Oxidation Of Milk Fat Research Articles

Mathematical modeling of experimental data in the design of formulas for dairy products

mathematical modeling methods. The author analyzed the problems in the field of food technology and concluded that mathematical modeling is used in the following areas: clarification of technological process modes, designing recipes and assessing the quality of finished products, as well as predicting the shelf life of new products when they are put into production. The use of dihydroquercetin as a drug that prevents the oxidation of milk fat in the design of dairy products is substantiated. Mathematical modeling was carried out on the basis of experimental and analytical material obtained in laboratory and production conditions. Based on the maximum value of the objective functions, the optimal normalized mixtures and the maximum allowable concentration of dihydroquercetin were selected. The analysis of the received mathematical dependences and models is carried out, the system of linear equations is made. Purpose: to study the effect of natural bioflavonoid antioxidant on the oxidative processes of milk fat and the viability of lactic acid cultures and their associations by mathematical modeling in order to use it in the technology of a new product; conduct an analysis of mathematical dependencies and models, compose a system of linear equations. Methods: the article uses the method of mathematical analysis and the matrix method. Results and their significance: a mathematical model was developed for the dependence of the viability of probiotic cultures on the mass fraction of dihydroquercetin when designing recipes for a creamy-protein curd product, a matrix of the chemical composition of dairy ingredients was presented, and a system of linear equations for basic recipes was compiled. In the course of the study, the spatial configurations of dihydroquercetin, as well as its effect on the oxidative processes of milk fat, were studied. Mathematical modeling of experimental data on the study of the effect of dihydroquercetin on the viability of microorganisms with probiotic properties was carried out. The normalization of the complex of obtained results on the study of the influence of the mass fraction of dihydroquercetin on the fermentation process was studied. Controlled factors characterizing the process of fermentation of model media with dihydroquercetin have been determined. A rationing of the dihydroquercetin complex of more than 0.50% was established; the target function decreases to its minimum value of 0.53 with a mass fraction of dihydroquercetin of 1.00%.

Nanoemulsion: A novel delivery approach for thermosensitive IgG on inhibiting milk fat oxidation

IgG, a biologically active substance in bovine colostrum, is easily inactivated during heat treatment and edible process to lose its biological activity. Nanoemulsion can effectively protect IgG to maintain its biological activity from injurious treatment. In this study, a food-grade nanoemulsion system was developed to protect IgG from heat and acid damage. It can be found that the residual rate of nanoemulsion-protected IgG reaches 87.1 % after 10 min at 72 °C. After 5 min at 82 °C, the residual rate of IgG in nanoemulsion was 18.7 % higher than that in PBS. In the simulated gastric fluid at pH 2.0, the residual rate of IgG in the nanoemulsion reacted for 4 h was 21.5 % higher than that in PBS. It indicated that nanoemulsion system can improve the heat and acid resistance of IgG compared with others, which is attributed to the lowest water activity of nanoemulsion. The contents of hydroperoxide and malondialdehyde in the milk after storage for 72 h with nanoemulsion-protected IgG were 0.12 meq/kg and 0.04 mg/kg, respectively, less than that of PBS-protected IgG. IgG is protected by nanoemulsion can effectively protect its activity during processing, which provides a theoretical basis for its direct application in liquid milk.

Prospects for the Use of Non-Starter Strain Lactiplantibacillus Plantarum AG15 in Dairy Technology

The article presents the comprehensive study results of the technological and antioxidant potential of the Lactoplantibacillus plantarum AG15 strain recaptured from silage and demonstrating probiotic properties during dairy products fermentation. The work aims at determining influence of the L. plantarum AG 15 strain on the antioxidant characteristics of the creamy milk; and identifying the strain introduction potential in the hard cheese technology. The authors applied a step-by-step research scheme with the technological and antioxidant potential assessment of a non-starter strain of lactic acid bacteria L. plantarum AG15 under conditions of milk fermentation and cheese maturation. A man used strain L. plantarum AG15 for fatty milk fermentation and compared its effect with the starter strain Lactobacillus bulgaricus. Compared to L. bulgaricus, L. plantarum AG15 has lower acid-forming ability, forms a dense lactic acid gel with the high syneresis level. Milk fermented by the L. plantarum AG15 strain has greater antioxidant activity (tests for reducing and radical-binding ability), which reduces the accumulation level of malonic aldehyde in milk fat during storage. Considering the identified antioxidant and technological potential, at the next stage, the researchers used L. plantarum AG15 strain as a part of a cheese starter to produce semi-hard cheese. The additional introduction of the non-starter strain L. plantarum AG15 does not affect the chemical quality of cheese (moisture, protein and salt content), but improves its antioxidant properties, leading to a decrease in the milk fat oxidation. Changes in the microbial community structure of the starter culture through the introduction of a non-starter strain L. plantarum AG15 enables to produce cheese with improved antioxidant properties and a more pronounced acrid flavor, expanding the production possibilities of high-quality cheeses with the diverse taste.

