Lipid composition of raw and grilled beef cattle slaughtered at four body weights

The fatty acid composition of beef can be altered by factors related to the animal, management, processing and preparation. The effect of body weight and cooking of meat on the composition of long chain fatty acids was evaluated. Forty 10-month old crossbred young bulls (1⁄2 Brown Swiss x 1⁄2 Nellore) of initial body weight 219 kg finished in feedlot with high grain diet and slaughtered with 450, 469, 491 and 513 kg of body weight. The Longissimus dorsi muscle was collected after slaughter and carcass chilling. The individual composition of the fatty acids of the meat was not altered (P < 0.05) by different body weights and by cooking (until reaching 72o C). Likewise, the sum of the percentages of saturated, monounsaturated, polyunsaturated, omega 3 and 6 fatty acids; as well as the ratios between monounsaturated/polyunsaturated fatty acids and omega 3 and 6 were not altered. Therefore, the different body weights and heating used in this study were insufficient to cause significant alterations in the fat molecules and the meat can be consumed without damaging the health of the consumer.


Introduction
Meat is an important source of nutrients and contribute considerable amounts in the intake of various nutrients that are essential for optimal growth and development of the body.
The essential fatty acids for the human body are the linoleic (ω-6, omega-6) and the alphalinolenic (ω-3, omega-3), necessitating therefore to be consumed through diet. These fat acids are synthesized in plant species and through of ruminal biohydrogenation, since the rumen microorganisms are able to insert carbon double bonds from the hydroxyl and form these compounds (Kaur, Chugh & Gupta, 2014).
It is desirable for the carcass to have minimal amounts of fat in the subcutaneous tissue Development, v. 9, n. 10, e1109108351, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8351 4 without a detrimental decrease of intramuscular fat. Lipids contribute significantly to the qualitative factors of the meat, as they are responsible for the smell and palatability of the meat, besides influencing the tenderness and nutritional value. However, it has been the subject of great concern regarding health related aspects associated with an increased risk of chronic diseases (Pickworth et al., 2011).
In general, the physicochemical composition of bovine meat is determined, mainly in the muscle Longissimus dorsi raw. Variations in the fatty acid profile in the meat are mainly related to the genetic group, slaughter weight, diet composition, finishing system, genders, use of additives or natural substances addition in the diet, methodology analysis, anatomical location of the evaluated cut, fat thickness, among others (Ornaghi et al., 2017;Rivaroli et al., 2016;Ito et al., 2012).
Performance may also interfere in an indirect way, where animals with greater weight gain tend to consume larger amounts of food and deposit more fat in the carcass. Animals with higher weight have a higher percentage of subcutaneous and intramuscular fat in the meat and can alter the profile of fatty acids. The percentage of unsaturated fatty acids, mainly monounsaturated is directly associated with total carcass fat (Pereira et al., 2012).
In addition to diet, breed, gender, age and weight at slaughter are important characteristics of beef production. While all of these factors can influence deposition of fat in the carcass, less is known about their effects on the fatty acid concentrations. In developing management that maximise the concentration in beef of fatty acids beneficial to human health, mainly concentrations of unsaturated fatty acids in beef, most research effort has been directed towards the effects of nutrition and there are relatively few reports on the effects of slaughter weight (Park et al., 2018).
In the same context, meat is eaten baked, boiled or fried. These preparation processes can denature the protein matrix of the meat and cause significant changes in its structure and composition. Loss of liquids initially occurs, promoting the concentration of nutrients and the incorporation of substances from the cooking medium. The heat can generate several modifications in the chemical components of the product as alteration in composition of fatty acids, contents of vitamins, content of cholesterol, contents and form of the proteins. The process of roasting, cooking or frying is essential to determine the flavor and juiciness of the meat. However, studies that report the effect of cooking on the fatty acids stability of meat are controversial (Kaur, Chugh & Gupta, 2014;Chávez et al., 2012) We hypothesised that pre-slaughter growth rate and consequently increased deposition of fat in the carcass therefore would also alter the composition of fatty acids in muscle. The Research, Society and Development, v. 9, n. 10, e1109108351, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8351 5 precocity will determine the amount of fat in the carcass. Animals with diets with high energy density, which allow greater gains, will reach the appropriate body composition more quickly.
Less precocious animals, with smaller gains, in turn, have physiologically younger carcasses, that is, leaner carcasses. The objectives of the present study were to determine the fatty acid composition of muscle from young bulls slaughtered at four target weights, as well as to evaluate the possible alterations in this profile by the cooking process.

