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Functional properties of raw and cooked pork patties with added irradiated, freeze-dried green tea leaf extract powder during storage at 4 °C
Meat Science 64 (2003) 13–17 www.elsevier.com/locate/meatsci
Functional properties of raw and cooked pork patties with added irradiated, freeze-dried green tea leaf extract powder during storage at 4 C Cheorun Joa, Jun Ho Sona, Cheon Bae Sonb, Myung Woo Byuna,* a
Team for Radiation Food Science and Biotechnology, Korea Atomic Energy Research Institute, PO Box 105, Yuseong, Daejeon, 305-600, South Korea b Department of Food and Nutrition, Chungnam National University, Daejeon, 305-764, South Korea Received 25 October 2001; received in revised form and accepted 8 May 2002
Abstract Functional and sensory properties of raw and cooked pork patties with added irradiated freeze-dried green tea leaf extract powder were studied. Components of green tea were extracted by 70% ethanol, and the extract was irradiated to obtain a bright color. The irradiated green tea extract was freeze-dried and the powdered sample (0.1%) was added to the pork patties (Trt C). Pork patties without any ingredient (Trt A) and with nonirradiated, freeze-dried green tea extract powder (Trt B) were also prepared for comparison. Lipid oxidation, radical scavenging effect, color, and sensory properties of pork patties with treatments were analyzed at 5-day intervals for 15 days with storage at 4 C. The lipid oxidation had a lower (P< 0.05) and radical scavenging effect was greater (P< 0.05) in the raw and cooked pork patties with added Trt B and Trt C, than those of Trt A (control). The pork patties with Trt B and Trt C had a higher Hunter color a*-value and less cooking loss than that of Trt A. Sensory panelists preferred the odor of the raw pork patties and color of the cooked pork patties of Trt C (P <0.05). Generally, no significant difference between Trt B and Trt C was found. Therefore, irradiated, freeze-dried green tea extract powder can be used for producing functionally-improved meat products. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Green tea extract; Pork patties; Irradiation; Storage
1. Introduction In order to achieve healthier meat and meat products, two methods can be applied: avoiding undesired substances or reducing them to appropriate limits, and increasing the levels (naturally or by programmed addition) of other substances with beneficial properties (Jimenez-Colmenero, Carballo, & Cofrades, 2001). Currently, exogenous antioxidants such as phenolic compounds, tocopherols, plant derivatives and chelating agents are added to raw meat patties or cooked meat products to improve oxidative stability. Tea catechins, a predominant group of polyphenols present in green tea leaf (Camellia sinensis L.), to inhibit lipid oxidation in edible oil (Wang & Zhao, 1997) and had a greater antioxidative effect than the butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tertiary butyl hydroquinone (TBHQ), and the * Corresponding author. Tel.: +82-42-868-8060; fax: +82-42-8688043. E-mail address: [email protected] (M.W. Byun).
natural antioxidant vitamin E depending on the types and concentration of the tea catechins used (Wanasundara & Shahidi, 1998). In addition, antimutagenic activity (Ruan, Liang, Liu, Tu, & Liu, 1992; Stich, Chan, & Rosin, 1982), suppressive effect of chromosome aberration (Yokozawa, Oura, Sakanaks, Ishigaki, & Kim, 1994) or inhibitory effects on arteriosclerosis (Kimura et al., 1983) were also investigated. The components from the green tea leaf and their soluble matters have a scavenging effect on the 1,1-diphenyl-2-picrylhydrazyl radical (Nanjo et al., 1996). The antimicrobial activity of water or ethanol extracts of green tea (steamed or roasted), oolong tea, and black tea was also reported (Oh, Lee, & Park, 1999). The green tea leaf has been used mainly for drinking with boiling water, despite successful use in food or cosmetics. This is probably because of its dark red color and off-flavor, which make it very difficult to apply sufficient amount in cosmetics, medicine, or foods. Irradiation can solve these problems (Jo, Son, & Byun, in press) as it can change the color of green tea leaf extract from dark red to a slightly bright yellow by 70% ethanol extraction. These can be stored without color
0309-1740/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(02)00131-6
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reversion by freeze-drying. The irradiated and powdered extract, which had improved color, was successfully applied to the cosmetic industry since the irradiation did not reduce the physiological benefits, such as the scavenging effect of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and the tyrosinase inhibitory effect (Son, Jo, Kim, Kim, & Byun, 2001). The objective of the present study is to investigate the effect of the addition of irradiated, freeze-dried green tea leaf extract powder to raw and cooked pork patties on lipid oxidation, color, sensory, and the DPPH radical scavenging effect.
