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Studies were conducted to investigate: 1) desaturation of dietary trans-vaccenic acid (TVA, trans11-18:1) to the cis9,trans11-18:2 isomer of conjugated linoleic acid (9/11CLA), 2) effects of two conjugated linoleic acid isomers [9/11CLA or trans10,cis12-18:2 (10/12CLA)] and TVA on enzyme activities and mRNA abundance for lipogenic enzymes, and 3) regulation of stearoyl-CoA desaturase (SCD) gene transcription. In the first study, lactating mice were fed 3% linoleic acid (LA), or 2% LA plus 1% stearic acid (SA), 1% TVA, or 1% CLA mixture. Dietary TVA enriched the 9/11CLA content of carcass, liver, and mammary tissue of lactating mice. A similar enhancement of 9/11CLA also was observed in liver, but not carcass, of suckling pups nursing TVA-fed dams. The CLA mixture decreased mammary acetyl-CoA carboxylase (ACC) activity compared with other treatments. However, total fatty acid content of mammary tissue was reduced only when compared with TVA. In the second experiment, lactating mice were fed 3% canola oil (OA), or 2% OA plus 1% SA, 1% TVA, 1% 9/11CLA, or 1% 10/12CLA. Dietary TVA, 9/11CLA, and 10/12CLA decreased mRNA abundance for ACC and fatty acid synthase (FAS) in mammary tissue, suggesting each had the potential to reduce de novo fatty acid synthesis. However, only the CLA isomers decreased ACC activity in mammary tissue and concentration of medium-chain fatty acids (MCFA = 12:0+14:0+16:0) in milk fat. The 10/12CLA isomer caused greater reductions in MCFA and milk fat percentage than the 9/11CLA, indicating that 10/12CLA is the primary CLA isomer affecting lipid metabolism in the mammary gland. Dietary TVA, 9/11CLA, or 10/12CLA decreased SCD enzyme activity and mRNA abundance in mammary tissue. In study 3, mouse (COMMA-D/MME) and bovine (Mac-T) mammary epithelial cells were transfected with the putative promoter (600 bp) of SCD gene. The 9/11CLA reduced SCD gene transcription in mouse cells, but not bovine cells. Transcription, however, was reduced in both cell lines by 10/12CLA, linoleic acid, and linolenic acid. Thus, reduced SCD transcription in response to the CLA isomers in mouse mammary cells in vitro may provide an explanation for reduced SCD enzyme activity and mRNA abundance in mammary tissue when lactating mice were fed either of the CLA isomers. In contrast, stearic acid, oleic acid, and TVA did not affect SCD transcription. Although TVA did not reduce SCD transcription in mouse mammary cells in vitro, it did reduce SCD enzyme activity and mRNA abundance in mammary tissue when fed to lactating mice. The results suggested TVA may influence SCD mRNA processing or stability in the nucleus after transcription. Despite the reduction in SCD mRNA and enzyme activity, however, substantial quantities of TVA were desaturated to the 9/11CLA isomer when TVA was fed to lactating mice in the first two studies. Thus, dietary TVA provides an alternate supply of the anticarcinogenic 9/11CLA isomer in tissues. / Ph. D.

