiler carcass and meat quality. A total of 360 broiler chickens were individually stunned using either 125 mA, 50 Hz, constant AC for 5 s (HC) or using 10.5 V, 500 Hz pulsed DC for 10 s (LV). Birds were individually weighted, killed by conventional neck cut, bled for 150 s, and reweighed to determine blood loss. Breast fillets (Pectoralis major) were removed from the carcass immediately after picking (0 h) or after aging for 24 h in a static ice-water slush. Breast muscle pH was determined at both 0 and 24 h. Raw breast meat color (CIELAB) and cooked breast meat Allo-Kramer shear values were determined on samples held at 2 C for 48 h. The LV stunning treatment significantly increased (P < 0.05) blood loss (4.0 vs 3.7%) and significantly reduced initial muscle pH (6.47 vs 6.67) when compared to the HC stunning treatment. There were no significant differences between the stunning systems for 24 h pH, raw breast color, and Allo-Kramer shear. High current stunning reduced initial blood loss and delayed early rigor development compared to the LV treatment, but appeared to have little effect on final meat quality.

Animals↗

N-ethylmaleimide (NEM) can significantly improve in situ hybridization results using 35S-labeled oligodeoxynucleotide or complementary RNA probes.

We predicted that a significant source of background labeling after in situ hybridization (ISH) using 35S-labeled probes is attributable to a chemical reaction between the phosphorothioate moiety of the probe [O3P = S] and disulfides in tissue. These covalent bonds would immobilize probe in the tissue, thereby increasing background labeling. On the basis of this view, we have explored the use of N-ethylmaleimide (NEM) to irreversibly alkylate the phosphorothioate moiety of the probe and/or to alkylate free sulfhydryls in tissue to block the formation of disulfides as a method of reducing background labeling. We report that NEM can significantly decrease background labeling of 35S-labeled oligodeoxynucleotide or cRNA probes but does not affect specific labeling. We conclude that the use of NEM in ISH protocols, as outlined here, may be an additional element researchers may consider to improve the signal-to-noise ratio.

Brain Chemistry↗