Food-Derived Bioactive Peptides with Antioxidative Capacity, Xanthine Oxidase and Tyrosinase Inhibitory Activity

Bioactive peptides (BPs) released by proteases from different food protein sources are often served as antioxidants in food applications. This study aims to investigate 11 BPs derived from fish and egg white as potential natural antioxidants by antioxidant activity assays. The kinetic activity of the BPs against xanthine oxidase (XOD) and tyrosinase was also analyzed. The antioxidative capacity of the BPs indicated that VWWW (VW4, mackerel meat), followed by IRW (IW3, egg white) and VKAGFAWTANQQLS (VS14, tuna backbone protein), possessed the highest antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and reducing power (RP) assays. Both the free-radical scavenging score predicted from the AnOxPePred algorithm and the DPPH, ABTS and RP results indicated that VW4 was the best antioxidant. Furthermore, the XOD and tyrosinase inhibition by three selected peptides exhibited competitive patterns of effective inhibition. The half maximal inhibitory concentrations (IC50) of the peptides for XOD inhibition were 5.310, 3.935, and 1.804 mM for VW4, IW3, and VS14, respectively, and they could serve as competitive natural XOD inhibitors. The IC50 of the peptides for tyrosinase inhibition were 1.254, 2.895, and 0.595 mM for VW4, IW3, and VS14, respectively. Overall, VW4, IW3, and VS14 are potential antioxidants and natural XOD inhibitors for preventing milk-fat oxidation, and anti-browning sources for inhibiting food-derived tyrosinase oxidation.

Influence of Fat Concentration on the Volatile Production in Model Whey Protein Systems as Affected by Low Frequency Ultrasound

Whey protein systems with varying fat concentrations (WF) of 2, 4, and 6% (w/w) were treated by ultrasound at 20 kHz up to 10 min, which corresponded to energy densities ranging from 9.54 to 190.8 J mL−1, respectively. The volatile compounds produced were extracted by solid phase micro extraction (SPME) and analysed by gas chromatography-mass spectrometry (GCMS). The results showed that hydrocarbons, aldehydes, ketones, esters, and alcohols are the predominant volatiles present within WF mixtures. These volatile compounds primarily derived from lipid oxidation of milk fat or cleavage of fatty acids, while some aldehydes, ethyl acetate, and hexanol derived from both lipid oxidation of milk fat and protein degradation. The fat content had negligible effects on the production of volatile compounds. In contrast, the fatty acids showed insignificant changes within WF systems containing 2% (w/w) fat, while some significant changes were observed with 4% and 6% (w/w) fat containing WF systems. However, the sonication time significantly influenced both the production of volatiles and the changes in fatty acids irrespective of the fat concentration highlighting the influence of both chemical and physical effects generated through acoustic cavitation.

Variation of volatile composition during the production of microencapsulated cream powder

The variation of volatile compounds during production of microencapsulated cream powder was investigated. First, maltodextrin (DE18) and sodium caseinate as wall materials were used to obtain microencapsulated cream as an oil-in-water emulsion, then it was spray-dried to produce the microencapsulated cream powder. Headspace solid-phase microextraction was used for isolation of volatiles and gas chromatography-mass spectrometry for identification. Results showed the volatile composition and amounts varied significantly during production of the microencapsulated cream powder. The microencapsulation of volatile acids and lactones in the cream was successfully performed. During spray drying, methyl ketones and limonene concentration decreased while the concentration of aldehydes (especially straight-chain aldehydes) significantly increased, indicating milk fat oxidation. Moreover, the concentration of a heat-treatment-related compound (furfural) increased and a methyl ketone degradation product (2-heptanol) was formed during spray drying.