Milk fat composition determines specific rheological, sensory and physicochemical properties of dairy products such as texture, melting point, flavor, color, oxidation rates, and viscosity. Previous studies have shown that milkfats containing higher levels of long chain polyunsaturated fatty acids have lower melting points and decreased solid fat contents which leads to softer-textured products. An increased risk of higher oxidation rates can be a disadvantage of high levels of polyunsaturated fatty acids. Three different milkfat compositions were obtained through dietary manipulation of cows: high oleic content, high linoleic content and control milkfat. Ice cream and butter were processed from the treated and control milks. Butter and ice cream samples then were analyzed to measure differences in fatty acid profiles and firmness. High-oleic and high-linoleic milkfat had lower concentrations of saturated fatty acids, such as C 16:0. Conjugated linoleic acid content was increased in the high-linoleic milkfat. High-oleic milkfat resulted in a softer butter. Ice cream samples were analyzed to measure differences in viscosity, melting point, oxidation rate and sensory perception. Significant differences (P<0.05) were found in the fatty acid profiles of milkfat, ice cream mix viscosity, peroxide values of ice cream after 3 to 5 months of storage, butter color, and butter firmness. Sensory analyses included a scooping test at -18°C to detect differences in texture. A difference test was conducted to determine oxidation flavor differences between the three ice cream treatments at extended storage times. No significant differences were found in the scooping test or the oxidation flavor difference. Manipulation of the cow's diet increased the total amount of unsaturated fatty acids. It also influenced firmness of butter and behavior of peroxide values during extended storage of high-linoleic ice cream. / Master of Science

No / The effects of a conjugated linoleic acid (CLA) mixture of single isomers (50:50, w/w, cis9,trans11:trans10,cis12) and the individual isomers on (a) the production of resting and calcium ionophore stimulated 14C-eicosanoids and (b) the incorporation of 14C-arachidonic acid (AA) into membrane phospholipids of human saphenous vein endothelial cells were investigated. The CLA mixture and the individual isomers were found to inhibit resting production of 14C-prostaglandin F2a by 50, 43 and 40%, respectively. A dose dependent inhibition of stimulated 14C-prostaglandins was observed with the CLA mixture (IC50 100 ¿M). The cis9,trans11 and trans10,cis12 (50 ¿M) isomers individually inhibited the overall production of stimulated 14C-prostaglandins (between 35 and 55% and 23 and 42%, respectively). When tested at a high concentration (100 ¿M), cis9,trans11 was found to inhibit eicosanoid production in contrast to trans10,cis12 that caused stimulation. The overall degree of 14C-AA incorporation into membrane phospholipids of the CLA (mixture and individual isomers) treated cells was found to be lower than that of control cells and the cis9,trans11 isomer was found to increase the incorporation of 14C-AA into phosphatidylcholine. Docosahexaenoic acid, eicosapentaenoic acid and linoleic acid did not alter the overall degree of incorporation of 14C-AA. The results of this study suggest that both isomers inhibit eicosanoid production, and although trans10,cis12 exhibits pro-inflammatory activity at high concentrations, the CLA mixture maintains its beneficial anti-inflammatory action that contributes to its anti-carcinogenic and anti-atherogenic properties.

Consumer awareness of the link between dietary fats and health outcomes has led to increased demand for food products enriched with bioactive fatty acids (FA). Ruminant-derived fats, such as dairy fats, contribute significantly to the American diet and contain many unique beneficial FA, such as short- and medium-chain FA, n-3 FA, conjugated linoleic acids (CLA), vaccenic acid (VA), as well as odd-and branched-chain FA (OBCFA). Increasing these FA in dairy products by altering farm management practices, such as breed, lactation stage, and nutrition, may improve human health without a change to the diet. The overarching goal of this dissertation was to evaluate on-farm strategies to increase the content of bioactive FA in bovine milk. The first objective was to enrich milk fat with bioactive FA via supplementation with echium oil, a terrestrial oil rich in n-3 FA. Treatments were 1.5% and 3.0% dry matter as lipid encapsulated echium oil (EEO) which were compared to a control (no EEO). Milk fat contents of n-3 FA increased with EEO supplementation but the transfer of n-3 FA from EEO into milk fat was rather low (< 5%). In a subsequent trial, ruminal protection of EEO and post-ruminal release of EEO-derived FA was examined. EEO-derived FA were preferentially incorporated into plasma lipid fractions unavailable to the mammary gland. Moreover, fecal excretion of EEO-derived FA ranged from 7-14% of intake, and VA and CLA, the biohydrogenation and metabolism products of n-3 FA, increased in milk and feces with EEO supplementation. Therefore, lipid-encapsulation provided inadequate digestibility and low transfer efficiency of n-3 FA into milk. The second objective was to compare the bacterial community structure and unique bioactive FA in bacterial membranes and milk fat between Holstein (HO), Jersey (JE), and HO x JE crossbreeds (CB) across a lactation. Lactation stage had a prominent effect on rumen bacterial taxa, with Firmicutes being most abundant during early lactation. The FA composition of bacterial cells was affected by both lactation stage and genetics, and OBCFA in bacterial cells were positively correlated with several bacteria of the Firmicutes phylum. HO and CB exhibited greater contents of various bioactive FA in milk than JE. The highest content of all bioactive FA occurred at early lactation, while OBCFA were highest at late lactation. The third objective was to determine the effects of grazing a monoculture vs. a diverse pasture on rumen bacterial and protozoal taxa, their membrane FA composition, and milk FA. Microbial communities shifted in response to grazing regime accompanied with changes in their membrane FA profiles. Rumen microbiota from cows grazing a diverse pasture had higher contents of n-3 FA and VA, but lower contents of OBCFA. Microbial membrane FA correlated with microbial taxa, the contents of ALA and n-3 FA were positively correlated with the bacterial genus Butyrivibrio and the protozoal genus Eudioplodinium. Milk contents of CLA and n-3 FA increased when cows grazed a diverse pasture, while grazing a monoculture led to greater milk contents of OBCFA. In conclusion, grazing cows on a diverse pasture, when compared to genetic effects and lipid supplementation, was the most efficacious strategy to increase the content of bioactive FA in milk.

