Inclusion of Beef Heart in Ground Beef Patties Alters Quality Characteristics and Consumer Acceptability as Assessed by the Application of Electronic Nose and Tongue Technology

Consumer purchasing of beef is often driven by the trinity of flavor, palatability, and convenience. Currently, beef patties in the United States are manufactured with fat and lean trimmings derived from skeletal muscles. A reduction in total beef supply may require the use of animal by-product utilization such as variety meats to achieve patty formulations. The current study aimed to assess textural, color, and flavor characteristics in addition to volatile compounds through electronic technology, e-nose and e-tongue, of ground beef patties formulated with beef heart. Ground beef patties were manufactured with 0%, 6%, 12%, or 18% beef heart, with the remainder of the meat block being shoulder clod-derived ground beef. Patties (n = 65/batch/treatment) within each batch (n = 3) with each treatment were randomly allocated to cooked color (n = 17/batch/treatment), Allo-Kramer shear force (AKSF; n = 17/batch/treatment), texture profile analysis (TPA; n = 6/batch/treatment), cooking loss (n = 17/batch/treatment), consumer panel (n = 3/batch/treatment), e-nose (n = 1/batch/treatment), and e-tongue (n = 1/batch/treatment) analysis groups. Patties containing beef heart did not require additional cooking time (p = 0.1325) nor exhibit greater cooking loss (p = 0.0803). Additionally, inclusion rates of beef heart increased hardness (p = 0.0030) and chewiness values (p = 0.0316) in TPA, were internally redder (p = 0.0001), and reduced overall liking by consumer panelists (p = 0.0367). Lastly, patties containing beef heart exhibited greater red-to-brown (p = 0.0003) and hue angle (p = 0.0001) values than control patties. The results suggest that beef heart inclusion does alter ground beef quality characteristics and consumer acceptability.

Feeding Ractopamine Improves the Growth Performance and Carcass Characteristics of the Lard-Type Mangalica Pig

Mangalica pigs are gaining popularity within the U.S. as a niche breed, given their reputation for superior-quality pork. However, slow growth rates, a poor lean yield, and excessive adiposity limit the widespread adoption of Mangalica. To determine if feeding the metabolic modifier, ractopamine hydrochloride (RAC), would improve growth performance without impairing pork quality in the Mangalica, pigs were fed either 0 or 20 mg per kg RAC for 21 days. At 24 h postharvest, pork quality and carcass composition measurements were recorded; then, primal cuts were fabricated and assessed. RAC increased ADG (p < 0.04) and gain efficiency (p < 0.03) by 24% and 21%, respectively. RAC increased Loin Eye Area (p < 0.0001) by 21% but did not impact the 10th rib fat depth (p > 0.90) or marbling score (p > 0.77). RAC failed to alter any primal cut weights. Feeding RAC lowered b* values (p < 0.04) and tended to lower L* values (p < 0.08) while not affecting a* values (p > 0.30), suggesting RAC darkened loin color. Finally, RAC decreased cook yield percentage (p < 0.02) by 11% without impacting Warner-Bratzler Shear Force (p > 0.31). These data support the hypothesis that feeding RAC to Mangalica improves growth performance without impairing pork quality in this breed.

Influence of Sous Vide Cooking on Ground Beef Patties

With rising consumer demand for fast-food options, quick-service restaurants are constantly developing new menu items to attract consumers. Sous vide cookery has become popular for the in-home and fine dining consumer but has not been considered the first cooking option for quick service applications. Therefore, ground beef patties were manufactured to measure the influence of sous vide cooking time on the patty characteristics of moisture, color, and objective tenderness. Patties were randomly assigned a sous vide cooking time of 30, 60, or 90 min and then grilled to an internal temperature of 71.1 °C. Patties sous vide cooked for 30 min exhibited the greatest (p < 0.05) cook loss, Allo-Kramer Shear Force (AKSF) and were darker (L*) than patties sous vide cooked for 60 or 90 min. Additionally, neither internal redness, calculated spectral values of chroma, hue angle, or red-to-brown differed (p > 0.05) regardless of sous vide cooking time. Sous vide cooking duration prior to grilling the ground beef patties altered the moisture, color, and objective texture characteristics of ground beef patties.

Influence of Hempseed Meal on Fresh Goat Meat Characteristics Stored in Vacuum Packaging

The objective of this study was to determine the influence of hempseed meal (HSM) on goat meat characteristics. Goats (N = 10/treatment) were allocated to a diet concentration (0, 10, 20, or 30%) of HSM, fed for 60 days, and harvested. Carcass measurements were collected after chilling, and subsequently fabricated into wholesale subprimals. From the subprimals of the shoulder and leg, steaks were cut 2.54 cm thick, vacuum packaged, and assigned to laboratory methods: cook yield, instrumental color, lipid oxidation, microbial spoilage, and instrumental tenderness. HSM did not alter (p > 0.05) carcass characteristics, microbial spoilage, cook loss, or the thiobarbituric acid reactive substance (TBARS). However, a decrease in objective tenderness measurements (p < 0.05) was observed with greater concentrations of HSM supplementation in the diet. Instrumental surface color values for lightness (L*) indicated that steaks became lighter and less red (a*) as storage time increased (p < 0.05). Results suggest that HSM and storage time do not alter some goat meat traits, but HSM or storage time separately may influence goat meat quality. HSM may be an effective feed ingredient that does not alter carcass quality or meat yield.

Extended Storage of Beef Steaks Using Thermoforming Vacuum Packaging

Extended storage duration often results in negative quality attributes of fresh or frozen beef steaks. This study focused on evaluating the fresh and cooked meat quality of beef steaks stored using vacuum packaging for 63 days. Steaks 2.54 cm thick were packaged into one of three thermoforming films VPA (250 µ nylon/EVOH/enhanced polyethylene coextrusion), VPB (250 µ nylon/EVOH/enhanced polyethylene coextrusion), or VPC (125 µ nylon/EVOH/enhanced/polyethylene coextrusion). Steaks placed in VPA were lighter (L*) and redder (a*) in surface color (p < 0.05) as the display period increased, whereas steaks packaged in VPB and VPC became darker. Yellowness, hue angle (Hue°), and chroma (C*) values were greater (p < 0.05) in steaks using VPC film as the storage period increased. Calculated spectral values of red to brown were greater (p < 0.05) for steaks in VPA and VPB than in VPC. However, steaks placed in VPC films contained greater (p < 0.05) forms of metmyoglobin and oxymyoglobin and lower calculated relative values of deoxymyoglobin. In addition, packaging treatment altered (p > 0.05) lipid oxidation, but storage time had a greater (p < 0.05) influence on purge loss, cook loss, and Warner-Bratzler shear force (WBSF). Current results suggest that the use of vacuum packaging for extended storage of beef steaks (>60) days is plausible.

