Chemical, physical, and sensory properties of dairy products enriched with conjugated linoleic acid

Recent studies have illustrated the effects of cis-9,trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9,trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9,trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg (on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18:0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsatu-rated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.     

Investigation of the migration of triclabendazole residues to milk products manufactured from bovine milk,and stability therein,following lactating cow treatment

Triclabendazole (TCB) is a flukicide used in the treatment of liver fluke in cattle; however, its use is currently prohibited in lactating dairy cows. In this study, following administration of 10% Fasinex (triclabendazole, Novartis Animal Health UK Ltd., Camberley, UK) the milk of 6 animals was used to manufacture dairy products, to ascertain if TCB residues in milk migrate into dairy products. The detection limit of the ultra-high-performance liquid chromatography-tandem mass spectrometry method used was 0.67 μg/kg. The highest concentrations of TCB residue measured, within the individual cow milk yield, was 1,529 ± 244 µg/kg (n = 6), on d 2 posttreatment. Days 2 and 23 posttreatment represented high and low residue concentrations, respectively. At each of these 2 time points, the milk was pooled into 2 independent aliquots and refrigerated. Milk products, including cheese, butter, and skim milk powder were manufactured using pasteurized and unpasteurized milk from each aliquot. The results for high residue milks demonstrated that TCB residues concentrated in the cheese by a factor of 5 (5,372 vs. 918 µg/kg for cheese vs. milk) compared with the starting milk. Residue concentrations are the sum of TCB and its metabolites, expressed as keto-TCB. Residues were concentrated in the butter by a factor of 9 (9,177 vs. 1,082 μg/kg for butter vs. milk) compared with the starting milk. For milk, which was separated to skim milk and cream fractions, the residues were concentrated in the cream. Once skim milk powder was manufactured from the skim milk fraction, the residue in powder was concentrated 15-fold compared with the starting skim milk (7,252 vs. 423 µg/kg for powder vs. skim milk), despite the high temperature (185°C) required during powder manufacture. For products manufactured from milk with low residue concentrations at d 23 posttreatment, TCB residues were detected in butter, cheese, and skim milk powder, even though there was no detectable residue in the milk used to manufacture these products. Triclabendazole residues were concentrated in some milk products (despite manufacturing treatments), exceeding residue levels in the starting milk and, depending on the storage conditions, may be relatively stable over time.     

Tetracycline antibiotics transfer from contaminated milk to dairy products and the effect of the skimming step and pasteurisation process on residue concentrations

The presence of antibiotics in raw milk and milk derivatives poses a threat to human health and can negatively affect the dairy industry. Therefore, the main object of this study was to investigate the transfer of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC) and doxycycline (DC) from raw, experimental milk contaminated with tetracyclines (TCs) to different dairy products: cream, butter, buttermilk, sour milk, whey, curd and cheese. Additionally the effect of the skimming process on TCs concentrations was tested, as well as the influence of low-temperature long-time pasteurisation. The analyses of TCs in milk and dairy products were performed by an LC-MS/MS method. In order to determine TCs residues in dairy products, an analytical method was developed with the same extraction step for all matrices. TCs molecules were inhomogenously distributed between the milk derivative fractions. The highest concentrations were determined in curd and cheese in the ranges 320–482 µg/kg and 280–561 µg/kg, respectively. Low levels of TCs in butter and whey were observed (11.8–41.2 µg/kg). TCs were found in sour milk (66.0–111 µg/kg), cream (85.0–115 µg/kg) and buttermilk (196–221 µg/kg) at much higher levels than in butter and whey, but lower than in curd and cheese. During the skimming process, the highest yield of cream was obtained after the raw milk was held at 2–8°C for 24 h. The differences in concentrations of TCs between whole milk and skimmed milk, expressed as percentages of recovery, were below 19% (recoveries in excess of 81%). The highest content was observed in milk and cream skimmed at 2–8°C. The degradation percentages for TCs during the pasteurisation process (63°C for 30 min) were below 19%.     