Thesis submitted in fulfilment of the requirements for the degree of Magister Technologiae: Agriculture in the Faculty of Applied Sciences at the Cape Peninsula University of Technology / Conjugated linoleic acid (CLA), a fatty acid (FA) present in the meat and milk of ruminant animals, is considered a functional nutrient for humans. The interest in CLA is attributed to its many health benefits, such as having anti-carcinogenic, anti-atherogenic, anti-diabetic and anti-adipogenic effects. Dairy products are a rich natural source of CLA, and preliminary research indicates that the levels in milk can vary based on cattle breed and feeding system. The Fleckvieh is a popular dual-purpose breed recently introduced to the Western Cape. It is used in crossbreeding programs with Holstein and Jersey herds to increase fertility and beef production. Holstein and Jersey cattle are the two most common South African dairy breeds, but little information is available on the effect of crossbreeding on FA content and CLA levels in the milk. The primary objective of this study was to compare milk FA composition and CLA content of these two dairy breeds and their respective Fleckvieh crosses. A second objective was to investigate the effect of lactation stage on CLA levels. Jersey (J) and Fleckvieh x Jersey (F×J) cows were kept in a pasture-based system (PBS) for the duration of the study. Holstein (H) and Fleckvieh x Holstein (F×H) cows were housed in a feedlot system and fed a total mixed ration (TMR) for the duration of the study. The FA and CLA content of feeds from these two feeding systems were also analysed and compared. All cows used in the study were housed at the Elsenburg Research Farm of the Western Cape Department of Agriculture. Milk samples were collected every 35 days from the cows in each feeding group, starting 10 days after calving. Samples were kept in a freezer at -20 °C until laboratory analyses. The total number of milk samples collected was 1044. The milk FA composition and CLA in particular were determined by gas chromatography. Differences between groups were statistically analysed by two-way repeated measures of analysis of variance (ANOVA). Results show that milk CLA levels are higher in Fleckvieh-crossbred cows when compared to purebred cows. The higher CLA content of milk from Fleckvieh crossbred cows demonstrates the feasibility of using Fleckvieh bulls in South African crossbreeding programs, and are also an indication that genetic selection for increased CLA content is possible. The analysis of lactation stage showed that milk CLA is higher during late lactation. A comparison of feed samples from the two feeding systems revealed that pasture feeding resulted in higher omega-3 FA in milk. Key words: Conjugated linoleic acid, milk fatty acids profile, diet, breed, health benefits, Fleckvieh, Holstein, Jersey, diet, pasture based system, total mixed ration system,

Três experimentos foram conduzidos com o objetivo de avaliar os efeitos do fornecimento de baixos teores de óleo de peixe em substituição parcial ao óleo de soja, sobre o consumo de matéria seca (CMS), produção e perfil de ácidos graxos do leite de ovelhas, ganho médio diário de peso corporal (GMD), características da carcaça e composição de ácidos graxos da carne de cordeiros, digestibilidade dos nutrientes, características de fermentação ruminal e metabolismo ruminal dos ácidos graxos. Os tratamentos consistiram de uma dieta controle (CONT), sem adição de óleo; e 4 dietas adicionadas com 4,0% de óleo, consistindo de 0,0% (0P); 0,25% (25P); 0,50% (50P) e 0,75% de óleo de peixe (75P), com o óleo de soja completando o teor de 4,0% de óleo adicionado (% MS). No Experimento I a dieta controle foi composta por 70% de concentrado e 30% de volumoso, nos Experimentos II e III a dieta controle foi composta por 90% de concentrado e 10% de volumoso. Experimento I: Foram utilizadas 50 ovelhas, distribuídas em delineamento experimental de blocos completos casualizados. Verificouse aumento linear na produção de leite das ovelhas e no GMD das