Goat Milk Fat Research Articles

Características microbiológicas e físico-químicas do leite de cabra submetido à pasteurização lenta pós-envase e ao congelamento

O objetivo principal deste trabalho foi avaliar o efeito da pasteurização lenta (65°C 30min-1) em banho-maria e do congelamento (-18°C), seguido de estocagem por uma semana (-18°C), sobre as características microbiológicas e físico-químicas do leite de cabra pré-embalado. Quinze amostras individuais de leite de cabra foram analisadas antes e após o processamento, realizado no próprio capril. A pasteurização lenta mostrou-se eficaz na redução da contaminação por mesófilos, psicrotróficos e fungos, mas a baixa contagem de coliformes fecais e totais do leite cru não proporcionou a mesma eficácia neste grupo de bactérias. O armazenamento do leite congelado durante uma semana não alterou a sua qualidade microbiológica. Não se observou influência significativa do processamento térmico sobre as concentrações dos principais constituintes do leite ou sobre as propriedades físico-químicas analisadas. Os resultados obtidos nesse experimento mostraram também que um equipamento de leitura infra-vermelha calibrado com leite bovino pode ser usado para a determinação dos teores de gordura e proteína do leite de cabra.

The effect of dietary inclusion of olive tree leaves and grape marc on the content of conjugated linoleic acid and vaccenic acid in the milk of dairy sheep and goats

Olive tree leaves (OTL) and grape marc (GM) are by-products with high linolenic (LNA) and linoleic (LA) acid content, respectively, which can be used as dietary ingredients to increase the cis-9 trans-11 conjugated linoleic acid (CLA) content of milk fat in sheep and goats. An experiment was conducted with 16 Friesian ewes and 16 Alpine goats to study the effect of OTL and GM inclusion in sheep and goat diets on their milk fatty acid profile, with emphasis on cis-9, trans-11 CLA and vaccenic acid (VA). Ewes and the goats were fed the control (C) diets from parturition to the 90 days in milk (DIM) and then both groups were divided into two sub-groups (treatments). The control groups of both species continued to be fed the C diets, whereas the treated groups were gradually switched over a 2-week period (DIM=91-105) from the C diets to that of treatment 1, which contained air-dried OTL. These OTL diets were fed ad libitum for 1 month (DIM=106-135). After that period, the same treated groups, after 2 weeks of gradual adaptation (DIM=136-150), were switched to treatment 2, which contained air-dried GM. The GM diets were fed ad libitum for 1 month (151-180 DIM). Concentrations of polyunsaturated fatty acids (PUFA) and mono-unsaturated fatty acids increased significantly in milk fat of sheep fed OTL v. C. For goats, only the PUFA in milk fat was increased by feeding OTL compared with C. Relative to C, GM increased significantly the concentration of PUFA only in milk fat of sheep. OTL and GM diets increased the cis-9, trans-11 CLA and VA content in milk fat, compared with C, only in sheep. GM caused a sharp increase in 18:0 only in sheep milk fat, while the OTL diet increased significantly the 18:0 in milk fat of goats. GM and OTL diets also had opposite effects on the 18:1/18:0 ratio of sheep milk fat. In conclusion, OTL and GM, when included in sheep diets altered the milk fatty acid profile with a pronounced increase in cis-9, trans-11 CLA and VA contents. The results show that the response of sheep and goats to OTL and GM diets was different, suggesting a species difference that needs further investigation.

Crystallization Properties and Polymorphism of Triacylglycerols in Goat’s Milk Fat Globules

The sensorial, functional, and nutritional properties of goat dairy products result from the specific fatty acid composition of goat's milk fat. However, information on the physical and thermal properties of goat's milk fat is scarce. In this study, crystallization of triacylglycerols (TG) in goat's milk fat globules was investigated using polarized light microscopy and the coupling of time-resolved synchrotron radiation X-ray diffraction (XRD) and high-sensitivity differential scanning calorimetry (DSC). The molecular organization of the solid fat phase was characterized for cooling rates between 3 and 0.1 degrees C/min. Quenching of goat's milk fat globules from 50 to -8 degrees C and 4 degrees C was also examined to identify the most unstable polymorphic forms of TG. Then, the melting behavior of fat crystals was studied on subsequent heating at 1 degrees C/min. Triple chain length (3L: 68.6-70 A) and double chain length (2L: 37-45.4 A) structures were characterized and 5 polymorphic forms, alpha, sub-alpha, beta' 1, beta' 2, and beta were identified. Polymorphic transitions were observed within goat's milk fat globules as a function of time after quenching and as a function of temperature on heating. From a technological point of view, this work will contribute to a better understanding of the rheological properties as well as on the flavor evolutions of goat's milk-based products.