2. Materials and methods 2.1. Preparation of green tea leaf extract Dried green tea leaf was purchased from the Bosung area in Chonnam, Korea, and 200 g were weighed, transferred to ethanol solution (70%, 4 l), and extracted overnight. Extraction was performed twice and the extract was divided into two groups, labeled treated by irradiation or not. 2.2. Irradiation and freeze-drying Samples in tightly capped containers (2 l) were irradiated in a cobalt-60 irradiator (point source, AECL, IR-79, Nordion, Canada) with 20 kGy absorbed doses. The source strength was approximately 100 kCi with a dose rate of 83 Gy min 1 at 15 0.5 C. Dosimetry was performed using 5 mm diameter alanine dosimeters (Bruker Instruments, Rheinstetten Germany), and the free-radical signal was measured using a Bruker EMS 104 EPR Analyzer. The actual dose was within 2% of the target dose. The sample was turned 360 continuously during the irradiation process to achieve uniform target doses and the nonirradiated control was placed outside of the irradiation chamber in order for it to have the same environmental temperature effect as the irradiating sample. Ethanol in the irradiated green tea leaf mixture was removed by laboratory evaporator (Rotary Evaporator N-11, Tokyo, Japan) immediately after irradiation and freeze-dried (SFDSF12, Samwon Co. Ltd., Pusan, Korea). The dried sample (28.3 0.11 g/100 g green tea leaf) was collected and used as an ingredient in the pork patties. 2.3. Patties preparation The longissimus dorsi muscle from pigs were obtained 24 h after slaughter from three different local meat packers, and ground twice through a 9-mm plate. Patties (approximately 100 g each) were prepared without
(Trt A) or with 0.1% freeze-dried green tea leaf extract (Trt B) and 0.1% irradiated, freeze-dried green tea leaf extract (Trt C). The prepared raw pork patties were packaged in oxygen permeable polyethylene and stored for 15 days at 4 C. 2.4. Color measurement The patty was placed on the plate of a Color Difference Meter (Spectrophotometer CM-3500d, Minolta Co., Ltd. Osaka, Japan) and measured. The instrument was calibrated to standard black and white tiles before analysis. Four different areas of patty per treatment were evaluated and mean values were used for replication. A medium size aperture was used and the measurement was duplicated. The Hunter color L*-, a*-, and b*-values were reported through the computerized system using Spectra Magic software (version 2.11, Minolta Cyberchrom Inc. Osaka, Japan). 2.5. Scavenging effects of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The sample (2 g) was transferred to a 20 ml-test tube and homogenized (DIAX 900, Heidolph Co., Ltd., Germany) for 15 s at speed setting 6 (approximately 23,000 rpm) with 8 ml of deionized distilled water (DDW). The mixture was filtered by a filter paper (No. 4., Whatman International Ltd., Springfield Mill, Maidstone, Kent, England) and chloroform (2 ml) was added into the filterate. The tube with filterate was vortexed vigorously to remove any fat in the sample and centrifuged (VS 5500, Vision Scientific Co., Ltd. Bucheon, Korea) at 2400 rpm for 30 min. The upper layer of the mixture was diluted 5 times with DDW, and the free radical scavenging effect was estimated according to the method of Blois (1958) with some modification. A sample (1 ml) was added into the 0.2 mM DPPH radical (1 ml). The mixture was shaken and left to stand for 30 min at room temperature and measured at 517 nm with a spectrophotometer. 2.6. Lipid oxidation, fatty acid composition, and sensory analysis Lipid oxidation was determined as a 2-thiobarbituric acid reactive substances (TBARS) value by using a spectrophotometer (UV 1600 PC, Shimadzu, Tokyo, Japan) as described by Ahn, Olson, Jo, Love, and Jin (1999). The lipid oxidation development was reported as mg malondialdehyde/kg meat sample. Fatty acid composition was analyzed by the method of Jo and Ahn (2000) using a gas chromatograph (GC, Model 6890, Agillent Tehcnologies Inc., Palo Alto, CA) equipped with a flame ionization detector (FID). A split inlet (split ratio, 20:1) was used to inject samples into a
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capillary column (DB Wax, 60 m250 mm0.25 mm nominated, J&W Scientific Inc., Folsom, CA) and ramped oven temperature was used (180C for 5 min, increased to 220 C at 2.5 C/min, kept constant for 20 min). Injection was achieved by an Agillent Model 7683 injector (Agillent Technologies, Inc.). Inlet and detector temperature were 210 C. Nitrogen was the carrier gas at constant flow of 1.1 ml/min. Detector air, N2, and make-up gas (N2) flows were 300, 30, and 28 ml/min, respectively. The obtained chromatogram was integrated using a GC Chemstation software (Rev. A.08.03, Agillent Technologies, Inc.). Trained panelists (n=10) were used to evaluate sensory properties of the raw and cooked pork patties. A patty was placed on a preheated pan at about 170 C and pressed after 30 s. After 1.5 min, the patty was turned over and left for another 1.5 min. The temperature of the center of patty reached approximately 78 C. Average pan temperature during cooking was 160 C. After cooling for 2 min at room temperature, the patties were sliced into four similar pieces and served to the panelists individually. The sensory parameters for the raw patties were color and odor, and for the cooked patties, color, odor, taste, and tenderness were evaluated independently by the panelists on each of the three different occasions. A 15 cm line-scale was provided to the panelists and it was anchored as follows; very undesirable (0) to very desirable (15) for color, strong off-odor (0) to very mild odor (15) for odor, very poor taste (0) to excellent (15) for taste, and very tough (0) to very tender (15) for tenderness. 2.7. Statistical analysis The experimental design used was a 3 treatments 3 storage factorial and the whole experiment was duplicated. Two-way Analyses of Variance was performed using SAS software (SAS Institute, 1989) and the Student–Newman–Keul’s multiple range test was used to compare differences among mean values. Mean values and pooled standard errors of the mean (SEM) were reported, and the significance was defined at P < 0.05.
