Chemical and Fatty acid composition of different cuts cooked or uncooked from yearling bulls fed oil sources

Composição química e lipídica de diferentes cortes cárneos in natura ou assados de tourinhos alimentados com fontes de óleo

Emanuel Almeida de Oliveira Alexandre Amstalden Moraes Sampaio Wignez Henrique Thiago Martins Pivaro Bruna Laurindo Rosa Alexandre Rodrigo Mendes Fernandes About the authors

Abstracts

This study evaluated the chemical and lipid composition of uncooked or cooked loin (Longissimus thoracis) and rump (Biceps femoris) in samples of 2.54 cm thick from 35 carcasses of Nellore young bulls finished in feedlot for 96 days and slaughtered at an average weight of 532.17 ± 30.25 kg and 24 months of age. The rump had the lowest level of protein and ash (18.57 and 0.90%, respectively) and the highest level of ether extract compared to loin (3.37 and 1.90%, respectively). Higher levels of cholesterol were found in rump compared to loin (40.91 e 30.93 mg 100 g-1, respectively). The uncooked loin showed lower content of saturated fatty acids and higher content of polyunsaturated fatty acids. The best values for the omega-6: omega-3 ratio was observed in the uncooked beef. In the present study, the loin was healthier due to the higher amount of polyunsaturated fatty acids compared to rump. Cooking the meat decreases the levels of polyunsaturated fatty acids, omega-3, omega-6 and the omega-6: omega-3 ratio.

Conjugated linoleic acid; cholesterol; ether extract; meat cuts; protein


Objetivou-se avaliar as diferenças na composição química e lipídica do contrafilé (Longissimus thoracis) e da picanha (Biceps femoris) in natura ou assados de bovinos alimentados com diferentes fontes de óleo. Para isto, foram utilizadas amostras, seccionadas em bifes de 2,54 cm, do contrafilé e da picanha, provenientes de 35 carcaças de tourinhos da raça Nelore, confinados por 96 dias e abatidos com peso médio de 532,17 ± 30,25 kg e 24 meses de idade. A picanha apresentou os valores mais baixos de proteína e cinzas (18,57 e 0,90%, respectivamente). No entanto, os maiores teores de extrato etéreo também foram encontrados para este corte comparado ao contrafilé (3,37 e 1,90%, respectivamente). Maiores teores de colesterol foram encontrados na picanha em relação ao contrafilé (40,91 e 30,93 mg 100 g-1, respectivamente). O contrafilé in natura apresentou menores teores de ácidos graxos saturados e maiores quantidades de ácidos graxos poli-insaturados. Para as relações dos ácidos graxos ômega-6: ômega-3, os melhores valores foram encontrados na carne in natura. O contrafilé, no presente estudo, mostrou-se mais saudável pela maior quantidade de ácidos graxos poli-insaturados que a picanha. Assar a carne diminui os teores de ácidos graxos poli-insaturados, ômega-3 e ômega-6, além da relação ômega-6: ômega-3.

Ácido linoleico conjugado; colesterol; extrato etéreo; cortes cárneos; proteína.


Introduction

Currently, consumers are more concerned to find safe and healthy foods that have quality and convenience (Guerrero et al., 2013Guerrero, A., Valero, M. V., Campo, M. M. & Sañudo, C. (2013). Some factors that affect ruminant meat quality: from the farm to the fork. Review. Acta Scientiarum. Animal Sciences, 35(4), 335-347. ; Hocquette et al., 2012Hocquette, J.-F., Botreau, R., Picard, B., Jacquet, A., Pethick, D. W. & Scollan, N. D. (2012). Opportunities for predicting and manipulating beef quality. Meat Science, 92(3), 197-209.). Furthermore, beef is an important food with a high nutritional value, containing important and essential constituents, such as proteins and minerals. Besides, beef is considered an easily prepared food (Scollan et al., 2006Scollan, N., Hocquette, J. F., Nuernberg, K., Dannenberger, D., Richardson, I. & Moloney, A. (2006). Innovations in beef production systems that enhance the nutritional and health value of beef lipids and their relationship with meat quality. Meat Science, 74(1), 17-33. ).