Screening, cloning and sequence analysis ofgBTN1A1gene in mammary gland of Xinong Saanen goat

AbstractButyrophilin 1A1 (BTN1A1), which is a member of the Ig superfamily, is highly expressed in the lactating mammary gland and is secreted into milk in association with lipid droplets, and concentrated in the apical plasma membranes of mammary epithelial cells. Because butyrophilin is expressed only during lactation, it appears to be essential for milk fat globule production. However, there is little information about its properties in the dairy goat. The objective of this study was to confirm whether butyrophilin was related to milk changes in different lactation periods of Xinong Saanen goats. Using suppression subtractive hybridization analysis, we identified a significant increase in butyrophilin mRNA in Xinong Saanen goat mammary gland at middle lactation when compared to that of late lactation. The gBTN1A1 complementary DNA has an open reading frame of 1581 nucleotides encoding a putative protein of 526 amino acids. Amino acids 1–26 were the signal peptide domain. The homologies of nucleotide and peptide sequences of goat butyrophilin with bovine (NM_174508), human (NM_001732) and mouse (AK145168) butyrophilin were 97 and 96%, 88 and 84%, 84 and 70%, respectively. The secondary structure, transmembrane domain and hydrophilicity of goat butyrophilin were similar to the those of the bovine, human and mouse protein. In conclusion, we confirmed that the goat mammary gland mRNA level of gBTN1A1 was responsible for goat milk fat globule secretion.

Diet, rumen biohydrogenation and nutritional quality of cow and goat milk fat

AbstractThe potential to modify the milk fatty acid (FA) composition by changing the cow or goat diets is reviewed. Ruminal biohydrogenation (RBH), combined with mammary lipogenic and Δ‐9 desaturation pathways, considerably modifies the profile of dietary FA and thus milk composition. The pasture has major effects by decreasing saturated FA and increasing FA considered as favorable for human health (c9‐18:1, 18:3n‐3 andc9t11‐CLA), compared to winter diets, especially those based on maize silage and concentrates. Plant lipid supplements have effects similar to pasture, especially linseed, but they increase to a larger extent, simultaneously severaltransisomers of 18:1 and, conjugated or non‐conjugated 18:2, especially when added to maize silage or concentrate‐rich diets. The goat responds better for milk 18:3n‐3 andc9t11‐CLA, and sometimes less forc9‐18:1, and is less prone to the RBHtrans‐11 totrans‐10 shift, which has been shown to be time dependent in the cow. The respective physiological roles of most milktransFA have not been studied to date, and more studies in rodents and humans fed dairy products modified by changing ruminant diet are required before recommending a larger use of lipid sources and how to combine them with the different feeding systems used by dairy farmers.

FEED ADDITIVES INNUTRITION OF ORGANIC GOAT

Goats fed on high quality and valuable forage provide the production of high quality milk and dairy product Improper and poor feeding during lactation period reduce milk yield, weaken animal’s organism, has an influence on breeding and fertility ability and metabolic processes in goats. The goal of our research was to assess the influence of different feed additives on organic goat milk productivity and quality indices. In Latvian local goat feeding of sunflower cake and buckwheat meal increased milk yield by 7,3%, reduced feed units by 3,8% and by 5,2% reduced consumption of digestible protein as well as increased milk fat and protein content in goat milk by 10% and 4,7%> respectively compare to control. Feeding of wheat bran and buckwheat meal increased milk yield by 5,4%>, reduced feed units by 1,5% and by 3,0% reduced consumption of digestible protein as well as increased protein content in goat milk by 3,0% compare to control. Results of milk analysis on milk cells cytology and immunity indices show that feed additives used, and particularly sunflower cake and buckwheat meal, have a beneficial effect on immunity in animal organism.

