Selective Increase in Conjugated Linoleic Acid in Milk Fat by Crystallization

The objective of this work was to obtain concentrated natural conjugated linoleic acid (CLA) from milk fat by urea complexation. Milk fat was hydrolyzed to provide free fatty acids, followed by crystallization with different ratios of urea. The profiles of fatty acids achieved by urea complexation showed different fatty acid compositions. Long-chain unsaturated fatty acids, including CLA, were concentrated after crystallization. The highest amount of CLA was achieved by the first crystallization with a 2:1 urea/fatty acid ratio. CLA was elevated 2.5-fold. The C18:1/C18:0 fatty acid ratio was increased from 2 to 51, and stearic acid (C18:0) was decreased 17-fold.     

Effects of Linoleic Acid on Conjugated Linoleic Acid Production by Planktonic Rumen Bacteria from Grain-fed Cows

Ruminal conjugated linoleic acid (CLA) production from linoleic acid (LA) was characterized in vitro. Rumen bacteria from grain‐fed cows were more active in BH than those from hay‐fed cows. Particleassociated bacteria produced more hydrogenated products leaving less CLA than the planktonic bacteria (P < 0.05). CLA production by planktonic bacteria did not always correlate to LA given; longer incubations generally decreased CLA concentration and increased c9, t11/t10, c12 ratio, especially at higher LA concentrations. The preincubated cells to LA produced more CLA than the unexposed ones and the increase was more evident with c9, t11 CLA (P < 0.05). This study provides insight into how cattle diet and LA feedings affect ruminal CLA production.     

Increase of Conjugated Linoleic Acid Content in Milk by Fermentation with Lactic Acid Bacteria

ABSTRACT: The objectives of this study were to identify the factors and procedures responsible for increasing the conjugated linoleic acid (CLA) content in fermented milk. Fourteen lactic acid bacteria were screened for CLA-producing ability using sunflower oil (containing 70% linoleic acid) as a substrate. Among the screened strains, Lactococcus lactis I-01 showed the highest CLA-producing ability. The optimal concentration of sunflower oil for CLA production was 0.1 g/L in whole milk, which accounted for 0.25% of total milk fat. Our results demonstrated that CLA formation in fermented milk could be affected by numerous factors such as bacterial strain, cell number, optimal substrate concentration, and the period of incubation at neutral pH.     

Effect of Inoculation Level of Lactobacillus rhamnosus and Yogurt Cultures on Conjugated Linoleic Acid Content and Quality Attributes of Fermented Milk Products

ABSTRACT:  The effect of inoculation concentration of Lactobacillus rhamnosus and yogurt cultures and storage time on conjugated linoleic acid (CLA) content and quality attributes of fermented milk products was determined. Yogurt culture ( Lactobacillus bulgaricus and Streptococcus thermophilus, 1:1 ratio, YC ) , L. rhamnosus (LB), and LB co-cultured with yogurt culture, were inoculated at 10⁶, 10⁷, 10⁸ CFU/mL into a milk with hydrolyzed soy oil as the lipid source. CLA content, microbial counts, acidity, texture, and volatile flavor profile of the fermented milk products were stable during storage at 4 °C for 14 d. Total CLA contents ranged from 0.51 to 1.00 mg CLA/g lipid following 14 d of storage. Inoculation level of L. rhamnosus and yogurt cultures had no significant effect on CLA content and texture, but affected acidity and the volatile flavor profile of the fermented milk products. The fermented milk products produced by L. rhamnosus co-cultured with yogurt culture with 10⁷ CFU/mL total inoculation level resulted in a high CLA content and desirable quality characteristics. This research demonstrated that the optimal inoculation concentration and the combination of L. rhamnosus and yogurt cultures were important factors to produce fermented milk products with CLA content and acceptable quality attributes.     

Dietary Influences on Bovine Milk cis-9,trans-11-Conjugated Linoleic Acid Content

The effects of grass dry matter (DM) allowance and dietary supplements of full fat rapeseeds on levels of cis-9,trans-11 octadecadienoic (CLA) acid in bovine milk were investigated. Grass allowance of 16 kg/(cow*day) resulted in reduced (p<0.05) milk fat CLA levels (3.91 mg CLA/g fat) compared to 20 kg/(cow*day) after 19 wk treatment. CLA levels increased in milk fat from cows on a high-rapeseed-supplemented diet (p<0.001) (1650 g/(cow*day) full fat rapeseed) compared to the control (pasture) and low rapeseed (p<0.01) (825 g/(cow*day) full fat rapeseed) supplemented diets. The variation in milk fat CLA levels among individual cows over both trials was 1.5–16 mg/g.     

