The effect of intense pulsed light on the sensory properties of nonfat dry milk.

Our objectives were to examine (1) how intense pulsed light (IPL) processing parameters (exposure time and initial temperature) affected aroma, flavor, and mouthfeel of nonfat dry milk, (2) which levels of each parameter produced aroma, flavor, and mouthfeel changes from an untreated control sample, and (3) whether minimal or intense processing conditions produced a noticeable appearance change from the control. Four exposure times (1, 2, 3, and 4 passes through the IPL chamber) and three initial temperatures (25, 30, and 35℃) were studied with untreated milk powder as the control. The samples were prepared as both milk powder and reconstituted milk for sensory evaluation. Using standard evaluating protocols, trained descriptive analysis panelists rated the aroma, flavor, and mouthfeel of these samples. Panelists compared the appearance of the IPL-treated samples that underwent a minimal or intense processing condition to the control by using a two-out-of-five difference test. Increasing the exposure time led to increased intensities of overall flavor, burnt flavor, and umami taste in both milk powder and reconstituted milk, while increasing temperature increased animal and sulfur aromas in reconstituted milk only. Compared to the control, all levels of exposure time at any initial temperature resulted in increased aroma and flavor including cardboard aroma, sulfur aroma, and brothy flavor in both milk powder and reconstituted milk. Only the 4-pass exposure at the initial temperature of 25℃ changed the appearance of milk powder. However, the appearance change was not noticeable in reconstituted milk. PRACTICAL APPLICATION: The standard evaluation protocols and lexicons provide useful tools for research on milk powder. Additionally, the understanding of critical factors impacting sensory properties will contribute to a better implementation of this decontamination technology.

The role of heat treatment in light oxidation of fluid milk.

Light-oxidized flavor (LOF) resulting from photooxidation of riboflavin following light exposure is one of the most common off-flavors in fluid milk. The sensory perception of LOF has been studied extensively in high temperature, short time pasteurized (HTST) milk, but few studies have evaluated ultrapasteurized (UP) milk. The objective of this study was to evaluate the role of heat treatment in the development of LOF in UP fluid skim milk. Skim milk was processed by HTST or by direct steam injection (DSI-UP) and subsequently exposed to 2,000-lx light-emitting diode light for various times. Sensory properties were monitored by descriptive analysis and threshold tests, and volatile compounds were evaluated by solid phase microextraction with gas chromatography-mass spectrometry. Dissolved oxygen and riboflavin were determined at each time point using an oxygen meter and ultra-performance liquid chromatography with a fluorescence detector, respectively. The entire experiment was performed in triplicate. Typical cardboard and mushroom flavors (LOF) were detected by trained panelists in HTST milk after 3.5 h of light exposure. In contrast, LOF was not detected by trained panelists in UP milk until 36 h of light exposure. Similarly, the best estimate threshold for LOF from untrained consumers (n = 101) was higher for DSI-UP milk (61.0 h) than for HTST milk (15.2 h). Milks with LOF were characterized by higher relative abundance of the lipid oxidation compounds hexanal and heptanal. Dissolved oxygen (DO) and riboflavin concentrations decreased with increased light exposure time, and the decrease was slower in UP milk compared with HTST milk. Initial DO concentration was investigated as a possible influence in LOF development because DSI-UP milks had lower initial DO concentrations than HTST milks. However, follow-up evaluations of deaerated HTST milks suggested that DO was not a significant factor in LOF development. These results demonstrate that UP milk is less sensitive to LOF than HTST milk, possibly due to sensory masking effects or antioxidant effects of volatile sulfur compounds. An enhanced understanding of light and storage effects on milks will assist with best practices when transporting and displaying fluid milk products for sale.

Radiation Exposure to the Thyroid After the Chernobyl Accident.