Over the last 15 years, beef consumption has been associated with several negative drawbacks, such as increased levels of cholesterol, incidence of coronary heart disease and cancer (Scollan et al., 2006Scollan, N., Hocquette, J. F., Nuernberg, K., Dannenberger, D., Richardson, I. & Moloney, A. (2006). Innovations in beef production systems that enhance the nutritional and health value of beef lipids and their relationship with meat quality. Meat Science, 74(1), 17-33. ). Thereby, researches on human nutrition suggest that the intake of fats derived from animal products should be between 15 and 30% of total calories, for saturated fats, the ingestion should not exceed 10%, and for cholesterol, should not exceed 300 mg daily (Chizzolini et al., 1999Chizzolini, R., Zanardi, E., Dorigoni, V. & Ghidini, S. (1999). Calorific value and cholesterol content of normal and low-fat meat and meat products. Trends in Food Science & Technology, 10(4-5), 119-128.).

However, beef has important elements derived exclusively from ruminants, such as conjugated linoleic acid (Prado et al., 2008Prado, I. N., Rotta, P. P., Prado, R. M., Visantainer, J. V., Moletta, J. L. & Perotto, D. (2008). Carcass characteristics and chemical composition of the Longissimus muscle of Purunã and 1/2 Purunã vs. 1/2 Canchin bulls. Asian-AustralasianJournal of Animal Sciences, 21(9), 1296-1302. ; Rotta et al., 2009Rotta, P. P., Prado, R. M., Prado, I. N., Valero, M. V., Visentainer, J. V. & Silva, R. R.(2009). The effects of genetic groups, nutrition, finishing systems and gender of Brazilian cattle on carcass characteristics and beef composition and appearance: a review. Asian-Australasian Journal of Animal Sciences, 22(12), 1718-1734.), which has proven benefits to human health, including tumor reduction, reduced risks for developing atherosclerosis, and increased immunity. In this sense, the manipulation of diets for ruminants with precursors of important fatty acids, such as C18:2 ω6 or C18:3 ω3, or even the addition of foodstuff rich in unsaturated fatty acids could be very interesting (Ito et al., 2010Ito, R. H., Ducatti, T., Prado, J. M., Prado, I. M., Rotta, P. P., Valero, M. V., ... Silva, R. R. (2010). Soybean oil and linseed grains on performance and carcass characteristics of crossbred bulls finished in feedlot. Semina: Ciências Agrárias, 31(1), 259-268. ; Souza et al., 2007Souza, N. E., Silva, R. R., Prado, I. M., Prado, J. M., Wada, F. Y. & Prado, I. N. (2007). Grãos de linhaça e canola sobre a composição do músculo Longissimus de novilhas confinadas. Archivos de Zootecnia, 56(216), 863-874. ).

This study was performed to assess differences in chemical and fatty acid composition between two commercial cuts (loin and rump), common in Brazilian cuisine, uncooked or cooked, from Nellore young bulls finished in feedlot and fed diets rich in omega-3 and omega-6 fatty acids.

Material and methods

For this study, samples of loin (L. thoracis) and rump (B. femoris) were taken from 35 Nellore young bulls with an average body weight of 402.69 ± 14.90 kg and an average age of 18 ± 2 months. The experiment was conducted at the Beef Cattle Sector of the Department of Animal Sciences, College of Agrarian and Veterinary Sciences of Unesp (Jaboticabal, São Paulo State, Brazil). All experimental procedures were approved by the Committee for Ethics and Animal Welfare (Cebea), College of Agrarian and Veterinary Sciences (protocol 021167-07).

Prior to the experimental period, these animals were randomly assigned to different treatments, and subsequently adapted to specific management conditions and diets for 28 days. At the end of the experimental period, the animals were transported to a slaughterhouse 200 km away, stunned and slaughtered. At the time of slaughter, the bulls exhibited an average weight of 532.2 ± 30.2 kg, an average carcass dressing of 55.3 ± 1.30 %, and an average fat thickness of 7.0 mm.

The five experimental diets were formulated using the RLM(r) software (Esalq/USP), with nutritional demands estimated by the CNCPS system (Fox et al., 1992Fox, D. G., Sniffen, C. J., O'Connor, J. D., Russell, J. B. & Van Soest, P. J. (1992). A net carbohydrate and protein system for evaluating cattle diets: III. Cattle requirements and diet adequacy. Journal of Animal Science, 70(11), 3578-3596. ) with the aim of maximum weight gain (Table 1). The first diet was the Control with no oil added. The other four diets were composed of different lipid sources as follow: Soybean oil (unprotected soybean oil), Linseed oil (unprotected linseed oil), Megalac- E(r) (soybean oil protected from ruminal degradation) and PLO (linseed oil protected from ruminal degradation), all diets had sugar cane IAC 86-2480 at 40% DM as exclusive forage.

