Influence of Zinc and Ractopamine Hydrochloride Supplementation on Beef Carcass Characteristics and Quality Attributes of Aged Ribeye Steaks

ObjectivesGrowth promoting technologies such as the β agonist ractopamine hydrochloride (RAC) and nutritional practices such as increased zinc (ZN) supplementation have potential to positively impact beef cattle growth. However, the impact of these strategies (RAC and ZN) on meat quality is unclear. The objective of this experiment was to determine the extent to which ZN and RAC supplementation in the diets of finishing beef steers influence carcass characteristics and meat quality of aged longissimus steaks.Materials and MethodsCrossbred Angus steers (∼431 kg initial body weight) from a single source were fed one of four diets in GrowSafe bunks. Steers were assigned to diets based on growth potential (Gene Max gain score) and initial body weight: control (CON-NO; 30 ppm Zn (NRC requirement); n = 7), ZN supplementation (SUPZN-CON; 150 ppm ZN (60 ppm ZnSO4, 60 ppm Zn-AA); n = 7), RAC supplementation (CON-RAC 300 mg/hd/d; 30 ppm Zn; n = 6), and ZN supplementation combined with RAC supplementation (SUPZN-RAC; 150 ppm ZN (60 ppm ZnSO4, 60 ppm Zn-AA), RAC 300 mg/hd/d; n = 7). Zn treatments were fed for the entire 90 d trial. RAC supplementation occurred for the final 28 d of the feeding trial. At finishing weights (∼739 kg), steers were harvested at a commercial processing facility. Yield and quality data were collected. Whole rib sections were collected 6 d postmortem, transported to the Iowa State University Meat Lab, and fabricated into 2.54 cm thick steaks. Temperature, pH, Hunter L, a, and b values, and proximate analysis (moisture, fat and protein) were measured at 6 d postmortem on the longissimus muscle. Pairs of adjacent steaks were vacuum packaged, aged for 7, 14, 28 or 42 d, and frozen until quality evaluation. At the completion of aging and storage; purge, pH, Hunter L, a, and b values, marbling scores, cook loss, and Warner-Bratzler Shear Force (WBS) values were measured on each pair of steaks. Data were analyzed using the PROC MIXED procedure of SAS version 9.4 with fixed effect of treatment. Initial body weight was used as a covariate for hot carcass weight (HCW) analysis. HCW was used as a covariate for analysis of ribeye area, fat thickness (FT), kidney, pelvic and heart fat percentage, yield grade, and d 6 marbling score. FT was used as a covariate for d 6 pH and temperature measurements.ResultsSupplementation of Zn and RAC resulted in a greater HCW and REA with decreased fat thickness, marbling scores, and yield grades than CON-NO. Zn only supplementation had greater redness at 6 and 7 d postmortem. RAC supplementation resulted in increased WBS values at 7, 14, and 28 but no differences were observed at 42 d aging. No differences in KPH, pH, temperature, L and b value, proximate analysis and purge were determined between treatments at any d aging.ConclusionThe results demonstrate that supplementation of ZN and RAC increased carcass yield. However, RAC inclusion negatively impacted WBS values unless aged for greater than 28 d. The data reveal that WBS differences exist between treatments. The molecular explanations for these differences should be defined to understand how ZN and RAC inclusion impact tenderness development.

Contribution of Protein Degradation and Sarcomere Length to Aged Pork Loin Warner-Bratzler Shear Force

