Conjugated linoleic acid in canadian dairy and beef products.

Conjugated linoleic acid (CLA) is a dietary fatty acid produced by ruminant animals and exhibits promising beneficial health effects. CLA has been identified as having anticancer, antiatherogenic, and body fat reducing effects. There are no published data on the CLA content of Canadian beef and dairy products. The purpose of this study was to assess the level and type of CLA isomers found in commercial beef and dairy products. Under the present experimental conditions only the Delta9c,11t-18:2 isomer was detected. Other minor isomers, which may be present, were not determined by the method used in this study. Levels of CLA ranged between 1.2 and 6.2 mg/g of fat or 0.001-4.3 mg/g or mg/mL of sample. On the basis of a usual serving size, levels of CLA ranged between 0.03 and 81.0 mg per serving. It is concluded that the Delta9c,11t-18:2 isomer is present in dairy and beef products and levels when expressed per gram of fat are not significantly different among products.     

Conjugated linoleic acid isomers in partially hydrogenated soybean oil obtained during nonselective and selective hydrogenation processes

Partially hydrogenated soybean oil samples were collected during selective and nonselective hydrogenation processes. The formation of conjugated linoleic acids (CLAs) during hydrogenation was greatly dependent on the types and duration of hydrogenation processes. During hydrogenation processes, CLA contents increased initially. After reaching maximum CLA content, the content decreased during hydrogenation. Selective hydrogenation was much more favorable for the formation of conjugated linoleic acids. With nonselective hydrogenation process, the total CLA content was a maximum (9.06 mg total CLA/g oil) at 35 min. However, with the selective hydrogenation process, the total CLA content was a maximum (98.27 mg total CLA/g oil) at 210 min. The CLA contents in some of the tested selectively hydrogenated soybean oils were among the highest ever reported in foods.     

Conjugated linoleic acid isomers differ in their free radical scavenging properties

Conjugated linoleic acid (CLA) isomers were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH(*)) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR measurements confirmed that both c9,t11-CLA and t10,c12-CLA directly reacted with and quenched DPPH radicals, whereas spectrophotometric analysis demonstrated that c9,t11-CLA and t10,c12-CLA differed in their kinetic and thermodynamic properties in reacting with DPPH radicals. t10,c12-CLA was shown to exhibit a greater initial velocity in CLA-DPPH radical reactions at levels of 2.5-80 mg/mL, and c9,t11-CLA scavenged more DPPH radicals at steady state. Similar dose and time relationships were observed for both isomers. In addition, a mixture of c9,t11- and t10,c12-CLA isomers demonstrated a greater initial velocity in quenching DPPH radicals than either isomer alone on the same concentration basis, suggesting that a synergistic effect between CLA isomers existed in their reactions with DPPH radicals. These results support the conclusion that individual CLA isomers differ in their biological actions and indicate that interaction(s) between isomers may contribute to their beneficial effects.     

Conjugated linoleic acids alter the fatty acid composition and physical properties of egg yolk and albumen

Effects of dietary conjugated linoleic acids (CLAs) and docosahexaenoic acid (DHA) on the fatty acid composition of different egg compartments after storage were studied. Four dietary treatments [supplemented with safflower oil (SAFF, control group), DHA, CLAs plus DHA (CAD), and CLAs alone] were administered to Single Comb White Leghorn (SCWL) laying hens. Eggs from the different treatment groups were collected and stored for 10 weeks at 4 degrees C before analysis. Fatty acids from the yolk (yolk granules and plasma), egg albumen, and vitelline membrane were analyzed by gas chromatography. The yolk of eggs from hens given CLAs had significantly higher amounts of saturated fatty acids, typically 16:0 and 18:0, but lower amounts of polyunsaturated fatty acids (PUFAs) compared to eggs from the control group (SAFF). CLA content was highest in the yolk and present in both neutral and polar lipids, with the greatest concentrations in neutral lipids. DHA was incorporated mainly into yolk polar lipids. Lipids in yolk plasma and granules contained similar amounts of CLAs. The fatty acid compositions of vitelline membrane and egg albumen mirrored that of the egg yolk. CLA supplementation resulted in hard and rubbery yolks when compared to hard-cooked eggs from the control group. This study showed that feeding CLAs to hens led to accumulation of the isomers in polar and neutral lipids of the egg yolk and that these isomers migrated into egg albumen. Because the sensory properties of hard-cooked eggs were negatively affected by the enrichment of a mixture of CLA isomers in this study, further research should be conducted to evaluate how the different isomers alter the properties of egg yolk and albumen so that the quality of designed eggs containing CLAs and DHA can be improved.     

