Effects of Conjugated Linoleic Acid, Salt, and Sodium Tripolyphosphate on Physical, Sensory, and Instrumental Color Characteristics of Beef Striploins

Authors


Abstract

ABSTRACT:  USDA Select striploins (IMPS 180; n= 24) were cut into thirds (anterior, medial, and posterior) and assigned to 1 of 8 treatments utilizing a randomized incomplete block design. Treatments included (1) control (C); (2) 1.5% conjugated linoleic acid (conjugated linoleic acid = CLA) (CGA); (3) 0.4% sodium tripolyphosphate (PHO); (4) 0.5% salt (SAL); (5) 0.4% sodium tripolyphosphate, 0.5% salt (SPH); (6) 0.4% sodium tripolyphosphate, 1.5% CLA (PCL); (7) 0.5% salt, 1.5% CLA (SCL); and (8) 0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA (SPC). Treatments were injected with solutions to 110% (10% pump) of their original weight. Treatments with CLA had higher (P < 0.05) marbling scores than treatments that did not. Not including SAL, treatments with salt, or phosphate or a combination of the two had higher tenderness values when sampled by panelists. Fresh steaks with inclusion of CLA had greater amounts (P < 0.05) of the CLA isomers than steaks not having CLA. Cooked steaks having CLA also had greater amounts (P < 0.05) of CLA, except for SCL, which were not different (P > 0.05) from the non-CLA treatments. Day was a significant source of variability for a*, b*, and saturation index. Treatment × day interactions were significant (P < 0.05) for hue angle and L* values. These data suggest that inclusion of CLA can increase amounts of CLA isomers without major deleterious effects to instrumental, physical, and quality characteristics of beef striploin steaks.

Introduction

The beef industry has had problems not only by high variability but also by the lack of highly marbled steaks. This has a major impact due to the fact that quality of beef is associated to the overall marbling and quality grade of beef. Studies by several researchers including Robbins and others (2003) and Baublits and others (2005, 2006a,b) have shown that palatability and overall quality of beef steaks can be enhanced with phosphates and/or salt, or a combination of the two to produce not only a better product but a more uniform product as well. Another issue faced by the beef industry has been the negative health implications of saturated fatty acids found in beef. This could be possibly eased or fixed if the incorporation of a healthful fatty acid such as CLA could be used to enhance the fatty acid profile of beef. Conjugated linoleic acids have been shown to have positive healthful benefits such as antiadipogenic, anticarcenogenic, and antiinflammatoy properties to name a few (Bhattacharya and others 2006). Beef contains some CLA found in meat due to ruminant biohydrogenation, which is the natural mechanism for CLA production and deposition in beef. Lorenzen and others (2007) found that changing the feeding regimes could increase the amount of CLA in beef. However, 1 serving a day of beef from their highest CLA containing group would still not be enough to achieve the necessary intake that has been considered to be beneficial to health in animal studies. Baublits and others (2007), however, were able to dramatically increase the amount of CLA making it easier to consume the recommended intake.

The idea of not only increasing the uniformity and palatability of beef but also the marbling score and health benefits of beef became possible when Baublits and others (2007) found that inclusion of conjugated linoleic acid can increase marbling scores of steaks. This not only allowed for increased palatability but increased marbling as well. This could have positive impacts for the beef industry due to the way that steaks are marketed. This could also allow for USDA Select or Standard steaks to be marketed with the same level of marbling as USDA Choice or Prime cuts. Therefore the objectives of this study were to examine the effects of inclusion of CLA with or without salt, with or without phosphate, or the combination of the two on the physical, sensory, and instrumental color characteristics of beef striploins.

Materials and Methods

Muscles

Fresh USDA Select beef striploins (IMPS 180; n= 24) were obtained from a commercial packing plant from the same day of production and transported to the Univ. of Arkansas Red Meat Abattoir and aged for 12 d. Upon completion of aging, muscles were removed from vacuum packages and external fat and adjacent muscles were removed from the longissimus muscles. Muscles were then split into thirds and assigned to 1 of 8 treatments. Muscles were 14 d postmortem on day 0 of the study.