Since protected linseed oil is not commercially available, a method was developed to obtain this product from regular linseed oil at the Laboratory of Applied Enzymology of the College of Agrarian and Veterinary Sciences of Unesp.

Table 1:
Composition (% of dry matter (DM)), nutritional characteristics, and fatty acid composition of the experimental diets.

Linseed oil was saponified with sodium hydroxide in 65% ethanol using an unheated plastic drum and agitated until glycerol and soap was produced. Once saponification was complete, a saturated solution of calcium chloride was added to precipitate the soap. The mixture of water and glycerol was then collected and the calcium soap dried at room temperature. The resulting product contained large quantities of unsaturated fatty acids, with 85% protection at a pH level close to that of the rumen. Saponification of fat results in a product with a high total fat composition, a low content of free fatty acids, and almost no oxidation.

Immediately after slaughter, half-carcasses were stored at 4°C for 24h. From the left- half-carcasses, cuts between the 9th and 13th ribs and a triangular standard cut of the B. femoris muscle with about 1.5 kg were removed and taken to the laboratory for the proximate, cholesterol and fatty acids analysis.

For the cooked meat analysis, steaks with 2.54 cm from the 11th and 13th ribs of L. thoracis and the central part of B. femoris were taken. After, the steaks were cooked in a gas oven at 175°C until their geometric centers reached 71°C, measured by digital thermometer.

The proximate analysis for uncooked beef (moisture, protein, total lipids and ash) was performed according to AOAC (2005AOAC-Association Official Analytical Chemist (2005). Official methods of analysis (18th ed.). Gaitherburg, Maryland, USA: AOAC.).

The determination of the cholesterol content of uncooked loin (L. thoracis) and rump (B. femoris) were performed by colorimetry as described by Bragagnolo and Rodriguez-Amaya (1995Bragagnolo, N. & Rodriguez-Amaya, D. B. (1995). Teores de colesterol em carne suína e bovina e efeito do cozimento. Ciência e Tecnologia de Alimentos, 15(1), 11-17. ). The total lipid content was measured by extraction from approximately 10 g loin samples in 200 mL of a chloroform-methanol mixture (2:1). From this extract, 5 mL sample was dried using nitrogen gas, followed by addition of 10 mL 12% KOH in 90% ethanol. The solution was then placed in a water bath at 80°C and agitated for 15 min. At the end of this process, 5 mL water was added, and after cooling, 10 mL hexane was added and the solution was vortexing. After separation of the phases, a 10 mL sample was dried using nitrogen gas. Finally, 6 mL acetic acid saturated with concentrated ferrous sulfate was added. Once cooled, the absorbance was read at 538 nm.

To determine the fatty acid composition of uncooked and cooked beef, samples of cross section were collected from the muscle, freeze-dried and grind with liquid nitrogen for lipid extraction and fatty acids methylation. The fatty material was extracted using a mixture of chloroform-methanol, as reported by Bligh and Dyer (1959Bligh, E. G. & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology, 37(8), 911-917. ) with modification performed by Fernandes et al. (2009Fernandes, A. R. M., Sampaio, A. A. M., Henrique, W., Tullio, R. R., Oliveira, E. A. &Silva, T. M. (2009). Composição química e perfil de ácidos graxos da carne de bovinos de diferentes condições sexuais recebendo silagem de milho e concentrado ou cana-de-açúcar e concentrado contendo grãos de girassol. Revista Brasileira de Zootecnia, 38(4), 705-712. ). About 3 g of freeze dried sample was transferred to a 125 mL Erlenmeyer and then added 10 mL chloroform, 20 mL methanol and 8 mL of distilled water; the containers were shaken for 30 min in a shaker table. After this period, 10 mL chloroform and 10 mL 1.5% sodium sulfate were added and the Erlenmeyer were shaken again for 2 min. The material was filtered through a quantitative filter paper into a 50 mL falcon tube. After separation of the layers, the upper methanoic was discarded. From the remaining filtrate, 10 mL were transferred to a 50 ml weighed beaker. The beaker was taken to a forced air circulation oven at 55°C to evaporate the solvent, for 24h, and then cooled in a desiccator and weighed. The lipid content of the sample was calculated by the difference in weights.