Conjugated linoleic acid content and organoleptic attributes of fermented milk products produced with probiotic bacteria

The effect of probiotic bacteria on the formation of conjugated linoleic acid (CLA), microbial growth, and organoleptic attributes (acidity, texture, and flavor) of fermented milk products was determined. Four probiotic bacteria, Lactobacillus rhamnosus, Propionibacterium freudenreichii subsp. shermanii 56, P. freudenreichii subsp. shermanii 51, and P. freudenreichii subsp. freudenreichii 23, were evaluated individually or in coculture with traditional yogurt cultures (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus). The lipid source was hydrolyzed soy oil. L. rhamnosus, in coculture with yogurt culture, resulted in the highest content of CLA. Growth and CLA formation of propionibacteria were enhanced in the presence of yogurt cultures. Texture and flavor attributes of fermented milks produced with propionibacteria were significantly different than the fermented milks processed with yogurt cultures. The fermented milks processed with probiotic bacteria in coculture with yogurt cultures demonstrated similar acidity, texture, and flavor as the fermented milk produced with yogurt cultures.     

Conjugated linoleic acid, cis-9,trans-11, is a substrate for pulmonary 15-lipoxygenase-1 in rat

The objective of this study was to determine whether two of the major conjugated linoleic acid (CLA) isomers, cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12), are possible substrates for pulmonary 15-lipoxygenase-1 (15-LOX-1) and, therefore, they are also involved in the production of 13(S)-hydroxyoctadecadienoic acid [13(S)-HODE] in biological systems. 13(S)-HODE, a major bioactive metabolite of linoleic acid, is an important intracellular signal agent and is involved in cell proliferation and differentiation in various biological systems. Nordihydroguaiaretic acid (NDGA), a known LOX inhibitor, was used as a control for measuring 15-LOX-1 enzyme activity. It was found that c9,t11-CLA was 25% as active as linoleic acid as a substrate for 15-LOX-1; however, t10,c12-CLA was not a substrate for 15-LOX-1 as measured by 13(S)-HODE production. The authenticity of the production of 13(S)-HODE from c9,t11 as a substrate was established by isolation and cochromatography with pure standard on HPLC using non-radioactive and [14C]-c9,t11-CLA.     

Conjugated linoleic acid-induced fatty liver can be attenuated by combination with docosahexaenoic acid in C57BL/6N mice

We investigated the effect of dietary combination of conjugated linoleic acid (CLA) and docosahexaenoic acid (DHA) to attenuate CLA-induced fatty liver in C57BL/6N mice. Mice were fed semisynthetic diets that contained either 6% high linoleic safflower oil (HL-SAF), 4% HL-SAF + 2% CLA, or 3.5% HL-SAF + 2% CLA + 0.5% DHA for 4 weeks. This 4 week feeding of CLA showed hepatic lipid accumulation concomitant with the decrease in adipose tissue weight in mice. However, 0.5% supplementation of DHA to the CLA diet could alleviate fatty liver without decreasing the antiobesity effect of CLA. The CLA diet promoted fatty acid synthesis in the liver, but DHA supplementation significantly attenuated the increase in enzyme activity induced by CLA. On the other hand, serum adipocytokines, leptin and adiponectin, were drastically decreased by CLA feeding, and DHA supplementation did not affect those levels. These results show that DHA supplementation to the CLA diet can attenuate CLA-induced fatty liver through the reduction of hepatic fatty acid synthesis without affecting adipocytokine production in C57BL/6N mice.     

日粮共轭亚油酸对黄羽肉鸡腹脂沉积的影响及机理研究

选择1日龄黄羽肉鸡60只,随机分成2组。在实验组中添加3%共轭亚油酸(conjugated linoleic acid,CLA),对照组日粮中添加3%的食用菜籽油。49日龄屠宰,采集腹部脂肪组织。用RT-PCR方法,以β-actin为内标,相对定量测定腹脂中鸡生长激素受体（cGHR）、胰岛素样生长因子-1（cIGF-1）、胰岛素样生长因子Ⅰ型受体（cIGF-ⅠR）、过氧化物增殖剂活化受体γ（cPPARγ）、脂联素（cAdiponectin）及其Ⅰ型受体（cAdipoⅠR）的mRNA丰度。结果显示：CLA处理使肉鸡的腹脂沉积下降了20.93%（P<0.05）,分别使腹脂中鸡cGHR mRNA和cPPARγ mRNA降低了24.74%（P<0.05）和66.52%（P<0.01）;而对cIGF-1、cIGF-ⅠR、cAdiponectin、cAdipoⅠR 基因表达无显著影响（P>0.05）;数据提示：CLA降低肉鸡脂肪沉积的作用可能通过GH途径和PPARγ通路介导,而与IGF-1和（或）GH-IGF-1途径、Adiponectin 的作用无关。     