Carotenoids and retinoids in Finnish foods: dairy products and eggs

As part of an overall composition study of Finnish foods, the carotenoid and retinoid content of 20 dairy product samples and eggs were determined by HPLC. The total beta-carotene (all-trans beta-carotene plus 15-cis beta-carotene) was quantitated for dairy products. For egg and egg yolk, lutein content was also determined. Only traces of lycopene, cryptoxanthin, and alpha-carotene were present. All-trans retinol and 13-cis retinol were the major retinoids in dairy products. Small amounts of 9-cis, 11-cis, and 9,11-cis retinols were found. High values of both retinol and beta-carotene were found in full fat cheeses and whipping cream: from 179.0 (cheese, Edam-type) to 318.7 micrograms/100 g (whipping cream) and from 86.7 (cheese, Edam-type) to 186.5 micrograms/100 g (whipping cream) for all-trans retinol and total beta-carotene, respectively. The retinol content averaged 16.3, 32.6, and 52.2 and that of beta-carotene 9.6, 16.7, and 3.0 micrograms/100 g in milk (1.9% fat), milk (3.9% fat), and human milk, respectively. The major pigment in eggs and egg yolk was lutein, 619.5 micrograms/100 g in eggs and 1575.8 micrograms/100 g in egg yolk. According to this study, at the present level of consumption in Finland, milk, milk products (excluding butter), and eggs result in a daily intake of about 350 retinol equivalents, and consequently, are a major source of vitamin A.     

Method for determination of aflatoxin M₁ in cheese and butter by HPLC using an immunoaffinity column

A rapid, sensitive convenient method for determination of aflatoxin M? (AFM?) in cheese and butter by HPLC was developed and validated. The method employs a safe extraction solution (mixture of acetonitrile, methanol and water) and an immunoaffinity column (IAC) for clean-up. Compared with the widely used method employing chloroform and a Florisil column, the IAC method has a short analytical time and there are no interference peaks. The limits of quantification (LOQ) of the IAC method were 0.12 and 0.14 μg/kg, while those of the Florisil column method were 0.47 and 0.23 μg/kg in cheese and buffer, respectively. The recovery and relative standard deviation (RSD) for cheese (spiked at 0.5 μg/kg) in the IAC method were 92% and 7%, respectively, while for the Florisil column method the corresponding values were 76% and 10%. The recovery and RSD for butter (spiked at 0.5 μg/kg) in the IAC method were 97% and 9%, and those in the Florisil method were 74% and 9%, respectively. In the IAC method, the values of in-house precision (n=2, day=5) of cheese and butter (spiked at 0.5 μg/kg) were 9% and 13%, respectively. The IAC method is superior to the Florisil column method in terms of safety, ease of handling, sensitivity and reliability. A survey of AFM? contamination in imported cheese and butter in Japan was conducted by the IAC method. AFM? was not detected in 60 samples of cheese and 30 samples of butter.     

Detection of aflatoxin M1 in milk and dairy products consumed in Adana, Turkey

A total of 70 dairy products consisting of 20 sterilized milk, 10 butter, 20 white cheese and 20 Kashar cheese samples were analysed for aflatoxin M₁ (AFM₁) by enzyme-linked immunosorbent assay (ELISA). The detection limit was 5 ng/L for milk and 25 ng/kg for butter, white cheese and Kashar cheese. Of the 70 dairy products analysed, AFM₁ in 49 samples (70%) was found to range from 10 to 388 ng/kg. Moreover, AFM₁ levels in three samples of milk, two samples of butter, one sample of white cheese and one sample of Kashar cheese were found to be higher than the Turkish legal limits.     

Conjugated linoleic acid (CLA) concentration,fatty acid composition and cholesterol content of some Turkish dairy products

Conjugated linoleic acid (CLA) concentrations, fatty acid composition and cholesterol content of some Turkish dairy products (butter, processed cheese, Kaymak and cream) were determined by capillary gas chromatography. The CLA and cholesterol content of some Turkish dairy products ranged from 1.50–5.60 mg/g fat and 148.30–369.04 mg/g fat, respectively. The most abundant saturated fatty acids in the dairy products investigated were palmitic acid (C16:0), stearic acid (C18:0) and myristic acid (C14:0). In all dairy products, C18:1 cis-9, 12 unsaturated fatty acid content (23.12–32.78 g/100 g) was considerably higher than others. In all samples studied, there was no correlation between CLA content of products and the linoleic acid content, or any other unsaturated fatty acid. A positive correlation between cholesterol and fat content of dairy products was observed.     