Enantioselective Determination of Anteiso Fatty Acids in Food Samples

Anteiso fatty acids (aFAs)-long-chain carboxylic acids with a methyl branch on the (n - 2)-carbon-are among the most simple fatty acids that are chiral. The most frequently occurring aFAs in food are 12-methyltetradecanoic acid (a15:0) and 14-methylhexadecanoic acid (a17:0), structures where the asymmetric carbon is more than 10 carbons separated from the polar head group. Previously, only enantioseparation of 4-methyl-substituted carboxylic fatty acids has been reported by gas chromatography. Here we present the first direct partial enantioresolution of synthesized racemic a15:0-a17:0 on a capillary column coated with 50% heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin diluted in OV1701. Synthesized (S)-(+)-enantiomers were used to demonstrate that the elution order was (R)- prior to (S)-enantiomers. Using this system, food samples (butter, goat's milk fat, suet, human milk, seal oil, cod liver oil) known to contain aFAs were analyzed. Prior to the enantioselective gas chromatography, unsaturated fatty acids were preseparated by urea complexation, silver ion high performance liquid chromatography (Ag+-HPLC), or both from food samples. The fractions of the food samples enriched with methyl-branched fatty acids were then analyzed by GC/MS in the SIM mode. The measurements confirmed that the (S)-enantiomer of a15:0 (ee >96%), a16:0, and a17:0 (ee >90%, respectively) dominated in all samples. While the (R)-enantiomers could not be identified in samples from ruminants and human milk, their presence could be established in cod liver and seal oil (ee <86%).

Anhydrous Goat's Milk Fat: Thermal and Structural Behaviors Studied by Coupled Differential Scanning Calorimetry and X-ray Diffraction. 2. Influence of Cooling Rate

Crystallization and melting properties of triacylglycerols (TGs) in anhydrous goat's milk fat (AGMF) are investigated by X-ray diffraction as a function of temperature (XRDT) coupled with high-sensitivity differential scanning calorimetry (DSC), using synchrotron radiation and Microcalix. The polymorphic behavior of AGMF was monitored by varying the cooling rates between 5 and 1 degrees C/min from 45 to -20 degrees C with their subsequent melting at 1 degrees C/min. Quenching of AGMF at -20 degrees C was also examined to determine the metastable polymorphic form of AGMF. At intermediate cooling rates, TGs in AGMF crystallize, from about 18 degrees C in two different lamellar structures with triple chain length 3Lalpha stacking of 72 A and a double chain length 2Lalpha stacking of 48 A, which are correlated to two overlapped exothermic peaks recorded by DSC. A reversible transition sub alpha <--> alpha was observed. Subsequent heating at 1 degrees C/min shows numerous structural rearrangements before final melting. At fast cooling of AGMF (5 degrees C/min), similar unstable crystalline varieties are formed while three endotherms are recorded. Several new unstable lamellar structures are observed after quenching. All of these data are compared to those previously reported at slow cooling (0.1 degrees C/min) showing a relative stability of the structures formed. In spite of general similitude, the thermal and structural behavior of the goat's milk is more complex than that of the cow's milk.

Goat's alpha-s1 casein genotype influences its milk fatty acid composition and delta-9 desaturation ratios

A large number of studies about impacts of alpha-s1 (αs1) casein (CSN1S1) gene polymorphism on goat milk composition, including its milk fat concentration, secretion in mammary cells and transcriptome analysis, have been reported. Despite this knowledge, very little data is available on the fatty acid (FA) composition of goat milk according to the CSN1S1 genotype. The study reported here compares two groups of 33 and 38 goats with different CSN1S1 genotypes, associated respectively with low or high milk protein and fat concentrations, matched for lactation stage and diets. Results confirm the lower milk protein (−5.0 g/kg) and fat (−6.8 g/kg) concentrations in the Low genotype group, whereas milk yield and its lactose concentration were not changed. There were between-group differences in proportions in milk fat of at least 17 FA, particularly the C8–C12 saturated FA and palmitic, stearic, oleic, linoleic and rumenic acids. In addition, delta-9 desaturation ratios were higher in the Low CSN1S1 group for C10:0, C14:0, C17:0, C18:0, trans11-C18:1 and trans13-C18:1, which strongly suggests an effect on mammary desaturase activity, especially for C18:0 and trans11-C18:1. It is likely that higher delta-9 desaturation ratios for C10:0 to transC18:1 isomers in the Low genotype could compensate for the lower secretion of medium-chain FA (C8:0 to C12:0), thus contributing to maintenance of the melting point of milk fat in this genotype. The polymorphism in the CSN1S1 genotype has important impacts on goat milk fat, and its FA composition, possibly making the goat model of interest in the search for a better understanding of regulation of mammary function, in particular FA synthesis, desaturation and secretion, and how it could be related to protein synthesis and secretion.

