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Effect of dietary tea catechins supplementation in goats on the quality of meat kept under refrigeration
Small Ruminant Research 87 (2009) 122–125
Contents lists available at ScienceDirect
Small Ruminant Research journal homepage: www.elsevier.com/locate/smallrumres
Short communication
Effect of dietary tea catechins supplementation in goats on the quality of meat kept under refrigeration R.Z. Zhong a,b , C.Y. Tan a , X.F. Han a , S.X. Tang a , Z.L. Tan a,∗ , B. Zeng a a
Key Laboratory of Agro-ecological Process of Subtropical Region, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, Hunan 410125, PR China b Graduate University of the Chinese Academy of Sciences, Beijing 100039, PR China
a r t i c l e
i n f o
Article history: Received 23 July 2009 Received in revised form 19 October 2009 Accepted 19 October 2009 Available online 14 November 2009 Keywords: Tea catechins Antioxidant Meat quality Goats
a b s t r a c t Liuyang black male goats were used to examine the effects of TC inclusion on lipid oxidation and fresh meat quality of goats. Forty goats were randomly divided into four equal groups (ten animals in each group) and assigned to four experiment diets with TC supplementation at four levels (0, 2000, 3000 and 4000 mg TC/kg feed). After 60 days of feeding period, all goats were slaughtered and sampled. The results showed that dietary TC supplementation had significant (P < 0.05) effect on plasma total antioxidant status (TAS) at days 40 and 60, lipid oxidation of M. longissimus dorsi (LD), gluteus medius (GM) and semimemberanosus (SM), pH value of GM and SM at 24 h postmortem, intramuscular fat (IMF) of SM, drip loss percentage of GM and SM, and total haem pigment content (THP) of LD and SM. In conclusion, suitable dietary TC level could inhibit lipid oxidation, decrease drip loss of fresh meat and improve meat colour stability in goat, moreover, dietary TC inclusion influences muscle pH values and IMF at some degree, but different muscle types showed different trend to change, and the quality of LD was relatively stable according to overall evaluation. © 2009 Elsevier B.V. All rights reserved.
1. Introduction The palatability of chevon, as well as its tenderness, protein content, colour stability and shelf life, is valued by consumers. It is now commonly recognized that lipid oxidation is responsible for the decline of meat quality. It occurs during processing and storage of meat production. Lipid oxidation in meat results in a variety of breakdown of products which leads to discoloration, drip loss, offodour, off-flavour, and even changes the nutritive value and reduces shelf life (Nissen et al., 2000). It is therefore necessary to control this change for better meat product development.
∗ Corresponding author at: Institute of Subtropical Agriculture, The Chinese Academy of Sciences, PO Box 10, Changsha, Hunan 410125, PR China. Tel.: +86 731 4619702; fax: +86 731 4612685. E-mail address: [email protected] (Z.L. Tan). 0921-4488/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2009.10.012
Lipid oxidation mainly caused by reactive oxygen species (ROS) is defined as “a disturbance in prooxidant–antioxidant balance in favour of the former, leading to potential damage”. Living cell has several mechanisms to protect against oxidative process, including the endogenous enzymes superoxide dismutase (SOD), catalase (Cat) and glutathione peroxidase (GSH-Px). Besides the protection of endogenous enzymes, the oxidative stability of meat is determined by the presence of some exogenous low-molecular-mass antioxidants, e.g. the role of vitamin E in retarding lipid oxidation and improving colour stability is well recognized. Therefore, some synthetic phenolic antioxidants are easily available and largely used in food production. However, these synthetic antioxidants have been reported to have carcinogenic potential risks. In line with these evidences, the growing interest about natural antioxidants, such as polyphenols or flavonoids, has fostered research on inhibition of lipid oxidation and oxidative stress (Sánchez-Escalante et al., 2003)
R.Z. Zhong et al. / Small Ruminant Research 87 (2009) 122–125 Table 1 Ingredients and chemical composition of basal experimental diet. Ingredient (% DM) Maize stover Ground corn Soybean meal Wheat bran Urea Calcium carbonate Calcium bicarbonate Sodium chloride Minerals and vitamins salta
Chemical composition 45 25 15 11.2 0.2 0.9 0.6 0.6 1.5
DM (%) OM (% DM) ME (Mcal kg−1 DM)b CP (% DM) NDF (% DM) ADF (% DM) Ca (% DM) Total P (% DM)
89.8 92.7 2.75 12.3 36.7 24.2 0.92 0.74
a Contained per kg: 227 g MgSO4 ·H2 O, 12.5 g FeSO4 ·7H2 O, 2.8 g CuSO4 ·5H2 O, 12.2 g MnSO4 ·H2 O, 13.4 g ZnSO4 ·H2 O, 20 mg Na2 SeO3 , 50 mg KI, 35 mg CoCl2 ·6H2 O, 90,000 IU vitamin A, 17,000 IU vitamin D, and 17,500 IU vitamin E. b Metabolic energy was calculated according to NRC (1981).