ObjectivesPostmortem aging of fresh pork loins improves tenderness through protein degradation. Sarcomere length (SL) of postmortem muscle can vary between animals, and this could impact access and efficacy of proteinases to degrade proteins within, but not outside of the myofibril. The relationship between SL and protein degradation is not well documented in pork. Therefore, the objective of this experiment was to compare protein degradation of troponin-T with desmin and SL in aged pork loins over 21d.Materials and MethodsPaired sides of fresh pork loins (n = 20) were collected 1 d postmortem. Criteria for inclusion in the study were a pH between 5.85 and 6.10 and a visual color score (NPPC) between 3 and 4. Eight loin chops (2.54 cm) containing only the longissimus muscle were fabricated. Two chops from each pair of loins were aged for 1, 8, 14 or 21 d and immediately evaluated. After aging, chops were cooked to 68°C and Warner-Bratzler shear force (WBSF) was measured. Whole muscle proteins were solubilized from samples at each aging period (10mM sodium phosphate, pH 7.0 and 2% wt/vol sodium dodecyl sulfate). Abundance of degraded troponin-T (30 kDa) and intact desmin (55 kDa) in the whole muscle sample was determined by immunoblotting. Abundance of troponin-T degradation product and intact desmin was normalized by a reference sample on each gel. A helium-neon laser diffraction method was used to determine SL (total of 36 SL per sample were recorded). The distance between primary diffraction bands was used to calculate SL. Correlation coefficients were determined using PROC CORR of SAS 9.4 and significance determined by P < 0.05.ResultsOverall and across all days aging, SL was not strongly correlated to intact desmin (r = –0.198; P = 0.07) or troponin-T degradation (r = 0.236; P = 0.04). Troponin-T degradation was not detected at d1 in any samples but overall and across all days was highly correlated with WBSF (r = –0.671; P < 0.01)). Intact desmin was correlated with WBSF (r = 0.661; P < 0.01). Across all samples, SL was correlated with WBSF (r = –0.445; P < 0.01). Intact desmin and troponin-T degradation were correlated (r = –0.818; P < 0.01).Correlations within day of aging revealed that protein degradation was not significantly correlated with WBSF at d 1. In contrast, troponin-T degradation was correlated (P < 0.01) with WBSF at 8, 14, 21 d postmortem (r = –0.733, –0.641, and –0.772, respectively). Similarly, intact desmin was correlated (P < 0.01) with WBSF at 8, 14, and 21 d postmortem (r = 0.447, 0.553, and 0.824, respectively). SL was correlated (P < 0.01) with WBSF at each d postmortem (r = –0.445, –0.562, –0.714, and –0.512, respectively).ConclusionThe correlation results suggest that SL is consistently correlated with WBSF across aging periods and is more strongly correlated with WBSF early postmortem than protein degradation. After aging, troponin-T degradation and intact desmin demonstrate greater correlations with WBSF than SL. Finally, SL correlation to troponin-T and desmin were generally similar and not strong, suggesting that SL does not affect the efficacy of proteinases to degrade proteins within the myofibril differently than extra-myofibrillar proteins.

Utilization of Conventional and High Oleic Soybean Oil Oleogels Structured with Rice Bran Wax to Replace Pork Fat in Mechanically Separated Chicken-Based Bologna Sausage

ObjectivesThe objective of this study was to assess the quality and organoleptic attributes of bologna formulated with soybean oil/rice bran wax (RBW) oleogels made with either conventional (CO) or high oleic (HO) soybean oil as pork fat replacers.Materials and MethodsSix bologna treatments were manufactured using combinations of mechanically separated chicken and a lipid source to achieve a finished product fat target of 25.5%. The lipid sources used were: (1) 90% CO:10% RBW oleogel (C90); (2) 97.5% CO:2.5% RBW oleogel (C97.5); (3) 90% HO:10% RBW oleogel (H90); (4) 97.5% HO:2.5% RBW oleogel (H97.5), (5) liquid CO (CO); and (6) pork back fat (PF; control treatment). Treatments 1–5 were designed to replace 100% of the pork fat, which was approximately 41% of total fat. Treatment effects on emulsion stability, cook/chill yields, instrumental texture (Texture Profile Analysis [TPA] and incisor puncture) and color (CIE L*a*b*), lipid oxidation (TBARS), and sensory parameters were evaluated over a storage period of 98 d at 0–1°C. The experiment was replicated three times. Statistical analysis was conducted as a mixed model using JMP Pro 13.2.0 (SAS Institute, Cary, NC).ResultsNo treatment effects were observed for fat loss in emulsion stability, but CO resulted in significantly higher (P < 0.05) water loss, suggesting a less stable batter. L* instrumental color values revealed that PF was significantly darker (P < 0.05) and CO and C97.5 were significantly lighter (P < 0.05) than all other treatments. a* values were also highest (P < 0.05) for PF and lowest (P < 0.05) for CO and C97.5. b* values were highest (P < 0.05) for PF and lowest (P < 0.05) for C97.5. This agrees with sensory color analysis, which found color intensity to be highest (P < 0.05) in PF and lowest (P < 0.05) in CO. TPA parameters (firmness, cohesiveness, springiness, resilience, chewiness) were not significantly different (P > 0.05) among treatments. No treatment effects were observed for incisor peak force values (P < 0.05). There were no treatment effects for the following sensory parameters: sensory bologna aroma, other aroma, texture, moistness and other flavor. However, bologna flavor was significantly higher (P < 0.05) for PF than for CO, H90 and C97.5, but not than for H97.5 and C90. No storage time effects were observed in sensory analysis (P > 0.05). There were significant (P < 0.05) treatment effects on lipid oxidation, with TBARS values being lowest for PF and CO; however, none exceeded 0.29 mg malondialdehyde/kg over the length of the study, indicating acceptable oxidative stability for all treatments throughout the entire storage period. Microstructure analysis showed fat globule size was larger in PF and smaller in CO than in all other treatments, which could be partly responsible for the lower emulsion stability observed.ConclusionOleogels made with either high oleic or conventional soybean oil resulted in bologna products of similar quality and organoleptic properties, indicating they are easily interchangeable for this application. Use of high oleic soybean oil, however, would result in a product with a more favorable fatty acid profile. Pork fat replacement with liquid oil, while possible, could result in more unstable raw batters, less desirable color and lower flavor intensity.