Application of Ethyl Esters and d3-Methyl Esters as Internal Standards for the Gas Chromatographic Quantification of Transesterified Fatty Acid Methyl Esters in Food

Ethyl esters (FAEE) and trideuterium-labeled methyl esters (d3-FAME) of fatty acids were prepared and investigated regarding their suitability as internal standards (IS) for the determination of fatty acids as methyl esters (FAME). On CP-Sil 88, ethyl esters of odd-numbered fatty acids eluted approximately 0.5 min after the respective FAME, and only coelutions with minor FAME were observed. Depending on the problem, one or even many FAEE can be added as IS for the quantification of FAME by both GC-FID and GC-MS. By contrast, d3-FAME coeluted with FAME on the polar GC column, and the use of the former as IS requires application of GC-MS. In the SIM mode, m/z 77 and 90 are suggested for d3-methyl esters of saturated fatty acids, whereas m/z 88 and 101 are recommended for ethyl esters of saturated fatty acids. These m/z values give either no or very low response for FAME and can thus be used for the analysis of FAME in food by GC-MS in the SIM mode. Fatty acids in sunflower oil and mozzarella cheese were quantified using five saturated FAEE as IS. Gravimetric studies showed that the transesterification procedure could be carried out without of loss of fatty acids. GC-EI/MS full scan analysis was suitable for the quantitative determination of all unsaturated fatty acids in both food samples, whereas GC-EI/MS in the SIM mode was particularly valuable for quantifying minor fatty acids. The novel GC-EI/MS/SIM method using fatty acid ethyl esters as internal standards can be used to quantify individual fatty acids only, that is, without determination of all fatty acids (the common 100% method), although this is present. This was demonstrated by the exclusive quantification of selected fatty acids including methyl-branched fatty acids, erucic acid (18:1n-9trans), and polyunsaturated fatty acids in cod liver oil and goat's milk fat.

Concentration of conjugated linoleic acid in grazing sheep and goat milk fat

Abstract The conjugated linoleic acid (CLA) content of grazing sheep and goat milk fat, throughout their lactation period, was examined. Six sheep and six goat representative farms were selected at random and milk samples were taken at monthly intervals for fatty acids profile determination. Sheep and goat nutrition was based on natural grazing and on supplementary feeding during the winter months. From April onwards, grazing native pastures was the only source of feed for sheep and goats. The University farm whose sheep are kept indoors all year round without any grazing, was also used as reference. Fifteen individual milk samples were also taken in April from a sheep and goat farm respectively, in order to see the variability of CLA inside the farm. The results showed that: a. the CLA content of grazing sheep and goat milk fat increased significantly in April–May (early growth stage of grass) and then declined while that of indoors kept sheep was more or less constant during the same period, b. the isomers cis-9, trans-11 and trans-10, cis-12 of CLA were found in grazing sheep milk fat, while in indoors kept sheep and goats' milk fat only the cis-9, trans-11 isomer was found, c. the CLA content of sheep milk fat was much higher than that of goats, d. a negative correlation between sheep milk fat and CLA content was found and e. there was considerable variation in milk fat CLA content between sheep and goat farms and inside the farms.

