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The wooden breast (WB) condition in broiler breast meat negatively influences technological meat quality. However, it is unknown if the WB effects are uniform throughout the Pectoralis major. The objective of this study was to determine the effects of WB on the marination and cooking performance of the dorsal and ventral portions of broiler breast fillets. Sixty butterfly breast fillets were collected from the deboning line of a commercial plant and sorted into normal (no WB) and severe WB categories. Each fillet was horizontally portioned into dorsal and ventral halves. Portions from one side of each butterfly were used as non-marinated controls, while portions from the other side were vacuum-tumble marinated (16 rpm, −0.6 atm, 4°C, 20 min) with 20% (wt/wt) marinade to meat ratio. Marinade was formulated to target a final concentration of 0.75% salt and 0.45% sodium tripolyphosphate in the final product. Samples were cooked to 78°C in a combination oven. Marinade uptake and retention were lower (P < 0.001) in both the ventral and dorsal portions of the WB fillets. The dorsal portions had greater (P < 0.001) marinade uptake and retention than the ventral portions in both normal and WB fillets. For non-marinated samples, cook loss was greater (P < 0.05) in both the ventral and dorsal portions of WB fillets. In marinated samples, however, cook loss was similar between the dorsal portions of normal and WB fillets. Final cooked product yield was calculated based on pre-marination and post-cook weights. Non-marinated WB samples exhibited lower (P < 0.001) cooked product yields than normal samples in both portions. For marinated samples, cooked product yields were greater (P < 0.001) in the dorsal portions. Data demonstrated that the dorsal portion of the Pectoralis major more readily absorbs and retains marinade during vacuum tumbling and storage than the ventral portion. Although the WB condition negatively influenced marination and cooking performance in both fillet portions, the effects were less severe in the dorsal portion. [ABSTRACT FROM AUTHOR]

The wooden breast (WB) myopathy influences muscle composition and texture characteristics in broiler breast meat. It is unknown if marination reduces the negative influence of WB on meat sensory quality or if WB effects are uniform throughout the Pectoralis major. The objective of this study was to determine the effects of marination on the sensory attributes and instrumental shear force measurements of the ventral (skin-side) and dorsal (bone-side) portions of normal and severe WB meat. Sixty butterfly fillets (30 normal and 30 severe WB) were selected from the deboning line of a commercial processing plant. Individual fillets were portioned into ventral and dorsal halves. Portions from one side of each butterfly were used as non-marinated controls, and portions from the other side were vacuum-tumble marinated (16 rpm, −0.6 atm, 4°C, 20 min) with 20% (wt/wt) marinade to meat ratio. Marinade was formulated to target a concentration of 0.75% (w/v) salt and 0.45% (w/v) sodium tripolyphosphate in the final product. Descriptive sensory analysis (9 trained panelists) was conducted to evaluate visual, texture, and flavor attributes (0–15 point scale) of breast portions along with Warner-Bratzler shear force. Significant interaction effects between WB and marination were not observed for the sensory attributes. Greater springiness, cohesiveness, hardness, fibrousness, and chewiness scores were observed in WB samples (P < 0.001). Marination decreased cohesiveness, hardness, and chewiness (P < 0.05) and increased juiciness (P = 0.002). The effects of WB on sensory texture attributes were more apparent in the ventral portions of the breast fillets. Flavor attributes (salty and brothy) increased (P < 0.001) with marination. In non-marinated samples, shear force was similar between normal and WB samples. In marinated samples, however, shear force was greater (P < 0.001) in WB samples. Data suggest that the WB effect on meat sensory quality is not uniform throughout the Pectoralis major and that WB-related differences in cooked meat sensory texture attributes are lessened but not eliminated by vacuum-tumbling marination. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of the wooden breast (WB) condition on the texture of cooked broiler breast fillets (Pectoralis major) after fresh and frozen storage. Texture characteristics of normal (NORM) and severe WB fillets were studied by both sensory descriptive analyses and Warner-Bratzler shear force. Broiler breast fillets were collected over 3 separate trial days from a commercial deboning line at 3 h postmortem, classified according to the wooden breast condition, and then stored at either 4°C or –20°C prior to cooking and texture evaluation. Fillets were cooked to an endpoint temperature of 76°C and then evaluated by an 8-member trained sensory panel for springiness, cohesiveness, hardness, juiciness, cohesiveness of mass, bolus size, wetness of mass, fibrous texture, rate of breakdown, and chewiness. The fillets with the WB condition showed higher cook loss than those with NORM condition regardless of storage temperature. The mean value of shear force of WB fillets was lower than NORM fillets when cooked after 4°C storage. Sensory evaluation showed that WB fillets were higher in springiness and cohesiveness than NORM fillets and that the sensory attributes springiness, hardness and fibrousness were perceived differently between ventral and dorsal sections of cooked WB fillets. This work indicates that human perception of cooked WB meat has texture irregularities. The cooked breast meat with the WB condition is perceived with more springiness and cohesiveness than that with no WB condition. [ABSTRACT FROM AUTHOR]