3. Results and discussion 3.1. Lipid oxidation The TBARS value of the raw pork patties increased during 15 days of storage in all treatments; however, the TBARS values of the patties with added freeze-dried green tea leaf extract powder (0.1%) were significantly lower than those of the control, Trt A (Table 1). There was no significant difference between irradiation and nonirradiation treatment to the green tea leaf extract. McCarthy, Kerry, Kerry, Lynch, and Buckley (2001)
Table 1 TBARS values (mg malondialdehyde/kg meat) of raw and cooked pork patties with added nonirradiated or irradiated freeze-dried green tea leaf extract powder (0.1%) SEMa
Storage day 0
5
10
15
Raw pork patties Trt A 0.38cx Trt B 0.28by Trt C 0.30by 0.021 SEMb
0.56bx 0.42ay 0.36az 0.016
0.56bx 0.43ay 0.35ay 0.025
0.69ax 0.48ay 0.39ay 0.028
0.029 0.024 0.016
Cooked pork patties Trt A 1.13bx Trt B 0.48z Trt C 0.58ay SEMb 0.027
1.22abx 0.42y 0.36by 0.048
1.38ax 0.42y 0.44by 0.043
1.21abx 0.44y 0.31by 0.048
0.044 0.042 0.042
Trt A, only pork patties; Trt B, patties with nonirradiated, freeze-dried green tea leaf extract powder (0.1%); Trt C, patties with irradiated at 10 kGy, freeze-dried green tea leaf extract powder (0.1%). Different letters (a–c) within the same row differ (P<0.05). Different letters (x– z) within the same column with raw and cooked pork patties differ (P<0.05). a Pooled standard errors of the mean (n=6). b (n=8).
reported that tea catechins were the most effective in reducing lipid oxidation in fresh or frozen pork patties among nine natural antioxidants used. Cooked meat is more susceptible to lipid oxidation than raw meat during refrigerated and frozen storage due to the fact that heating accelerates oxidative reactions with the lipid in meat (Kingston, Monahan, Buckley, & Lynch, 1998). In cooked pork patties, the TBARS values of the control significantly increased compared to the raw pork patties but both patties treated with freeze-dried green tea extract powder, Trt B and Trt C, maintained almost the same values as the raw pork patties except for at day 0 (P < 0.05). It is indicated that the added green tea extract powder significantly reduced the lipid oxidation development of the pork patties. There was no difference found in the lipid oxidation of patties between Trt B and Trt C. Tang, Kerry, Sheehan, Buckley, and Morrissey (2001) reported that dietary tea catechin supplementation to chicken at 50–300 mg/kg feed, showed antioxidative effects for both the breast and thigh meat during 10 days of refrigerated and 9 months of frozen storage. Furthermore, McCarthy et al. (2001) concluded that the tea catechin was the most effective antioxidant in raw and cooked pork patties among the natural food/plant extract or synthetic antioxidants. 3.2. Scavenging effects of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The radical scavenging effect in raw pork patties with Trt A was 30.9%, but 58.1 and 62.0% in the patties
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with added Trt B or Trt C (Table 2). The addition of green tea leaf extract powder significantly increased the radical scavenging effect of raw pork patties but no difference was found between irradiation treatments to the extract. The radical scavenging effect was significantly reduced (P < 0.05) by the cooking of the raw pork patties (Table 2). The cooked pork patties with control (Trt A) was 19.26–26.41% of radical scavenging during storage without significant changes. However, the cooked pork patties with Trt B had a higher radical scavenging effect than that with Trt A. The radical scavenging effect of pork patties with Trt C was also higher than that with Trt A. Between the patties with added nonirradiated and irradiated green tea extract powder (Trt B and Trt C), there was no difference found. Byun, Son, Yook, Jo, and Kim (2001) reported that 5, 10 and 20 kGy of irradiation to Korean traditional soybean-based fermented food, Chungkookjang and Doenjang, did not change physiological activities such as angiotensin converting enzyme inhibition, xanthine oxidase inhibition, tyrosinase inhibition, as well as radical scavenging ability. Son et al. (2001) and Jo et al. (in press) also concluded that irradiation technology can enhance the color of green tea leaf extract without any adverse change in physiological activities.
was irradiated or not, had a generally higher Hunter color L*-value. The a*-value was higher in the patties without green tea extract powder at Day 0, but during storage the patties with added green tea extract powder had a higher a-value than that of the control (Table 3). In a comparative study of McCarthy et al. (2001), butylated hydroxyanisol/butylated hydroxytoluene (BHA/BHT, 0.01%) was the most effective for preserving the meat redness of pork patties among 11 test food ingredients with optimum concentrations. In the same study, the pork patties with tea catechin (0.25%) also had a higher Hunter color a*-value than that of the control from the beginning. The Hunter color b*-value Table 3 Color changes of raw pork patties added with nonirradiated or irradiated green tea leaf extract powder (0.1%) Treatment
0
5
10
SEMa
L*
Trt A Trt B Trt C SEMb
53.13y 56.04x 54.44bxy 0.684
55.37y 56.42ay 57.96ax 0.666
54.16y 56.03x 57.10ax 0.473
0.591 0.710 0.530
a*
Trt A Trt B Trt C SEMb
4.84ax 4.39ax 4.34ay 0.280
4.15b 4.24a 4.36a 0.289
3.08cy 3.68bx 3.89bx 0.179
0.242 0.277 0.159
b*
Trt A Trt B Trt C SEMb
13.33ax 13.03x 12.04cy 0.127
12.22by 13.62x 13.26ax 0.216
11.59cz 13.50x 12.56by 0.217
0.220 0.189 0.159
3.3. Color change and fatty acid composition The Hunter color L*-value of the patties with Trt B was higher than that of the control, Trt A (Table 3). The patties with added green tea extract powder, whether it Table 2 Radical scavenging effect (%) of raw and cooked pork patties with added nonirradiated or irradiated freeze-dried green tea leaf extract powder (0.1%) SEMa
Storage day 0
5
10
15
Raw pork patties Trt A 30.9by Trt B 58.1bx Trt C 62.0bx 1.66 SEMb
43.4aby 77.0ax 80.8ax 4.28
50.0ay 74.8ax 81.4ax 5.54
51.1ay 75.9ax 80.3ax 5.50
4.32 4.50 3.59
Cooked pork patties Trt A 26.41ay Trt B 59.86x Trt C 62.95ax SEMb 4.846
23.23ay 47.05x 43.37bx 2.668
19.26by 46.28x 30.74cx 2.576
24.59ay 51.37x 48.21bx 2.741
1.068 5.044 2.641
Trt A, only pork patties; Trt B, patties with nonirradiated, freeze-dried green tea leaf extract powder (0.1%); Trt C, patties with irradiated at 10 kGy, freeze-dried green tea leaf extract powder (0.1%). Different letters (a,b) within the same row differ (P <0.05). Different letters (x,y) within the same column with raw and cooked pork patties differ (P<0.05). a Pooled standard errors of the mean (n=6). b (n=8).
