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Objectives were to evaluate effects of fat source and formulated fat percentage on fatty acid composition, lean color stability, lipid oxidation, and aerobic microbial load during simulated retail display of ground beef patties. In Experiment 1 beef carcasses (
Consumer purchasing intent is driven by color (
Multiple studies have shown that microbial growth is an important factor in controlling the spoilage of meat (
Crossbred beef steers (
Extractable fat and moisture determination was performed on the day the meat was ground on each source and fat percentage combination (6 samples per animal) according to
Methodology utilized for fatty acid quantification was an adaptation of the methods used by
Lipid oxidation products were determined using the thiobarbituric acid reactive substances (TBARS) extraction method described by
Statistical Analysis for proximate analysis and fatty acid profiles was performed using the MIXED procedure of SAS (Version 9.4, SAS Inst. Inc., Cary, NC) to obtain least square means and standard error estimates. The model included the fixed effects of fat source (KP and S) and fat percentage (5 and 25%) and all possible interactions. Objective color and TBARS were analyzed using the MIXED procedure of SAS and the model included the fixed effects of fat source, fat percentage, day (1, 3, 5, or 7), and all possible interactions. Significance was determined at
Crossbred beef steers (
Fat and moisture percentage determination was performed in triplicate as described in Experiment 1.
Surface color measurements (L*, a*, b*) of the ground beef patties were acquired utilizing a HunterLab MiniScan model 4500L (Hunter Associates Laboratory, Reston, VA) with a D65 light source, 1.27 cm aperture, geometry 45°/0° and physical standard was used to calibrate the MiniScan each day. Color coordinates were recorded on each sample’s specific day of removal from simulated retail display. On the first day of simulated retail display, all of the d 1 patties were measured prior to removal from the case for further analysis. This was continued on d 3, 5, and 7 of the study. Samples were evaluated in triplicate and averaged to achieve a more accurate representation of each ground beef patty.
Myoglobin concentrations of the ground beef samples were calculated via selected wavelengths described in the Meat Color Measurements Guidelines (
Hue angle (HA), saturation index (SI), and a*/b* ratios were determined according to
A total of 15 trained panelists participated in the ground beef sensory panel to determine odor and visual characteristics throughout shelf life of ground beef patties by methods described by
Lipid oxidation products were determined using the TBARS extraction method in duplicate as described in Experiment 1.
Samples from each treatment were processed APC on d 1 and d 7. Duplicate 25 g portions of ground beef were weighed from 2 patties from each treatment for a total of four replications per treatment. Each 25-g sample was placed in separate sterile stomacher bag (Whirl-pak, Nasco) and homogenized in 225 mL of sterile 0.1% peptone water (BD Difco, Fisher Scientific) for 2 min (Seward Stomacher Model # 400C, Fisher Scientific, Pittsburgh, PA). Samples were serially diluted in sterile 0.1% peptone water at dilutions of 10–1 to 10–4 and 1 mL of each dilution was pour plated in approximately 20 mL of plate count agar. Plates were incubated at 5°C for 7 d. After the incubation period, colonies were manually counted, recorded, averaged and expressed as colony forming unit (CFU)/g. The minimum detection limit for determining APC was 10 CFU/g or 1 colony at 10–1.
