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Use of double packaging and antioxidant combinations to improve color, lipid oxidation, and volatiles of irradiated raw and cooked turkey breast patties
PROCESSING AND PRODUCTS Use of Double Packaging and Antioxidant Combinations to Improve Color, Lipid Oxidation, and Volatiles of Irradiated Raw and Cooked Turkey Breast Patties1 K. C. Nam and D. U. Ahn2 Department of Animal Science, Iowa State University, Ames, Iowa 50011-3150 radiated control. Irradiated aerobically packaged meat had accelerated lipid oxidation and aldehyde production at 10 d and after cooking. Gallate + α-tocopherol alone with double packaging was effective in reducing the red color of irradiated meat at 10 d and after cooking. Considerable amounts of off-odor volatiles were reduced by double packaging and antioxidant treatment. Sulfur volatiles were evaporated during the aerobic period of double packaging, and lipid oxidation was prevented by the antioxidants and vacuum condition of double packaging. These beneficial effects of double packaging and antioxidants were more critical in irradiated cooked meat. Therefore, the combined use of antioxidants and double packaging would be a useful method to control the oxidative quality changes of irradiated raw and cooked turkey breast.
(Key words: antioxidant, double packaging, irradiated turkey, lipid oxidation, volatiles) 2003 Poultry Science 82:850–857
secondary reactions of free radicals generated by irradiation with meat components are believed to be the main cause of these quality changes. Woods and Pikaev (1994) and Ahn et al. (1997) reported that antioxidants reduce oxidative quality deterioration of irradiated meat by quenching free radicals. Nam and Ahn (2002b) showed that gallate or sesamol combined with α-tocopherol decreases production of sulfur volatiles as well as lipid oxidation in irradiated pork patties. Packaging is also a critical factor influencing the quality of irradiated meat. Under vacuum conditions, almost all sulfur volatiles generated by irradiation are retained in meat (Ahn et al., 2000b; Ahn et al., 2001; Nam et al., 2001), and the intensity of pink color in irradiated meat increases during storage (Luchsinger et al., 1996; Nam and Ahn, 2002a). Under aerobic conditions, almost all sulfur volatiles generated by irradiation disappear, and pink color intensity decreases after a few days of storage. Lipid oxidation in irradiated meat during storage was
INTRODUCTION Although irradiating is the best method to ensure the microbiological safety of raw meat (Lambert et al., 1991), it caused a few radiolytic meat quality defects. Irradiated pork and poultry meat accelerate lipid oxidation (Katusin-Razem et al., 1992; Ahn et al., 2000a), produce a characteristic off-odor (Patterson and Stevenson 1995; Du et al., 2000; Ahn et al., 2001), and develop a pink color (Lynch et al., 1991; Nanke et al., 1998; Nam and Ahn, 2002a). Jo and Ahn (2000) elucidated that sulfur volatiles produced by radiolytic degradation of sulfur amino acids are responsible for the irradiation off-odor, and Nam and Ahn (2002a) characterized the pink color in irradiated turkey breast as the complex of heme pigment and radiolytic carbon monoxide. The primary and
2003 Poultry Science Association, Inc. Received for publication February 13, 2002. Accepted for publication December 18, 2002. 1 Journal Paper No. J-19735 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project No. 3706, and supported by NRI. 2 To whom correspondence should be addressed: [email protected].
Abbreviation Key: a* = redness; b* = yellowness; CO-Mb = carbon monoxide-myoglobin; L* = lightness; TBARS, 2-thiobarbituric acid reactive substances.
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ABSTRACT The effects of antioxidants and double packaging combinations on color, lipid oxidation, and volatiles production in irradiated raw and cooked turkey breast were determined. Ground meat was treated with antioxidants (none, sesamol + α-tocopherol, or gallate + αtocopherol), and patties were prepared. The patties were packaged under vacuum, packaged aerobically, or double packaged (vacuum for 7 d then aerobic for 3 d) and electron beam irradiated at 3 kGy. Color, 2-thiobarbituric acid-reactive substances (TBARS), and volatile profiles of the samples were determined at 0 and 10 d and after cooking. Irradiated vacuum-packaged patties had great amounts of sulfur volatiles (dimethyl sulfide and dimethyl disulfide) and increased red color during refrigerated storage and after cooking compared with the nonir-
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY
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TABLE 1. Packaging, irradiation, and antioxidant treatments used in this study Treatment
Irradiation (kGy)
Antioxidant (100 ppm each)
Packaging method
0 3 3 3 3 3
Not added Not added Not added Not added Sesamol, α-tocopherol Gallate, α-tocopherol
Vacuum for 10 d Vacuum for 10 d Aerobic for 10 d Vacuum for 7 d then aerobic for 3 d Vacuum for 7 d then aerobic for 3 d Vacuum for 7 d then aerobic for 3 d
Nonirradiated-vacuum packaged Irradiated-vacuum packaged Irradiated-aerobic packaged Irradiated-double packaged Irradiated-double packaged/S+E1 Irradiated-double packaged/G+E2 1
Sesamol (100 ppm) and α-tocopherol (100 ppm) added. Gallic acid (100 ppm) and α-tocopherol (100 ppm) added.
2
MATERIALS AND METHODS Treatments A total of 36 male Large White turkeys (16 wk old) were slaughtered, and then carcasses were chilled in ice water for 3 h and drained in a cold room. Breast muscles were deboned from the carcasses 24 h after slaughter. Skin and visible fat were removed. Breast meats from six birds were pooled from and used as a replication. Meats for each replication were ground through a 3-mm plate, and four replications were prepared. Six different treatments were prepared using antioxidant, packaging method, and irradiation conditions (Table 1). Vitamin E + sesamol and vitamin E + gallate combinations were used in this study, because these antioxidant combinations were most effective in reducing lipid oxidation and off-odor volatiles in irradiated turkey meat (Nam and Ahn, 2002b). Sesamol3 (3,4-methylenedioxyphenol) plus α-tocopherol4 or gallate3 (3,4,5-trihydroxybenzoic acid) plus α-tocopherol was mixed with the ground turkey meat each at 100 ppm (final 200 ppm) using a bowl mixer5 (Model KSM 90). The mixed meat samples were ground again through a 3-mm plate to ensure uniform
3
Sigma Chemical Co., St. Louis, MO. Aldrich Chemical Co., Milwaukee, WI. 5 Kitchen Aid, Inc., St. Joseph, MI. 6 Koch, Kansas City, MO. 7 Associated Bag Company, Milwaukee, WI. 8 Thomson CSF Linac, Saint-Aubin, France. 9 Bruker Instruments Inc., Billerica, MA. 10 Hunter Associated Labs, Inc., Reston, VA. 4
distribution of the added antioxidants. Other treatments without antioxidants were also put through the same mixing process to provide the same preparation conditions as antioxidant-added treatments. About 50 g of turkey breast patties was prepared from each treatment and then individually vacuum packaged in high oxygen-barrier bags6 (nylon-polyethylene, 9.3 mL O2/m2 per 24 h at 0°C), aerobically packaged in polyethylene oxygen-permeable bags7 (polyethylene, 2 mil), or double packaged. For double packaging, aerobically packaged patties were repackaged in oxygen-impermeable vacuum bags. The packaged patties were irradiated at 2.5 kGy using a linear accelerator8 (Circe IIIR) with 10 MeV of energy, 10 kW of power, and 86.2 kGy/min of average dose rate. To confirm the target dose, two alanine dosimeters per cart were attached to the top and bottom surfaces of the sample and were read using a 104 Electron Paramagnetic Resonance instrument9 (EMS-104). Nonirradiated vacuum-packaged patties were prepared as a control. The outer vacuum bags of double-packaged meat were removed after 7 d of storage at 4°C to expose the samples under aerobic conditions. Color, lipid oxidation, and volatile compounds of the irradiated raw meats were determined at 0 and 10 d of refrigerated storage. Part of the raw meat stored for 10 d was cooked in a 90°C water bath (cooked in bag) to an internal temperature of 75°C. The surface and internal colors, lipid oxidation, and volatiles of the cooked meat were determined after cooling the meat to room temperature.
