RESUMEN
This is the first time that fouling of cation-exchange membranes during cheddar cheese whey electroacidification with bipolar membranes is reported. A mineral fouling was observed only on the cationic membrane side in contact with the base. The deposit was identified as magnesium hydroxide and this fouling was more important on the cation-exchange membrane situated close to the cathode. Little deposit was formed after six electroacidification runs, but on long time, the buildup of fouling film would lead after many electroacidifications to an important decrease of the system efficiency. Since, fouling of permselective membranes represents one of the major issues in electrodialytic processes, this result will be the basis for the determination of cleaning conditions allowing the prevention of such a fouling.
Asunto(s)
Queso/análisis , Diálisis/métodos , Electroquímica , Tecnología de Alimentos , Intercambio Iónico , Membranas Artificiales , Microscopía Electrónica de Rastreo , Proteínas de la Leche/química , Proteína de Suero de LecheRESUMEN
Conjugated linolenic acids (CLnA) are octadecatrienoic fatty acid isomers with at least 2 conjugated double bonds. Various CLnA isomers occur naturally, and some isomers could be formed by ruminants from dietary alpha-linolenic acid. Ruminant biohydrogenation of polyunsaturated fatty acids gives rise to the formation of numerous metabolites having conjugated or nonconjugated structures. The objectives of this study were to identify and characterize CLnA isomers in milk fat and muscle lipid extracts from cattle fed a high-forage diet. The analysis of total fatty acid methyl esters revealed levels of total CLnA of 0.39% in a single milk lipid extract and 0.34% in a single muscle lipid extract. Fatty acid methyl esters were fractionated by argentation thin-layer chromatography. A fraction containing dienoic fatty acids as well as CLnA isomers was isolated and analyzed. The double bond positions of CLnA isomers (cis-9, trans-11, cis-15 and cis-9, trans-13, cis-15 18:3) were confirmed by mass spectrometry of their 4,4-dimethyloxazoline derivatives. Mass spectra of the cis-9, trans-13, cis-15 18:3 isomer was characterized by an intense ion at m/z 236 attributable to the formation of 2 stabilized allylic radical fragments, whereas this intense ion corresponding to the stabilized radical fragments was located at m/z 262 for the cis-9, trans-11, cis-15 18:3 isomer. The gap of 12 amu between m/z 250 and 262 confirmed the occurrence of a double bond in position delta13. Configuration of the double bonds of standards having similar mass spectra and gas-liquid chromatographic retention times was confirmed by 1H nuclear magnetic resonance. We also showed that both CLnA isomers were found in the muscle lipid extract, whereas only the cis-9, trans-11, cis-15 18:3 isomer was identified in the milk lipid extract. This study appears to be the first to identify 2 CLnA isomers in bovine muscle lipid extract.
Asunto(s)
Bovinos/fisiología , Leche/química , Músculos/química , Ácido alfa-Linolénico/metabolismo , Tejido Adiposo/química , Animales , Cromatografía de Gases/veterinaria , Cromatografía en Capa Delgada/veterinaria , Ácidos Grasos/metabolismo , Femenino , Hidrogenación , Isomerismo , Oxazoles , Ácido alfa-Linolénico/químicaRESUMEN
Conjugated linoleic acids (CLAs) such as rumenic acid (RA) have the potential to alter blood lipid profiles in animals and in humans. In contrast, physiological effects of conjugated α-linolenic acids (CLnAs), which concomitantly are omega-3 and conjugated fatty acids, are still unknown. The aim of this study was to evaluate the potential of CLnA to interfere in early steps of atherosclerosis by altering lipoprotein profiles and fatty streaks in the aortas. F1B hamsters were fed a control or one of the three hypercholesterolemic (HC) diets: HC-control, HC-RA (18:2 cis-9, trans-11) or HC-CLnA (CLnA: equimolar mixture of 18:3 cis-9, trans-11, cis-15 and cis-9, trans-13, cis-15) diet. In low-cholesterol control-fed hamsters, the proportion of high-density lipoprotein cholesterol (HDL-C) was around 45% while in HC-fed hamsters, HDL-C was around 10% and cholesterol was mostly (80%) carried by triglyceride-rich lipoproteins (TRL). Low-density lipoprotein (LDL) triglycerides (TGs) increased by approximately 60% in hamsters fed either HC-RA or HC-CLnA compared with HC-controls but not compared with the low-cholesterol control diet. HDL cholesterol decreased by 24% and 16% in hamsters fed HC-RA and HC-CLnA, respectively. Small dense LDL-cholesterol increased by approximately 60% in hamsters fed HC-RA and HC-CLnA compared with the HC-control group and by more than a 100% compared with hamsters on the control diet. The relative percentage of liver cholesteryl ester content increased by 88% in hamsters fed HC diets compared with the control diet. Significant differences in fatty streaks were observed between control and HC-diet-fed hamsters. However, no significant difference was observed among the HC-diet-fed hamsters. This study shows that animals fed any one of the HC diets developed an adverse lipoprotein profile compared with a normolipidic diet. Also, HC-RA or HC-CLnA diets altered lipoprotein profile compared with animals fed the HC-control diet but had no beneficial effects on atherosclerosis.
