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Keywords:

  • antioxidants;
  • application methods;
  • ground beef;
  • irradiation;
  • quality parameters

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. References

ABSTRACT:  Four antioxidant treatments (none, 0.05% ascorbic acid, 0.01%α-tocopherol + 0.01% sesamol, and 0.05% ascorbic acid + 0.01%α-tocopherol + 0.01% sesamol) were applied to ground beef using either mixing or spraying method. The meat samples were placed on Styrofoam trays, irradiated at 0 or 2.5 kGy, and then stored for 7 d at 4 °C. Color, lipid oxidation, volatiles, oxidation-reduction potential (ORP), and carbon monoxide (CO) production were determined at 0, 3, and 7 d of storage. Irradiation increased lipid oxidation of ground beef with control and ascorbic acid treatments after 3 d of storage. α-Tocopherol + sesamol and ascorbic acid +α-tocopherol + sesamol treatments were effective in slowing down lipid oxidation in ground beef during storage regardless of application methods, but mixing was better than the spraying method. Irradiation lowered L*-value and a*-value of ground beef. Storage had no effect on lightness but redness decreased with storage. Ascorbic acid was the most effective in maintaining redness of ground beef followed by ascorbic acid +α-tocopherol + sesamol. Irradiation and storage reduced the b*-value of ground beef. Irradiation lowered ORP of ground beef regardless of antioxidants application methods, but ORP was lower in beef with mixing than spraying method. Beef sprayed with antioxidants produced more hydrocarbons and alcohols than the mixing application, but ascorbic acid +α-tocopherol + sesamol treatment was effective in reducing the amount of volatiles produced by irradiation. Therefore, mixing was better than the spraying method in preventing lipid oxidation and maintaining color of irradiated ground beef.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. References

Ground beef products represent about 44% of total fresh beef available for consumption in the U.S. (Breidenstein and Williams 1986). Meat color is one of the most important parameters that determine and affect consumer purchasing decisions. In retail cases, displaying meat under high-intensity lights accelerates the formation of metmyoglobin, which produces unattractive brown color (Faustman and Cassens 1990). Because of meat discoloration, retailers lose more than a billion dollars every year (Hermel 1993). Irradiation negatively impacts ground beef color by developing undesirable greenish or brownish gray color (Nanke and others 1998; Kim and others 2002a; Nam and Ahn 2003a).

Unlike popular belief, ground beef oxidizes faster than ground pork or poultry (Nam and others 2001; Kim and others 2002a). Under aerobic conditions, irradiation accelerates lipid oxidation in fresh raw pork and beef patties despite their intrinsic antioxidant activities (Ahn and others 1998a,b; Kim and others 2002b). Oxidative rancidity in food products are commonly measured by the 2-thiobarbituric acid (TBA) test, and sensory analysis of rancid odor shows strong correlations with TBA values in fresh and cooked ground beef (Tarladgis and others 1960; Poste and others 1986; Brewer and Harbers 1992).

Food antioxidants are used in fresh and further processed meat to prevent oxidative rancidity and improve color stability (Xiong and others 1993; Sanchez-Escalante and others 2001). Some phenolic antioxidants such as vitamin E have free-radical-scavenging properties and stop free-radical reactions in meat during storage (Gray and others 1996; Morrissey and others 1998). Therefore, the combinations of phenolic antioxidants such as gallate, sesamol, and tocopherol were effective in reducing the oxidative reactions in irradiated pork by scavenging free radicals produced by irradiation (Nam and Ahn 2003a). Ascorbic acid is a reducing agent, which prevents color changes in irradiated and nonirradiated ground beef during storage (Wheeler and others 1996; Lee and others 1999; Giroux and others 2001; Nam and Ahn 2003a).

In addition to color changes and accelerated lipid oxidation, irradiation produces off-odor volatiles in meat. Sulfur compounds are the major volatile compounds responsible for irradiation off-odor, and are produced mainly by radiolysis of sulfur-containing amino acids and are different from those of lipid oxidation (Ahn and others 1999a, 2000, 2001). Under aerobic conditions, the sulfur compounds were highly volatile and evaporated easily. However, under vacuum conditions, these compounds remained in meat (Ahn and others 2001). Although aerobic packaging was very effective in eliminating the sulfur volatiles produced by irradiation, the amounts of volatile aldehydes in irradiated ground beef significantly increased during storage unless antioxidant additives were added. Therefore, when irradiated beef is aerobically stored, the generation of lipid oxidation products is more concern than the S-volatiles (Ahn and Nam 2004). The objective of this study was to determine the effect of antioxidant application methods on the color, lipid oxidation, and off-odor volatiles of ground beef.