Characterization of Growth Performance, Pork Quality, and Body Composition in Mangalica Pigs

European heritage breeds, such as the Blonde (B), Red (R), and Swallow-bellied (SB) Mangalica pig, display an extreme propensity to fatten and are reputed to produce superior quality pork. This suggests that Mangalica pork should command a higher price, and the Mangalica is a candidate breed to target niche markets within the United States. Our objectives were to test this hypothesis by (1) directly comparing growth performance and carcass merit of purebred Yorkshire (Y), B, R, and SB Mangalica pigs to identify the best breed for adoption, and (2) comparing indices of pork quality in purebred R, Y, and crossbred (R × Y) pigs to determine if crossbreeding represented a viable alternative to the adoption of purebred Mangalica. Daily feed intake, average daily gain (ADG), and feed efficiency were highest in Y and lowest in SB pigs with B and R ranked intermediately (p < 0.001). Backfat thickness was greatest in B and lowest in Y with R and SB ranked intermediately (p < 0.001). Marbling score was greatest in R pigs and lowest in Y pigs with B and SB ranked intermediately (p < 0.01). In contrast, loin eye area (LEA) was greatest in Y pigs compared to B, R, and SB (p < 0.001). Indices of meat quality were then compared in R, R × Y, and Y pigs. Backfat thickness and marbling scores were greater in R than R × Y and Y pigs (p < 0.001) while LEA was greater in Y than R × Y and R pigs (p < 0.001). Loin and ham ultimate pH, color, and firmness scores were significantly greater in R than R × Y or Y pigs (p < 0.05). Meanwhile, cook loss was significantly less in R than Y pigs (p < 0.007) while Warner-Bratzler Shear Force (WBS) was not different in chops between groups (p < 0.11). These data indicate that though Mangalica exhibit poorer growth performance, Mangalica pork exhibits superior pork quality attributes, suggesting that higher price points for Mangalica pork in niche markets are justified.

Determination of Optimal Harvest Weight for Mangalica Pigs Using a Serial Harvest Approach to Measure Growth Performance and Carcass Characteristics

Mangalica pigs are a popular niche breed given their reputation for superior pork quality. However, growth and carcass parameters for this breed are poorly documented. To better characterize optimal harvest weights for the Mangalica, a growth trial was conducted whereby pigs (n = 56) were randomly distributed across stratified harvest weights (50, 57, 68, 82, 93, 102, 127 kg) in a completely randomized design. Pigs were fed standard finisher rations with individual daily feed intakes and weekly body weights recorded for all animals. At 24 h postmortem, carcasses were split and ribbed with marbling and loin eye area (LEA) measured at the 10th rib. Primal cuts were fabricated and individually weighed. Fat back was separated from the loin and weighed. As expected, live weight significantly increased across the weight class (p < 0.0001). ADG was similar across classes up to 82 kg live weight, before steadily declining with increasing weight class (p < 0.0025). Likewise, feed efficiency did not differ between classes until weights heavier than 82 kg (p < 0.03). LEA significantly increased by class up to 82 kg and then plateaued as harvest weight increased further (p < 0.003). Marbling score significantly increased with increasing weight class up to 102 kg, where they then plateaued (p < 0.04). Fat back dramatically increased across all weight classes (p < 0.0001) despite negligible increases in LEA or marbling after 102 kg. Primal cut weights for the ham (p < 0.0001), loin (p < 0.0001), Boston butt (p < 0.0001), shoulder (p < 0.0001), and belly (p < 0.0001) all significantly increased with increasing live weight though significant fat deposition contributed to this gain. These data suggest an optimal harvest weight occurs between 82 to 102 kg, while offering little objective justification for harvesting Mangalica pigs at heavier live weights.

Classification and Feature Extraction Using Supervised and Unsupervised Machine Learning Approach for Broiler Woody Breast Myopathy Detection

Bioelectrical impedance analysis (BIA) was established to quantify diverse cellular characteristics. This technique has been widely used in various species, such as fish, poultry, and humans for compositional analysis. This technology was limited to offline quality assurance/detection of woody breast (WB); however, inline technology that can be retrofitted on the conveyor belt would be more helpful to processors. Freshly deboned (n = 80) chicken breast fillets were collected from a local processor and analyzed by hand-palpation for different WB severity levels. Data collected from both BIA setups were subjected to supervised and unsupervised learning algorithms. The modified BIA showed better detection ability for regular fillets than the probe BIA setup. In the plate BIA setup, fillets were 80.00% for normal, 66.67% for moderate (data for mild and moderate merged), and 85.00% for severe WB. However, hand-held BIA showed 77.78, 85.71, and 88.89% for normal, moderate, and severe WB, respectively. Plate BIA setup is more effective in detecting WB myopathies and could be installed without slowing the processing line. Breast fillet detection on the processing line can be significantly improved using a modified automated plate BIA.

Vacuum Packaging Maintains Fresh Characteristics of Previously Frozen Beef Steaks during Simulated Retail Display

The impact of frozen storage on beef steaks prior to the retail setting may result in changes to the quality and safety of the packaged meat. Therefore, the objective of the current study was to evaluate fresh characteristics on previously frozen steaks during a simulated retail display. Steaks were allocated to one of three packaging treatments (MB, MDF, MFS) and stored frozen (−13 °C) for 25 days in the absence of light. After thawing, steaks were stored in a lighted retail case at 3 °C and evaluated for instrumental surface color, pH, purge loss, lipid oxidation, and microbial spoilage organisms throughout the 25-day fresh display period. There was an increase (p < 0.05) for aerobic plate counts and lipid oxidation from day 20 through 25 on steaks packaged in MFS and MDF, respectively. Steaks packaged in MB were redder (p < 0.05) and more vivid (C*) as storage time increased. Whereas lipid oxidation was greater (p < 0.05) throughout the entire display for steaks packaged in MFS and MDF. It is evident that barrier properties of MB limiting oxygen exposure of the steak preserved fresh meat characteristics after frozen storage. Results from the current study suggest that vacuum packaging films can aid in retarding detrimental effects caused by frozen storage after placing the steaks in fresh retail conditions.

Sampling Adipose and Muscle Tissue following Post-Harvest Scalding Does Not Affect RNA Integrity or Real-Time PCR Results in Market Weight Yorkshire Pigs

Improving production efficiency while enhancing pork quality is pivotal for strengthening sustainable pork production. Being able to study both gene expression and indices of pork quality from the same anatomical location of an individual animal would better enable research conducted to study relationships between animal growth and carcass merit. To facilitate gene expression studies, adipose and muscle tissue samples are often collected immediately following exsanguination to maximize RNA integrity, which is a primary determinant of the sensitivity of RNA-based assays, such as real-time PCR. However, collecting soft tissue samples requires cutting through the hide or skin. This leaves the underlying tissue exposed during scalding, poses possible food safety issues, and potentially confounds pork quality measures. To overcome these limitations, the effect of tissue sample timing post-harvest on RNA integrity, real-time PCR results, and pork quality measurements was investigated by sampling subcutaneous adipose tissue and longissimus thoracis et lumborum muscle immediately following either exsanguination, scalding, or chilling. Sampling time did not affect RNA quality, as determined by the RNA integrity number of RNA samples purified from either adipose (RIN; p > 0.54) or muscle tissue (p > 0.43). Likewise, the sampling time did not influence the results of real-time PCR analysis of gene expression when comparing RNA samples prepared from adipose or muscle tissue immediately following either exsanguination or scalding (p > 0.92). However, sampling tissue prior to scalding resulted in a greater visual color score (p < 0.001) and lesser L* (p < 0.001) and b* (p < 0.001) values without impacting the 24 h pH (p < 0.41). These results suggested that if both RNA-based assays and meat quality endpoints are to be performed at the same anatomical location on an animal, tissue sampling to facilitate RNA-based assays should occur at a time point immediately following scalding. These findings demonstrated that sampling of adipose and muscle tissue can be delayed until after scalding/dehairing without decreasing the RNA integrity or altering the results of real-time PCR assays, while doing so was associated with little impact on measures of pork quality.