RESUMEN
Ruminal biohydrogenation of alpha-linolenic acid is not fully understood compared with that of linoleic acid. Some hypothetical intermediates, that is, conjugated isomers of alpha-linolenic acid (cis-9,trans-11,cis-15 and cis-9,trans-13,cis-15 18:3) have never been reported to occur in ruminant fat. Therefore, milk fat was analyzed using a combination of techniques to characterize alpha-linolenic acid biohydrogenation intermediates. Tandem off-line argentation thin-layer chromatography and high-resolution gas-liquid chromatography using a 120-m highly polar, open tubular capillary column coated with 70% cyanoalkyl polysiloxane equivalent material was used for quantification. Structural characterization of fatty acids was achieved by gas-chromatography mass-spectrometry after synthesis of specific azo-derivatives. This study confirmed that minute amounts of alpha-linolenic acid biohydrogenation intermediates are present in milk fat. Routes involved in biohydrogenation of linoleic and alpha-linolenic acids in the rumen and subsequent endogenous metabolism of related biohydrogenation products are discussed.
Asunto(s)
Grasas/química , Ácidos Linoleicos Conjugados/análisis , Leche/química , Ácido alfa-Linolénico/química , Ácido alfa-Linolénico/metabolismo , Animales , Ácidos Grasos Insaturados/análisis , Cromatografía de Gases y Espectrometría de Masas , Hidrogenación , Espectrometría de Masas , Oxazoles/análisis , Rumen/metabolismoRESUMEN
Rumenic (cis-9,trans-11 18:2) acid is the main conjugated linoleic acid (CLA) isomer in milk and other ruminant fats. Anhydrous regular and high-CLA butterfats were heated at 200 degrees C for 2, 4, and 6 h under atmospheric conditions. [1,5] Sigmatropic isomerization of rumenic acid occurred, resulting in the formation of trans-8,cis-10 18:2 acid, as determined by mass spectrometry of its 4,4-dimethyloxazoline derivative. Rate of isomerization was monitored by gas-liquid chromatography, using a 120-m capillary column coated with 70% equivalent cyanoalkylpolysiloxane polymer, and reaction was of first order. Furthermore, [1,5] sigmatropic rearrangement product analysis can be used as an indicator of heat treatment of natural fats and oils containing CLA.
Asunto(s)
Grasas/química , Ácidos Linoleicos Conjugados/análisis , Lípidos/análisis , Leche/química , Animales , Bovinos , Cromatografía de Gases , Ácidos Grasos/análisis , Cromatografía de Gases y Espectrometría de Masas , Isomerismo , Ácidos Linoleicos Conjugados/química , Oxazoles/químicaRESUMEN
A previously undescribed fatty acid, all-cis 7,11-20:2 (dihomotaxoleic acid, DHT), has been characterized by gas chromatography-mass spectrometry as being present (approximately 0.1%) in seed oils of two Taxaceae containing high levels (11-16%) of taxoleic acid (all-cis 5,9-18:2). This compound was absent from oils of 10 other conifer genera, as well as from one member of Taxaceae containing very low amounts of taxoleic acid, suggesting that DHT is a taxoleic acid elongation product.
