Research Note. Effect of Plant Extracts on Physicochemical Properties of Chicken Breast Meat Cooked Using Conventional Electric Oven or Microwave

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1 Research Note Effect of Plant Extracts on Physicochemical Properties of Chicken Breast Meat Cooked Using Conventional Electric Oven or T. M. Rababah,*,1 K. I. Ereifej,* M. A. Al-Mahasneh, and M. A. Al-Rababah* *Faculty of Agriculture, Jordan University of Science and Technology, PO Box 3030, Irbid, Jordan 22110; and and Faculty of Engineering, Jordan University of Science and Technology, PO Box 3030, Irbid, Jordan ABSTRACT This study evaluated effects of vacuuminfused and conventional electric oven, respectively. Meats fresh chicken breast meats with grape seed ex- tracts, green tea extracts, or tertiary butyl hydroquinone cooked by microwave had higher redness and lower lightness values than those cooked by conventional electric oven. Also, meats cooked by microwave had higher on ph, texture, color, and thiobarbituric reactive substances after cooking using a microwave or conventional maximum shear force, working of shear, hardness, springiness, cohesiveness, and chewiness values than electric oven for 12 d storage at 5 C. Thiobarbituric reactive substances values of uncooked (raw) chicken breast meats cooked by conventional electric oven. Tertiary butyl hydroquinone was the most effective in raw and meats for 0 to 12 d of storage ranged from 1.12 to 3.5 mg cooked meats in reducing lipid oxidation, followed by of malonaldehyde/100 g of chicken. During 0 to 12 d of grape seed and green tea extracts. Plant extracts are effective in preventing undesirable changes in chemical prop- storage, thiobarbituric reactive substances values ranged from 2.50 to 7.80 and from 2.4 to 7.35 mg of malonaldehyde/100 g of chicken breast meat cooked by microwave erties in chicken breast meat caused by microwave and conventional electric oven cooking. Key words: microwave, extract, physicochemical, property 2006 Poultry Science 85: INTRODUCTION The speed of cooking and ease of preparation with microwave ovens fits well into today s convenience-oriented lifestyle. Interest in microwave processing began shortly after World War II with the introduction of the first microwave. The first US patent for microwave cooking was granted to Raytheon Co. and was illustrated with a food product moving on a conveyor belt past a microwave source (Graves and Peckham, 1996). It is estimated that there are more than 225 million microwave ovens in homes in the industrialized world today. Penetration into households has reached above 100% in the USA, Japan, and Australia, and above 80% in the UK and the Nordic countries in Europe (Caballero et al., 2003). Most of the physicochemical properties that can be evaluated in meat products are color, ph, texture, and thiobarbituric acid-reactive substances (TBARS). Seideman et al. (1984) stated that meat color is considered one of the most important quality attributes for consumer acceptance. The ph is known as a crucial factor for meat quality (Nam et al., 2001). Gray et al. (1996) reported that 2006 Poultry Science Association, Inc. Received March 16, Accepted September 24, Corresponding author: rebabah@yahoo.com the likelihood of consumers to purchase food products depends on sensory properties such as flavor, appearance, and texture. The TBARS has been used to quantify malonaldehyde (MDA) oxidized in meat and meat product compounds (Jo and Ahn, 1998). Synthetic antioxidants have been commonly used for several years to retard or prevent lipid oxidation in foods (Ahmad, 1996). However, because of toxicological concerns of synthetic antioxidants, there have been increasing demands in identifying plant extracts to reduce or retard lipid oxidation in several products (Ahn et al., 1998). Green tea is rich in flavonoids that have antioxidant properties (Fadhel and Amran, 2002). Grape seed extracts contain large amounts of phenolic compounds and antioxidants (Yen and Chen, 1995). Rababah et al. (2004) found that grape seed and green tea extracts had the highest antioxidant activities compared within several plant extracts. The effect of green tea and grape seed extracts to prevent or minimize the physicochemical property changes that occur during cooking in conventional electric ovens or microwaves needs investigation. The objective of this study was to evaluate the effectiveness of vacuum infusion with green tea extracts, commercial grape seed extracts, or tertiary butyl hydroquinone (TBHQ) on physicochemical properties of fresh boneless chicken breast meats after cooking using a microwave or conventional electric oven for 12 d at 5 C. 148