Partial inhibition of biohydrogenation of linoleic acid can increase the conjugated linoleic acid production of Butyrivibrio fibrisolvens A38

Butyrivibrio fibrisolvens A38, one of the most active rumen bacteria in conjugated linoleic acid (CLA) production, was characterized in vitro. Previous findings that some inhibitory levels of substrate for biohydrogenation (BH) by B. fibrisolvens A38 resulted in more CLA accumulation led to a prediction that partial inhibition of BH could increase ruminal CLA production. The inhibitory conditions for bacterial growth were less effective on the isomerization step than on the following reduction step. Linoleic acid (LA) was inhibitory not only to cell growth but also to LA hydrogenation, and this effect was greater at high concentrations. The reduction step, converting CLA to hydrogenated products (trans-C18:1 and C18:0), was significantly inhibited, and more CLA accumulated during aerobic incubation when LA was added along with a glycolytic inhibitor, iodoacetate (IAA), to cells that were pre-adapted to LA (1 g/OD at 600 nm/L, P < 0.05). Monensin was more inhibitory than IAA to cell growth but less effective for CLA accumulation. Rumen fluid in the culture medium appeared to activate BH even in an aerobic condition, resulting in a lower CLA level than the control group (P < 0.05). Because the isomerization and reduction steps are coupled reactions in BH of most hydrogenating bacteria including B. fibrisolvens A38 cells, both positive and negative modulations of the reduction steps could be key determinants for CLA accumulation in the rumen.     

Differences in acid tolerance during the early life stages of three strains of brook trout,Salvelinus fontinalis

Brook trout, Salvelinus fontinalis, embryos and fry from three sources (an acidic watershed in Kejimkujik Park at pH 4.7 to 5.3, a neutral watershed at pH 7, a hatchery at pH 7) were exposed separately to lethal and sublethal levels of acidity (pH 7.0, 5.2, 4.7, 4.3, 3.9), beginning at fertilization. Significant differences in mortality between the strains at low pH were observed and these suggested a genetic component to acid tolerance. Mortality in the strain from the acidic watershed was the lowest, followed by the second wild strain. Survival in both wild strains at low pH was much better than survival in hatchery embryos. These differences in survival at sublethal acidity (4.7 to 7.0) were principally the result of high mortality shortly after fertilization. After this period, survival stabilized. Only at pH 4.3 did substantial mortality occur at hatching. The early embryonic stage therefore appears to be the most susceptible to sublethal acid stress in brook trout. Hatchery strain embryos were also introduced at the eyed stage at 213 degree-days. Subsequent survival of this group was better at low pH than that of hatchery embryos introduced at fertilization, thereby indicating an early or cumulative deleterious effect. Higher acidity retarded hatch in all cases. The time to 50% hatch was delayed by 1.2 degree-days with each increase of 1 μM H⁺.     

Positional distribution of conjugated linoleic acid in triacylglycerol of Saccharomyces cerevisiae

Saccharomyces cerevisiae was cultivated in the presence of cis-9,trans-11 or trans-10,cis-12 isomers of free conjugated linoleic acid (CLA), and the effects of the isomers on the regioisomerisms of triacylglycerol (TAG) of the yeast were elucidated. Both isomers constituted about 34% of all fatty acids and increased drastically the number of different TAG species. Nearly all of the species contained CLA in at least one sn-position. In the most abundant species analyzed (20% of total species), the cis-9,trans-11 isomer appeared in combination with monounsaturated fatty acids (C16:1, C:18:1) whereas trans-10,cis-12 isomer was most frequently present with a medium chain fatty acid (C10:0 or C12:0) in the sn-2 position and C16:0 in one of the end positions (14% of total species). With either isomer, the amount of TAG species in which CLA encompassed all sn-positions was ca. 4%. Thus, S. cerevisiae can be used to produce edible single cell oil characterized by very heterogeneous distribution of CLA among the different TAG species.     