Asunto(s)
Ácidos Grasos Insaturados/análisis , Plantas Medicinales , Semillas/química , Taxus/química , Ácidos Grasos Insaturados/química , Cromatografía de Gases y Espectrometría de Masas , Aceites de Plantas/análisis , Especificidad de la EspecieRESUMEN
Dibutyroyl derivatives of monoacylglycerols (DBMAG) from conifer seed oil triacylglycerols (TAG) were prepared by partial deacylation of TAG with ethylmagnesium bromide followed by diesterification with n-butyryl chloride. The resulting mixtures were analyzed by gas-liquid chromatography (GLC) with a 65% phenylmethyl silicon open tubular fused-silica capillary column operated under optimal conditions and separated according to both their fatty acid structures and their regiospecific distribution. Seed oils of 18 species from 5 conifer families (Pinaceae, Taxaceae, Cupressaceae, Cephalotaxaceae, and Podocarpaceae) were analyzed. The chromatograms showed a satisfactory resolution of DBMAG containing palmitic (16:0), stearic (18:0), taxoleic (cis-5,cis-9 18:2), oleic (cis-9 18:1), cis-vaccenic (cis-11 18:1), pinolenic (cis-5,cis-9,cis-12 18:3), linoleic (cis-9,cis-12 18:2), alpha-linolenic (cis-9,cis-12,cis-15 18:3), and an almost baseline resolution of DBMAG containing gondoic (cis-11 20:1), cis-5,cis-11 20:2, sciadonic (cis-5,cis-11,cis-14 20:3), dihomolinoleic (cis-11,cis-14 20:2), juniperonic (cis-5,cis-11,cis-14,cis-17 20:4), and dihomo-alphalinolenic (cis-11,cis-14,cis-17 20:3) acids. We have observed that results for Pinus pinaster and P. koraiensis seed oils obtained with this new simple method compared favorably with literature data established with other usual regiospecific analytical techniques. Delta5-olefinic acids are esterified mainly at the external positions of the glycerol backbone in all cases, in agreement with data obtained by other methodologies allowing validation of the GLC regiospecific method. To date, 45 gymnosperm species (mostly Coniferophytes) from 21 genera belonging to 9 families have been analyzed, all of them showing a definite enrichment of delta5-olefinic acids in the external positions of TAG. These fatty acids (FA), with one exception only, represent between approximately 2 and 8% of FA esterified to the internal positions. For some species, i.e., P. koraiensis and P. pinaster, this asymmetrical distribution was established by at least three analytical procedures and confirmed by stereospecific analysis of their seed TAG.
Asunto(s)
Alquenos/análisis , Cromatografía de Gases/métodos , Cromatografía Líquida de Alta Presión/métodos , Cycadopsida/química , Semillas/química , Triglicéridos/análisis , Alquenos/química , Ácidos Grasos/análisis , Isomerismo , Reproducibilidad de los Resultados , Triglicéridos/químicaRESUMEN
Chitosan treatment (2-8 mg/mL) of wheat seeds significantly improved seed germination to recommended seed certification standards (>85%) and vigor at concentrations >4 mg/mL, in two cultivars of spring wheat (Norseman and Max), by controlling seed-borne Fusarium graminearum infection. The germination was <80% in the control and >85% in benomyl- and chitosan-treated seeds. Seed-borne F. graminearum was reduced to >50% at higher chitosan treatments compared to the control. Synthesis of phenolic acids was stimulated in primary leaves following chitosan treatment, and levels of these phenolic acids, especially ferulic acid, increased significantly with increasing chitosan concentration. Lignin content of primary leaves also showed a similar pattern. The synthesis of precursors of lignin such as p-coumaric, ferulic, and sinapic acids and phenolic acids having antimicrobial activity such as benzoic, p-coumaric, caffeic, protocatechuic, chlorogenic, ferulic, and gallic acids was also stimulated by chitosan treatment. The induction of phenolic acids and lignin was significantly lower in cv. Max compared to Norseman. Chitosan also inhibited fungal transmission to the primary roots of germinating seedlings. Results suggest that chitosan controlled seed-borne F. graminearum infection and increased the resistance in seedlings by stimulating the accumulation of phenolics and lignin. Thus, chitosan has a potential for improvement of seed quality and enhancement of crop yields as well as increased value of stored grains for food and feed.
Asunto(s)
Quitina/análogos & derivados , Fungicidas Industriales/farmacología , Fusarium/patogenicidad , Triticum/efectos de los fármacos , Triticum/microbiología , Benomilo/farmacología , Quitina/farmacología , Quitosano , Lignina/biosíntesis , Fenoles/metabolismo , Hojas de la Planta/metabolismo , Semillas/efectos de los fármacos , Semillas/microbiología , Triticum/fisiologíaRESUMEN
Bovine milk fat was fractionated using preparative reversed-phase high-performance liquid chromatography. The conditions consisted of two successive linear gradients of acetonitrile and tert-butylmethylether, followed by a final isocratic mixture of the two eluants, leading to triacylglycerols grouped by their partition number (PN). Fractions corresponding to partition numbers 32 to 50 were isolated and analyzed for fatty acid distribution between sn-1,3 and sn-2 positions by Grignard degradation. Results showed that the fatty acid distribution in milk fat triacylglycerols is nonrandom. The distribution of short-chain fatty acids, stearic (predominantly at sn-1,3 position) and palmitic (predominantly sn-2 position), did not change with triacylglycerol size. Medium-chain fatty acids were predominantly located at sn-2 position, but their proportion at this position decreased with triacylglycerol size. Oleic acid distribution was also size-dependent in that it was located in high proportions at sn-2 position in smaller triacylglycerols and vice versa. Results also showed that the sn-2 position was more unsaturated than sn-1,3 position in the PN range from 32 to 40, but it was more saturated in triacylglycerols with higher PN.