Volatile oxidation compounds in a conjugated linoleic acid-rich oil

In this study, volatile oxidation compounds formed in a commercial conjugated linoleic acid (CLA)-rich oil were quantified and results compared to those found in safflower oil (rich in linoleic acid, LA). Intact oil samples and pure triacylglycerols obtained following elimination of tocopherols and minor compounds were oxidised at 60 °C, and volatile oxidation compounds were analysed by solid phase microextraction-gas chromatography with flame ionisation detector and mass spectrometer. Results showed that while, as expected, hexanal was the major volatile oxidation compound found in oil and triacylglycerols rich in LA, both hexanal and heptanal equally were the most abundant compounds in oil and triacylglycerols rich in CLA. Besides, samples rich in CLA also showed significantly high quantities of trans-2-octenal and trans-2-nonenal and the latter, along with heptanal, were absent in samples rich in LA. Results for CLA samples were not easy to interpret since major volatiles found are not expected from theoretically stable hydroperoxides formed in CLA and could in part derive from dioxetanes coming from 1,2-cycloadditions of CLA with oxygen. Overall, results obtained support evidence that oxidation mechanisms of CLA may differ than those of LA. Also, it was concluded that heptanal determination could serve as a useful marker of oxidation progress in CLA-rich oils.     

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.     

共轭亚油酸的合成

共轭亚油酸(CLA)是亚油酸(LA)的同分异构体,是一种非常重要的功能性油脂,在医药保健、食品工业、饲料等方面的应用有着广阔的应用前景.从CLA的生产方法着手,重点描述了传统CLA的制备方法-化学异构化法、羟基脂肪酸脱水法,生物合成法和光异构化法.并对这些方法的研究手段、国内外研究水平、存在的问题、解决措施、优缺点和应用前景进行了介绍.尤其是生物合成法,由于其产物选择性高、异构体种类少、培养易于控制等,具有很好的商业应用前景.     

Influence of sodium glycocholate on production of conjugated linoleic acid by cells of Lactobacillus reuteri ATCC 55739

ABSTRACT:  The possible influence of a bile salt on production of conjugated linoleic acid (CLA) by Lactobacillus reuteri ATCC 55739 was evaluated. Cells of the lactobacilli grown in MRS broth with and without linoleic acid (LA, 0.2%) were harvested and washed. The washed cells were added to buffer containing 0.2% LA and incubated 18 h at 37 °C. The cells, which had been grown without LA, transformed LA into CLA (mainly c9t11-C18:2) better than did those cells grown with it. When sodium glycocholate (0.3%) was added to the washed cell suspensions, about the same level of CLA was formed as in its absence regardless of whether or not the cells had been grown in broth supplemented with free LA. Thus, glycocholate that occurs in humans did not influence production of CLA by resting cells of the lactobacilli.     

保加利亚乳杆菌诱导产亚油酸异构酶条件研究

亚油酸异构酶可由保加利亚乳杆菌经诱导产生,可以将亚油酸(LA)转化为共轭亚油酸(CLA)。本实验对诱导保加利亚乳杆菌产亚油酸异构酶的条件进行研究,利用紫外和气质联用仪(GC-MS)检测所生成的CLA。结果表明：在培养基中添加1.5‰(V/V) LA 时所产酶的共轭亚油酸转化率最高;温度为36℃,培养36h 为较适的培养条件;单独添加0.1%(m/V)的乳糖或0.1%(m/V)的氯化钠有利于诱导产酶;在培养基中直接添加LA 的效果优于培养3至12h 后再进行添加。诱导所产酶可将LA 转化为CLA,且含有9c,11t-CLA 异构体。     

共轭亚油酸生理功能及其合成方法

共轭亚油酸（CLA）为亚油酸（LA）的异构体,具有抗癌、降脂、调节免疫、抗粥样硬化等重要的生理功能,目前共轭亚油酸（CLA）的生产大都是利用碱催化亚油酸异构而成,但其异构体繁多。利用微生物转化生产的共轭亚油酸（CLA）,异构体较少,与天然食品中的CLA异构体组成相似,具有很好的商业前景。     

共轭亚油酸生物合成及其对肠道菌群影响的研究进展

共轭亚油酸(CLA)是一种人和动物自身无法合成但又不可缺少的脂肪酸,它具有抗癌、抗肥胖、抗动脉粥样硬化、抗糖尿病等潜在生理功能,被广泛用作食品营养补充剂。由于天然CLA来源较少、化学合成副产物较多,而利用乳酸菌生物合成的CLA结构单一且转化效率高,是一种有前景的合成方法。目前微生物将亚油酸(LA)转化为CLA的机制主要有2种,即以瘤胃微生物为主的生物氢化合成和乳酸菌为代表的多酶系合成。现有研究表明,CLA具有调节肠道菌群的作用,并指出其潜在生理功能可能与其对肠道微生态的影响密切相关。文章总结了CLA生物合成和影响因素,分析了CLA的生物合成机制以及其对肠道菌群的调节作用,为进一步筛选出高产CLA菌株和CLA的产业化应用提供理论依据。     