海蓬子籽油亚油酸共轭化产物的抗肿瘤作用

目的:探讨海蓬子籽油亚油酸共轭化产物体外抗肿瘤活性。方法:以含有73.52%亚油酸的海蓬子籽油为原料,利用化学法转化制备共轭亚油酸(conjugated linoleic acid,CLA),采用国标法和小鼠急性毒性实验对共轭化油进行理化指标分析和急性毒性评价,MTT法检测共轭化油对人肿瘤细胞的生长抑制作用。结果:共轭化油中c9,t11-CLA和t10,c12-CLA含量为68.75%,理化指标符合相关产品要求。小鼠急性毒性LD50>20g/kg,属无毒级。共轭化油对食道癌EC109细胞和乳腺癌HTB-22细胞均有较强抑制作用,对宫颈癌HeLa细胞无抑制活性,对正常人胚肾细胞293T无毒性,对EC109细胞的IC50为111.9μg/mL。结论:利用海蓬子籽油转化的共轭亚油酸产物对人肿瘤细胞有较强的生长抑制作用,但其作用具有选择性。     

Conjugated Linoleic Acid Concentrations in Dairy Products as Affected by Processing and Storage

Total conjugated linoleic acid (CLA) concentrations increased 1.32 fold in salted and 1.27 in unsalted butter but did not alter the ratio of 9-cis 11-trans to total CLA. Nonfat yogurt showed an increase in CLA content with processing (5.25 mg total CLA/g fat) compared to unprocessed raw material (4.40 mg CLA/g fat). No changes in CLA content was observed in processed dairy products such as lowfat yogurt, regular yogurt, lowfat and regular ice cream, sour cream or cheeses such as Mozzarella, Gouda and Cheddar. Storage did not affect CLA concentration in any products suggesting that CLA is a stable component.     

豆酸凝乳的研制

研究了以大豆为主要原料,利用嗜热乳酸链球菌和保加利亚乳杆菌混合发酵,制得无豆腥味且具有豆腐味及乳酸发酵特殊香味的大豆凝乳。     

Fatty Acids Profiles of Fresh Milk,Yogurt and Concentrated Yogurt from Peranakan Etawah Goat Milk

The objective of the study was to characterize the fatty acids profiles of goat milk and its fermented products i.e. yogurt and concentrated yogurt. Fresh milk from Peranakan Etawah goats was collected directly from local goat farmers, and processed into stirred-type fresh yogurt. The yogurt was then further processed into concentrated yogurt using Berge method. A total of 26 fatty acids were detected in milk, yogurt and concentrated yogurt, comprised of both saturated and unsaturated fatty acids. The oleic acid, stearic acid and palmitic acid were the major fatty acids found in fresh milk, yogurt and concentrated yogurt. There were changes in the profiles of individual fatty acids during processing of fresh goat milk into yogurt and concentrated yogurt.     

超临界法制备玉米共轭亚油酸的工艺研究

以玉米胚芽油为原料,采用超临界法制备玉米共轭亚油酸(CLA)。通过正交试验方法确定最佳工艺条件为温度80℃、油:碱为1:0.5、时间4h、油:溶剂为1:2、压力15MPa,此时异构化效果理想,经气相色谱检测CLA转化率97.65%,产品中c9,t11-CLA与t10,c12-CLA含量分别为27.72%和30.88%。     

共轭亚油酸合成原料的研究进展

共轭亚油酸(Conjugated Linoleic Acid,CLA)具有抗肿瘤、减少脂肪蓄积、调节机体免疫力、抗动脉粥样硬化、调节血糖血压、预防骨质疏松等多种生理活性,已经被广泛应用于医药、食品、保健品、化妆品等领域。由于CLA天然来源较少,以亚油酸为底物人工合成制备CLA成为了人们获取CLA的主要途径。本文系统介绍了游离脂肪酸、烷烃酯、甘油酯等不同形式的亚油酸及来源广泛、价格低廉的天然油脂在CLA生产中的运用,并综述了食品发酵中CLA的合成,为优化CLA原料利用、经济高效地获取CLA提供了参考。     

提高水牛奶中共轭亚油酸含量的菌种筛选

在水牛奶中分别添加不同的菌种进行发酵,通过溶剂法提取发酵乳中的脂肪,采用BF3/甲醇对脂肪酸进行甲酯化,使用紫外分光光度法与气相色谱法相结合进行发酵乳中共轭亚油酸的含量测定。结果显示,经单一菌种发酵的水牛奶其共轭亚油酸(CLA)的含量均有一定的提高,其中德式乳杆菌保加利亚亚种的转换能力相对最高。     

Effect of Dietary Starch or Micro Algae Supplementation on Rumen Fermentation and Milk Fatty Acid Composition of Dairy Cows