Predicting aged pork quality using a portable Raman device

The utility of Raman spectroscopic signatures of fresh pork loin (1 d & 15 d postmortem) in predicting fresh pork tenderness and slice shear force (SSF) was determined. Partial least square models showed that sensory tenderness and SSF are weakly correlated (R² = 0.2). Raman spectral data were collected in 6 s using a portable Raman spectrometer (RS). A PLS regression model was developed to predict quantitatively the tenderness scores and SSF values from Raman spectral data, with very limited success. It was discovered that the prediction accuracies for day 15 post mortem samples are significantly greater than that for day 1 postmortem samples. Classification models were developed to predict tenderness at two ends of sensory quality as "poor" vs. "good". The accuracies of classification into different quality categories (1st to 4th percentile) are also greater for the day 15 postmortem samples for sensory tenderness (93.5% vs 76.3%) and SSF (92.8% vs 76.1%). RS has the potential to become a rapid on-line screening tool for the pork producers to quickly select meats with superior quality and/or cull poor quality to meet market demand/expectations.

Postmortem protein degradation is a key contributor to fresh pork loin tenderness

The objective of this study was to determine factors that influence tenderness independent of variation in pH, color, or marbling. To achieve the objective, 2 sample groups were chosen from a population of 159 pork loins aged 11 to 16 d. Predetermined ranges (ultimate pH, 5.54 to 5.86; marbling score, 1.0 to 3.0; percent total lipid, 1.61 to 3.37%) were defined for inclusion of individual loins in the study. The pork loins with the greatest ( = 12) and least ( = 12) Instron star probe values were assigned to 2 classification groups. The high star probe group had an average star probe that was 2.8 kg greater than the low star probe group (7.75 vs. 4.95 kg). Pork quality and sensory characteristics of pH, subjective and instrumental color values, cook loss, sensory tenderness, chewiness, juiciness, pork flavor, and off flavor were determined on fresh, never frozen pork chops. Lipid content, sarcomere length, myosin heavy-chain profile, and calpain autolysis were determined. Degradation of troponin-T, desmin, filamin, and titin were evaluated on the protein extracts from each sample. Pork loin pH, subjective color scores, Minolta L values, sarcomere length, and myosin heavy-chain composition were not different across groups. Chops from the low star probe group had a significantly greater marbling score (2.3 vs. 1.9) and lipid content (2.61 vs. 2.23%). Calpain-1 was completely autolyzed in both high and low star probe samples, demonstrating that calpain-1 potentially had been active in all samples. Low star probe whole-muscle protein extracts had more troponin-T ( < 0.01), desmin ( < 0.01), and filamin degradation ( < 0.01) than high star probe samples. Both classification groups showed degradation of titin. Remarkably, some high star probe samples still had observable intact bands of titin on SDS-PAGE gels. These results demonstrate that significant variation in instrumental tenderness is observed within a moderate pH range. Lipid content and proteolysis both appear to contribute to this variation.

Proteomic features linked to tenderness of aged pork loins

There is considerable evidence that the protein component of fresh pork makes a major contribution to tenderness. In particular, the proteomic profile can be linked to postmortem events including pH decline, tissue oxidation, and protein degradation. The objectives for this study were to determine differences in sarcoplasmic proteomes that contribute to tenderness variation in aged pork longissimus dorsi muscles (LM). A defined set of pork loins selected to be similar in pH, color, and lipid yet different in tenderness were used. Pork loins were assigned to tenderness groups based on their star probe values; a high star probe group (HSP; n=12 mean star probe 7.75 kg) and low star probe group (LPS; n=12 star probe 4.95 kg) Samples were selected for proteomic experiments based on star probe values, and selected samples were within specified ranges for ultimate pH (5.54-5.86), marbling score (1.0-3.0), and percent total lipid (1.61-3.37%). Two-dimensional difference in gel electrophoresis (2D-DIGE) and mass spectrometry were used to examine sarcoplasmic protein abundance and potential modifications. Proteins spots that were significantly different across groups were selected for identification. Results from 2D-DIGE showed that HSP samples had significantly more abundant metabolic, stress response, and regulatory proteins in the sarcoplasmic fraction compared with LSP samples. The stress response protein peroxiredoxin-2 was more abundant in HSP samples as determined by 2D-DIGE ( ≤ 0.01; 2 spots) and western blot assay ( = 0.02). Low star probe samples showed significantly more degradation of the structural protein desmin in 2D-DIGE ( < 0.01) and western blot assay ( < 0.01). These results demonstrate that extreme proteolytic differences influenced measured tenderness of LSP and HSP samples and that soluble desmin and peroxiredoxin-2 may be used as biomarkers to differentiate between tough and tender aged pork products.