Broilers in the United States are typically electrically stunned using low voltage-high frequency (12-38 V, ≥400 Hz) DC or AC water bath stunners. In the European Union, however, broilers are required to be electrocuted using high voltagelow frequency (50-150 V, 50-350 Hz) AC. Low voltage stunned broilers regain consciousness in the absence of bleeding. In contrast, high voltage stunned broilers die due to induction of cardiac fibrillation. For birds stunned with low voltage systems, concerns have been raised regarding animal welfare during bleeding. This work evaluated the impact of extended DC stunning duration and alternative stunning methods (DC+AC combination) on the recovery of bird consciousness and meat quality. In the absence of bleeding, broilers that were DC stunned for extended times (60, 90, or 120 s), 63, 10, or 0% of broilers, respectively, were able to recover consciousness. Alternative stunning protocols included water bath stunning broilers at 15 or 25 V DC for 10 s followed by plate stunning at 100, 110, or 120 V AC for 5 s. Prior to shackling, live body weight and shank width were measured and during stunning, maximum mA for both DC and AC stuns were recorded. All of the alternative stunning protocols (DC+AC) resulted in non-recoverable stunning. The maximum mA recorded during both DC and AC stunning were moderately/strongly (r = 0.54-0.81) correlated to body weight and poorly/moderately (r = 0.27-0.74) correlated to shank width. No significant differences for carcass or meat quality characteristics (hemorrhages, red wing tips, broken clavicles, pH, cook loss, a* and b* color values, and MORS shear energy) were detected between control (15 or 25 V DC only) and treatment groups (DC+AC combination stunning). The only significant different meat quality parameter was L* values where the lowest voltage group (15 V DC) had the darkest fillets (53.27) and the 15 V DC+100 V AC group had the lightest fillets (55.61) with all other groups intermediate. These data indicate that stunning parameters combining DC and AC stunning may be viable protocols when a stun-to-death is desired. [ABSTRACT FROM AUTHOR]

The white striping (WS) condition in broiler meat results in increased intramuscular fat, connective tissue, and moisture loss during cooking and negatively affects product appearance and consumer acceptance of skinless chicken meat. The effect of WS on the human perception of cooked meat texture is unknown. The objective of this study was to evaluate the effects of WS on sensory texture attributes of cooked chicken breast fillets (Pectoralis major). Over three separate trial days, a total of 105 breast butterfly fillets were collected from the deboning line of a commercial broiler processing plant. Fillets were classified according to the degree of WS (normal, moderate, severe) and stored at -20±C until use. Fourteen representative fillets from each category were cooked directly from the frozen state to an endpoint temperature of 78±C and evaluated by a 7-member trained panel for five texture attributes: cohesiveness, hardness, juiciness, rate of breakdown, and chewiness. There were no differences (P > 0.05) for juiciness or the rate of breakdown between the fillets based on the degree of WS. Among the three WS groups, however, differences (P < 0.05) in cohesiveness, hardness, and chewiness were observed. For these attributes, the mean intensity scores of fillets with severe WS were consistently highest among the groups. There were no differences (P > 0.05) between the normal and moderate WS fillets. These data suggest that the severe WS condition was perceived to be harder, more cohesive, and chewier than either normal or moderate WS fillets by panelists. [ABSTRACT FROM AUTHOR]

