Acids In Dairy Products Research Articles

Effect of dietary cold-pressed hempseed cake on the fatty acid profile of semi-hard cheese made from goat milk

Recently, many feedstuffs have been introduced to animal diets to increase the content of beneficial fatty acids in dairy products. Therefore, this study aimed to research the effect of including hempseed cake in dairy goats concentrate mixtures on the chemical composition and fatty acid profile of semi-hard goat cheese that is traditionally produced on family farm. The feeding of goats was based on meadow hay ad libitum and 1200 g/day/head of concentrate mixture. In the first experimental group, 60 g/kg DM of hempseed cake (HSC-60) was administered; meanwhile, in the second experimental group, 120 g/kg DM of hempseed cake (HSC-120) was included in the diet. The chemical composition of cheese was mostly unaffected by enriching the goats’ nutrition with hempseed cakes. Dietary HSC-120 increased C18:1 n-9 and C18:3 n-6 compared to the control, and increased C22:6 n-3 in cheese compared to HSC- 60, although both HSC-120 and HSC-60 lowered n-6/n-3 ratios in cheese. Feeding goats with HSC-120 may have contributed to the development of the functional properties of semi-hard goat cheese made on family farm, as compared to the cheese produced by goats fed with commercial concentrate mixtures.

Application of cationic dye pyronin G (Y) for quantitative photometric and fluorimetric determination of higher carboxylic acids in dairy products using extraction

In this work we propose to use a heptane-ethanol extract of the ionic associate of higher carboxylic acids with a cationic dye – pyronin G (Y) for quantitative extraction-photometric and extraction-fluorimetric determination of carboxylic acids in dairy products. The resulting ion associate is characterized by a maximum of optical density at 510 nm and intense of fluorescence with a maximum at 566 nm. The maximum optical density and fluorescence intensity of the ion associate is observed during its extraction with octanol/heptane from aqueous solutions with pH = 11.25. The quantum yield of ionic associates of higher carboxylic acids with pyronine G (Y) relative to the standard solution of fluorescein was calculated. A technique has been developed for the extraction-fluorimetric determination of hydrophobic acids in milk and cheese. The method has been tested in the determination of carboxylic acids content in milk and cheese samples. The content of higher carboxylic acids, determined by the method with pyronin G, in milk was (6.6 ± 0.15) · 10–4 M, in cheese – (1.1 ± 0.10) · 10–3 mol/kg. The obtained results of extraction-photometric and extraction-fluorimetric determination of carboxylic acids in dairy products make it possible to recommend the developed method in the practice of institutions of the corresponding profile.

Nanomolar detection of essential amino acid in dairy products using a novel electrochemical sensor based on zinc cobaltite nanoflowers embedded porous 3D reduced graphene oxide

L-tryptophan (L-Trp) is a vital amino acid that sways neuronal function, immunity, and gut homeostasis, and its accurate detection in food samples is crucial. The aim of this study is to integrate zinc cobaltite (ZCO) nanoparticles and 3D porous reduced graphene oxide (rGO) on a screen-printed carbon electrode (SPCE) surface for building a novel electrochemical sensor to sensitively detect L-Trp in food products. A low-temperature aqueous solution method was employed in ZCO nanoflower synthesis and a hydrothermal approach was utilized to prepare 3D rGO. SEM, elemental mapping, XRD, Raman spectroscopy, XPS, and EIS characterizations were performed on the prepared nanocomposite, ZCO/3DrGO. Electrochemical experiments conducted with the cyclic and differential pulse voltammetric techniques were used for effectively assessing the catalytic power of ZCO/3DrGO/SPCE. With a low detection limit of 3 nM, high sensitivity of 19.53 μAμM−1cm−2, and a broad linear range of 0.08–5.93; 5.93–87.18 μM, the sensor demonstrated promising electrocatalytic activity towards L-Trp. Further, the reliability of the sensor was proved by analyzing its stability, repeatability, reproducibility, and selectivity towards L-Trp. The successful detection of L-Trp in dairy products (yogurt, milk, and cottage cheese) using the proposed sensor evinced its practical feasibility with high recovery of 98.16%–101.16% and low RSD of 2.8%.