Statistical analysis for fat and moisture determination was performed using the MIXED procedure of SAS (Version 9.4, SAS Inst. Inc., Cary, NC) to obtain LS means and SE estimates. The model included the fixed effects of fat source (KP and S) and fat percentage (5 and 25%) and all possible interactions. Furthermore, statistical analysis for TBARS values, myoglobin percentages, color scores and sensory panel scores was performed using the repeated measures option in the MIXED procedure of SAS and the model included the fixed effects of fat source, fat percentage, d (1, 3, 5, or 7), and all possible interactions. Significance was determined at
Ground beef made with S fat had a greater percentage of fat, monounsaturated fatty acids (MUFA), greater IV and TBARS values than ground beef made with KP fat (
Effect of fat source1 on ground beef fatty acid composition2 and lipid oxidation
Item | S ( | KP ( | SEM | |
Fat, % | 15.69a | 14.80b | 0.28 | 0.0284 |
Moisture, % | 63.26 | 63.82 | 0.23 | 0.0888 |
SFA, % | 52.17b | 57.96a | 1.08 | 0.0002 |
MUFA, % | 37.59a | 33.12b | 1.16 | 0.0076 |
PUFA, % | 5.50 | 5.15 | 0.23 | 0.2833 |
SFA/PUFA | 10.80b | 15.52a | 1.22 | 0.0074 |
n-33, % | 0.32 | 0.26 | 0.04 | 0.2273 |
n-64, % | 4.53 | 4.26 | 0.22 | 0.4027 |
n-3/n-6 | 0.10 | 0.10 | 0.02 | 0.9337 |
IV5 | 38.32a | 33.95b | 1.03 | 0.0032 |
TBARS6 | 0.117a | 0.107b | 0.007 | 0.0101 |
a,bData within a row lacking a common superscript differ
1S = subcutaneous fat; KP = kidney and pelvic fat.
2Percent of total fatty acids detected.
3Omega-3 fatty acids.
4Omega-6 fatty acids.
5Calculated iodine value.
6Thiobarbituric acid reactive substances expressed as mg malonaldehyde/kg sample;
Fat and moisture percentages differed (
Effect of formulated fat percentage on ground beef fatty acid composition1 and lipid oxidation
Item | 5% ( | 25% ( | SEM | |
Fat, % | 6.89b | 23.61a | 0.28 | < 0.0001 |
Moisture, % | 69.98b | 57.10a | 0.23 | < 0.0001 |
SFA, % | 50.70b | 59.44a | 1.08 | < 0.0001 |
MUFA, % | 38.75a | 31.97b | 1.16 | < 0.0001 |
PUFA, % | 5.96a | 4.69b | 0.23 | 0.0002 |
SFA/PUFA | 10.02b | 16.31a | 1.22 | 0.0004 |
n-32, % | 0.31 | 0.27 | 0.04 | 0.4473 |
n-63, % | 5.08a | 3.71b | 0.22 | < 0.0001 |
n-3/n-6 | 0.07 | 0.12 | 0.02 | 0.0600 |
IV4 | 39.95a | 32.32b | 1.03 | < 0.0001 |
TBARS5 | 0.112 | 0.111 | 0.007 | 0.7848 |
a,bData within a row lacking a common superscript differ
1Percent of total fatty acids detected.
2Omega-3 fatty acids.
3Omega-6 fatty acids.
4Calculated iodine value.
5Thiobarbituric acid reactive substances expressed as mg malonaldehyde/kg sample;
Effect of storage day on ground beef lipid oxidation (
Item | 1 | 3 | 5 | 7 | SEM | |
TBARS1 | 0.104b | 0.087c | 0.113b | 0.143a | 0.008 | < .0001 |
a–cData within a row lacking a common superscript differ
1Thiobarbituric acid reactive substances expressed as mg malonaldehyde/kg sample.
Ground beef made with S had higher (
Effect of fat source1 on lipid oxidation, color and odor of ground beef
Item | S ( | KP ( | SEM | |
Fat2, % | 14.7 | 14.5 | 0.30 | 0.6033 |
Moisture2, % | 63.8 | 63.6 | 0.33 | 0.7677 |
TBARS3 | 0.113 | 0.119 | 0.007 | 0.3502 |
L* | 44.82a | 44.41b | 0.35 | 0.0403 |
a* | 16.60 | 16.72 | 0.24 | 0.2276 |
b* | 18.89b | 19.28a | 0.14 | 0.0021 |
a/b | 0.88 | 0.87 | 0.01 | 0.2013 |
SI | 25.27a | 25.38b | 0.23 | 0.0098 |
HA | 48.99 | 49.20 | 0.33 | 0.1899 |
OMb, % | 51.87b | 52.33a | 0.21 | 0.0009 |
Fruity/sweet | 0.9 | 1.0 | 0.04 | 0.1696 |
Sour | 0.9 | 1.0 | 0.05 | 0.6707 |
Putrid | 0.3 | 0.4 | 0.05 | 0.6264 |
Discoloration | 0.4 | 0.4 | 0.07 | 0.3978 |
Color | 5.3 | 5.3 | 0.09 | 0.5947 |
a,bData within a row lacking a common superscript differ
1S = subcutaneous fat; KP = kidney and pelvic fat.