Three experiments were conducted to evaluate the effects of postmortem deboning time on cook yield of boneless skinless chicken thighs. In experi-ment 1, chicken thigh meat was deboned at 0.75 (hot-bone), 2, and 24 h postmortem (PM) and trimmed to obtain mainly iliotibialis muscle. Samples were cooked directly from a frozen state. Cook yield of the muscle was significantly influenced by PM deboning time. Hot-boned thighs exhibited a 7% greater cook yield than the samples deboned at 24 li. In experiment 2, boneless skinless chicken thighs were deboned at 0.3, 2, and 24 h PM and cooked directly from a fresh, never-frozen state at 24 h PM. Cook yield of the hot-boned thighs was significantly higher than those of the 2 and 24 h deboned samples, which did not differ from each other. In experiment 3, whole legs (thigh + drumstick) were cut from the carcass backbone at 0.3 (hot-cut), 2, and 24 h PM. Thighs were separated from the legs (drum-sticks) at either the same time the whole legs were re-moved from the carcasses or at 24 h PM. Intact thighs (bone in) were cooked fresh at 24 h PM. Color of fresh thigh muscles, cook yield, and Warner-Bratzler shear force of cooked samples were measured. Cook yield of the thighs cut from the backbone before chilling was significantly higher than those cut from the carcasses at 2 and 24 h PM, which did not differ from each other. The PM time at which intact thighs were separated from the leg (drumstick) did not influence cook yield. These results demonstrate that postmortem deboning time can significantly affect cook yield of boneless skin-less chicken thigh products. Deboning chicken thighs after chilling reduces the cook yield. Differences in the cook yield of thighs may also result from the removal of whole chicken legs from the carcass backbone. [ABSTRACT FROM AUTHOR]

The objective of this study was to deter-mine the relationship between meat quality and the protein content and composition of muscle exudate from broiler breast fillets. Deboned breast fillets (n = 48) were obtained from a commercial processing facility and segregated into 2 groups based on color (light and dark). Meat pH, color, moisture content, 3 measures of water-holding capacity (drip loss, salt-induced water uptake, cook loss), protein solubility, and the protein content of muscle exudates were determined in breast fillets. The protein composition of the muscle exudate was evaluated using SDS-PAGE analysis. Light breast fillets had lower meat pH (4 and 24 h postmortem) and higher L* (lightness) and b* (yellowness) values than dark fillets. Light breast fillets exhibited greater drip loss after 2 and 7 d of storage, lower salt-induced wa-ter uptake, and higher cook loss than dark fillets. Nei-ther sarcoplasmic nor total protein solubility differed between light and dark fillets. Protein concentration of muscle exudates was greater in dark fillets and was negatively correlated to drip loss after 2 d of storage (r = -0.50) and salt-induced water uptake (r = 0.42). Electrophoretic protein banding patterns were similar between muscle exudates and sarcoplasmic protein ex-tracts. Gel electrophoresis data from muscle exudates showed that the relative abundance of 4 bands cor-responding to 225, 165, 90, and 71 kDa was higher in dark breast fillets. The relative abundance of 3 bands corresponding to 47, 43, and 39 kDa was higher in light breast fillets. Muscle pH and measurements of water-holding capacity were significantly correlated to the abundance of several individual protein bands within the protein profile of muscle exudates. Data from this study showed that protein differences in breast muscle exudates are related to meat pH, color, and water-hold-ing capacity and suggest that muscle exudate could be a potential source of protein markers for fresh meat quality attributes in broiler fillets. [ABSTRACT FROM AUTHOR]