Introduction: The Chernobyl accident resulted in a considerable release of radioactivity to the atmosphere, particularly of Iodine-131 (131I), with the greatest contamination occurring in Belarus, Ukraine, and western part of Russia. Material and Methods: Increase in thyroid cancer and other thyroid diseases incidence in population exposed to Chernobyl fallout in these counties was the major health effect of the accident. Therefore, a lot of attention was paid to the thyroid doses, mainly, the 131I intake during two months after the accident. This paper reviews thyroid doses, both the individual for the subjects of radiation epidemiological studies and population-average doses. Exposure to 131I intake and other exposure pathways to population of affected regions and the Chernobyl cleanup workers (liquidators) are considered. Results: Individual thyroid doses due to 131I intake varied up to 42 Gy and depended on the age of the person, the region where a person was exposed, and their cow's milk consumption habits. Population-average thyroid doses among children of youngest age reached up to 0.75 Gy in the most contaminated area, the Gomel Oblast, in Belarus. Intake of 131I was the main pathway of exposure to the thyroid gland; its mean contribution to the thyroid dose in affected regions was more than 90%. The mean thyroid dose from inhalation of 131I for early Chernobyl cleanup workers was estimated to be 0.18 Gy. Individual thyroid doses due to different exposure pathways varied among 1,137 cleanup workers included in the epidemiological studies up to 9 Gy. Uncertainties associated with dose estimates, in terms of mean geometric standard deviation of individual stochastic doses, varied in range from 1.6 for doses based on individual-radiation measurements to 2.6 for "modelled" doses. Conclusion: The 131I was the most radiologically important radionuclide that resulted in radiation exposure to the thyroid gland and cause an increase in the of rate of thyroid cancer and other thyroid diseases in population exposed after the Chernobyl accident.

Inactivation of milk-borne pathogens by blue light exposure.

Food safety and quality management play a pivotal role in the dairy industry. Milk is a highly nutritious food that also provides an excellent medium for growth of pathogenic microorganisms. Thus, dairy industry focuses most of their processes and costs on keeping contamination levels as low as possible. Thermal processes for microbial decontamination may be effective; however, they cannot provide excellent organoleptic, nutritional, and decontamination properties simultaneously. In this scenario, microbial inactivation by exposure to blue light is a promising alternative method in the food industry due to its intrinsic antimicrobial properties free of any thermal effect. Therefore, this study aimed to determine the inactivation kinetics induced by blue light (λ = 413 nm) against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella Typhimurium, and Mycobacterium fortuitum cells suspended in whole milk or saline solution. We also performed a series of optic spectroscopies to investigate possible degradation of milk components. All species were sensitive to photoinactivation suspended either in saline solution or milk. Inactivation kinetics differs significantly depending on the suspension medium and each species is differently affected. All bacterial species tested presented more than 5 log10 of inactivation within less than 2 h of irradiation (720 J/cm2). Infrared spectroscopy did not reveal any significant alteration in any of the milk constituents (e.g., sugars, proteins, and lipids). Riboflavin (vitamin B2) was the only significantly degraded constituent found. Therefore, we conclude that microbial inactivation performed by blue light presents extraordinary potential for processes in the dairy industry.

The use of mid-infrared spectra to map genes affecting milk composition.

The aim of this study was to investigate the feasibility of using mid-infrared (MIR) spectroscopy analysis of milk samples to increase the power and precision of genome-wide association studies (GWAS) for milk composition and to better distinguish linked quantitative trait loci (QTL). To achieve this goal, we analyzed phenotypic data of milk composition traits, related MIR spectra, and genotypic data comprising 626,777 SNP on 5,202 Holstein, Jersey, and crossbred cows. We performed a conventional GWAS on protein, lactose, fat, and fatty acid concentrations in milk, a GWAS on individual MIR wavenumbers, and a partial least squares regression (PLS), which is equivalent to a multi-trait GWAS, exploiting MIR data simultaneously to predict SNP genotypes. The PLS detected most of the QTL identified using single-trait GWAS, usually with a higher significance value, as well as previously undetected QTL for milk composition. Each QTL tends to have a different pattern of effects across the MIR spectrum and this explains the increased power. Because SNP tracking different QTL tend to have different patterns of effect, it was possible to distinguish closely linked QTL. Overall, the results of this study suggest that using MIR data through either GWAS or PLS analysis applied to genomic data can provide a powerful tool to distinguish milk composition QTL.

Lipolysis and Oxidation in Ultra-High Temperature Milk Depend on Sampling Month, Storage Duration, and Temperature.

During storage, some factors (for example, storage duration and temperature) can affect milk stability and consumer acceptability. Thiobarbituric acid reactive substances (TBARSs), lipid classes, and fatty acid profiles in stored ultra-high temperature (UHT) milk were analyzed to assess the effects of storage time and temperature on lipid oxidation and lipolysis. With storage duration up to 12 months, the milk fat phase was separated and showed high levels of oxidation and lipolysis, manifested as increased levels of TBARS and free fatty acids. High oxidation levels decreased the percentage of unsaturated fatty acids (UFAs) in triacylglycerol and phospholipids. Higher storage temperatures (20, 30, and 37 °C) resulted in a higher degree of fat aggregation, oxidation, and lipolysis compared with refrigerated storage (4 °C). Additionally, sampling month of raw milk (May, July, and November) affected the lipid profiles of UHT milk during storage, with more UFA oxidized in July than in the other 2 months.