Tea catechins (TC), a predominant group of polyphenols present in green tea leaves (Camellia sinensis L.), comprise mainly four compounds namely (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), and (−)-epigallocatechin gallate (EGCG). The antioxidative properties of dietary TC supplementation have already been studied in human, rats, beef cattle, chicken and pig using in vivo or in vitro experiments, however, few data are available on its antioxidative properties and meat quality in goats. The objectives of current study were to investigate the antioxidant properties of different levels of dietary TC supplementation against lipid oxidation, and to assess the effect of dietary TC supplementation on meat quality traits of growing goats. 2. Materials and methods The experiment was conducted according to the animal care and the use guidelines of the Animal Care Committee, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China.
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2.3. Blood sampling and slaughtering procedure At days 0, 20, 40 and 60 of the trial period, blood samples (20 mL) were taken from the jugular vein of each goat at 06:00 and 10:00 h into Li-heparin treated tubes to obtain blood plasma. Blood samples were centrifuged using centrifuge (Himac CR22G2, Hitachi Koki Co., Ltd) at 3000 rpm for 15 min at 4 ◦ C to harvest plasma. Thereafter, samples were stored at −20 ◦ C until analysis of plasma total antioxidant status (TAS). At the end of 60 days of feeding period, all goats were weighed and humanely slaughtered in line with the approved commercial procedures by the animal ethic committee of Institute of Subtropical Agriculture. The animals were allowed to bleed after which their bodies were hung to remove the skin, head, fore feet, hind feet, gastrointestinal tract and viscera organs. The left side of carcass was kept under aseptic condition at 4 ◦ C for meat quality determination. Muscles were removed from left side of the carcass and all external fat and connective tissue were also removed within 24 h postmortem. About 200 g each of left M. longissimus dorsi (LD), gluteus medius (GM) and semimemberanosus (SM) muscles were sampled. 50 g each of sampled muscles were ice-dried for analysis of intramuscular fat (IMF) while another 50 g each of muscles were cut into small slices (1 cm in width × 1 cm in length), vacuum packaged and stored at 4 ◦ C dark for the measurement of total haem pigment content (THP) and thiobarbituric acid reactive substances (TBARS). About 80 g each of muscles samples were further taken and cut into small slices (3 cm in width × 10 cm in length), before hanging them in an icebox at 4 ◦ C under aseptic condition for the determination of drip loss. Another 20 g muscle samples were kept at 4 ◦ C under aseptic condition for 24 h to assay muscle pH value. 2.4. Analytical procedure Plasma TAS was measured using a commercially available TAS kit (Total Antioxidant Status, Jiancheng Biology Co., Nanjing, China) according to the manufacturer’s instructions. Lipid oxidation of LD, GM and SM samples were measured on day 0, 2, 4, 6 and 8 of postmortem aging according to TBARS by the modified method of Olsvik et al. (2005). Drip loss percentage was measured by hanging slices in sealed aseptic polythene bags at days 2, 4, 6 and 8 of postmortem aging, and expressed as the loss weight proportion to the original weight. Samples of LD, GM and SM (10 g) at 24 h postmortem were homogenized (1 min, 24,000 rpm) in 100 mL of ice phosphate buffer solution (pH 7.0) using Power Gen Model 125 homogenizer (Fisher Scientific, Beijing, China). The pH value of the homogenate was measured at 20 ◦ C using a pH meter (6250 membrane pH meter, Yibo Instruments Co., Shanghai, China). The IMF content of LD, GM and SM were evaluated using the method of ether extraction on Sohxtex (AOAC, 1990). The THP of LD, GM and SM on days 0, 1, 3, 5 and 7 postmortem were measured according to the method of Ockerman (1985).
2.1. Tea catechins preparation 2.5. Statistical analysis The TC (purity of 80.86%) was extracted from green tea leaves (C. sinensis L.) by using high pressure liquid chromatography (HPLC) (Model Waters600, Waters Co., Milford, USA). The extracted TC contained caffeine (0.75%), (+)-catechin and (−)-catechin (DL-C) (1.61%), EC (5.77%), EGC (0.47%), ECG (13.03%), (−)-gallocatechin gallate (GCG) (1.56%) and EGCG (57.67%), respectively.
2.2. Experimental design, animal management and diets Forty Liuyang black male goats (a local breed) with average age of 8 months ± 10 days, average initial body weight of 16.2 ± 1.2 kg and same genetic background were randomly divided into four equal groups (ten animals in each group) and assigned to four experiment diets for 60 days of feeding trial. The control group (TC0) was fed basal diet without TC supplementation. The other three groups were fed basal diet with dietary TC supplementation at levels of 2000 (TC2000), 3000 (TC3000) and 4000 (TC4000) mg TC/kg feed (on DM basis). The ingredients and chemical composition of basal diet are shown in Table 1. All goats were castrated surgically before the commencement of the trial, and then allowed a recovery period of two weeks. During feeding period, each kid was fed twice daily (08:00 and 20:00 h) with 578 g feed each day (on DM basis) and recorded the orts daily. Each goat was assigned to single finishing barn with average temperature of 24 ± 1 ◦ C and free access to fresh water. After 60 days of feeding period, all goats were humanely slaughtered and samples collected.
All data were subjected to analysis of variance (ANOVA) using the generalized linear model procedure of SAS (2002). The main effect tested was the TC supplementation level for all variables. The following statistical model was used for data analysis, which had repeated measure over time.