crias com a inclusão de óleo de peixe nas dietas. As concentrações de ácido vacênico, CLA C18:2 trans-10, cis-12, ácido eicosapentaenóico (EPA) e ácido docosahexaenóico (DHA) também aumentaram linearmente com os teores crescentes de inclusão de óleo de peixe. Experimento II: Foram utilizados 50 cordeiros, distribuídos em delineamento experimental de blocos completos casualizados. O CMS expresso em % do peso corporal (PC) e em g/kg de PC0,75 aumentou linearmente com os teores crescentes de inclusão de óleo de peixe, o que resultou em aumento linear no GMD dos cordeiros. A concentração de ácido esteárico reduziu com os teores crescentes de substituição do óleo de soja pelo óleo de peixe. Verificou-se aumento linear na concentração de ácido vacênico à medida que o óleo de peixe foi adicionado à dieta. Em comparação ao tratamento controle, os animais alimentados com as dietas contendo óleo de peixe apresentaram maior concentração de CLA C18:2 cis-9, trans-11 na carne. Experimento III: Foram utilizados cinco borregos, canulados no rúmen e no duodeno, distribuídos em delineamento experimental quadrado latino 5 x 5. A suplementação com as fontes de óleo reduziu a digestibilidade da PB. A concentração de acetato, butirato e dos ácidos graxos de cadeia curta (AGCC) totais foi maior no conteúdo ruminal dos animais alimentados com a dieta controle em relação aos das dietas contendo óleo, como conseqüência, o pH ruminal destes animais foi inferior. O fluxo duodenal de C18:1 trans-11 e CLA C18:2 cis-9, trans-11 foi superior para os animais que receberam gordura suplementar. Observou-se aumento linear no fluxo duodenal de ácido C18:1 trans-11 em resposta a inclusão de óleo de peixe nas dietas. A inclusão de 0,75% de óleo de peixe na dieta misturado à 3,25% de óleo de soja mostrou-se como a melhor alternativa avaliada. / Three trials were conducted to evaluate the effects of small amounts of fish oil supply in partial replacement of soybean oil on dry matter intake (DMI), lactation performance and milk fatty acid composition of ewes, growth, carcass characteristics, and on meat fatty acid composition of feedlot lambs, some rumen constituents, and ruminal fatty acid metabolism. Treatments consisted of a control diet (CONT), and 4 diets with 4% added fat consisting of 0.0% (0FO), 0.25% (25FO), 0.50% (50FO) and 0.75% (75FO) fish oil with soybean oil providing the balance of 4% added fat. In trial I the control treatment consisted of 30:70 ratio of forage to concentrate (DM basis). In trials II and III the control treatment consisted of 10:90 ratio of forage to concentrate (DM basis). Trial I: Fifty Santa Inês ewes were penned individually and used in a randomized complete block design. Milk production and preweaning ADG of lambs increased linearly when fish oil replaced soybean oil. Vaccenic acid, CLA trans-10, cis-12, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased linearly with fish oil inclusion. Trial II: Fifty Santa Inês ram lambs were penned individually and used in a randomized complete block design. DMI (% of BW and g/kg of BW0,75) increased linearly when fish oil replaced soybean oil, as consequence ADG also increased. Stearic acid concentration decreased and vaccenic acid increased with fish oil inclusion. CLA C18:2 cis-9, trans-11 showed higher concentration in meat of animals fed diets containing fish oil compared to the control diet. Trial III: Five ram lambs cannulated in the rumen and proximal duodenum were assigned in a 5 x 5 Latin Square design. Soybean oil and fish oil supplementations decreased CP digestibility. Ruminal concentrations of acetate, butyrate and total SCFA were higher for animals fed the control diet. Ruminal pH was lower for animals fed the control diet compared to diets with oils. Duodenal flow of C18:1 trans-11 and CLA C18:2 cis-9, trans-11 was greater for diets containing supplemented oils. C18:1 trans-11 flow to the duodenum increased linearly with fish oil inclusion.The inclusion of 0.75% of fish oil in the diet mixed with 3.25% soybean oil was the best alternative evaluated.