2 EFFECT OF PLANT EXTRACTS ON COOKED CHICKEN 149 Table 1. Effect of storage time (12 d) on plant extract- and antioxidant-infused raw chicken breast meats stored at 5 C on thiobarbituric reactive substance (TBARS; mg of malonaldehyde/100 g of chicken) values TBARS (mg of malondialdehyde/100 g of chicken) 0d 6d 12d Treatment ppm Mean ± SEM Mean ± SEM Mean ± SEM Grape seed extract 2, ± 0.04 g 1.15 ± 0.04 g 1.48 ± 0.05 e Green tea extract 2, ± 0.05 g 1.16 ± 0.05 g 1.57 ± 0.06 d TBHQ ± 0.04 g 1.15 ± 0.04 g 1.31 ± 0.04 f Water control 1.12 ± 0.04 g 1.87 ± 0.06 c 3.34 ± 0.11 b Control as is 1.12 ± 0.04 g 1.87 ± 0.06 c 3.48 ± 0.12 a * a g Means followed by different letters in the same column or row are significantly different (P < 0.05). Materials MATERIALS AND METHODS Fresh boneless and skinless chicken breast meats were provided by a local poultry industry. Green tea (Celestial Seasonings, Inc., Boulder, CO) and Ziploc plastic bags were purchased from a local supermarket. The TBHQ (Tenox 20A; contains 20% TBHQ) was purchased from Eastman Chemical Company (Kingsport, TN). Commercial grape seed extract powder was obtained from Mega Natural Inc. (Madera, CA). Cryovac bags (type B-540 bags) were purchased from Cryovac Sealed Air Corporation (Duncan, SC). Methods Green Tea Extracts Preparation and Standardization. Green tea extracts were prepared and standardized as described by Rababah et al. (2004). Chicken Breast Infusion with Plant Extracts and TBHQ. Chicken breasts were marinated via a partial vacuum tumbling method with green tea extracts, commercial grape seed extracts, or TBHQ. Green tea and grape seed were used at 2,500 ppm, and TBHQ was used at 200 ppm based on 2.5% chicken fat. For water control, chicken breast meats marinated with deionized water, and control as is, without marination, were included for comparison. Four kilograms of chicken breast meat for each treatment were vacuum tumbled with 320 ml of antioxidant solutions (8% for 4-kg chicken) for 20 min under a vacuum of 63.5 cm of Hg using a vacuum tumbler (model LT-4 LyCo, Janesville, WI). All marination and infusion were conducted in a walk-in cooler at 5 C. The samples were then packaged in Cryovac bags (4 pieces of chicken breast per bag) and sealed by a vacuum impulse sealer (model PVS-GA18, PAC Packaging Aids Corporation, San Rafael, CA) with a sealing time of 4 s and a cooling time of 9 s. Packaging and sealing were done at atmospheric conditions. All packages were then double-bagged with Ziploc plastic bags. Storage Samples were evaluated for color, ph, texture, and TBARS values of cooked breast chicken meats using a microwave or conventional electric oven at 0, 6, and 12 d of storage at 5 C. For every targeted day of storage time, 3 chicken breast meats of each treatment and the controls for each type of cooking (microwave or conventional electric oven) were taken randomly for analyses. The remaining samples were kept at 5 C for the next targeted day. Analytical Determinations Color Measurement. Color of breast meat was measured by a colorimeter (Model CR-300, Minolta) and re- Table 2. Effect of storage time (12 d) on plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C on thiobarbituric reactive substance (TBARS; mg of malonaldehyde/100 g of chicken) values TBARS (mg of malondialdehyde/100 g of chicken) values using microwave TBARS (mg of malondialdehyde/100 g of chicken) values using conventional electric oven Grape seed extract 2, ± 0.11 i 3.05 ± 0.10 h 3.20 ± 0.11 h 2.45 ± 0.10 j 2.75 ± 0.08 i 3.05 ± 0.1 h Green tea extract 2, ± 0.09 i 3.50 ± 0.13 g 3.80 ± 0.14 f 2.50 ± 0.08 j 3.06 ± 0.10 h 3.45 ± 0.1 g TBHQ ± 0.08 j 2.55 ± 0.08 j 2.60 ± 0.09 i 2.40 ± 0.11 j 2.5 ± 0.10 j 2.65 ± 0.1 i Water control 2.78 ± 0.10 i 7.19 ± 0.23 c 7.81 ± 0.28 a * 2.55 ± 0.09 j 6.67 ± 0.26 e 7.37 ± 0.3 b Control as is 2.81 ± 0.11 i 6.85 ± 0.26 d 7.72 ± 0.34 a 2.55 ± 0.10 j 6.58 ± 0.25 e 7.21 ± 0.2 c a j Means followed by different letters in the same column or row are significantly different (P < 0.05).