Anhydrous Goat's Milk Fat: Thermal and Structural Behavior. 1. Crystalline Forms Obtained by Slow Cooling

The thermal and structural behaviors of anhydrous goat's milk fat (AGMF) have been determined as a function of temperature using a powerful technique allowing simultaneous time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) and high-sensivity differential scanning calorimetry (DSC) measurements from the same sample. This first paper, aiming at the characterization of the physical properties of AGMF, we examine crystalline organizations made by triacylglycerols (TG) upon slow cooling at /dT/dt/ = 0.1 degrees C/min from 45 to -20 degrees C in order to approach system equilibrium. Three overlapped exotherms were observed by DSC upon cooling, whereas four endotherms were found on the subsequent heating at 1 degrees C/min. XRDT evidenced that AGMF crystallizes under four different lamellar structures, two with double-chain length packings at 41.5 and 38.2 angstroms and two with triple-chain lengths of 72 and 64.7 angstroms stacking. Simultaneous wide-angle XRDT has shown that initial nucleation mainly occurs in a packing of beta' type from approximately 26 degrees C, although some transient presence of alpha was detected. The absence of polymorphic transition, on heating, until final melting (approximately 40 degrees C) demonstrated the relative stability of the structures formed.

PHYSICOCHEMICAL CHARACTERISTICS OF BINARY MIXTURES OF HYDROGENATED PALM KERNEL OIL AND GOAT MILK FAT

ABSTRACT The changes in physicochemical characteristics of fat blends containing hydrogenated palm kernel oil (HPKO) and goat milk fat (GMF), before and after chemical interesterification using sodium methoxide as catalyst, was evaluated. HPKO : GMF blends were prepared in six ratios: 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 (w/w). Melting characteristics were studied by differential scanning calorimetry. Peak melting temperatures (Tp) of noninteresterified blends decreased as the percentage of GMF increased. Generally, the interesterified blends showed lower Tpvalues compared to the noninteresterified blends at their respective blending ratios. Decrease in melting enthalpy (Ep) occurred with the increase in percentage GMF in the blends for both the noninteresterified and interesterified blends. Interesterified blends had greater Epvalues than those of the noninteresterified blends at respective ratios. Results from X‐ray diffraction analysis showed that all blends possessed a β′ polymorph. HPKO : GMF (0:100) was the only blend in which the presence of both β′ and β polymorphs was detected. Chemical interesterification had no effect on polymorphic crystal behavior. Based on solid fat content (SFC) results, eutectic effect did not occur in all HPKO : GMF blends studied. It was shown that the percentage of SFC decreased as percentage of GMF increased. Decrease in percentage SFC of blends was brought about by interesterification. The HPKO : GMF (100:0) blend had the highest percentage of free fatty acid followed by HPKO : GMF (0:100). Interesterification caused a 2‐ to 3‐fold increase in the percentage of free fatty acids compared to noninteresterified blends. Iodine values of the blends increased with an increase in GMF proportion. A rapid increase in iodine was observed in blends containing 0–20% GMF. Interesterification did not have any effect on the iodine value of fat blends.

The relationship between quality criteria of goat milk, its technological properties and the quality of the final products

This paper presents the main criteria that enable the control of milk quality criteria that are included in a payment system based on goat milk quality, with regard to hygienic quality and the technological and sensorial impacts on the final products. Somatic cells, often linked to mastitis and thus to pathogens when the count is high, induce changes of the biochemical composition of milk. However, somatic cell count (SCC) does not seem to impair either cheese-making or sensorial characteristics of the cheeses for SSC close to 1,800,000 cells/ml. Some problems could, nevertheless, occur for the production of high heat-treated milks. The presence of colostrum (IgG) could impair heat-treated fluid milk production, while inhibiting substances could impair the fermentation process. Taking into account the great variability of natural inhibiting substances contained in goat milk, the bovine test applied to goat milk should be adapted. Bacteria count gives a good estimation of the hygienic quality of milk and although pathogens are also included in payment systems, these are not discussed. Nevertheless, different classes of bacteria should be distinguished due to the specific character or change each may cause, for example, psychrotrophic bacteria, which may produce heat resistant protease and lipase and induce organoleptic defects in goat milk products. The fat and protein contents in goat milk have been improved through genetics and feeding programmes. Protein percentage, however, is not a precise criterion to predict and ensure cheese yield. Casein percentage would be a more precise criterion to ensure cheese yield. The lipolysis of goat milk can be a useful optional criterion to ensure the quality of non-ripened lactic cheeses.