49 Impact of Hydrocolloids and Poultry Co-product Combinations on Fresh Pet Food Shelf Life

The development and availability of meat-based food and treats for pets in the retail space continues to increase at a rapid pace. The current study focused on the evaluation of sodium alginate and encapsulated calcium lactate (ALGIN) inclusion within a fresh pet food formulation and subsequent influence on shelf-life characteristics. Poultry co-products are often undervalued throughout the meat industry due to their poor quality and low customer acceptance. However, it is plausible that these co-products could be a potential key component in adding value to the pet food industry. In addition, the use of ALGIN within a ground chicken co-product formulation may create a pet food worth generating a greater retail value for the manufacturer. Fresh chicken frames (CF) and boneless-skinless wooden breast (WB) were purchased from a commercial poultry processing facility and ground. Ground CF and WB (COMB) were allocated randomly to one of ten treatment combinations with either 0.5 or 1.0% added ALGIN. Ground treatments were portioned into 454 g bricks, placed into a form and fill vacuum package, sealed and displayed in a reach-in refrigerated cases for 21 days. Packages of fresh pet food were evaluated for surface color, lipid oxidation, water activity, and pH on days 1, 3, 7, 14 and 21 of the simulated display. Instrumental surface color was lighter, less red, and more yellow (P &lt; 0.05) with increasing percentages of CF regardless of ALGIN inclusion. Whereas pH was greater (P &lt; 0.05) and lipid oxidation were lower (P &lt; 0.05) with increasing percentage of WB. Water activity increased (P &lt; 0.05) when WB and ALGIN inclusion increased. These results suggest that the impact of ALGIN in a poultry co-product pet food formulation are minimal. However, the inclusion percentage of CF or WB could have a greater impact on shelf-life characteristics of fresh pet food.

50 Implications of a Thermoforming Vacuum Packaging or Overwrap Packaging Method on a Simulated Retail Display of Longissimus Lumborum Steaks

Fresh surface color of beef remains a focus for consumers at the time of purchasing in the retail sector. The objective of this study was to evaluate instrumental surface color, expert color evaluation, and lipid oxidation (TBARS) on beef longissimus lumborum steaks packaged using recycle-ready film (RRF) or polyvinyl chloride overwrap (PVC). Paired strip loins (IMPS # 180), fabricated from beef carcasses (n = 7) 10 d postmortem, cut into 2.54 cm-thick steaks, and assigned to one of two packaging treatments RRF (OTR = 0.8 cc/m2/24 h) or PVC (OTR = 14,000 cc/m2/24 h). Steaks were stored under simulated retail conditions (3 °C ± 1.5 °C) in a LED (2297 lux) lighted, three-tiered retail cabinet, rotated daily among shelves for 35 days. From d 0 to 35 objective surface color was captured every 5 days to record changes in lightness (L*), redness (a*), yellowness (b*), Chroma, Hue Angle, and calculated values of spectral wavelengths (Red to Brown, Oxymyoglobin, Deoxymyoglobin, & Metmyoglobin) using a HunterLab colorimeter. Steaks packaged in RRF became lighter (L*) as display period increased (P &lt; 0.05), whereas steaks packaged in PVC became darker (P &lt; 0.05). Redness (a*) values were greatest (P &lt; 0.05) for PVC steaks until day 5, whereas RRF steaks had greater (P &lt; 0.05) surface redness from day 10 to 35 of the display period. Calculated spectral values red to brown were greater (P &lt; 0.05) for steaks in RRF than PVC. Expert color evaluators rated RRF steaks having less browning and less discoloration (P &lt; 0.05) from day 5 to 35 of display. Lipid oxidation was greater (P &lt; 0.05) for PVC steaks from day 10 through day 35 of the display. These results suggest that the use of RRF vacuum packaging for beef steaks is plausible and can maintain surface color characteristics during extended display periods.

51 Influence of Thermoforming Films on Surface Color in Vacuum Packaged Ground Beef

With meat industry efforts focused on improving environmental influencers, adopting alternative packaging films may allow the meat industry to address the sustainability demands of the consumer. The current study evaluated instrumental surface color changes on fresh ground beef using vacuum packaging films identified as recycle ready (RRF), standard barrier (STB) and enhanced barrier (ENB). Coarse ground beef (80:20) was purchased from a commercial processing facility, ground once through a 3.18 mm plate and portioned into 454 g bricks. Ground beef bricks were allocated randomly to one of three packaging treatments (n = 25 packages/treatment), placed into a form and fill pouch, vacuum sealed, and displayed in a three-tiered retail display cabinet (3 °C ± 1.5 °C) for a 21-day simulated retail display period. Ground beef packages were rotated daily for the duration of the 21-d study among all shelves of the display cabinet. On each day of the display period, packages were scanned three times with a hand-held colorimeter (HunterLab) to capture instrumental color readings for lightness (L*), redness (a*), yellowness (b*), Hue angle, Chroma, and spectral wavelength values (400 to 700nm) to calculate relative values of Red:Brown (630:580nm), deoxymyoglobin (DEO), oxymyoglobin (OXY), and metmyoglobin (MET). Calculations of relative myoglobin forms were completed using the log of the reflectance values at 473, 525, 572, and 700nm respectively. Ground beef packaged using ENB barrier film was lighter (L*), redder (a*) and more vivid (Chroma) than all other packaging treatments during the simulated display period (P &lt; 0.05). By day 12 of the simulated retail display, ground beef surface color became lighter (L*), more yellow (b*), less red (a*), less vivid (chroma) and contained greater forms of calculated metmyoglobin, oxymyoglobin (P &lt; 0.05). These results suggest that vacuum packaging of ground beef remains a plausible option for extending surface color during fresh shelf-life conditions.