Treatments and solutions

One of 8 treatments was assigned to each muscle section. Treatments were equally distributed across muscle positions (anterior, medial, and posterior). Ingredients used were sodium tripolyphosphate, salt (NaCl), and water-soluble milk powder base CLA (Tonalin® 60 WDP, Cognis Corp., Cinncinati, Ohio, U.S.A.). The powdered CLA predominately contained approximately equal amounts of the cis-9; trans-11 and trans-10; cis-12 isomers with a maximum level of 0.07% mixed tocopherols and ascorbylpalmitate antioxidants. Treatments included (1) control (CON); (2) 1.5% CLA (CGA); (3) 0.4% sodium tripolyphosphate (PHO); (4) 0.5% salt (SAL); (5) 0.4% sodium tripolyphosphate, 0.5% salt (SPH); (6) 0.4% sodium tripolyphosphate, 1.5% CLA (PCL); (7) 0.5% salt, 1.5% CLA (SCL); and (8) 0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA (SPC). All treatment solutions were prepared in 2.2 °C tap water and agitated with ingredients until time of injection. Solution pHs were taken prior to injection and are as follows: CLA, 7.37; PHO, 8.83; SAL, 6.7; PCL, 8.64; SCL, 6.41; SPH, 7.87; and SPC, 7.5. All treatments were injected at 110% (10% pump) of fresh product weight. Treatments were injected via a Fomaco 20/40 injector (Reiser, Inc., Canton, Mass., U.S.A.) having 80 needles with 4 needles/5 cm2. Following injection, all treatment muscle groups were reweighed and vacuumed packaged and stored at 1 °C for 48 h.

Sample processing

After approximately 48 h post-enhancement, muscles were removed from vacuum packages. Muscle sections were then taken and cut into 2.54 cm steaks for their respective analysis. Two steaks from each muscle section were randomly chosen and placed on foam trays with absorbent pads and overwrapped with polyvinyl chloride film with an oxygen transfer rate of 14020 cc O2/m2/24 h/atm-60 gauge (Prime Source®, Koch Supplies Inc., Kansas City, Mo., U.S.A.). Steaks that were overwrapped and designated for instrumental color and thiobarbituric acid reactive substances (TBARS) were placed in display cases under simulated retail conditions (4 °C; deluxe warm white fluorescent lighting, 1600 1×, Philips Inc., Somerset, N.J., U.S.A.) for 7 d. All other steaks from the muscle sections were vacuum packaged and frozen until subsequent analysis of Warner–Bratzler shear force, cooking loss, and fatty acid determination. Sensory taste evaluations were done on fresh samples. The TBARS steaks were frozen aerobically after display and performed all at once at a later date.

Retail purge

The initial weight of the steaks was taken before being placed on the tray. After 7 d of display (0 to 6), steaks were weighed. The weight was then subtracted from the original weight and divided by the original weight and multiplied by 100 to represent percent purge during days of retail display.

Thiobarbituric acid reactive substances

TBARS assays were done on 3 steaks per treatment per day from days 0, 3, and 6 (n= 24) using the method described by Jimenez-Villareal and others (2003). Briefly, 2 mg of meat were homogenized with 8 mL of cold (2 °C) 50 mM phosphate buffer mix standardized to a pH of 7 and containing 0.1% EDTA and 0.1% propyl gallate and 2 mL of trichloroacetic acid (Sigma, St. Louis, Mo., U.S.A.). This was followed by filtration through Whatman Nr 4 filter paper (Whatman Intl. Ltd., Maidstone, England). Subsequently, 2 mL of clear supernatant were transferred in duplicate into 10 mL borosilicate tubes, 2 mL of 0.02 M 2-thiobarbituric acid reagent (Sigma) were added, and then boiled for 20 min. Upon cooking completion, tubes were placed in an ice bath for approximately 15 min and allowed to cool. Samples were read using a spectrophometer (Shimadzu Scientific Instruments, Inc., model UV-12015, Japan) at 533 nm. The absorbency was then multiplied using a factor of 12.21 to attain the TBARS value (mg malonaldehyde/kg of meat).

Warner–Bratzler shear force and cooking loss

After steaks were allowed to thaw to 2 °C, cooking loss of steaks was determined using the steaks for Warner–Bratzler shear force (WBS). Five steaks were chosen at random from each of the treatment groups (n= 40). After removal from their respective vacuum packages, steaks were weighed on a balance before cooking to obtain an initial steak weight. After cooling from cooking, steaks were weighed again and that weight was subtracted from the initial steak weight and divided by the initial steak weight and multiplied by 100 to convert the measure into a percent loss.

Striploin steaks (2.54 cm) were cooked in a Blodgett forced air convection oven (Blodgett Oven Co., Burlington, Vt., U.S.A.) until the internal temp of each steak reached 70 °C. Internal temperature was monitored every 5 s using Teflon-coated copper-constantan thermocouples (Omega Engineering, Inc., Stamford, Conn., U.S.A.) attached to a Doric multichannel data logger (VAS Engineering, Inc., San Diego, Calif., U.S.A.). After cooking, steaks were allowed to cool for approximately 2 h. When steaks reached room temperature, six 1.27 cm cores were attained parallel to the muscle fibers from each steak for WBS (AMSA 1995). Each core was then sheared with a Warner–Bratzler attachment on an Instron Universal Testing Machine (Instron Corp., Canton, Mass., U.S.A.) equipped with a 50 kg load cell and a 250-mm/min crosshead speed. The average of the 6 cores was used for the determination of peak shear force for each steak.