The effects of hydrodynamic pressure processing (HDP) on marination and meat quality characteristics of turkey breasts were investigated. Breast muscles from 45 turkey hens were removed from the carcasses within 30 mm postmortem. From each bird, the breast from one side was treated with HDP and the other side served as a nontreated control. Breasts were then marinated in either 15 or 30% brine (water, salt, and phosphate) based on muscle weight with vacuum tumbling for 30 mm or nonmarinated. The control and HDP-treated breasts from each bird received the same marination treatment. Brine uptake, processing yield, and cooking loss were measured as processing characteristics and texture, color, and expressible moisture were measured to document changes in meat quality. Hydrodynamic pressure processing increased (P < 0.001) brine uptake after 10 and 30 mm of marination and increased (P < 0.001) processing yield compared with controls. The HDP-induced improvements in these processing characteristics were augmented at 30% brine levels compared with 15% brine. Cooking loss was lower (P < 0.001) in marinated breasts compared with nonmarinated samples. Hydrodynamic pressure processing decreased (P < 0.0001) Warner-Bratzler shear force and significantly influenced texture profile parameters, resulting in reduced hardness but increased cohesiveness and springiness compared with controls at both marination levels. Hydrodynamic pressure processing did not influence color (L*, a, and b*) or expressible moisture values compared with controls at either mannation level. Marinated samples (15 and 30% brine levels) had lower (P < 0.001) Warner-Bratzler shear force values and lower (P < 0.05) hardness, cohesiveness, and chewiness values compared with nonmarinated samples. Data from this study suggest that HDP enhances brine absorption, increases processing yield, and improves texture characteristics in marinated turkey breasts. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the influence of hydrodynamic pressure processing (HDP) and aging on the overall quality and protein characteristics of pork loins. Boneless pork loins (n = 12) were split into anterior and posterior halves and were assigned to control and HDP treatments. Following treatment on day 0, each half was divided into two portions (0 and 7 days aging). Samples were removed for the determination of Warner–Bratzler shear force (WBSF), centrifugal moisture loss (CML), gravitational drip loss (DL), color, protein solubility and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of whole muscle protein extracts. WBSF decreased with HDP (P < 0.05) and aging treatments (P < 0.0001). CML decreased (P < 0.0001) with aging. Controls exhibited slightly less DL after 1 day than HDP samples, but the increase in DL between 1 and 7 days was similar for control and HDP samples. Treatment effects on L *, a * and b * measurements were minimal. Myofibrillar and total protein solubility were higher (P < 0.01) in HDP samples compared with controls at day 0 but not at day 7. Sarcoplasmic protein solubility decreased (P < 0.05) with aging. SDS-PAGE analysis of muscle proteins demonstrated a strong aging effect and only minor HDP differences. With aging, bands corresponding to 30–33 and 135 kDa increased (P < 0.0001), while bands corresponding to 38 and 95 kDa decreased (P < 0.05) in intensity (relative to the actin band). The 60 kDa band intensity increased (P < 0.05) with both aging and HDP treatments. Thus, data from this study suggest that HDP enhances aging tenderization in pork loins through the physical disruption of the muscle ultrastructure while having little detrimental effect on other parameters of pork quality. PRACTICAL APPLICATIONS This study demonstrates that hydrodynamic pressure processing is an effective postharvest technology for enhancing aging tenderization in pork loins through the physical disruption of the muscle ultrastructure with minimal impacts on other pork quality parameters such as water-holding capacity and color. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of hydrodynamic pressure processing (HDP) and aging on the sarcoplasmic proteins of beef strip loins. Loins (n = 12) were halved at 48 h postmortem and assigned to HDP or control treatments. Following treatment, each half was divided into three portions for aging (0, 5 or 8 d). Samples were removed for Warner-Bratzler shear force (WBSF) determination and sarcoplasmic protein isolation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis demonstrated that aging significantly influenced the composition of the sarcoplasmic protein fraction and that HDP influenced protein bands corresponding to 143, 65, 44, 36 and 19 kDa. Changes in sarcoplasmic protein composition were significantly correlated to WBSF (r = − 0.58 to 0.45). Sarcoplasmic protein solubility decreased with both HDP (P < 0.05) and aging (P < 0.0001). Changes in solubility were significantly correlated to SDS-PAGE band intensities (r = − 0.53 to 0.60). Data suggest that HDP and aging cause changes to sarcoplasmic proteins that may be indicators of proteolysis and tenderization. PRACTICAL APLICATIONS Results from this study demonstrate that postmortem aging and hydrodynamic pressure processing of beef influences the sarcoplasmic protein profile of the muscle. The relationships between these changes and Warner-Bratzler shear force measurements suggest that sarcoplasmic protein changes may be potentially useful as tenderness indicators. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of hydrodynamic pressure (HDP) processing and aging on the tenderness and myofibrillar proteins of beef strip loins. Loins (n = 12) were halved at 48 h postmortem and assigned to HDP or control treatments. Following treatment, each half was divided into three portions for aging (0, 5 or 8 days). Samples were removed for Warner–Bratzler shear force (WBSF) determination and myofibrillar protein isolation. HDP decreased (P < 0.0001) WBSF values 23% at 0, 5 and 8 days of aging. Myofibrillar fragmentation and myofibrillar protein solubility increased (P < 0.01) with HDP and aging. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting analysis of myofibrillar proteins showed that HDP and aging decreased the intensity of the troponin T (TnT) band and enhanced the accumulation of the 30 kD TnT degradation product. These data suggest that HDP is more effective than aging tenderization, and that HDP tenderization is caused by both protein degradation and physical disruption of the myofibril apparatus. PRACTICAL APPLICATIONS Hydrodynamic pressure (HDP) processing was shown to instantaneously tenderize tough cuts of beef to tenderness levels attained following 8 days of postmortem aging. For the meat industry, these results demonstrate the potential benefits of alternative tenderization techniques, such as high-energy shock waves. Observed changes in protein characteristics due to HDP and aging allow researchers to understand better potential mechanisms of meat tenderization. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of blade tenderization (BT), hydrodynamic pressure processing (HDP) and BT followed by HDP (BT + HDP) on collagen solubility and tenderness-related protein characteristics in top rounds from Brahman cattle. Top rounds (n = 12) were divided in half and randomly assigned to HDP, BT or BT + HDP with each treatment sample having a paired control. HDP and BT + HDP increased (P < 0.0001) collagen solubility, but the correlation between percent soluble collagen and tenderness was low (r = – 0.41). All three treatments increased (P < 0.01) fragmentation of myofibrils 35% compared with controls. HDP and BT + HDP treatments increased (P < 0.05) the content of a 100 to 110-kDa protein observed in myofibrillar protein fractions by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Minimal treatment differences were observed in sarcoplasmic proteins using SDS-PAGE. Results suggest BT physically disrupts the muscle structure to improve tenderness while HDP tenderization potentially results from both physical disruption of the muscle structure and some form of direct alterations to muscle proteins. [ABSTRACT FROM AUTHOR]