Shelf-Life Evaluation of Ingredient Combinations and Technologies for Use in Pet Food Formulations

Simple Summary

Creation of new meat-based pet food and pet treats continues to grow at a steady annual rate within the pet food industry. Poultry co-products are often overlooked due to their poor quality and low customer acceptance. However, poultry co-products pose great potential and added value to the pet food industry. Two of the most common poultry co-products (wooden breast and carcass frames) often directed towards pet food were used in a fresh pet food formulation. Due to variations in meat quality because of the wooden breast and carcass frames, a hydrocolloid was utilized to improve fresh pet food characteristics. A hydrocolloid is a type of protein that when added to meat products aids with binding and stabilization of the pet food. For the current study, the combination of sodium alginate and encapsulated calcium lactate pentahydrate (ALGIN) was used. Due to the perceived poor quality of wooden breast and carcass frames, it is plausible that the addition of hydrocolloids can combat the undesirable characteristics. Results from the current study suggest that the impact of ALGIN in poultry co-product pet food combinations does not severely alter shelf-life characteristics of a fresh pet food. However, the inclusion of varying amounts of wooden breast and ground carcass frame can impart a greater impact on shelf-life characteristics in fresh pet food by altering surface color and lipid oxidation.

Abstract

Poultry co-product chicken frames (CF) and wooden breast (WB) along with ingredient technology use may bring enhanced value to the pet food industry. Therefore, the current study focused on evaluating CF and WB combinations along with sodium alginate and encapsulated calcium lactate pentahydrate (ALGIN) inclusion within a fresh pet food formulation under simulated shelf-life conditions. Fresh chicken frames (CF) and boneless-skinless wooden breast (WB) were ground and allocated randomly to one of ten treatment combinations with either 0.5 or 1.0% added ALGIN. Ground treatments were placed into a form and fill vacuum package and stored using a reach-in refrigerated case for 21 days. Packages were evaluated for instrumental surface color, lipid oxidation, water activity, and pH on days 1, 3, 7, 14 and 21 of the display. Packages of pet food were lighter, less red, and more yellow (p < 0.05) with increasing percentages of CF regardless of ALGIN inclusion, whereas pH was greater (p < 0.05) and lipid oxidation was less (p < 0.05) with increasing percentage of WB. Water activity increased (p < 0.05) when WB and ALGIN inclusion increased. The current results suggest that the use of ALGIN in a poultry co-product pet food formulation can improve shelf-life characteristics such as surface color and lipid oxidation in fresh pet food.

Surface Color Variations of Ground Beef Packaged Using Enhanced, Recycle Ready, or Standard Barrier Vacuum Films

With current meat industry efforts focused on improving environmental influencers, adopting sustainable packaging materials may be an easier transition to addressing the sustainability demands of the meat consumer. With the growing popularity of vacuum-packaged meat products, the current study evaluated instrumental surface color on fresh ground beef using vacuum packaging films, recycle-ready film (RRF), standard barrier (STB) and enhanced barrier (ENB). Ground beef packaged using ENB barrier film was lighter (L*), redder (a*) and more vivid (chroma) than all other packaging treatments during the simulated display period (p < 0.05). By day 12 of the simulated retail display, the ground beef surface color became lighter (L*), more yellow (b*), less red (a*), less vivid (chroma) and contained greater forms of calculated metmyoglobin, oxymyoglobin (p < 0.05). The current results suggest that barrier properties of vacuum packaging film for ground beef are pivotal for extending the surface color during fresh shelf-life conditions.

Characteristics of Pork Muscles Cooked to Varying End-Point Temperatures

M. biceps femoris (BF), m. semimembranosus (SM) and m. semitendinosus (ST) from fresh pork ham were evaluated for characteristics of quality after cooking to an internal endpoint temperature of 62 °C or 73 °C. Fresh ham muscles from the left side (N = 68) were cut into 2.54 cm thick chops and allocated to cooking loss, Warner–Bratzler shear force (WBSF), pH and instrumental cooked color analysis. Cooking losses were greater (p < 0.0001) for SM and chops cooked to an internal temperature of 73 °C (p < 0.0001), whereas WBSF did not differ (p = 0.2509) among the three muscles, but was greater (p < 0.0001) in chops cooked to 73 °C. Fresh muscle’s pH was greater (p < 0.05) in ST than BF or SM. Lastly, the interactive effect (p < 0.05) of muscle × endpoint temperature for ST chops cooked to 73 °C was lighter (L*), but, when cooked to 62 °C, they were more red (a*), more yellow (b*) and incurred less color change from red to brown than BF or SM. The current results suggest it is plausible for BF, SM and ST to be considered for alternative uses instead of traditional value-added manufacturing.

Carcass Traits of Growing Meat Goats Fed Different Levels of Hempseed Meal

Industrial hemp is currently being investigated as a potential new crop in the U.S. with the 2014 and 2018 Farm Bills passage. Hemp seeds are utilized to produce hemp oil and result in Hempseed Meal (HSM) production, rich in crude protein and fiber, making it an ideal candidate as a feedstuff for ruminant animals. This study evaluated the effects of feeding different levels of HSM on the carcass traits and meat quality of crossbred Boer goats. Forty castrated male goat kids with an initial average body weight of 25.63±.33 kg and approximately six months of age and kg were assigned to one of four treatments (n = 10) in a completely randomized design. Goats were fed pelleted diets (50% forage and 50% concentrate). Treatments consisted of different levels of HSM: control with 0%, 10%, 20%, and 30% HSM supplementation of the total diets. The goats were harvested, and carcasses were processed at the Lambert-Powell Meat Laboratory at Auburn University after a 60-d feeding trial. Data were analyzed using the GLIMMIX procedures of SAS 9.4 (SAS Inst. Inc., Cary, NC). There were no significant differences (P &gt; 0.05) on the mean values of dressing percentages (46.59, 45.42, 45.77, and 46.16% for 0, 10, 20 and 30% HSM, respectively) and ribeye area (3.68, 3.4, 3.47, 3.39 inches, respectively). The percentage of moisture, fats, proteins, and collagen in the muscles showed no significant difference (P &gt; 0.05) between the different levels of HSM-containing diets. The marbling scores (376, 399, 355, 364 respectively) were also not significantly different (P &gt; 0.05) among the treatments and are representative of marbling scores indicative of “slight.” Results suggest that producers can include up to 30% of HSM in the diets of growing meat goats without creating a detrimental effect on carcass traits.

PSV-31 Influence of Hempseed Meal Supplementation on Fresh and Cooked Characteristics of Boer Cross Goats

Hempseed meal is byproduct of hemp oil production and is relatively high in fiber, fat, and protein, making it a potential feedstuff for ruminants. However, the impact this new byproduct could have on meat characteristics is unknown. The objective of the current study was to evaluate the impact of HSM on fresh and cooked characteristics of Spanish meat goat retail cuts. Forty Boer crossbred castrated male goats were randomly allocated to one of four diets (n = 10; 0, 10, 20 or 30%) containing HSM which originated from the manufacturing industry of hemp oil. Goats were provided 2 kg of diet daily that contained varying levels of HSM in addition to ad-libitum access to water throughout the study. Following a 60-day feeding period goats were harvested at the Lambert-Powell Meats Laboratory located at Auburn University. After chilling for 12 h at 0°C, carcass measurements were collected prior to carcass fabrication. Goat carcasses were fabricated into wholesale cuts of the shoulder, rack, loin and leg. Paired loins and legs were sliced into 2.54-cm-thick chops, vacuum packaged, and assigned to cook yield, instrumental fresh color, and instrumental tenderness and frozen at -23°C until all laboratory analysis could be completed. The use of HSM did not alter cooking yield in either the goat loin or leg chop (P &gt; 0.05) regardless of inclusion percentage within the diet. Furthermore, Warner-Bratzler shear force (WBSF) did not differ (P &gt; 0.05) with increasing inclusion rates of HSM for either the loin or leg chops. Instrumental color for lightness (L*) or yellowness (b*) did not differ (P &gt; 0.05) across diet treatments for either the loin or leg chops. These findings suggest that the inclusion of HSM within the diet of Boer cross goats did not alter fresh or cooked meat characteristics in either the loin or leg chops.