Sensory evaluation

On days 3, 4, 5, and 6, steaks were sampled by an 8-member trained sensory panel across 6 sessions. Each treatment was presented in each session, and then at random, 4 other treatments were chosen to be run so that each treatment appeared 2 times in 2 sessions and once in the other 4 session. Stratification made it so that the same 4 samples were not duplicated in the same session twice. Before each session, steaks were removed from their vacuum packages and cooked by means of the same method as described for WBS. Upon completion of cooking, steaks were cut into 1 × 1 cm cubes and placed in a food warmer (Alto-Shaam, Inc., Menomonee Falls, Wis., U.S.A.) at 63 °C for approximately 10 min. Panelists were then given each sample at their own pace in a booth with a designated random serving order with the sample being placed on 6-inch paper plates with the sample identification number. Between samples, panelists cleaned pallets using unsalted crackers and then taking a drink of water.

Panelists were selected (8) from the Univ. of Arkansas Dept. of Animal Science, and trained in accordance with the AMSA (1995) guidelines. To ensure that panelist were available and reliable for each session, they were compensated when the entire panel was completed. The panelists evaluated myofibrillar tenderness (initial bite), connective tissue (amount of defragmentation while chewing), overall tenderness, juiciness, and beef flavor on an 8-point scale (1 = extremely tough, abundant, extremely dry, extremely nonbeef like; 8 = extremely tender, none, extremely juicy, extremely beef like) while off-flavor was evaluated on a 5-point scale (1 = extreme off-flavor; 5 = no off-flavor). Tests were conducted under color neutralizing lights in partitioned booths to isolate panelists.

Instrumental color

Instrumental color readings of steaks placed under retail display conditions were measured using a Hunter Miniscan XE (Model 45/0-L, Hunter Associates Laboratory, Inc., Reston, Va., U.S.A.). The CIE L*, a*, and b* were determined from the average of 3 random readings from the surface of each steak using Illuminant A and a/10° standard observer. Hue angle was calculated using tan−1(b*/a*), and saturation index was calculated by square root (a*2+b*2).

Fatty acid methyl esters

Steaks that were destined for fatty acid (FA) analysis were frozen after packaging until assay could be performed. Upon time of analysis, steaks (n= 3 per treatment) were allowed to thaw to 1 °C, then were removed from their vacuum packages and divided in half, so that one half could be cooked for cooked analysis and the other half fresh for fresh analysis. Cooked sections were cooked in accordance with the Warner–Bratzler shear force method described previously. Samples, both fresh and cooked, were cubed into 15 g samples and freeze-dried in duplicate (7.5 g/duplicate). Samples were dried for 96 h utilizing a vacuum pressure of < 10 μm Hg at < –50 °C on a freeze-dryer (Labconco Corp., Kansas City, Mo., U.S.A.). Duplicates were then commingled and ground using a home-style electric coffee grinder. To avoid moisture uptake, ambient air exposure was kept to a minimum. Analysis of fatty acid methyl esters was based on the method of Murrieta and others (2003). Briefly, direct transesterification of duplicate 180 mg of dried muscle tissue was performed using 0.2 M KOH in anhydrous methanol as the catalyst and trideconoic acid as the internal standard. Fatty acid methyl esters were separated using a Hewlett-Packard 5890 GLC (Hewlett-Packard, Avondale, Pa., U.S.A.) with a flame ionization detector and a 100 m × 0.25 mm (i.d.) fused silica capillary column (SP-2560, 0.2 lm film thickness, Supelco, Bellefonte, Pa., U.S.A.). Fatty acids were determined by comparing retention times with acid methyl esters standards (Matreya Inc., Pleasant Gap, Pa., U.S.A.; Nu-Chek Prep Inc., Elysian, Minn., U.S.A.; Supelco).

Statistical analysis

All data were analyzed using Proc Mixed of SAS (SAS Inst. Inc., Cary, N.C., U.S.A.). To try to eliminate variation between muscles, muscles were sectioned into thirds, and each muscle was considered as a block and a randomized incomplete block design was utilized. Each treatment was randomly assigned to each section so that each treatment was present with each other treatment within a block. Treatments were evenly distributed across the muscle sections (anterior, medial, and posterior). Each treatment had 9 replicates. The model for cooking loss, retail purge, fatty acids, and WBS included the treatment due to subsampling within the reps. For assays that had the whole sample set, treatment was considered a fixed effect with muscle considered to be a random effect. For sensory taste, the model included treatment, and panelist, with muscle as a random effect. The model for instrumental color included the fixed effects of treatment and day and their interaction with muscle and treatment × muscle considered to be random effects. Day is considered to be a repeated measure and analyzed as such.