Materials and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. References

Sample preparation

Four blocks of beef chuck from 4 different animals were purchased from different grocery stores. Each meat block was trimmed off any visible fat, ground separately through a 6-mm plate and a 3-mm plate, and used as a replication. Eight batches of 4 antioxidant treatments were prepared. Four batches of them were used for mixing and the other 4 batches for spraying method. The antioxidant treatments were: (1) control, (2) 0.05% L-ascorbic acid (Fisher Scientific, Fair Lawn, N.J., U.S.A.), (3) 0.01% dl-α-tocopherol (Aldrich Chemical Co., Milwaukee, Wis., U.S.A.) + 0.01% sesamol (3,4-methylenedioxyphenol, final conc.; Sigma, St. Louis, Mo., U.S.A.), (4) 0.05% L-ascorbic acid + 0.01% dl-α-tocopherol + 0.01% sesamol. All the antioxidant treatments were on w/w basis and final concentrations. For the mixing application, each additive was added to the ground meat and then mixed for 2 min in a bowl mixer (Model KSM 90; Kitchen Aid Inc., St. Joseph, Mich., U.S.A.). Ground beef patties (approximately 50 g) were prepared by hand, placed individually on Styrofoam trays, and wrapped with clear stretch, oxygen-permeable meat film RMF-61 Hy (Borden Div., Borden Packaging and Industrial Products Inc., North Andover, Mass., U.S.A.), using a single-roll overwrapper (Model 600A, Heat Sealing Equipment Manufacturing Co., Cleveland, Ohio, U.S.A.). A dl-α-tocopherol was dissolve in corn oil first, and then oil emulsion (water-in-oil) was prepared using water or the aqueous solutions of ascorbate and/or sesamol before use.

For spraying method, ground beef patties were placed on large metal trays, and sprayed with antioxidant treatments on both sides using an electrostatic spraying device (Electrostatic Spraying System, Inc., Watkinsville, Ga., U.S.A.). After spraying, beef patties were placed individually on Styrofoam trays and wrapped as in mixing application. Prepared patties were stored overnight at 4 °C, and irradiated the next day morning. The additive treatments were applied as solution form: ascorbic acid and sesamol were dissolved in distilled water, while tocopherol was dissolved first in corn oil, and then oil emulsion was prepared using the aqueous solutions of ascorbic acid and/or sesamol. The same amounts of water and corn oil were added to all other treatments. For both application methods, 3 sets of samples were prepared and each set was used for color and chemical analyses at each storage time. For both mixing and spray applications, half of the patties from each antioxidant treatment was used for nonirradiated and the other half was used for irradiated meat.

Ionizing radiation

For irradiation treatment, ground beef patties from each antioxidant application was irradiated at 2.5 kGy using a linear accelerator facility (Circe IIIR; Thomson CSF Linac, St. Aubin, France) with 10 MeV of energy and 5.6 KW of power level. The average dose rate was 68.7 kGy/min. Alanine dosimeter were placed on the top and bottom surfaces of a sample and were read using a 104 Electron Paramagnetic Resonance Instrument (Bruker Instruments Inc., Billerica, Mass., U.S.A.) to check the absorbed dose. The dose range absorbed by meat samples was 2.45 to 2.95 kGy (max/min ratio was 1.20). The nonirradiated control samples were exposed to ambient temperature of linear acceleration facility while other samples were being irradiated. After irradiation, the irradiated and nonirradiated meat samples were immediately returned to a 4 °C cold room where they were displayed in a single layer on illuminated racks under standard fluorescent light (1000 lux, Philips, fluorescent light 40 W Cool White) for 7 d. Incident light reaching the sample surface had an intensity of 2018 lux. Color, lipid oxidation, volatile analysis, ORP, and CO production were determined at 0, 3, and 7 d of storage.

Thiobarbituric acid-reactive substances (TBARS) measurement

Lipid oxidation was determined using a TBARS method (Ahn and others 1999a). Five grams of ground beef were weighed into a 50-mL test tube and homogenized with 50 μL butylated hydroxytoluene (7.2% in ethanol) and 15 mL deionized distilled water (DDW) using a Polytron homogenizer (Type PT 10/35, Brinkman Instruments Inc., Westbury N.Y., U.S.A.) for 15 s at high speed. One milliliter of the meat homogenate was transferred to a disposable test tube (13 × 100 mm) and thiobarbituric acid/trichloroacetic acid (15 mM TBA/15% TCA, 2 mL) was added. The mixture was vortex mixed and incubated in a boiling water bath for 15 min to develop color. Then samples were cooled in ice-water for 10 min, mixed again, and centrifuged for 15 min at 2500 ×g at 4 °C. The absorbance of the resulting supernatant solution was determined at 531 nm against a blank containing 1 mL DDW and 2 mL TBA/TCA solution. The amounts of TBARS were expressed as milligrams of malonaldehyde (MDA) per kilogram of meat.

Volatile compounds

A purge-and-trap apparatus (Solatek 72 and Concentrator 3100; Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.) connected to a gas chromatograph/mass spectrometer (HP 6890/HP 5973; Hewlett-Packard Co., Wilmington, Del., U.S.A.) was used to analyze volatiles produced. The ground beef sample (3 g) was placed in a 40-mL sample vial, and the vial was flushed with helium gas (40 psi) for 5 s. The maximum waiting time of a sample in a refrigerated (4 °C) holding tray was less than 4 h to minimize oxidative changes before analysis (Ahn and others 2001). The meat sample was purged with helium gas (40 mL/min) for 14 min at 40 °C. Volatiles were trapped using a Tenax-charcoal-silica column (Tekmar-Dohrmann) and desorbed for 2 min at 225 °C, focused in a cryofocusing module (−80 °C), and then thermally desorbed into a capillary column for 60 s at 225 °C.