Yij = m + Ti + Dj + Ti × Dj + eij where Yij is dependent variables, is the overall mean, Ti is the effect of treatment (i = 1, 2, 3, 4), Dj is the effect of aging time as repeated measure (j = 1, 2, 3, 4, 5) for pH value, IMF, TBARS, drip loss and THP of individual muscles or the effect of feeding period as repeated measure (j = 1, 2, 3, 4) for plasma TAS, Ti × Dj is the interaction between Ti and Dj and eij is the random residual error. Where the effects of treatment were significant, differences among means were tested with Duncan’s multiple range tests. Statistical significance was declared at P ≤ 0.05.
3. Results and discussion Supplementation of TC had significant effect (P < 0.05) on plasma TAS at days 40 and 60. Plasma TAS decreased with the feeding time extension, but dietary TC treatments still had higher values than that of TC0 (Table 2). Plasma
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R.Z. Zhong et al. / Small Ruminant Research 87 (2009) 122–125
Table 2 Effect of dietary tea catechin (TC) supplementation on plasma total antioxidant status (TAS, U/mL). Feeding period (days)
0 20 40 60
Treatment TC0
TC2000
TC3000
TC4000
5.15 4.15 3.69a 2.80b
5.23 3.74 3.05b 3.05ab
5.32 3.78 3.06b 3.10ab
5.36 3.58 3.48ab 3.16a
SEMe
TC effect (P value) Linear
Quadratic
Cubic
0.533 0.324 0.267 0.182
NS NS NS
NS NS
NS NS NS NS
*
*
NS
a,b,c,d
Mean values followed by different superscripts in the same row differ significantly (P < 0.05). NS, not significant. * P < 0.05. e SEM = standard error of mean.
TAS is a useful indicator of the fate of antioxidant supplement in animal diets. A condition of decreased TAS has been attributed to antioxidant enzymes, in which their effects are exerted in dose and time-dependent manner (Granado-Serrano et al., 2009). The current results showed that plasma TAS of goats increased with increasing dietary TC supplementation at long term TC feeding. This observation is an indication that TC supplementation can protect ruminants against oxidation stress under suitable feeding condition. Supplementation using TC had significant linear effect (P < 0.01) on TBARS values of LD, GM and SM. Generally, the muscle TBARS values of all the groups fed TC showed sharp increasing trends than control group. Moreover, the effect showed dose-dependent manner, and TC4000 treatment had lowest TBARS among all four groups (Table 3). Malondialdehyde, a secondary product of lipid oxidation, is known to be toxic and carcinogenic in human. Hashimoto et al.
(1999) elucidated that the TC could protect phospholipids bilayers and low-density lipoprotein against lipid oxidation. During the last decade, many studies have emphasized the tea catechins’ function of inhibiting lipid oxidation in chicken meat and in raw red meat. Although some studies have reported no effect of TC supplementation on lipid oxidation of beef, our results have shown that TC could improve lipid stability of fresh meat of goats kept under refrigeration. Drip loss of LD showed no significantly change with TC supplementation, while that of GM decreased significantly (P < 0.05). For SM, its drip loss was significantly linear (P < 0.05), and TC4000 had the lowest value than the other groups (Table 3). In this trial, increased value of drip loss might be closely related to lipid oxidation, while this effect might be due to dietary TC supplementation in decreasing lipid oxidation, enhancing integrity of cellular membrane and consequently improving the water holding ability of
Table 3 Effect of dietary tea catechin (TC) supplementation on TBARS, drip loss, total haem pigment content (THP), pH value and intramuscular fat (IMF) and of M. longissimus dorsi (LD), gluteus medius (GM) and semimemberanosus (SM). Muscle
SEMe
Treatment TC0
TC2000
TC3000
TC4000
TBARS (g MDA/g meat) LD 1.71a GM 1.75a SM 1.91a
1.35b 1.54b 1.85a
1.01c 1.13c 1.54b
1.05c 1.05d 1.42c
0.020 0.017 0.033
Drip loss (%) LD GM SM
2.07 1.67ab 2.13a
2.09 1.41b 1.98a
2.09 1.48ab 1.57b
0.146 0.126 0.106
2.00 1.84a 1.95a
THP (g/g meat) LD 138.7b GM 168.2 SM 138.4b pH of 24 postmortem LD 5.39 GM 5.37b SM 5.37a IMF (g/kg) LD GM SM a,b,c,d
98.3 106.6 96.1a
139.8b 180.1 158.2a 5.35 5.47a 5.37a 121.2 126.6 93.6a
138.9b 184.7 137.3b 5.32 5.33b 5.29b 101.0 120.7 73.3b
155.1a 172.9 153.5a 5.34 5.36ab 5.34ab 115.5 92.2 89.6a
TC effect (P value) Linear
Quadratic
Cubic
**
**
**
**
**
**
**
**
**
NS
NS NS
NS NS NS
* *
**
3.906 5.933 4.963
*
*
NS NS
NS NS
0.033 0.032 0.021
NS NS NS
NS NS NS
1.266 1.074 0.468
NS NS NS
NS NS NS
Mean values followed by different superscripts in the same row differ significantly (P < 0.05). NS, not significant. * P < 0.05. ** P < 0.01. e SEM = standard error of mean.