Treatment means were generated using the LSMEANS option of SAS and are presented in the tables as such. Means were separated using the PDIFF option of SAS when there was a significant (P < 0.05) treatment effect. In the event of an interaction for data measured over time, data were reanalyzed by day to examine differences within day.

Results and Discussion

Retail purge and cooking loss

Least squares means for retail purge and cooking loss are presented in Table 1. Control steaks had the highest retail purge among the treatments and were different (P < 0.05) from all other treatments except for CGA (P > 0.05) which was not different (P > 0.05) from any treatment. Salt and phosphate or the combination of the two allowed for lower purge among the treatments.

Table 1—.  Least squares means for physical characteristics of enhanced beef striploin steaks.
Treatmentsw*Retail purgezCook losszMarblingyShear force (kg)
  1. zValues are shown in percentage form.

  2. yMarbling scores = 550 = The first number is the level: 9 = abundant, 8 = moderately abundant, 7 = slightly abundant, 6 = moderate, 5 = modest, 4 = small, 3 = slight. The last 2 numbers are the degree of marbling within each respective level.

  3. wAll treatments except control were injected at 110% of initial weight.

  4. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

  5. a–cMeans within column, means without a common superscript, differ (P < 0.05).

CON8.17a27.55402b3.12ab 
CGA 5.35ab30.20574a3.47a
PCL3.65b30.71613a2.73bc 
PHO4.06b25.65414b2.34c  
SAL4.23b28.53424b2.67bc
SCL3.44b30.70598a2.84abc
SPH2.83b27.07417b2.21c
SPC2.82b23.41584a2.42bc
SEM1.35  1.78 18.80.26  

These results are in agreement with Pietrasik and others (2006), who found that inclusion of salt and phosphate reduced purge among beef and bison steaks. However, the results of Baublits and others (2007) are not in agreement, who found that CLA injected into beef striploins increased retail purge. Baublits most likely had increased purge because there was not any kind of salt or phosphate added to the brine.

There were no differences (P > 0.05) among treatments for cooking loss. Treatment SPC had the lowest mean value while PCL had the highest. The reason for the lack of differences among treatments is not known, but more likely a function of the lack of variability among the treatments.

Baublits and others (2007) found that with the inclusion of CLA only, cooking loss was increased as compared to the control; however, Pietrasik and others (2006) on beef and bison, Sheard and Tali (2004) on pork, and Baublits and others (2005) on beef found that cooking losses decreased with inclusion of salt and phosphate. Robbins and others (2003) found that inclusion of salt and phosphate had no effect on cooking losses.

Marbling

Least squares means for marbling scores are presented in Table 1. Marbling scores among the treatments were affected (P < 0.05) by the inclusion of CLA. Treatments with CLA had higher scores than those without CLA. Treatments with CLA showed it possible to increase marbling scores by up to 2 full score levels.

The increase in marbling is a novel effect and has only been shown by Baublits and others (2007). In that study, the researchers were able to increase the average marbling score by about 2 levels with the powdered CLA. In the present study, the same treatment group CGA was raised by nearly 2 levels, but had the lowest mean value among the other 3 treatments. However, even though that group was the lowest among the CLA treatments, it was still significantly higher than the treatments without CLA. In agreement with the results of Baublits and others (2007), and data that are presented make it evident that marbling scores can be increased with or without salt, phosphate, or the combination of the two using CLA.

Warner–Bratzler shear force

Least squares means for shear force are presented in Table 1. There was a treatment effect (P < 0.05) for shear force. Treatments SPH had the lowest mean shear force while CGA had the highest mean shear force. There is no explanation for the behavior of the treatments; however, although not significant, inclusion of salt, phosphate, or the combination of the two tended to allow for lower mean shear values.

The reasons for the values not being different from the control are not completely known. It should be noted, however, that although not significant, the treatments that did not have CLA in them such as SPH, SAL, and PHO all had lower shear values than their counterparts with CLA such as SCL, SPC, and PCL (SPH < SPC, PHO < PCL, SAL < SCL). The literature is in partial agreement. Baublits and others (2005, 2006a, 2007) found there to be no differences between treated steaks and control steaks in shear values on biceps femoris steaks enhanced with salt and phosphate and on stiploin steaks enhanced with CLA, respectively. Robbins and others (2003), McGee and others (2003), Sheard and Tali (2004), and Hayes and others (2006) with beef and pork, respectively, found that inclusion of salt and phosphate lowered shear values from the control.

Inclusion of salt and phosphate does have the ability to lower shear values as characterized by Baublits and others (2006b) as salt having an effect on the solubilization of the myofibrillar proteins and forming a water–protein matrix that allows for less force during shearing. It can also be an effect of the phosphate dissociating the actomyosin and allowing for less force during shearing (Trout and Schmidt 1983).