Color stability and sensory characteristics of fresh and enhanced pork loins from immunologically castrated barrows

Our objective was to evaluate color changes during storage of fresh pork chops and enhanced and nonenhanced loin quality from anti-gonadotropin-releasing factor (Improvest) immunologically castrated (IC) barrows. In study 1, treatments evaluated were IC barrows, IC barrows fed ractopamine (IC+RAC), physically castrated (PC) barrows, intact males (IM), and gilts. Fresh loins were evaluated for sensory characteristics and instrumental tenderness including both Warner-Bratzler Shear force (WBSF) and star probe force. In study 2, treatments evaluated were IC barrows fed 0.55% and 0.65% standard ileal digestible (SID) lysine and PC barrows fed 0.55% SID lysine. Loin chops were displayed for 7 d, and color was evaluated. The remaining loin was halved, and one half was enhanced with a 3.5% salt and phosphate solution. Enhanced loins were evaluated for sensory characteristics and instrumental tenderness. In both studies, pen served as the experimental unit for all traits measured. Data from individual animals were averaged by pen and analyzed, per study, as a 1-way ANOVA using the MIXED procedure of SAS. In study 1, there were no differences ( 0.05) between treatments for juiciness, tenderness, chewiness, or off-flavor. Intact males had the most intense ( 0.05) boar aroma. Gilts had the most intense ( < 0.05) pork flavor, whereas IM had the least intense pork flavor; all other treatments were intermediate. Tenderness (WBSF) was similar between treatments at 1 d of aging; however, at 7, 14, and 21 d of aging, loins from IC barrows were more tender ( 0.05) than those from gilts, IM, and IC+RAC but were similar ( 0.05) to those from PC. In study 2, discoloration of fresh loin chops during storage was similar ( 0.42) between PC and IC barrows. Chops from enhanced loins were more tender and juicy but had more off-flavor than nonenhanced loins ( 0.01). Star probe and WBSF were also reduced ( 0.01) in enhanced loins compared with nonenhanced loins. Sensory characteristics and tenderness were not different between treatments of IC and PC barrows ( > 0.05), and there were no interactions of enhancement with castration treatments. These data suggest that immunological castration does not negatively impact the color stability, sensory characteristics, or tenderness of enhanced or nonenhanced pork loins.

The impact of dietary fat withdrawal on carcass iodine value, belly characteristics, and changes in body fat over time

The inclusion of unsaturated fats in pig diets has raised issues related to pork carcass fat quality. The objective of this experiment was to understand how withdrawal from the diet of unsaturated dietary fat before slaughter impacts the composition of jowl fat during the growth cycle and at market. Fifty individually housed pigs (PIC 337 × C22/29; initial BW = 59.3 ± 0.55 kg) were allotted based on sex and initial BW to 10 treatments for an 82-d experiment as follows: 3 dietary fat withdrawal times before slaughter (21, 42, or 63 d) by 3 dietary fat unsaturation loads (DFUL), which includea high intake of unsaturated fatty acids supplied through an inclusion of 5% corn oil (HIGH), a high intake of a mixture of saturated and unsaturated fatty acids supplied through an inclusion of 5% animal-vegetable blend (MED), and a moderate intake of unsaturated fatty acids supplied through an inclusion of 2.5% corn oil (LOW). Pigs were weighed and jowl adipose samples were collected on d 0, 21, 42, and 63 and at harvest on d 82. Data were analyzed using PROC MIXED with treatment and sex as fixed effects. At market (d 82), increasing the withdrawal of dietary fat further away from market increased 18:1 (P = 0.045) and tended to increase 14:0 concentrations (P = 0.054). It also significantly decreased 18:2 (P < 0.001) and tended to decrease 18:3 concentrations (P = 0.081). A HIGH DFUL resulted in the greatest 18:2 concentrations in jowl fat followed by LOW; MED resulted in the lowest 18:2 levels (P < 0.001). Dietary fat withdrawal before market significantly reduced carcass iodine value (IV) measured at d 82 (P = 0.006). In conclusion, elevated 18:2 intake makes lowering carcass IV in the depot fat very difficult and may take as long as 61 d. The withdrawal of unsaturated dietary fat apparently altered the fat depot to be more reflective of fat synthesized de novo, resulting in a more saturated depot fat. Importantly, this alteration of deposited fat composition did not translate into improved belly firmness, depth, weight, or fat color.