The ability of sodium polyphosphate (P) to alter postmortem pH declines and pork quality was investigated. Hams from electrically stimulated carcasses were injected 18 min postmortem with P or sodium bicarbonate (SB). P and SB reduced (P < 0.001) pH decline and improved (P < 0.05) color. P and SB administration improved water-holding capacity as indicated by reductions (P < 0.05) in drip loss, thaw loss, and cooking loss values. P and SB also reduced (P < 0.001) shear values. These data showed delivery of P and SB was effective in altering postmortem pH declines and improving the quality of pork. [ABSTRACT FROM AUTHOR]

1. Early post-mortem pH was used to identify PSE-like turkey meat, characterised by a low waterholding capacity and pale colour. In a commercial turkey processing facility, the pH value of turkey breast muscle was measured at 0, 9, 10, 14, 154, 231, and 246 min post mortem. 2. At 14 min post mortem , the carcases were separated into 3 pH classes: low (<5.70), medium (5.70 to 6.18), and high (>6.18). Low pH carcasses (<5.70) had higher drip loss(1.75%) than medium (0.81%) and high pH carcases (0.75%). Furthermore, high pH carcases (>6.18) had a lower L * value (darker) than low and medium pH carcases. 3. The effects of using CO2 'snow' on turkey breast muscle quality were also investigated. Light CO2 'snow' treatment (57 g snow/kg breast) and heavy CO2 treatment (113 g snow/kg breast) resulted in higher drip losses than the control no CO2 snow) group. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of tapioca flour (TF) on physicochemical properties and sensory qualities of chicken breast meat patties. The effects were also compared with some other commonly used meat binders. Ground chicken breast meat was either mixed with different concentrations of TF (1%, 2%, or 4% w/w) or mixed with 2% TF, potato flour, garbanzo flour, or egg white. Raw meat pH, color and cook loss and cooked meat expressible moisture, shear force, and sensory flavor and texture profiles were evaluated. The addition of TF reduced pH, cook loss, expressible moisture, and shear force and increased L* values (P < 0.05). Compared to the other binders, the patties with TF did not exhibit any differences (P > 0.05) in pH, L*, and b* values; however, they had lower cook loss, expressible moisture, and shear force (P < 0.05). TF did not change the intensity of flavor but reduced meat cohesiveness, hardness, and chewiness (P < 0.05). There were no differences between TF, potato flour, and garbanzo regardless of sensory attributes; however, TF samples were perceived to be significantly less meaty, cohesive, and hard than an egg white sample. These results suggest that the addition of TF to ground chicken breast meat significantly affects raw product appearance and improves water-holding capacity. TF did not impact flavor but improved the texture of cooked meat. The TF effects on meat texture are either better than or comparable to other commonly used meat binder additives. [ABSTRACT FROM AUTHOR]

The objective was to characterize texture properties of raw and cooked broiler fillets (Pectoralis major) with the wooden breast condition (WBC) using the instrumental texture techniques of Meullenet- Owens Razor Shear (MORS) and Texture Profile Analysis (TPA). Deboned (3 h postmortem) broiler fillets were collected from a commercial plant and categorized as normal, moderate, or severe WBC based on the incidence and severity of diffuse hardened areas throughout fillets and the degree of palpable hardness. The fillets were then either stored at 4°C overnight or in a -20°C freezer. The MORS and TPA of the raw samples were determined at 24 h postmortem for fresh samples and after thawing overnight for frozen samples. The same measurements were also taken after the samples were cooked to 78°C. Regardless of freshness (fresh vs. frozen-thawed), cooking (raw vs. cooked), and degree of WBC, both MORS force and energy of the WBC samples were higher than that of the normal samples (P < 0.05). For TPA adhesiveness and resilience, there were no differences between normal and WBC samples (P > 0.05). However, average TPA hardness and chewiness measurements of the fillets with WBC were higher than the normal fillets (P < 0.05). Regardless of texture measurement, there were no interactions between freshness and the wooden condition or no differences between moderate and severe WBC fillets (P > 0.05). These results demonstrate that there are significant differences in instrumental texture properties between normal fillets and those exhibiting the WBC. The WBC fillets required more force to cut through, harder, and chewier than normal breast muscles. These results suggest that cooked WBC meat would likely be tougher than cooked normal meat. [ABSTRACT FROM AUTHOR]