Research of milk fat oxidation processes during storage of butter pastes

Basic quality indicators studied: acidity, peroxide, anisidine value and integrated value of complete fat oxidation. Butter paste was selected as a reference, consisting of butter, skim milk powder and fat-soluble emulsifiers. Peroxide value during storage at the temperature of (4 ±2 °С) for the first 4 days did not exceed 5.0 1/2 О mmol.kg-1, on the 15th day fat peroxide value of butter paste with milk-vegetable protein exceeded permissible limits that is indicative of milk fat contamination. At the temperature of (-3 ±1 °С) butter paste fat couldn't be qualified as fresh when storing during 15 days, peroxide value exceeds permissible limits on the 25th day of storage. Rising of the peroxide value above 5 1/2 О mmol.kg-1 was detected on the 25th day of storage, exceeding of threshold value was on the 45th day. It was established that rate of oxidation processes in butter pastes with vegetable protein is the highest among all studied samples in each particular control and observation point. It was determined that the rate of secondary lipid oxidation depends on the storage temperature and is observed when storing butter paste samples at a temperature of (-3 ±1 °С) on the 10th day, (-24 ±2 °С) – on the 30th day of storage. Acid value did not exceed recommended limits (2.5 °K) and was on average – 2.3 °K when storing butter paste during 10 days at a temperature of (4 ±2 °С); 2.1 °K during 20 days at the temperature of (-3 ±1 °С), 2.4 °K during 40 days at the temperature of (-24 ±2 °С). In view of obtained results of fat phase stability evaluation of studied butter pastes, the following storage maximum time is recommended: at the temperature of (4 ±2 °С) ‒ 7 days, at the temperature of (-3 ±1 °С) – 15 days, at the temperature of (-26 ±2 °С) ‒ 30 days.

Development of an innovative apparatus using UV‐C for controlling the number of microorganisms in raw milk after milking

This study was conducted to investigate the effect of UV‐C irradiation on the reduction of microorganisms in raw milk. The experiments were carried out by varying the flow rates of 2, 4 and 7 L/min with 39W and 48W UV‐C. The number of microorganisms was reduced by 4.70 (39W) and 4.60 log10 CFU/mL (48W) at 120 min. With the residence time of 4.95 s and the UV‐C doses of 98 and 109.9 mJ/cm2 at 253.74 nm, the reduction of microorganism was clearly observed with no significant influence of different UV‐C power settings on the oxidation of milk fat.

Effect of milking frequency and α-tocopherol plus selenium supplementation on sheep milk lipid composition and oxidative stability

The aim of this research was to study the effect of milking frequency [once-daily milking (ODM) vs. twice-daily milking (TDM)] and antioxidant (AOX) supplementation on fatty acid (FA) profile and oxidative stability in sheep milk. Sixteen Assaf ewes were used; 8 did not receive any vitamin-mineral supplement (control), and the other 8 received an oral dose of 1,000 IU of α-tocopherol and 0.4 mg of Se daily. The experiment consisted of 2 consecutive periods; the first was 3 wk with TDM of both mammary glands. The second period was 8 wk and consisted of ODM of one mammary gland and TDM of the other gland. All ewes were fed ad libitum the same total mixed ration from lambing and throughout the experiment. There were no differences in plasma or milk Se concentrations between control and AOX ewes. However, plasma and milk α-tocopherol concentrations and AOX capacity were increased in ewes receiving the AOX supplement. Milk FA profile was practically unaffected after 21 d of AOX supplementation. However, after 77 d, AOX supplementation increased the relative percentage of C16:0 and cis-9 C18:1 and reduced the proportions of some saturated FA with less than 16 carbons and cis-9 C12:1. Antioxidant supplementation had no effect on the proportions of conjugated linoleic acid or total polyunsaturated FA (PUFA) but decreased the proportion of trans-7,cis-9 C18:2 and increased that of n-6 C20:3. Once-daily milking did not affect α-tocopherol, Se, or fat resistance to oxidation in milk. Total monounsaturated FA, cis-9 C16:1, and several cis and trans isomers of C18:1 were increased and total saturated FA were decreased in milk from ODM glands. Compared with TDM, ODM increased the proportions of cis-9,cis-12 C18:2 and several isomers of C18:2 and reduced those of cis-9,cis-12,cis-15 C18:3 and some PUFA of 20 and 22 carbons, but total proportion of PUFA was unaffected. Once-daily milking and AOX supplementation modified milk FA profile, but the effects of ODM could be considered of little biological relevance for consumer health. Supplementing ewes with α-tocopherol plus Se could be considered an effective strategy to improve plasma AOX status and reduce milk fat oxidation without substantial changes in the milk FA profile.