A comparison of slice characteristics and sensory characteristics of bacon from immunologically castrated barrows with bacon from physically castrated barrows, boars, and gilts

The objectives were to compare slice characteristics and sensory attributes of bacon from immunologically castrated (IC) barrows with bacon from other sexes using a trained sensory panel. Bacon was obtained for sensory evaluation from 3 experiments. In Exp. 1, trimmed and squared bellies (n=180) of IC barrows, IC barrows fed ractopamine hydrochloride (IC+RAC), physically castrated (PC) barrows, intact males (IM), and gilts were used. Data were analyzed as a general linear mixed model and pen (n=48) served as the experimental unit. Treatment (sex or diet) was a fixed effect in all 3 experiments. In Exp. 2, untrimmed, natural fall bellies (n=96) from IC and PC barrows fed 0 or 30% or a withdrawal distillers dried grains with solubles (DDGS) program when slaughtered at 5 wk after the second dose (25 wk of age) were used. In Exp. 3, untrimmed, natural fall bellies (n=96) from IC and PC barrows fed the same experimental diets as in experiment 2 but slaughtered at 7 wk after the second dose (27 wk of age) were used. Data from Exp. 2 and 3 were analyzed as a 2×3 factorial arrangement in a randomized complete block design and pen was the experimental unit. Bellies from all 3 experiments were processed using the same protocols. In Exp. 1, IM had the greatest (P<0.0001) boar aroma and flavor scores among all treatments. No differences were detected among the other treatment groups for boar aroma or flavor. Intact males had the least (P<0.0001) desirable cured bacon aroma and flavor among all treatments. No differences were detected among the other treatment groups for bacon aroma or flavor. There were no differences in bacon aroma or off-flavor between IC and PC barrows slaughtered at 5 wk after the second dose regardless of DDGS feeding program. Bacon from PC barrows was saltier (P<0.01) than bacon from IC barrows when slaughtered at 5 wk after the second dose. There were no differences in bacon aroma, off-aroma, bacon flavor, or saltiness between IC and PC barrows slaughtered at 7 wk after the second dose regardless of DDGS feeding program. Total slice area of bacon slices from IC barrows slaughtered at 5 wk after the second dose were less (P<0.01) than PC barrows, but the differences diminished (P=0.16) when slaughtered at 7 wk after the second dose. Overall, panelists successfully detected boar odor and flavor in Exp. 1. Immunological castration was as effective as physical castration at eliminating boar aroma and boar flavor in bacon even when feeding differing DDGS feeding programs or when slaughtered at 5 or 7 wk after the second dose.

Impact of dietary fat source and concentration and daily fatty acid intake on the composition of carcass fat and iodine value sampled in three regions of the pork carcass

The increased inclusion of unsaturated fats in pig diets has raised issues related to pork carcass fat quality. The objective of this experiment was to more precisely measure how differing levels of daily fatty acid intake alters the fatty acid composition in 3 different fat depots. A total of 42 gilts and 21 barrows (PIC 337×C22/29) with an average initial weight of 77.80±0.38 kg were allotted randomly based on sex and BW to 7 treatments: 3 and 6% of each of tallow (TAL; iodine value [IV]=41.9), choice white grease (CWG; IV=66.5), or corn oil (CO; IV=123.1) and a control (CNTR) corn-soybean meal-based diet with no added fat. Pigs were individually housed to allow accurate measurement of individual feed intake, in particular, daily dietary fatty acid and energy intake. Fat samples were collected from the jowl, belly, and loin at slaughter. Diet and carcass fat samples were analyzed for IV. Belly weights were recorded at slaughter along with a subjective belly firmness score (1=firmest to 3=least firm). Carcass lipid IV was increased (P<0.001) by increasing the degree of unsaturation of the dietary fat source (66.8, 70.3, and 76.3 for TAL, CWG, and CO, respectively). Carcass lipid IV for TAL and CWG was not affected (P>0.05) by inclusion levels; however, carcass lipid IV was greater (P<0.001) in pigs fed 6 than 3% CO (80.0 vs. 72.6), and carcasses of gilts had greater IV (P<0.001) than carcasses of barrows (71.5 vs. 69.1). Increasing the level of TAL and CO but not CWG from 3 to 6% decreased the apparent total tract digestibility of GE, resulting in a source×level interaction (P<0.05). Dietary fat source had no effect (P≥0.66) on apparent total tract digestibility of either DM or GE, but feeding 6% dietary fat increased G:F (P=0.006) over pigs fed 3% fat (0.358 vs. 0.337). Of all the fatty acids measured, only linoleic acid intake presented a reasonable coefficient of determination (R2=0.61). Overall, IV product (IVP) was approximately equal to linoleic acid intake as a predictor of carcass IV (R2=0.93 vs. R2=0.94). When inclusion of dietary fat and PUFA intake increased, IVP placed more emphasis on the dietary fat inclusion level rather than the dietary fat composition. Linoleic acid intake corrected the overemphasis placed on dietary fat inclusion by IVP. To conclude, linoleic acid intake showed a strong relationship with carcass IV and can be used as a predictor.