3 150 RABABAH ET AL. Table 3. Shear force values of plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C for 12 d Grape seed extract 2, ± 1.19 a * 33.3 ± 1.20 a 32.8 ± 1.18 a 12.8 ± 0.46 b 12.1 ± 0.44 b 12.1 ± 0.44 b Green tea extract 2, ± 1.25 a 32.2 ± 1.33 a 32.9 ± 1.36 a 12.6 ± 0.40 b 12.0 ± 0.41 b 12.2 ± 0.47 b TBHQ ± 1.08 a 32.9 ± 1.26 a 32.2 ± 1.16 a 12.5 ± 0.40 b 12.2 ± 0.39 b 12.5 ± 0.40 b Water control 34.1 ± 1.16 a 32.4 ± 1.34 a 33.1 ± 1.37 a 12.8 ± 0.44 b 11.8 ± 0.49 b 12.8 ± 0.41 b Control as is 33.1 ± 1.27 a 33.9 ± 1.09 a 32.8 ± 1.05 a 13.8 ± 0.53 b 13.7 ± 0.46 b 13.8 ± 0.44 b corded using the L*a*b* color system. The L*a*b* color system consists of a luminance or lightness component (L*) and 2 chromatic components: the a* component for green ( a) to red (+a) and the b* component from blue ( b) to yellow (+b) colors. The colorimeter was calibrated using a standard white plate. Values of the white standard were L = 97.10, a = +0.13, and b = Color was measured at 3 positions at both sides. Three pieces were used for each treatment, and then the measurements were averaged. ph. An Orion 420A ph meter with a Ross ph electrode was used to determine the ph of meat at 6 different locations of breast meat ventral side length points and the same reading from the dorsal side. The measurements were averaged. Texture of Cooked Chicken Texture of cooked chicken breast meat was determined using a texture analyzer (TA-XT2I, Texture Technologies Corp., New York). Chicken breast meat was cooked in a conventional electric oven at 190 C (oven temperature) for 30 min according to a method described by Sams et al. (1988); meat was cooked in a microwave for 10 min. After that, samples were cooled at room temperature for 30 min. After cooling, samples were wrapped in aluminum foil and analyzed. Warner-Bratzler Shear. Cooked chicken breast was sampled by cutting strips (1.9 cm in width) parallel to the muscle fibers from the middle portion of the breast. A heavy-duty platform (TA 90, Texture Technologies) was placed at the base of the texture analyzer and secured. A slotted plate was inserted into the heavy-duty platform and was secured by tightening 2 thumbscrews. A shearing blade (TA 7 WB blade, Texture Technologies) was attached to the load cell carrier. The heavy-duty platform was repositioned to enable the blade to pass through the base plate. The load cell (25 kg) was calibrated using a 5-kg weight and was set to move at a pretest speed of 5 mm/s, a test speed of 10 mm/s, and a post-test speed of 5 mm/s with total travel of 50 mm. The shear test was performed by cutting the sample strip with the blade. The maximum shear force and work of shearing were recorded from the force deformation curve. Nine measurements were made for each treatment (3 strips per breast). Instrumental Texture Profile of Cooked Chicken. Texture profile analysis (TPA) was conducted according to Lyon and Lyon (1989) and Smith et al. (1988). Cores were obtained from the middle or anterior end of each cooked chicken breast. A core of 0.5 inches in diameter was taken from the middle or anterior end of each cooked chicken breast. The cores were wrapped in plastic and held at room temperature to prevent drying of samples before the analysis. A compression plate (3 inches in diameter) was attached to the load cell. Each sample was placed in the center of the lower compression plate, and the upper plate was lowered to compress the sample to 70% of its original height. Each sample was compressed twice to produce 2 compression curves (A1 and A2); the Table 4. Work of shearing values of plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C for 12 d 1 Grape seed extract 2, ± 1.92 a * 49.5 ± 1.59 a 50.9 ± 1.84 a 21.4 ± 0.77 b 21.9 ± 0.79 b 22.1 ± 0.67 b Green tea extract 2, ± 1.57 a 51.8 ± 1.87 a 50.3 ± 1.61 a 21.9 ± 0.70 b 22.7 ± 0.82 b 21.6 ± 0.78 b TBHQ ± 1.84 a 50.3 ± 1.53 a 51.3 ± 1.74 a 22.1 ± 0.75 b 21.9 ± 0.74 b 22.2 ± 0.71 b Water control 52.7 ± 1.69 a 50.4 ± 1.71 a 50.2 ± 1.61 a 22.1 ± 0.75 b 22.3 ± 0.76 b 22.1 ± 0.75 b Control as is 50.6 ± 1.95 a 54.0 ± 2.08 a 53.7 ± 2.07 a 24.3 ± 0.82 b 24.2 ± 0.93 b 24.1 ± 0.77 b