An HP-624 column (8.5 m × 0.25 mm i.d., 1.4 μm nominal), an HP-1 column (60 m × 0.25 mm i.d., 0.25 μm nominal; Hewlett-Packard Co.), and an HP-Wax column (6.5 m × 0.25 mm i.d., 0.25 μm nominal) were connected using zero dead-volume column connectors (J &W Scientific, Folsom, Calif., U.S.A.). Ramped oven temperature was used to improve volatile separation. The initial oven temperature of 30 °C was held for 6 min. After that, the oven temperature was increased to 60 °C at 5 °C/min, increased to 180 °C at 20 °C/min, increased to 210 °C at 15 °C/min, and then was held for 5 min at the temperature. Constant column pressure at 22.5 psi was maintained. The ionization potential of the mass selective detector (Model 5973; Hewlett-Packard Co.) was 70 eV, and the scan range was 19.1 to 400 m/z. Identification of volatiles was achieved by comparing mass spectral data of samples with those of the Wiley Library (Hewlett-Packard Co.). Standards were used to confirm the identification by the mass-selective detector. The area of each peak was integrated using the ChemStation (Hewlett-Packard Co.), and the total peak area (pA*seconds × 104) was reported as an indicator of volatiles generated from the sample.

Color measurement

The color of meat was measured on the upper and the bottom surfaces of meat samples using a Labscan spectrophotometer (Hunter Assoc. Labs Inc., Reston, Va., U.S.A.) that had been calibrated against white and black reference tiles covered with the same film as those used for meat samples. CIE L*- (lightness), a*- (redness), and b*- (yellowness) values were obtained (AMSA 1991) using an illuminant A (light source). Area view and port size were 0.64 and 1.02 cm, respectively. An average value from 2 random locations on each side, upper and lower, of sample surface was used for statistical analysis.

Oxidation-reduction potential (ORP)

The method of Moiseeve and Cornforth (1999) was used in determining the change of ORP in meat. A pH/ion meter (Accumet 25, Fisher Scientific) connected to a platinum electrode filled with a 4 M-KCl solution saturated with AgCl was tightly inserted in the center of meat sample. To minimize the effect of air, the smallest possible pore was made before inserting the electrode and recording the ORP readings (microvolts).

Carbon monoxide

To measure carbon monoxide (CO) produced by irradiation, CO gas was purchased from Aldrich (Milwaukee, Wis., U.S.A.). The standard gas was analyzed using a gas chromatograph (GC, Model 6890; Hewlett Packard Co., Wilmington, Del., U.S.A.) with a flame ionization detector (FID). Meat sample (10 g) was placed in a 24-mL glass vial, and the vials were flushed with helium gas (40 psi) for 5 s to minimize experimental errors due to air incorporation, then samples were microwaved for 10 s at full power. Ten minutes after microwave heating, the headspace gas of each sample (200 μL) was withdrawn using an airtight syringe and injected into a splitless inlet of a GC (Model 6890; Hewlett Packard Co.). A Carboxen-1006 Plot column (30 m × 0.32 mm id; Supelco, Bellefonte, Pa., U.S.A.) was used. Helium was used as a carrier gas at a constant flow of 1.8 mL/min and oven conditions were set at 120 °C. A FID equipped with a nickel catalyst (Hewlett Packard Co.) was used for the methanization of CO, and the temperatures of inlet, detector, and nickel catalyst were 250, 280, and 375 °C, respectively. Detector (FID) air, H2, and make-up gas (He) flows were 350, 35, and 40 mL/min, respectively. The identification of CO was achieved using standard gas, and the area of each peak was integrated by using the Chemstation software (Hewlett Packard Co.). To quantify the amount of gas released, peak areas (pA × seconds) were converted to the concentration (parts per million) of gas in the sample headspace (14 mL) using CO2 concentration (330 ppm) in air.

Statistical analysis

The experiment was an incomplete randomized design with 4 replications. Data were analyzed by the procedures of generalized linear model of SAS (SAS Inst. 1995). Student–Newman–Keuls' multiple-range test was used to compare the mean values of the treatments. Mean values and standard error of the means (SEM) were reported. Significance was defined at P < 0.05. Analysis of variance (ANOVA) was used to determine the effects of application methods, irradiation, additives and storage period on lipid oxidation, color, CO production, and oxidation-reduction potential of ground beef.

Results and Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. References

Lipid oxidation

Application method, irradiation, additives, and storage influenced the TBARS values of ground beef (Table 1). In control samples, irradiation had no effect on lipid oxidation of ground beef at 0 d regardless of application method. In ascorbate-added samples, however, irradiation accelerated lipid oxidation during storage. Ascorbate was effective antioxidant only in nonirradiated ground beef, and addition of ascorbate by mixing was better than spraying method. Spraying of ascorbate was effective only in nonirradiated ground beef. The effectiveness of ascorbic acid in lowering TBARS values decreased as storage period increased. Antioxidant combinations (α-tocopherol + sesamol and ascorbic acid +α-tocopherol + sesamol) were effective in preventing oxidative changes in irradiated and nonirradiated ground beef during storage regardless of application methods. Nam and Ahn (2003b) reported that sesamol +α-tocopherol and gallate +α-tocopherol were effective in preventing lipid oxidation in turkey breast meat during storage. The addition of ascorbic acid to ground meat in combination with such antioxidants as rosemary or α-tocopherol exerted a synergistic effect (Mitsumoto and others 1991; Sanchez-Escalante and others 2001). Liu and others (1994) found that the antioxidant effect of α-tocopherol in cooked meat was lower than that in raw meat. Pearson and others (1977) explained that the difference in α-tocopherol effect between raw and cooked meat could be due to protein denaturation, release of heme and noneheme iron, which resulted in the catalysis of lipid oxidation during and after cooking. Overall, adding antioxidants to ground beef by mixing was better than that by spraying method in preventing oxidative changes during storage.