Effects of preslaughter feed withdrawal time on finishing pig carcass, body weight gain, and food safety characteristics in a commercial environment

The effects of feed withdrawal time before slaughter on finishing pig carcass composition were evaluated in 2 studies. In Exp. 1, 728 pigs (BW = 128.9 ± 1.2 kg) were allotted to 1 of 4 treatments in a randomized design with number of pigs per pen and location within barn balanced across treatment. The 4 treatments were feed withdrawal times of 8, 24, 36, or 48 h and there were 12 replicate pens per treatment. Before feed withdrawal, pigs were fed a standard corn-soybean meal diet containing dried distillers grains with solubles (DDGS), bakery coproducts, and 5.0 mg/kg ractopamine HCl. Feed withdrawal time decreased (linear; P < 0.02) live weight, HCW, and backfat while increasing percentage yield (quadratic; P < 0.01) and fat-free lean index (FFLI; linear; P < 0.001). In Exp. 2, 843 pigs (BW = 125.4 ± 1.6 kg) were used to determine the impact of feed withdrawal on growth, carcass, blood lactate, and meat quality. There were 4 treatments: withholding feed for 8, 12, 24, or 36 h, with 10 replicates per treatment. Pigs were fed a common corn-soybean meal-based diet containing 20% DDGS and 5.0 mg/kg ractopamine HCl. Withholding feed decreased (linear; P < 0.001) live weight, ultimately resulting in decreased (P < 0.01) HCW. There were no differences in FFLI or backfat, but percentage yield (linear; P < 0.001) increased with longer withdrawal times. Carcass contaminations by stomach contents escaping from the oral cavity after shackling (leaking ingesta) or visible fecal contamination of the exterior of the carcass (runny bung) were also measured. Although withholding feed did not affect runny bung, it increased (linear; P < 0.001) the incidence of leaking ingesta, whereas blood lactate, visual color score, and purge loss were unaffected. Withholding feed increased 45-min pH (quadratic; P > 0.02) and ultimate pH (linear; P < 0.01) and increased (quadratic; P < 0.03) visual marbling score. Withholding feed decreased (linear; P < 0.001) feed intake, resulting in feed savings of up to 3 kg/pig. Although several heavyweight pigs were removed before trial commencement and the variable number of remaining pigs per pen may have influenced the response to feed withdrawal, the present data indicates that finishing pigs can experience between 24 and 36 h of feed withdrawal without negatively affecting carcass composition. However, the increased incidence of leaking ingesta beyond 12 h of feed withdrawal is concerning.

Control of Salmonella enterica Typhimurium in chicken breast meat by irradiation combined with modified atmosphere packaging

Salmonella is one of the leading causes of human foodborne illnesses originating from meat and poultry products. Cross-contamination of Salmonella from raw to cooked products continues to be problematic in the food industry. Therefore, new intervention strategies are needed for meat and poultry products. Vacuum or modified atmosphere packaging (MAP) are common packaging techniques used to extend the shelf life of meat products. Irradiation has been well established as an antibacterial treatment to reduce pathogens on meat and poultry. Combining irradiation with high-CO(2)+CO MAP was investigated in this study for improving the control of Salmonella enterica Typhimurium on chicken breast meat. The radiation sensitivities (D10-values) of this pathogen in chicken breast meat were found to be similar in vacuum and in high-CO(2)+CO MAP (0.55 ± 0.03 kGy and 0.54 ± 0.03 kGy, respectively). Irradiation at 1.5 kGy reduced the Salmonella population by an average of 3 log. Some Salmonella cells survived in both vacuum and high-CO(2) + CO MAP through 6 weeks of refrigerated storage following irradiation. This pathogen also grew in both vacuum and MAP when the product was held at 25°C. This study demonstrated that irradiation is an effective means of reducing Salmonella on meat or poultry, but packaging in either vacuum or MAP had little impact during subsequent refrigerated storage.

Effects of ractopamine supplementation and postmortem aging on longissimus muscle palatability of beef steers differing in biological type