Color Measurement The CIE color values were measured on the surface of sample using a LabScan color meter10 that had been calibrated against black and white reference tiles covered with the same packaging materials as used for the samples. The CIE lightness (L*), redness (a*), and yellowness (b*) values were obtained using an illuminant A (light source) with an area view of 0.25 inch and a port size of 0.40 inch. Two random locations of both top and bottom surfaces of the samples were measured. For the internal color of cooked meat, the patties were horizontally dissected, and the internal central locations were measured.
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accelerated only under aerobic conditions (Katusin-Razem et al., 1992; Ahn et al., 2000b). Therefore, exposing irradiated meat to aerobic conditions for a limited period of time could lower irradiation off-odor odor and decrease pink color intensity, and subsequent storage under vacuum could minimize lipid oxidation. Addition of antioxidants thus can prevent quality deterioration of irradiated double-packaged meat during storage. The objective of this study was to determine the effects of double packaging and antioxidant combinations on color, lipid oxidation, and volatiles of irradiated raw turkey breast during refrigerated storage and after cooking.
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NAM AND AHN TABLE 2. CIE color values of irradiated turkey breast patties treated by different packaging and antioxidants during the 10 d of storage and after cooking Nonirradiated
Irradiated Double packaging2
Vacuum packaging
Aerobic packaging
None
S+E3
G+E4
SEM
L* value 0d 10 d Cooked5 (surface) Cooked (inside) SEM
54.29abz 54.44bz 84.38ax 82.05y 0.52
55.36az 56.88ay 84.73ax 84.30x 0.38
55.39ay 56.71ay 83.65ax 82.65x 0.55
55.20ay 56.14ay 84.41ax 83.73x 0.35
53.57bz 54.03bz 84.71ax 82.39y 0.32
53.59by 53.44by 81.70bx 81.98x 0.71
0.29 0.37 0.31 0.81
a* value 0d 10 d Cooked5 (surface) Cooked (inside) SEM
4.42cz 4.67dz 5.96by 7.50cx 0.16
7.95ay 7.89ay 7.53ay 10.04ax 0.24
7.15bx 5.66cy 3.99cz 5.58dy 0.14
6.95by 4.68dz 5.55bz 7.51cx 0.18
6.74bx 5.63cy 4.51cz 5.75dy 0.18
0.13 0.11 0.21 0.23
b* value 0d 10 d Cooked5 (surface) Cooked (inside) SEM
9.63aby 9.18dy 14.87abx 14.99abx 0.43
9.79az 9.55cdz 16.60ax 15.25aby 0.26
9.62abz 12.08ay 14.06bx 15.96ax 0.24
8.58cz 11.29by 15.70abx 15.22abx 0.33
8.59cz 9.86cy 14.29bx 14.44bx 0.38
0.15 0.18 0.50 0.33
Storage1
7.74axy 6.98by 6.20bz 8.62bx 0.13 9.14bz 11.37by 16.67ax 15.95ax 0.25
Different letters within a row are significantly different (P < 0.05); n = 4. Different letters within a column with same color value are significantly different (P < 0.05). 1 L* = lightness; a* = redness; b* = yellowness. 2 Vacuum packaged for 7 d then aerobically packaged for 3 d. 3 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 4 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. 5 Cooked by internal temperature (75°C) after 10 d of storage. a–d x–z
Analysis of 2-Thiobarbituric Acid Reactive Substance Values Lipid oxidation was determined by analysis of 2-thiobarbituric acid reactive substances (TBARS) (Ahn et al., 1998). Each meat sample (5 g) was placed in a 50-mL test tube and homogenized with 15 mL of deionized, distilled water using a Brinkman Polytron11 (Type PT 10/35) for 15 s at high speed. The meat homogenate (1 mL) was transferred to a disposable test tube (13 × 100 mm), and butylated hydroxytoluene (7.2%, 50 µL) and thiobarbituric acid-trichloroacetic acid [20 mM thiobarbituric acid and 15% (wt/vol) trichloroacetic acid] solution (2 mL) were added. The mixture was vortexed and then incubated in a 90°C water bath for 15 min to develop color. After cooling for 10 min in cold water, the samples were vortexed and centrifuged at 3,000 × g for 15 min at 5°C. The absorbance of the resulting upper layer was read at 531 nm against a blank prepared with 1 mL deionized, distilled water and 2 mL thiobarbituric acid-trichloroacetic acid solution. The amounts of TBARS were expressed as milligrams of malonedialdehyde per kilogram of meat.
11
Brinkman Instrument, Inc., Westbury, NY. Takmar-Dohrmann, Cincinnati, OH. 13 Hewlett-Packard Co., Wilmington, DE. 14 J & W Scientific, Folsom, CA. 12
Analysis of Volatile Profiles A purge-and-trap apparatus12(Precept II and Purge & Trap Concentrator 3000) connected to a gas chromatograph-mass spectrometer13 was used to analyze volatiles produced (Ahn et al., 2001). Each minced meat sample (3 g) was placed in a 40-mL sample vial, and the vials were flushed with helium gas (40 psi) for 5 s. Samples were held in a refrigerated (4°C) sample-holding tray before analysis, and the maximum holding time was less than 6 h to minimize oxidative changes (Ahn et al., 1999). The meat sample was purged with helium gas (40 mL/min) for 13 min at 40°C. Volatiles were trapped using a Tenax column14 and desorbed for 2 min at 225°C, focused in a cryofocusing module (−90°C), and then thermally desorbed into a column for 30 s at 225°C. An HP-624 column13 (7.5 m × 0.25 mm i.d., 1.4 µm nominal), an HP-1 column13 (52.5 m × 0.25 mm i.d., 0.25 µm nominal), and an HP-Wax column13 (7.5 m × 0.25 mm i.d., 0.25 µm nominal) were connected using zero dead-volume column connectors.14 Ramped oven temperature was used to improve volatile separation. The initial oven temperature of 0°C was held for 2.50 min. After that, the oven temperature was increased to 15°C at 2.5°C/min, increased to 45°C at 5°C/min, increased to 110°C at 20°C/min, increased to 210°C at 10°C/min, and then held for 4.5 min. Constant column pressure at 20.5 psi was maintained. The ionization potential of the mass selective detector13 (Model 5973) was 70 eV, and
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Vacuum packaging
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY
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TABLE 3. 2-Thiobarbituric acid reactive substance values of irradiated turkey breast patties treated by different packaging and antioxidants during 10 d of storage and after cooking Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 None
S+E2
G+E3
SEM
0.42dy 0.53cx 0.54ex 0.02
0.55c 0.53c 0.64e 0.04
0.03 0.09 0.07
4
(mg MDA /kg meat) 0d 10 d Cooked5 SEM
0.66by 0.72cy 1.12dx 0.06
0.84ay 0.84cy 1.67cx 0.04
0.91ay 2.18ax 2.37ax 0.14
0.83ay 1.61by 2.09bx 0.05
Different letters within a row are significantly different (P < 0.05); n = 4. Different letters within a column are significantly different (P < 0.05). 1 Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. 4 Malonedialdehyde. 5 Cooked by internal temperature (75°C) after 10 d of storage. a–e x,y
Statistical Analysis A completely randomized design was used to determine the effects of double packaging and antioxidant combinations on color, lipid oxidation, and volatile profiles of the irradiated samples during storage. Data were analyzed by the general linear models procedure using SAS software (SAS Institute, 1995). Student-NewmanKeul’s multiple-range test was used to compare the mean values of treatments. Mean values and SEM were reported at P < 0.05.