Table 1—.  TBARS values of beef mixed or sprayed with different additives during storage at 4 °C.
 MixingSEMSprayingSEM
Non-IRIRNon-IRIR
 (mg MDA/kg meat) 
 Control0.870.91a0.260.97a0.75a0.16
 A0.33y0.50bx0.030.53by0.83ax0.06
 E + S0.290.34b0.030.42b0.47b0.05
 A + E + S0.300.35b0.030.47b0.55b0.04
 SEM0.140.12 0.120.05 
Day 3
 Control1.27a2.00a0.380.89ay1.94ax0.25
 A0.45by1.06bx0.110.76aby2.29ax0.17
 E + S0.26b0.30c0.030.37b0.45b0.04
 A + E + S0.31b0.33c0.030.37b0.46b0.03
 SEM0.200.20 0.110.19 
Day 7
 Control1.553.06a0.661.06ay3.01ax0.31
 A0.51y1.68bx0.150.85aby3.85ax0.43
 E + S0.310.36b0.030.42b0.45b0.05
 A + E + S0.30z0.36b0.030.46b0.51b0.04
 SEM0.300.37 0.140.35 
 DFF-valueP
  1. a–cValues with different letters within a column of each storage period are significantly different (P < 0.05).

  2. x–yValues with different letters within a row of each application are significantly different (P < 0.05).

  3. Non-IR = nonirradiated samples (0 kGy); IR = irradiated samples (2.5 kGy); Cont. = control; A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means (n= 4).

Application (A)111.880.0007
Irradiation (IR)171.350.0001
Additives (AD)385.120.0001
Storage (S)233.260.0001
A × IR15.580.0195
A × AD310.190.0001
A × S20.710.4948
IR × AD319.940.0001
IR × S218.310.0001
AD × S611.320.0001
A × IR × AD33.370.0203
A × IR × S21.920.1510
A × AD × S61.700.1242
IR × AD × S66.280.0001
A × IR × AD × S60.940.4698

Color values

Irradiation decreased the lightness (L*-value) of ground beef regardless of antioxidant application methods (Table 2). Similar results were reported by Zhu and others (2003) who found significant decrease in lightness values in irradiated turkey ham. Application methods influenced the lightness of beef at 0 d, but the differences were small. There were no differences in the L*-values between the upper and lower surfaces of beef patties and none of the antioxidant treatments affected the L*-value of ground beef. However, storage increased the L*-values of irradiated ground beef. Changes in L*-value itself may not have that much impact on beef color, but are important for light meat color. Especially, high L*-values in combination with increased a*-value intensify the redness of meat. Houser and others (2003) found that storage had no significant effects on the L*-value for irradiated cured ham. Also, Nam and Ahn (2002a) reported that packaging, irradiation and storage had no effect on the L*-value of precooked turkey breast.

Table 2—.  CIE color L*-values of beef mixed or sprayed with different additives during storage at 4 °C.
 MixingSEMSprayingSEM
Non-IRIRNon-IRIR
UpperLowerUpperLowerUpperLowerUpperLower
Day 0
 Cont.46.00w44.93abw42.67x41.02y0.4545.25w44.62w41.90x38.86y0.41
 A45.87w45.75aw41.87x41.05x0.5145.59w44.61w40.48x40.26x0.57
 E + S44.81w43.5bx40.95y40.82y0.4345.35w44.62w40.35x39.66x0.54
 A + E + S45.3w44.64abw42.09x41.28x0.5545.79w44.81w40.60x41.67x0.64
 SEM0.470.420.490.56 0.380.520.450.76 
Day 3
 Cont.45.49bc44.6345.2343.850.5143.33b42.8442.0942.000.56
 A47.46aw46.34w45.35wx43.84x0.6245.9aw44.8w43.44x41.23y0.45
 E + S44.48c44.6043.5643.090.7043.34b43.0142.5641.830.55
 A + E + S46.31abw44.75w44.91w43.21x0.4744.71abw44.16wx43.00wx42.47x0.53
 SEM0.490.680.600.52 0.460.580.500.55 
Day 7
 Cont.46.07cwx45.47abwx46.95aw44.66x0.5843.80wx42.92abx44.29w42.56x0.39
 A45.80a45.97a46.15a45.320.6343.1444.37a43.4843.570.60
 E + S44.71c44.08b43.93b43.610.5341.5641.94b42.3642.330.55
 A + E + S44.11b43.89b43.40b43.010.5741.8142.86ab42.4742.950.75
 SEM0.660.470.560.61 0.640.510.550.48 
 DFF-valueP DFF-value P
  1. a–cValues with different letters within a column of each storage period are significantly different (P < 0.05).

  2. w–yValues with different letters within a row of each application are significantly different (P < 0.05).

  3. Non-IR = nonirradiated samples (0 kGy); IR = irradiated samples (2.5 kGy); Cont = control; A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means (n= 4).