Role of the conjugated linoleic acid in the prevention of cancer

There are multiple lines of evidence that a variety of natural fatty acids are effective in health promotion. Among these fatty acids, conjugated linoleic acid (CLA)--a collective term referring to a mixture of positional and geometric isomers of linoleic acid (LA, cis-9, cis-12-octadecadienoic acid)--is currently under intensive investigation due to its health-promotion potential. The antitumor activity of CLA is of special interest, since it shows inhibitory effects against multistage carcinogenesis at relatively low dietary levels. Many studies using in vivo and in vitro models have shown that CLA suppresses the development of multistage carcinogenesis at different sites. The research to date on CLA has provided a vast amount of information about the mechanism on how CLA functions in the prevention of cancer. This article discusses characteristics of CLA in the prevention of cancer in both in vivo and in vitro studies and the possible underlying chemoprevention mechanisms.     

Production of conjugated linoleic acid-rich potato chips

ABSTRACT:  Conjugated linoleic acid (CLA) is found primarily in diary and beef products, but the health benefits of CLA can only be realized if they are consumed at much greater levels than a normal healthy dietary intake. We have recently shown that a CLA-rich soy oil can be produced by simple isomerization of linoleic acid in soy oil by photoirradiation. This oil may allow greatly increased dietary CLA without significantly elevating fat intake. The objective of this study was to prepare CLA-rich potato chips by frying in CLA-rich soy oil. Soy oil was photoisomerized in the presence of iodine catalyst with UV/visible light. The irradiated oil was clay processed to remove the residual iodine and this oil was then used to fry potato chips. Oil was extracted from fried chips and analyzed for its CLA content with gas chromatography. A 1-oz serving of CLA-rich potato chips contained approximately 2.4 g CLA as compared to 0.1 g CLA in 3-oz serving of steak fillet and 0.06 g CLA in 8-oz serving of whole milk. The peroxide value of the oil extracted from potato chips was found to be 1 meq/1000 g sample, which was within the acceptable commercial standards. This study may lead to the commercialization of CLA-rich food products.     

Bacterial Production of Conjugated Linoleic and Linolenic Acid in Foods: A Technological Challenge

Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers are present in foods derived from ruminants as a result of the respective linoleic acid (LA) and α-linolenic acid (LNA) metabolism by ruminal microorganisms and in animals’ tissues. CLA and CLNA have isomer-specific, health-promoting properties, including anticarcinogenic, antiatherogenic, anti-inflammatory, and antidiabetic activity, as well as the ability to reduce body fat. Besides ruminal microorganisms, such as Butyrivibrio fibrisolvens, many food-grade bacteria, such as bifidobacteria, lactic acid bacteria (LAB), and propionibacteria, are able to convert LA and LNA to CLA and CLNA, respectively. Linoleate isomerase activity, responsible for this conversion, is strain-dependent and probably related to the ability of the producer strain to tolerate the toxic effects of LA and LNA. Since natural concentrations of CLA and CLNA in ruminal food products are relatively low to exert their health benefits, food-grade bacteria with linoleate isomerase activity could be used as starter or adjunct cultures to develop functional fermented dairy and meat products with increased levels of CLA and CLNA or included in fermented products as probiotic cultures. However, results obtained so far are below expectations due to technological bottlenecks. More research is needed to assess if bacterial production kinetics can be increased and can match food processing requirements.     

Effects of substrate, passage rate, and pH in continuous culture on flows of conjugated linoleic acid and trans C18:1