Effects of ractopamine hydrochloride (RAC) supplementation and postmortem aging on palatability of beef from steers differing in biological type were evaluated using LM samples from British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 98/type). Equal numbers of steers within each type were assigned to treatments of 0 or 200 mg.steer(-1).d(-1) of RAC fed during the final 28 d of the finishing period. Warner-Bratzler shear force (WBSF) was measured at 3, 7, 14, and 21 d postmortem, and trained sensory panel (TP) evaluation was conducted using LM samples aged for 14 d postmortem. A RAC x type interaction (P = 0.006) was detected for WBSF. Within each type, steers fed RAC produced steaks with greater (P < 0.05) WBSF values than steaks from control steers; however, the magnitude of the effect of RAC on WBSF was more pronounced among Brahman cross-breds (5.53 vs. 4.96 +/- 0.10 kg) than among Continental crossbred (4.16 vs. 3.96 +/- 0.10 kg) and British steers (4.10 vs. 3.75 +/- 0.10 kg). The effect of RAC on WBSF, though diminished slightly by aging (mean WBSF difference: 3 d = 0.49 kg; 21 d = 0.24 kg), was not completely mitigated by 21 d of postmortem storage (P(RAC x AGE) = 0.16). Steers fed RAC produced steaks that received lower (P < 0.05) TP ratings for tenderness (8.09 vs. 8.95 +/- 0.18) and juiciness (7.41 vs. 8.07 +/- 0.16 kg), along with slightly lower (P = 0.06) ratings for beef flavor (6.67 vs. 6.93 +/- 0.10 kg), compared with steaks from unsupplemented steers, regardless of biological type. Among the 3 biological types, Brahman crossbred cattle produced steaks with the greatest (P < 0.05) WBSF values at each aging period; WBSF values for steaks from British and Continental type steers did not differ (P > 0.05) at any aging time. Sensory panel ratings of tenderness, juiciness, and beef flavor were greatest (P < 0.05) for steaks from British steers, and least (P < 0.05) for steaks produced by Brahman-type steers. Results from this study suggest that RAC supplementation slightly decreases LM tenderness (WBSF and TP) of British, Continental crossbred, and Brahman cross-bred steers, and that the effect of RAC on WBSF may be more pronounced in steaks from Brahman crossbred cattle than among stenks from Continental type or British steers.

Influence of lipid content on pork sensory quality within pH classification1

The objective of this project was to determine the contribution of lipid content to textural and sensory properties of fresh pork within defined pH classifications. Pigs (n = 1,535; from 248 sires and 836 dams) from the 1991, 1992, and 1994 National Barrow Show Sire Progeny Test were used in this study. The test included purebred Berkshire (107), Chester White (113), Duroc (249), Hampshire (220), Landrace (165), Poland China (101), Spotted (181), and Yorkshire (399) barrows (901) and gilts (634). Diets were uniform across breeds within test. The halothane (Hal 1843) genotype (1346 NN and 189 Nn) was determined. Pigs were slaughtered at 105 kg of BW, and samples of the LM were obtained from each carcass at the 10th rib. Star probe, sensory traits, and lipid content were determined on the LM from each pig. A pH classification of LM was assigned as follows: class A, > 5.95, n = 186; class B, > or = 5.80 to 5.95, n = 236; class C, > or = 5.65 to 5.80, n = 467; class D, > or = 5.50 to 5.65, n = 441; class E, < 5.50, n = 205. Data were analyzed using a mixed linear model including pH classification, test, sex, halothane genotype, breed, and breed x sex interaction as fixed effects, with sire and dam within breed included as random effects. Correlations were determined within pH class. Lipid content was a significant source of variation for models predicting star probe values in class C and D and for chewiness in class B, C, and D. Increasing lipid content tended to increase sensory tenderness in pH class D. Sensory tenderness was not affected by lipid content in pH class A, B, or E. Lipid content was not a significant source of variation for juiciness scores within any pH class. Intramuscular lipid is correlated with sensory texture traits primarily in classes C and D. Within class C and D, correlations indicate that increasing lipid content is associated with high sensory tenderness, low sensory chewiness, and low star probe values. It is concluded that lipid content is a small source of variation in texture and tenderness of pork loin with pH between 5.80 and 5.50, but not at a greater or lesser pH.

Effects of preslaughter management on the quality of carcasses from porcine stress syndrome heterozygous market hogs

The objectives of this study were to determine whether two preslaughter management treatments, rest and mixing, influence the muscle quality of porcine stress syndrome (PSS) heterozygous (Nn) market hogs and to verify the expected quality characteristics of carcasses produced from PSS-normal (NN) and PSS-susceptible (nn) animals. Twenty-nine Nn, 14 NN, and 9 nn market hogs were randomly assigned to preslaughter handling treatments. One-half of the animals in each genotype group received 16 h of rest before slaughter, and the remaining pigs were slaughtered immediately upon arrival at the Iowa State University Meat Laboratory. Within each group, half of the Nn animals were mixed with unfamiliar pigs during transport and lairage. Length, backfat, and loin muscle area (LMA) were not affected by mixing and rest treatment. The carcasses from nn pigs had less fat (P < .05) measured at the 10th rib (off midline) and last lumbar vertebra (midline) and possessed larger LMA than carcasses from NN pigs. Heterozygous pigs were intermediate for most carcass traits. Carcass pH values among heterozygous groups were not significantly different, except that the rested animals had higher ultimate pH values (P < .01) and higher 45-min pH values. Resting had no effect on pH of NN or nn pigs. The 45-min pH values of nn carcasses were lower (P < .01) than those of NN carcasses, but ultimate pH values were similar. Values of unrested Nn animals were between those of NN and nn genotypes but with rest approached values of NN pigs. Loin muscle Minolta-Y and Hunter-L values from unrested Nn animals were higher ( P < .05) than those of rested Nn animals. Mixing did not influence these traits. The longissimus muscle lipid content was not influenced by treatment but differed among genotypes (P < .01). Glycogen levels of rested Nn animals tended to be lower than those of NN animals and approached those of nn pigs. Mixing of Nn animals resulted in higher (P < .05) chewiness scores of cooked loin chops. No significant cooking loss or InstronTM tenderness differences were observed between the PSS-Nn treatment groups. Even though 16 h of rest before slaughter improved the color and water-holding capacity of Nn pigs, effects were small and were much less than those that were due to the PSS gene.