Foodborne campylobacteriosis has been traced to undercooked chicken liver. We have detected Campylobacter in raw chicken livers from retail and processing plant samples. In the current study, we tested a 1 or 5 min 60(C heat treatment, a 48 h 225(C freeze treatment, and a combination of both as a means to pasteurize raw chicken liver lobes. We cultured treated and untreated liver lobes to determine numbers of Campylobacter and total aerobic bacteria. Overall, the 1 min heat treatment was ineffective. The 5 min heat treatment significantly lowered Campylobacter numbers. Freezing was also moderately effective. The combination of both heating and freezing resulted in nearly 99% decrease in Campylobacter numbers but was accompanied by significant lightening of the liver tissue. A mild heat treatment with or without subsequent freezing will not assure elimination of Campylobacter but may lessen consumer risk because of exposure in kitchen and during meal preparation. [ABSTRACT FROM AUTHOR]

Microbiological safety and quality of fresh chicken meat are important concerns to industry. The objective of this study was to investigate the effects of in-package, non-thermal high voltage dielectric barrier discharge (HVDBD) treatment on microbial quality, safety, and color of fresh chicken breast meat (pectoralis major). Boneless skinless chicken breast meat was collected from a local commercial plant. Non-inoculated meat samples and meat samples inoculated with Campylobacter jejuni and Salmonella Typhimurium were packed in polymeric trays under ambient air conditions. The packaged samples were HVDBD-treated at different voltages (0, 55, 70, or 85 kV) for 180 s, and stored at 4°C for 5 d. Microbial counts (psychrophiles, C. jejuni, S. Typhimurium) and meat color (L*a*b*) were measured before HVDBD treatment and after 5 d of post-treatment storage. Psychrophile growth was inhibited (P < 0.05) and both foodborne pathogens were reduced (P < 0.05) by HVDBD treatments regardless of treatment voltage. No differences in psychrophilic and S. Typhimurium counts were observed between the three treatment voltages; however, increasing treatment voltage beyond 55 kV resulted in additional inactivation of C. jejuni. In terms of meat color, there were no differences (P > 0.05) in a* and b* values between pre-treatment and post-treatment measurements; however, all HVDBD treatments resulted in increased L* value (P < 0.05). Results indicate that in-package HVDBD treatment can be used to reduce both microbial spoilage and foodborne pathogen risks; however, in-package HVDBD treatment may increase pale color in raw chicken breast meat. [ABSTRACT FROM AUTHOR]

Scanning electron microscopy (SEM) was utilized to evaluate microstructural changes in intramuscular connective tissue of beef semimembranosus muscle subjected to hydrodynamic pressure processing (HDP). Samples were HDP treated in a plastic container (HDP-PC) or a steel commercial unit (HDP-CU). Control and HDP samples were obtained immediately post-treatment and after 14days of aging for SEM and Warner-Bratzler shear force (WBSF) analysis. Immediately post-treatment, HDP treated samples exhibited lower (P<0.01) WBSF than did controls. After aging, HDP-PC samples had lower (P<0.01) WBSF than that of aged controls. SEM analysis indicated that HDP-PC treatment disrupted the integrity of the collagen fibril network of the endomysium in both the non-aged and aged samples. Aging effects on the intramuscular connective tissue were observed in the HDP-PC and control samples. Both WBSF and connective tissue changes were greater in the HDP-PC than in the HDP-CU treated samples. Data suggest that shockwave alterations to connective tissue contribute to the meat tenderization of HDP., (Published by Elsevier Ltd.)