Fatty acid profiles

Fatty acid profiles for fresh steaks are presented in Table 2 and profiles for cooked steaks are presented in Table 3. Differences among treatments for fatty acids that are not of the CLA family, are considered to be a random effect of muscle, and are presented for brevity purposes.

Table 2—.  Least squares means for fatty acid profiles of fresh enhanced beef striploin steaks.z*
 CONCLAPCLPHOSALSCLSPHSPCSEM
  1. zValues are presented as mg fatty acid/g of dry tissue.

  2. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

  3. a–cMeans within row, without a common superscript, differ at the P < 0.05 level.

Total FA84.02113.3587.9086.07157.85129.49141.63137.1226.14
c10:00.0270.0370.0060.000.0640.0420.0470.0640.017
c12:00.0430.0390.0260.0180.080.0610.0750.0770.024
c14:02.502.371.802.394.353.184.783.560.92
c14:10.390.390.320.410.930.650.970.710.24
c15:00.320.370.270.370.720.460.660.580.16
c16:021.4621.9317.6321.8039.1528.6837.7029.906.98
c16:1t0.180.220.120.180.470.250.290.280.083
c16:1c2.603.12.252.775.844.025.623.851.09
c17:00.840.870.530.911.841.101.541.390.39
c17:1t0.000.0060.000.000.0430.000.000.000.016
c18:012.2012.5110.3611.7323.0414.5619.1817.043.76
c18:1t3.092.392.313.697.603.452.873.781.55
c18:1c928.5733.5026.3329.2657.3943.1753.2442.659.88
c18:1c111.762.762.202.003.903.283.603.570.67
c18:2n65.985.676.167.186.305.496.536.410.63
c18:3n30.250.310.260.240.570.370.330.340.08
c18:2c9;t110.22b10.89a6.87a0.23b0.73b8.03a0.26b8.82a1.51
c18:2t10;c120.00b11.19a7.43a0.00b0.00b8.69a0.00b9.55a1.64
c18:2c9c110.00b0.55a0.33a0.00b0.00b0.35a0.00b0.49a0.098
c18:2t9t11
c20:00.006b0.014b0.006b0.00b0.018b0.006b0.00b0.045a0.009
c20:10.0450.0640.0660.0370.1460.0240.1000.1710.049
c20:3n60.36a0.37a0.25b0.31ab0.34a0.35a0.0.31ab0.25b0.27
c20:4n61.441.241.141.201.081.351.291.020.134
c20:5n30.040.0710.0970.1080.0290.0130.000.1120.042
c22:5n30.280.330.330.330.280.240.160.260.043
Table 3—.  Least squares means for fatty acid profiles of cooked enhanced beef striploin steaks.z*
 CONCLAPCLPHOSALSCLSPHSPCSEM
  1. zValues presented as mg fatty acid/g dry tissue.

  2. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

  3. a–cMeans within row, without a common superscript, differ at the P < 0.05 level.

Total FA130.44170.99177.27126.33117.14123.89119.92141.6927.48
c10:00.0680.0750.0570.0270.0320.0450.0560.0470.018
c12:00.0870.0890.0620.0640.0340.0640.0740.0520.024
c14:04.394.284.013.582.653.163.903.040.92
c14:10.720.720.690.630.540.570.680.640.205
c15:00.660.700.710.640.410.460.520.440.17
c16:034.5836.2636.6131.5629.2128.1630.8126.556.35
c16:1t0.360.440.450.360.270.260.590.190.12
c16:1c4.195.385.074.283.813.774.673.441.01
c17:01.561.681.601.601.211.061.011.250.403
c17:1t0.000.0270.0450.000.000.0070.0160.000.02
c18:019.9820.8524.2317.9417.2615.4616.8715.364.26
c18:1t6.054.806.447.105.083.272.672.902.06
c18:1c943.5854.8557.4743.4143.7641.4044.9941.749.13
c18:1c112.994.223.992.883.053.363.593.130.63
c18:2n66.006.827.117.645.494.745.285.880.65
c18:3n30.390.520.460.390.380.370.310.340.083
c18:2c9;t110.48c11.23ab11.64ab0.45c0.31c6.48bc0.32c15.78a2.36
c18:2t10;c120.00c11.96ab12.25ab0.00c0.00c7.03bc0.00c16.97a2.43
c18:2c9c110.00c0.87ab0.84ab0.00c0.00c0.46bc0.00c1.30a0.164
c18:2t9t11
c20:00.046ab0.070a0.00c0.00c0.00c0.025bc0.031abc0.00c0.015
c20:10.0930.140.280.0980.0890.0070.110.0920.102
c20:3n60.280.360.220.280.320.290.240.160.04
c20:4n60.861.080.920.890.980.950.790.930.151
c20:5n30.0230.0790.0250.000.010.0180.0220.0310.016
c22:5n30.190.300.240.240.220.170.110.190.052

Fresh fatty acid analysis revealed as expected that inclusion of CLA allowed for greater (P < 0.05) amounts of CLA among treatments enhanced with CLA. This was present in all forms of CLA except for the isomer c18:2 trans 9; trans 11 which was not found in any of the samples.