Two experiments with rumen-fistulated dairy cows were conducted to evaluate the effects of feeding docosahexaenoic acid (DHA; C22:6 n-3)-enriched diets or diets provoking a decreased rumen pH on milk fatty acid composition. In the first experiment, dietary treatments were tested during 21-d experimental periods in a 4 × 4 Latin square design. Diets included a control diet, a starch-rich diet, a bicarbonate-buffered starch-rich diet, and a diet supplemented with DHA-enriched micro algae [Schizochytrium sp., 43.0 g/kg of dry matter intake (DMI)]. Algae were supplemented directly through the rumen fistula. The total mixed ration consisted of grass silage, corn silage, soybean meal, and a standard or glucogenic concentrate. The glucogenic and buffered glucogenic diet had no effect on rumen fermentation and milk fatty acid composition because, unexpectedly, no reduced rumen pH was detected. The algae diet had no effect on rumen pH but provoked decreased butyrate and increased isovalerate molar proportions in the rumen. In addition, algae supplementation affected rumen biohydrogenation of linoleic and linolenic acid as reflected in the modified milk fatty acid composition toward increased conjugated linoleic acid (CLA) cis-9 trans-11, CLA trans-9 cis-11, C18:1 trans-10, C18:1 trans-11, and C22:6 n-3 concentrations. Concomitantly, on average, a 45% decrease in DMI and milk yield was observed. Based on these drastic and impractical results, a second animal experiment was performed for 20 d in which 9.35 g/kg of total DMI of algae were incorporated in the concentrate and supplemented to 3 rumen-fistulated cows. Algae concentrate feeding increased rumen pH, which was associated with decreased rumen short-chain fatty acid concentrations. Moreover, a different shift in rumen short-chain fatty acid proportions was observed compared with the first experiment because molar proportions of butyrate, isobutyrate, and isovalerate increased, whereas acetate molar proportion decreased. The milk fatty acid profile changed as in experiment 1. However, the decrease in DMI and milk yield was less pronounced (on average 10%) at this algae supplementation level, whereas milk fat percentage decreased from 47.9 to 22.0 g/kg of milk after algae treatment. In conclusion, an algae supplementation level of about 10 g/kg of DMI proved effective to reduce the milk fat content and to modify the milk fatty acid composition toward increased CLA cis-9 trans-11, C18:1 trans, and DHA concentrations.     

共轭亚油酸生理功能及其应用

共轭亚油酸(CLA)具有抗癌、抗动脉粥样硬化、改善脂肪代谢、骨组织代谢和减肥等多种生理活性,是一种具有保健功能脂肪酸。该文综述天然活性物质共轭亚油酸涵义界定、功能特性、CLA安全性与推荐摄入量及其在食品中应用前景。     

共轭亚油酸的结构与性质

该文系统地介绍和评述了共轭亚油酸结构和性质。共轭亚油酸与亚油酸不仅在空间结构上不同，而且在理化性质和生理功能等方面也具有显著区别。共轭亚油酸经肠粘膜吸收渗入到血脂、细胞膜及脂肪组织，或者经过代谢进一步合成一系列活性物质而发挥重要生理功能。     

一株嗜酸乳杆菌合成共轭亚油酸的条件优化

以嗜酸乳杆菌(Lactobacillus acidophilus)1.1854为出发菌株,经紫外诱变和诱导处理,获得1株共轭亚油酸(CLA)高产菌株,通过五因素二次正交旋转组合设计对该菌株合成共轭亚油酸的条件进行了优化。其优化条件为:培养温度37℃、pH值4.5～5.5、LA浓度0.1%、接种量5%～7%、培养时间24h,此时CLA产率达31.2%。     

米糠油提取物对共轭亚油酸的抗氧化作用研究

本文采用乙醇，异丙醇和乙酸乙酯为溶剂提取米糠油，得到富含天然抗氧化剂的米糠油提取物，其提取得率分别为26.8％，67．1％和82．8％。将提取物添加到共轭亚油酸中进行60℃氧化试验，结果农咧，虽然不同溶剂的提取物显示不同的抗氧化活性，但对于CLA的抗氧化效果均优于BHT，其中以异丙酣提取物的抗氧化效果最好，表明米糠油的异丙醇提取物可以作为CLA良好的天然抗氧化剂。     

共轭亚油酸同分异构体对肥胖Zucker大鼠的脂肪肝中的类二十烷酸的影响

目的:检测使用共轭亚油酸(CLA)同分异构体后,Zucker大鼠肝脏中多种类二十烷酸水平以及探测与这些种类二十烷酸合成有关的酶的蛋白表达。方法:17周的雄性Zucker大鼠被随机分为对照组[瘦鼠对照组(lean control),和胖鼠对照组(fa/fa control)n=7]和治疗组[随机抽取的肥胖鼠(fa/fa 9,11CLA、fa/fa 10,12CLA),n=7],分别接受无CLA的对照饮食和加入0.4%(w/w)CLA的治疗饮食。8周后用高效液相质谱仪(HPLC/MS/MS)检测多种类二十烷酸水平;使用免疫印迹法(Westernblotting)探测与这些种类二十烷酸合成有关的酶的蛋白表达。结果:与对照组比较,t10,c12 CLA升高了肝组织中的白三烯4(LTB4)的水平(P<0.01)。然而,免疫印迹实验(Western blotting)显示,t10,c12 CLA(P<0.005)和c9,t11CLA(P<0.005)都抑制环氧合酶(COX2)的表达。与胖鼠对照组比较,瘦鼠对照组有较高的羟二十碳四烯酸(HODE)水平。结论:t10,c12 CLA减少脂肪肝里的总脂肪量,而抑制了COX2的蛋白表达、升高LTB4水平,两者对肝组织的影响,有待于组织学研究证实。胖鼠对照组有较低的13-HODE和9-HODE水平,与脂肪肝的饱和脂肪酸代谢酶的活性降低,引起亚油酸(LA)降低有关,不能反映血循环中的氧化应激状态。