Effect of reverse osmosis pre-processing of acid whey and electrodialysis current density on process performance

Acid whey (AW) is the main side-stream from acidified dairy products, known for its high contents of lactic acid and minerals. The present work investigates the effect of reverse osmosis (RO) pre-processing of AW (ROAW) and the current density during electrodialysis (ED) on the ED process performance. Firstly, the limiting current density of the ED system when treating AW and ROAW was determined. Then, the AW and ROAW have been demineralized and deacidified at under-limiting or over-limiting current density batch operating conditions. RO pre-processing of AW and current density strongly affect the demineralization rate and solutes mass transport across the membranes. Lactate transport can be rationalized by the weak acid dissociation mechanism, while water splitting played a minor role in the ED process performance. Among cations, calcium and magnesium were most affected by RO pre-processing, due to their high affinity to the cation exchange membranes. Lactose and galactose were found in small amounts in the concentrate solution, while no glucose was detected for most conditions even though the glucose content decreased in the diluates. The energy consumption was up to 2 fold higher for ROAW compared to AW

Fouling of ion-exchange membranes during electrodialytic acid whey processing analysed by 2D fluorescence and FTIR spectroscopy

Acid whey (AW), a by-product from the production of acidified dairy products, contains high amounts of lactic acid and minerals that can be recovered by electrodialysis (ED). To better understand the process and improve its efficiency, the objective of this study was to investigate fouling of ion-exchange membranes (IEMs) during ED of AW and concentrated AW by reverse osmosis (ROAW), underlimiting (ULCD), limiting (LCD) and overlimiting current density operating conditions (OLCD). The structure, hydrophobicity, and chemical composition of membranes showed differences regarding fouling on anion- (AEM) and cation- (CEM) exchange membranes facing the diluate and the concentrate, both for AW and ROAW. Furthermore, operating at OLCD tends to reduce fouling compared to ULCD, due to the expected generation of electroconvective vortices. 2D fluorescence spectroscopy and Fourier-transform infrared spectroscopy (FTIR) provided complementary and more detailed information regarding the fouling and efficiency of the cleaning procedure. The 2D fluorescence spectra showed that the AEM surfaces in contact with the diluate change more than those in contact with the concentrate. The FTIR analyses showed the presence of lactose and lactic acid on the AEM surfaces in contact with the concentrate, which could not be detected by fluorescence.

The effect of feed formulation on surface composition of powders and wall deposition during spray drying of acidified dairy products

The effect of feed formulation on surface composition of powders and wall deposition during spray drying of acidified dairy products

Improved Tribological Characterization of Acidified Milk Products by Means of a New Rubber Material

Acidified dairy products such as yogurt or quark have been popular for a long time because of their typical creaminess. However, determining creaminess is difficult. Various approaches to measuring creaminess have already been developed, often taking the coefficient of friction into account. Therefore, the aim of this work was to establish a commercially available rubber surface for a tribological method to improve the differentiation of samples with different contents of fat and protein. This improved differentiation should in turn help to gain more information about the creaminess of acidified milk products.Rubber surfaces including natural rubber, styrene-butadiene and nitrile-butadiene as single compounds as well as mixtures of two rubbers (natural rubber/styrene-butadiene and nitrile-butadiene/styrene-butadiene) were screened. An acidified milk matrix with 0% and 3.5% fat was chosen as sample set for the screening. Using the rubber P9540 (mixture of styrene-butadiene and nitrile-butdadiene), the differentiation was improved for 34–58% compared to the widely used SBR 70 (depending on the chosen sliding speed). Afterwards, the application of the rubber was tested using a sample set of acidified milk matrices with fat contents ranging from 0 to 10% and a sample set of commercial products with protein contents from 4 to 11%. The new rubber mixture is suited for differentiating fermented milk matrices with a fat content of 0% and 3.5% and above. Additionally, commercial samples like Skyr with a protein content of 11% can be distinguished from samples with a lower protein content.

SERS Detection of Benzoic Acid in Milk by Using Ag-COF SERS Substrate

Benzoic acid, which has a pivotal role in food additive, is prohibited to add as a preservative in dairy products. China, Brazil, and other countries have proposed standard methods to detect the addition of benzoic acid in food. Surface-enhanced Raman scattering (SERS) is an upcoming spectral detection technique, which has been widely used in the field of material analysis with the advantages of non-invasive, fast detection speed and complex environment with little interference. To detect the illegal use of benzoic acid in dairy industry, we developed Ag-COF (covalent-organic framework) material as SERS substrate to detect benzoic acid in liquid milk. The great enhancement ability of Ag-COF substrate is controlled by the addition of acetic acid and complex interplay between COF material and benzoic acid. This detection method has high sensitivity and reliability that allows us to achieve limit of detection (LOD) of 0.13 μg/mL in milk and 0.00372 μg/mL in water by applying this method. In experiment on recovery rate of real samples, the detection time is less than 15 minutes and the relative standard deviation (RSD) ranged from 2.82% to 5.69%. Therefore, this method has practical significance of the detection of benzoic acid in dairy products.