Trt A, only pork patties; Trt B, patties with nonirradiated, freeze-dried green tea leaf extract powder (0.1%); Trt C, patties with irradiated at 10 kGy, freeze-dried green tea leaf extract powder (0.1%). Different letters (a–c) within the same row differ (P<0.05). Different letters (x– z) within the same column with same color value differ (P<0.05). a Pooled standard errors of the mean (n=6). b (n=6).
Table 4 Sensory scores of raw and cooked pork patties with nonirradiated or irradiated freeze-dried green tea leaf extract powder (0.1%) Parameter
Trt A Trt B Trt C SEMb
Cookeda
Raw Color
Odor
Color
Odor
Taste
Tenderness
8.6 8.7 7.9 0.47
6.9b 5.4c 9.0a 0.90
6.78b 8.10a 8.66a 0.47
6.61 7.41 5.97 0.80
5.98 8.16 6.52 0.75
6.30 6.67 6.17 0.69
Different letters (a–c) within the same column differ (P<0.05). a Patties were cooked on a preheated pan for 3.5 min. The cooked patties were sliced into small pieces, served to the panelists individually and evaluated independently in two different times at Day 1 and Day 3. A 15 line-scale was provided to the panelists and scored; very undesirable (0) to very desirable (15) for color, strong off-odor (0) to very mild odor (15) for odor, very poor taste (0) to very tasty for taste, and very tough (0) to very tender (15) for tenderness. b Pooled standard errors of the mean (n=60).
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of the patties with added irradiated, freeze-dried green tea leaf extract powder was lower than those of the control, or that with the added nonirradiated, freezedried green tea leaf extract powder (Table 3). McCarthy et al. (2001) reported that no significant difference was found in Hunter color L*- and b*-values. The fatty acid composition of raw and cooked pork patties was not different among treatments (data not shown). 3.4. Sensory analysis No color preference was found among raw samples (Table 4). However, the panelists preferred the odor of the raw patties with the addition of irradiated, freezedried green tea extract powder (Trt C) to the control (Trt A). The pork patties with Trt B scored lowest in odor, probably because of the odor of the native green tea extracts. Surface color of cooked pork patties was scored better with Trt B and Trt C than Trt A. Odor, taste, and tenderness were not different among the samples tested. In conclusion, irradiated, freeze-dried green tea leaf extract powder did not have negative effects on physical and sensory properties. In contrast, the patties with added green tea leaf extract, both nonirradiated and irradiated, had beneficial biochemical properties. Therefore, the irradiated green tea extract powder can be used to add functional properties to the pork patties as well as functional ingredients for the cosmetic industry.
Acknowledgements This research was supported by the Nuclear R & D Program by the Ministry of Science and Technology in Korea.
References Ahn, D. U., Olson, D. G., Jo, C., Love, J., & Jin, S. K. (1999). Volatiles production and lipid oxidation on irradiated cooked sausage as related to packaging and storage. Journal of Food Science, 64, 226–229. Blois, M. S. (1958). Antioxidant determination by the use of a stable free radical. Nature, 181, 1199–1200. Byun, M. W., Son, J. H., Yook, H. S., Jo, C., & Kim, D. H. (2001). Effect of gamma irradiation on physiological activity of Korean
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soybean fermented foods, Chungkookjang and Doenjang. Radiation Physics and Chemistry, 64, 245–248. Jimenez-Colmenero, F., Carballo, J., & Cofrades, S. (2001). Healthier meat and meat products: their role as functional foods. Meat Science, 59, 5–13. Jo, C., & Ahn, D. U. (2000). Volatiles and oxidative changes in irradiated pork sausage with different fatty acid composition and tocopherol content. Journal of Food Science, 65, 270–275. Jo, C., Son, J. H., Byun, M. W. Irradiation application for color removal and purification of green tea leave extract. Radiation Physics and Chemistry (in press). Kimura, Y., Okuda, H., Okuda, T., Yoshida, T., Hatano, T., & Arichi, S. (1983). Studies on the activities of tannins and related compounds from medicinal plants and drugs. II. Effects of various tannins and related compounds on adrenaline-induced lipolysis in fat cells (1). Chemical and Pharmceutical Bulletin, 31, 2497–2500. Kingston, E. R., Monahan, F. J., Buckley, D. J., & Lynch, P. B. (1998). Lipid oxidation in cooked pork as affected by vitamin E, cooking and storage conditions. Journal of Food Science, 63, 386–389. McCarthy, T. L., Kerry, J. P., Kerry, J. F., Lynch, P. B., & Buckley, D. J. (2001). Assesment of the antioxidant potential of natural food and plant extracts in fresh and previously frozen pork