Thymus capitatus essential oil ameliorates pasteurization efficiency.

This work aims to characterize Thymus capitatus essential oil and to investigate its preservative effects on raw milk quality alone or combined to pasteurization heat treatment. To study its preservative effect, 1mgl-1 of T. capitatus essential oil, characterized by GC-MS, was added to pasteurized or raw milk. The evaluation of milk quality was made by consulting samples total acidities, peroxide values and their total microbial counts, as compared to control milks. Assays were made immediately and after every 48h of incubation at room temperature throughout 6days. Results showed that the incorporation of T. capitatus EO to pasteurized milk was the most efficient treatment that inhibited milk deterioration. Combining pasteurization to EO incorporation into raw milk inhibited completely the contaminant bacterial growth to the second day of incubation. Moreover, until the fourth day, no statistical differences have been recorded on the total acidity of incorporated and pasteurized milk samples, while raw milk acidity exceeded 55g of lactic acid equivalentl-1. Considering milk fat oxidation, adding T. capitatus EO to pasteurized milk has significantly retarded milk peroxide production to day 4. In conclusion, Thymus capitatus essential oil, combined to pasteurization, presents an interesting potency to act as milk stabilizer.

Efecto de la Suplementación con Medicago sativa (Alfalfa) sobre Algunos Parámetros de la Leche Bovina

El objetivo de este trabajo fue determinar si la suplementación con alfalfa en vacas en producción podría generar un efecto antioxidante y modificar la composición de los ácidos grasos de la leche. Se utilizaron 19 vacas distribuidas en un grupo tratado (suplementado con alfalfa; n=11) y un grupo control (n=8). Se determinó el nivel de oxidación de la grasa de la leche (prueba de jabón de cobre), la calidad composicional y la presencia de ácidos grasos (cromatografía de gases) en la leche. La grasa de la leche de los animales suplementados mostró mayor estabilidad y menor oxidación respecto al grupo control, mostrando un efecto antioxidante, aun en aquella leche que se mantuvo 14 días a temperatura ambiente. Asimismo, hubo aumento de ácidos grasos poliinsaturados y disminución de los saturados, y aumento del porcentaje de grasa total de la leche. Se concluye que la suplementación con alfalfa da mayor estabilidad a la grasa de la leche por su efecto antioxidante y mejora la proporción de ácidos grasos poliinsaturados con disminución de los saturados, lo cual podría ser más benéfico para la salud del consumidor.

Effects of different fat mixtures on milk fatty acid composition and oxidative stability of milk fat

The experiment was carried out to determine effects of different fatty acids (FA) mixtures on milk FA composition and milk fat oxidation change. Thirty-six dairy cows were used in a completed design experiment for 8 weeks. Cows were fed one of three lipid supplements (1) short- and medium-chain fatty acids (SMCFA), (2) butterfat, and (3) long-chain fatty acids (LCFA). Data were analyzed using MIXED procedure of SAS. Daily dry matter intake (DMI), milk yield, and milk protein, total solids (TS), lactose, free fatty acids (FFA) content were unaffected among 3 treatments, whereas milk fat concentration was decreased (P<0.05) as carbon chain length increased in supplement lipid. Relative to SMCFA, 12:0, 14:0 and 16:0 concentrations in milk fat from cows on butterfat and LCFA treatment were decreased (P<0.05). Proportions of cis9-18:1, trans9-C18:1, and cis9, trans11-conjugated linoleic acid (CLA) were increased by 15.5, 74.3, and 20.3% (P<0.05) in milk fat from cows on LCFA compared with cows on SMCFA. Similar increases in trans9-18:1, trans11-18:1, cis9, trans11-CLA, 18:2n-6 and 18:3n-3 were 34.2, 31.5, 21.4, 11.0, and 15.4% (P<0.05) in butterfat treatments, respectively. Furthermore, activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were decreased (P<0.05) when increased long-chain FA in diets, while concentration of malondialdehyde (MDA) was increased (P<0.01) in bovine milk. Our results indicated that long-chain FA exhibit positive effects on milk FA composition, but may decrease oxidative stability of milk fat.