A novel immobilization fluorescence capillary analysis method and its applications.

Fluorescence capillary analysis (FCA) realizes trace-level analysis of micro-volume samples; it is easy to operate, extremely low in analytical cost and can significantly lessen environmental pollution from analytical chemistry waste. FCA has the characteristics of green analytical chemistry and has been applied in clinical, biochemical, pharmaceutical, food safety and other fields. FCA basically involves a micro-volume glass capillary, a capillary holder and an ordinary fluorescence detector. The capillary is not only a container for chemical reaction and detection but also functions as a carrier to immobilize enzymes, gene probes or reagents; it can be used repeatedly or can be disposable. In analysis, the capillary which is modified with functional reagents sucks in a measured liquid for the reaction and is then inserted into the holder within the fluorescent detector for measurement. The immobilized FCA method has been successfully used in the determination of reduced coenzyme I, ethanol in liqueur, lactic acid in dairy products, pyruvic acid and glucose in serum, trace-level sulfated bile acid in urine, the ratio of pyruvic/lactic acid in serum, and pyruvic acid in cells as well as in DNA end-labeling and dyeing methods. Further, FCA can also be extended to capillary arrays to complete multipurpose simultaneous determinations and can be combined with mobile phones as fluorescence detectors for use in mobile health analytical technology. FCA will produce considerable social benefits in medicine, pharmacy, fermentation of food, environmental protection and other fields. Therefore, the relevant contents are presented in this tutorial review.

Жирнокислотный состав козьего и овечьего молока и его трансформация в процессе производства йогурта

Introduction. Information on the structure of fatty acids is crucial for production and promotion of goat and sheep milk in dairy industry. The profile of fatty acids of milk fat can affect the nutrition value and market value of dairy products.
 Study objects and methods. The present research featured fatty acid structure of goat and sheep milk and its transformation during yogurt production. The fatty acid structure was studied using gas chromatography. The milk was obtained from goats of the Zaanensky breed and sheep of the North Caucasian breed. Their ratio in the yogurt was 1:1. 
 Results and discussion. The content of saturated fatty acids was 12% less in goat milk than in sheep milk. Olein, stearin, and palmitic acids are the main fatty acids in the fatty phase of milk and yogurt. The research revealed some changes in concentration of individual fatty acids during milk processing and during the storage of yogurt. As a result of ripening and storage, the amount of saturated fatty acids in yogurt increased by 5% on day 7, in comparison with the initial dairy mix. The content of the polynonsaturated fatty acids decreased by 19.27%. Goat milk had the highest value of the ratio of the hypocholesteremic and hypercholesteremic fatty acids. Goat milk demonstrated the most acceptable fatty acid structure in terms of healthy nutrition and prevention of atherosclerosis and thrombogenesis. During yogurt production and storage, the monononsaturated and polynonsaturated fatty acids decreased, while the content of saturated fatty acids increased. Thus, goat milk can increase the amount of monononsaturated and polynonsaturated fatty
 acids in dairy products. However, the research also revealed a general tendency to decrease in monononsaturated and polynonsaturated fatty acids during yogurt production and storage, with a parallel increase in the content of saturated fatty acids. Unlike ship milk, goat milk had a lower value of the indices of atherogenicity and thrombogenesis.
 Conclusion. The indices of atherogenicity and thrombogenesis provided additional information on the functional properties of the product. The established features of the fatty acid profile and its transformation during yogurt production provide data that can help produce qualitatively new dairy drinks with a healthy fatty acid profile.

Size classification of precipitated calcium phosphate using hydrocyclone technology for the recovery of minerals from deproteinised acid whey

Acid whey is generated during the manufacture of acidified dairy products, such as soft cheeses, acid casein ingredients and strained yoghurts. Examples of these whey‐based by‐products include Cottage cheese acid whey and Greek yoghurt acid whey. Alkalisation of acid whey at elevated temperatures (60 °C) precipitates calcium phosphate, which can be recovered and used as an ingredient. The novel application of a liquid–solid hydrocyclone in the size classification of calcium phosphate from heated and neutralised acid whey was investigated in this study. Factors influencing hydrocyclone performance were tested, and the technology was integrated into a membrane filtration‐based process for the production of milk mineral powders.