Nutrient composition and sensory attributes of cooked ground beef: effects of fat content, cooking method, and water rinsing

Ground beef with 10%, 20%, and 30% fat was shaped into patties or crumbled and cooked by panfrying, panbroiling, or microwaving. After cooking, half of the crumbles were water rinsed. Samples were analyzed for yield, energy, moisture, protein, total lipid, cholesterol, iron, and zinc. In other experiments, cooked crumbled samples were analyzed for vitamin B-12 content and sensory qualities. Effects of cooking method on total lipid and cholesterol levels were generally small. Initial fat level significantly affected total lipid content in cooked ground beef; cooked samples with 10% initial fat contained slightly less total lipid than those with 20% or 30% initial fat. Rinsing with warm water significantly reduced fat and increased the moisture content of cooked ground beef crumbles. Protein, iron, zinc, and vitamin B-12 were well retained during rinsing. We conclude that consumers can achieve a significant reduction in fat content, without substantial losses in protein, iron, zinc, or vitamin B-12, if they water rinse cooked ground beef crumbles. The flavor and texture of the cooked ground beef crumbles are altered somewhat by rinsing. Acceptance in mixed recipes was not determined.

Cholesterol content of broiler breast fillets heated with and without the skin in convection and conventional ovens

Six treatment combinations for the heating of broiler breast fillets were investigated: three skin variables (heated and analyzed with skin, heated with and analyzed without skin, and heated and analyzed without skin) and two heating systems (convection broiling and conventional roasting). Matched broiler breast fillets were analyzed raw or breaded and heated to 82 C. Raw and cooked samples of meat, skin, and meat with skin were analyzed for moisture, fat, and cholesterol contents. In the raw state, samples of meat with skin contained greater moisture and fat contents, but similar cholesterol contents, when compared with samples of meat alone. Fillets heated by convection broiling had greater cooking losses but shorter heating times compared with conventionally roasted samples. Fillets with the skin removed before or after heating contained more moisture, less fat, and less cholesterol than samples cooked and analyzed with the skin present.

Relationship of selected quality characteristics and the cholesterol and sodium content of turkey

Turkey breast roasts (pectoralis major muscles) were heated in three oven types to one of two internal endpoint temperatures. The relationship of cook time and rate, cook losses, proximate analysis, fat content of the cook drip, and percent cholesterol in the cook drip with the cholesterol and sodium content of the tissue was studied. On a wet-weight basis, the cholesterol content of the cooked turkey was not significantly correlated to either the fat content or the moisture content. Drip loss and total cook loss were positively correlated with cholesterol content. On a dry-weight basis, sodium content was significantly correlated with evaporative loss and total cooking loss.

Quality characteristics, cholesterol, and sodium content of turkey as affected by conventional, convection, and microwave heating

Six treatment combinations for evaluation of quality characteristics, sodium, and cholesterol content of turkey breast roasts were studied: three oven types (conventional, convection, and microwave) and two internal endpoint heating temperatures (77 C and 82 C). The microwave oven was the most energy efficient, and the conventional oven was the least efficient. Overall, drip loss was highest in the microwave oven, and heating to 82 C increased total cooking loss. Cook drip from the microwave oven contained less fat but the same amount of cholesterol as cook drip from the other two oven types. Instron shear values were not affected by oven type or internal endpoint temperature. Generally, when comparing raw to cooked samples, heating increased (concentrated) the cholesterol content and decreased the sodium content of the turkey. Cholesterol content of the heated roasts was not affected by type of oven; however, heating to the higher internal endpoint temperature increased (concentrated) the cholesterol. Sodium content was not affected by oven type or internal endpoint heating temperature. Cholesterol and sodium retentions of the roasts after heating were 96 and 64%, respectively, when averaged over the three oven types.