Short communication: Mycosporine-like amino acids protect natamycin against photodegradation in milk exposed to fluorescent or light-emitting diode light.

Natamycin has been used as a natural antimicrobial in dairy products, but the poor light stability of natamycin can limit usefulness in food products. Mycosporine-like amino acids are strong UV absorbers and might be useful as an additive to decrease light-induced degradations. Therefore, the objective of this study was to evaluate the photoprotective effect of mycosporine-like amino acids (MAA) in cow milk stored under 2 lighting conditions in retail commercial display cabinets with fluorescent and high intensity light-emitting diode illumination. When milk was exposed to both fluorescent and light-emitting diode light, natamycin degradation was very fast, and only 17.1 ± 0.9% of its original concentration was observed after 8 d at 4.0°C. On the other hand, by adding MAA into milk, natamycin was retained at 82.2 ± 0.9% and 92.2 ± 0.9% when low and high MAA levels were used, respectively. However, high MAA levels resulted in color changes. Therefore, MAA at low levels had a photoprotective effect for natamycin stability in cow milk exposed to light in refrigerated glass containers.

Does vitamin fortification affect light oxidation in fluid skim milk?

Off-flavors in milk related to light oxidation form due to photoxidation of native riboflavin and tetrapyrroles, resulting in an array of lipid oxidation compounds. Recent work has established that fortification with water-dispersible vitamin A can result in off-flavors in fluid skim milk caused by vitamin A degradation products in the vitamin premix. The objective of this study was to determine the role of vitamin fortification on light oxidation of high temperature, short time pasteurized fluid skim milk. First, the aroma profiles and aroma-active volatile compounds in light-exposed vitamin premixes were determined by exposing the premixes to fluorescent (FL) or light-emitting diode (LED) light at 2,000 lx at 4°C for 0, 2, 4, 8, or 24 h. A trained panel (n = 6) documented aroma profiles of each vitamin premix at each time point. Headspace solid-phase microextraction followed by gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS) were performed to characterize aroma-active compounds in light-exposed vitamin premixes. In the second experiment, commercial vitamin premixes (vitamin A and vitamin D in oil and water matrices) were used to fortify skim milk (vitamin A: 3,000 IU/946 mL; vitamin D: 600 IU/946 mL). Skim milk was pasteurized, homogenized, and packaged in 946-mL high-density polyethylene jugs. Milks were exposed to FL or LED light at 2,000 lx at 4°C for 4, 12, 24, or 48 h. Controls with and without vitamins and light shielding were included. Riboflavin and vitamin A and D degradation were quantified via ultra-high-performance liquid chromatography. A trained panel (n = 8) documented sensory profiles of milks at each time point. Lipid oxidation volatile compounds were quantified via solid-phase microextraction with GC-MS. Vitamin degradation volatile compounds were quantified via solvent-assisted sorptive stir bar extraction with GC-MS. Riboflavin, vitamin A, and vitamin D degradation were consistent with that reported in previous studies. We found no effect of vitamin fortification on development of typical light oxidation-related off-flavors (cardboard and mushroom) or lipid oxidation-related volatiles (hexanal and heptanal). A perfumey/floral flavor was documented in the oil-based vitamin A-fortified milk, suggesting that light exposure affected the off-flavors contributed by water- versus oil-based vitamin fortification. These results show no evidence that vitamin fortification at current levels provides any protection against light oxidation-related off-flavors in fluid milk.

Use of UV Treated Milk Powder to Increase Vaccine Efficacy in the Elderly.

Aging populations experience a decline in adaptive immune system function also known as immunosenesence. Protein nutrition has been shown to stimulate and strengthen the immune system, and such approaches are needed for this growing segment of the population. A controlled, randomized, double blind pilot study was conducted to compare two different protein sources (soy and dairy) as nutritional supplementation to enhance vaccine response. Our objective was to examine the immune stimulating effects of dairy protein subjected to ultraviolet radiation (UV-C) radiation treatment process instead of pasteurization. Participants were 21 healthy individuals over 60 years of age who consumed 6 g of the dairy protein or a comparison, soy isoflavone protein, twice a day for 8 weeks. DTaP vaccine administered at week 4. Non-parametric t-tests revealed a significant increase in Tetanus antibodies in the dairy group compared to the soy group at week 8. These findings suggest additional benefits of UV-C treated unheated dairy protein as a solution to counteract immunosenescence, but warrant further study in elderly and other populations that might benefit from immune system stimulation.