Determination of Major Sialic Acids in Dairy Products by Electrophoretic Stacking Technology with Contactless Conductivity Detection

Synergistic stacking technique by combining field-amplified sample injection with moving chemical reaction boundary was developed for the sensitive determination of two major sialic acids, N-acetylneuraminic acid (NANA) and N-glycolylneuraminic acid (NGNA) based on capillary electrophoresis with capacitively coupled contactless conductivity detection. A series of experimental parameters affecting electrophoretic separation, detection sensitivity, and hydrolysis efficiency of sialic acids were investigated. Under the optimum conditions, NANA and NGNA could be well separated from the common monosaccharides and disaccharides as well as other potential coexisting inorganic and organic anions in a running buffer of 30 mmol L−1 NaOH–10 mmol L−1 Na2HPO4/0.8 mmol L−1 CTAB. This developed method has been applied to determine the target analytes in dairy products. In terms of its high sensitivity (LODs 1.7–2.2 ng mL−1, namely, 5.5–7.2 nmol L−1), good linearity (r > 0.999), acceptable recovery (93–107%), and reliability of acid hydrolysis step, this proposed method provides a simple, rapid, sensitive, and environmentally friendly alternative for the analyses of the main sialic acids in dairy products without derivatization.

An overview on D-amino acids.

More than half a century ago researchers thought that D-amino acids had a minor function compared to L-enantiomers in biological processes. Many evidences have shown that D-amino acids are present in high concentration in microorganisms, plants, mammals and humans and fulfil specific biological functions. In the brain of mammals, D-serine (D-Ser) acts as a co-agonist of the N-methyl-D-aspartate (NMDA)-type glutamate receptors, responsible for learning, memory and behaviour. D-Ser metabolism is relevant for disorders associated with an altered function of the NMDA receptor, such as schizophrenia, ischemia, epilepsy and neurodegenerative disorders. On the other hand, D-aspartate (D-Asp) is one of the major regulators of adult neurogenesis and plays an important role in the development of endocrine function. D-Asp is present in the neuroendocrine and endocrine tissues and testes, and regulates the synthesis and secretion of hormones and spermatogenesis. Also food proteins contain D-amino acids that are naturally originated or processing-induced under conditions such as high temperatures, acid and alkali treatments and fermentation processes. The presence of D-amino acids in dairy products denotes thermal and alkaline treatments and microbial contamination. Two enzymes are involved in the metabolism of D-amino acids: amino acid racemase in the synthesis and D-amino acid oxidase in the degradation.

Phytanic acid in dairy products and risk of cancer: current evidence and future directions

Previous epidemiological studies of dairy and cancer risk reported inconsistent associations. Differences in abundance of bioactive components, such as metabolites from rumen microbiome, may explain the inconsistent associations. Among such rumen‐microbiome‐derived metabolites, this report focuses on phytanic acid, which is a 20‐carbon, methylated, branched‐chain fatty acid and a metabolite of plant‐based chlorophyll, and summarizes current evidence on its association with cancer risk through literature review and meta‐analysis. Phytanic acid has multiple functional properties linked to carcinogenesis from in vitro studies through peroxisomal function; mitochondrial function and oxidative stress; and cell signal transduction. Phytanic acid is converted in the peroxisomes to pristanic acid by multiple enzymes, including α‐methylacyl‐CoA racemase (AMACR). AMACR is overexpressed in tissues of various cancer sites, including prostate, colon, rectum, ovaries, breast, bladder, lung, and liver and in lymphoma tissues. In prostate cancer, AMACR expression is strongly linked to presence of the disease and hypothesized as a diagnostic marker. In addition, phytanic and pristanic acids are retinoid X receptor and peroxisome proliferator‐activated receptor (PPAR) agonists and thereby can alter cell proliferation and apoptosis. The association between phytanic acid and cancer risk has been examined in several epidemiological studies. Three studies examined the association between phytanic acid intake from foods or concentration in blood and risk of overall prostate cancer. When pooled, their results are summarized as no association [pooled odds ratio (OR) =1.04; 95% confidence intervals (CI)=0.90–1.17, comparing the highest category with the lowest]. Another study reported higher concentrations in cases than in controls (P‐difference=0.04). For risk of advanced prostate cancer, one of the three studies observed a positive association (OR=1.4; 95% CI=1.0–1.9). For non‐Hodgkin's lymphoma risk, only one study examined the association with phytanic acid intake and reported a positive association (OR=1.5; 95% CI=1.0–2.1). None of the previous epidemiological studies examined factors that are potentially involved in the association between phytanic acid and cancer risk such as AMACR and PPARs, which we propose for future studies. In addition, we propose to extend to other fatty acids that are unique to dairy fats such as short‐ and medium‐chain fatty acids.Support or Funding InformationThis study was funded by the Oregon Health & Science University/Oregon State University Cancer Prevention and Control Initiative (PHR030‐PV07; Lead‐PI: Y Takata).