RESULTS AND DISCUSSION Color Changes Irradiated turkey breast had higher a* values than nonirradiated meat (Table 2). Antioxidants lowered the L* value of vacuum-packaged irradiated meat by about 2 U and a* value by 1 U. The a* value of aerobically packaged irradiated meat was lower than that of vacuum-packaged meat but was still higher than the nonirradiated control. Nam and Ahn (2002a) attributed the increased red color in irradiated turkey meat to the formation of carbon monoxide-myoglobin (CO-Mb) complexes. The CO-Mb complex is more stable than oxymyoglobin because of the strong binding of CO to the iron-porphyrin site on the myoglobin molecule (Sorheim et al., 1999). The increased redness of vacuum-packaged turkey breast by irradiation was stable even after 10 d of refrig-
erated storage. However, the redness of aerobically or double-packaged meat decreased significantly. This finding indicated that exposing irradiated meat to aerobic conditions was effective in reducing CO-heme pigment complex formation. Furthermore, the combination of antioxidants with double packaging showed a synergistic effect in reducing the redness of irradiated meat; the presence of oxygen should accelerate the dissociation of CO-Mb, whereas antioxidants should inhibit radiolytic generation of CO. Grant and Patterson (1991) also reported that irradiated color could be discolored in the presence of oxygen. The color changes of irradiated meat after cooking are more of concern, because residual pink color in turkey breast meat can be considered undercooked or contaminated by consumers. The redness of meat was still higher in irradiated meat than in nonirradiated meat even after cooking, and the inside of the meat had stronger redness intensity than the surface. Irradiated cooked turkey breast meat from double packaging and antioxidant combinations, however, produced significantly lower a* values than the vacuum-packaged irradiated cooked meat. Gallate plus α-tocopherol was significantly more effective in reducing the redness than sesamol plus αtocopherol. Therefore, the gallate plus α-tocopherol in combination with double packaging can be effective in controlling off-color in irradiated raw and cooked turkey breast meat.
Lipid Oxidation Both aerobic packaging and irradiation increased the lipid oxidation of turkey breast, but the presence of oxygen was a more critical factor than irradiation on lipid oxidation during storage (Table 3). Vacuum-packaged meat was more resistant to lipid oxidation than aerobically packaged meat, and the TBARS increase was proportional to the exposure time to aerobic conditions. The TBARS of meat was highest with aerobic packaging, lowest with vacuum packaging, and in the middle with
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the scan range was 18.1 to 350 m/z. Identification of volatiles was achieved by comparing mass spectral data of samples with those of the Wiley library.13 Standards, when available, were used to confirm the identification by the mass selective detector. The area of each peak was integrated using the ChemStation,13 and the total peak area (pA × s × 104) was reported as an indicator of volatiles generated from the sample.
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NAM AND AHN
double packaging. Two antioxidant combinations were very effective in preventing lipid oxidation during storage, and the TBARS of antioxidant-treated meats were lower than even nonirradiated vacuum-packaged meat at 10 d. The antioxidant effect on lipid oxidation of turkey meat was even more distinct after cooking. The TBARS of irradiated turkey meat increased rapidly after cooking, but those with antioxidants did not. Therefore, the problem of lipid oxidation in aerobically or doublepackaged irradiated raw and cooked turkey breast could be solved by addition of sesamol + α-tocopherol or gallate + α-tocopherol.
Off-Odor Volatiles of Raw Meat
TABLE 4. Volatile profiles of irradiated raw turkey breast patties treated by different packaging and antioxidants at 0 d Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 S+E2
None
G+E3
SEM
(Total ion counts × 10 ) 4
Hydrocarbons 1-Butene 1-Pentene Pentane 2-Pentene 1-Hexene Hexane Benzene 1-Heptene Heptane Toluene 4-Octene Octane 2-Octene 3-Methyl-2-heptene 2-Octene Sulfurs Dimethyl sulfide Carbon disulfide Dimethyl disulfide Aldehyde and ketone Propanal 2-Propanone Total
0b 0c 431b 0b 0c 97c 0c 0d 0d 0d 246b 418b 169bc 242a 0c
854a 176ab 854a 110a 115a 260b 196ab 124ab 110b 560a 371a 658a 644a 313a 145a
947a 189a 1,105a 96a 99ab 384a 158b 155a 168a 365c 0d 119c 0c 0c 0c
818a 156ab 904a 102a 94ab 212b 226a 127ab 120b 432bc 123c 246bc 397b 82b 70b
859a 123b 352b 0b 75ab 168bc 208ab 90bc 76c 468b 135c 255bc 480b 109b 16c
951a 147ab 426b 33b 47ab 180bc 246a 64c 57c 426bc 135c 251bc 408b 99b 39bc
68 14 70 10 14 26 15 10 9 24 23 43 10 24 11
879b 246ab 0b
1,455a 293a 11,918a
819b 0c 83b
1,405a 276ab 11,466a
1,434a 203b 8,306a
919b 44c 8,557a
78 22 1,473
61b 2,608a 5,401c
286a 2,630a 22,069a
257a 2,465ab 7,415c
298a 1,555c 19,117ab
0b 1,800c 15,162b
0b 2,158b 15,195b
19 105 1,483
Different letters within a row are significantly different (P < 0.05); n = 4. Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. a–d 1
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Irradiation generated many volatiles not found in vacuum-packaged nonirradiated turkey breast meat (Table 4). The majority of newly generated volatiles were hydrocarbons and sulfur-containing compounds, and 1butene, toluene, dimethyl sulfide, and dimethyl disulfide were among the most distinct. S-compounds are regarded as the major volatiles responsible for the characteristic of irradiation off-odor and are different from the rancidity caused by lipid oxidation products. Ahn et al. (2000a) described the irradiation odor in raw pork as a “barbecued corn-like” odor. S-containing volatiles,
such as 2,3-dimethyl disulfide produced by radiolytic degradation of sulfur amino acids, are responsible for the off-odor in irradiated pork, and their amounts are highly dependent upon irradiation dose (Ahn et al., 2000b). Aerobic packaging was more desirable than vacuum or double packaging in reducing the amounts of hydrocarbons and sulfur compounds. Almost all dimethyl disulfide, a main irradiation off-odor, disappeared under aerobic conditions, and aerobically packaged irradiated meat had only one-third the total volatiles of the vacuum-packaged meat. Little difference in volatile profiles between vacuum-packaged irradiated and doubly packaged irradiated meats at 0 d was found because they were both under vacuum conditions during irradiation. Antioxidant treatments lowered total volatiles in meat, and propanal was not detected when antioxidants were added. After 10 d of refrigerated storage, volatile profiles of irradiated turkey breast were highly dependent upon antioxidant and packaging conditions (Table 5). Vacuum-packaged irradiated turkey breast had the greatest amounts of total and sulfur volatiles. The amount of dimethyl disulfide increased twofold compared with that at 0 d (P < 0.01), and dimethyl trisulfide was newly generated in vacuum-packaged irradiated meat. These sulfur volatiles, however, were not detected in irradi-
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY
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TABLE 5. Volatile profiles of irradiated raw turkey breast patties treated by different packaging and antioxidants after 10 d of refrigerated storage Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 None
S+E2
G+E3
SEM
(Total ion counts × 10 ) 4
0c 0c 684bc 40bc 0c 78c 0c 0c 0c 0c 228b 411b 193b 230b
Sulfurs Dimethyl sulfide Carbon disulfide Dimethyl disulfide Dimethyl trisulfide
1,304b 258b 0b 0b
Aldehydes and Ketones Propanal Hexanal 2-Propanone 2-Butanone
0b 0 1,739b 0b
Total
5,172b
930a 195a 1,365ab 174a 112a 374b 309a 92b 110b 537a 490a 862a 451a 445a
111c 113b 2,147a 0c 75b 514a 20c 167a 217a 178b 0d 122c 0c 0d
419b 120b 1,532a 65b 67b 311b 200b 96b 125b 214b 74cd 174c 59c 60cd
366b 140b 354c 0c 69b 294b 152b 79b 82b 172b 96c 203c 59c 76cd
366b 99b 571bc 0c 80b 304b 144b 79b 99b 213b 137c 302bc 85c 116c
52 16 200 14 7 33 22 8 12 24 25 53 17 28
1,990a 306a 22,702a 554a
140d 0c 0b 0b
831c 0c 32b 0b
676c 0c 0b 0b
546c 0c 43b 0b
85 14 739 16
0b 0 2,116ab 0b 34,120a
1,966a 755 2,465a 107a 9,102b
600b 0 2,147ab 0b 7,132b
0b 0 1,962ab 0b 4,785b
0b 0 1,992ab 0b 5,183b
14 308 140 5 1,152
Different letters within a row are significantly different (P < 0.05); n = 4. Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. a–d 1
ated aerobically or double-packaged meat. Three days of exposure to aerobic conditions was enough for the sulfur volatiles to escape from the meat. However, aerobically packaged irradiated meat without antioxidants produced large amounts of aldehydes (propanal, hexanal) and 2-butanone at 10 d, which coincided with the result of TBARS (Table 3). Double-packaged meat had few lipid oxidation products compared with aerobically packaged meat, but antioxidant combinations significantly reduced the amount of pentane. Therefore, the combination of double packaging (vacuum for 3 d then aerobic for 7) with antioxidants in irradiated raw turkey breast was very effective in reducing total and sulfur volatiles responsible for the irradiation off-odor without any problem in lipid oxidation.