NS NS **
NS * *
NS NS **
R.Z. Zhong et al. / Small Ruminant Research 87 (2009) 122–125
meat. One interesting finding was that drip loss of LD was not affected by TC supplementation, and the reason for this should be further studied. Supplementation of TC had significant linear effect on THP content of LD (P < 0.05) and cubic effect on SM (P < 0.01). As a whole, the THP of LD in TC4000 group had highest value than that of other treatments, while the THP content of SM in TC2000 and TC4000 treatments showed higher value than the other two groups (Table 3). For red meat, the colour is determined by the amount of haem pigment and myoglobin. It has been established that meat colour and lipid oxidation are negatively correlated. In the present study, the reason for improved pigment stability of muscle might be linked to the retardation of lipid, protein and myoglobin oxidation in meat because of the addition of TC. The TC supplementation had no significant effect on pH value of LD, but had significant cubic effect (P < 0.05) on pH values of GM and SM. As a whole, muscle pH values of all the TC supplementation groups were lower than that of control except pH value of GM in TC2000 group (Table 3). The ultimate pH value of postmortem muscle can be correlated with meat tenderness. Many studies have reported the curvilinear relationship between tenderness and ultimate pH value of meat, and the optimum tenderness occurred at approximately pH value of 6 in beef cattle. Our study has provided valid evidence that dietary TC affected the ultimate pH value of postmortem muscle of goats. Variations in ultimate pH value for different types for goat’s muscle in the present study were similar to those reported by Kadim et al. (2003). Dietary TC supplementation had no significant effect on IMF of LD and GM, but IMF of SM was affected cubically (P < 0.01). For LD, TC2000 was found highest among all groups. For GM, TC2000 and TC3000 groups had numerically higher IMF, but TC4000 group had lower IMF than that of control group. For SM, supplementation of TC insignificantly decreased IMF with TC3000 group being the lowest (Table 3). Intramuscular fat content is positively correlated with the tenderness, juiciness and taste of meat. Though IMF is a stable index mainly affected by genetic factors, some studies have also reported different observations on the relationship between supplementation of antioxidant and IMF deposition (Nade et al., 2003). Our results indicated that dietary antioxidant is not the main factor in determining IMF percentage. Detailed of the physiological mechanism involved in this should be further investigated. 4. Conclusion This work showed that TC is a promising natural antioxidant to improve meat quality in goats. TC acts
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as antioxidant to modulate TAS of organisms, enhance integrity of cellular membrane, improved fresh meat colour stability and decreased TBARS and drip loss consequently. Although TC supplementation had significant influence on muscle pH of SM and IMF of GM and SM, but different muscle types showed different trends to change, and the quality of LD was relative stable according to overall evaluation. Another interesting finding was that the effect of TC supplementation is dose and feeding period dependent. Feeding period of 40–60 days and supplementation dose of 3000–4000 mg TC/kg feed have better effects in goats. Acknowledgement We would like to express our sincere gratitude and appreciation to the Ministry of Science and Technology of China (2006BAD04A15) for providing the financial support for this study. References AOAC (Association of Official Analytical Chemists), 1990. Official Methods of Analysis, vol. 2., 5th ed. Association of Official Analytical Chemist, Washington, DC, USA, Arlington, Virginia. Granado-Serrano, A.B., Martín, M.A., Goya, L., Bravo, L., Ramos, S., 2009. Time-course regulation of survival pathways by epicatechin on HepG2 cells. J. Nutr. Biochem. 20, 115–124. Hashimoto, T., Kumazawa, S., Nanjo, F., Hara, Y., Nakayama, T., 1999. Interaction of tea catechins with lipid bilayers investigated with liposome systems. Biosci. Biotechnol. Biochem. 63, 2252–2255. Kadim, I.T., Mahgoub, O., Al-Ajmi, D.S., Al-Maqbaly, R.S., Al-Saqri, N.M., Ritchie, A., 2003. An evaluation of the growth, carcass and meat quality characteristics of Omani goat breeds. Meat Sci. 66, 203– 210. Nade, T., Hirabara, S., Okumura, T., Fujita, K., 2003. Effects of vitamin A on carcass composition concerning younger steers fattening of Wagyu cattle. Asian-Aust. J. Anim. Sci. 16, 353–358. Nissen, H., Alvseike, O., Bredholt, S., Holck, A., Nesbakken, T., 2000. Comparison between the growth of Yersinia enterocolitica, Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp. in ground beef packed by three commercially used packaging techniques. Int J. Food Microbiol. 59, 211–220. NRC, Nurient Requirements of Goats: Angora, 1981. Dairy and Meat Goats in Temperate and Tropical Countries. National Academy Press, Washington DC, USA, 110–115 pp. Ockerman, H.W., 1985. Quality Control of Post-Mortem Muscle Tissue. Department of Animal Sciences, The Ohio State University, Columbus, OH, USA. Olsvik, P.A., Kristensen, T., Waagbø, R., Rosseland, B.O., Tollefsen, K.E., Baeverfjord, G., Berntssen, M.H.G., 2005. mRNA expression of antioxidant enzymes (SOD, Cat and GSH-Px) and lipid peroxidative stress in liver of Atlantic salmon (Salmo salar) exposed to hyperoxic water during smoltification. Comp. Biochem. Physiol. 141, 314– 323. SAS, 2002. SAS/STAT® User’s Guide: Statistics. Version 9.1 Edition. SAS Inc., Cary, NC, USA. Sánchez-Escalante, A., Djenane, D., Torrescano, G., Beltrán, J.A., Roncalés, P., 2003. Antioxidant action of borage, rosemary, oregano, and ascorbic acid in beef patties packaged in modified atmosphere. J. Food Sci. 68, 339–344.