Determination of bisphenol A in milk and dairy products by high-performance liquid chromatography with fluorescence detection

This study was conducted to develop a selective and sensitive method for the determination of bisphenol A (BPA) levels in milk and dairy products. A method based on solvent extraction with acetonitrile and solid-phase extraction (SPE) was developed for the analysis of BPA in milk, yogurt, cream, butter, pudding, condensed milk, and flavored milk, and a method using two SPE cartridges (OASIS HLB and Florisil cartridge) for skim milk was also developed. The developed methods showed good recovery levels (77 to 102%) together with low detection limits (1 microg/liter for milk, yogurt, pudding, condensed milk, flavored milk, and skim milk and 3 microg/liter for cream and butter). These methods are simple, sensitive, and suitable for the analysis of BPA in milk and dairy products. When 40 milk and dairy products were analyzed by the proposed methods, BPA was not identified in noncanned products, but its levels ranged from 21 to 43 microg/kg in canned products, levels that were 60- to 140-fold lower than the migration limits in the European Union and Japan.     

The occurrence and growth of yeasts in dairy products

Yeasts were isolated, identified and enumerated from 161 samples of retail dairy products. Highest yeast populations (up to 10⁶–10⁷ cells/g) were found in yogurt and cheese samples while lower counts occurred in samples of pasteurized milk, cream, butter and ice cream. Candida famata, Kluyveromyces marxianus, Candida diffluens and Rhodotorula glutinis were the most frequency isolated species. The growth of these and other species was demonstrated during the refrigerated storage of cream, butter and cheese samples and by their inoculation and incubation in milk and yogurt samples. The predominance and growth species was probably related to their production of protein and fat hydrolysing enzymes and the ability to grow at 5°C.     

Assessing economic and demographic factors that influence United States dairy demand

Low-fat dairy products are key components of a healthy diet for all Americans. As the USDA increases its focus on nutrition and healthy eating, it is important to understand the underlying demands for dairy products, both the healthy and the less healthy ones. The consumption of fluid milk products has decreased over the last decade, whereas milk used for manufactured dairy products such as cheese, ice cream, yogurt, and butter, and for use as an ingredient in other food products, has risen. The objective of this study is to determine the effects of changes in demographic variables, retail prices, and total dairy expenditure on at-home consumption of dairy products, using purchase data from Nielsen 2007 Homescan (ACNielsen, New York, NY) data. To derive the demand elasticities for 16 products, a censored Almost Ideal Demand System model is used. Results reveal that demographic variables do have effects on the purchase of the 16 products, and own-price elasticities are 1 or greater for all 16 products for both uncompensated and compensated elasticities except 4: ice cream, refrigerated yogurt, processed cheese, and margarine. A substitution relationship exists among all fluid milk categories, natural and processed cheese, low-fat ice cream, and refrigerated yogurt, butter, and margarine.     

Determination of melamine in milk and dairy products by high performance liquid chromatography

A simple, precise, accurate, and validated reverse-phase HPLC method was developed for the determination of melamine in milk (pasteurized and UHT milk) and dairy products (powdered infant formula, fruit yogurt, soft cheese, and milk powder). Following extraction with acetonitrile:water (50:50, vol/vol), samples were purified by filter (0.45 μm), separated on a Nucleosil C8 column (4.6 mm × 250 mm, 3 μm) with acetonitrile:10 mmol/L sodium L-octane sulfonate (pH 3.1; 15:85, vol/vol) as mobile phase at a flow rate of 1 mL/min, and determined by a photodiode array detector. A linear calibration curve was obtained in the concentration range from 0.05 to 5 mg/kg. Milk and dairy products were fortified with melamine at 4 levels producing average recovery yields of 95 to 109%. The limits of detection and quantification of melamine were 35 to 110 and 105 to 340 μg/kg, respectively. The method was then used to analyze 300 samples of milk and dairy products purchased from major retailers in Turkey. Melamine was not found in infant formulas and pasteurized UHT milk, whereas 2% of cheese, 8% of milk powder, and 44% of yogurt samples contained melamine at the 121, 694±146, and 294±98 μg/kg levels, respectively. These findings were below the limits set by the Codex Alimentarius Commission and European Union legislation. This is the first study to confirm the existence of melamine in milk and dairy products in Turkey. Consumption of foods containing these low levels of melamine does not constitute a health risk for consumers.     