A dual-flow continuous culture system consisting of 4 fermenters was used in a 4 x4 Latin square design. The objective of the research was to evaluate the effects of solid dilution rate (SDR), pH, and concentration of linoleic acid (LA) in the feed mixture on the production of conjugated linoleic acid (CLA) and trans-C18:1. The 4 treatments were 1) control = pH 6.5, 1% LA, 4%/h SDR; 2) high solid dilution rate (HSDR) = pH 6.5, 1% LA, 8%/h SDR; 3) high linoleic acid (HLA) = pH 6.5, 3% LA, 4%/h SDR; and 4) low pH (LPH) = pH 5.8, 1% LA, 4%/h SDR. Inoculum was collected 6 h after feeding from a cow fed 40% alfalfa hay and 60% grain. Liquid dilution rate was held at 0.12/h. All treatments except HLA contained 2% tallow. The LA was dissolved in buffer and continuously infused into the fermenters. The CLA flows were 16.5, 20.4, 23.2, and 25.2 mg/d for control, HSDR, HLA, and LPH, respectively. Compared with control, LPH increased flows of CLA, cis-C18:1, and C18:2, and decreased flow of C18:0. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibilities were not affected by pH. The HSDR tended to increase CLA flow compared to control, possibly because a shorter solid retention time led to incomplete biohydrogenation (BH). The NDF and ADF digestibilities and bacterial numbers were reduced by HSDR. With more LA available as a substrate for CLA, HLA resulted in a higher flow of CLA than control. The HLA resulted in the highest acid detergent fiber and fatty acid digestibilities, bacterial numbers, and BH. Increasing solids passage rate, reducing pH, and increasing dietary LA appears to increase in vitro CLA production.     

Production of conjugated linoleic acid by food‐grade bacteria: A review

Conjugated linoleic acid (CLA) is a group of isomers of linoleic acid (LA) with several potential health benefits which justifies the efforts to obtain foods with enhanced CLA contents. A possible way to obtain CLA‐enriched products is via fermentation as several micro‐organisms, many of which are employed in the manufacture of foods, are known to convert free LA into CLA. However, due to several constraints, the use of CLA‐producing bacteria still remains challenging and continuous efforts are required. This review summarises the current knowledge on microbial CLA production by food‐grade micro‐organisms, its technical issues and limitations, potential applications and bioactivities.     

产共轭亚油酸鼠李糖乳杆菌的筛选与鉴定

从东北传统酸菜汁中筛选出具有产共轭亚油酸(CLA)能力的乳酸菌菌株15株,采用紫外分光度计法测定发酵液中共轭亚油酸产量,其中菌株A53.2的产量最高,在MRS培养基中添加0.4mg/mL亚油酸(LA),37℃发酵24h,CLA产量达14.91μg/mL。通过对菌体的形态特征和生化特性分析,并结合16SrDNA分子生物学以及系统发育分析鉴定菌株A53.2为鼠李糖乳杆菌。     

共轭亚油酸的生理功效及其在乳品中的强化途径

综述了共轭亚油酸(CLA)在抗癌、降低血清胆固醇、强化免疫、促生长、抑制脂肪沉积等的方面的生理作用；阐述了乳及其制品中共轭亚油酸产生的特点；讨论了发酵乳制品中影响共轭亚油酸产生的各种因素以及菌株产生亚油酸异构酶的条件，比较了不同来源的乳酸菌产共轭亚油酸的能力和在乳中的强化模式；最后比较了常用的共轭亚油酸检测分析方法及其效果。     

Occurrence of conjugated linoleic acid in longissimus dorsi muscle of water buffalo (Bubalus bubalis) and zebu-type cattle raised under savannah conditions

Lipid extracts from longissimus dorsi muscles of 64 water buffaloes and 68 zebu-type cattle were used to quantify the amount (mg/g of lipids) of total conjugated linoleic acid (CLA), CLA isomers c9, t11 and t10, c12 and linoleic acid (LA), according to species (buffaloes and cattle), age (slaughter groups at 7, 17, 19 or 24 months of age) and gender (bulls and steers). The effects of gender and age were significant (P<0.05) but marginal. Comparisons of lipid extracts from buffaloes vs. cattle showed that total CLA (1.83 vs. 1.47 mg/g), CLA c9, t11 (1.27 vs. 1.01 mg/g) and CLA t10, c12 (0.56 vs. 0.47 mg/g) isomers as well as the CLA/LA ratio (0.10 vs. 0.07) were higher (P<0.05) in buffalo lipids. Considering the sparingly low lipid concentrations (<2 g/100 g of fresh muscle) none of the meat species should be considered a significant source of CLA.     

产共轭亚油酸丙酸菌的筛选及转化条件初探

通过富集培养、梯度密度稀释和液体培养发酵,采用紫外分光光度法测定共轭亚油酸(CLA),从市售奶酪中筛选获得1株转化生成CLA能力相对较高的菌株P9:考察了菌体接种量、亚油酸(LA)的添加量、反应温度、反应体系pH值以及乳化剂种类等因素对菌株P9 CLA生成量的影响.通过对菌株P9的菌落和形态特征、产丙酸特性及生理生化特性分析,初步鉴定该菌株为费氏丙酸杆菌(Propionibacterium frudenreichii).研究结果显示,菌株P9在菌体接种量10%(v/v),LA添加量0.75mg/mL,pH值为6.8,反应温度30℃,Tween-80作为乳化剂的条件下,CLA生成量为63.371μg/mL,亚油酸转化率为8.45%,表现出较好的产共轭亚油酸能力.     