Cooked fatty analysis revealed similar results to the fresh analysis, except for SCL not being different from the treatment without CLA. This is thought to be a function of cooking loss, due to the fact that SCL had higher cooking loss and was similar to PCL, although PCL retained its CLA better.

Our findings are in agreement with those of Baublits and others (2007) who found that the overall profile of the steaks was not affected. However, the CLA or 18:2 isomers (c9,t11; t10,c12; c9, c11; t9,t11) were affected and were significantly higher than that of the controls. With the exception of SCL, treatments with CLA increased in amount of mg per g of CLA in the dry tissue. The loss of water during cooking, but the higher concentrations CLA in the product expressed as milligram per gram dry tissue indicates the retention of the CLA in those muscles.

Sensory taste

Least squares means for sensory taste are presented in Table 4. Except for SAL, treatments with salt, phosphate, or the combination of the two tended to have better myofibrillar and overall tenderness among treatments. In both measures, SPH had the highest mean values, while CGA had the lowest. Treatment CGA had the lowest mean for connective tissue amount and was not different (P > 0.05) from CON, SAL, and SPC. Treatment PHO had the highest mean for connective tissue amount and was not different (P > 0.05) from PCL, SCL, SPH, and SPC. Except for not being different from CON, CGA was less juicy than the other treatments. Except for CON, treatments with salt, phosphate, or a combination of the two allowed for greater juiciness.

Table 4—.  Least squares means for sensory characteristics of enhanced beef striploin steaks.
Treatmentu*Myofibrillar tendernesswConnective tissue amountwOverall tendernesswJuicinessxBeef flavoryOff-flavorz
  1. uAll treatments except control were injected at 110% of initial weight.

  2. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

  3. a–dWithin a column, means without a common superscript differ (P < 0.05).

  4. w1–8 scale: 1 = extremely tough, abundant; 8 = extremely tender, none.

  5. x1–8 scale: 1 = extremely dry; 8 = extremely juicy.

  6. y1–8 scale: 1 = extremely nonbeef like; 8 = extremely beef like.

  7. z1–5 scale: 1 = extreme off-flavor; 5 = no off-flavor.

CON6.51c6.63bc6.47c5.81bc6.90d4.59cd
CGA6.25c6.58c6.26c5.46c6.98cd4.48d
PCL6.89ab6.94ab6.90ab6.11b7.09bc4.72abc
PHO7.17a7.19a7.14a6.54a7.19ab4.83a
SAL6.62bc6.64bc6.60bc6.20ab7.14abc4.76ab
SCL7.05a7.09a7.00a6.54a7.31a4.80ab
SPH7.21a6.98ab7.17a6.56a7.23ab4.86a
SPC7.02a6.85abc7.00a6.57a7.20ab4.64bcd
SEM0.160.150.150.170.070.06

Except for SAL not being different from CON and CGA, salt, phosphate, or the combination of the two allowed for better myofibrillar tenderness, overall tenderness, and juiciness. This is in agreement with several researchers (beef: McGee and others 2003; Robbins and others 2003; Baublits and others 2005; pork: Hayes and others 2006) who have all found that inclusion of salt and phosphate increases the tenderness and juiciness attributes of steaks. However, Baublits and others (2006a) found that phosphate alone in biceps femoris muscles had no effect on tenderness or juiciness attributes. Additionally, Baublits and others (2007) found that inclusion of powderized CLA, which is the same type used in the present study, increased tenderness ratings, which is in contrast to our results with treatment CGA. However, Baublits is in agreement with juiciness attributes, showing no differences between the control and CLA treatments.

For beef flavor, there were differences among treatments with SCL having the highest mean and CON having the lowest. However, it must be noted that even though there are differences among the treatments, the range was from 6.90 to 7.31 on an 8-point scale with 8 being extremely beef like. The same goes for off-flavor that showed differences among treatments, but the range of variation was from 4.59 to 4.86 on a 5-point scale with 5 being no off-flavor.

a* values

Least squares means for a* values are presented in Table 5. The interaction for treatment × day for a* values was not significant (P > 0.05). Therefore, the main effects of day and treatment are presented. As expected, there was a general decline in a* values form day 0 to day 6. Days 0 and 2 were not different (P > 0.05) from each other; however, days 4 and 6 were different (P < 0.05) from the other days. Treatment PHO had the highest mean and was not different (P > 0.05) from CON, PCL, and CGA, while SCL had the lowest mean and was different (P < 0.05) from all treatments except SAL. Treatments with salt (SPH, SPC, SAL, SCL), although not all were significant, had lower means than the other treatments.