Os objetivos deste experimento foram os de realizar levantamento exploratório da produção, composição e perfil de ácidos graxos do leite de búfalas e dos alimentos utilizados em cinco fazendas da região de Sarapuí e Pilar do Sul, no Estado de São Paulo. Foram coletadas amostras mensais de leite de oito búfalas por fazenda e de alimentos durante os meses de abril a novembro de 2002. Das cinco fazendas, uma explorava sistema de confinamento total e quatro usavam sistemas de produção a pasto com suplementação volumosa no inverno (silagem de gramíneas e cana-de-açúcar) e concentrado (resíduo de cervejaria ou mistura comercial) o ano todo.Três propriedades realizavam duas ordenhas diárias, e as demais apenas uma. Os teores de gordura, proteína e lactose variaram de 5,4 a 8,6%, 3,7 a 4,9% e 4,5 a 5,6%, respectivamente, valores normais para bubalinos. Os teores de gordura e de proteína aumentaram ao longo da lactação, enquanto o teor de lactose acompanhou a curva de lactação. O teor de nitrogênio uréico no leite variou entre 5,6 e 27,3 mg/dL, com valor médio em todas as fazendas de 15,9 mg/dL, inferior ao observado na literatura para bubalinos. Do total de ácidos graxos na B. decumbens o ácido linoléico variou de 18,2% no inverno para 19,9% no verão e o ácido linolênico de 20,8% no inverno para 31,4% no verão. A B. ruziziensis apresentou teor de ácido linoléico 17,7% no inverno e 19,4% no verão, enquanto o ácido linolênico variou de 50,2% no inverno para 45,6% no verão. Observou-se grande variação individual no teor de CLA no leite de bubalinos (0,31-3,42%). Nos animais a pasto ou com suplementação volumosa de gramíneas frescas a variação foi maior (0,44 a 3,31%) que nos animais confinados (0,31 a 1,74%). Os teores obtidos de CLA no verão foram em média mais elevados (38,6%), que no inverno, nos rebanhos em pastejo. A Análise de Componentes Principais confirmou a correlação positiva entre os ácidos graxos de cadeia ímpar e de cadeia ramificada e alta correlação entre os ácidos capróico, caprílico e cáprico. Também indicou correlação negativa entre os ácidos graxos de cadeia longa com os de cadeia curta, média, ímpar e ramificada. O teor dos ácidos graxos hiper-colesterolêmicos (ácidos láurico, mirístico e palmítico) diminuiu à medida que houve elevação do teor de ácidos graxos de cadeia longa no leite. A atividade da enzima &#8710;9-dessaturase, medida indiretamente (relação produto x substrato), foi maior em animais que receberam resíduo de cervejaria em menor quantidade ao longo do ano. / The objective of this study was to determine milk production, composition and fatty acids profiles in five buffalo farms in the Sarapui and Pilar do Sul counties, in the Southeast region of the State of Sao Paulo. Monthly feed and milk (from eight animals per farm) samples were collected from April to November 2002. In one farm animals were housed in total confinement and were fed a TMR ration; wet brewers grains and a commercial grain mix and summer pasture and a mixture of grass silage plus chopped sugar cane during winter were offered in the remaining farms. Animals were milked twice daily in three farms. Milk fat, protein and lactose contents varied from 5.4 to8.6%, 3.7 to 4.9% and 4.5 to 5.6%, respectively. Milk fat and protein contents increased as the lactation progressed. Milk urea nitrogen showed a large variation among farms (5.6 to 27.3 mg/dL). The content of linoleic and linolenic acids in B. decumbens varied from18.2 and 20.8% (winter) to 19.9 and 31.4% (summer) and in B. ruziziensis varied from 17.7 and 50.2% (winter) to 19.4 and 45.6% (summer). "Milk CLA content showed a large variation among animals (0.31 to 3.42%). Pasture fed or green chopp supplemented animals showed a larger variation (0.44 to 3.31%) than TMR fed animals (0.31 to 1.74%). Milk CLA content was higher (39%) during summer than in winter, in pasture fed animals. Principle Component Analysis confirmed the positive correlation between odd chain and side chain fatty acids and a high correlation among caproic, caprilic and capric acids. It also showed a negative correlation between long chain fatty acids and short and medium chain and odd and side chain fatty acids. Milk hiper-colesterolemic fatty acids (lauric, miristic and palmitic acids) content decreased as the long chain fatty acids did increased. The indirectly measured Delta 9 dessaturase activity was higher in animals being offered small amounts of wet brewers grains throughout the lactation.