Contents lists available at ScienceDirect
Small Ruminant Research journal homepage: www.elsevier.com/locate/smallrumres
Short communication
Effect of dietary tea catechins supplementation in goats on the quality of meat kept under refrigeration R.Z. Zhong a,b , C.Y. Tan a , X.F. Han a , S.X. Tang a , Z.L. Tan a,∗ , B. Zeng a a
Key Laboratory of Agro-ecological Process of Subtropical Region, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, Hunan 410125, PR China b Graduate University of the Chinese Academy of Sciences, Beijing 100039, PR China
a r t i c l e
i n f o
Article history: Received 23 July 2009 Received in revised form 19 October 2009 Accepted 19 October 2009 Available online 14 November 2009 Keywords: Tea catechins Antioxidant Meat quality Goats
a b s t r a c t Liuyang black male goats were used to examine the effects of TC inclusion on lipid oxidation and fresh meat quality of goats. Forty goats were randomly divided into four equal groups (ten animals in each group) and assigned to four experiment diets with TC supplementation at four levels (0, 2000, 3000 and 4000 mg TC/kg feed). After 60 days of feeding period, all goats were slaughtered and sampled. The results showed that dietary TC supplementation had significant (P < 0.05) effect on plasma total antioxidant status (TAS) at days 40 and 60, lipid oxidation of M. longissimus dorsi (LD), gluteus medius (GM) and semimemberanosus (SM), pH value of GM and SM at 24 h postmortem, intramuscular fat (IMF) of SM, drip loss percentage of GM and SM, and total haem pigment content (THP) of LD and SM. In conclusion, suitable dietary TC level could inhibit lipid oxidation, decrease drip loss of fresh meat and improve meat colour stability in goat, moreover, dietary TC inclusion influences muscle pH values and IMF at some degree, but different muscle types showed different trend to change, and the quality of LD was relatively stable according to overall evaluation. © 2009 Elsevier B.V. All rights reserved.
1. Introduction The palatability of chevon, as well as its tenderness, protein content, colour stability and shelf life, is valued by consumers. It is now commonly recognized that lipid oxidation is responsible for the decline of meat quality. It occurs during processing and storage of meat production. Lipid oxidation in meat results in a variety of breakdown of products which leads to discoloration, drip loss, offodour, off-flavour, and even changes the nutritive value and reduces shelf life (Nissen et al., 2000). It is therefore necessary to control this change for better meat product development.
∗ Corresponding author at: Institute of Subtropical Agriculture, The Chinese Academy of Sciences, PO Box 10, Changsha, Hunan 410125, PR China. Tel.: +86 731 4619702; fax: +86 731 4612685. E-mail address: [email protected] (Z.L. Tan). 0921-4488/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2009.10.012
Lipid oxidation mainly caused by reactive oxygen species (ROS) is defined as “a disturbance in prooxidant–antioxidant balance in favour of the former, leading to potential damage”. Living cell has several mechanisms to protect against oxidative process, including the endogenous enzymes superoxide dismutase (SOD), catalase (Cat) and glutathione peroxidase (GSH-Px). Besides the protection of endogenous enzymes, the oxidative stability of meat is determined by the presence of some exogenous low-molecular-mass antioxidants, e.g. the role of vitamin E in retarding lipid oxidation and improving colour stability is well recognized. Therefore, some synthetic phenolic antioxidants are easily available and largely used in food production. However, these synthetic antioxidants have been reported to have carcinogenic potential risks. In line with these evidences, the growing interest about natural antioxidants, such as polyphenols or flavonoids, has fostered research on inhibition of lipid oxidation and oxidative stress (Sánchez-Escalante et al., 2003)
R.Z. Zhong et al. / Small Ruminant Research 87 (2009) 122–125 Table 1 Ingredients and chemical composition of basal experimental diet. Ingredient (% DM) Maize stover Ground corn Soybean meal Wheat bran Urea Calcium carbonate Calcium bicarbonate Sodium chloride Minerals and vitamins salta
Chemical composition 45 25 15 11.2 0.2 0.9 0.6 0.6 1.5
DM (%) OM (% DM) ME (Mcal kg−1 DM)b CP (% DM) NDF (% DM) ADF (% DM) Ca (% DM) Total P (% DM)
89.8 92.7 2.75 12.3 36.7 24.2 0.92 0.74
a Contained per kg: 227 g MgSO4 ·H2 O, 12.5 g FeSO4 ·7H2 O, 2.8 g CuSO4 ·5H2 O, 12.2 g MnSO4 ·H2 O, 13.4 g ZnSO4 ·H2 O, 20 mg Na2 SeO3 , 50 mg KI, 35 mg CoCl2 ·6H2 O, 90,000 IU vitamin A, 17,000 IU vitamin D, and 17,500 IU vitamin E. b Metabolic energy was calculated according to NRC (1981).
Tea catechins (TC), a predominant group of polyphenols present in green tea leaves (Camellia sinensis L.), comprise mainly four compounds namely (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), and (−)-epigallocatechin gallate (EGCG). The antioxidative properties of dietary TC supplementation have already been studied in human, rats, beef cattle, chicken and pig using in vivo or in vitro experiments, however, few data are available on its antioxidative properties and meat quality in goats. The objectives of current study were to investigate the antioxidant properties of different levels of dietary TC supplementation against lipid oxidation, and to assess the effect of dietary TC supplementation on meat quality traits of growing goats. 2. Materials and methods The experiment was conducted according to the animal care and the use guidelines of the Animal Care Committee, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, China.