Table 5—.  Main effect least squares means of enhanced beef striploin steaks for instrumental color characteristics.w
Treatmentz*a*b*Saturation indexy
  1. a–eWithin a column, with in an effect, means without a common superscript differ (P < 0.05).

  2. wa*: –60 = green, +60 = red; b*–60 = blue, +60 = yellow; Saturation index: higher values indicate greater vividness of red.

  3. ySaturation index calculated as: SQRT (a*2+b*2).

  4. zAll treatments except control were injected at 110% of initial weight.

  5. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

CON24.62ab19.39ab31.35ab
CGA23.65abc19.06abc30.40ab
PCL23.76abc18.33bcd30.04bc
PHO25.21a20.04a32.22a
SAL20.96de18.02cd27.72de
SCL20.24e16.28e26.02e
SPH23.56bc18.03cd29.68bc
SPC22.17cd17.34de28.17cd
SEM0.570.390.66
Day
 024.61a18.61ab30.88a
 223.93a18.88a30.49a
 422.84c18.35b29.32b
 620.69d17.40c27.10c
SEM0.280.180.32

Baublits and others (2007) are in agreement with CGA not being different from CON. Baublits and others (2006b) are also in agreement with the phosphate only and phosphate and salt not being different from that of the control. Robbins and others (2003) found on beef clods that control clods had greater a* values than their enhanced counterparts. It is the feeling of the researchers that the 2 treatments SAL and SCL had the lowest a* values because salt is a prooxidant and that without a chelator or buffer, such as a phosphate, that the increased oxidation that was present in these 2 treatments caused the decrease in the redness of the steaks.

b* values

Least squares means for b* values are presented in Table 5. The interaction of treatment × day was not significant, so main effects of day and treatment are presented. Day was significant, and as expected, there was a general decline in values across the days, except for day 2, which had a higher mean than day 0, but was not different (P > 0.05). Days 0 and 2 were not different (P > 0.05), 0 and 4 were not different (P > 0.05), and day 6 was different (P < 0.05) from all other days. Treatment PHO had the highest mean and was not different (P > 0.05) from CON and CLA, while SCL had the lowest mean and was different (P < 0.05) from all other treatments except for SPC. Once again, although not all means were significantly different, treatments with salt had lower means than treatments without salt.

Once again, the salt treatments having lower mean values are most likely due to the prooxidant nature of salt. Salt can interfere with oxygen solubility and the formation of oxymyoglobin causing a reduction in b* values (Fernandez-Lopez and others 2004).

L* values

Least squares means for L* values are presented in Table 6. The treatment × day interaction was significant (P < 0.05) for L* values. Due to the interaction, means were reanalyzed by day to examine differences closer. This interaction resulted from CGA and PCL being the same on day 0 (P > 0.05), different on days 2 and 4 (P < 0.05), and then the same again on day 6 (P > 0.05).

Table 6—.  Treatment × day interaction least squares means for L* values of enhanced beef striploin steaks.y
Treatmentsz*Day 0Day 2Day 4Day 6
  1. a–eWithin a column, means without a common superscript differ (P < 0.05).

  2. yL*; 0 = black, 100 = white.

  3. zAll treatments except control were injected at 110% of initial weight.

  4. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

CON42.23bc39.14d37.80d37.04cd
CGA47.15a48.51a47.24a46.41a
PCL44.39ab44.84bc43.93b43.70a
PHO38.01e38.00de37.68d36.91cd
SAL41.39cd39.99d39.76cd37.62c
SCL45.67a46.87ab47.36a45.12a
SPH38.82de35.42e34.29e34.58d
SPC45.54a43.18c42.04bc40.68b
SEM1.010.951.061.02

It should be noted that all treatments with CLA had greater mean values than the treatments without CLA. This is due to the white nature of the CLA showing up in and on the muscle. Baublits and others (2007) also noticed an increase in L* values in treatments with CLA as compared to the control. If the 2 factions of the treatments are separated such as to have those with CLA and those without, it is seen that the treatments that had both salt and phosphate (SPC and SPH) had lower L* values than their other 3 counterparts in each of their respective groups. This is likely due to the increased water retention causing a darker surface color and decreased oxygen penetration (Baublits and others 2006b). Robbins and others (2003) found that enhanced beef clods, superficial semimembranosus, and deep semimembranosus were all darker than the controls. However, in pork, Hayes and others (2006) found no differences between enhanced and control chops.