4 EFFECT OF PLANT EXTRACTS ON COOKED CHICKEN 151 Table 5. Hardness values of plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C for 12 d Grape seed extract 2, ± 4.13 a * ± 4.26 a ± 4.26 a 86.6 ± 2.94 b 88.9 ± 3.21 b 86.8 ± 2.95 b Green tea extract 2, ± 3.74 a ± 4.29 a ± 4.00 a 84.7 ± 2.57 b 85.2 ± 2.89 b 83.5 ± 2.54 b TBHQ ± 3.89 a ± 4.02 a ± 3.94 a 89.1 ± 3.02 b 88.0 ± 2.99 b 83.9 ± 2.85 b Water control ± 4.17 a ± 3.97 a ± 4.06 a 83.5 ± 2.68 b 84.0 ± 2.69 b 85.2 ± 2.73 b Control as is ± 4.52 a ± 4.50 a ± 4.58 a 85.7 ± 2.91 b 82.8 ± 2.99 b 86.8 ± 3.13 b second compression followed immediately after the upper plate returned to the sample s original height. The load cell (25 kg) was calibrated using a 5-kg weight. The load cell (25 kg) was set to move at a pretest speed of 5 mm/s, a test speed of 10 mm/s, and a post-test speed of 10 mm/s with trigger force of 40 g. Texture profile was used to determine instrumental hardness, springiness, cohesiveness, and chewiness of the poultry meat samples. The TPA hardness is the amount of force necessary to produce the first compression. The TPA springiness (D2/ D1) is calculated as the ratio of the distance or time of contact with the sample during the second compression (D2) to the same distance or time for the first compression (D1). The TPA cohesiveness is the ratio of the 2 total areas under the compression curves (A1 and A2). The TPA chewiness is the product of hardness, springiness, and cohesiveness. Nine measurements were made for each treatment to determine potential significant differences between treatments (3 cores per breast). TBARS Analysis for Raw and Cooked Meat Samples A modified fluorometric method was used to determine TBARS value in the raw and cooked chicken breast meats using microwave or conventional electric oven to evaluate lipid oxidation as described by Jo and Ahn (1998). Two-gram portions of raw and cooked (those were cooked in a conventional electric oven for 30 min and for 10 min using the microwave and were cooled for 15 min) meat samples were liquefied with 40 ml of deionized water in a blender (Osterizer Galaxie Dual Range 14, Oster Corp., Milwaukee, WI) for 1.5 min. To 1.0 ml of homogenate, 200 L of 8.1% SDS, 1.5 ml of 2M HCl, 1.5 ml of 20 mm TBA, and 50 L of 7.2% BHT were added and vortexed. The samples were then heated in 90 C water bath for 15 min and cooled in cold water for 10 min. After cooling, 1.0 ml of deionized water and 5.0 ml of n-butanol/pyridine (15:1) were added. The solutions were centrifuged (J2 to 21 Centrifuge, Beckman, Fullerton, CA) at 3,000 g and 20 C for 15 min. A blank was made using 1.0 ml of deionized water in place of the samples. The clear upper layer solutions were removed, and readings were taken using a Spectrofluorophotometer (Model RF-1501, Shimadzu, Kyoto, Japan) at 520 nm excitation and 550 nm emission. The calculation was made from the observed fluorescent intensity of samples using an equation of a standard curve of MDA as following: TBARS (in mg of MDA/100 g of chicken) = [( F ) 50 72]/10 F = Fluorescent intensity. Statistical Analysis Data were presented as means from 3 chicken breasts (3 replicates) taken randomly