patties. Meat Science, 57, 177–184. Nanjo, F., Goto, K., Seto, R., Suzuki, M., Sakai, M., & Hara, Y. (1996). Scavenging effects of tea catechins and their derivatives on 1,1-diphenyl-2-picrylhydrazyl radical. Free Radical Biolology and Medicen, 21, 895–902. Oh, D. H., Lee, M. K., & Park, B. K. (1999). Antimicrobial activities of commercially available tea on the harmful foodborne orgranisms. Journal of the Korean Society of Food Science and Nutrition, 28, 100–106. Ruan, C., Liang, Y., Liu, J., Tu, W., & Liu, Z. (1992). Antimutagenic effect of eight natural foods on molsy foods in a high liver cancer incidence area. Mutation Research, 279, 35–40. SAS Institute. (1989). SAS User’s Guide. Cary, NC. USA: SAS Institute. Son, J. H., Jo, C., Kim, M. R., Kim, J. O., & Byun, M. W. (2001). Effect of gamma irradiation on removal of undesirable color of green tea extract. Journal of Korean Society of Food Science and Nutrition, 30, 1305–1308. Stich, H. F., Chan, P. K. L., & Rosin, M. P. (1982). Inhibitory effects on phenolics, teas, and saliva on the formation of mutagenic nitrosation products of salted fish. International Journal of Cancer, 39, 719–724. Tang, S. Z., Kerry, J. P., Sheehan, D., Buckley, D. J., & Morrissey, P. A. (2001). Antioxidative effect of dietary tea catechins on lipid oxidation of long-term frozen stored chicken meat. Meat Science, 57, 331–336. Wanasundara, U. N., & Shahidi, F. (1998). Antioxidative and prooxidant activity of green tea extract in marine oils. Food Chemistry, 63, 335–342. Wang, S. M., & Zhao, J. F. (1997). Antioxidant activities of tea polyphenol on edible oil. Western Cereal and Oil Technology, 22, 44–46. Yokozawa, T., Oura, H., Sakanaka, S., Ishigaki, S., & Kim, M. (1994). Depressor effect of tannin in green tea on rats with renal hypertension. Bioscience Biotechnology Biochemistry, 58, 855.
Functional properties of raw and cooked pork patties with added irradiated, freeze-dried green tea leaf extract powder during storage at 4 C Cheorun Joa, Jun Ho Sona, Cheon Bae Sonb, Myung Woo Byuna,* a
Team for Radiation Food Science and Biotechnology, Korea Atomic Energy Research Institute, PO Box 105, Yuseong, Daejeon, 305-600, South Korea b Department of Food and Nutrition, Chungnam National University, Daejeon, 305-764, South Korea Received 25 October 2001; received in revised form and accepted 8 May 2002
Abstract Functional and sensory properties of raw and cooked pork patties with added irradiated freeze-dried green tea leaf extract powder were studied. Components of green tea were extracted by 70% ethanol, and the extract was irradiated to obtain a bright color. The irradiated green tea extract was freeze-dried and the powdered sample (0.1%) was added to the pork patties (Trt C). Pork patties without any ingredient (Trt A) and with nonirradiated, freeze-dried green tea extract powder (Trt B) were also prepared for comparison. Lipid oxidation, radical scavenging effect, color, and sensory properties of pork patties with treatments were analyzed at 5-day intervals for 15 days with storage at 4 C. The lipid oxidation had a lower (P< 0.05) and radical scavenging effect was greater (P< 0.05) in the raw and cooked pork patties with added Trt B and Trt C, than those of Trt A (control). The pork patties with Trt B and Trt C had a higher Hunter color a*-value and less cooking loss than that of Trt A. Sensory panelists preferred the odor of the raw pork patties and color of the cooked pork patties of Trt C (P <0.05). Generally, no significant difference between Trt B and Trt C was found. Therefore, irradiated, freeze-dried green tea extract powder can be used for producing functionally-improved meat products. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Green tea extract; Pork patties; Irradiation; Storage
1. Introduction In order to achieve healthier meat and meat products, two methods can be applied: avoiding undesired substances or reducing them to appropriate limits, and increasing the levels (naturally or by programmed addition) of other substances with beneficial properties (Jimenez-Colmenero, Carballo, & Cofrades, 2001). Currently, exogenous antioxidants such as phenolic compounds, tocopherols, plant derivatives and chelating agents are added to raw meat patties or cooked meat products to improve oxidative stability. Tea catechins, a predominant group of polyphenols present in green tea leaf (Camellia sinensis L.), to inhibit lipid oxidation in edible oil (Wang & Zhao, 1997) and had a greater antioxidative effect than the butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tertiary butyl hydroquinone (TBHQ), and the * Corresponding author. Tel.: +82-42-868-8060; fax: +82-42-8688043. E-mail address: [email protected] (M.W. Byun).