Local, animals and diets
Forty 10 ± 2.2-month old crossbred young bulls (½ Brown Swiss + ½ Nellore) of initial body weight 219 ± 11.7 kg were used. The experiment lasted 187 days and the animals were slaughtered at approximately 17 months of age and had a mean BW of 475 ± 51.3 kg in a commercial slaughterhouse following the slaughtering standards of the State Inspection Service (SIE) of Brazilian Legislation.
The animals were slaughtered all on the same day and separated into four groups according to body weight (BW). Group 1 (T450): young bulls averaging 450 kg BW; group 2 (T469): young bulls averaging 469 kg BW; group 3 (T491): young bulls averaging 491 kg BW and group 4 (T513): young bulls averaging 513 kg BW.
After slaughter, the carcass was cooled (24 hours) in a chilling chamber at 4 ± 1 ºC. The

Cooking and preparation of samples
Samples were thawed in a chilling chamber (4 ± 2 ºC) trimmed with connective and adipose tissues and cut into a 10 x 5 cm rectangular section measuring 2.5 cm thick. To perform thermal processing, the samples were packed in aluminum foil and baked in an electric grill (Philco Jumbo Inox Grill, Philco SA, Brazil) preheated at 200 ºC until reaching the internal temperature of 72 ºC, this temperature was monitored with thermometer (Incoterm, 145 mm, Incoterm LTDA, Brazil) at five different points.

Determination of fatty acid composition
For the analysis of total lipids, the extraction with chloroform-methanol (1:2, v/v) was used according to the methodology described by Bligh and Dyer (1959). For the feed samples moisture correction was performed and hypersaturated NaCl solution was added to assist in the phase separation, as described in the methodology proposed by the same author.
For identification, the retention times of fatty acids were compared with those of the standard methyl esters (Sigma, St. Louis, MO). Retention times and percentages of peak areas were automatically calculated with Chronquest 5.0 software. The fatty acid compositions were expressed as a percentage. Each sample was analyzed in triplicate.
The operating parameters were as follows: Detector at 240 °C, injection point 230 °C, column at 165 °C for 18 min, programmed to increase at 4 °C min -1 up to 235 °C, with a duration of 14.5 minutes, the carrier gas was the hydrogen, flow rate of 1.2 mL min -1 and the gas makeup was the nitrogen at 30 mL min -1 , and injection divided at a ratio of 1:80.

Statistical analyzes
All variables under study were tested for normality, those with normal distribution were submitted to a variance analysis (ANOVA). The means were compared using the Tukey test at the 5% level of significance or 5% T-test (two treatments). The statistical program used was IBM SPSS Statistic ® version 21.0.

Fatty acid composition in the diets
Diet composition directly affects intake, BW and fat deposition in the carcass. The fat contents of the grains, although low, have high proportions of unsaturated fatty acids such as oleic acid (18:1n-9c), linolenic acid (18:3n-3 and 18:3n-6) and linoleic acid (18:2n-6) (Hall, Schönfeldt, & Pretorius, 2016), being 33.8, 0.3, 2.5 and 33.2%, respectively (Table 2). These fatty acids are precursors of polyunsaturated fatty acids (PUFA) in the meat and can not be biosynthesized by mammals, being consumed through vegetable oils, and are necessary for health (Gogus & Smith, 2010). In the case of human, he can still consume through the meat.
A large amount of saturated palmitic acid (20.4%) was found. This acid is commonly found in corn kernels and soybean meal. This fatty acid can be used as a substrate for subsequent synthesis of other monounsaturated fatty acids through the action of enzymes by stretching and desaturation in the rumen (Laliotis, Bizelis, & Rogdakis, 2010). Research, Society and Development, v. 9, n. 10, e1109108351, 2020 (CC BY 4. Note that 4.54% stearic acid is very important for the synthesis of unsaturated fatty acids by the introduction of a double bond between carbon atoms 9 and 10 and is catalyzed by the enzyme delta-9-desaturase. This enzyme is present in plants and animals, and converts stearic acid to oleic acid (Lee et al., 2016).
The composition of total lipids and fatty acids of the diet was determined, where the percentage of total lipids was of the order of 0.61% (Table 3). In general, the diet of cattle finished in feedlot presents between 2 and 3% of total lipids.