Off-Odor Volatiles of Cooked Meat The beneficial effects of double packaging and antioxidant combinations on volatiles were more apparent in irradiated cooked turkey breast (Table 6). Irradiated cooked turkey breast not only produced considerable amounts of sulfur volatiles but also aldehydes and ketones. Therefore, irradiated cooked meat had a characteristic irradiation off-odor and lipid oxidation-related
volatiles compared with the nonirradiated cooked meat. Cooking of vacuum-packaged irradiated meat produced high amounts of sulfur volatiles, whereas cooking of aerobically packaged irradiated meat produced large amounts of aldehydes. Large amounts of propanal and hexanal were formed in irradiated cooked turkey breast, and the amount of total volatiles was greatest in aerobically packaged irradiated cooked meat. This result shows that both lipid oxidation products and irradiation off-odor were problematic when storing irradiated meat under aerobic conditions. Double packaging was more effective than vacuum packaging in reducing sulfur volatiles and lipid oxidation-dependent volatiles compared with aerobic packaging. However, the combination of antioxidant with double packaging was more effective in reducing sulfur and lipid oxidation volatiles in irradiated cooked meat. The total amounts of sulfur volatiles in double-packaged irradiated turkey meat with antioxidants were only about 5 to 7% of the irradiated vacuum-packaged cooked meat without antioxidants. Production of most aldehydes in irradiated cooked turkey breast was prevented by using antioxidants and double packaging. In conclusion, the combination of double packaging and antioxidants was highly effective in controlling lipid
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Hydrocarbons 1-Butene 1-Pentene Pentane 2-Pentene 1-Hexene Hexane Benzene 1-Heptene Heptane Toluene 4-Octene Octane 2-Octene 3-Methyl-2-heptene
856
NAM AND AHN TABLE 6. Volatile profiles of irradiated, cooked (internal temperature, 75°C) turkey breast patties treated by different packaging and antioxidants Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 None
S+E2
G+E3
SEM
(Total ion counts × 10 ) 4
74c 0d 1,738c 77d 0c 191d 0c 0b 94c 0c 253b 380d 137c 267a 0b 0b
1,441a 366ab 6,527c 289c 199ab 904c 313a 414a 467c 2,199a 510a 1,219bc 612a 409a 0b 0b
1,595a 380ab 30,267a 721a 274a 5,192a 177b 680a 3,602a 822b 129b 2,214a 653a 0b 63a 166a
1,502a 436a 21,607b 606b 204ab 2,540b 316a 558a 1,799b 2,226a 294b 1,677b 606a 301ab 0b 0b
575b 174c 1,332c 82d 156b 803c 192b 412a 321c 2,403a 313b 800cd 313b 227ab 0b 0b
577b 240bc 2,443c 128d 191ab 931c 224ab 453a 485c 1,689a 251b 801cd 323b 170ab 0b 0b
95 43 2,051 28 22 165 29 75 133 216 56 164 50 61 1 11
Sulfurs Dimethyl sulfide Carbon disulfide Dimethyl disulfide Dimethyl trisulfide
1,008b 419a 0b 0b
2,032a 339ab 17,861a 1,007a
451d 210b 342b 0b
1,005b 271ab 940b 118b
689c 278ab 412b 0b
588cd 374a 210b 0b
48 35 601 49
Aldehydes and Ketones Propanal Butanal Pentanal Hexanal 2-Propanone 2-Butanone 3-Methyl butanal
233d 0e 62c 0b 1,770d 0c 0c
Total
6,706c
2,272c 127d 875c 3,734b 2,828bc 116b 100b 47,171b
8,637a 592a 3,014a 37,617a 3,744a 0c 223a 101,773a
5,962b 195c 1,667b 9,686b 33,84ab 231a 204a 58,251b
38d 302b 0c 0b 2,863bc 223a 131b 13,046c
427d 226c 31c 0b 2,637c 142b 142b 13,691c
377 22 223 2,626 167 10 12 4,889
Different letters within a row are significantly different (P < 0.05); n = 4. Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. a–e 1
oxidation and irradiation off-odor of irradiated raw and cooked turkey breast patties.
REFERENCES Ahn, D. U., C. Jo, and D. G. Olson. 1999. Volatile profiles of raw and cooked turkey thigh as affected by purge temperature and holding time before purge. J. Food Sci. 64:230–233. Ahn, D. U., C. Jo, and D. G. Olson. 2000a. Analysis of volatile components and the sensory characteristics of irradiated raw pork. Meat Sci. 54:209–215. Ahn, D. U., C. Jo, M. Du, D. G. Olson, and K. C. Nam. 2000b. Quality characteristics of pork patties irradiated and stored in different packaging and storage conditions. Meat Sci. 56:203–209. Ahn, D. U., K. C. Nam, M. Du, and C. Jo. 2001. Volatile production in irradiated normal, pale soft exudative (PSE) and dark firm dry (DFD) pork under different packaging and storage conditions. Meat Sci. 57:419–426. Ahn, D. U., D. G. Olson, C. Jo, X. Chen, C. Wu, and J. I. Lee. 1998. Effect of muscle type, packaging, and irradiation on lipid oxidation, volatile production, and color in raw pork patties. Meat Sci. 47:27–39. Ahn, D. U., J. L. Sell, M. Jeffery, C. Jo, X. Chen, C. Wu, and J. I. Lee. 1997. Dietary vitamin E affects lipid oxidation and
total volatiles of irradiated raw turkey meat. J. Food Sci. 62:954–958. Du, M., D. U. Ahn, K. C. Nam, and J. L. Sell. 2000. Influence of dietary conjugated linolenic acid on volatile profiles, color and lipid oxidation of irradiated raw chicken meat. Meat Sci. 56:387–395. Grant, I. R., and M. F. Patterson. 1991. Effect of irradiation and modified atmosphere packaging on the microbiological and sensory quality of pork stored at refrigeration temperatures. Int. J. Food Sci. Technol. 26:507–519. Jo, C., and D. U. Ahn. 2000. Production of volatile compounds from irradiated oil emulsions containing amino acids or proteins. J. Food Sci. 65:612–616. Katusin-Razem, B., K. W. Mihaljevic, and D. Razem. 1992. Timedependent post irradiation oxidative chemical changes in dehydrated egg products. J. Agric. Food Chem. 40:1948–1952. Lambert, A. D., J. P. Smith, and K. L. Dodds. 1991. Shelf life extension and microbiological safety of fresh meat: A review. Food Microbiol. 8:267–297. Luchsinger, S. E., D. H. Kropf, C. M. Garcia-Zepeda, M. C. Hunt, J. L. Marsden, E. J. Rubio-Canas, C. L. Kastner, W. G. Kuecher, and T. Mata. 1996. Color and oxidative rancidity of gamma and electron beam-irradiated boneless pork chops. J. Food Sci. 61:1000–1005. Lynch, J. A., H. J. H. MacFie, and G. C. Mead. 1991. Effect of irradiation and packaging type on sensory quality of chilled-
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Hydrocarbons and furan 1-Butene 1-Pentene Pentane 2-Pentene 1-Hexene Hexane Benzene 1-Heptene Heptane Toluene 4-Octene Octane 2-Octene 3-Methyl-2-heptene Nonane 2-Ethyl furan
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY stored turkey breast fillets. Int. J. Food Sci. Technol. 26:653–668. Nam, K. C., and D. U. Ahn. 2002a. Carbon monoxide-heme pigment is responsible for the pink color in irradiated raw turkey breast meat. Meat Sci. 60:25–33. Nam, K. C., and D. U. Ahn. 2002b. Use of antioxidants to reduce lipid oxidation and off-odor volatiles of irradiated pork homogenates and patties. Meat Sci. 63:1–8. Nam, K. C., D. U. Ahn, M. Du, and C. Jo. 2001. Lipid oxidation, color, volatiles, and sensory characteristics of aerobically packaged and irradiated pork with different ultimate pH. J. Food Sci. 66:1225–1229. Nanke, K. E., J. G. Sebranek, and D. G. Olson. 1998. Color characteristics of irradiated vacuum-packaged pork, beef, and turkey. J. Food Sci. 63:1001–1006.