Efficacy of light-protective additive packaging in protecting milk freshness in a retail dairy case with LED lighting at different light intensities.

Light emitting diodes (LED) are rapidly developing as dominant lighting systems in dairy retail cases. Bright light is typically chosen to best exhibit milk products. However, high intensity LED lighting may create high potential for detrimental oxidation and destroying milk freshness. In this study, we investigated the interaction between LED light intensity, exposure time, and packaging material on limiting milk oxidation and protecting milk freshness and vitamins. Within 4 h of LED light exposure at an intensity as low as 1068 lx, light-induced oxidation occurred on 2% milkfat milk with commercial packaging including glass and translucent high-density polyethylene (HDPE) bottles. Higher light intensity (>4094 lx) and longer light exposure time (>24 h) rapidly increased the oxidation rate in milk. Polyethylene terephthalate (PET) packaging with lower oxygen permeability rate effectively reduced (P < 0.05) vitamin A degradation under low light intensity within 24 h. A combination of light-protective additive (TiO2) and oxygen barrier material (PET) successfully reduced (P < .05) the loss of dissolved oxygen and riboflavin, and decreased the formation of final oxidation products in milk, as measured by thiobarbituric reactive substances (TBARS), when exposed to high light intensity within 24 h. Lower LED light intensity in retail case was preferred by 50% of participants in a visual acceptance test; consumers are willing to consider pigmented packaging with limited visibility. Results of this study provides guidance for dairy industry in choosing appropriate LED lighting conditions and packaging to adequately display the milk products as well as minimize the degradation of milk nutrients and flavor.

Effect of Calcium on Absorption Properties and Thermal Stability of Milk during Microwave Heating.

During heating, there are a lot of physical and chemical changes in milk components, which are mainly reflected in the changes of proteins. Calcium ions in milk react with proteins to precipitate or form gels, and the thermal stability of milk is affected by the type and content of calcium. In this study, different calcium-fortified milk systems were treated by rapid conventional heating (RCV) and microwave heating (MV) to evaluate the effects of forms and concentration of calcium in liquid milk on microwave absorption properties and thermal stability of milk. It was found that the concentration of calcium ions on microwave energy absorption is not a significant influence, while the forms affected the systems dramatically. The thermal stability of milk during MV is remarkably affected by the forms of calcium ions. When adding ionized calcium, the calcium-fortified milk systems had poor thermal stability and severe agglomeration of protein, while the addition of milk calcium had little effect and was almost free from protein coagulation. It could be speculated that the metal ions in the microwave field could create a strong vibration that could trigger protein agglomeration through the combination of the surrounding casein phosphorylates.

Effects of microwave on extracellular vesicles and microRNA in milk.

This study demonstrates the effects of microwaves on the microRNA (miRNA) content of milk and milk extracellular vesicles (EV). We determined the miRNA concentration in milk subjected to different treatments using real-time PCR and a spectrophotometer. The miRNA expression and total RNA content of the microwaved milk samples were lower when compared with untreated milk. We measured the microstructure and the size distribution by scanning electron microscopy and dynamic light scattering to verify the loss of miRNA in microwaved milk due to damage to the EV. The results revealed that 2 different-sized EV were present and had an average size of 147.50 and 22.14 nm, respectively. Furthermore, acridine orange staining showed that the total RNA content in microwaved milk EV was lower than that in cow milk. These results suggest that EV may confer the protection and the stability of the miRNA in milk.

Using Fluorescence Spectroscopy To Identify Milk from Grass-Fed Dairy Cows and To Monitor Its Photodegradation.