2
3Thiobarbituric acid reactive substances expressed as mg malonaldehyde/kg sample.
4SI = saturation index; HA = hue angle; OMb = oxymyoglobin.
5Fruity/sweet, sour, putrid 0 = no odor and 7 = extreme odor; discoloration 0 = no discoloration and 7 = complete discoloration; color 1 = dark brownish– greenish gray, 2 = light brownish– greenish gray, 3 = light gray, 4 = moderately dark red, 5 = slightly dark red, 6 = cherry red, 7 = moderately light cherry red, 8 = very light cherry red.
Increasing percent of added fat from 5 to 25% increased (
Effect of formulated fat percentage on lipid oxidation, color and odor of ground beef
Item | 5% ( | 25% ( | SEM | |
Fat1, % | 6.5b | 22.7a | 0.30 | < 0.0001 |
Moisture1, % | 70.1a | 57.4b | 0.33 | < 0.0001 |
TBARS2 | 0.122 | 0.109 | 0.007 | 0.1199 |
L* | 39.37b | 49.86a | 0.35 | < 0.0001 |
a* | 17.65a | 15.68b | 0.24 | < 0.0001 |
b* | 18.37b | 19.90a | 0.14 | < 0.0001 |
a/b | 0.96a | 0.79b | 0.01 | < 0.0001 |
SI | 25.49 | 25.36 | 0.23 | 0.2599 |
HA | 46.27b | 51.91a | 0.33 | < 0.0001 |
OMb, % | 49.74b | 54.46a | 0.23 | < 0.0001 |
Fruity/sweet | 1.1a | 0.8b | 0.04 | < 0.0001 |
Sour | 1.0 | 0.9 | 0.05 | 0.5994 |
Putrid | 0.3 | 0.4 | 0.05 | 0.2569 |
Discoloration | 0.2b | 0.6a | 0.07 | < 0.0001 |
Color | 4.5b | 6.1a | 0.09 | < 0.0001 |
a,bData within a row lacking a common superscript differ
1
2Thiobarbituric acid reactive substances expressed as mg malonaldehyde/kg sample.
3SI = saturation index; HA = hue angle; OMb = oxymyoglobin.
4Fruity/sweet, sour, putrid 0 = no odor and 7 = extreme odor; discoloration 0 = no discoloration and 7 = complete discoloration; color 1 = dark brownish– greenish gray, 2 = light brownish– greenish gray, 3 = light gray, 4 = moderately dark red, 5 = slightly dark red, 6 = cherry red, 7 = moderately light cherry red, 8 = very light cherry red.