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Patterson, R. L., and M. H. Stevenson. 1995. Irradiation-induced off-odor in chicken and its possible control. Br. Poult. Sci. 36:425–441. SAS Institute. 1995. SAS/STAT User’s Guide. SAS Institute Inc., Cary, NC. Sorheim, O., H. Nessen, and T. Nesbakken. 1999. The storage life of beef and pork packaged in an atmosphere with low carbon monoxide and high carbon dioxide. Meat Sci. 52:157–164. Woods, R. J., and A. K. Pikaev. 1994. Interaction of radiation with matter. Pages 59–89 in Applied Radiation Chemistry: Radiation Processing. R. J. Woods and A. K. Pikaev, ed. J. Wiley, New York.
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(Key words: antioxidant, double packaging, irradiated turkey, lipid oxidation, volatiles) 2003 Poultry Science 82:850–857
secondary reactions of free radicals generated by irradiation with meat components are believed to be the main cause of these quality changes. Woods and Pikaev (1994) and Ahn et al. (1997) reported that antioxidants reduce oxidative quality deterioration of irradiated meat by quenching free radicals. Nam and Ahn (2002b) showed that gallate or sesamol combined with α-tocopherol decreases production of sulfur volatiles as well as lipid oxidation in irradiated pork patties. Packaging is also a critical factor influencing the quality of irradiated meat. Under vacuum conditions, almost all sulfur volatiles generated by irradiation are retained in meat (Ahn et al., 2000b; Ahn et al., 2001; Nam et al., 2001), and the intensity of pink color in irradiated meat increases during storage (Luchsinger et al., 1996; Nam and Ahn, 2002a). Under aerobic conditions, almost all sulfur volatiles generated by irradiation disappear, and pink color intensity decreases after a few days of storage. Lipid oxidation in irradiated meat during storage was
INTRODUCTION Although irradiating is the best method to ensure the microbiological safety of raw meat (Lambert et al., 1991), it caused a few radiolytic meat quality defects. Irradiated pork and poultry meat accelerate lipid oxidation (Katusin-Razem et al., 1992; Ahn et al., 2000a), produce a characteristic off-odor (Patterson and Stevenson 1995; Du et al., 2000; Ahn et al., 2001), and develop a pink color (Lynch et al., 1991; Nanke et al., 1998; Nam and Ahn, 2002a). Jo and Ahn (2000) elucidated that sulfur volatiles produced by radiolytic degradation of sulfur amino acids are responsible for the irradiation off-odor, and Nam and Ahn (2002a) characterized the pink color in irradiated turkey breast as the complex of heme pigment and radiolytic carbon monoxide. The primary and
2003 Poultry Science Association, Inc. Received for publication February 13, 2002. Accepted for publication December 18, 2002. 1 Journal Paper No. J-19735 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project No. 3706, and supported by NRI. 2 To whom correspondence should be addressed: [email protected].
Abbreviation Key: a* = redness; b* = yellowness; CO-Mb = carbon monoxide-myoglobin; L* = lightness; TBARS, 2-thiobarbituric acid reactive substances.
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ABSTRACT The effects of antioxidants and double packaging combinations on color, lipid oxidation, and volatiles production in irradiated raw and cooked turkey breast were determined. Ground meat was treated with antioxidants (none, sesamol + α-tocopherol, or gallate + αtocopherol), and patties were prepared. The patties were packaged under vacuum, packaged aerobically, or double packaged (vacuum for 7 d then aerobic for 3 d) and electron beam irradiated at 3 kGy. Color, 2-thiobarbituric acid-reactive substances (TBARS), and volatile profiles of the samples were determined at 0 and 10 d and after cooking. Irradiated vacuum-packaged patties had great amounts of sulfur volatiles (dimethyl sulfide and dimethyl disulfide) and increased red color during refrigerated storage and after cooking compared with the nonir-
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY
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TABLE 1. Packaging, irradiation, and antioxidant treatments used in this study Treatment
Irradiation (kGy)
Antioxidant (100 ppm each)
Packaging method
0 3 3 3 3 3
Not added Not added Not added Not added Sesamol, α-tocopherol Gallate, α-tocopherol
Vacuum for 10 d Vacuum for 10 d Aerobic for 10 d Vacuum for 7 d then aerobic for 3 d Vacuum for 7 d then aerobic for 3 d Vacuum for 7 d then aerobic for 3 d
Nonirradiated-vacuum packaged Irradiated-vacuum packaged Irradiated-aerobic packaged Irradiated-double packaged Irradiated-double packaged/S+E1 Irradiated-double packaged/G+E2 1
Sesamol (100 ppm) and α-tocopherol (100 ppm) added. Gallic acid (100 ppm) and α-tocopherol (100 ppm) added.
