Conjugated Linoleic Acid Fatty Acids Research Articles

Impact of hedonic evaluation on consumers' preferences for beef attributes including its enrichment with n-3 and CLA fatty acids

The impact of hedonic evaluation on consumers' preferences for beef attributes was evaluated (origin, animal diet, fat content, color, price) including its enrichment with omega-3 (n-3) and conjugated linoleic acid (CLA) fatty acids. One group of consumers (n=325) received information about n-3 and CLA, while the other group (n=322) received no information. Consumers conducted a Discrete Choice Experiment (DCE), using the recently developed Generalized Multinomial Logit model; followed by a blind hedonic evaluation of beef samples, which were identified after tasting, and finally repeated the DCE. Results showed that hedonic evaluation had a significant impact on consumers' preferences, which were similar after tasting for all consumers, with less emphasis on the fat content, color, and origin attributes and greater emphasis on animal diet. Preference for n-3 enriched beef increased, while preference for CLA enriched beef was still not significant after tasting. The information provided had a significant effect on consumers' beef preferences, but no significant impact on beef liking scores.

Fatty acid composition of young Holstein bulls fed whole linseed and rumen-protected conjugated linoleic acid enriched diets

Forty-eight young Holstein bulls were used to evaluate the effect of whole linseed and conjugated linoleic acid (CLA) supplementation on beef fatty acid profile in intramuscular and subcutaneous fat. Animals were fed one of four isoenergetic and isoproteic diets: control (0% linseed, 0% CLA), linseed (10% linseed, 0% CLA), CLA (0% linseed, 2% CLA), and linseed plus CLA (10% linseed, 2% CLA). The fatty acid profile had similar trends in intramuscular and subcutaneous fat when diets were enriched with linseed and/or CLA, increasing the level of CLAc9,t11 and α-linolenic acid (ALA), and decreasing the n-6/n-3 fatty acid ratio. Supplementation with linseed improved the fatty acid profile by increasing the proportions of n-3 and CLA fatty acids and decreasing the n-6/n-3 ratio compared with the control. CLA addition achieved similar CLA tissue levels to linseed supplementation, but similar n-3 proportions to the control. Linseed plus CLA supplementation was more effective in increasing total polyunsaturated fatty acids and CLA compared with their individual addition. It is concluded that supplementation of whole linseed and/or CLA in bulls resulted in an increase in beef fat of some fatty acids considered to be of potential benefit to human health.

Contenido de ácido linoleico conjugado (CLA) en leche de ganado lechero Holstein estabulado en el noroeste de México

Experimental animal studies suggest that conjugated linoleic acid (CLA) has beneficial health properties. Ruminant-derived products such as meat and milk are the principal natural sources of CLA. Milk CLA content is influenced by several factors, including diet and production system. An evaluation was done of CLA content in milk from confined Holstein cows at a farm in Hermosillo municipality, Sonora State, Mexico, during the summer months, when daytime temperatures surpass 40 °C. Milk samples were collected from 120 cows. Quality parameters such as fat, lactose, protein and total solids percentages were measured using AOAC methods. The fatty acid and CLA profile was generated by gas chromatography. Average milk production was 15.8 ± 0.5 kg/day, fat content was 1.91 ± 0.06 %, lactose content was 4.30 ± 0.2 %, protein content was 3.34 ± 0.03 and total solids content was 10.4 ± 0.09 %. Unsaturated fatty acids content was higher (P<0.05) in August than during June and July. Average cis-9, trans-11 CLA concentration was 9.36 mg/g fat (10.78 ± 0.41 in June, 8.50 ± 0.37 in July, and 10.16 ± 0.39 in August), which is high compared to concentrations reported in countries with a temperate climate. The relatively high CLA content observed in the present study was probably caused by the 58.8 % alfalfa content in the summer diet, since this legume is rich in CLA fatty acids precursors (linoleic and linolenic acid).

ENZYMATIC PRODUCTION OF CONJUGATED LINOLEIC ACID MONOACYLGLYCEROLS FROM DEHYDRATED ISOMERIZED CASTOR BEAN OIL

ABSTRACT The goal of this study was to produce conjugated linoleic acid (CLA) monoacylglycerols (MAGs). A chemicoenzymatic process was employed starting from castor bean oil, which was chemically dehydrated and isomerized to obtain new modified triacylglycerols (TAGs) with a very high proportion of CLA fatty acids (&gt;95%). Such TAGs were then used in enzymatic glycerolysis reaction using Candida antarctica B lipase at 55C in tert‐butyl alcohol as a solvent. The effect of enzyme load and substrate molar ratio on the production yield of MAGs was evaluated and optimized using response surface methodology with a two‐factor and three‐level factorial design. A satisfactory linear correlation existed between experimental results and predicted values (R2 = 0.97 and R2adj. = 0.94). Using the contour plot generated from the model for MAG production yield, optimum parameters could be obtained corresponding to an 11/1 glycerol/TAG molar ratio and an enzyme load of 2% (% w/w of both substrates).PRACTICAL APPLICATIONSThis research work proposes a new route for the synthesis of functional monoacylglycerols combining the emulsifying effect of partial acylglycerols with the nutritional benefits of conjugated linoleic acids, which have been shown to exhibit promising biological properties. The compounds so produced may have potential applications in the food industry.

