Fatty acids in bovine milk fat

Milk fat contains approximately 400 different fatty acid, which make it the most complex of all natural fats. The milk fatty acids are derived almost equally from two sources, the feed and the microbial activity in the rumen of the cow and the lipids in bovine milk are mainly present in globules as an oil-in-water emulsion. Almost 70% of the fat in Swedish milk is saturated of which around 11% comprises short-chain fatty acids, almost half of which is butyric acid. Approximately 25% of the fatty acids in milk are mono-unsaturated and 2.3% are poly-unsaturated with omega-6/omega-3 ratio around 2.3. Approximately 2.7% are trans fatty acids

Nutrient density of beverages in relation to climate impact

The food chain contributes to a substantial part of greenhouse gas (GHG) emissions and growing evidence points to the urgent need to reduce GHGs emissions worldwide. Among suggestions were proposals to alter food consumption patterns by replacing animal foods with more plant-based foods. However, the nutritional dimensions of changing consumption patterns to lower GHG emissions still remains relatively unexplored. This study is the first to estimate the composite nutrient density, expressed as percentage of Nordic Nutrition Recommendations (NNR) for 21 essential nutrients, in relation to cost in GHG emissions of the production from a life cycle perspective, expressed in grams of CO2-equivalents, using an index called the Nutrient Density to Climate Impact (NDCI) index. The NDCI index was calculated for milk, soft drink, orange juice, beer, wine, bottled carbonated water, soy drink, and oat drink. Due to low-nutrient density, the NDCI index was 0 for carbonated water, soft drink, and beer and below 0.1 for red wine and oat drink. The NDCI index was similar for orange juice (0.28) and soy drink (0.25). Due to a very high-nutrient density, the NDCI index for milk was substantially higher (0.54) than for the other beverages. Future discussion on how changes in food consumption patterns might help avert climate change need to take both GHG emission and nutrient density of foods and beverages into account

Bioactive Proteins in Bovine Milk - Studies on Glutathione Peroxidase, Lactoferrin and Immunoglobulins

Many proteins in bovine milk exhibit specific biological activity in addition to their established nutritional value as source of protein. Examples of such bioactive proteins are extracellular glutathione peroxidase, lactoferrin and immunoglobulins. Extracellular glutathione peroxidase (eGSHPx) fulfils an antioxidative function, immunoglobulins are antimicrobial, and it has been suggested that lactoferrin exhibits both of these properties. These functions may be of importance in the quality of milk and other dairy products, the influence of milk on human health and in the use of milk as a source of bioactive components in food or pharmaceutical products. Therefore, a good under-standing of the relation between thermal stability and bioactivity is important for the optimal use of bioactive proteins. In this thesis, antioxidative factors in milk are reviewed, both enzymatic and non-enzymatic factors, and a relationship between the protein antioxidants is proposed. For one of the antioxidant enzymes, eGSHPx, a purification strategy for its isolation from bovine plasma is described for the first time. The purified eGSHPx was used to develop a new immunological assay of it and, moreover, a method of measuring its activity in milk and whey was optimised. The glutathione peroxidase (GSHPx) activity in bovine milk was found to be similar to that in human milk, 25 to 50 U mL-1. The effect of storage and heating on GSHPx in milk and on pure eGSHPx and cellular glutathione peroxidase (cGSHPx) was also studied. An important finding was that the activity of GSHPx in milk and whey persisted after heat treatment at 72°C for 2 min, indicating that some industrially used pasteurisation processes will not affect the enzyme activity. Furthermore, studies on the thermal stability of immunoglobulins showed them to have a higher unfolding temperature, 80°C, than eGSHPx (69°C), but both of these unfolding temperatures were in the same range as those of other whey proteins. Finally, the influence of the antimicrobial activity of immunoglobulins and lactoferrin on the growth of starter cultures was evaluated in milk with a somatic cell count (SCC) below about 400 000. The concentration of the immunoglobulins IgA, IgG2, IgM and lactoferrin, as well as the prolonged fermentation time, could be used as markers of processability in addition to SCC. The addition of zinc to cows’ feed significantly increased the concentration of IgA, IgG2 and lactoferrin, while no effect was observed on SCC. The delay in time before growth commenced of starter cultures was also extended indicating that the immune response was affected by zinc supplementation

Antioxidative factors in milk

Lipid auto-oxidation in milk is affected by a complex interplay of pro- and antioxidants. Several of these compounds are also important nutrients in the human diet and may have other physiological effects in the gastrointestinal tract and other tissues. Among antioxidative enzymes superoxide dismutase catalyses the dismutation of superoxide anion to hydrogen peroxide. The degradation of hydrogen peroxide can be catalysed by catalase and the selenoprotein glutathione peroxidase. The latter enzyme can also degrade lipid peroxides. Lactoferrin may have an important role by binding pro-oxidative iron ions. The occurrence of different forms of these antioxidative proteins in milk and available data on their functional role are reviewed. More remains to be learnt of individual compounds and as an example the potential role of seleno compounds in milk is virtually unknown. Antioxidative vitamins in milk can provide an important contribution to the daily dietary intake. Moreover vitamin E and carotenoids act as fat-soluble antioxidants, e.g. in the milk fat globule membrane, which is regarded as a major site of auto-oxidation. Vitamin C is an important water-soluble antioxidant and interacts in a complex manner with iron and fat-soluble antioxidants. The concentrations of these compounds in milk are affected by cow feeding rations and milk storage conditions. Since milk contains a number of antioxidants many reactions are possible and the specific function of each antioxidant cannot easily be defined. There are indications that other compounds may have antioxidative function and measurement of total antioxidative capacity should be a useful tool in evaluating their relative roles

Effect of polymorphisms in the leptin, leptin receptor and acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) genes and genetic polymorphism of milk proteins on bovine milk composition.