Influence of Linolenic Acid Content on the Oxidation of Milk Fat

Increasing the content of alpha-linolenic acid in milk fat might be desirable to meet consumer concerns about dietary healthfulness. However, the rich content of polyunsaturated fatty acids (PUFAs) will influence the oxidative stability of milk fat. This experiment was carried out to determine the effects of infusion with different amounts of high-linolenic perilla fatty acid (HLPFA) emulsion into the duodenum of dairy cows on milk fatty acid profile and the susceptibility of milk fat to oxidation. In a crossover design, 4 multiparous Holstein cows were infused duodenally with increasing amounts (0, 40, 80, 120, or 160 g/day) of free fatty acids from HLPFA emulsion or with carrier alone. Continuous infusions (20 to 22 h/day) were for 7 days at each amount. Infusions were homogenates of HLPFA with 15 g/day of xanthan gum, 5 g/day sodium alginate, and 25 g/day Tween 80; controls received carrier only. The concentration of n-3 PUFAs, especially alpha-linolenic acid, in milk fat increased linearly as HLPFA infusion increased, but the saturated fatty acids decreased linearly. The milk production and the activity of superoxide dismutase, glutathione peroxidase, and catalase in milk tended to decrease quadratically. The milk fat percentage, however, tended to increase. The concentration of malondialdehyde increased quadratically in milk fat. Results suggest that infusion with HLPFA emulsion at varying amounts enhanced the content of n-3 PUFAs in milk fat over the length of experiment but decreased the oxidative stability of milk fat.

Influence of vitamin E supplementation on spontaneous oxidized flavour of milk in dairy buffaloes

Twenty‐four Murrah buffaloes (60 days pre‐partum) were divided into four equal groups (T 1 , T 2 , T 3 and T 4 ) and were supplemented with 0, 1000, 1500 and 2000 IU α‐tocopheryl acetate per day up to 30 days of lactation, and half of these doses from 30 to 60 days of lactation. Milk samples collected fortnightly were analysed for vitamin E, fat, and development of oxidized flavour, with and without copper addition by a panel of judges, and chemically by the thiobarbituric acid test. Scores for oxidized flavour ranged from 0 to 10 with 0–4 as definite, 5–7 as light and 8–10 having no defect. The α‐tocopherol content in milk fat (µg/g) averaged 20.55, 25.56, 29.98 and 31.38 in T 1 , T 2 , T 3 and T 4 groups, respectively. The addition of Cu in the milk significantly increased milk fat oxidation. Better stability of milk in T 3 and T 4 groups was observed, which might be due to a higher level of milk α‐tocopherol. Addition of 1500 IU α‐tocopheryl acetate in the diet of buffaloes helped in improving the oxidative stability of milk.

Effect of legume silages fed to Holstein dairy cows on plasma alpha-tocopherol concentration, milk alpha-tocopherol and malonic dialdehyde in milk samples stored at 4°C and 20°C

Alpha-tocopherol is the natural antioxidant in milk preventing the oxidation of milk fat and development of off-flavour and off-odour. The feeding of dairy cows can significantly affect plasma and milk concentrations of α-tocopherol. There is growing interest in the use of legumes in milk production and so it is important to investigate their effects on milk a-tocopherol as well as the oxidation of milk fat during storage and, hence, shelf-life of milk.

The Effect of Vitamin E Supplementation of Cow Diets Containing Rapeseed and Linseed on the Prevention of Milk Fat Oxidation

Two experiments involving lactating Holstein cows were carried out to quantify the effect of a 550-g supplement of lipids from extruded rapeseed and linseed on milk fatty acid profiles and the susceptibility of milk fat to oxidation. The effect of a daily oral supplement containing 9616 IU of vitamin E (all-rac-α-tocopheryl acetate) on milk α-tocopherol and protection against oxidation was also evaluated. The intake of oilseeds decreased protein and fat contents in milk, and the proportion of all C18 fatty acids increased. The trans isomers were 2.7 and 10.76% of the milk fatty acids, respectively, for cows fed the control diet and the diet containing extruded rapeseed and linseed. The ratio of oleic to palmitic acid was doubled, and the resistance to oxidation was reduced by 30 to 40% in both experiments. The dietary vitamin E supplement increased the α-tocopherol concentration in milk by about 45% and was sufficient to prevent milk fat depression and oxidation. The diet containing oilseeds and supplemented with an adequate amount of vitamin E allowed cows to yield milk that could be used to manufacture butter with high oleic acid content, good spreadability, and resistance to oxidation.