Heavy metals and trace elements levels in milk and milk products

Milk and dairy products are an important food in the human diet. The present investigation was carried out to determine concentrations of lead, cadmium, zinc, copper and iron in milk and dairy products and evaluate the potential health risks of metals to humans via consumption of milk and dairy products. A total of 77 samples of milk and dairy products (22 raw milk, 20 kareish cheese, 21 butter and 14 rice pudding) were collected from farms, individual farmers and dairy shops in Beni-Suef governorate, Egypt. Pb, Cd, Zn, Cu and Fe concentrations in milk and dairy products ranged from 0.044–0.751, 0.008–0.179, 0.888–18.316, 0.002–1.692 and 1.3208–45.6198 ppm respectively. Pb concentration in all samples exceeded the maximum permissible limit (0.02 mg/kg) established by codex standard. Pd and Cd intake through milk and dairy products consumption were 1.27 and 0.33 μg/kg bw/day, which represent 35.3 and 39.8 % of the tolerable daily intake. Dairy products are poor sources of iron, copper and zinc, and milk contributes little to the total iron and zinc intake. Target hazard quotient values of less than 1 indicate a relative absence of health risks associated with the consumption of milk and dairy products.     

A review of the microbiological hazards of dairy products made from raw milk

This review concentrates on information concerning microbiological hazards possibly present in raw milk dairy products, in particular cheese, butter, cream and buttermilk. The main microbiological hazards of raw milk cheeses (especially soft and fresh cheeses) are linked to Listeria monocytogenes, verocytotoxin-producing Escherichia coli (VTEC), Staphylococcus aureus, Salmonella and Campylobacter. L. monocytogenes, VTEC and S. aureus have been identified as microbiological hazards in raw milk butter and cream albeit to a lesser extent because of a reduced growth potential compared with cheese. In endemic areas, raw milk dairy products may also be contaminated with Brucella spp., Mycobacterium bovis and the tick-borne encephalitis virus (TBEV). Potential risks due to Coxiella burnetii and Mycobacterium avium subsp. paratuberculosis (MAP) are discussed. Pasteurisation ensures inactivation of vegetative pathogenic microorganisms, which increases the safety of products made thereof compared with dairy products made from raw milk. Several control measures from farm to fork are discussed.     

Consumer acceptance of dairy products with a saturated fatty acid–reduced,monounsaturated fatty acid–enriched content

Agriculture-based reformulation initiatives, including oleic acid–rich lipid supplementation of the dairy cow diet, provide a novel means for reducing intake of saturated fatty acids (SFA) at a population level. In a blinded manner, this study evaluated the consumer acceptance of SFA-reduced, monounsaturated fatty acid–enriched (modified) milk, Cheddar cheese, and butter when compared with control and commercially available comparative samples. The effect of providing nutritional information about the modified cheese was also evaluated. Consumers (n = 115) rated samples for overall liking (appearance, flavor, and texture) using 9-point hedonic scales. Although no significant differences were found between the milk samples, the modified cheese was liked significantly less than a regular-fat commercial alternative for overall liking and liking of specific modalities and had a lower liking of texture score compared with the control cheese. The provision of health information significantly increased the overall liking of the modified cheese compared with tasting the same sample in a blinded manner. Significant differences were evident between the butter samples for overall liking and modalities of liking; all of the samples were significantly more liked than the commercial butter and sunflower oil spread. In conclusion, this study illustrated that consumer acceptance of SFA-reduced, monounsaturated fatty acid–enriched dairy products was dependent on product type. Future research should consider how optimization of the textural properties of fatty acid–modified (and fat-reduced) cheese might enhance consumer acceptance of this product.     