Application (A)1109.830.0001 IR × S 266.660.0001
Irradiation (IR)1159.530.0001 AD × S 67.380.0001
Additives (AD)35.560.0010 A × IR × AD 30.150.9321
Storage (S)226.640.0001 A × IR × S 21.080.3400
A × IR12.760.0974 A × AD × S 60.810.5623
A × AD31.230.2988 IR × AD × S 60.480.8251
A × S212.620.0001 A × IR × AD × S 60.400.8779
IR × AD34.020.0078    

Irradiation, antioxidant treatments, and storage influenced the redness (a*-value) of ground beef (Table 3). Irradiated ground beef had significantly lower redness values than nonirradiated ones. Adding antioxidants by spraying maintained higher a*-values than those by mixing method in nonirradiated meat for 3 d, but the difference was not consistent after 7 d. Antioxidant application methods had no effects on the a*-values of irradiated meat. No consistent difference in a*-value was observed between the upper and lower surfaces of ground beef. Among the antioxidant treatments, ascorbic acid was the most effective in maintaining red color in both irradiated and nonirradiated ground beef. Addition of tocopherol + sesamol had negative effect on the a*-value of ground beef. Nam and Ahn (2003b) showed that addition of sesamol significantly reduced the redness of turkey breast meat after storage. In all antioxidant treatments, a*-values started to decrease with storage time regardless of application method. At 3 d, only ascorbic acid maintained the same level of redness values as 0 d. At day 7, the redness of ground beef was not acceptable regardless of antioxidant treatments and application methods. Luchsinger and others (1997) reported that beef patties irradiated at 2.0 kGy were less red than nonirradiated controls.

Table 3—.  CIE color a*-values of beef mixed or sprayed with different additives during storage at 4 °C.
 MixingSEMSprayingSEM
Non-IRIRNon-IRIR
UpperLowerUpperLowerUpperLowerUpperLower
Day 0
 Cont.27.23cw26.49cw15.87cx16.97bx0.5330.58aw30.18abw15.72cy16.95x0.33
 A30.43aw29.3ax17.23by16.70by0.2230.27aw30.79aw16.91bx16.3x0.49
 E + S26.90cw26.08cw16.95bx17.12bx0.3228.55bw29.02bcw16.91bx17.14x0.36
 A + E + S28.57bw28.02bw18.90ax18.61ax0.3528.96bw28.75cw18.26ax17.57x0.24
 SEM0.450.390.260.37 0.330.410.310.41 
Day 3
 Cont.21.66cw20.51cw16.05cx16.06cx0.5924.73cw25.27cw17.00bx16.80bx0.32
 A30.55aw29.53aw22.94ax22.36ax0.4530.24aw30.61aw21.77ax21.77ax0.46
 E + S19.60dw18.86dx16.37cy16.29cy0.2222.60dw23.35dw17.37bx17.19bx0.40
 A + E + S25.32bw25.16bw21.24bx21.12bx0.3326.76bw27.16bw21.32ax20.91ax0.40
 SEM0.410.520.310.43 0.410.510.270.37 
Day 7
 Cont.13.71c13.59b14.39b15.83c0.7516.21cwx16.93cw13.85bx15.58cwx0.68
 A21.76a19.87a22.89a22.99a0.9722.92aw22.64aw16.60ay19.50ax0.73
 E + S13.01cx14.41bwx13.85cx15.55cw0.4313.51dy15.04cx16.19awx17.12bw0.50
 A + E + S17.03bx17.75awx19.53bw19.80bw0.5918.15bx19.25buwx17.16ax20.36aw0.61
 SEM0.731.000.570.39 0.590.740.670.50 
 DFF-valueP DFF-value P
  1. a–cValues with different letters within a column of each storage period are significantly different (P < 0.05).

  2. w–yValues with different letters within a row of each application are significantly different (P < 0.05).

  3. Non-IR = nonirradiated samples (0 kGy); IR = irradiated samples (2.5 kGy); Cont = control; A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means (n= 4).

Application (A)19.220.0026 IR × S 2426.540.0001
Irradiation (IR)11582.860.0001 AD × S 6114.660.0001
Additives (AD)3118.260.0001 A × IR × AD 32.110.0987
Storage (S)2389.310.0001 A × IR × S 214.110.0001
A × IR178.810.0001 A × AD × S 67.430.0001
A × AD35.180.0016 IR × AD × S 68.270.0001
A × S24.280.0146 A × IR × AD × S 61.890.0823
IR × AD39.040.0001    

The yellowness (b*-values) of beef was dramatically decreased by irradiation in both application methods at day 0 (Table 4). While the b*-values of nonirradiated beef decreased over the storage time, those of the irradiated ones increased after 3 d of storage. Nanke and others (1999) reported that the yellowness values decreased in beef and pork because of irradiation. Ascorbic acid increased the yellowness of nonirradiated meat, but as storage period increased, the yellowness decreased. Overall, spraying of antioxidants was better than mixing in maintaining the color of ground beef for short term (<3 d). Significant increases in yellowness (b*-value) are frequently seen in irradiated meat, but its impact to overall color of meat because a*-value mainly determines the color of meat color.