Owing to its high ω-3 fatty acid content, milk from grass-fed dairy cows is becoming increasingly more attractive to consumers. Consequently, it is important to identify the origins of such products and to measure their content, at least relative to some standard. To date, chromatography has been the most extensively used technique. Sample preparation and cost, however, often reduce its widespread applicability. Here, we report the effectiveness of fluorescence spectroscopy for such quantification by measuring the amount of chlorophyll metabolites in the sample. Their content is significantly higher for milk from grass-fed cows compared to milk from grain/silage-fed cows. It is 0.11-0.13 µM in milk samples from grass-fed cows, whereas in milk from cows fed grain/silage rations, the concentration was 0.01-0.04 µM. In various organic milk samples, the chlorophyll metabolite concentration was in the range of 0.07-0.09 µM. In addition, we explored the mechanisms of photodegradation of milk. Riboflavin and chlorophyll metabolites act as photosensitizers in milk for type-I and type-II reactions, respectively. It was also observed that the presence of high levels of chlorophyll metabolites can synergistically degrade riboflavin, contributing to the degradation of milk quality.

Exposure to light-emitting diodes may be more damaging to the sensory properties of fat-free milk than exposure to fluorescent light.

Light exposure can damage the sensory properties of milk, leading to adverse consumer responses. This is presumed to be through the action of photosensitive compounds such as riboflavin, present in milk and capable of releasing energy when irradiated, leading to damage of proteins and fats in the milk. Light-emitting diode (LED) lighting is assumed to be less damaging to milk due to lower inherent power consumption. In this study, fat-free milk was exposed to LED and fluorescent light at 2,000 lx to compare the sensory thresholds of exposure, the flavor profile of milk produced by these exposures, and resultant consumer acceptance of the samples. Additionally, the effectiveness of light-protective packaging and supplementation with antioxidants was evaluated. The sensory threshold from LED exposure was no longer than from fluorescence, whereas with antioxidants (tocopherols and ascorbic acid), the majority of the panelists failed to discriminate milk exposed to LED light even at 48 h of exposure. Trained panelists described light-exposed milk as significantly higher in cardboard, old oil, and plastic, with LED exposure resulting in a marginally more plastic aroma, and fluorescent marginally more cardboard. Consumers reported higher liking for fluorescent-exposed samples versus those exposed to LED. The antioxidant-supplemented samples, and those exposed to LED light engineered to eliminate wavelengths below 480 nm (thus most of riboflavin's absorption peaks), resulted in significantly higher old oil aroma; however, the former received higher liking scores than LED-exposed samples. Light-protective packaging offered near-complete protection from LED exposure, with a similar flavor profile as unexposed milk, and the best liking scores of any treatment. Nevertheless, consumers disliked its appearance, due to unfamiliarity, suggesting some consumer education may be needed if this were to be an efficient protective strategy.

Immunotherapy for cow's milk allergy.

Oral immunotherapy (OIT) is used regularly for young children with cow's milk (CM) allergy and has been shown to be effective in several studies. However, adverse events occur frequently during OIT. Furthermore, there are only 5 randomized controlled trial studies of CM-OIT and these are low-powered single center trials. Therefore, evidence levels are also low and sometimes frequent and severe allergic events occur during the OIT. Furthermore, there are no standardized protocols in pediatric allergy guidelines from several countries and studies with long-term follow-up observations and clinical tolerance defined as sustained unresponsiveness are rare. Additionally, clinical tolerance by OIT is generally not well defined and obscure. Thus, several problems remain to be resolved, however we hope OIT in combination with omalizumab and less allergenic heated CM products will resolve these problems in the future.

Comparison of milk oxidation by exposure to LED and fluorescent light.

Light-induced oxidation of milk has been well studied. Exposure of milk to UV light facilitates the oxidation of fats to aldehydes, and the degradation of sulfur-containing amino acids, both of which contribute to off-flavors. In addition, vitamin A and riboflavin are easily degraded by UV light. These reactions occur rapidly and are exacerbated by bright fluorescent lights in retail dairy cases. The invention of white light-emitting diodes (LED) may provide a solution to this oxidation problem. In this study, fresh milk containing 1% fat and fortified with vitamin A and riboflavin was exposed to LED at 4,000 lx, or fluorescent light at 2,200 lx for 24 h. Milk samples exposed to LED or fluorescent light, as well as milk protected from light, were analyzed by a consumer acceptance panel, and a trained flavor panel. In addition, vitamin A, riboflavin, and the production of volatile compounds were quantified. Exposure to light resulted in a reduction of cooked/sweet, milkfat, and sweet flavors and increased the intensity of butterscotch, cardboard, and astringency. In general, exposure to fluorescent light resulted in greater changes in the milk than exposure to LED even though the LED was at higher intensity. Consumers were able detect off-flavors in milk exposed to fluorescent light after 12 h and LED after 24 h of exposure. The riboflavin and vitamin A content was reduced by exposure to fluorescent light, whereas there was no significant reduction caused by LED compared with the non-light-exposed control. Production of hexanal, heptanal, 2-heptanal, octanal, 2-octanal nonanal, dimethyl sulfide, and caproic acid vinyl ester from the light-induced degradation of fats was significantly higher with fluorescent than LED. Production of these compounds was significantly higher with both light treatments than in the control milk. This study indicates that LED is less destructive to milk than fluorescent light.