natural antioxidant vitamin E depending on the types and concentration of the tea catechins used (Wanasundara & Shahidi, 1998). In addition, antimutagenic activity (Ruan, Liang, Liu, Tu, & Liu, 1992; Stich, Chan, & Rosin, 1982), suppressive effect of chromosome aberration (Yokozawa, Oura, Sakanaks, Ishigaki, & Kim, 1994) or inhibitory effects on arteriosclerosis (Kimura et al., 1983) were also investigated. The components from the green tea leaf and their soluble matters have a scavenging effect on the 1,1-diphenyl-2-picrylhydrazyl radical (Nanjo et al., 1996). The antimicrobial activity of water or ethanol extracts of green tea (steamed or roasted), oolong tea, and black tea was also reported (Oh, Lee, & Park, 1999). The green tea leaf has been used mainly for drinking with boiling water, despite successful use in food or cosmetics. This is probably because of its dark red color and off-flavor, which make it very difficult to apply sufficient amount in cosmetics, medicine, or foods. Irradiation can solve these problems (Jo, Son, & Byun, in press) as it can change the color of green tea leaf extract from dark red to a slightly bright yellow by 70% ethanol extraction. These can be stored without color
0309-1740/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(02)00131-6
14
C. Jo et al. / Meat Science 64 (2003) 13–17
reversion by freeze-drying. The irradiated and powdered extract, which had improved color, was successfully applied to the cosmetic industry since the irradiation did not reduce the physiological benefits, such as the scavenging effect of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and the tyrosinase inhibitory effect (Son, Jo, Kim, Kim, & Byun, 2001). The objective of the present study is to investigate the effect of the addition of irradiated, freeze-dried green tea leaf extract powder to raw and cooked pork patties on lipid oxidation, color, sensory, and the DPPH radical scavenging effect.
2. Materials and methods 2.1. Preparation of green tea leaf extract Dried green tea leaf was purchased from the Bosung area in Chonnam, Korea, and 200 g were weighed, transferred to ethanol solution (70%, 4 l), and extracted overnight. Extraction was performed twice and the extract was divided into two groups, labeled treated by irradiation or not. 2.2. Irradiation and freeze-drying Samples in tightly capped containers (2 l) were irradiated in a cobalt-60 irradiator (point source, AECL, IR-79, Nordion, Canada) with 20 kGy absorbed doses. The source strength was approximately 100 kCi with a dose rate of 83 Gy min 1 at 15 0.5 C. Dosimetry was performed using 5 mm diameter alanine dosimeters (Bruker Instruments, Rheinstetten Germany), and the free-radical signal was measured using a Bruker EMS 104 EPR Analyzer. The actual dose was within 2% of the target dose. The sample was turned 360 continuously during the irradiation process to achieve uniform target doses and the nonirradiated control was placed outside of the irradiation chamber in order for it to have the same environmental temperature effect as the irradiating sample. Ethanol in the irradiated green tea leaf mixture was removed by laboratory evaporator (Rotary Evaporator N-11, Tokyo, Japan) immediately after irradiation and freeze-dried (SFDSF12, Samwon Co. Ltd., Pusan, Korea). The dried sample (28.3 0.11 g/100 g green tea leaf) was collected and used as an ingredient in the pork patties. 2.3. Patties preparation The longissimus dorsi muscle from pigs were obtained 24 h after slaughter from three different local meat packers, and ground twice through a 9-mm plate. Patties (approximately 100 g each) were prepared without
(Trt A) or with 0.1% freeze-dried green tea leaf extract (Trt B) and 0.1% irradiated, freeze-dried green tea leaf extract (Trt C). The prepared raw pork patties were packaged in oxygen permeable polyethylene and stored for 15 days at 4 C. 2.4. Color measurement The patty was placed on the plate of a Color Difference Meter (Spectrophotometer CM-3500d, Minolta Co., Ltd. Osaka, Japan) and measured. The instrument was calibrated to standard black and white tiles before analysis. Four different areas of patty per treatment were evaluated and mean values were used for replication. A medium size aperture was used and the measurement was duplicated. The Hunter color L*-, a*-, and b*-values were reported through the computerized system using Spectra Magic software (version 2.11, Minolta Cyberchrom Inc. Osaka, Japan). 2.5. Scavenging effects of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The sample (2 g) was transferred to a 20 ml-test tube and homogenized (DIAX 900, Heidolph Co., Ltd., Germany) for 15 s at speed setting 6 (approximately 23,000 rpm) with 8 ml of deionized distilled water (DDW). The mixture was filtered by a filter paper (No. 4., Whatman International Ltd., Springfield Mill, Maidstone, Kent, England) and chloroform (2 ml) was added into the filterate. The tube with filterate was vortexed vigorously to remove any fat in the sample and centrifuged (VS 5500, Vision Scientific Co., Ltd. Bucheon, Korea) at 2400 rpm for 30 min. The upper layer of the mixture was diluted 5 times with DDW, and the free radical scavenging effect was estimated according to the method of Blois (1958) with some modification. A sample (1 ml) was added into the 0.2 mM DPPH radical (1 ml). The mixture was shaken and left to stand for 30 min at room temperature and measured at 517 nm with a spectrophotometer. 2.6. Lipid oxidation, fatty acid composition, and sensory analysis Lipid oxidation was determined as a 2-thiobarbituric acid reactive substances (TBARS) value by using a spectrophotometer (UV 1600 PC, Shimadzu, Tokyo, Japan) as described by Ahn, Olson, Jo, Love, and Jin (1999). The lipid oxidation development was reported as mg malondialdehyde/kg meat sample. Fatty acid composition was analyzed by the method of Jo and Ahn (2000) using a gas chromatograph (GC, Model 6890, Agillent Tehcnologies Inc., Palo Alto, CA) equipped with a flame ionization detector (FID). A split inlet (split ratio, 20:1) was used to inject samples into a
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capillary column (DB Wax, 60 m250 mm0.25 mm nominated, J&W Scientific Inc., Folsom, CA) and ramped oven temperature was used (180C for 5 min, increased to 220 C at 2.5 C/min, kept constant for 20 min). Injection was achieved by an Agillent Model 7683 injector (Agillent Technologies, Inc.). Inlet and detector temperature were 210 C. Nitrogen was the carrier gas at constant flow of 1.1 ml/min. Detector air, N2, and make-up gas (N2) flows were 300, 30, and 28 ml/min, respectively. The obtained chromatogram was integrated using a GC Chemstation software (Rev. A.08.03, Agillent Technologies, Inc.). Trained panelists (n=10) were used to evaluate sensory properties of the raw and cooked pork patties. A patty was placed on a preheated pan at about 170 C and pressed after 30 s. After 1.5 min, the patty was turned over and left for another 1.5 min. The temperature of the center of patty reached approximately 78 C. Average pan temperature during cooking was 160 C. After cooling for 2 min at room temperature, the patties were sliced into four similar pieces and served to the panelists individually. The sensory parameters for the raw patties were color and odor, and for the cooked patties, color, odor, taste, and tenderness were evaluated independently by the panelists on each of the three different occasions. A 15 cm line-scale was provided to the panelists and it was anchored as follows; very undesirable (0) to very desirable (15) for color, strong off-odor (0) to very mild odor (15) for odor, very poor taste (0) to excellent (15) for taste, and very tough (0) to very tender (15) for tenderness. 2.7. Statistical analysis The experimental design used was a 3 treatments 3 storage factorial and the whole experiment was duplicated. Two-way Analyses of Variance was performed using SAS software (SAS Institute, 1989) and the Student–Newman–Keul’s multiple range test was used to compare differences among mean values. Mean values and pooled standard errors of the mean (SEM) were reported, and the significance was defined at P < 0.05.