2
MATERIALS AND METHODS Treatments A total of 36 male Large White turkeys (16 wk old) were slaughtered, and then carcasses were chilled in ice water for 3 h and drained in a cold room. Breast muscles were deboned from the carcasses 24 h after slaughter. Skin and visible fat were removed. Breast meats from six birds were pooled from and used as a replication. Meats for each replication were ground through a 3-mm plate, and four replications were prepared. Six different treatments were prepared using antioxidant, packaging method, and irradiation conditions (Table 1). Vitamin E + sesamol and vitamin E + gallate combinations were used in this study, because these antioxidant combinations were most effective in reducing lipid oxidation and off-odor volatiles in irradiated turkey meat (Nam and Ahn, 2002b). Sesamol3 (3,4-methylenedioxyphenol) plus α-tocopherol4 or gallate3 (3,4,5-trihydroxybenzoic acid) plus α-tocopherol was mixed with the ground turkey meat each at 100 ppm (final 200 ppm) using a bowl mixer5 (Model KSM 90). The mixed meat samples were ground again through a 3-mm plate to ensure uniform
3
Sigma Chemical Co., St. Louis, MO. Aldrich Chemical Co., Milwaukee, WI. 5 Kitchen Aid, Inc., St. Joseph, MI. 6 Koch, Kansas City, MO. 7 Associated Bag Company, Milwaukee, WI. 8 Thomson CSF Linac, Saint-Aubin, France. 9 Bruker Instruments Inc., Billerica, MA. 10 Hunter Associated Labs, Inc., Reston, VA. 4
distribution of the added antioxidants. Other treatments without antioxidants were also put through the same mixing process to provide the same preparation conditions as antioxidant-added treatments. About 50 g of turkey breast patties was prepared from each treatment and then individually vacuum packaged in high oxygen-barrier bags6 (nylon-polyethylene, 9.3 mL O2/m2 per 24 h at 0°C), aerobically packaged in polyethylene oxygen-permeable bags7 (polyethylene, 2 mil), or double packaged. For double packaging, aerobically packaged patties were repackaged in oxygen-impermeable vacuum bags. The packaged patties were irradiated at 2.5 kGy using a linear accelerator8 (Circe IIIR) with 10 MeV of energy, 10 kW of power, and 86.2 kGy/min of average dose rate. To confirm the target dose, two alanine dosimeters per cart were attached to the top and bottom surfaces of the sample and were read using a 104 Electron Paramagnetic Resonance instrument9 (EMS-104). Nonirradiated vacuum-packaged patties were prepared as a control. The outer vacuum bags of double-packaged meat were removed after 7 d of storage at 4°C to expose the samples under aerobic conditions. Color, lipid oxidation, and volatile compounds of the irradiated raw meats were determined at 0 and 10 d of refrigerated storage. Part of the raw meat stored for 10 d was cooked in a 90°C water bath (cooked in bag) to an internal temperature of 75°C. The surface and internal colors, lipid oxidation, and volatiles of the cooked meat were determined after cooling the meat to room temperature.
Color Measurement The CIE color values were measured on the surface of sample using a LabScan color meter10 that had been calibrated against black and white reference tiles covered with the same packaging materials as used for the samples. The CIE lightness (L*), redness (a*), and yellowness (b*) values were obtained using an illuminant A (light source) with an area view of 0.25 inch and a port size of 0.40 inch. Two random locations of both top and bottom surfaces of the samples were measured. For the internal color of cooked meat, the patties were horizontally dissected, and the internal central locations were measured.
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accelerated only under aerobic conditions (Katusin-Razem et al., 1992; Ahn et al., 2000b). Therefore, exposing irradiated meat to aerobic conditions for a limited period of time could lower irradiation off-odor odor and decrease pink color intensity, and subsequent storage under vacuum could minimize lipid oxidation. Addition of antioxidants thus can prevent quality deterioration of irradiated double-packaged meat during storage. The objective of this study was to determine the effects of double packaging and antioxidant combinations on color, lipid oxidation, and volatiles of irradiated raw turkey breast during refrigerated storage and after cooking.
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NAM AND AHN TABLE 2. CIE color values of irradiated turkey breast patties treated by different packaging and antioxidants during the 10 d of storage and after cooking Nonirradiated
Irradiated Double packaging2
Vacuum packaging
Aerobic packaging
None
S+E3
G+E4
SEM
L* value 0d 10 d Cooked5 (surface) Cooked (inside) SEM
54.29abz 54.44bz 84.38ax 82.05y 0.52
55.36az 56.88ay 84.73ax 84.30x 0.38
55.39ay 56.71ay 83.65ax 82.65x 0.55
55.20ay 56.14ay 84.41ax 83.73x 0.35
53.57bz 54.03bz 84.71ax 82.39y 0.32
53.59by 53.44by 81.70bx 81.98x 0.71
0.29 0.37 0.31 0.81
a* value 0d 10 d Cooked5 (surface) Cooked (inside) SEM
4.42cz 4.67dz 5.96by 7.50cx 0.16
7.95ay 7.89ay 7.53ay 10.04ax 0.24
7.15bx 5.66cy 3.99cz 5.58dy 0.14
6.95by 4.68dz 5.55bz 7.51cx 0.18
6.74bx 5.63cy 4.51cz 5.75dy 0.18
0.13 0.11 0.21 0.23
b* value 0d 10 d Cooked5 (surface) Cooked (inside) SEM
9.63aby 9.18dy 14.87abx 14.99abx 0.43
9.79az 9.55cdz 16.60ax 15.25aby 0.26
9.62abz 12.08ay 14.06bx 15.96ax 0.24
8.58cz 11.29by 15.70abx 15.22abx 0.33
8.59cz 9.86cy 14.29bx 14.44bx 0.38
0.15 0.18 0.50 0.33
Storage1
7.74axy 6.98by 6.20bz 8.62bx 0.13 9.14bz 11.37by 16.67ax 15.95ax 0.25
Different letters within a row are significantly different (P < 0.05); n = 4. Different letters within a column with same color value are significantly different (P < 0.05). 1 L* = lightness; a* = redness; b* = yellowness. 2 Vacuum packaged for 7 d then aerobically packaged for 3 d. 3 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 4 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. 5 Cooked by internal temperature (75°C) after 10 d of storage. a–d x–z
Analysis of 2-Thiobarbituric Acid Reactive Substance Values Lipid oxidation was determined by analysis of 2-thiobarbituric acid reactive substances (TBARS) (Ahn et al., 1998). Each meat sample (5 g) was placed in a 50-mL test tube and homogenized with 15 mL of deionized, distilled water using a Brinkman Polytron11 (Type PT 10/35) for 15 s at high speed. The meat homogenate (1 mL) was transferred to a disposable test tube (13 × 100 mm), and butylated hydroxytoluene (7.2%, 50 µL) and thiobarbituric acid-trichloroacetic acid [20 mM thiobarbituric acid and 15% (wt/vol) trichloroacetic acid] solution (2 mL) were added. The mixture was vortexed and then incubated in a 90°C water bath for 15 min to develop color. After cooling for 10 min in cold water, the samples were vortexed and centrifuged at 3,000 × g for 15 min at 5°C. The absorbance of the resulting upper layer was read at 531 nm against a blank prepared with 1 mL deionized, distilled water and 2 mL thiobarbituric acid-trichloroacetic acid solution. The amounts of TBARS were expressed as milligrams of malonedialdehyde per kilogram of meat.