Method to assess the carbon footprint at product level in the dairy industry

A model to calculate the farm-to-customer carbon footprint (CF) for different dairy product groups is presented. As the largest share of the CF of dairy products occurs at farm level, it is decisive how the emissions from raw milk production are allocated between different products. Impacts associated with raw milk are allocated based on a weighted fat and protein content (1:1.4). Data from the dairy company Arla Foods give 1.1, 8.1, 6.5, 7.4 and 1.2 kg carbon dioxide equivalents per kg of fresh dairy product, butter and butter blend, cheese, milk powder and whey based product, and other, respectively. One critical aspect is how the by-product ‘whey’ is dealt with. No emissions are allocated to the milk solid whey, which is why products containing whey have an apparent low impact. Underlying methodological assumptions are open to debate and further research is needed concerning the CF impact of different milk components.     

Recovery of n-3 polyunsaturated fatty acids and conjugated linoleic acids in ripened cheese obtained from milk of cows fed different levels of extruded flaxseed

The aim of the study was to investigate whether the addition of extruded flaxseed (EF) in dairy cow diets had an effect on milk fat and individual fatty acids (FA) recovery in cheese after 90 d of ripening. Eighteen Holstein-Friesian cows, divided into 3 experimental groups (6 cows/group), were fed 3 isonitrogenous and isoenergetic diets with 0 (CTR), 500 (EF500), or 1,000 g/d (EF1000) of EF in 3 subsequent periods (2 wk/each), following a 3 × 3 Latin square design. Dry matter intake (DMI) and milk yield were recorded daily. Individual milk samples were collected on d 7 and 13 of each period to determine proximate and FA composition. Eighteen cheese-making sessions (2 for each group and period) were carried out, using a representative pooled milk sample obtained from the 6 cows of each group (10 L). At 90 d of ripening, cheeses were analyzed for proximate and FA composition. Cheese yield was computed as the ratio between the weights of ripened cheese and processed milk. Recoveries of fat, individual FA, and grouped FA were computed as the ratio between the corresponding weights in cheese and in milk. Inclusion of EF did not affect DMI, milk yield, or milk composition. Compared with CTR, the 2 diets containing EF increased the proportion of C18:3n-3 and total n-3 FA, in both milk and cheese. Cheese yield and cheese fat percentage did not differ among diets. Likewise, milk fat recovery in cheese was comparable in the 3 treatments and averaged 0.85. The recoveries of individual FA were, for the most part, not dissimilar from fat recovery, except for short-chain saturated FA (from 0.38 for C4:0 to 0.80 for C13:0), some long-chain saturated FA (0.56 and 0.62 for C20:0 and C21:0, respectively), and for C18:3n-6 (1.65). The recovery of saturated FA was lower than that of monounsaturated FA, whereas recovery of polyunsaturated FA was intermediate. Compared with medium- and long-chain FA, short-chain FA were recovered to a smaller extent in cheese. No differences in recovery were found between n-6 and n-3 FA. In conclusion, FA have different recoveries during cheese-making, with lower values for the short-chain compared with long-chain FA, and for saturated FA compared with unsaturated FA. The addition of EF in dairy cow diets did not influence cheese yield or fat recovery in cheese, irrespective of the inclusion level. The experiment confirmed that feeding cows with EF represents a successful strategy for improving the FA profile of dairy products, through an increase of n-3 FA.     

Hot topic: Fatty acid and conjugated linoleic acid (CLA) isomer composition of commercial CLA-fortified dairy products: evaluation after processing and storage