123
2.3. Blood sampling and slaughtering procedure At days 0, 20, 40 and 60 of the trial period, blood samples (20 mL) were taken from the jugular vein of each goat at 06:00 and 10:00 h into Li-heparin treated tubes to obtain blood plasma. Blood samples were centrifuged using centrifuge (Himac CR22G2, Hitachi Koki Co., Ltd) at 3000 rpm for 15 min at 4 ◦ C to harvest plasma. Thereafter, samples were stored at −20 ◦ C until analysis of plasma total antioxidant status (TAS). At the end of 60 days of feeding period, all goats were weighed and humanely slaughtered in line with the approved commercial procedures by the animal ethic committee of Institute of Subtropical Agriculture. The animals were allowed to bleed after which their bodies were hung to remove the skin, head, fore feet, hind feet, gastrointestinal tract and viscera organs. The left side of carcass was kept under aseptic condition at 4 ◦ C for meat quality determination. Muscles were removed from left side of the carcass and all external fat and connective tissue were also removed within 24 h postmortem. About 200 g each of left M. longissimus dorsi (LD), gluteus medius (GM) and semimemberanosus (SM) muscles were sampled. 50 g each of sampled muscles were ice-dried for analysis of intramuscular fat (IMF) while another 50 g each of muscles were cut into small slices (1 cm in width × 1 cm in length), vacuum packaged and stored at 4 ◦ C dark for the measurement of total haem pigment content (THP) and thiobarbituric acid reactive substances (TBARS). About 80 g each of muscles samples were further taken and cut into small slices (3 cm in width × 10 cm in length), before hanging them in an icebox at 4 ◦ C under aseptic condition for the determination of drip loss. Another 20 g muscle samples were kept at 4 ◦ C under aseptic condition for 24 h to assay muscle pH value. 2.4. Analytical procedure Plasma TAS was measured using a commercially available TAS kit (Total Antioxidant Status, Jiancheng Biology Co., Nanjing, China) according to the manufacturer’s instructions. Lipid oxidation of LD, GM and SM samples were measured on day 0, 2, 4, 6 and 8 of postmortem aging according to TBARS by the modified method of Olsvik et al. (2005). Drip loss percentage was measured by hanging slices in sealed aseptic polythene bags at days 2, 4, 6 and 8 of postmortem aging, and expressed as the loss weight proportion to the original weight. Samples of LD, GM and SM (10 g) at 24 h postmortem were homogenized (1 min, 24,000 rpm) in 100 mL of ice phosphate buffer solution (pH 7.0) using Power Gen Model 125 homogenizer (Fisher Scientific, Beijing, China). The pH value of the homogenate was measured at 20 ◦ C using a pH meter (6250 membrane pH meter, Yibo Instruments Co., Shanghai, China). The IMF content of LD, GM and SM were evaluated using the method of ether extraction on Sohxtex (AOAC, 1990). The THP of LD, GM and SM on days 0, 1, 3, 5 and 7 postmortem were measured according to the method of Ockerman (1985).
2.1. Tea catechins preparation 2.5. Statistical analysis The TC (purity of 80.86%) was extracted from green tea leaves (C. sinensis L.) by using high pressure liquid chromatography (HPLC) (Model Waters600, Waters Co., Milford, USA). The extracted TC contained caffeine (0.75%), (+)-catechin and (−)-catechin (DL-C) (1.61%), EC (5.77%), EGC (0.47%), ECG (13.03%), (−)-gallocatechin gallate (GCG) (1.56%) and EGCG (57.67%), respectively.
2.2. Experimental design, animal management and diets Forty Liuyang black male goats (a local breed) with average age of 8 months ± 10 days, average initial body weight of 16.2 ± 1.2 kg and same genetic background were randomly divided into four equal groups (ten animals in each group) and assigned to four experiment diets for 60 days of feeding trial. The control group (TC0) was fed basal diet without TC supplementation. The other three groups were fed basal diet with dietary TC supplementation at levels of 2000 (TC2000), 3000 (TC3000) and 4000 (TC4000) mg TC/kg feed (on DM basis). The ingredients and chemical composition of basal diet are shown in Table 1. All goats were castrated surgically before the commencement of the trial, and then allowed a recovery period of two weeks. During feeding period, each kid was fed twice daily (08:00 and 20:00 h) with 578 g feed each day (on DM basis) and recorded the orts daily. Each goat was assigned to single finishing barn with average temperature of 24 ± 1 ◦ C and free access to fresh water. After 60 days of feeding period, all goats were humanely slaughtered and samples collected.
All data were subjected to analysis of variance (ANOVA) using the generalized linear model procedure of SAS (2002). The main effect tested was the TC supplementation level for all variables. The following statistical model was used for data analysis, which had repeated measure over time.