Hue angle

Least squares means for hue angle are presented in Table 7. The treatment × day interaction was significant (P < 0.05) for hue angle. Data were reanalyzed by day to examine differences. The reasoning for the interaction was due to CGA and PCL being different on day 2 (P < 0.05), but not being different on days 4 and 6 (P > 0.05). The other reason is one of magnitude, with SAL having a greater increase in value than the other treatments across the days of display.

Table 7—.  Treatment × day interaction least squares means for enhanced beef striploin steaks for hue angle.y
Treatmentz*Day 0Day 2Day 4Day 6
  1. a–dWithin a column, means without a common superscript differ (P < 0.05).

  2. ylower values indicate a redder color.

  3. zAll treatments except control were injected at 110% of initial weight.

  4. *CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error).

CON37.2138.26bc38.39bc38.99b
CGA37.5039.00b39.19b40.89b
PCL36.4437.49cd37.92bc39.86b
PHO36.7738.32bc38.93bc40.03b
SAL37.7240.13a41.31a45.43a
SCL37.1038.20bc39.12b41.86b
SPH36.5337.18d37.74c38.79b
SPC37.2737.56cd38.01bc39.08b
SEM0.400.320.481.11

Treatment SAL having the highest hue angle can be justified in 2 ways, first, salt is a prooxidant and without having a chelator in the solution, allows for oxidation to proceed without hesitation. The other being, the a* and b* values are closer in value. Either way, although not all significant, the 2 treatments with salt tended to have the 2 highest mean values on day 6, indicating a greater loss of redness than the other treatments. The application of CLA seemed to have no effect on hue angle as the treatments that had CLA were dispersed with in the other treatments. Baublits and others (2007) in agreement with our results, found no differences between powderized CLA, which is what was used in this study, and the control steaks. Fernandez-Lopez and others (2004) found on pork that salt increased hue angles when compared to controls.

Saturation index

Least squares means for saturation index values are presented in Table 5. The treatment × day interaction was not significant, therefore, main effects of day and treatment are presented. Days 0 and 2 were not different (P > 0.05); however, days 4 and 6 were different (P < 0.05) from each other and the other 2 treatments. As expected, there was a general decline in values among treatments across days. Treatment PHO had the highest mean and was not different (P > 0.05) from CON and CLA. Treatment SCL had the lowest mean and was different (P < 0.05) from all other treatments except for SAL. Once again, treatments with salt, although not significant, had lower mean values than treatments without salt.

In agreement with our results is Baublits and others (2006b) with PHO, and SPH having similar saturation indexes as CON. Additionally, Baublits and others (2007) found no differences between powder CLA treatments and CON, which is also in agreement with the present study (CON = CGA). The salt treatments (SAL and SCL) having lower indexes than that of the controls is in agreement with Fernandez-Lopez and others (2004) who found with pork that treatments with salt without a chelator had decreased values.

TBARS

Least squares means for TBARS are presented in Figure 1. Main effects of treatment and day both were significant; however, there interaction was not. All 3 d were different from each other with an expected increase in value on each day. Treatment means found PHO to have the lowest mean value among treatments while SCL had the highest. Treatments SAL, SCL, and SPC were not different (P > 0.05) while all of the other treatments were not different from each other. Treatment SPC was not different (P > 0.05) from any treatment.

Figure 1—.

TBARS for enhanced striploin steaks.
*CON (control); CLA (1.5% CLA); PHO (0.4% sodium tripolyphosphate); SAL (0.5% salt); SPH (0.4% sodium tripolyphosphate, 0.5% salt); PCL (0.4% sodium tripolyphosphate, 1.5% CLA); SCL (0.5% salt, 1.5% CLA); SPC (0.4% sodium tripolyphosphate, 0.5% salt, 1.5% CLA); SEM (standard error). SEM for treatments = 0.10, SEM for day = 0.06.

Treatments with salt only or salt and CLA only had the highest (P < 0.05) amounts of oxidation which is expected due to the prooxidant nature of salt. Baublits and others (2007) found that the treatment with CLA had lower TBARS values than that of the controls. However, it should be noted that there were antioxidants included in the commercial blend of the CLA; however, this was only in partial agreement to our results.

Conclusions

The results from the current study show that the use of CLA can effectively increase marbling scores of steaks. Palatability is not impacted as long as there is phosphate or salt or both in the solution. However, treatments with salt and without phosphate showed increased oxidation levels. More research is needed to determine better distribution and use of other ingredients to curb oxidation and enhance instrumental color.

Acknowledgments

The authors would like to thank the Arkansas Beef Council for funding this study and Tyson Foods, Inc. for their support with muscles. Additionally, the authors would like to thank P. Dias-Morse, S. Quilo-Ortiz, Donna Delozier, and the panelists for their sensory help.

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