Quantitative determination of linoleic acid in infant formulas by gas chromatography

A method has been developed for the quantitative determination of linoleic acid in infant formulas by gas chromatography (GC). A known amount of triheptadecanoin was spiked into the sample. Total lipid was extracted from the product by an ethyl ether-petroleum ether-ethanol system in a Mojonnier flask. The sample was saponified by methanolic KOH after the solvents were evaporated. Methyl esters of the fatty acids were prepared by boron trifluoride (BF3) in methanol and analyzed by gas chromatography. A glass column packed with 10% SP-2340 (75% cyanopropyl silicone) was used to separate and identify the methyl linoleate and the methyl heptadecanoate. The quantity of methyl linoleate was calculated by comparing the integrated peak areas of these 2 fatty acid methyl esters. This method was satisfactory for both milk protein-based and soy protein-based matrixes. The results obtained by this method are comparable to those obtained by the AOAC spectrophotometric method 28.082-28.085.     

加工温度及存放时间对富共轭亚油酸牛乳脂脂肪酸的影响

随着富共轭亚油酸(CLA)原料乳生产技术的日趋成熟,为研究CLA牛乳加工温度及其贮藏期内CLA含量变化对CLA牛乳终端产品的影响,对不同处理温度及存放时间的牛乳进行脂肪酸分析,试验结果表明,不同温度处理对牛乳中c9t11CLA影响差异不显著(p>0.05);75℃和135℃处理后的不同存放期内乳中c9t11CLA变化差异也不显著(p>0.05);但在120℃处理后的保存期内,c9t11CLA含量有升高趋势(p=0.045)。试验未发现一定加工温度及保存时间引起富CLA牛乳中c9t11CLA含量大幅度降低现象,因此,富CLA牛乳适合终端产品开发。     

Determination of conjugated linoleic acid (CLA) concentrations in milk chocolate

The fatty acids from a series of milk-chocolate-based confectionery samples were analyzed as methyl esters by GC to determine the presence and amount of conjugated linoleic acid (CLA). A single peak corresponding to the 9-cis,11-trans isomer and ranging from less than 0.1% to nearly 0.2% of the total fatty acids, corresponding to up to 0.3 mg per g of chocolate, was observed. One of the chocolate extracts and a milk extract were subjected to silver ion HPLC and GC-MS in order to confirm the identity of the major isomer and tentatively identity minor isomers.     

Influence of feeding soybean oil on conjugated linoleic acid content in beef

Forty-eight steers were used to study the influence of feeding soybean oil (SO) on the conjugated linoleic acid (CLA) content of beef. Steers were fed either a control diet containing 954 g/kg of dry matter (DM) corn-based concentrate (CTL) or a control diet supplemented with SO at 20 (SO2) or 40 g/kg (SO4) of diet DM for 105 days. Adipose tissue samples were collected from the M. longissimus dorsi (LD) and from the M. semitendinosus (ST) on days 0 and 63 of the experiment. Adipose and muscle tissue samples were collected from the LD and ST immediately after slaughter. Feeding 40 g/kg of DM as SO increased the proportions of trans-C(18:1) in beef lipid as compared to CTL and SO2 treatments. The C(18:2) cis-9, trans-11 isomer of CLA as a proportion of total fat was not different in adipose and muscle across treatments. Supplementing SO increased C(18:2) trans-10, cis-12 CLA in adipose tissue of the LD. Supplementing high-grain finishing diets with SO is not an effective strategy to enhance the C(18:2) cis-9, trans-11 isomer of CLA in beef.     

Hydroxycinnamic acids and ferulic acid dehydrodimers in barley and processed barley

Hydroxycinnamic acid content and ferulic acid dehydrodimer content were determined in 11 barley varieties after alkaline hydrolysis. Ferulic acid (FA) was the most abundant hydroxycinnamate with concentrations ranging from 359 to 624 microg/g dry weight. p-Coumaric acid (PCA) levels ranged from 79 to 260 microg/g dry weight, and caffeic acid was present at concentrations of <19 microg/g dry weight. Among the ferulic acid dehydrodimers that were identified, 8-O-4'-diFA was the most abundant (73-118 microg/g dry weight), followed by 5,5'-diFA (26-47 microg/g dry weight), the 8,5'-diFA benzofuran form (22-45 microg/g dry weight), and the 8,5'-diFA open form (10-23 microg/g dry weight). Significant variations (p < 0.05) among the different barley varieties were observed for all the compounds that were quantified. Barley grains were mechanically fractionated into three fractions: F1, fraction consisting mainly of the husk and outer layers; F2, intermediate fraction; and F3, fraction consisting mainly of the endosperm. Fraction F1 contained the highest concentration for ferulic acid (from 77.7 to 82.3% of the total amount in barley grain), p-coumaric acid (from 78.0 to 86.3%), and ferulic acid dehydrodimers (from 79.2 to 86.8%). Lower contents were found in fraction F2, whereas fraction F3 exhibited the lowest percentages (from 1.2 to 1.9% for ferulic acid, from 0.9 to 1.7% for p-coumaric acid, and <0.02% for ferulic acid dehydrodimers). The solid barley residue from the brewing process (brewer's spent grain) was approximately 5-fold richer in ferulic acid, p-coumaric acid, and ferulic acid dehydrodimers than barley grains.     