Table 4—.  CIE color b*-values of beef mixed or sprayed with different additives during storage at 4 °C.
 MixingSEMSprayingSEM
Non-IRIRNon-IRIR
UpperLowerUpperLowerUpperLowerUpperLower
Day 0
 Cont.23.70bw23.70bw15.36cy17.34x0.5025.44w26.35aw15.46cy17.83x0.36
 A26.20aw25.30ax17.30by17.38y0.2825.19w26.44aw16.99bx17.51x0.44
 E + S24.08bw23.99bw17.65abx18.30x0.3224.55w24.96bw17.88abx18.65x0.40
 A + E + S24.96bw25.10aw18.60ax18.75x0.3625.04w24.94bw18.33ax17.67x0.31
 SEM0.380.320.350.42 0.360.350.350.45 
Day 3
 Cont.21.07cw21.42cw17.71cx18.34bx0.3722.27bx23.73bw18.34by19.15by0.35
 A26.25aw25.13aw20.81ax20.42ax0.4825.21aw26.29aw20.53ax20.72ax0.55
 E + S20.00c19.90d19.00b18.90a0.4020.74cx22.56bw19.28aby19.16by0.43
 A + E + S23.13bw22.93bw20.15ax20.23ax0.4023.38bw24.33bw20.04ax19.85abx0.41
 SEM0.430.450.330.44 0.410.580.390.38 
Day 7
 Cont.17.20b18.5217.43b18.39c0.4318.22bwx19.58w17.13x18.68w0.42
 A19.72a20.2320.84a20.81a0.6520.29aw21.04w17.50x20.00w0.45
 E + S18.26abwx19.15w17.63bx18.82bcwx0.3417.26by19.54w18.23x19.08wx0.33
 A + E + S18.56ab19.9519.53a19.65b0.4818.44bx20.38w17.41x19.70w0.42
 SEM0.570.560.470.33 0.370.430.350.46 
 DFF-valueP DFF-valueP
  1. a–cValues with different letters within a column of each storage period are significantly different (P < 0.05).

  2. w–yValues with different letters within a row of each application are significantly different (P < 0.05).

  3. Non-IR = nonirradiated samples (0 kGy); IR = irradiated samples (2.5 kGy); Cont = control; A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means (n= 4).

Application (A)10.470.4920 IR × S 2298.570.0001
Irradiation (IR)1994.560.0001 AD × S 620.600.0001
Additives (AD)370.290.0001 A × IR × AD 32.470.0615
Storage (S)2118.710.0001 A × IR × S 25.120.0064
A × IR111.290.0009 A × AD × S 63.250.0040
A × AD33.310.0204 IR × AD × S 65.990.0001
A × S20.530.5865 A × IR × AD × S 61.040.3978
IR × AD312.990.0001    

Oxidation-reduction potential

For both mixing and spraying applications of antioxidants, the ORP values of ground beef decreased after irradiation at 0 d (Table 5). The decrease of ORP by irradiation in ground beef was greater (lower ORP values) with mixing than spraying method. Lowered ORP in irradiated meat rapidly increased during storage under aerobic conditions as previously reported (Hannah and Simic 1985; Nam and Ahn 2002b). Addition of ascorbic acid lowered ORP values in both irradiated and nonirradiated beef regardless of application methods, but the decrease was greater by mixing than spraying. The other 2 antioxidant treatments (E + S, A + E + S) had a higher ORP values than ascorbic acid alone in both application methods, but mixing method was better than spraying in maintaining reducing conditions (low ORP) for short-term storage (3 d). After 3 d storage, the ORP values of all ground beef increased significantly.

Table 5—.  ORP values of beef mixed or sprayed with different additives during storage at 4 °C.
 MixingSEMSprayingSEM
Non-IRIRNon-IRIR
 (Unit: mVolt) 
Day 0
 Cont.30.13ax−87.75cy7.0156.75ax2.85cy8.02
 A−6.13b−17.38b6.1130.50b35.83b3.06
 E + S46.19a22.20a9.1249.73ay73.63ax4.70
 A + E + S7.58b8.53a4.1212.80c14.83c4.96
 SEM5.627.86 4.366.41 
Day 3
 Cont.69.58a95.05a9.66113.58a116.90a5.43
 A27.70b42.78b7.0072.93b74.93b4.97
 E + S80.15ay102.23ax6.10117.55ay120.88ax0.83
 A + E + S37.53by55.38bx4.8374.95b84.45b4.58
 SEM8.135.95 3.255.23 
Day 7
 Cont.44.38a92.3316.1468.38113.3315.80
 A−6.95by88.10x15.1238.13y98.55x9.57
 E + S72.23ay132.50x11.3546.23y111.65x7.74
 A + E + S55.03ay90.75x10.3038.35y93.15x8.16
 SEM15.7110.74  10.2111.39
 DFF-value P
  1. a–cValues with different letters within a column of each storage period are significantly different (P < 0.05).

  2. x–yValues with different letters within a row of each application are significantly different (P < 0.05).

  3. Non-IR = non-irradiated samples (0 kGy); IR = irradiated samples (2.5 kGy); Cont = control; A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means (n= 4).