For the transesterification of triglycerides, approximately 50 mg of extracted lipid matter was transferred to a 15 mL falcon tube, then, 2 mL n-heptane was added. The mixture was vortexed until complete dissolution of the fatty material. After this procedure, 2 mL of 2 mol KOH L-1 in methanol was added. This mixture was vortexed again for 5 min. After separation of the layers, 1 mL of the upper phase (heptane and fatty acids methyl esters) was transferred to 1.5 mL tubes. Tubes were tightly closed, protected from light and stored in a freezer at - 18°C for subsequent chromatographic analysis (Bligh & Dyer, 1959Bligh, E. G. & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology, 37(8), 911-917. ).

Qualitative and quantitative measurements of fatty acid content were performed by gas chromatography using a chromatograph (Shimadzu, GC-14B) with a flame ionization detector (FID) and fused silica capillary column (Omegawax 250), which was 30 m in length and 0.25 mm in diameter and a film thickness of 0.25 μm (Supelco SP-24136). Helium was used as a carrier gas at a flow of 1 mL min. A 1-μL aliquot of the sample was injected into a "split" at a division ratio of 1 100-1 and a temperature of 250°C. The temperature of the oven was programmed to remain at 100°C for 2 min and then increase to 220°C at 4°C min-1 for 25 min, while the detector was at 280°C. Identification and quantification of the methyl esters of the fatty acids was achieved by comparison with the retention times and concentrations of methyl esters of standard fatty acids.

The index of activity of the Δ9-desaturase enzyme on fatty acids with 18 carbons was obtained using the following equation: C18 = 100 (18:1/18:0 + 18:1), postulated by Malau-Aduli et al. (1997Malau-Aduli, A. E. O., Siebert, B. D., Bottema, C. D. K. & Pitchford, W. S. (1997). A comparison of the fatty acid composition of triacylglycerols in adipose tissue from Limousin and Jersey cattle. Australian Journal of Agricultural Research, 48(5), 715-722. ).

Results were subjected to analysis of variance using the general linear model (GLM) (SAS, 2004). A randomized block design was adopted for five treatments with seven replications. Mean values were compared using t-test at 5% significance level.

Results and discussion

The cholesterol analysis (Table 2) indicated differences (p < 0.05) between the muscles in this study. The rump presented 32.5% more cholesterol than the loin. Cholesterol values found in this study (30.9 and 40.1 mg 100 g-1 for loin and rump, respectively) were lower than the values considered normal (58.3 to 83.4 mg 100 g-1) for different beef cuts (Macedo et al., 2008Macedo, L. M., Prado, I. M., Prado, J. M., Rotta, P. P., Prado, R. M., Souza, N. E. & Prado, I. N. (2008). Chemical composition and fatty acids profile of five carcass cuts of crossbred heifers finished in feedlot. Semina: Ciências Agrárias, 29(3), 597-608. ; Maggioni et al., 2010Maggioni, D., Marques, J. A., Rotta, P. P., Perotto, D., Ducatti, T., Visentainer, J. V. & Prado, I. N. (2010). Animal performance and meat quality of crossbred young bulls. Livestock Science, 127(2), 176-182. ; Rotta et al., 2009Rotta, P. P., Prado, R. M., Prado, I. N., Valero, M. V., Visentainer, J. V. & Silva, R. R.(2009). The effects of genetic groups, nutrition, finishing systems and gender of Brazilian cattle on carcass characteristics and beef composition and appearance: a review. Asian-Australasian Journal of Animal Sciences, 22(12), 1718-1734.).

The use of diets containing sugar cane and vegetable oils, rich in polyunsaturated fatty acids, mainly, linoleic (C18:2 n6) and linolenic (C18:3 n3) acids, may have influenced the reduction in cholesterol in the animal body, reflecting the lower concentrations of this compound in the tissue (Prado et al., 2012Prado, I. N., Maggioni, D., Abrahão, J. J. S., Valero, M. V., Prado, R. M. & Souza, N. E. (2012). Meat quality of crossbred bulls fed with sorghum silage or sugar cane and slaughtered at two levels of fat thickness. Acta Scientiarum. Technology, 34(3), 337-344. ).