11
Brinkman Instrument, Inc., Westbury, NY. Takmar-Dohrmann, Cincinnati, OH. 13 Hewlett-Packard Co., Wilmington, DE. 14 J & W Scientific, Folsom, CA. 12
Analysis of Volatile Profiles A purge-and-trap apparatus12(Precept II and Purge & Trap Concentrator 3000) connected to a gas chromatograph-mass spectrometer13 was used to analyze volatiles produced (Ahn et al., 2001). Each minced meat sample (3 g) was placed in a 40-mL sample vial, and the vials were flushed with helium gas (40 psi) for 5 s. Samples were held in a refrigerated (4°C) sample-holding tray before analysis, and the maximum holding time was less than 6 h to minimize oxidative changes (Ahn et al., 1999). The meat sample was purged with helium gas (40 mL/min) for 13 min at 40°C. Volatiles were trapped using a Tenax column14 and desorbed for 2 min at 225°C, focused in a cryofocusing module (−90°C), and then thermally desorbed into a column for 30 s at 225°C. An HP-624 column13 (7.5 m × 0.25 mm i.d., 1.4 µm nominal), an HP-1 column13 (52.5 m × 0.25 mm i.d., 0.25 µm nominal), and an HP-Wax column13 (7.5 m × 0.25 mm i.d., 0.25 µm nominal) were connected using zero dead-volume column connectors.14 Ramped oven temperature was used to improve volatile separation. The initial oven temperature of 0°C was held for 2.50 min. After that, the oven temperature was increased to 15°C at 2.5°C/min, increased to 45°C at 5°C/min, increased to 110°C at 20°C/min, increased to 210°C at 10°C/min, and then held for 4.5 min. Constant column pressure at 20.5 psi was maintained. The ionization potential of the mass selective detector13 (Model 5973) was 70 eV, and
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Vacuum packaging
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY
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TABLE 3. 2-Thiobarbituric acid reactive substance values of irradiated turkey breast patties treated by different packaging and antioxidants during 10 d of storage and after cooking Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 None
S+E2
G+E3
SEM
0.42dy 0.53cx 0.54ex 0.02
0.55c 0.53c 0.64e 0.04
0.03 0.09 0.07
4
(mg MDA /kg meat) 0d 10 d Cooked5 SEM
0.66by 0.72cy 1.12dx 0.06
0.84ay 0.84cy 1.67cx 0.04
0.91ay 2.18ax 2.37ax 0.14
0.83ay 1.61by 2.09bx 0.05
Different letters within a row are significantly different (P < 0.05); n = 4. Different letters within a column are significantly different (P < 0.05). 1 Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. 4 Malonedialdehyde. 5 Cooked by internal temperature (75°C) after 10 d of storage. a–e x,y
Statistical Analysis A completely randomized design was used to determine the effects of double packaging and antioxidant combinations on color, lipid oxidation, and volatile profiles of the irradiated samples during storage. Data were analyzed by the general linear models procedure using SAS software (SAS Institute, 1995). Student-NewmanKeul’s multiple-range test was used to compare the mean values of treatments. Mean values and SEM were reported at P < 0.05.
RESULTS AND DISCUSSION Color Changes Irradiated turkey breast had higher a* values than nonirradiated meat (Table 2). Antioxidants lowered the L* value of vacuum-packaged irradiated meat by about 2 U and a* value by 1 U. The a* value of aerobically packaged irradiated meat was lower than that of vacuum-packaged meat but was still higher than the nonirradiated control. Nam and Ahn (2002a) attributed the increased red color in irradiated turkey meat to the formation of carbon monoxide-myoglobin (CO-Mb) complexes. The CO-Mb complex is more stable than oxymyoglobin because of the strong binding of CO to the iron-porphyrin site on the myoglobin molecule (Sorheim et al., 1999). The increased redness of vacuum-packaged turkey breast by irradiation was stable even after 10 d of refrig-
erated storage. However, the redness of aerobically or double-packaged meat decreased significantly. This finding indicated that exposing irradiated meat to aerobic conditions was effective in reducing CO-heme pigment complex formation. Furthermore, the combination of antioxidants with double packaging showed a synergistic effect in reducing the redness of irradiated meat; the presence of oxygen should accelerate the dissociation of CO-Mb, whereas antioxidants should inhibit radiolytic generation of CO. Grant and Patterson (1991) also reported that irradiated color could be discolored in the presence of oxygen. The color changes of irradiated meat after cooking are more of concern, because residual pink color in turkey breast meat can be considered undercooked or contaminated by consumers. The redness of meat was still higher in irradiated meat than in nonirradiated meat even after cooking, and the inside of the meat had stronger redness intensity than the surface. Irradiated cooked turkey breast meat from double packaging and antioxidant combinations, however, produced significantly lower a* values than the vacuum-packaged irradiated cooked meat. Gallate plus α-tocopherol was significantly more effective in reducing the redness than sesamol plus αtocopherol. Therefore, the gallate plus α-tocopherol in combination with double packaging can be effective in controlling off-color in irradiated raw and cooked turkey breast meat.
Lipid Oxidation Both aerobic packaging and irradiation increased the lipid oxidation of turkey breast, but the presence of oxygen was a more critical factor than irradiation on lipid oxidation during storage (Table 3). Vacuum-packaged meat was more resistant to lipid oxidation than aerobically packaged meat, and the TBARS increase was proportional to the exposure time to aerobic conditions. The TBARS of meat was highest with aerobic packaging, lowest with vacuum packaging, and in the middle with
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the scan range was 18.1 to 350 m/z. Identification of volatiles was achieved by comparing mass spectral data of samples with those of the Wiley library.13 Standards, when available, were used to confirm the identification by the mass selective detector. The area of each peak was integrated using the ChemStation,13 and the total peak area (pA × s × 104) was reported as an indicator of volatiles generated from the sample.
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NAM AND AHN
double packaging. Two antioxidant combinations were very effective in preventing lipid oxidation during storage, and the TBARS of antioxidant-treated meats were lower than even nonirradiated vacuum-packaged meat at 10 d. The antioxidant effect on lipid oxidation of turkey meat was even more distinct after cooking. The TBARS of irradiated turkey meat increased rapidly after cooking, but those with antioxidants did not. Therefore, the problem of lipid oxidation in aerobically or doublepackaged irradiated raw and cooked turkey breast could be solved by addition of sesamol + α-tocopherol or gallate + α-tocopherol.
Off-Odor Volatiles of Raw Meat
TABLE 4. Volatile profiles of irradiated raw turkey breast patties treated by different packaging and antioxidants at 0 d Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 S+E2
None
G+E3
SEM
(Total ion counts × 10 ) 4
Hydrocarbons 1-Butene 1-Pentene Pentane 2-Pentene 1-Hexene Hexane Benzene 1-Heptene Heptane Toluene 4-Octene Octane 2-Octene 3-Methyl-2-heptene 2-Octene Sulfurs Dimethyl sulfide Carbon disulfide Dimethyl disulfide Aldehyde and ketone Propanal 2-Propanone Total
0b 0c 431b 0b 0c 97c 0c 0d 0d 0d 246b 418b 169bc 242a 0c
854a 176ab 854a 110a 115a 260b 196ab 124ab 110b 560a 371a 658a 644a 313a 145a
947a 189a 1,105a 96a 99ab 384a 158b 155a 168a 365c 0d 119c 0c 0c 0c
818a 156ab 904a 102a 94ab 212b 226a 127ab 120b 432bc 123c 246bc 397b 82b 70b
859a 123b 352b 0b 75ab 168bc 208ab 90bc 76c 468b 135c 255bc 480b 109b 16c
951a 147ab 426b 33b 47ab 180bc 246a 64c 57c 426bc 135c 251bc 408b 99b 39bc
68 14 70 10 14 26 15 10 9 24 23 43 10 24 11
879b 246ab 0b
1,455a 293a 11,918a
819b 0c 83b
1,405a 276ab 11,466a
1,434a 203b 8,306a
919b 44c 8,557a
78 22 1,473
61b 2,608a 5,401c
286a 2,630a 22,069a
257a 2,465ab 7,415c
298a 1,555c 19,117ab