As storage day increased, a*, b*, a/b, and saturation index values decreased (
Effect of simulated retail display day on lipid oxidation, color and odor of ground beef
Item | 1 ( | 3 ( | 5 ( | 7 ( | SEM | |
TBARS1 | 0.119 | 0.098 | 0.127 | 0.116 | 0.009 | 0.0713 |
L* | 44.72 | 44.47 | 44.50 | 44.077 | 0.38 | 0.6565 |
a* | 19.34a | 16.71b | 15.66c | 14.95d | 0.25 | < 0.0001 |
b* | 20.79a | 19.09b | 18.58c | 18.08d | 0.15 | < 0.0001 |
a/b | 0.93a | 0.88b | 0.85c | 0.83d | 0.01 | < 0.0001 |
SI | 28.44a | 25.41b | 24.34c | 23.51d | 0.25 | < 0.0001 |
HA | 47.12d | 48.85c | 49.95b | 50.45a | 0.35 | < 0.0001 |
MMb, % | 35.9d | 39.4c | 41.2b | 42.2a | 0.32 | < 0.0001 |
DMb, % | 9.1a | 8.0b | 8.0b | 7.9b | 0.29 | < 0.0001 |
OMb, % | 55.0a | 52.6b | 50.8c | 50.0d | 0.21 | < 0.0001 |
Fruity/sweet | 1.0a | 1.0a | 0.8b | 0.9ab | 0.05 | 0.0354 |
Sour | 1.0a | 1.1a | 0.9b | 0.8b | 0.06 | < 0.0001 |
Putrid | 0.4 | 0.4 | 0.3 | 0.3 | 0.06 | 0.0768 |
Discoloration | 0.3 | 0.5 | 0.4 | 0.4 | 0.08 | 0.1877 |
Color | 5.3 | 5.2 | 5.3 | 5.3 | 0.1 | 0.4136 |
a–dData within a row lacking a common superscript differ
1Thiobarbituric acid reactive substances expressed as mg malonaldehyde/kg sample.
2SI = saturation index; HA = hue angle; MMb = metmyoglobin; DMb = deoxymyoglobin; OMb = oxymyoglobin.
3Fruity/sweet, sour, putrid 0 = no odor and 7 = extreme odor; discoloration 0 = no discoloration and 7 = complete discoloration; color 1 = dark brownish– greenish gray, 2 = light brownish– greenish gray, 3 = light gray, 4 = moderately dark red, 5 = slightly dark red, 6 = cherry red, 7 = moderately light cherry red, 8 = very light cherry red.
An interaction between fat source and added fat percentage (
Effect of fat source1 and formulated fat percentage on myoglobin state of ground beef
Item2 | S | KP | SEM | |||
5 ( | 25 ( | 5 ( | 25 ( | |||
MMb, % | 39.7b | 39.5b | 39.5b | 40.0a | 0.32 | < .0001 |
DMb, % | 10.8a | 6.3b | 10.5a | 5.3c | 0.29 | 0.0057 |
a–cData within a row lacking a common superscript differ
1S = subcutaneous fat; KP = kidney and pelvic fat.
2MMb = metmyogloblin; DMb = deoxymyoglobin.
APC data revealed very low levels of aerobic bacterial ranged from 102 CFU/g on d 1 to 103 CFU/g on d 7 of simulated retail display (data not presented in tabular form). Fat source did not affect (
Research has shown that various fat depots in the beef carcass have different fatty acid profiles, thus resulting in different subjectivity to lipid oxidation and shelf life in retail ground beef products (
Results also showed that the 2 formulated fat percentage treatments differed (
Patties with 5% fat, on average, were between moderately dark red and slightly dark red; whereas, patties containing 25% fat were most commonly called cherry red which agrees with
Our data showed TBARS values fluctuating over the simulated retail display, this has been reported before by
Many reviews have suggested the link between lipid oxidation and myoglobin oxidation (
We found no difference in L* value due to storage day or sensory panel color score. Similar findings showed no difference (
Redness (a* values) decreased over retail display (
Day also effected (
Metmyoglobin concentrations increased (
Data from this study reports slight changes in fruity/sweet and sour odors over time. However it should be noted the magnitude of the sensory scores is very low. This contradicts other researchers (
The use of KP as a fat source in ground beef may decrease lipid oxidation without affecting color because it has higher SFA levels compared to S. Discoloration in ground beef over 7 d of retail display was more a function of muscle pigment oxidation (OMb to MMb) than aerobic microbial spoilage. This research confirmed that desirable color in ground beef decreases over storage day. However, other contradicting results between the two experiments and cited literature were most likely due to low storage temperatures in the simulated retail display.
Funded in part by the Beef Checkoff.