The differences between the cuts in this study can also be associated with the anatomical location of the muscle (Macedo et al., 2008Macedo, L. M., Prado, I. M., Prado, J. M., Rotta, P. P., Prado, R. M., Souza, N. E. & Prado, I. N. (2008). Chemical composition and fatty acids profile of five carcass cuts of crossbred heifers finished in feedlot. Semina: Ciências Agrárias, 29(3), 597-608. ), probably due to different rates of development of muscle fibers, the structure and diameter that may affect the cholesterol synthesis rate among the different muscles of the carcass (Werdi Pratiwi et al., 2006Werdi Pratiwi, N. M., Murray, P. J., Taylor, D. G. & Zhang, D. (2006). Comparison of breed, slaughter weight and castration on fatty acid profiles in the longissimus thoracic muscle from male Boer and Australian feral goats. Small Ruminant Research, 64(1-2), 94-100.).

Table 2:
Chemical composition of L. thoracis (loin) and B. Femoris (rump) from Nellore young bulls fed diets rich in Omega-3 and Omega-6 fatty acids.

Moreira et al. (2003Moreira, F. B., Souza, N. E., Matsushita, M., Prado, I. N. & Nascimento, W. G. (2003). Evaluation of carcass characteristics and meat chemical composition of Bos indicus and Bos indicus x Bos taurus crossbred steers finished in pasture systems. Brazilian Archives of Biology and Technology, 46(4), 609-616. ); Rule et al. (1997Rule, D. C., MacNeil, M. D. & Short, R. E. (1997). Influence of sire growth potential, time on feed, and growing-finishing strategy on cholesterol and fatty acids of the ground carcass and Longissimus muscle of beef steers. Journal of Animal Science, 75(6), 1525-1533. ) evaluated the cholesterol content of beef with different fat content in the carcass. These authors found that animals with greater amount of fat in the carcass had higher cholesterol levels on meat. Likewise, Chung et al. (2006Chung, K. Y., Lunt, D. K., Choi, C. B., Chae, S. H., Rhoades, R. D., Adams, T. H., ... Smith, S. B. (2006). Lipid characteristics of subcutaneous adipose tissue and M. longissimus thoracis of Angus and Wagyu steers fed to US and Japanese endpoints. Meat Science, 73(3), 432-441.) worked with Wagyu and Angus animals slaughtered at different feeding times and verified a strong correlation between marbling and cholesterol content.

There was no difference (p < 0.05) for moisture between the loin and rump (Table 2). Similar data were reported by Fernandes et al. (2009Fernandes, A. R. M., Sampaio, A. A. M., Henrique, W., Tullio, R. R., Oliveira, E. A. &Silva, T. M. (2009). Composição química e perfil de ácidos graxos da carne de bovinos de diferentes condições sexuais recebendo silagem de milho e concentrado ou cana-de-açúcar e concentrado contendo grãos de girassol. Revista Brasileira de Zootecnia, 38(4), 705-712. ), who evaluated the chemical composition of Nellore and Canchim young bulls fed diets with different concentrate levels.

Higher levels for protein and ash (p < 0.05) were observed for the loin. However, the ether extract was higher (p < 0.05) for the rump. Probably, the higher amount of ether extract in the rump resulted in smaller amounts of protein and ash in this cut.

According to Rotta et al. (2009Rotta, P. P., Prado, R. M., Prado, I. N., Valero, M. V., Visentainer, J. V. & Silva, R. R.(2009). The effects of genetic groups, nutrition, finishing systems and gender of Brazilian cattle on carcass characteristics and beef composition and appearance: a review. Asian-Australasian Journal of Animal Sciences, 22(12), 1718-1734.), the ether extract content is the most variable in meat and, once it increases, there is a decrease in the levels of moisture, protein and minerals. Beef has almost all important minerals for human nutrition and in quantitative terms, phosphorus and potassium predominate, followed by sodium and magnesium. In addition, the iron in beef is absorbed 3 to 5 times faster than when originating from vegetables.

There were significant differences (p < 0.05) for fatty acid composition between the two cuts (loin and rump) regardless of cooking. Lower values of saturated fatty acids C12:0, C14:0, C15:0 and C17:0 were found in loin (Table 3).

In this way, Bessa et al. (2009Bessa, R. J. B., Maia, M. R. G., Jerónimo, E., Belo, A. T., Cabrita, A. R. J., Dewhurst, R. J. &Fonseca, A. J. M. (2009). Using microbial fatty acids to improve understanding of the contribution of solid associated bacteria to microbial mass in the rumen. Animal Feed Science and Technology, 150(3-4), 197-206.) emphasized the importance of lower levels of fatty acids, such as C12:0 and C14:0. These fatty acids are harmful to human health, causing hypercholesterolemia.