Fatty acid composition in the raw meat
The fat of the cattle meat presents great variation and the deposited amounts result from the energetic balance of the diet and metabolic requirements of the animal (Hocquette et al., 2010). The fatty acid composition of the meat is of great importance, especially the ω-3 and ω-Research, Society and Development, v. 9, n. 10, e1109108351, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8351 6 families, because they have numerous benefits to the health (Simopoulos, 2016). The table 4 shows the distribution of the main fatty acid classifications found in meat in this study.
There were no differences in the fatty acid profile between treatments with different termination BW (Table 4). Similar work was found in the literature (Dias et al., 2016).
However, also report decreasing linear variation of saturated fatty acids as the animals gained weight (Broncano et al., 2009;Serrano et al., 2007;Tejeda et al., 2008). The meat of cattle is rich in saturated fatty acids derived from the peculiar process of lipid digestion in ruminants. However, it is not all saturated fatty acids that are considered hypercholesterolemic. The most undesirable fatty acid would be myristic acid, which found an Development, v. 9, n. 10, e1109108351, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8351 11 average value of 3.34% in the meat of these animals, values considered within the standards for meat (Kaur, Chugh & Gupta, 2014). Palmitic acid has the lowest hypercholesterolemic effect, with an average value of 28.01%. And finally, stearic acid, with an average of 17.04% of the total saturated fatty acids in the meat, but is considered to be null, since it is a precursor of oleic acid in the body, not influencing blood cholesterol levels (Sokoła-Wysoczańska et al., 2018).
The most common MUFA is oleic acid, also observed in this work with an average value of 34.0%, followed by palmitolic acid with 3.72%. The higher levels of these fatty acids are found in animals with high dietary energy and fast fat deposition (Pickworth et al., 2011), according to this study.
The most representative PUFA in meat are linoleic, arachidonic, eicosapentaonoic and docosahexaenoic acids (Sokoła-Wysoczańska et al., 2018), together they were found in an average amount of 7.56% in meat. Higher values usually found are around 5% of polyunsaturated acids. However, lipolysis and biohydrogenation rates are lower in situations of high grain concentration in the diet, resulting in a greater escape of unsaturated fatty acids. As for polyunsaturated fatty acids, meat and fish oil are the only food sources of arachidonic acid and eicosapentaenoic acid, and values were found within normal standards for meat (Shingfield, Bonnet & Scollan, 2013).
There was no effect (P > 0.05) of the treatments on the percentages of MUFA and PUFA in the muscle LT with a mean of 41.7 and 8.3%, respectively, of the total quantified fatty acids.
The results obtained in this experiment demonstrated that the meat fat of these cattle was constituted in half by unsaturated fatty acids, being these beneficial to human health. The other half is composed of saturated fatty acids, in which a large part refers to the stearic fatty acid, which is considered neutral with respect to blood cholesterol levels (Lee et al., 2016).
The PUFA:MUFA ratio was not altered (P > 0.05) by treatments ( Likewise, the ratio ω-6:ω-3 did not present a difference (P > 0.05) between the treatments, with a mean ratio of 5.0. This ratio must be less than four parts of ω-6, for a part of ω-3. According Corpet (2011) this reason is important because of the risks of cancer and coronary diseases that an unbalanced diet provides.

Fatty acid composition in cooked meat
Brazilians, for the most part, consume fairly well meat, so the meat was still evaluated for the fatty acid profile after cooking and presented in Table 6. The treatments had no differences (P > 0.05), therefore the results were presented with the means of all the treatments.
The cooking in general, did not alter the composition of fatty acids when compared to raw meat (P > 0.05). Similar result to that found by Sarriés et al. (2009) in meat cooking (grilled at 140º C for 30 min) of crossbred heifers. Suggesting that the cooking causes minimal changes on the fatty acids of the meat, being beneficial for the conservation of the product, retarding the oxidation and development of unpleasant odors.
When the samples were analyzed cooked, it was observed that there was an increase in the amount of lipids (P > 0.05) (from 1.37 to 3.83%) due to the loss of water with the consequent concentration of the constituents (Table 7). Saturated fats solidify after cooking positively affecting the sensory characteristics of the meat. In addition to improving digestibility, reducing or eliminating pathogenic microorganisms, bringing to the food better sanitary conditions (Frank, Joo & Warner, 2016).
The loss of water during the process that can vary from 20 to 30% (Monteschio et al., 2017;Rivaroli et al., 2016). In this way, the fat concentration increases (Alfaia et al., 2010).
The percentage of saturated fatty acids was similar (P < 0.05) in raw and cooked meat.
The percentages of palmitic (28.4%) and stearic (17.3%) fatty acids in meat were the highest, as observed by other authors . The percentage of 18: 1n-9c (oleic) fatty acid was the highest among the monounsaturated fatty acids present in meat as observed by several authors .
The highest percentage was for SFA, followed by MUFA and PUFA. Likewise, the percentages of omega 3 and omega 6 fatty acids were not altered by the cooking of the meat.
The ratio between the percentages of PUFA:MUFA was not altered (P > 0.05) by the meat cooking process. The ratio of PUFA:MUFA was 0.20. Thus, the ratio observed in this experiment is low (HMSO, 1994). However, this ratio in the meat of finished feedlot animals is always between 0.10 and 0.20 .
The results of this experiment show that meat fat consists of 51% SFA, 41% MUFA and only 8% PUFA. For most saturated fatty acids it was stearic acid which is considered neutral for blood cholesterol levels (Shingfield, Bonnet & Scollan, 2013).
The ratio of the percentages between omega 6 and omega 3 was not altered (P > 0.05) by the meat cooking process. The ratio of omega-6 to omega-3 was 4.7. Therefore, the reason observed in this experiment is adequate (HMSO, 1994). The ratio in the meat of finished cattle in feedlot is always between 4 to 10 . In general, the ratio of omega-6 fatty acids to omega-3 fatty acids in pasture finishing cattle is more adequate because of the higher contribution of omega-3 fatty acids in these animals .

Final Considerations
In view of the above, the individual composition of the fatty acids was not altered by the difference in the BW of the animals and by the meat cooking process. The BW of the animals and cooking influenced the amount of total lipids, but the composition of fatty acids remained unchanged, concluding that the diferent BW and the heating used in this study were insufficient to cause important changes in the fat molecules and the meat can be consumed without damaging the health of the consumer.