Production of free conjugated linoleic acid by Lactobacillus acidophilus and Lactobacillus casei of human intestinal origin

A gas chromatographic procedure was used for analysis of conjugated linoleic acid (CLA) isomers cis-9, trans-11-octadecadienoic; trans-10, cis-12 octadecadienoic; and trans-9, trans-11-octadecadienoic (c9t11, t10c12, t9t11) produced by lactobacilli. Four different cultures, two strains each of Lactobacillus acidophilus and Lactobacillus casei were tested for their ability to produce CLA from free linoleic acid in MRS broth supplemented with linoleic acid. Different concentrations of linoleic acid (0, 0.05, 0.1, 0.2 and 0.5 mg/ml) were added to MRS broth, inoculated with the lactobacilli, and incubated at 37 degrees C. Viable counts and amounts of individual isomers of CLA (c9t11, t10c12, t9t11) were measured at 0, 24, 48, and 72 h. All the cultures were able to produce free CLA in media supplemented with linoleic acid. Maximum production of CLA (80.14 to 131.63 microg/ml) was observed at 24 h of incubation in broth containing 0.02% of free linoleic acid. No significant (P > 0.05) increases in total CLA levels were observed after 24 h of incubation. The ability of the cultures to produce CLA in skim milk supplemented with 0.02% free linoleic acid also was studied. In this medium, the total amounts of free CLA after 24 h of incubation ranged from 54.31 to 116.53 microg/ml. The use of lactic acid bacteria able to form free CLA in cultured dairy products may have potential health or nutritional benefits. Free CLA in the products likely would be more readily available for absorption from the digestive tract than if it were incorporated into the cells of the starter culture.     

Additive anti-inflammation by a combination of conjugated linoleic acid and α-lipoic acid through molecular interaction between both compounds

Food Science and Biotechnology - Alpha lipoic acid (LA) and conjugated linoleic acid (CLA) have been well-documented on a variety of functional effects in health foods. The main purpose of this...     

高纯度共轭亚油酸的制备

以红花籽油为原料,比较了2种高纯度共轭亚油酸(CLA)的制备方法:(1)碱法异构化-尿素包合、(2)皂化-尿素包合-碱法异构化。针对每种方法确定了尿素包合和碱法异构化的最佳工艺条件,并对所得的CLA异构体组成进行了分析。研究表明:按照方法(2)先获得高纯度亚油酸(LA),再对其碱法异构化制备CLA可以得到纯度更高的产品。该方法在最佳反应条件下,制备得到的CLA的纯度为97.22%,收率为32.08%,其中c9t11-CLA含量为45.14%,t10c12-CLA含量为49.12%。     

Effectiveness of oils rich in linoleic and linolenic acids to enhance conjugated linoleic acid in milk from dairy cows

Forty Holstein dairy cows were used to determine the effectiveness of linoleic or linolenic-rich oils to enhance C_18:2cis-9, trans-11 conjugated linoleic acid (CLA) and C_18:1trans-11 (vaccenic acid; VA) in milk. The experimental design was a complete randomized design for 9 wk with measurements made during the last 6 wk. Cows were fed a basal diet containing 59% forage (control) or a basal diet supplemented with either 4% soybean oil (SO), 4% flaxseed oil (FO), or 2% soybean oil plus 2% flaxseed oil (SFO) on a dry matter basis. Total fatty acids in the diet were 3.27, 7.47, 7.61, and 7.50 g/100 g in control, SO, FO, and SFO diets, respectively. Feed intake, energy-corrected milk (ECM) yield, and ECM produced/kg of feed intake were similar among treatments. The proportions of VA were increased by 318, 105, and 206% in milk fat from cows in the SO, FO, and SFO groups compared with cows in the control group. Similar increases in C_18:2cis-9, trans-11 CLA were 273, 150, and 183% in SO, FO, and SFO treatments, respectively. Under similar feeding conditions, oils rich in linoleic acid (soybean oil) were more effective in enhancing VA and C_18:2cis-9, trans-11 CLA in milk fat than oils containing linolenic acid (flaxseed oil) in dairy cows fed high-forage diets (59% forage). The effects of mixing linoleic and linolenic acids (50:50) on enhancing VA and C_18:2cis-9, trans-11 CLA were additive, but not greater than when fed separately. Increasing the proportion of healthy fatty acids (VA and CLA) by feeding soybean or flaxseed oil would result in milk with higher nutritive and therapeutic value.