159 Effect of ionophore, implant, and beta-adrenergic agonists on key indicators of sustainable beef production

Net protein contribution (NPC) of the beef value chain has been evaluated and it has been demonstrated that the beef value chain positively contributes to NPC; however, the specific role of growth-enhancing technologies has not be evaluated. To compare effects of technology on NPC baseline, performance data from 8 commercial feedlots located in the Texas panhandle (n = 6) and Kansas (n = 2) were used to create 8 scenarios: 1) no technology (NT), 2) ionophore (ION), 3) implant (IMP), 4) beta-agonist (B), 5) ionophore and implant (ION+IMP), 6) ionophore and beta-agonist (ION+B), 7) implant and beta-agonist (IMP+B), and 8) ionophore, implant and beta-agonist (I+I+B). An IMP×B interaction was observed for human-edible protein conversion efficiency (HePCE) and NPC (P ≤ 0.03). Implants and beta-agonists increased HePCE and NPC compared to NT (P &lt; 0.01), and IMP+B was greater than combined effects of IMP and B. Ionophore scenarios had greater HePCE and NPC compared to NT (P &lt; 0.01). Interactions for ION×IMP and IMP×B were observed for NPC of beef value chain (P &lt; 0.03), but an ION×B interaction was not observed (P = 0.07). All technology scenarios were lower than NT for NPC (3.21 vs 3.74, respectively; P &lt; 0.01) because HePCE for the beef value chain was reduced when cattle were fed longer in the technology scenarios. Interactions for ION×IMP, IMP×B, and ION×B were observed for enteric CH4 production feedlot cattle (P ≤ 0.03), and a three-way interaction was observed for enteric CH4 production of the beef value chain (P &lt; 0.01). All technologies reduced enteric CH4 produced per kg of HePg compared to NT (P &lt; 0.01). Net protein contribution should be balanced with other indicators of sustainability for a representative understanding of technology impacts on sustainable beef production.

PSV-28 Feeding Ractopamine Improves Growth Performance and Carcass Characteristics of the Lard-type Mangalica Pig

Mangalica pigs are a popular niche breed given their reputation for superior quality pork; however, the slow growth rate, poor lean yield and excessive adiposity exhibited by this breed limits its widespread adoption. Our objective was to determine if feeding Ractopamine (RAC), a metabolic modifier that improves feed efficiency and lean yield, would improve growth performance without impairing pork quality in the Mangalica. To accomplish this, a growth trial was conducted whereby pigs (n = 28) weighing 73 kg were fed a standard grower ration supplemented with either 0 or 22 ppm RAC for 21 days during which daily feed intakes and weekly body weights were recorded for all animals. Then pigs were finished to a 105 kg harvest weight. At 24h postmortem, carcasses were ribbed at the 10th rib to facilitate pork quality and carcass composition measurements. Primal cuts were fabricated and individually weighed. As hypothesized, RAC increased ADG (P &lt; 0.04) and feed efficiency (P &lt; 0.03) 24% and 21% respectively. However, unexpectedly, RAC failed to suppress voluntary feed intake (P &gt; 0.71). Interestingly RAC increased LEA (P &lt; 0.0001) by 21% but did not impact 10th rib fat depth (P &gt; 0.90) or marbling score (P &gt; 0.77). Likewise, RAC failed to alter any primal cut weights. Feeding RAC lowered b* values (P &lt; 0.04) and tended to lower L* values (P &lt; 0.08) while not affecting a* values (P &gt; 0.30) suggesting RAC darkened loin color. Finally, RAC improved cook loss percentage (P &lt; 0.02) 11% while not impacting WBSF (P &gt; 0.31). Collectively, these data support the hypothesis that feeding RAC to the lard type Mangalica pig improves growth performance without impairing pork quality in this breed. Feeding RAC may be a viable strategy to improve the economic feasibility of utilizing this breed to target niche markets.

Substituting ground woody plants for cottonseed hulls in lamb feedlot diets: carcass characteristics, adipose tissue fatty acid composition, and sensory panel traits

Effects of using ground woody plants in Rambouillet wether lamb (n = 48) feedlot diets on carcass characteristics, adipose tissue fatty acid composition, and sensory panel traits were evaluated. In a randomized design study with two feeding periods (period 1 = fed a 70% concentrate diet from days 0 to 27; period 2 = fed an 86% concentrate diet from days 28 to 57), lambs were individually fed six diets that differed only by roughage source (n = 8 animals/treatment; initial BW = 32.9 ± 3.2 kg): cottonseed hulls (CSH; control) or ground wood consisting of either redberry (RED), blueberry (BLUE), one-seed (ONE), or eastern red cedar (ERC) Juniperus spp., or Prosopis glandulosa (MESQ). After 57 d, the lambs were humanely harvested and after chilling (2 ± 1 oC) 24 h, carcasses were evaluated for carcass traits. At 48 h postmortem, the longissimus thoracis (LT) was removed from the left side of the carcass, and after freezing for no more than 3 mo, were thawed for 24 h, cooked, and evaluated by a trained sensory panel. Additionally, volatile aroma chemicals on the LT were determined by gas chromatograph/mass spectrometer/olfactory (GC/MS/OF, respectively) analyses. Lamb HCW was greater (P = 0.01) for lambs fed CSH compared with all other diets, but lambs had similar (P > 0.08) LM area, back fat thickness, leg circumference, and body wall. Neither adipose tissue fatty acid composition (P > 0.08) nor trained sensory panel evaluation (P > 0.18) was affected by finishing diet roughage source. Of the 81 volatile aroma compounds found in the grilled lamb chops, only seven were affected (P < 0.05) by dietary roughage source and included 1-pentanol (a sweet, pleasant aroma), heptenal (a fishy aroma), pentanal (fermented, bready aroma description), 1-(1H-pyrol-2yl)-ethanone (caramel-like), 2-heptanone (cheesy, banana, fruity aromatic), 6,7-dodecanedione (unknown aroma), and butanoic acid (a sweaty, rancid aroma). The addition of any of four species of juniper or mesquite may be substituted for CSH without negatively affecting carcass fat and muscling, fatty acid, or sensory traits.