Raes et al. (2004Raes, K., Haak, L., Balcaen, A., Claeys, E., Demeyer, D. & De Smet, S. (2004). Effect of linseed feeding at similar linoleic acid levels on the fatty acid composition of double-muscled Belgian Blue young bulls. Meat Science, 66(2), 307-315.) evaluated the fatty acid composition of beef cattle fed diets with similar levels of linoleic acid and found differences in the lipid composition between the L. thoracis and T. brachii muscles. The authors claimed that the differences were due to the amounts of triglycerides and phospholipids found in the muscles. According to these authors, phospholipids have large amounts of polyunsaturated fatty acids, while triglycerides consist mainly of saturated and monounsaturated fatty acids. Therefore, the differences found in this study may be related to differences in the fat composition.

Lower levels (p < 0.05) of monounsaturated fatty acids (Table 3) were observed for loin. Cifuni et al. (2004Cifuni, G. F., Napolitano, F., Riviezzi, A. M., Braghieri, A. &Girolami, A. (2004). Fatty acid profile, cholesterol content and tenderness of meat from Podolian young bulls. Meat Science, 67(2), 289-297.) reported that the monounsaturated fatty acids with cis configuration are hypocholesterolemic with the advantage of reducing the HDL cholesterol level, which protects against heart disease.

In this sense, Bessa et al. (2009Bessa, R. J. B., Maia, M. R. G., Jerónimo, E., Belo, A. T., Cabrita, A. R. J., Dewhurst, R. J. &Fonseca, A. J. M. (2009). Using microbial fatty acids to improve understanding of the contribution of solid associated bacteria to microbial mass in the rumen. Animal Feed Science and Technology, 150(3-4), 197-206.) reported that the hypocholesterolemic properties of monounsaturated fatty acids are obtained only from the oleic acid (C18:1 cis-9) since monounsaturated fatty acids such as elaidic (C18:1 trans-9), palmitoleic (C16:1 cis-9), and myristoleic (C14:1 cis-9) fatty acids do not have the same properties.

Turk and Smith (2009Turk, S. N. & Smith, S. B. (2009). Carcass fatty acid mapping. Meat Science, 81(4), 658-663.) evaluated the fatty acid composition of different ground cuts and detected differences for monounsaturated fatty acids, wherein the brisket had the highest (p = 0.0001) values compared to other cuts. These authors claimed that the differences are related to the activity of Δ9-desaturase enzyme.

Table 3.
Fatty acid composition of L. thoracis (loin) and B. femoris (rump), uncooked or cooked, from Nellore young bulls fed diets rich in Omega-3 and Omega-6 fatty acids.

The results for Δ9-desaturase enzyme indicated that rump presented higher activity (p < 0.05) of this enzyme than loin (73.9 and 73.1, respectively). According to Turk and Smith (2009Turk, S. N. & Smith, S. B. (2009). Carcass fatty acid mapping. Meat Science, 81(4), 658-663.), cuts located closer to the surface of the body could present higher activity of Δ9-desaturase due the lower body temperature.

The loin presented higher (p < 0.05) levels of the polyunsaturated fatty acids C18:2 ω6, C18:3 ω3, C20:2, C20:3 ω6 and C20:5 ω3. Increasing concentration of these acids is a goal to be achieved due to their important roles against diseases. On the other hand, conjugated linoleic acid (C18:2 c9, t11) showed a higher concentration in the rump.

According to Griswold et al. (2003Griswold, K. E., Apgar, G. A., Robinson, R. A., Jacobson, B. N., Johnson, D. & Woody, H. D. (2003). Effectiveness of short-term feeding strategies for altering conjugated linoleic acid content of beef. Journal of Animal Science, 81(7), 1862-1871. ), the conjugated linoleic acid (CLA) is found exclusively in ruminant products and man needs to eat about 400 mg CLA daily to have a benefit. Thus, the daily diet with meat and milk can provide considerable amounts of this element.

In the present study, the difference found for CLA is related to the greater activity of Δ9-desaturase enzyme in the rump (Table 3). According to Griswold et al. (2003Griswold, K. E., Apgar, G. A., Robinson, R. A., Jacobson, B. N., Johnson, D. & Woody, H. D. (2003). Effectiveness of short-term feeding strategies for altering conjugated linoleic acid content of beef. Journal of Animal Science, 81(7), 1862-1871. ), there are two ways of CLA production, the first occurs with rumen biohydrogenation of linoleic acid and the second is the conversion of C18:1 t11 (trans vaccenic acid) into the CLA by means of the activity of Δ9-desaturase enzyme.