and analyzed using the mixed model procedure of ANOVA using SAS (2002) version 8.2 software package. The model included the Table 6. Springiness values of plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C for 12 d Grape seed extract 2, ± 0.02 a * 0.51 ± 0.02 a 0.49 ± 0.02 a 0.36 ± 0.01 b 0.31 ± 0.01 b 0.38 ± 0.02 b Green tea extract 2, ± 0.01 a 0.48 ± 0.01 a 0.48 ± 0.01 a 0.36 ± 0.02 b 0.38 ± 0.01 b 0.36 ± 0.02 b TBHQ ± 0.02 a 0.48 ± 0.02 a 0.48 ± 0.02 a 0.37 ± 0.01 b 0.37 ± 0.02 b 0.37 ± 0.01 b Water control 0.49 ± 0.01 a 0.49 ± 0.02 a 0.49 ± 0.01 a 0.37 ± 0.02 b 0.34 ± 0.02 b 0.36 ± 0.01 b Control as is 0.48 ± 0.02 a 0.49 ± 0.01 a 0.50 ± 0.02 a 0.38 ± 0.01 b 0.35 ± 0.01 b 0.39 ± 0.02 b

5 152 RABABAH ET AL. Table 7. Cohesiveness values of plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C for 12 d Grape seed extract 2, ± 0.01 a * 0.48 ± 0.01 a 0.48 ± 0.14 a 0.35 ± 0.01 b 0.33 ± 0.01 b 0.32 ± 0.01 b Green tea extract 2, ± 0.01 a 0.48 ± 0.02 a 0.49 ± 0.01 a 0.34 ± 0.01 b 0.36 ± 0.02 b 0.35 ± 0.02 b TBHQ ± 0.02 a 0.47 ± 0.02 a 0.49 ± 0.02 a 0.36 ± 0.02 b 0.35 ± 0.01 b 0.37 ± 0.01 b Water control 0.47 ± 0.01 a 0.49 ± 0.02 a 0.48 ± 0.01 a 0.37 ± 0.01 b 0.33 ± 0.01 b 0.31 ± 0.01 b Control as is 0.48 ± 0.02 a 0.49 ± 0.01 a 0.49 ± 0.02 a 0.35 ± 0.02 b 0.29 ± 0.02 b 0.35 ± 0.02 b main effects of replicates, infusion treatments (grape seed extracts, green tea extracts, TBHQ, water control, and control as is ), cooking methods (microwave and conventional electric oven), 3 storage times (0, 6, and 12 d), and their interactions. The experimental error term was used to test for the main effects and their interactions. Measured variables included TBARS, color, ph, and texture analysis. Means were separated by LSD analysis at a LSD P-value of RESULTS AND DISCUSSION TBARS for Raw and Cooked Chicken Breast Tables 1 and 2 show the effect of storage time at 5 C of antioxidant-infused raw and cooked chicken breast meats using microwave or conventional electric oven and controls on TBARS. During 0 to 12 d of storage, TBARS values ranged from 1.12 to 3.5 mg of MDA/100 g of chicken for raw breast meats. The TBARS values of cooked chicken using microwave and conventional electric oven ranged from 2.50 to 7.80 and from 2.4 to 7.35 mg of MDA/100 g of chicken, respectively. In general, TBARS values of cooked chicken using a microwave were higher than conventional electric oven values. This could be due to heat generated during microwave cooking. The antioxidant-infused raw and cooked chicken meats had similar effect on reducing TBARS values in both cooking methods. As compared with controls, the TBARS values of antioxidant-infused chicken breast meats were generally lower. The TBHQ was the most effective antioxidant to decrease lipid oxidation, followed by grape seed and green tea extracts. This could be attributed to the different types of phenolic compounds that have different antioxidant activities. Rababah et al. (2004) found that grape seed extracts had higher induction times (hour) values than green tea extracts using an oxidative stability instrument (OSI), even though they have similar phenolic compounds. Compared with controls, antioxidant infusions minimized lipid oxidation in raw and cooked samples for 0 to 12 d. The results demonstrated that TBHQ and grape seed and green tea extracts were effective in reducing lipid oxidation in raw and cooked meats with both cooking methods. Color Measurement The lightness (L*) values of chicken cooked using a conventional electric oven and microwave ranged from 50.3 to 56.2 and from 42.6 to 50.5, respectively. For 0 to 12 d of storage, grape seed extracts produced L* values