The objectives of this study were to determine the influence of pH and MyHC isoforms on myofibrillar and actin-activated myosin subfragment 1 (S1) ATPase activity and the protective effect of actin. Red (RST) semitendinosus and white (WST) semitendinosus myofibrils were incubated at pH 7, 6, or 5.5 with 0 or 2mM ATP. RST and WST S1 isolates were incubated at pH 7, 6, or 5.5 in the presence or absence of actin. Maximum calcium-activated myofibrillar and actin-activated S1-ATPase activity were then assayed at pH 7. Incubation of myofibrils with ATP caused ATPase activity of myofibrils to decrease (p<0.05) with the pH of the incubation. RST myofibrils maintained a higher (p<0.0001) relative activity than WST myofibrils after incubation at pH 6 with ATP. Myofibrils incubated without ATP exhibited higher (p<0.001) activities than those incubated with ATP following pH 5.5 treatments. WST myofibrils had a lower (p<0.05) relative activity than RST following incubation at pH 5.5 without ATP. S1 ATPase activities decreased (p<0.05) with incubation pH in WST samples, but not in RST samples. WST S1 activity was higher (p<0.01) in samples exposed to pH 6 and 5.5 with actin bound compared to those incubated without actin. RST S1 exhibited a higher (p<0.01) relative activity than WST samples following pH 5.5 treatment with bound actin. These data show that low pH inactivates myofibrils by altering actin-activated S1 ATPase. Furthermore, these results suggest that muscles with high proportions of fast fibers are more susceptible to pH inactivation of ATPase activity and that the protective effect of actin binding to myosin is less in fast fibers.

The objective of this study was to determine the effects of postmortem muscle pH and temperature declines on the actomyosin ATPase activity of muscle fibers expressing different MyHC isoforms. Using a quantitative histochemical procedure to determine ATPase activity, the maximum actomyosin ATPase activity was determined on individual fibers classified by MyHC expression. Samples were collected from the red (RST) and white (WST) semitendinosus muscles at 3 min and 24 h postmortem from electrically stimulated (ES) and control (NS) pork carcasses. In samples taken at 3 min postmortem, type I fibers had the lowest ATPase activity staining and type 2X and 2B had the highest activity staining, with type 2A fibers intermediate. Postmortem time and carcass treatment did not influence the ATPase activity staining of type I muscle fibers. ATPase activity staining of 2A fibers was lower (p<0.001) in 24 h samples than in 3 min samples from ES carcasses. In 3 min and NS-24 h samples, RST type 2A fibers had lower (p<0.05) activities than type 2A fibers from the WST. In type 2X fibers, ATPase activity staining decreased (p<0.01) from 3 min to 24 h postmortem in ES carcasses. This decrease was more severe in WST 2X fibers compared to RST 2X fibers. ATPase activity staining in type 2B fibers did not decrease from 3 min to 24 h postmortem in NS carcasses. In ES carcasses, activity staining of 2B fibers decreased (p<0.0001) with time postmortem. The results of the experiment indicate that fibers expressing fast MyHC isoforms have a higher ATPase activity early postmortem than slow muscle fibers but are more prone to inactivation by a rapid pH decline.

The pH and Ca(2+) sensitivity of myofibrillar ATPase activity plays an integral role in regulating postmortem muscle ATP utilization and likely paces postmortem glycolysis. The objective of this study was to determine the influence of pH and Ca(2+) concentration on the ATPase activity of myofibrils from red semitendinosus (RST) and white semitendinosus (WST) porcine muscles. Myofibrillar ATPase was measured at 39 °C over a pH range 5-7.5 and a [Ca(2+)] range pCa 4-9 (10(-4)-10(-9)M). At maximum Ca(2+)-dependent activation (pCa 4), RST myofibrils had lower (p<0.0001) ATPase activity than WST myofibrils. This maximum activity of myofibrils from both muscle regions was not influenced from pH 7.5 to 6.5, declined between pH 6.5 and 5.75 (Hill coefficient, n(H)=2.7-3.4; pH at half maximum activity, pH(50)=5.97) and was near zero at pH 5.5. At pH 7, pCa-activity relationships showed that RST required less Ca(2+) for half-maximum activation (higher pCa(50); 6.50) than WST myofibrils (pCa(50)=6.35) but had no difference in n(H). At pH 7, both RST and WST myofibrils had maximum Ca(2+)-dependent, actin-activated ATPase activity at pCa ⩽6 and Ca(2+)-independent myosin ATPase activity at pCa ⩾6.75. pCa-activity relationships at different pH levels indicated that pCa(50) decreased with pH from pH 6.5 to 6.125 in both RST and WST myofibrils. At pH <5.75, [Ca(2+)] did not influence ATPase activity in RST or WST myofibrils. These data show that myofibrils with predominantly fast MyHC (WST) have a higher actin-activated myosin ATPase activity than myofibrils with primarily slow MyHC isoforms (RST) at Ca(2+) concentrations and pH values characteristic of postmortem muscle.