Modification of Physicochemical Characteristics of Goat Milk Fat by Feeding Protected High Oleic Sunflower Oil Supplements

ABSTRACT: Protein-oil supplements containing high oleic sunflower oil (HOSO) and different proteins were prepared and fed to lactating goats. Milk fat from goats on basal diet had 12.5% oleic acid (C18:1n9), but C18:1n9 increased (P < 0.05) to 19.0% on the keratin protein-oil supplement diet, 19.2% on the casein protein-oil supplement diet, and 25.2% on dry casein (DC) protein-oil supplements diet. Feeding protein-oil supplements increased (P < 0.05) levels of triacylglycerols with 46 and 50 carbons in milk fat and decreased (P < 0.05) solid content in milk fat at 10°C from 34.8% to 23.0% for DC, to 26.5% for casein, and to 29.6% for keratin. The DC protein-oil supplement diet might produce spreadable butter out of the refrigerator.

Effect of feeding systems on composition of goat milk and yield of Domiati cheese

Twenty lactating Alpine goats were randomly allocated to four treatment groups to investigate the effect of pasture feeding with different levels of concentrates on composition of Alpine goat milk and quality of Domiati cheese during lactation. Goats in Group A were confined and fed alfalfa hay with 0.66 kg/day of concentrate mixture per 1.5 kg of milk. Groups B, C and D were rotationally grazed and received 0.66, 0.33, and 0 kg/day of concentrate supplementation, respectively. Milk from each group was processed into Domiati soft cheese twice monthly for a 6-month lactation period. Fresh cheese samples were evaluated for sensory quality. The results obtained from this experiment indicated that goats fed a high concentrate level with pasture grazing (Group B) produced milk with significantly higher contents of fat, protein and total solids and thus had a higher cheese yield than goats kept on pasture alone (Group D) or under a confined feeding system with concentrate and hays (Group A). The change of Domiati cheese yield over lactation followed the same trends of fat, protein and total solids in goat milk. The chemical composition of Alpine goat milk and the yield of Domiati cheese varied significantly during lactation, with high values in the early and the late lactations. Contents of milk fat, protein and total solids were highly positively correlated with Domiati cheese yield. The milk fat content had an adverse effect on the cheese flavor score while the level of total fatty acids in milk was positively correlated with the flavor score. Further research is needed to investigate the economical efficiency of milk production using concentrate supplementation to lactating goats and the processing functionalities of goat milk for cheese manufacturing.

Influences of Olive Oil and Ghee (samen balady) on Serum Cholesterol of Jordanians

The effects of olive oil (OO) and ghee types (semen balady) on the serum lipid profile were studied in healthy volunteers (11 males, aged 36-44 year; 13 females aged 27-35 year). The 24 subjects ate their habitual diet with OO or ghee of cow milk fat (CMF), ghee of goat milk fat (GMF) or ghee of sheep milk fat (SMF) for 4 wk with 4 wk interval between the four diets. Compared with initial values, OO diet significantly (P<0.05) reduced concentrations of serum total cholesterol (TC, -3.42%) and low density lipoprotein cholesterol (LDL-c, -4.31%). OO caused slight reduction in concentration of high density lipoprotein cholesterol (HDL-c, -2.86%), and ratios of TC/HDL-c and LDL-c/HDL-c. Whereas ghee types significantly (P<0.05) increased these parameters and the SMF resulted in the highest rise of TC (+11.93%) and LDL-c (+16.16%). The highest rise in concentration of HDL-c (+8.81%) was shown with GMF. Ghee types slightly increased the ratios of TC/HDL-c and LDL-c/HDL-c compared with the initial values. SMF resulted in the highest rise of TC/HDL-c (+0.26) and LDL-c/HDL-c (+0.31) Serum triglycerides level increased (+3.38 %) after OO diet, whereas reduced (about -2.15%) after periods of ghee types. In general, the responses in serum lipids were greater in males than in females in all the four diets.