of cooked chicken in the range of 51.2 to 53.7 and 42.6 to 47.3 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, green tea extracts produced L* values of cooked chicken in the range of 52.5 to 56.2 and 45.9 to 50.5 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, TBHQ produced L* values of cooked chicken in the range of 53.0 to 54.7 and 44.8 to 48.2 using a conventional electric Table 8. Chewiness values of plant extract- and antioxidant-infused cooked chicken breast meats stored at 5 C for 12 d Grape seed extract 2, ± 2.18 a * 51.2 ± 1.64 a 50.6 ± 1.73 a 12.6 ± 0.52 b 11.9 ± 0.49 b 11.2 ± 0.46 b Green tea extract 2, ± 1.96 a 49.7 ± 1.79 a 50.0 ± 1.86 a 11.8 ± 0.43 b 11.8 ± 0.43 b 12.0 ± 0.43 b TBHQ ± 1.81 a 50.0 ± 1.81 a 50.5 ± 1.79 a 11.8 ± 0.42 b 11.6 ± 0.42 b 11.7 ± 0.42 b Water control 49.5 ± 1.51 a 51.1 ± 1.64 a 50.9 ± 1.68 a 12.3 ± 0.42 b 10.3 ± 0.37 b 12.4 ± 0.38 b Control as is 49.1 ± 1.67 a 50.4 ± 1.71 a 49.5 ± 1.56 a 11.0 ± 0.37 b 11.2 ± 0.38 b 11.7 ± 0.45 b

6 EFFECT OF PLANT EXTRACTS ON COOKED CHICKEN 153 oven and microwave, respectively. For 0 to 12 d of storage, water control produced L* values of cooked chicken in the range of 51.2 to 56.2 and 43.9 to 50.4 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, control as is produced L* values of cooked chicken in the range of 50.3 to 54.9 and 44.5 to 49.3 using a conventional electric oven and microwave, respectively. In general, cooking the samples in a microwave decreased L* values (P < 0.05) compared with a conventional electric oven. Addition of antioxidants did not produce any difference between the cooking methods. The redness (a*) values of chicken meat cooked using a conventional electric oven and microwave ranged from 1.1 to 1.7 and from 1.7 to 2.5, respectively. For 0 to 12 d of storage, grape seed extracts produced a* values of cooked chicken in the range of 1.3 to 1.7 and 1.6 to 2.0 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, green tea extracts produced a* values of cooked chicken in the range of 1.1 to 1.6 and 1.5 to 2.1 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, TBHQ produced a* values of cooked chicken in the range of 1.4 to 1.6 and 1.7 to 2.4 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, water control produced a* values of cooked chicken in the range of 1.1 to 1.7 and 1.4 to 2.0 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, control as is produced a* values of cooked chicken in the range of 1.4 to 1.5 and 1.7 to 1.9 using a conventional electric oven and microwave, respectively. Cooking the samples using a microwave increased the a* values of all samples. In general, myoglobin is the major pigment responsible for the color of meats. However, the mechanism of increasing redness in the microwave in poultry products is not yet known, but the increase in redness in the microwave could be due to the same reasons as irradiated poultry products. Katherine (1999) reported that the increase in red color in irradiated meats could be due to the production of carboxymyglobin, which is possibly what happens in meats cooked in a microwave. Also, the development of a pink color in poultry meats cooked in a microwave could be attributed to the production of CO myoglobin like what happens in irradiated meat (Nam and Ahn, 2002a). The yellowness (b*) values of cooked chicken meat using a conventional electric oven and microwave ranged from 3.3 to 5.2 and from 3.4 to 5.4, respectively, but no significant differences were found. For 0 to 12 d of storage, grape seed extracts produced b* values of cooked chicken in the range of 3.8 to 5.2 and 3.9 to 5.4 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, green