Influence of Amino Acids in Dairy Products on Glucose Homeostasis: The Clinical Evidence.

Dairy products have been hypothesized to protect against type 2 diabetes because of their high content of whey proteins, rich in branched-chain amino acids (BCAAs) - leucine, isoleucine and valine - and lysine, which may decrease postprandial glucose responses and stimulate insulin secretion. Paradoxically, epidemiologic studies also show that higher levels of plasma BCAAs have been linked to insulin resistance and type 2 diabetes. Therefore, the objective was to review the recent clinical evidence concerning the intake of amino acids found in dairy proteins so as to determine their impact on glucose homeostasis in healthy persons and in those with prediabetes and type 2 diabetes. Clinical studies have reported that the major dairy amino acids, namely, leucine, isoleucine, glutamine, phenylalanine, proline and lysine, have beneficial effects on glucose homeostasis. Yet the reported doses of amino acids investigated are too elevated to be reached through adequate dairy product intake. The minor dairy amino acids, arginine and glycine, may improve glucose homeostasis by improving other risk factors for type 2 diabetes. Further, the combination of amino acids may also improve glucose-related outcomes, suggesting additive or synergistic effects. Nevertheless, additional long-term studies in individuals with prediabetes and type 2 diabetes are needed to ascertain the benefits for glucose homeostasis of amino acids found in dairy foods.

Benzoic Acid Production with Respect to Starter Culture and Incubation Temperature during Yogurt Fermentation using Response Surface Methodology.

Benzoic acid is occasionally used as a raw material supplement in food products and is sometimes generated during the fermentation process. In this study, the production of naturally occurring yogurt preservatives was investigated for various starter cultures and incubation temperatures, and considered food regulations. Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus reuteri, Lactobacillus plantarum, Bifidobacterium longum, Bifidobacterium lactis, Bifidobacterium bifidum, Bifidobacterium infantis, and Bifidobacterium breve were used as yogurt starter cultures in commercial starters. Among these strains, L. rhamnosus and L. paracasei showed the highest production of benzoic acid. Therefore, the use of L. rhamnosus, L. paracasei, S. thermophilus, and different incubation temperatures were examined to optimize benzoic acid production. Response surface methodology (RSM) based on a central composite design was performed for various incubation temperatures (35-44℃) and starter culture inoculum ratios (0-0.04%) in a commercial range of dairy fermentation processes. The optimum conditions were 0.04% L. rhamnosus, 0.01% L. paracasei, 0.02% S. thermophilus, and 38.12℃, and the predicted and estimated concentrations of benzoic acid were 13.31 and 13.94 mg/kg, respectively. These conditions maximized naturally occurring benzoic acid production during the yogurt fermentation process, and the observed production levels satisfied regulatory guidelines for benzoic acid in dairy products.

Method for determination of fatty acids in bovine colostrum using GC-FID

Bovine colostrum is potentially valuable source of essential fatty acids (FAs), but so far only few studies have made the effort to estimate FA composition of this potential resource. The aim of current research was to fill this gap with selecting and validating an accurate procedure for the analysis of the composition of the FAs in bovine colostrum. We used colostrum samples of Holstein-Friesian cattle from Märja experimental farm as a test material. The validated method includes derivatization, in which FAs are sent through esterification with the acidic catalyst boron trifluoride. Formed methyl esters of fatty acids (FAMEs) were analysed using GC-FID. The obtained LOD and the LOQ of FAMEs were 0.11–0.68 and 0.37–2.27ppm, respectively. The analysis of fortified samples showed very good and similar recoveries, indicating that the method proposed here can be routinely used for determination and investigation of the fatty acids in dairy products.