The objective of this study was to determine the influence of myofibril isolation procedures and myosin heavy chain (MyHC) isoform composition on myofibrillar ATPase activity as related to postmortem muscle metabolism. Myofibrils from the red (RST) and white (WST) portions of semitendinosus muscles were isolated using two different methods (A and B) at 3 min and 24 h postmortem in control (NS) and electrically stimulated (ES) pork carcasses. Comparison of the relative MyHC isoform profiles between the two different myofibril isolation methods and myosin extracts from the RST and WST at 3 min showed that method B myofibrils were more similar to the myosin extract than method A. Myofibrillar ATPase activity remained constant or increased (P<0.01) from 3 min to 24 h postmortem in NS carcasses and decreased (P<0.0001) in ES carcasses. From the RST, method A myofibrils had higher (P<0.0001) ATPase activity compared to method B across sampling time and carcass treatment. In the WST, method A myofibrils had lower (P<0.01) activity at 3 min, were not different at 24 h in NS carcasses, but had higher (P<0.05) activity at 24 h in ES carcasses versus method B myofibrils. Compared to method B, isolation method A biased the isoform profile of myofibril samples more towards faster MyHC (2A and 2X) in the RST and towards MyHC 2X in the WST. Results suggest that the ATPase activity and MyHC isoform profile of isolated myofibril samples are influenced by method of myofibril isolation, postmortem sampling time, and the rate of postmortem metabolism. Thus, differences in MyHC isoform profile and method of myofibril isolation must be taken into account to determine accurately the relationship between myofibrillar ATPase activity and rate of postmortem metabolism.

Carcasses from 64 gilts were subjected to electrical stimulation (ES) at 3, 15, 25, 35, 45, and 55 min postmortem or were untreated (NS). Temperature and pH of longissimus muscles were recorded at 1, 7, 14, 20, 30, 40, 50, and 60 min, and 24 h postmortem. Muscle samples were collected at 1, 30 and 60 min, and 24 h for determining glycolytic metabolite concentrations. ES at 3, 15, and 25 min resulted in lower (P<0.05) muscle pH, but stimulation after 25 min had no effect on muscle pH. Likewise, ES prior to 25 min resulted in greater (P<0.05) muscle temperatures. Muscle lactate concentrations were greater (P<0.05) in carcasses stimulated before 45 min postmortem. Glucose 6-phosphate concentration decreased (P<0.05) during the first hr postmortem and increased (P<0.05) thereafter. ES of carcasses at 45 and 55 min resulted in higher (P<0.05) concentrations of muscle glucose 6-phosphate at 24 h compared with NS and early-stimulated carcasses. Muscle glycogen concentrations at 30 min in carcasses stimulated at 3, 15 and 25 min were lower (P<0.05) than NS carcasses. Carcasses stimulated at 3 and 15 min exhibited lower (P<0.05) concentrations of muscle glycogen at 60 min than NS carcasses. Carcasses stimulated at 3 and 15 min postmortem exhibited lower (P<0.05) color and firmness scores, while ES at 3 and 25 min postmortem resulted in lower (P<0.05) water holding capacity. ES had no significant effect on CIE L(∗), a(∗), b(∗), or 24 h muscle pH. These data show that ES of pork carcasses during the first 25 min postmortem creates PSE-like quality characteristics and suggest that ES is a potential model for studying pork quality development.

The objective of this study was to determine if electrical stimulation (ES) early postmortem is an effective method to generate PSE-like meat. One hundred and thirty-eight gilts (85-125 kg) from heavy muscled (HM), normal muscled (NM), and light muscled (LM) porcine genetic lines were subjected to one of two treatments: ES (26 pulses of 500 V, 60 Hz) at 3 min postmortem or non-stimulated (NS). Pigs from HM line were further characterized as halothane (HAL) carriers (Nn) or non-carriers (NN). ES carcasses had lower (P<0.0001) pH values and higher (P<0.0001) temperature than NS carcasses during the first 56 min postmortem. ES carcasses had lower (P<0.0001) a*-values, and color and firmness scores, as well as higher (P<0.0001) drip loss and L*-values. No significant interactions were found between treatment and genetic line or HAL gene status with regard to pH, temperature, or quality characteristics. Temperature and pH declines within the first hour postmortem were not affected by genetic line, but slight (P<0.01) quality differences were observed. Nn and NN did not differ in pH or temperature within the first hour postmortem, but Nn carcasses had lower (P<0.01) color and firmness scores, and higher (P<0.05) drip loss. These results show that ES early postmortem is an effective method for simulating PSE development in pigs of different muscling and HAL gene status, and suggest that pH and temperature decline alone cannot explain all aspects of pork quality.