tea extracts produced b* values of cooked chicken in the range of 3.4 to 4.6 and 3.5 to 4.6 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, TBHQ produced b* values of cooked chicken in the range of 3.6 to 4.9 and 3.8 to 4.9 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, water control produced b* values of cooked chicken in the range of 3.3 to 4.4 and 3.4 to 4.5 using a conventional electric oven and microwave, respectively. For 0 to 12 d of storage, control as is produced b* values of cooked chicken in the range of 3.4 to 4.5 and 3.5 to 4.3 using a conventional electric oven and microwave, respectively. In general, addition of antioxidant or plant extracts did not have any significant effect on L*, a*, and b* values between cooked chicken using a conventional electric oven or microwave. ph The ph values were approximately 6.00 in all chicken breast meats. The ph values of cooked chicken using a conventional electric oven and microwave ranged from 5.98 to 6.16 and 5.92 to 6.12, respectively. No significant differences (P < 0.05) were observed in any of the treatments. Texture of Cooked Chicken, Warner-Bratzler Shear. Maximum shear force and work of shearing values of cooked chicken breast meats using conventional electric oven or microwave are given in Tables 3 and 4. Maximum shear force values of cooked chicken using a conventional electric oven and microwave ranged from 12.0 to 13.8 and from 31.9 to 34.5, respectively. Work of shearing values of cooked chicken using a conventional electric oven and microwave ranged from 21.4 to 24.3 and 49.5 to 54.1, respectively. cooking of chicken breast meats increased maximum shear force and work of shearing values of both controls and plant extracts (P < 0.05) compared with electric oven cooking. Addition of plant extracts did not have an effect on maximum shear force and work of shearing values in both cooking methods. The increase of maximum shear force and work of shearing values in microwave cooking of chicken meats could be because of less denaturation of the myofibrillar and sarcoplasmic proteins (Roberts and Lawrie, 1974) that resulted in a tough texture of chicken breast. Another reason for increasing toughness of meat samples that were cooked in microwave could be due to high speed motions of molecules generated during the microwave cooking could pass through meat samples and compress and compact the chicken fibers, causing increasing maximum shear force, and consequently a less tender product (William, 2001; Batsanov, 1994). Instrumental Texture Profile of Cooked Chicken Texture profile analysis of hardness, cohesiveness, springiness, and chewiness values of cooked chicken using a microwave or conventional electric oven are given in Tables 5 to 8. The hardness values of cooked chicken using a conventional electric oven and microwave ranged from 82.8 to 88.9 and from to 119.6, respectively. The springiness values ranged from 0.34 to 0.39 and 0.48 to 0.51, respectively. The cohesiveness values of nonirradiated and irradiated chicken breast meat ranged from 0.29 to 0.37 and from 0.46 to 0.49, respectively. The chewi-