Tocopherols, retinol, beta-carotene and fatty acids in fat globule membrane and fat globule core in cows' milk.

Milk fat globule membranes (MFGM) were isolated from milk from cows injected intraperitoneally with dl-alpha-tocopherol acetate. The fatty acid composition and content, and the contents of tocopherols, retinol and beta-carotene were determined and compared with the composition and content in the original cream sample. Intraperitoneal injection of 10 g dl-alpha-tocopherol acetate elevated the alpha-tocopherol content in the milk fat from 13-30 to 50-70 micrograms alpha-tocopherol/g milk fat 2-3 d after injection. The increase depended on the alpha-tocopherol status of the cow prior to injection. The concentrations of retinol and beta-carotene in the milk fat were unchanged after the alpha-tocopherol injections. MFGM fatty acids made up 18-27 g/kg total fatty acids in the milk fat. However, the proportions of monounsaturated and polyunsaturated fatty acids were higher in MFGM than in total milk fat, while the proportion of saturated fatty acids was lower in MFGM (P < 0.001). Thus, the long-chain polyunsaturated fatty acids in MFGM constituted approximately 40-70 g/kg total milk fat. alpha-Tocopherol was the only fat-soluble vitamin detected in MFGM; gamma-tocopherol, retinol and beta-carotene were detected only in the cream. A significant relationship between alpha-tocopherol contents in cream and MFGM was found: (alpha-tocopherol in MFGM fatty acids) = -1652 x (1/ln(alpha-tocopherol in cream fatty acids)3) + 97 (r = 0.857, P < 0.001) when the contents of alpha-tocopherol were expressed as microgram/g fatty acid. According to this equation the upper limit for incorporation of alpha-tocopherol into MFGM is 97 +/- 5 micrograms/g MFGM fatty acids. Thus, under normal farming conditions the alpha-tocopherol content will be highest in MFGM. However, in cream with an alpha-tocopherol concentration < 15 micrograms/g cream fatty acids the concentration in MFGM will be lower and furthermore will decrease rapidly. The possible importance of this relationship in relation to the oxidation of milk fat is discussed.

Cooling, Storing and Quality of Raw Milk

Abstract Full-scale experiments with cooling of raw milk of good initial quality from a herd of 70 dairy cows have been performed under practical farm conditions, with different cooling and storage conditions, including instant cooling in a continuous process versus normal cooling in a batch process. During each milking, the milk was divided equally and successively for different cooling procedures. Quality evaluations (number of bacteria, acidity and oxidation of fat, sensoric quality) indicated that instant cooling/continuous process compared with normal cooling/batch process over 2.5 hours, both to 4°C, resulted in a slightly slower bacterial growth and a slightly slower hydrolysis and oxidation of milk fat. Instant raw milk cooled and stored at 2.5°C maintained a good quality for about one to two days more than when normal cooling over 1.5 hours and storing at 4°C was used.

Oxidative Stability of Anhydrous Milkfat Microencapsulated in Whey Proteins

ABSTRACTThe chemical stability was studied on anhydrous milkfat (AMF) encapsulated in whey protein isolate (WPI) and WPI combined with lactose (1:1 w/w WPI/L). AMF‐containing microcapsules, as well as bulk milkfat, were stored at 20°C with light, 40°C without light, and 50°C with and without light for up to 12 mo. Milkfat oxidation was monitored by oxygen uptake in headspace and hexanal accumulation. In all cases, AMF oxidation was significantly limited by microencapsulation in WPI or WPI/L. Whey proteins are effective microencapsulating agents.

Prooxidative and antioxidative effects of phospholipids on milk fat

The effects of dipalmitoylphosphatidylethanolamine (DPE) and dipalmitoylphosphatidylcholine (DPC) on milk fat oxidation was examined at 50°C and 95°C under various conditions by monitoring oxygen uptake and fatty acid composition. DPE strongly inhibited milk fat oxidation both at 50°C and 95°C in the absence of water. DPC was less effective than DPE. In aqueous systems, the reverse was observed. DPE accelerated milk fat oxidation at both 50°C and 95°C. DPC accelerated the oxidation at 50°C, but inhibited it at 95°C. The free amino group in DPE may be responsible for its inhibiting effect in the dry system. The accelerating activity of DPE in the aqueous system is probably due to the formation of a more dispersed structure with better oxygen accessibility.