0b 1,800c 15,162b
0b 2,158b 15,195b
19 105 1,483
Different letters within a row are significantly different (P < 0.05); n = 4. Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. a–d 1
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Irradiation generated many volatiles not found in vacuum-packaged nonirradiated turkey breast meat (Table 4). The majority of newly generated volatiles were hydrocarbons and sulfur-containing compounds, and 1butene, toluene, dimethyl sulfide, and dimethyl disulfide were among the most distinct. S-compounds are regarded as the major volatiles responsible for the characteristic of irradiation off-odor and are different from the rancidity caused by lipid oxidation products. Ahn et al. (2000a) described the irradiation odor in raw pork as a “barbecued corn-like” odor. S-containing volatiles,
such as 2,3-dimethyl disulfide produced by radiolytic degradation of sulfur amino acids, are responsible for the off-odor in irradiated pork, and their amounts are highly dependent upon irradiation dose (Ahn et al., 2000b). Aerobic packaging was more desirable than vacuum or double packaging in reducing the amounts of hydrocarbons and sulfur compounds. Almost all dimethyl disulfide, a main irradiation off-odor, disappeared under aerobic conditions, and aerobically packaged irradiated meat had only one-third the total volatiles of the vacuum-packaged meat. Little difference in volatile profiles between vacuum-packaged irradiated and doubly packaged irradiated meats at 0 d was found because they were both under vacuum conditions during irradiation. Antioxidant treatments lowered total volatiles in meat, and propanal was not detected when antioxidants were added. After 10 d of refrigerated storage, volatile profiles of irradiated turkey breast were highly dependent upon antioxidant and packaging conditions (Table 5). Vacuum-packaged irradiated turkey breast had the greatest amounts of total and sulfur volatiles. The amount of dimethyl disulfide increased twofold compared with that at 0 d (P < 0.01), and dimethyl trisulfide was newly generated in vacuum-packaged irradiated meat. These sulfur volatiles, however, were not detected in irradi-
ANTIOXIDANT AND DOUBLE PACKAGING ON IRRADIATED TURKEY MEAT QUALITY
855
TABLE 5. Volatile profiles of irradiated raw turkey breast patties treated by different packaging and antioxidants after 10 d of refrigerated storage Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 None
S+E2
G+E3
SEM
(Total ion counts × 10 ) 4
0c 0c 684bc 40bc 0c 78c 0c 0c 0c 0c 228b 411b 193b 230b
Sulfurs Dimethyl sulfide Carbon disulfide Dimethyl disulfide Dimethyl trisulfide
1,304b 258b 0b 0b
Aldehydes and Ketones Propanal Hexanal 2-Propanone 2-Butanone
0b 0 1,739b 0b
Total
5,172b
930a 195a 1,365ab 174a 112a 374b 309a 92b 110b 537a 490a 862a 451a 445a
111c 113b 2,147a 0c 75b 514a 20c 167a 217a 178b 0d 122c 0c 0d
419b 120b 1,532a 65b 67b 311b 200b 96b 125b 214b 74cd 174c 59c 60cd
366b 140b 354c 0c 69b 294b 152b 79b 82b 172b 96c 203c 59c 76cd
366b 99b 571bc 0c 80b 304b 144b 79b 99b 213b 137c 302bc 85c 116c
52 16 200 14 7 33 22 8 12 24 25 53 17 28
1,990a 306a 22,702a 554a
140d 0c 0b 0b
831c 0c 32b 0b
676c 0c 0b 0b
546c 0c 43b 0b
85 14 739 16
0b 0 2,116ab 0b 34,120a
1,966a 755 2,465a 107a 9,102b
600b 0 2,147ab 0b 7,132b
0b 0 1,962ab 0b 4,785b
0b 0 1,992ab 0b 5,183b
14 308 140 5 1,152
Different letters within a row are significantly different (P < 0.05); n = 4. Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. a–d 1
ated aerobically or double-packaged meat. Three days of exposure to aerobic conditions was enough for the sulfur volatiles to escape from the meat. However, aerobically packaged irradiated meat without antioxidants produced large amounts of aldehydes (propanal, hexanal) and 2-butanone at 10 d, which coincided with the result of TBARS (Table 3). Double-packaged meat had few lipid oxidation products compared with aerobically packaged meat, but antioxidant combinations significantly reduced the amount of pentane. Therefore, the combination of double packaging (vacuum for 3 d then aerobic for 7) with antioxidants in irradiated raw turkey breast was very effective in reducing total and sulfur volatiles responsible for the irradiation off-odor without any problem in lipid oxidation.
Off-Odor Volatiles of Cooked Meat The beneficial effects of double packaging and antioxidant combinations on volatiles were more apparent in irradiated cooked turkey breast (Table 6). Irradiated cooked turkey breast not only produced considerable amounts of sulfur volatiles but also aldehydes and ketones. Therefore, irradiated cooked meat had a characteristic irradiation off-odor and lipid oxidation-related
volatiles compared with the nonirradiated cooked meat. Cooking of vacuum-packaged irradiated meat produced high amounts of sulfur volatiles, whereas cooking of aerobically packaged irradiated meat produced large amounts of aldehydes. Large amounts of propanal and hexanal were formed in irradiated cooked turkey breast, and the amount of total volatiles was greatest in aerobically packaged irradiated cooked meat. This result shows that both lipid oxidation products and irradiation off-odor were problematic when storing irradiated meat under aerobic conditions. Double packaging was more effective than vacuum packaging in reducing sulfur volatiles and lipid oxidation-dependent volatiles compared with aerobic packaging. However, the combination of antioxidant with double packaging was more effective in reducing sulfur and lipid oxidation volatiles in irradiated cooked meat. The total amounts of sulfur volatiles in double-packaged irradiated turkey meat with antioxidants were only about 5 to 7% of the irradiated vacuum-packaged cooked meat without antioxidants. Production of most aldehydes in irradiated cooked turkey breast was prevented by using antioxidants and double packaging. In conclusion, the combination of double packaging and antioxidants was highly effective in controlling lipid
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Hydrocarbons 1-Butene 1-Pentene Pentane 2-Pentene 1-Hexene Hexane Benzene 1-Heptene Heptane Toluene 4-Octene Octane 2-Octene 3-Methyl-2-heptene
856
NAM AND AHN TABLE 6. Volatile profiles of irradiated, cooked (internal temperature, 75°C) turkey breast patties treated by different packaging and antioxidants Nonirradiated
Storage
Vacuum packaging
Irradiated Vacuum packaging
Aerobic packaging
Double packaging1 None
S+E2
G+E3
SEM
(Total ion counts × 10 ) 4
74c 0d 1,738c 77d 0c 191d 0c 0b 94c 0c 253b 380d 137c 267a 0b 0b
1,441a 366ab 6,527c 289c 199ab 904c 313a 414a 467c 2,199a 510a 1,219bc 612a 409a 0b 0b
1,595a 380ab 30,267a 721a 274a 5,192a 177b 680a 3,602a 822b 129b 2,214a 653a 0b 63a 166a
1,502a 436a 21,607b 606b 204ab 2,540b 316a 558a 1,799b 2,226a 294b 1,677b 606a 301ab 0b 0b
575b 174c 1,332c 82d 156b 803c 192b 412a 321c 2,403a 313b 800cd 313b 227ab 0b 0b
577b 240bc 2,443c 128d 191ab 931c 224ab 453a 485c 1,689a 251b 801cd 323b 170ab 0b 0b
95 43 2,051 28 22 165 29 75 133 216 56 164 50 61 1 11
Sulfurs Dimethyl sulfide Carbon disulfide Dimethyl disulfide Dimethyl trisulfide
1,008b 419a 0b 0b
2,032a 339ab 17,861a 1,007a
451d 210b 342b 0b
1,005b 271ab 940b 118b
689c 278ab 412b 0b
588cd 374a 210b 0b
48 35 601 49
Aldehydes and Ketones Propanal Butanal Pentanal Hexanal 2-Propanone 2-Butanone 3-Methyl butanal
233d 0e 62c 0b 1,770d 0c 0c
Total
6,706c
2,272c 127d 875c 3,734b 2,828bc 116b 100b 47,171b
8,637a 592a 3,014a 37,617a 3,744a 0c 223a 101,773a
5,962b 195c 1,667b 9,686b 33,84ab 231a 204a 58,251b
38d 302b 0c 0b 2,863bc 223a 131b 13,046c
427d 226c 31c 0b 2,637c 142b 142b 13,691c
377 22 223 2,626 167 10 12 4,889
Different letters within a row are significantly different (P < 0.05); n = 4. Vacuum packaged for 7 d then aerobically packaged for 3 d. 2 Sesamol (100 ppm) and α-tocopherol (100 ppm) added. 3 Gallic acid (100 ppm) and α-tocopherol (100 ppm) added. a–e 1
oxidation and irradiation off-odor of irradiated raw and cooked turkey breast patties.
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