Bloom Development of the Beef Semimembranosus and Triceps Brachii as Influenced by Wet-Aging

The semimembranosus (SM) and triceps brachii (TB) from USDA Select beef carcasses were used to test the effect of wet-aging period on bloom development. Inside rounds (IMPS#168) and shoulder clods (IMPS #114) were randomly allocated to 0, 7, 14, 21, 28, and 35 d wet-aging at 2°C (n = 10 subprimal cuts/aging period). Each week, two 2.54-cm-thick, non-adjacent steaks were cut from aged inside rounds and shoulder clods, and instrumental color (L*, a*, and b*) of the SM and TB was measured at 10-min intervals for 2 h after cutting. Steaks from the SM and TB became a more vivid (greater C* values; P < 0.05), redder (greater a* values; P < 0.05), and yellower (greater b* values; P < 0.05) color during the 120-min bloom period. Moreover, the calculated proportion of oxymyoglobin (OMb) in SM and TB steaks increased (linear, P < 0.001) during the first 80 min after cutting but stabilized thereafter. Redness (a* and hue angles), b*, and C* values decreased (linear, P ≤ 0.050) in SM steaks as duration of wet-aging increased from 0 to 35 d, but length of wet-aging had no (P ≥ 0.127) effect on instrumental color measures of TB steaks. Neither the percentage of calculated OMb (P = 0.580) nor OMb asymptotic point (P ≥ 0.214) for SM steaks was affected by duration of wet-aging, and, even though the proportion of OMb in TB steaks was not altered (P = 0.459) by postmortem aging, OMb asymptotic points increased (linear, P = 0.001) in TB steaks with increasing durations of wet-aging. Results of these experiments indicate that 90%, or more, of the change in color was achieved within the first 50 to 60 min after cutting, but duration of wet-aging had little to no impact on bloom development in SM and TB steaks.

Aging implications on fresh muscle traits of Certified Angus Beef steaks

Vacuum-packaged Certified Angus Beef (CAB) subprimals ( = 72) that included the longissimus thoracis (LT), longissimus lumborum (LL), gluteus medius (GM), and infraspinatus (IF) muscles were purchased from a major beef packing facility. Subprimals were allocated to 1 of 3 aging periods (14, 28, or 42 d) and aged at 2°C. After aging, 5 steaks were cut from each subprimal and assigned to pH, water-holding capacity, Warner-Bratzler shear force (WBSF), cooked color, cooking yield, cooking loss, and sensory panel analysis. Infraspinatus steaks were more tender ( < 0.05) than all other steaks, and subprimals aged 14 d had greater ( < 0.05) WBSF values than the other 2 aging periods, regardless of muscle. Water-holding capacity and cook yield were greater ( < 0.05) for LL and LT than IF and GM steaks, whereas purge loss was greater ( < 0.05) for IF and GM than LL and LT steaks. Throughout the aging periods, pH declined for all muscle groups, with IF steaks having the greatest ( < 0.05) pH values among all muscles. Among IF steaks, sensory evaluations of all attributes did not ( ≥ 0.26) differ across aging periods; yet among LT steaks, consumers rated those aged 14 d greater ( < 0.05) in overall impression than LT steaks aged 28 and 42 d. Among LT steaks, those aged 14 d received greater ( < 0.05) flavor ratings than LT steaks subjected to longer aging periods, and LT steaks aged 14 d received the greatest ( < 0.05) overall impression, with consumers giving greater ( < 0.05) overall impression scores to LT steaks aged 42 d over those aged 28 d. Aging period had no effect ( ≥ 0.017) on consumer ratings for flavor, tenderness, juiciness, or overall impression of LL steaks. Among GM steaks, consumers rated steaks aged 14 and 28 d more ( < 0.05) flavorful than those aged 42 d, and consumer ratings for overall impression were greater ( < 0.05) for GM steaks aged 28 d than for GM steaks aged 42 d; however, consumers failed ( = 0.035) to note differences in tenderness scores of GM steaks in response to aging period. Furthermore, consumers indicated a greater ( < 0.05) likelihood to purchase LT steaks aged 14 d over LT steaks aged 28 d, LL steaks aged 42 d over LL steaks aged 14 d, and GM steaks aged 14 and 28 d over GM steaks aged 42 d. These results indicate that consumers struggled to identify steak flavor attributes and suggest that the benefit of aging for premium beef products does not offer a tremendous sensory advantage to the consumer.

Fresh and cooked color of dark-cutting beef can be altered by post-rigor enhancement with lactic acid

Fresh and cooked color of dark-cutting (DC) beef strip loins (mean pH=6.56) enhanced with 0.25, 0.50, 0.75 or 1.00% lactic acid (LA) were compared to non-enhanced DC and normal pH (NpH; mean pH=5.43) strip loins. Even though NpH steaks received the most (P<0.05) desirable fresh color scores, color scores for steaks from DC sections enhanced with 0.25% LA approached those of NpH steaks after the first day of retail display. Discoloration scores were also similar (P>0.05) among NpH and 0.25% LA-enhanced DC steaks throughout the 5 d of display. Fresh steaks from NpH strip loins were redder, as evidenced by greater (P<0.05) a(∗) values and lower (P<0.05) hue angles, than DC steaks and DC steaks enhanced with LA, regardless of concentration. However, cooked color scores and proportions of denatured myoglobin were similar (P>0.05) between untreated NpH steaks and DC steaks enhanced with 0.25% LA. Results from this study indicate that enhancing DC beef with LA may lead to the brightening of the fresh color and prevention of the persistent red cooked color, approaching that of NpH beef.

Interactive effect of ractopamine and dietary fat source on quality characteristics of fresh pork bellies1

Crossbred pigs (n = 216) were used to test the interaction, if any, of ractopamine (RAC) and dietary fat source on the characteristics of fresh pork bellies. Pigs were blocked by BW (77.6 +/- 6.5 kg) and allotted randomly to pens (6 pigs/pen). After receiving a common diet devoid of RAC for 2 wk, pens within blocks were assigned randomly to 1 of 4 treatments arranged in a 2 x 2 factorial design, with 5% fat (beef tallow vs. soybean oil) and RAC (0 vs. 10 mg/kg). At the conclusion of the 35-d feeding period, pigs were slaughtered at a commercial pork packing plant (average BW of 108.8 +/- 0.6 kg), and fresh bellies were captured during carcass fabrication. Neither RAC (P = 0.362) nor fat source (P = 0.247) affected belly thickness. Subjective (bar-suspension) or objective (compression test) measures of belly firmness were not (P > or = 0.148) affected by the inclusion of RAC in the diet; however, bellies from pigs fed soybean oil (SBO) were softer than those from pigs fed beef tallow (BT), as indicated by perpendicular (P < or = 0.005) and parallel (P < 0.001) suspensions. Moreover, bellies from BT-fed pigs required more (P = 0.096) force to compress 50% of their thickness than bellies from SBO-fed pigs (52.29 vs. 43.51 kg). Color (L*, a*, and b* values) of the belly lean and fat was not (P > or = 0.131) affected by RAC, and lean color was similar (P > or = 0.262) between fat sources; however, belly fat from BT-fed pigs was lighter (P = 0.030) and redder (P = 0.013) in color than belly fat from SBO-fed pigs. Bellies of SBO-fed pigs had greater (P < 0.001) proportions of PUFA and lower (P < 0.001) proportions of SFA and MUFA than belly fat from pigs fed BT. Regardless of the RAC inclusion level, PUFA:SFA and iodine values were lower in belly fat from pigs fed BT than SBO; however, within SBO-fed pigs, PUFA:SFA and iodine values were further increased by feeding RAC (RAC x fat source, P < 0.001). As expected, dietary fat source altered the fatty acid composition of fresh pork bellies, which subsequently impacted fresh belly firmness. Interestingly, including RAC in swine finishing diets exacerbated the effect of feeding SBO on pork fat polyunsaturation.