The Effect of Solids Dilution Rate and Oil Source on Trans C18:1 and Conjugated Linoleic Acid Production by Ruminal Microbes in Continuous Culture

The objective of this study was to evaluate the effect of solids dilution rate (SDR) and oil source [soybean oil (SBO) or linseed oil (LSO)] on the ruminal production of trans C18:1 and conjugated linoleic acid (CLA). A dual-flow continuous culture system consisting of 4 fermenters was used in a 4×4 Latin square design with a factorial arrangement of treatments over 4 consecutive periods of 10 d each. Treatment diets (50:50 forage to concentrate) were fed at 120 g/d of dry matter (DM) in 3 equal portions. The concentrate mix contained 1% fish oil and either 2% SBO or 2% LSO on a DM basis. Treatments were as follows: 1) SBO at 6%/h SDR, 2) SBO at 3%/h SDR, 3) LSO at 6%/h SDR, and 4) LSO at 3%/h SDR. The oil source by SDR interaction was not significant for trans C18:1 and CLA fatty acids. The concentrations of trans C18:1 and vaccenic acid were greater in effluents when diets were supplemented with SBO vs. LSO (37.11 vs. 34.09 and 32.71 vs. 29.70 mg/g of DM, respectively) and at high SDR than low SDR (37.60 vs. 33.61 and 32.72 vs. 29.61 mg/g of DM, respectively). The concentration of cis-9, trans-11 CLA in effluents was also greater with SBO than LSO (0.81 vs. 0.40 mg/g of DM) supplementation and at high SDR than low SDR (0.68 vs. 0.54 mg/g of DM). Biohydrogenation of linoleic acid and linolenic acid increased at higher SDR within each oil treatment. Based on these results, SBO supplementation at high SDR enhances ruminal production of vaccenic acid, and therefore could potentially enhance cis-9, trans-11 CLA in milk fat through synthesis by Δ9-desaturase.

Improved Identification of Conjugated Linoleic Acid Isomers Using Silver-Ion HPLC Separations

Silver-ion high-performance liquid chromatography (Ag+-HPLC) has been shown to be effective in the resolution of most of the isomers of conjugated octadecadienoic acids (18:2), also known as conjugated linoleic acid (CLA). The CLA isomers identified in natural fats from ruminants are a mixture of numerous positional and geometric isomers from 7,9- to 12,14-18:2. Ag+-HPLC separates both geometric (trans,trans < cis/trans < cis,cis) and positional CLA isomers using the mobile phase hexane/acetonitrile (99.9:0.1). The elution volumes for the CLA isomers were not only affected by the concentration of acetonitrile (in the prepared mobile phase) but also with successive runs during the day using a prepared mobile phase batch, due to the partial solubility of acetonitrile in hexane. However, this drift does not affect the relative resolution of the CLA isomers. The addition of diethyl ether to the mobile phase partly stabilizes the solvent mixture. In order to facilitate the interpretation of Ag-+HPLC chromatograms, the relative retention volumes (RRV) were calculated for each CLA isomer. Toluene was added to all the test portions and served as an estimator of dead volume, whereas the elution of the ubiquitous 9c,11t-CLA isomer was chosen as unity (1.00). Expressing the elution of all the CLA isomers as their RRV greatly helped to standardize each CLA isomer, resulting in relatively small coefficients of variation (% CV) for the trans,trans (<1.5%) and cis/trans (<0.5%) CLA isomers. The identification of the CLA isomers was further facilitated by synthesis of authentic CLA isomers. All the geometric CLA fatty acid methyl esters (FAME) from positions 6,8- to 13,15-CLA were commercially available or synthesized by a combination of partial hydrazine reduction of known polyunsaturated fatty acids followed by alkali isomerization, isolation of products, and further iodine-catalyzed geometric isomerization. Based on expressing the elution volume as RRV and the availability of the synthetic CLA isomers, a unique reversal of the elution order of the c/t CLA isomers was found. It is also proposed that the retention times of CLA isomers by gas chromatography (GC) should be expressed as their relative retention times (RRT) relative to methyl gamma-linoleneate. The availability of CLA reference materials and the application of RRV and RRT to Ag+-HPLC and GC separations, respectively, will greatly improve in the identifications of CLA isomers.

Simultaneous quantitative determination of isolated trans fatty acids and conjugated linoleic acids in oils and fats by chemometric analysis of the infrared profiles

Trans fatty acids and conjugated linoleic acids (CLA) in edible oils and fats have been for the first time quantitatively determined simultaneously using infrared spectroscopy and chemometrics. The task has been achieved by establishing calibration models using the infrared spectral profiles of the mixtures of trans and CLA fatty acids in virgin olive oil which is free of trans and CLA. The infrared profiles were scanned in the region 1000–850 cm −1 where the CH bending vibrations of the trans fatty acids and CH deformation vibrations of the CLA fall. Two calibration models, one for trans and/or CLA in the range 1–2.5% in olive oil and a second for trans and/or CLA in the range 0–30% in olive oil were established. The partial-least-squares (PLA) technique was used in establishing calibration models. Cross validation procedure was used in validating the calibration models. These models were then used to predict some laboratory-prepared samples and a natural sample (beef fat) for their trans and CLA contents. The model established for the lower concentration range predicts trans and CLA contents with an error limit of ±0.1% and at the same time the model established for high concentration range predicts trans and CLA contents with error limits of ±0.9 and ±0.5%, respectively. The predicted values in beef fat are in the range reported for this sample in the literature. These values were further confirmed by addition technique.