Application (A)194.200.0001
Irradiation (IR)142.430.0001
Additives (AD)352.520.0001
Storage (S)2256.990.0001
A × IR10.810.3685
A × AD39.780.0001
A × S214.930.0001
IR × AD311.240.0001
IR × S286.850.0001
AD × S69.170.0001
A × IR × AD31.150.3309
A × IR × S28.380.0004
A × AD × S62.760.0143
IR × AD × S68.350.0001
A × IR × AD × S61.750.1135

CO production

Irradiation increased CO production from ground beef (Table 6). The amount of CO produced in irradiated ground beef was higher with mixing than spraying application in general, but was not consistent. CO was produced by radiolysis of meat components in meat by irradiation (Lee and Ahn 2004). E + S treatment produced smaller amounts of CO in irradiated ground beef after 3 and 7 d of storage, but other treatments had no effect. As storage period increased, the amount of CO in ground beef decreased regardless of application methods or antioxidant treatments.

Table 6—.  Carbon monoxide (CO) gas formation from beef mixed or sprayed with different additives during storage at 4 °C.
 MixingSEMSprayingSEM
Non-IRIRNon-IRIR
 (Unit: mVolt) 
Day 0
 Cont.38.86135.7235.6518.11y83.49x8.53
 A18.34y85.65x16.1811.50y91.68x8.99
 E + S22.43y91.70x14.1810.00y82.01x8.93
 A + E + S18.50y87.33x11.4810.84y97.23x12.87
 SEM13.8327.23 6.0512.77 
Day 3
 Cont.29.51ay100.56ax15.1823.97y74.27x4.33
 A22.09ay87.67abx7.9116.01aby82.90ax7.62
 E + S5.50by47.85bx5.015.76by49.68bx7.13
 A + E + S30.03ay69.23abx5.0028.10ay57.06abx5.47
 SEM4.2012.40 4.527.64 
Day 7
 Cont.0.00y85.09x7.140.00y49.94x4.01
 A0.00y61.19ax7.613.60y64.77ax3.87
 E + S0.00y27.26bx2.310.00y30.65bx1.89
 A + E + S0.00y61.04ax1.710.00y47.88abx5.42
 SEM0.007.65 1.805.36 
 DFF-value P
  1. a–cValues with different letters within a column of each storage period are significantly different (P < 0.05).

  2. x–yValues with different letters within a row of each application are significantly different (P < 0.05).

  3. Non-IR = nonirradiated samples (0 kGy); IR = irradiated samples (2.5 kGy); Cont = control; A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means. n= 4.

Application (A)16.530.0117
Irradiation (IR)1356.140.0001
Additives (AD)38.970.0001
Storage (S)227.940.0001
A × IR10.640.4255
A × AD32.560.0571
A × S20.600.5517
IR × AD32.290.0804
IR × S26.820.0015
AD × S60.880.5105
A × IR × AD31.640.1833
A × IR × S20.430.6511
A × AD × S60.540.7745
IR × AD × S60.970.4461
A × IR × AD × S60.150.9891

Volatiles production

Irradiation, antioxidants, and storage time influenced volatile production in both application methods (Table 7 and 8). Irradiation increased the production of total volatiles from beef at days 0 and 3. However, the amounts of total volatiles in nonirradiated ground beef were higher than those of irradiated ones regardless of antioxidant treatments or application methods due to great increase in alcohol content at day 7. Ethanol was the major alcohol and the content increased greatly in nonirradiated ground beef after 7 d of storage probably due to microbial growth. However, total plate count of microorganisms in the samples was not conducted. There was no clear trend in the production of all volatiles between mixing and spraying method.

Table 7—.  Volatile compounds of beef mixed with different additives during storage at 4 °C.
CompoundContAE + SA + E + SSEM
Non-IRIRNon-IRIRNon-IRIRNon-IRIR
  1. a–cValues with different superscripts within a row are significantly different (P < 0.05). n= 4.

  2. Non-IR = non-irradiated (0 kGy); IR = irradiated (2.5 kGy); A = ascorbic acid; E = vitamin E; S = sesamol; and SEM = standard error of the means.

  3. Hydrocarbons: 2-Methyl butane, propane, 1-pentene, pentane, 1-hexene, hexane, 1-heptene, heptane, octane, nonane; Ketones: 2-Propanone, 2,3-butanedione, 2-butanone, 2-pentanone, 2-heptanone; Alcohols: Ethanol, 1-propanol, 2-butanol, 1-pentanol, 2-methyl-1-propanol, 3-methyl-1-butanol, hexanol; Aldehydes: Acetaldehyde, propanal, 3-methyl butanal, hexanal, heptanal; Aromatics: Toluene.