Effect of supplemental iron on finishing swine performance, carcass characteristics, and pork quality during retail display1

Crossbred pigs (n = 185) were used to test the effects of dietary Fe supplementation on performance and carcass characteristics of growing-finishing swine. Pigs were blocked by BW, allotted to pens (5 to 6 pigs/pen), and pens (5 pens/block) were allotted randomly to either negative control (NC) corn-soybean meal grower and finisher diets devoid of Fe in the mineral premix, positive control (PC) corn-soybean meal grower and finisher diets with Fe included in the mineral premix, or the PC diets supplemented with 50, 100, or 150 ppm Fe from Availa-Fe (an Fe-AA complex). When the lightest block averaged 118.2 kg, the pigs were slaughtered, and bone-in pork loins were collected during fabrication for pork quality data. During the grower-I phase, there was a tendency for supplemental Fe to reduce ADG linearly (P = 0.10), whereas in the grower-II phase, supplemental Fe tended to increase ADG linearly (P = 0.10). Even though pigs fed NC had greater G:F during the finisher-I phase (P < 0.05) and across the entire trial (P = 0.07), live performance did not (P > or = 0.13) differ among dietary treatments. There were linear increases in 10th-rib fat depth (P = 0.08) and calculated fat-free lean yield (P = 0.06); otherwise, dietary Fe did not (P > 0.19) affect pork carcass muscling or fatness. Moreover, LM concentrations of total, heme, and nonheme Fe were similar (P > 0.23) among treatments. A randomly selected subset of loins from each treatment was further fabricated into 2.5-cm-thick LM chops, placed on styrofoam trays, overwrapped with polyvinyl chloride film, and placed in coffin-chest display cases (2.6 degrees C) under continuous fluorescent lighting (1,600 lx) for 7 d. During display, chops from NC-fed pigs and pigs fed the diets supplemented with 100 ppm Fe tended to have a more vivid (higher chroma value; P = 0.07), redder (higher a* value; P = 0.09) color than LM chops of pigs fed 50 ppm of supplemental Fe. Moreover, greater (P < 0.01) redness:yellowness ratios in chops from pigs supplemented with 100 ppm Fe indicated a more red color than chops from PC-fed pigs or pigs fed diets supplemented with 50 ppm Fe. In conclusion, however, increasing dietary Fe had no appreciable effects on performance, carcass, or LM characteristics, suggesting that current dietary Fe recommendations are sufficient for optimal growth performance, pork carcass composition, and pork quality.

Effects of supplemental manganese on performance of growing-finishing pigs and pork quality during retail display

Crossbred barrows and gilts (n = 168) were used to test the effects of supplemental Mn during the growing-finishing period on performance, pork carcass characteristics, and pork quality during 7 d of retail display. Pigs were blocked by BW and allotted within blocks to pens (5 pigs/pen in blocks 1, 2, 5, and 6, and 4 pigs/pen in blocks 3 and 4). A total of 36 pens was randomly assigned to 1 of 6 dietary treatments, where the basal diets were formulated with (PC) or without (NC) Mn in the mineral premix, and supplemented with 0 or 350 ppm (as-fed basis) of Mn from MnSO4 or a Mn-AA complex (AvMn). Pigs were slaughtered at a commercial pork packing plant when the lightest block of pigs averaged 113.6 kg. During fabrication, boneless pork loins were collected and transported to Oklahoma State University, where 2.5-cm-thick LM chops were packaged in a modified atmosphere (80% O2 and 20% CO2) and subsequently placed in display cases (2 to 4 degrees C) under continuous fluorescent lighting (1,600 lx) for 7 d. Pig performance was not (P > or = 0.44) affected by supplemental Mn; however, during the grower-II phase, pigs fed the basal diets including Mn consumed less (P < 0.02) feed and tended to be more efficient (P < 0.09) than pigs fed the basal diets devoid of Mn. Throughout the entire feeding trial, neither dietary nor supplemental Mn altered (P > or = 0.22) ADG, ADFI, or G:F. Chops from pigs fed the diets supplemented with MnSO4 received greater (P < or = 0.05) lean color scores and had a redder (greater a* and hue angle values), more vivid color than chops from pigs fed the diets supplemented with AvMn. Additionally, LM chops from pigs fed the PC diets supplemented with MnSO4 were darker (lower L* values; P < 0.05) than chops from pigs fed the NC diets or PC diets supplemented with 0 or 350 ppm of AvMn. Even though discoloration scores were similar during the first 4 d of display, chops from pigs fed the PC diets supplemented with MnSO4 were less (P < 0.05) discolored on d 6 and 7 of retail display than chops from pigs fed the PC or NC diets and diets supplemented with AvMn (dietary treatment x display time, P = 0.04). Results of this study indicate that feeding an additional 350 ppm of Mn from MnSO4 above the maintenance requirements of growing-finishing pigs does not beneficially affect live pig performance but may improve pork color and delay discoloration of pork during retail display.

Lateral and longitudinal characterization of color stability, instrumental tenderness, and sensory characteristics in the beef semimembranosus

The objectives of this study were to evaluate longitudinal and lateral variations in color stability and sensory characteristics of the semimembranosus from each muscle location (dorsal=D, medial=M, ventral=V), and within each steak subsequently divided into four regions (caudal-distal=CaD, cranial-distal=CrD, caudal-proximal=CaP, cranial-proximal=CrP). Instrumental color assessment indicated that L(∗) (lightness) values tended to be lower for the CaD and CrD regions of all muscle locations, with higher L(∗) values recorded for the CrP regions of muscle sections. Instrumental tenderness measurements for Meullenet-Owens razor and Warner-Bratzler shear force values were generally lower for the CaD region of the D section, whereas regions within the V section were tougher and required greater shear force. Sensory panelists perceived lower amounts of connective tissue in the CaD of the D section, which tended to be more tender, whereas higher levels of connective tissue and greater toughness occurred in the CaP and CrP regions of the M and V sections. These results provide a detailed muscle profile of the quality variation within the semimembranosus, and may be used to further enhance the fabrication and marketability of this beef subprimal cut.