Yij = m + Ti + Dj + Ti × Dj + eij where Yij is dependent variables, is the overall mean, Ti is the effect of treatment (i = 1, 2, 3, 4), Dj is the effect of aging time as repeated measure (j = 1, 2, 3, 4, 5) for pH value, IMF, TBARS, drip loss and THP of individual muscles or the effect of feeding period as repeated measure (j = 1, 2, 3, 4) for plasma TAS, Ti × Dj is the interaction between Ti and Dj and eij is the random residual error. Where the effects of treatment were significant, differences among means were tested with Duncan’s multiple range tests. Statistical significance was declared at P ≤ 0.05.
3. Results and discussion Supplementation of TC had significant effect (P < 0.05) on plasma TAS at days 40 and 60. Plasma TAS decreased with the feeding time extension, but dietary TC treatments still had higher values than that of TC0 (Table 2). Plasma
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Table 2 Effect of dietary tea catechin (TC) supplementation on plasma total antioxidant status (TAS, U/mL). Feeding period (days)
0 20 40 60
Treatment TC0
TC2000
TC3000
TC4000
5.15 4.15 3.69a 2.80b
5.23 3.74 3.05b 3.05ab
5.32 3.78 3.06b 3.10ab
5.36 3.58 3.48ab 3.16a
SEMe
TC effect (P value) Linear
Quadratic
Cubic
0.533 0.324 0.267 0.182
NS NS NS
NS NS
NS NS NS NS
*
*
NS
a,b,c,d
Mean values followed by different superscripts in the same row differ significantly (P < 0.05). NS, not significant. * P < 0.05. e SEM = standard error of mean.
TAS is a useful indicator of the fate of antioxidant supplement in animal diets. A condition of decreased TAS has been attributed to antioxidant enzymes, in which their effects are exerted in dose and time-dependent manner (Granado-Serrano et al., 2009). The current results showed that plasma TAS of goats increased with increasing dietary TC supplementation at long term TC feeding. This observation is an indication that TC supplementation can protect ruminants against oxidation stress under suitable feeding condition. Supplementation using TC had significant linear effect (P < 0.01) on TBARS values of LD, GM and SM. Generally, the muscle TBARS values of all the groups fed TC showed sharp increasing trends than control group. Moreover, the effect showed dose-dependent manner, and TC4000 treatment had lowest TBARS among all four groups (Table 3). Malondialdehyde, a secondary product of lipid oxidation, is known to be toxic and carcinogenic in human. Hashimoto et al.
(1999) elucidated that the TC could protect phospholipids bilayers and low-density lipoprotein against lipid oxidation. During the last decade, many studies have emphasized the tea catechins’ function of inhibiting lipid oxidation in chicken meat and in raw red meat. Although some studies have reported no effect of TC supplementation on lipid oxidation of beef, our results have shown that TC could improve lipid stability of fresh meat of goats kept under refrigeration. Drip loss of LD showed no significantly change with TC supplementation, while that of GM decreased significantly (P < 0.05). For SM, its drip loss was significantly linear (P < 0.05), and TC4000 had the lowest value than the other groups (Table 3). In this trial, increased value of drip loss might be closely related to lipid oxidation, while this effect might be due to dietary TC supplementation in decreasing lipid oxidation, enhancing integrity of cellular membrane and consequently improving the water holding ability of
Table 3 Effect of dietary tea catechin (TC) supplementation on TBARS, drip loss, total haem pigment content (THP), pH value and intramuscular fat (IMF) and of M. longissimus dorsi (LD), gluteus medius (GM) and semimemberanosus (SM). Muscle
SEMe
Treatment TC0
TC2000
TC3000
TC4000
TBARS (g MDA/g meat) LD 1.71a GM 1.75a SM 1.91a
1.35b 1.54b 1.85a
1.01c 1.13c 1.54b
1.05c 1.05d 1.42c
0.020 0.017 0.033
Drip loss (%) LD GM SM
2.07 1.67ab 2.13a
2.09 1.41b 1.98a
2.09 1.48ab 1.57b
0.146 0.126 0.106
2.00 1.84a 1.95a
THP (g/g meat) LD 138.7b GM 168.2 SM 138.4b pH of 24 postmortem LD 5.39 GM 5.37b SM 5.37a IMF (g/kg) LD GM SM a,b,c,d
98.3 106.6 96.1a
139.8b 180.1 158.2a 5.35 5.47a 5.37a 121.2 126.6 93.6a
138.9b 184.7 137.3b 5.32 5.33b 5.29b 101.0 120.7 73.3b
155.1a 172.9 153.5a 5.34 5.36ab 5.34ab 115.5 92.2 89.6a
TC effect (P value) Linear
Quadratic
Cubic
**
**
**
**
**
**
**
**
**
NS
NS NS
NS NS NS
* *
**
3.906 5.933 4.963
*
*
NS NS
NS NS
0.033 0.032 0.021
NS NS NS
NS NS NS
1.266 1.074 0.468
NS NS NS
NS NS NS
Mean values followed by different superscripts in the same row differ significantly (P < 0.05). NS, not significant. * P < 0.05. ** P < 0.01. e SEM = standard error of mean.