13C NMR spectra of TAG: An easy way to distinguish milks from different animal species

AbstractIn order to differentiate milks from different species, we carried out a comparative analysis of TAG from cow, buffalo, goat, and sheep milk fat based on13C NMR experiments. NMR spectroscopy, although less sensitive than other techniques, does not require an extensive chemical manipulation of samples and can easily highlight the differences in the content of short‐chain acyl groups in the four milk species. The resonances were assigned and quantified, and by using only three NMR parameters in data clustering with fuzzy logic analysis, we were able to distinguish goats' milk from sheep's milk, and both of these milks from cows' and buffaloes' milks. This appears to be an important result, considering the ease and rapidity with which milk identification can be obtained. From13C NMR spectra of TAG, the positional distribution of FA chains on the glycerol backbone can also be easily evaluated. In particular, analysis of the positional distribution of monounsaturated FA revealed that it may be species‐specific, and we are currently analyzing larger data sets in order to evaluate the use of this parameter as a suitable approach to address the issue of milk authenticity.

Occurrence of trans-C18:1 Fatty Acid Isomers in Goat Milk: Effect of Two Dietary Regimens

Trans-octadecenoic acid composition of goat milk fat was studied by using silver-ion thin layer chromatography combined with gas-liquid chromatography. This analytical procedure also was used to investigate the effect of diet on trans-C18:1 fatty acid content in goat milk. Thirty-two goats were used in a 2 x 2 factorial arrangement and treatments. Two groups of goats received alfalfa hay at either a high or a low level of forage and two other groups received Rumiluz (dehydrated alfalfa from France Luzerne, Châlon en Champagne, France) at either a high or a low level of forage. Trans-C18:1 isomer proportions (relative to total fatty acids) were, respectively, 2.02% for the Rumiluz low-level group and 1.75% for the Rumiluz high-level group versus 1.71% for the alfalfa low-level group and 1.21% for the alfalfa high-level group. Goats fed on Rumiluz thus produced relatively higher levels of trans-C18:1 fatty acids than animals fed alfalfa hay. The results also showed that production of trans-C18:1 fatty acids increased when the level of forage in the diet decreased. Moreover, goat milk trans-C18:1 composition appeared similar to the cow milk profile. Vaccenic acid, trans-11-C18:1, was the major component and represented about 36.2% of total trans-C18:1 isomers.

Study of individual trans- and cis-16:1 isomers in cow, goat, and ewe cheese fats by gas-liquid chromatography with emphasis on the trans-delta3 isomer.

Low-temperature gas-liquid chromatography (GLC) was applied to study the distribution profiles of isomeric trans- and cis-hexadecenoic acids in ruminant (cow, goat, and ewe) milk fat after their fractionation by argentation thin-layer chromatography (Ag-TLC). The fat was extracted from cheeses (12 samples of each species), the most common foods made with goat and ewe milks. The predominant trans-16:1 isomer is palmitelaidic acid (the delta9 isomer), but it does not exceed one-third of the total group, which itself represents 0.17% (cow), 0.16% (goat), and 0.26% (ewe) of the total fatty acids. The trans-delta3 16:1 isomer, which is reported for the first time in ruminant lipids and which likely comes from the animals' feed, is present at a level of ca. 10% of the trans-16:1 acid group. Otherwise, all isomers with their ethylenic bond between positions delta4 and delta14 are observed in the three species studied, roughly showing the same relative distribution pattern. Quantitatively, the trans-16:1 isomers only represent ca. 5% of the sum of the trans-16:1 plus trans-18:1 isomers, and they appear of little importance in comparison. It is inferred from this and recent studies that some previously reported data that were established for consumption assessments dealt in fact mainly with iso-17:0 acid, which was confused with (and added to) trans-delta9 (palmitelaidic) acid; consequently, these results were large over-estimates. Regarding the cis-16:1 acids, the delta9 isomer is the prominent constituent as expected, but the second-most important isomer is the delta13 isomer. It does not appear that trans-16:1 isomers are from ruminant milk fats of great nutritional importance as compared with trans-18:1 isomeric acids. As for trans18:1 isomers, the combination Ag-TLC/GLC is a necessary procedure to quantitate trans-16:1 acids accurately and reliably. Ag-TLC allows removal of interfering branched 17:0 acids and cis-16:1 acids, and low-temperature GLC permits an accurate measurement of all individual isomers most of which with baseline resolution.