Ácidos graxos conjugados (AGCs) é o termo geral para descrever os isômeros posicionais e geométricos dos ácidos graxos poliinsaturados com duplas ligações conjugadas. Inúmeros efeitos benéficos para a saúde como: anti-cancerígeno, anti-aterogênicos, anti-adipogênicos e anti-inflamatórios, tem sido atribuídos ao consumo dos AGCs. Entretanto, estudos sobre os efeitos dos AGCs no organismo ainda são inconclusivos e por isso o interesse em pesquisas visando a sua participação em processos fisiológicos. O objetivo deste estudo foi avaliar em ratos o efeito dos isômeros conjugados do ácido linoleico (9cis, 11trans e 10trans, 12cis) sobre o perfil lipídico tecidual e sua influência sobre parâmetros bioquímicos em processos oxidativos. Não foi possível detectar a atividade antioxidante in vitro dos CLAs. Os resultados obtidos demonstraram que o FFA-CLA foi capaz de reagir apenas com o radical DPPH. No experimento in vivo uma mistura comercial dos isômeros (9cis, 11trans e 10trans, 12 cis) foi utilizada como fonte de CLAs, e a influência da suplementação desses isômeros, foi avaliada e comparada com um grupo controle suplementado com água e com grupos experimentais suplementados com óleo de soja. O primeiro experimento foi realizado com animais Wistar saudáveis e teve duração de 40 dias, as amostras de ácidos graxos livres de CLAs, (FFACLAs) e óleo de soja foram fornecidas aos animais por meio de entubação orogástrica nas concentrações de 1%, 2% e 4% em relação ao consumo diário de dieta, o grupo controle recebeu 1% de água. A suplementação da dieta dos animais com os CLAs leva ao aumento nos níveis de triglicérides, mas não interfere nos parâmetros de estresse oxidativo, embora haja incorporação dose-dependente nos tecidos hepático, muscular e adiposo, não foram observadas alterações no volume das células adiposas, e na área e diâmetro do tecido muscular. No segundo experimento, com duração de 21 dias, ao avaliar o efeito da suplementação na dose de 2% de CLAs em ratos Wistar induzidos a peroxidação, pelo tratamento com tetracloreto de carbono. Pôde-se observar efeitos hepatoprotetor, dos CLAs atribuídos a sua prevenção na peroxidação lipídica e ao aumento da atividade das enzimas catalase (CAT), glutatina redutase (GR) e glutationa reduzida (GSH). / Conjugated fatty acids (CFAs) is the general term to describe positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds. Many beneficial health effects such as anti-cancer, anti-atherogenic, anti-adipogenic and anti-inflammatory, has been attributed to the consumption of the CFAs. However, studies on the effects of the CFAs in the body are still inconclusive and therefore the interest in research aimed at their participation in processes physiological. The objective of this study was to evaluate in rats the effect of conjugated linoleic acid isomers (9cis, 11trans and 10trans, 12cis) on lipid profile tissue and its effect on biochemical parameters in oxidative processes. It was not possible to detect the in vitro antioxidant activity of CLAs. The results showed that the free fatty acids of CLAs (FFA-CLAs) was able to react only with the DPPH radical. In in vivo experiment a commercial mixture of isomers (9cis, 11trans and 10trans, 12cis) was used as a source of CLAs and the influence of supplementation of these isomers was evaluated and compared with a control group supplemented with water and experimental groups supplemented with soybean oil. The first experiment was conducted with healthy Wistar and lasted 40 days, samples of FFA-CLA and soybean oil were delivered to animals via orogastric intubation at concentrations of 1%, 2 % and 4% in relation to daily diet, the control group received 1% water. Supplementing the diet with CLAs leads to increased levels of triglycerides, but does not interfere with oxidative stress parameters, although there is a dose-dependent incorporation into liver tissue, muscle and fat, no changes were observed in the volume of fat cells, and in the area and diameter of muscle tissue. In the second experiment, lasting 21 days, to evaluate the effect of supplementation at a dose of 2% of CLAs in Wistar, tha peroxidation induced by treatment with carbon tetrachloride. Could be observed hepatoprotective effects, attributed to the CLAs prevention lipid peroxidation and increased activity of the enzymes catalase (CAT), glutathione reductase (GR) and glutathione reduzida (GSH).