NS NS **
NS * *
NS NS **
R.Z. Zhong et al. / Small Ruminant Research 87 (2009) 122–125
meat. One interesting finding was that drip loss of LD was not affected by TC supplementation, and the reason for this should be further studied. Supplementation of TC had significant linear effect on THP content of LD (P < 0.05) and cubic effect on SM (P < 0.01). As a whole, the THP of LD in TC4000 group had highest value than that of other treatments, while the THP content of SM in TC2000 and TC4000 treatments showed higher value than the other two groups (Table 3). For red meat, the colour is determined by the amount of haem pigment and myoglobin. It has been established that meat colour and lipid oxidation are negatively correlated. In the present study, the reason for improved pigment stability of muscle might be linked to the retardation of lipid, protein and myoglobin oxidation in meat because of the addition of TC. The TC supplementation had no significant effect on pH value of LD, but had significant cubic effect (P < 0.05) on pH values of GM and SM. As a whole, muscle pH values of all the TC supplementation groups were lower than that of control except pH value of GM in TC2000 group (Table 3). The ultimate pH value of postmortem muscle can be correlated with meat tenderness. Many studies have reported the curvilinear relationship between tenderness and ultimate pH value of meat, and the optimum tenderness occurred at approximately pH value of 6 in beef cattle. Our study has provided valid evidence that dietary TC affected the ultimate pH value of postmortem muscle of goats. Variations in ultimate pH value for different types for goat’s muscle in the present study were similar to those reported by Kadim et al. (2003). Dietary TC supplementation had no significant effect on IMF of LD and GM, but IMF of SM was affected cubically (P < 0.01). For LD, TC2000 was found highest among all groups. For GM, TC2000 and TC3000 groups had numerically higher IMF, but TC4000 group had lower IMF than that of control group. For SM, supplementation of TC insignificantly decreased IMF with TC3000 group being the lowest (Table 3). Intramuscular fat content is positively correlated with the tenderness, juiciness and taste of meat. Though IMF is a stable index mainly affected by genetic factors, some studies have also reported different observations on the relationship between supplementation of antioxidant and IMF deposition (Nade et al., 2003). Our results indicated that dietary antioxidant is not the main factor in determining IMF percentage. Detailed of the physiological mechanism involved in this should be further investigated. 4. Conclusion This work showed that TC is a promising natural antioxidant to improve meat quality in goats. TC acts
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as antioxidant to modulate TAS of organisms, enhance integrity of cellular membrane, improved fresh meat colour stability and decreased TBARS and drip loss consequently. Although TC supplementation had significant influence on muscle pH of SM and IMF of GM and SM, but different muscle types showed different trends to change, and the quality of LD was relative stable according to overall evaluation. Another interesting finding was that the effect of TC supplementation is dose and feeding period dependent. Feeding period of 40–60 days and supplementation dose of 3000–4000 mg TC/kg feed have better effects in goats. Acknowledgement We would like to express our sincere gratitude and appreciation to the Ministry of Science and Technology of China (2006BAD04A15) for providing the financial support for this study. References AOAC (Association of Official Analytical Chemists), 1990. Official Methods of Analysis, vol. 2., 5th ed. Association of Official Analytical Chemist, Washington, DC, USA, Arlington, Virginia. Granado-Serrano, A.B., Martín, M.A., Goya, L., Bravo, L., Ramos, S., 2009. Time-course regulation of survival pathways by epicatechin on HepG2 cells. J. Nutr. Biochem. 20, 115–124. Hashimoto, T., Kumazawa, S., Nanjo, F., Hara, Y., Nakayama, T., 1999. Interaction of tea catechins with lipid bilayers investigated with liposome systems. Biosci. Biotechnol. Biochem. 63, 2252–2255. Kadim, I.T., Mahgoub, O., Al-Ajmi, D.S., Al-Maqbaly, R.S., Al-Saqri, N.M., Ritchie, A., 2003. An evaluation of the growth, carcass and meat quality characteristics of Omani goat breeds. Meat Sci. 66, 203– 210. Nade, T., Hirabara, S., Okumura, T., Fujita, K., 2003. Effects of vitamin A on carcass composition concerning younger steers fattening of Wagyu cattle. Asian-Aust. J. Anim. Sci. 16, 353–358. Nissen, H., Alvseike, O., Bredholt, S., Holck, A., Nesbakken, T., 2000. Comparison between the growth of Yersinia enterocolitica, Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp. in ground beef packed by three commercially used packaging techniques. Int J. Food Microbiol. 59, 211–220. NRC, Nurient Requirements of Goats: Angora, 1981. Dairy and Meat Goats in Temperate and Tropical Countries. National Academy Press, Washington DC, USA, 110–115 pp. Ockerman, H.W., 1985. Quality Control of Post-Mortem Muscle Tissue. Department of Animal Sciences, The Ohio State University, Columbus, OH, USA. Olsvik, P.A., Kristensen, T., Waagbø, R., Rosseland, B.O., Tollefsen, K.E., Baeverfjord, G., Berntssen, M.H.G., 2005. mRNA expression of antioxidant enzymes (SOD, Cat and GSH-Px) and lipid peroxidative stress in liver of Atlantic salmon (Salmo salar) exposed to hyperoxic water during smoltification. Comp. Biochem. Physiol. 141, 314– 323. SAS, 2002. SAS/STAT® User’s Guide: Statistics. Version 9.1 Edition. SAS Inc., Cary, NC, USA. Sánchez-Escalante, A., Djenane, D., Torrescano, G., Beltrán, J.A., Roncalés, P., 2003. Antioxidant action of borage, rosemary, oregano, and ascorbic acid in beef patties packaged in modified atmosphere. J. Food Sci. 68, 339–344.