Effectiveness of Protective Activities for Rehabilitation of the Forage Lands in Russia and Belarus Contaminated as a Result of the Chernobyl Accident.

Regularities of changes in the content of (137)Cs in green fodder during the remote period after the CNPP accident depending on application of agro-technical and agrochemical activities are analyzed. It is revealed that the use of mineral fertilizers reduces receipt of (137)Cs from the soil to forage and further to a food chain. It is also established that agrochemical activities are more effective than agro-technical ones.

Light-induced lipid oxidation in sheep milk: effects of dietary grape seed and linseed, alone or in combination, on milk oxidative stability.

The present work aimed to investigate the milk oxidative stability when the sheep diet includes a source of polyphenols (grape seed, (GS)) and a source of polyunsaturated fatty acids (linseed, (LIN)), alone or in combination (MIX) compared to a control group (CON). For this purpose light-induced oxidation in milk was studied. After 24 h of light exposure the lipid hydroperoxides increased in milk in the LIN and MIX groups. The calculated ratio between the level of lipid hydroperoxides and unsaturated fatty acids (UFAs) in milk was lower in the GS and MIX than in the LIN group. At the same time the level of the ratio between hexanal/linoleic acid in milk was lower in the GS and MIX than in the CON group. Although the dietary inclusion of grape seed did not reduce the level of lipid oxidation products in sheep milk, it effectively reduced the extent of oxidation of UFA.

Efficacy of Ultraviolet (UV-C) Light in a Thin-Film Turbulent Flow for the Reduction of Milkborne Pathogens.

Nonthermal technologies are being investigated as viable alternatives to, or supplemental utilization, with thermal pasteurization in the food-processing industry. In this study, the effect of ultraviolet (UV)-C light on the inactivation of seven milkborne pathogens (Listeria monocytogenes, Serratia marcescens, Salmonella Senftenberg, Yersinia enterocolitica, Aeromonas hydrophila, Escherichia coli, and Staphylococcus aureus) was evaluated. The pathogens were suspended in ultra-high-temperature whole milk and treated at UV doses between 0 and 5000 J/L at a flow rate of 4300 L/h in a thin-film turbulent flow-through pilot system. Of the seven milkborne pathogens tested, L. monocytogenes was the most UV resistant, requiring 2000 J/L of UV-C exposure to reach a 5-log reduction. The most sensitive bacterium was S. aureus, requiring only 1450 J/L to reach a 5-log reduction. This study demonstrated that the survival curves were nonlinear. Sigmoidal inactivation curves were observed for all tested bacterial strains. Nonlinear modeling of the inactivation data was a better fit than the traditional log-linear approach. Results obtained from this study indicate that UV illumination has the potential to be used as a nonthermal method to reduce microorganism populations in milk.

Stability of fatty acid composition after thermal, high pressure, and microwave processing of cow milk as affected by polyunsaturated fatty acid concentration.

Interest has been increasing to enhance the contents of healthy polyunsaturated fatty acid (PUFA) in milk. However, trans fatty acids and conjugated linoleic acid (CLA) can be altered after thermal processing and high pressures disrupt the milk fat globule membrane, exposing the lipid core and helping its oxidation. The objective of the present research was to study whether processing can alter the fatty acid composition of milk and if these changes are affected by PUFA concentration as previous studies suggest. Two cow milk batches (500 L each), one naturally enriched in PUFA, were processed to obtain pasteurized; high temperature, short time; UHT; high pressure; and microwave pasteurized samples. The detailed fatty acid composition was analyzed with special attention to trans fatty acids and CLA isomers. Results showed that after high temperature, short time processing, total CLA content increased in both milk batches, whereas sterilization resulted in a sigmatropic rearrangement of C18:2 cis-9,trans-11 to C18:2 trans-9,trans-11. The extent of these effects was greater in milks naturally enriched in PUFA.