Comparison and validation of 2 analytical methods for the determination of free fatty acids in dairy products by gas chromatography with flame ionization detection

Accurate quantification of free fatty acids (FFA) in dairy products is important for quality control, nutritional, antimicrobial, authenticity, legislative, and flavor purposes. In this study, the performance of 2 widely used gas chromatographic flame ionization detection methods for determination of FFA in dairy products differing in lipid content and degree of lipolysis were evaluated. We used a direct on-column approach where the isolated FFA extract was injected directly and a derivatization approach where the FFA were esterified in the injector to methyl esters using tetramethylammonium hydroxide as a catalyst. A comprehensive validation was undertaken to establish method linearity, limits of detection, limits of quantification, accuracy, and precision. Linear calibrations of 3 to 700mg/L (R2>0.999) and 20 to 700mg/L (R2>0.997), and limits of detection and limits of quantification of 0.7 and 3mg/L and 5 and 20mg/L were obtained for the direct injection on-column and the derivatization method, respectively. Intraday precision of 1.5 to 7.2% was obtained for both methods. The direct injection on-column method had the lower levels of limits of detection and quantification, because FFA are directly injected onto the GC as opposed to the split injection used in the derivatization method. However, the direct injection on-column method experienced accumulative column phase deterioration and irreversible FFA absorption because of the acidic nature of the injection extract, which adversely affected method robustness and the quantification of some longer chain FFA. The derivatization method experienced issues with quantification of butyric acid at low concentrations because of coelution with the injection solvent peak, loss of polyunsaturated FFA due to degradation by tetramethylammonium hydroxide, and the periodic emergence of by-product peaks of the tetramethylammonium hydroxide reaction that interfered with the quantification of some short-chain FFA. The derivatization method is more robust, and because the derivatization step can be automated, it is more suitable for routine analysis of FFA in dairy products. However, considerable scope exists to develop an alternative gas chromatography with flame ionization detection method to quantify FFA in dairy products without any limitations that is robust and accurate.

Acid gelation of whey protein microbeads of different sizes

In acidified dairy products, the size of the whey protein particles could play a key role in the final structure of the gel. In the present study, small (SM; 2.5 ± 1.2 μm), medium (MM; 4.2 ± 2.2 μm), and large (LM; 18.4 ± 7.2 μm) whey protein microbeads were produced by mixing a 150 g.kg−1 whey protein isolate (WPI) solution and n-dodecane in the presence of polyglycerolpolyricinoleate (PGPR) surfactant at different shear rates and were then stabilized through heat gelation. The microbeads were then washed by centrifugation, dispersed at 70 or 90 g.kg−1 in milk ultrafiltrate, and acidification was performed at 35 °C by adding glucono-δ-lactone to achieve the final pH of ~4.5 in 6 h. Acid gelation was monitored using small deformation rheology, while the gel microstructure was investigated microscopically. The results showed that smaller size of microbeads promoted gels with a higher stiffness and a smaller pore size distribution. The effects were particularly significant at SM microbeads as the number of particles in this system was higher than in LM or MM, hence more connectivity between particles.

Effect of Safflower Oil on Concentration of Conjugated Linoleic Acid of Kefir Prepared by Low-fat Milk.

Conjugated linoleic acid (CLA) is a special fatty acid in dairy products with unique antioxidant and anti-cancerous effects. Kefir, a milk product, comprises normalized homogenized cow's milk, the fructose and lactulose syrup as well as a symbiotic starter which has improved probiotic characteristics. The study was aimed to discuss patents and to examine the effect of different safflower oil concentrations on CLA content of the kefir drink prepared by low-fat milk. Safflower oil was added at 0.1, 0.3 and 0.5% (V/V) to low-fat cow's milk and six formulations of kefir samples were prepared. The CLA content of the kefir products was measured at pH=6.0 and pH=6.8 by gas chromatography. Acid and bile tolerance of bacterial microenvironment in the products were also determined. Substitution of natural fat content of milk with safflower oil resulted in proportional increase in the CLA contents of kefir in a dose dependent manner. The highest concentration of CLA was found under 0.5% (V/V) of safflower oil at pH 6.0 and temperature of 37 °C. Adding the Safflower oil into milk used for kefir production, increased CLA content from 0.123 (g/100 g) in pure safflower free samples to 0.322 (g/100 g) in samples with 0.5% (V/V) of safflower oil. The current study revealed that substitution of safflower oil with natural fat of cow's milk may help the production of kefir samples with remarkable increase in CLA content of final product.