Conjugated linoleic acid (CLA) exerts a strong positive influence on human health but intake of these fatty acids is typically too low, and increased consumption of CLA is recommended. A good way to raise the CLA content in the diet without a radical change in eating habits seems to be the enrichment of commonly consumed food products with CLA supplements. This study analyzed the total fatty acid content and the CLA isomer composition of 6 commercially available CLA-fortified dairy products during processing and 10 wk of refrigerated storage. Research was carried out by combining gas chromatography and silver-ion HPLC. The tested samples were a CLA oil supplement, and several skim milk dairy products fortified with the supplement (milk, milk powder, fermented milk, yogurt, fresh cheese, and milk-juice blend). The CLA oil supplement was added such that the consumer received 2.4 g/d of CLA by consuming 2 servings. The predominant isomers present, C18:2 cis-9, trans-11 CLA and C18:2 cis-10, trans-12 CLA, were in at a similar ratio, which ranged from 0.97 to 1.05. These major isomers were not significantly affected by processing but a decrease in total CLA in fresh cheese samples was detected after 10 wk of refrigerated storage. Refrigerated storage and thermal treatment resulted in significant decreases or disappearance of some of the minor CLA isomers and a significant increase of trans, trans isomers from both cis, trans, trans, cis, and cis, cis isomers especially in CLA-fortified milk powder but also in fermented milk, yogurt, and milk-juice blend.     

EFFECTS of STERILIZING DOSES of GAMMA IRRADIATION ON LEVELS of VITAMIN A, AMINO ACIDS, and FATTY ACIDS IN SELECTED DAIRY PRODUCTS

Frozen dairy products intended for low microbial diets of immunosuppressed patients were sterilized by exposure to 40 kGy (4 Mrad) of cobalt-60 irradiation. Levels of vitamin A, amino acids, and selected fatty acids were measured in yogurt bars, ice cream, Cheddar cheese, mozzarella cheese, and nonfat dry milk before and after irradiation. Addition of antioxidants to the frozen dairy desserts prior to irradiation at - 78C was not effective in preventing degradation of vitamin A. There were significant decreases of approximately 90% in levels of vitamin A in Cheddar cheese and mozzarella cheese irradiated at -78C and 0–5C compared to the corresponding nonirradiated products. Levels of vitamin A in nonfat dry milk irradiated at three different temperatures (22C, 0–5C, or - 78C) were variable compared to levels in the nonirradiated product. Levels of palmitic, stearic, oleic, linoleic, and linolenic acids were retained in all irradiated dairy products analyzed. Irradiation at the specified temperatures did not affect levels of individual amino acids in nonfat dry milk or mozzarella cheese.     

Determination of total solids in dairy products using the microwave-oven method

Microwave-oven and air-oven methods were compared in the determination of total solids in various dairy products (plain yogurt, flavoured yogurt, soft cheese, aged cheese and butter). the microwave-oven method considerably reduced drying time. For the cheeses and butter the drying times were 10 and 20 min respectively. Precision levels were not satisfactory in the case of yogurts.     

Production of conjugated linoleic acid enriched milk and dairy products from cows receiving grass silage supplemented with a cereal-based concentrate containing rapeseed oil

Opportunities for the production of milk and dairy products enriched with cis-9, trans-11 conjugated linoleic acid (CLA) were investigated. Eighteen mid-lactation cows were used in a continuous-design for 7 weeks. During the first week, cows received grass silage ad libitum supplemented with 10 kg per day of a cereal-based concentrate (control) that was replaced with a concentrate containing 50 g kg⁻¹ of rapeseed oil (RO). Changes in milk fatty acid composition were monitored on a weekly basis and milk produced was used to manufacture Edam cheese and butter. Inclusion of RO in the concentrate supplement increased the mean levels of trans-octadecanoic, monounsaturated, CLA and polyunsaturated fatty acid in the milk fat from 1.6, 25.7, 0.46 and 2.8 to 4.3, 35.3, 1.02 and 3.9 g 100 g⁻¹ total fatty acids, respectively. In contrast, the mean level of saturated fatty acids decreased from 71.4 to 60.7 g  100 g⁻¹ total fatty acids. Changes in milk fatty acid composition due to RO occurred within 7 days, with responses reaching a plateau after 21 days. Furthermore, the CLA concentrations in the milk fat from individual cows ranged between 0.37 and 0.65 and 0.43 and 2.06 g 100 g⁻¹ total fatty acids for the control and RO diet, respectively. CLA enriched milk was used successfully to manufacture of Edam cheese and butter with softer textures but with acceptable organoleptic and storage properties. Processing milk into butter or cheese had no effect on the CLA concentrations indicating that enrichment of dairy products is dependent on the content in raw milk fat.