The relations between cow genetics and milk composition have gained a lot of attention during the past years, however, generally only a few compositional traits have been examined. The aim of this study was to determine if polymorphisms in the leptin (LEP), leptin receptor (LEPR) and acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) genes as well as genetic polymorphism of β-casein (β-CN), κ-CN and β-lactoglobulin (β-LG) impact several bovine milk composition traits. Individual milk samples from the Swedish Red and Swedish Holstein breeds were analyzed for components in the protein, lipid, carbohydrate and mineral profiles. Cow alleles were determined on the following SNP: A1457G, A252T, A59V and C963T on the LEP gene, T945M on the LEPR gene and Nt984+8(A-G) on the DGAT1 gene. Additionally, genetic variants of β-CN, κ-CN and β-LG were determined. For both the breeds, the same tendency of minor allele frequency was found for all SNPs and protein genes, except on LEPA1457G and LEPC963T. This study indicated significant (PA) and LEPC963T (T>C), whereas total Ca, ionic Ca concentration and milk pH were affected by LEPA1457G, LEPA59V, LEPC963T and LEPRT945M. However, yields of milk, protein, CN, lactose, total Ca and P were mainly affected by β-CN (A2>A1) and κ-CN (A>B>E). β-LG was mainly associated with whey protein yield and ionic Ca concentration (A>B). Thus, this study shows possibilities of using these polymorphisms as markers within genetic selection programs to improve and adjust several compositional parameters

Antioxidant capacity of bovine milk as assayed by spectrophotometric and amperometric methods

The total antioxidant capacity (TAC) of bovine milk, whey, and low-molecular-weight (LMW) fractions of whey was investigated using spectrophotometric methods including an ABTS-based method (reduction of the cation radical of 2,2′-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid)) and a FRAP method (reduction of Fe3+). Significant antioxidant capacity in milk and whey was demonstrated by the ABTS method (TAC(ABTS)), and it apparently increased with increasing pH. TAC (ABTS) was several-fold higher in milk than in whey, which had a slightly higher TAC than a LMW fraction prepared from it. Also the FRAP method could be used to demonstrate TAC in whey, although the low pH necessary for this method led to some protein precipitation. Most of the ferric-reducing activity of whey was found in the LMW fraction. The TAC values obtained using these methods were also compared to those obtained using a newly developed flow-injection amperometric (FIAmp) procedure for LMW fractions. High correlations were found for the TAC values of LMW samples obtained by the ABTS, FRAP and FIAmp methods (R2>0.8, P<0.001). Furthermore, to identify the major antioxidants in the LMW fraction, it was treated by uricase. Since most of the TAC (using ABTS, FRAP and FIAmp methods) was removed by uricase treatment, it could be concluded that urate is the major antioxidant in the LMW fraction. Also the effect of heat treatment on TAC in milk and whey was monitored. After heating of whey at 63°C for 1 h, TAC(ABTS) tended to increase by at least 20%, while TAC(FRAP) was not significantly changed. In milk, TAC(ABTS) remained constant during the same heat treatment. It is concluded that the methods tested gave the most reliable results for the LMW fraction of whey and that the use of several methods is necessary to characterise the antioxidant capacity of milk

Two-dimensional gel electrophoresis of proteins and peptides in bovine milk

Proteins and peptides in bovine milk and colostrum were separated by two-dimensional gel electrophoresis (2-DE). The proteins were separated in the first dimension by isoelectric focusing in the pH ranges 4-7 and 6-11, and in the second dimension by sodium dodecyl sulphate polyacrylamide gel electrophoresis on 12.5% T homogeneous gels. The peptides were separated in the pH range 3-10 in the first dimension, while 15% T homogeneous gels were used in the second dimension. 2-DE evaluation of samples with various somatic cell counts showed an increased number of peptides with increased cell count. 2-DE analysis of samples heated at 65 and 85 degreesC for 30 min showed a decrease in the number of proteins and peptides with increased temperature. Colostrum exhibited a peptide pattern in which the intensity and number of spots decreased with time postpartum. These results show that 2-DE is a useful tool to detect variations of proteins and peptides in milk

Immunoglobulins, growth factors and growth hormone in bovine colostrum and the effects of processing

In colostrum collected 0-80 h postpartum the contents of immunoglobulins (Igs), transforming growth factor beta-2 (TGF-beta2), insulin-like growth factor-1 (IGF-1) and growth hormone (GH) were analysed. Colostrum initially contained 90 mg mL(-1) IgG1, 2.8 mg mL(-1) IgG2, 1.6 mg mL(-1) IgA, 4.5 mg mL(-1) IgM, and these concentrations declined by 92%, 87%, 93% and 84%, respectively, in the samples collected later. Of the growth factors, colostrum initially contained 289-310 ng mL(-1) TGF-beta2 and the concentration diminished to 66 ng mL(-1). The content of IGF-1 and GH postpartum decreased from 870 to 150 ng mL(-1), and from 0.17 to < 0.03 ng mL(-1), respectively. Heat treatment and freeze-drying of colostral whey decreased the content of Igs to 75%, while the contents of IGF-1 and TGF-beta2 were unaffected. A similar processing, including filtration steps reduced also the IGF-1 and TGF-beta2 by 25%. IgM seems to be the most sensitive of the Igs to processing. (C) 2002 Elsevier Science Ltd. All rights reserved