Dithiothreitol treatment induces heterotypic aggregation of newly synthesized secretory proteins in HepG2 cells

To analyze the importance of the endoplasmic reticulum oxidizing state for the folding and aggregation of newly made polypeptides, we have incubated intact HepG2 hepatoma cells in the presence of dithiothreitol. When dithiothreitol-treated cells were extracted under nondenaturing conditions immunoprecipitates of newly synthesized albumin showed a complex polypeptide profile. Using direct and sequential immunoprecipitation protocols we identified eight other polypeptide chains, transferrin, plasminogen, ceruloplasmin, alpha 2-macroglobulin, the three fibrinogen chains, and haptoglobin, that were among the proteins co-immunoprecipitated with albumin. The heterotypic aggregates are larger than several hundred kilodaltons and are stabilized by noncovalent interactions. Of the 10 polypeptide chains we examined, only one, alpha 1-antitrypsin, failed to aggregate. This protein is distinguished from the others by the absence of disulfide bonds. We propose a model in which the function of the oxidizing conditions of the endoplasmic reticulum is to promote the rapid formation of disulfide bonds that stabilize adhesive domains in a buried state, thus preventing "global" heterotypic aggregation of newly synthesized chains.

Early disulfide bond formation prevents heterotypic aggregation of membrane proteins in a cell-free translation system

We previously demonstrated that a heterotypic complex of the two rat asialoglycoprotein receptor subunits was assembled during cell-free translation (Sawyer, J. T., and D. Doyle. 1990. Proc. Natl. Acad. Sci. USA. 87:4854-4858). We have characterized this system further by analyzing polypeptide interactions under both reducing and oxidizing translation conditions. This report shows that the complex represents a heterogeneous interaction between reduced membrane proteins rather than a specific oligomeric structure. In the reduced state membrane proteins interact in this system to form aggregates of diverse size and composition. The aggregated nascent polypeptides interact with the immunoglobulin heavy chain binding protein but this protein is not an integral component of the aggregate. Aggregation occurs via the exoplasmic domain, rather than the transmembrane domain, and the folding of this domain by the formation of intramolecular disulfides, prevents the interaction from occurring. Additionally, the folded molecules containing intramolecular disulfides lack high affinity binding activity and thus appear to resemble the earliest folding intermediates seen in vivo (Olson, J. T., and M. D. Lane. 198. FASEB (Fed. Am. Soc. Exp. Biol.) J. 3:1618-1624). These results lead us to suggest that the formation of intramolecular disulfides during early biogenesis serves to prevent nonspecific associations between nascent polypeptides.

Assembly of a heterooligomeric asialoglycoprotein receptor complex during cell-free translation

We have translated RNAs for the two rat asialoglycoprotein receptor polypeptides together in a cell-free system containing dog pancreatic microsomes and immunoprecipitated the products with antibodies that distinguish the two proteins. In this system the proteins oligomerize, as judged by their coprecipitation with either of the subunit-specific antisera. Oligomerization does not occur between subunits synthesized without microsomes or between subunits synthesized on separate microsomes mixed during detergent solubilization. Thus, oligomerization occurs within the microsomal membrane. We calculate that oligomerization proceeds with an efficiency of approximately 85%. The receptor complex appears to represent a specific oligomer because it excludes a third membrane glycoprotein synthesized in the same reaction. Oligomerization of the asialoglycoprotein receptor in vitro should provide a useful system to study the assembly of a membrane-protein complex.

Identification of a complex of the three forms of the rat liver asialoglycoprotein receptor

We have generated antibodies against synthetic peptides which represent the carboxyl terminus of either the major, or the two minor, forms of the rat hepatic lectin which recognizes galactose-terminated glycoproteins (asialoglycoproteins). The antibodies were shown to be specific for the form of the lectin containing the immunizing peptide sequence by the following: reaction with purified lectin after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoprecipitation of sodium dodecyl sulfate-denatured lectin, immunoprecipitation of lectin synthesized in vitro. These antibodies, however, precipitated all three rat hepatic lectin forms from nonionic detergent extracts of hepatocytes labeled with 125I via the lactoperoxidase catalyzed technique. A similar result was obtained if antibody was bound to intact cells prior to solubilization with detergent and collection of the immune complexes. We conclude that at least the plasma membrane-associated fraction of the rat hepatic lectin forms exists as a heterotypic complex.

Differential redistribution of lectin receptor classes on clonal rat myotubes and myoblasts

To evaluate the relative mobilities of cell surface glycoconjugates during myogenesis we have studied the redistribution of fluorescein-conjugated plant lectins on L6 rat myogenic cells. Previous experiments had demonstrated that the receptors for the lectins soybean agglutinin (SBA), wheat germ agglutinin, concanavalin A and Lens culinaris agglutinin all were relatively uniformly distributed on both myoblasts and myotubes, and that SBA receptors were capable of rapid redistribution on myotubes but not myoblasts at 4 degrees C (Sawyer & Akeson, 1983). Here we show that when SBA-labelled myoblasts are incubated at 37 degrees C, or for extended times at 4 degrees C, the lectin aggregates as on myotubes. So it appears that SBA-binding components show a quantitative rather than qualitative change in their mobility during L6 differentiation. In addition, the redistribution of the three other lectins on myoblasts and myotubes was either less prominent (i.e. showing fewer apparent surface clusters) or occurred less rapidly than with SBA. None of these three lectins showed striking differences in mobility between myoblasts and myotubes. Thus, it appears that SBA binds to a subset of surface glycoconjugates that is relatively highly mobile, and that this mobility is specifically enhanced with differentiation.

Clonal myoblasts and myotubes show differences in lectin-binding patterns

To determine changes in distribution or mobility of cell-surface glycoconjugates during myogenesis the binding of fluorescein-conjugated plant lectins to myoblasts and myotubes of the L6 rat skeletal muscle cell line has been studied. Binding has been carried out at 4 degrees C on either live or glutaraldehyde-fixed cells. Fluorescein conjugates of soybean agglutinin (Fl-SBA), wheat germ agglutinin (Fl-WGA), concanavalin A (Fl-conA) and Lens culinaris agglutinin (Fl-LCA) produced predominantly uniform fluorescence on both live and fixed myoblasts. On fixed myotubes, Fl-LCA, Fl-conA and Fl-SBA again produced predominantly uniform fluorescence, whereas Fl-WGA showed a pattern of diffuse, irregular spots in addition to uniform fluorescence. Fl-conA, Fl-LCA and Fl-WGA binding to live myotubes resulted in patterns quite similar to those on fixed myotubes; the only differences being the presence of weak patterns of diffuse spots with Fl-LCA and Fl-conA and an enhanced pattern of diffuse spots with Fl-WGA. Fl-SBA, however, showed a unique pattern on live myotubes which consisted of discrete, round spots and minimal uniform fluorescence. With shorter labeling times, Fl-SBA produced relatively more prominent uniform fluorescence on live myotubes. It appears, therefore, that the native distribution of SBA, conA and LCA-binding sites is similar and predominantly random on L6 myoblasts and myotubes, whereas some WGA-binding sites may be aggregated on myotubes. The results also suggest that SBA-binding sites readily cluster at 4 degrees C on myotubes but not myoblasts, whereas the other lectin sites undergo little or no redistribution on either cell type. Thus the mobility of SBA-binding sites may increase with differentiation.