7 154 RABABAH ET AL. ness values ranged from 10.3 to 12.6 and 49.1 to 52.9, respectively. cooking of chicken meats increased the hardness, chewiness, springiness, and cohesiveness of both controls and plant extracts (P < 0.05) compared with electric oven cooking of meats. Addition of plant extracts did not affect these variables. cooking of chicken breast meats increased hardness, chewiness, springiness, and cohesiveness, and this could also be due to maximum shear force and work of shearing, and the explanation could also be similar. The results of this study showed that infusing plant extracts into skinless, boneless chicken breast meats could be an effective technique for minimizing undesirable changes in chemical properties during storage in both conventional electric oven and microwave cooking methods. In general, some changes were observed in TBARS values, color, and texture of cooked meats using microwave cooking compared with a conventional electric oven, whereas for ph no changes were observed. Grape seed extracts, green tea extracts, or TBHQ could have beneficial effects in reducing TBARS developed during storage. Infusion improved texture of chicken breast meats cooked using a microwave or conventional electric oven. The conventional electric oven could be considered a better cooking method for keeping higher physicochemical properties than microwaving of chicken breast meats. REFERENCES Ahmad, J. I Free radicals and health: Is vitamin E the answer? Food Sci. Technol. 10: Ahn, D. U., D. G. Olson, J. I. Lee, C. Jo, C. Wu, and X. Chen Packaging and irradiation effects on lipid oxidation and volatiles in pork patties. J. Food Sci. 63: Batsanov, S. S Effects of Explosions on Materials, Modification and Synthesis Under High Pressure Shock Compression. Springer-Verlag, New York, NY. Caballero, C., L. C. Trugo, and P. M. Finglas Pages in Encyclopedia of Food Sciences and Nutrition. 2nd ed. Vol. 7. Acad. Press, Amsterdam, The Netherlands. Fadhel, Z. A., and S. Amran Effects of black tea extract on carbon tetrachloride-indced lipid peroxidation in liver, kidneys, and testes of rats. Phytother. Res. 16: Graves, J. H., and G. C. Peckham Foundation of Food Preparation. Merrill, Englewood Cliffs, NJ. Gray, J. I., E. A. Gomaa, and D. J. Buckley Oxidative quality and shelf life of meats. Meat Sci. 34: Jo, C., and D. U. Ahn Fluorometric analysis of 2-thiobarbituric acid reactive substances in turkey. Poult. Sci. 77: Katherine, B The effect of irradiation and modified atmosphere on the quality of chill-stored turkey breast. Ph.D. Diss. Kansas State Univ., Manhattan. Lyon, B. G., and C. E. Lyon Texture profile of broiler pectoralis major as influenced by post-mortem deboning time and heat method. Poult. Sci. 69: 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: Nam, K. C., D. U. Ahn, M. Du, and C. Jo Lipid oxidation, color, volatiles, and sensory characteristics of aerobically packaged and irradiated pork with different ultimate ph. J. Food Sci. 66: Rababah, T. M., N. S. Hettiarachchy, and R. Horax Total phenolics and antioxidant activities of fenugreek, green tea, black tea, grape seed, ginger, rosemary, gotu kola, and ginkgo extracts, vitamin e, and tert-butylhydroquinone. J. Agric. Food Chem. 52: Roberts, P. C. B., and R. A. Lawrie Effects of bovine L. dorsi muscle of convectional and microwave heating. J. Food Technol. 9: Sams, A. R., D. M. Janky, and S. A. Woodward Comparison of two shearing methods for objective tenderness evaluation and two sampling times for physical-characteristic analysis of early-harvested broiler breast meat. Poult. Sci. 69: SAS User s Guide. Release 8.2 ed., SAS Institute Inc., Cary, NC. Seideman, S. C., H. R. Cross, G. C. Smith, and P. R. Durland Factors associated with fresh meat color: A review. J. Food Qual. 6: Smith, D. P., C. E. Lyon, and D. L. Fletcher Comparision of the Allo-Kramer shear and texture profile methods of broiler meat texture analysis. Poult. Sci. 67: William, S Introduction to Astronomy. Available: matter_phases/. Accessed Jul. 15, Yen, G. C., and H. Y. Chen Antioxidant activity of various tea extract in relation to their antimutagenicity. J. Agric. Food Chem. 43:27 32.