Beaulieu et al. (2002Beaulieu, A. D., Drackley, J. K. & Merchen, N. R. (2002). Concentrations of conjugated linoleic acid (cis-9, trans-11-octadecadienoic acid) are not increased in tissue lipids of cattle fed a high-concentrate diet supplemented with soybean oil. Journal of Animal Science, 80(3), 847-861. ); Malau-Aduli et al. (1997Malau-Aduli, A. E. O., Siebert, B. D., Bottema, C. D. K. & Pitchford, W. S. (1997). A comparison of the fatty acid composition of triacylglycerols in adipose tissue from Limousin and Jersey cattle. Australian Journal of Agricultural Research, 48(5), 715-722. ) commented that this enzyme is responsible for the desaturation of saturated fatty acids with 16 and 18-carbon, converting them into their corresponding monounsaturated forms, by adding a double bond at the carbon 9. The production of CLA by Δ9-desaturase is performed using the trans vaccenic acid (C18:1 t11), product of the incomplete biohydrogenation of linoleic and linolenic acids by the rumen bacteria. As reported by the same authors, this enzyme has activity in the intestine epithelium and in muscles, but at lower intensity compared with adipose tissue; its activity can be influenced by animal breed, age, sex and degree of maturity.

Saturated fatty acids, mainly the hypercholesterolemic ones (C12:0, C14:0 and C16:0), presented the lowest levels in the uncooked cuts. Herein, the cooking process increased the levels of those fatty acids, probably due to loss of moisture and saturation of unsaturated fatty acids.

Differences were found (p < 0.05) for all fatty acids analyzed, except for the fatty acids C20:0 and C20:1 ω9. There was a significant increase (p < 0.05) in concentrations of C12:0 and C14:0 fatty acids after cooking the beef. These results corroborate those obtained by Alfaia et al. (2010Alfaia, C. M. M., Alves, S. P., Lopes, A. F., Fernandes, M. J. E., Costa, A. S. H., Fontes, C. M. G. A., ... Prates, J. A. M. (2010). Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat. Meat Science, 84(4), 769-777.), who examined steaks from Alentejano breed subjected to different cooking methods (grilled, stewed and microwave). The authors found an increase in the concentration of C12:0 and C14:0 fatty acids.

According to Alfaia et al. (2010Alfaia, C. M. M., Alves, S. P., Lopes, A. F., Fernandes, M. J. E., Costa, A. S. H., Fontes, C. M. G. A., ... Prates, J. A. M. (2010). Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat. Meat Science, 84(4), 769-777.), there are many mechanisms responsible for changes in the lipid composition of beef, including loss of moisture loss and lipid oxidation. The same authors commented that the physical and chemical properties of beef undergo several changes during the heating process, especially its lipid composition, which, combined with the cooking method, provides great changes in the final meat quality.

Nevertheless, Scheeder et al. (2001Scheeder, M. R. L., Casutt, M. M., Roulin, M., Escher, F., Dufey, P.-A. & Kreuzer, M. (2001). Fatty acid composition, cooking loss and texture of beef patties from meat of bulls fed different fats. Meat Science, 58(3), 321-328. ) verified decrease in the concentration of some saturated fatty acids (C14:0, C16:0 and C18:0) and increased concentrations of polyunsaturated fatty acids, when they studied processed beef derived from animals fed diets with different oil sources.

The same authors reported that polyunsaturated fatty acids were less affected by the effects of cooking, such as oxidation, because they belong to the structure of cell membranes, whereas saturated fatty acids are mostly present in triglycerides of the adipose tissue, which suffer greater losses, mainly due to drip loss.

Thus, Rodriguez-Estrada et al. (1997Rodriguez-Estrada, M. T., Penazzi, G., Caboni, M. F., Bertacco, G. & Lercker, G. (1997). Effect of different cooking methods on some lipid and protein components of hamburgers. Meat Science, 45(3), 365-375.) argued that heating can trigger unpleasant changes such as loss of essential fatty acids, reducing the nutritional value of beef, mainly due to the oxidation of lipids. Additionally, meat cuts with higher levels of polyunsaturated fatty acids are likely to suffer more oxidation.