 (Total ion counts × 104) 
Day 0
 Hydrocarbons9847bc13059b1047d8661c24038a25045a4642cd9592bc1681
 Ketones902712870101991471210102115589380141371597
 Alcohols658986015859785249907283496983521010
 Aldehydes2092a2480a706b1246b952b1118b969b1044b206
 Aromatics0c383b0c666a0c608a0c626a23
 Total volatiles27556c37392ab17811d33136c40082ab45612a19960d33750bc2485
Day 3
 Hydrocarbons6615cd13914b1823d10441bc20160a19542a4415d7213cd1435
 Ketones5359b7407ab6384ab8807ab9342a9603a6965ab8490ab835
 Alcohols7601abc8965a5289abc8123ab4037bc6578abc3752c5381abc941
 Aldehydes3325ab4646a653b1360b537b746b579b599b668
 Aromatics0c508b0c586a0c501b0c477b20
 Total volatiles22900bc35440a14149c29316ab34076a36970a15710c22161bc2763
Day 7
 Hydrocarbons7736cd17160b3717d10430c20390b27688a8318cd8922c1329
 Ketones18085123781305611727132621276912634117631878
 Alcohols40494a10511b52917a7536b12671b4434b17452b3706b6854
 Aldehydes3420b9138a3156b1970b1301b833b1632b559b1240
 Aromatics0c553a0c506a146b564a189b488a21
 Total volatiles69735a49740ab72846a32169b47770ab46288ab40225ab25439b8582
Table 8—.  Volatile compounds of irradiated and nonirradiated ground beef with antioxidants added by spraying during storage at 4 °C.
CompoundContAE + SA + E + SSEM
Non-IRIRNon-IRIRNon-IRIRNon-IRIR
  1. a–dValues with different superscripts within a row are significantly different (P < 0.05). n= 4.

  2. Non-IR = nonirradiated (0 kGy); IR = irradiated (2.5 kGy); A = ascorbic acid; E = vitamin E; S = sesamol; SEM = standard error of the means.

  3. Hydrocarbons: 2-Methyl butane, 1-pentene, pentane, 1-hexene, hexane, 1-heptene, heptane, octane, nonane; Ketones: 2-Propanone, 2,3-butanedione, 2-butanone, 2-pentanone, 3-hexanone, 2-heptanone; Alcohols: Ethanol, 1-propanol, 1-butanol, 2-butanol, 1-pentanol, 1-hexanol, 2-methyl-1-propanol, 3-methyl-1-butanol; Aldehydes: Acetaldehyde, propanal, 3-methyl butanal, hexanal, heptanal; Aromatics: Toluene.

 (Total ion counts × 104) 
Day 0
 Hydrocarbons12499bc17180a3617e8066de7248de14884ab6416de8933cd1235
 Ketones1060311553938913762105181168110044125641737
 Alcohols12843ab13912a11521ab14107a10919ab11703ab9572b10740ab815
 Aldehydes1474ab1927a705c1454ab1257abc1822ab1108bc1688ab172
 Aromatics0c594ab0c591ab0c715a0c553b38
 Total volatiles37419abc45166a25231d37980abc29942cd40805ab27140cd34479bcd2398
Day 3
 Hydrocarbons7721b14966a3544b9315ab6139b15827a3372b7211b1921
 Ketones52187080551780575340639353127235773
 Alcohols10123bc13135ab10263bc14101a8252c10264bc7064c9803bc829
 Aldehydes1645b5575a1311b4824a553b1483b407b1493b621
 Aromatics0b500a0b495a0b445a0b502a27
 Total volatiles24707bc40256a20634c35802a20284c33523ab16156c25240bc2615
Day 7
 Hydrocarbons10212ab16112a5046c13245a11310a9537bc3790c7311c1461
 Ketones13542a11063abc10193bc9800bc12689ab9073c11973abc9643bc710
 Alcohols30612a11136b23866ab9858b30657a7179b29487a6172b4357
 Aldehydes2409b7085a1396b9343a2231b896b1558b640b945
 Aromatics0c512ab0c558a0c479b0c472b17
 Total volatiles56776a45909ab40501abc42804abc56887a27163c46809ab24238c4981

With mixing method (Table 7), the amounts of hydrocarbons were the highest in irradiated meat with E + S treatment and the lowest in nonirradiated meat with ascorbic acid treatment. Aldehydes were produced the most in control beef regardless of irradiation treatment and increased as storage time increased. Acetaldehyde, propanal, 3-methyl-butanal, hexanal, and heptanal were the aldehydes detected in ground beef, but the amount of hexanal increased the most after 3 and 7 d of storage, especially in irradiated meat with control and ascorbic acid treatments. Addition of α-tocopherol + sesamol or ascorbic acid +α-tocopherol + sesamol was more effective than ascorbic acid in lowering the amounts of aldehydes in irradiated beef. Aromatic compounds, mainly tolune, were produced only in irradiated ground beef. Similar trends were detected in meat with spraying application (Table 8). Nam and others (2006) reported that the combination of rosemary-tocopherol reduced the amount of hexanal in irradiated pork loin by 30%. Hexanal is a common indicator of lipid oxidation in meat (Ahn and others 1999b). Sulfur compounds were detected only in irradiated meat but the amounts were very small. The reason for the low sulfur volatiles in irradiated ground beef, especially at day 0, in this study is not clear, but could be related to the somewhat lengthy exposure of samples to aerobic conditions before analysis at day 0.

Conclusions

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. References

Antioxidant combinations E + S and A + E + S were highly effective in preventing oxidative changes in irradiated and nonirradiated ground beef. However, ascorbate alone was effective only in nonirradiated ground beef. Adding antioxidants in beef patties by spraying produced more volatiles, hydrocarbons, and alcohols, and had higher ORP values than those with mixing. This indicated that patties with tested antioxidants applied on the surfaces would be more susceptible to oxidative changes than those spread antioxidants throughout by mixing. Therefore, mixing method is recommended for applying ascorbic acid and antioxidants to avoid any quality changes in irradiated ground beef.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and Methods
  5. Results and Discussion
  6. Conclusions
  7. References