3. Results and discussion 3.1. Lipid oxidation The TBARS value of the raw pork patties increased during 15 days of storage in all treatments; however, the TBARS values of the patties with added freeze-dried green tea leaf extract powder (0.1%) were significantly lower than those of the control, Trt A (Table 1). There was no significant difference between irradiation and nonirradiation treatment to the green tea leaf extract. McCarthy, Kerry, Kerry, Lynch, and Buckley (2001)
Table 1 TBARS values (mg malondialdehyde/kg meat) of raw and cooked pork patties with added nonirradiated or irradiated freeze-dried green tea leaf extract powder (0.1%) SEMa
Storage day 0
5
10
15
Raw pork patties Trt A 0.38cx Trt B 0.28by Trt C 0.30by 0.021 SEMb
0.56bx 0.42ay 0.36az 0.016
0.56bx 0.43ay 0.35ay 0.025
0.69ax 0.48ay 0.39ay 0.028
0.029 0.024 0.016
Cooked pork patties Trt A 1.13bx Trt B 0.48z Trt C 0.58ay SEMb 0.027
1.22abx 0.42y 0.36by 0.048
1.38ax 0.42y 0.44by 0.043
1.21abx 0.44y 0.31by 0.048
0.044 0.042 0.042
Trt A, only pork patties; Trt B, patties with nonirradiated, freeze-dried green tea leaf extract powder (0.1%); Trt C, patties with irradiated at 10 kGy, freeze-dried green tea leaf extract powder (0.1%). Different letters (a–c) within the same row differ (P<0.05). Different letters (x– z) within the same column with raw and cooked pork patties differ (P<0.05). a Pooled standard errors of the mean (n=6). b (n=8).
reported that tea catechins were the most effective in reducing lipid oxidation in fresh or frozen pork patties among nine natural antioxidants used. Cooked meat is more susceptible to lipid oxidation than raw meat during refrigerated and frozen storage due to the fact that heating accelerates oxidative reactions with the lipid in meat (Kingston, Monahan, Buckley, & Lynch, 1998). In cooked pork patties, the TBARS values of the control significantly increased compared to the raw pork patties but both patties treated with freeze-dried green tea extract powder, Trt B and Trt C, maintained almost the same values as the raw pork patties except for at day 0 (P < 0.05). It is indicated that the added green tea extract powder significantly reduced the lipid oxidation development of the pork patties. There was no difference found in the lipid oxidation of patties between Trt B and Trt C. Tang, Kerry, Sheehan, Buckley, and Morrissey (2001) reported that dietary tea catechin supplementation to chicken at 50–300 mg/kg feed, showed antioxidative effects for both the breast and thigh meat during 10 days of refrigerated and 9 months of frozen storage. Furthermore, McCarthy et al. (2001) concluded that the tea catechin was the most effective antioxidant in raw and cooked pork patties among the natural food/plant extract or synthetic antioxidants. 3.2. Scavenging effects of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The radical scavenging effect in raw pork patties with Trt A was 30.9%, but 58.1 and 62.0% in the patties
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with added Trt B or Trt C (Table 2). The addition of green tea leaf extract powder significantly increased the radical scavenging effect of raw pork patties but no difference was found between irradiation treatments to the extract. The radical scavenging effect was significantly reduced (P < 0.05) by the cooking of the raw pork patties (Table 2). The cooked pork patties with control (Trt A) was 19.26–26.41% of radical scavenging during storage without significant changes. However, the cooked pork patties with Trt B had a higher radical scavenging effect than that with Trt A. The radical scavenging effect of pork patties with Trt C was also higher than that with Trt A. Between the patties with added nonirradiated and irradiated green tea extract powder (Trt B and Trt C), there was no difference found. Byun, Son, Yook, Jo, and Kim (2001) reported that 5, 10 and 20 kGy of irradiation to Korean traditional soybean-based fermented food, Chungkookjang and Doenjang, did not change physiological activities such as angiotensin converting enzyme inhibition, xanthine oxidase inhibition, tyrosinase inhibition, as well as radical scavenging ability. Son et al. (2001) and Jo et al. (in press) also concluded that irradiation technology can enhance the color of green tea leaf extract without any adverse change in physiological activities.