Os ácidos linoléicos conjugados (CLAs) consistem de um grupo de isômeros geométricos e posicionais do ácido linoléico aos quais tem sido atribuídos efeitos anticarcinogênico, antidiabético, antiaterogênico e modulador da composição corporal. As principais fontes naturais de CLA são o leite e a carne de ruminantes, uma vez que microorganismos ruminais são capazes de formar CLAs e seus precursores como intermediários da biohidrogenação. Para sua identificação e quantificação por cromatografia gasosa (CG) deve se tomar cuidado ao decidir um procedimento apropriado de metilação, a fim de evitar a isomerização dos CLAs. Dessa forma, o objetivo do presente trabalho foi de avaliar criticamente metodologias analíticas para caracterizar os isômeros conjugados c-9, t-11 e t-10, c-12 do ácido linoléico, identificando o melhor método para a esterificação e a melhor programação por cromatografia gasosa para a separação, identificação e quantificação dos CLAs através de sua análise em suplementos, cortes bovinos e laticínios. Para tanto, foram empregadas as técnicas de esterificação ácida com trifluoreto de boro metanólico, esterificação alcalina com metóxido de sódio metanólico e uma esterificação mista usando a combinação dos dois catalisadores na metilação de uma amostra comercial de suplemento de ácido linoléico conjugado na forma de triacilglicerol, o Tonalin® CLA TG 80, da Cognis. Os ésteres metílicos foram identificados sob três condições cromatográficas CLA01, CLA02 e CLA03. Também foram realizadas quantificações dos isômeros c-9, t-11 e t-10, c-12 CLA no Tonalin® CLA TG 80 e FFA 80 através de ressonância magnética nuclear do carbono 13 (13C-RMN). Os resultados obtidos permitiram decidir pelo emprego da técnica de esterificação alcalina, seguido da análise cromatográfica pelo método CLA03 para análise de cinco cortes bovinos fracionados em músculo e capa de gordura, creme de leite, iogurte integral e três tipos de queijo. O método de esterificação alcalina, seguido de separação por CG pelo método CLA03 mostrou-se o mais adequado para uma quantificação segura do perfil de ácidos graxos de alimentos que contenham os isômeros conjugados do ácido linoléico, uma vez que os resultados obtidos concordam com a literatura atual. / Conjugated linoleic acids (CLAs) are a group of geometric and positional isomers of linoleic acid which have been attributed to present anticarcinogenic, antidiabetic, antiaterogenic and body composition modulation effects. Major natural sources of CLA are ruminants milk and meat, since rumen microorganisms are able to produce CLAs and their precursors as intermediates of biohydrogenation. Before identification and quantification by gas chromatography (GC), the methylation procedure should be carefully decided to avoid isomerization of CLAs. Thus, the objective of this study was to critically evaluate analytical methods for characterizing conjugated linoleic acid isomers c-9, t-11 and t-10, c-12, by identifying the best method for esterification and the best gas chromatography programming for separation, identification and quantification of CLAs through quantification of CLAs in supplements, beef and dairy products. In order to accomplish this objetive, the techniques of acid esterification with boron trifluoride methanol, alkaline esterification with methanolic sodium methoxide and mixed esterification using a combination of the two catalysts were employed in the methylation of a commercial sample of conjugated linoleic acid supplement in triacylglycerol form, the CLA Tonalin® TG 80, from Cognis. The methyl esters were identified in 3 chromatographic conditions CLA01, CLA02 and CLA03. CLA isomers c-9, t-11 and t-10, c-12 were also quantified in CLA Tonalin® TG 80 and FFA 80 by carbon 13 nuclear magnetic resonance (13C-NMR). The results indicated the alkaline esterification technique followed by chromatographic analysis by CLA03 method as the best method for analyzing five cuts of beef fractionated in muscle and fat layer, cream, full yoghurt and three types of cheese. The alkaline esterification method followed by GC separation method CLA03 proved to be the most suitable for safe quantification of fatty acid profile in foods that contain conjugated linoleic acid isomers, once the results agreed with the data available in the current literature.