Effect of the degree of processing on soy oil conjugated linoleic acid yields

Photoirradiation processing can be used to rapidly synthesize conjugated linoleic acid (CLA) in large quantities in soy oil. The objective of this study was to evaluate the effect of the level of refining of soy oil on CLA yields and oxidative properties after photoirradiation. Crude, alkali-refined, alkali-refined bleached, and alkali-refined bleached and deodorized (RBD) soy oils were photoirradiated in a pilot-plant processing system for 12 h with 0.35% iodine catalyst at 47 degrees C. RBD soy oil gave the highest total CLA yield of 16.3% of total oil with 4.3% cis, trans- and trans, cis-CLA isomers. Oxidative stability as measured by weight gain during incubation at 64 degrees C showed that iodine decreased the induction time of soy oil samples by 2-4 days. Photoirradiation processing further decreased the induction time by 2 days as a result of loss of total tocopherols. Iodine addition increased the titratable acidity in all the samples of soy oil. However, the level of refining affects this increase of titratable acidity, and RBD soy oil was found to be the most stable. The study indicates that RBD soy oil was the most suitable candidate for photoirradiation processing. Thus, soy oil should be alkali-refined, bleached, deodorized, and then photoprocessed followed by a secondary adsorption step to remove the iodine catalyst to obtain a RBD CLA-rich soy oil.     

Biochemical and microbial changes during the storage of minimally processed cantaloupe

The effect of storage time on pH, titratable acidity, degrees Brix, organic acids, sugars, amino acids, and color of minimally processed cantaloupe melon (Cucumis melo L. var. reticulatus Naud. cv. Mission) was determined at 4 degrees C and 20 degrees C. Changes in most of the biochemical parameters with storage time were relatively slow at the lower temperature. At 20 degrees C, a 17% loss in soluble solids and a 2-fold increase in acidity occurred after 2 days. Organic acid content also increased considerably with time at this temperature as a result of the production of lactic acid. Oxalic, citric, malic, and succinic acids were the organic acids, and glucose, fructose, and sucrose were the sugars present in the freshly cut cantaloupe. Malic acid concentration decreased concurrently with lactic acid production indicating the possible involvement of anaerobic malo-lactic fermentation along with sugar utilization by lactic acid bacteria. The effect of storage on microbial growth was determined at 4, 10, and 20 degrees C. Gram-negative stained rods grew at a slower rate at 4 degrees C and 10 degrees C than the Gram-positive mesophilic bacteria that dominated microorganism growth at 20 degrees C. Eighteen amino acids were identified in fresh cantaloupe: aspartic acid, glutamic acid, asparagine, serine, glutamine, glycine, histidine, arginine, threonine, alanine, proline, tyrosine, valine, methionine, isoleucine, leucine, phenyl alanine, and lysine. The dominant amino acids were aspartic acid, glutamic acid, arginine, and alanine. Total amino acid content decreased rapidly at 20 degrees C, but only a slight decrease occurred at 4 degrees C after prolonged storage. Changes in lightness (L), chroma, and hue at both temperatures indicate the absence of browning reactions. The results indicate the potential use of lactic acid and lactic acid bacteria as quality control markers in minimally processed fruits.     

Effects of high hydrostatic pressure treatments on biogenic amine contents in goat cheeses during ripening

The application of high-pressure treatment to accelerate cheese ripening may influence the occurrence and profile of biogenic amines. In some cases, high-pressure treatment could yield high amine content, whereas in others the amine concentrations were comparable with those in nontreated ones. Tyramine was the most affected amine. However, the influence of high pressure depended on the treatment applied. The highest amine concentrations were observed when 50 MPa for 72 h was applied, and in which, the content of tyramine was almost three times higher than in the untreated samples. On the contrary, when 400 MPa for 5 min or 400 MPa for 5 min plus 50 MPa for 72 h were applied contents of this amine were similar or lower than those found in control cheeses showing similar degrees of proteolysis. The higher proteolysis, induced by the pressurization treatments, was not correlated with the higher amine production.