was irradiated or not, had a generally higher Hunter color L*-value. The a*-value was higher in the patties without green tea extract powder at Day 0, but during storage the patties with added green tea extract powder had a higher a-value than that of the control (Table 3). In a comparative study of McCarthy et al. (2001), butylated hydroxyanisol/butylated hydroxytoluene (BHA/BHT, 0.01%) was the most effective for preserving the meat redness of pork patties among 11 test food ingredients with optimum concentrations. In the same study, the pork patties with tea catechin (0.25%) also had a higher Hunter color a*-value than that of the control from the beginning. The Hunter color b*-value Table 3 Color changes of raw pork patties added with nonirradiated or irradiated green tea leaf extract powder (0.1%) Treatment
0
5
10
SEMa
L*
Trt A Trt B Trt C SEMb
53.13y 56.04x 54.44bxy 0.684
55.37y 56.42ay 57.96ax 0.666
54.16y 56.03x 57.10ax 0.473
0.591 0.710 0.530
a*
Trt A Trt B Trt C SEMb
4.84ax 4.39ax 4.34ay 0.280
4.15b 4.24a 4.36a 0.289
3.08cy 3.68bx 3.89bx 0.179
0.242 0.277 0.159
b*
Trt A Trt B Trt C SEMb
13.33ax 13.03x 12.04cy 0.127
12.22by 13.62x 13.26ax 0.216
11.59cz 13.50x 12.56by 0.217
0.220 0.189 0.159
3.3. Color change and fatty acid composition The Hunter color L*-value of the patties with Trt B was higher than that of the control, Trt A (Table 3). The patties with added green tea extract powder, whether it Table 2 Radical scavenging effect (%) of raw and cooked pork patties with added nonirradiated or irradiated freeze-dried green tea leaf extract powder (0.1%) SEMa
Storage day 0
5
10
15
Raw pork patties Trt A 30.9by Trt B 58.1bx Trt C 62.0bx 1.66 SEMb
43.4aby 77.0ax 80.8ax 4.28
50.0ay 74.8ax 81.4ax 5.54
51.1ay 75.9ax 80.3ax 5.50
4.32 4.50 3.59
Cooked pork patties Trt A 26.41ay Trt B 59.86x Trt C 62.95ax SEMb 4.846
23.23ay 47.05x 43.37bx 2.668
19.26by 46.28x 30.74cx 2.576
24.59ay 51.37x 48.21bx 2.741
1.068 5.044 2.641
Trt A, only pork patties; Trt B, patties with nonirradiated, freeze-dried green tea leaf extract powder (0.1%); Trt C, patties with irradiated at 10 kGy, freeze-dried green tea leaf extract powder (0.1%). Different letters (a,b) within the same row differ (P <0.05). Different letters (x,y) within the same column with raw and cooked pork patties differ (P<0.05). a Pooled standard errors of the mean (n=6). b (n=8).
Trt A, only pork patties; Trt B, patties with nonirradiated, freeze-dried green tea leaf extract powder (0.1%); Trt C, patties with irradiated at 10 kGy, freeze-dried green tea leaf extract powder (0.1%). Different letters (a–c) within the same row differ (P<0.05). Different letters (x– z) within the same column with same color value differ (P<0.05). a Pooled standard errors of the mean (n=6). b (n=6).
Table 4 Sensory scores of raw and cooked pork patties with nonirradiated or irradiated freeze-dried green tea leaf extract powder (0.1%) Parameter
Trt A Trt B Trt C SEMb
Cookeda
Raw Color
Odor
Color
Odor
Taste
Tenderness
8.6 8.7 7.9 0.47
6.9b 5.4c 9.0a 0.90
6.78b 8.10a 8.66a 0.47
6.61 7.41 5.97 0.80
5.98 8.16 6.52 0.75
6.30 6.67 6.17 0.69
Different letters (a–c) within the same column differ (P<0.05). a Patties were cooked on a preheated pan for 3.5 min. The cooked patties were sliced into small pieces, served to the panelists individually and evaluated independently in two different times at Day 1 and Day 3. A 15 line-scale was provided to the panelists and scored; very undesirable (0) to very desirable (15) for color, strong off-odor (0) to very mild odor (15) for odor, very poor taste (0) to very tasty for taste, and very tough (0) to very tender (15) for tenderness. b Pooled standard errors of the mean (n=60).
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of the patties with added irradiated, freeze-dried green tea leaf extract powder was lower than those of the control, or that with the added nonirradiated, freezedried green tea leaf extract powder (Table 3). McCarthy et al. (2001) reported that no significant difference was found in Hunter color L*- and b*-values. The fatty acid composition of raw and cooked pork patties was not different among treatments (data not shown). 3.4. Sensory analysis No color preference was found among raw samples (Table 4). However, the panelists preferred the odor of the raw patties with the addition of irradiated, freezedried green tea extract powder (Trt C) to the control (Trt A). The pork patties with Trt B scored lowest in odor, probably because of the odor of the native green tea extracts. Surface color of cooked pork patties was scored better with Trt B and Trt C than Trt A. Odor, taste, and tenderness were not different among the samples tested. In conclusion, irradiated, freeze-dried green tea leaf extract powder did not have negative effects on physical and sensory properties. In contrast, the patties with added green tea leaf extract, both nonirradiated and irradiated, had beneficial biochemical properties. Therefore, the irradiated green tea extract powder can be used to add functional properties to the pork patties as well as functional ingredients for the cosmetic industry.
Acknowledgements This research was supported by the Nuclear R & D Program by the Ministry of Science and Technology in Korea.
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