There was a decrease (p<0.05) in the CLA level for cooked rump; however, no change was observed for uncooked or cooked loin. Ha et al. (1989Ha, Y. L., Grimm, N. K. & Pariza, M. W. (1989). Newly recognized anticarcinogenic fatty acids: identification and quantification in natural and processed cheeses. Journal of Agricultural and Food Chemistry, 37(1), 75-81. ) commented that the increase in CLA levels can be observed in cooked compared to uncooked beef. This probably occurs by the temperature and cooking methods that influence its concentration. However, CLA can also be denatured if the cooking temperatures are extremely high.

Shantha et al. (1994Shantha, N. C., Crum, A. D. & Decker, E. A. (1994). Evaluation of conjugated linoleic acid concentrations in cooked beef. Journal of Agricultural and Food Chemistry, 42(8), 1757-1760. ) commented that since the CLA assumed an important role as beneficial to health, there is a need to establish how meat must be prepared in order to not affect the CLA concentration.

There were no interactions for the sums of fatty acids (Table 4). There was higher (p < 0.05) amounts of saturated (SFA) and polyunsaturated (PUFA) fatty acids for loin compared to rump, however, the rump showed higher amounts of unsaturated (UFA) and monounsaturated (MUFA) fatty acids. The higher (p < 0.05) levels of Omega-3 and Omega-6 fatty acids were observed for the loin.

The differences detected for fatty acids between the muscles in the present study may be related to the amounts of phospholipids and triacylglycerols present in different locations. According to Raes et al. (2004Raes, K., Haak, L., Balcaen, A., Claeys, E., Demeyer, D. & De Smet, S. (2004). Effect of linseed feeding at similar linoleic acid levels on the fatty acid composition of double-muscled Belgian Blue young bulls. Meat Science, 66(2), 307-315.), the highest amount of triacylglycerol compared to phospholipid provides higher levels of saturated and polyunsaturated fatty acids.

In this sense, Picard et al. (1998) reported that glycolytic muscles have lower levels of mitochondria, and thus lower amounts of phospholipids, which are restricted to membranes. The lower amounts of phospholipids result in lower amounts of polyunsaturated fatty acids and consequently higher amounts of saturated and monounsaturated fatty acids.

Higher amounts (p < 0.05) of saturated fatty acids were observed for the L. thoracis cooked. For the rump, there was no difference (p > 0.05) between uncooked and cooked cuts.

Table 4:
Fatty acids ratios of L. thoracis (loin) and Biceps femoris (rump), uncooked or cooked, from Nellore young bulls fed diets rich in Omega-3 and Omega-6 fatty acids.

Also, significant losses (p < 0.05) of polyunsaturated, Omega-3 and Omega-6 fatty acids were observed when those two cuts were cooked. Alfaia et al. (2010Alfaia, C. M. M., Alves, S. P., Lopes, A. F., Fernandes, M. J. E., Costa, A. S. H., Fontes, C. M. G. A., ... Prates, J. A. M. (2010). Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat. Meat Science, 84(4), 769-777.) found similar results with reduction of polyunsaturated fatty acid. These results may be related to higher susceptibility to oxidation of polyunsaturated fatty acid.

The rump had the best (p < 0.05) ratios UFA:SFA and MUFA:SFA, while the PUFA:SFA and Omega-6:Omega-3 ratios were better (p < 0.05) for the loin. These results are mainly associated with the individual value of each fatty acid (Table 3).

According to Alfaia et al. (2010Alfaia, C. M. M., Alves, S. P., Lopes, A. F., Fernandes, M. J. E., Costa, A. S. H., Fontes, C. M. G. A., ... Prates, J. A. M. (2010). Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat. Meat Science, 84(4), 769-777.), there are recommendations for the fatty acids ratios, the PUFA:SFA ratio should not be less than 0.45 and the omega-6:omega-3 ratio should not exceed 4. The results obtained for the PUFA:SFA ratio was far from ideal, however, the omega-6:omega-3 ratio met the ideal standards, even with cooked meat.

Conclusion

Cooking meat decreases its moisture and consequently concentrates its protein, ether extract and minerals in loin and rump.

The rump has higher levels of myristic fatty acid, and the higher levels of conjugated linoleic acid.

The loin showed the best fatty acid composition when uncooked. The cooking process causes loss of important fatty acids.

Regardless of the cut, cooking meat affects negatively the amounts of polyunsaturated, omega-3 and omega-6 fatty acids as well as the omega-6:omega-3 ratio.

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Publication Dates

  • Publication in this collection
    June 2015

History

  • Received
    05 Feb 2015
  • Accepted
    20 Mar 2015
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