Raw Milk Fat Research Articles

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Adulteration of milk fat in raw milk with vegetable oil/ fats with pre-adjusted BR- reading, Reichert Meissl and Polenske values is becoming a common practice in the present scenario of rampant adulteration of milk and milk products. Detection of such type of adulteration using traditional or routine methods wherein physico-chemical constants of milk fat are used as a basis becomes impossible and continues to be a challenge for the dairy industry. Hence, in the present study, relatively rapid and convenient protocol based on Reversed-phase thin layer chromatographic was developed to check the purity of milk fat in milk. Using the Reversed- phase thin layer chromatographic protocol the added adulterant oils (rice bran oil, soybean oil, sunflower oil and groundnut oil) in milk could be detected to the minimum level of 1%.

Change in interfacial properties of milk fat globules by homogenization and thermal processing plays a key role in their in vitro gastrointestinal digestion

The effects of homogenization, homogenization plus thermal processing including high temperature short time (HHTST) or ultra-high temperature (HUHT) treatment on digestion and interfacial properties of milk fat globules during simulated gastrointestinal digestion were investigated. Compared to raw milk fat globules, homogenization and thermal processing increased the initial digestion rate of milk fat globules. Homogenization increased the release of middle- and long-chain fatty acids, HHTST increased the release of unsaturated fatty acids, and HUHT increased the release of all types of fatty acids under gastrointestinal digestion. After homogenization, milk proteins (caseins and whey proteins) increased but glycosylated molecules decreased, both of which were at the surface of milk fat globules. The amount of glycosylated molecules at the surface of HHTST milk fat globules and the amount of denatured milk proteins at the surface of HUHT milk fat globules were higher than those of homogenized milk fat globules. During gastrointestinal digestion, fat globules in HHTST milk possessed higher amount of glycosylated molecules and more integrated phospholipid layers, and HUHT milk fat globules had more filamentous phospholipid layers, and less integrated phospholipid layers and glycosylated molecules than those of homogenized milk fat globules. Therefore, the changes in composition and microstructure of glycosylated molecules and phospholipid layers at the surface of milk fat globules induced by homogenization and thermal processing might contribute to the digestion difference of milk fat globules.

A simplified protocol for fatty acid profiling of milk fat without lipid extraction

Determination of the fatty acid profile of milk fat generally involves a protocol that comprises total lipid extraction, transesterification and GC analysis. The lipid extraction step is time-consuming and often employs toxic solvents such as chloroform. A novel protocol is presented here that skips the lipid extraction step and allows the determination of fatty acid composition via direct methylation of milk fat isolated after centrifugation of raw milk. This new method is reliable for relative quantification of fatty acids in raw milk fat and offers a much higher throughput compared with the classical methods.

Research on Rapid Detection Method of Protein and Fat in Raw Milk Based on Mid-infrared Spectrum

In this paper raw milk was taken as the research object, using mid-infrared spectrum analysis method rapidly tests protein and fat content in raw milk through establishing quantitative analysis model. First of all, researchers collect 84 kinds of raw milk which is different areas and varieties in Heilongjiang province, and classify 84 samples into calibration sets and validation sets by standard chemical testing and spectral scanning on protein and fat, and calibration sets contain 64 samples, and validation sets contain 20 samples. Then, denoising by second derivative method which window size is 17 points, and selecting method by comparing SPA and GA characteristic wavelength respectively, and establishing PLS model and model demonstration. Eventually, researchers draw the conclusion that SPA wavelength selection method which value of m_max is 10 and GA wavelength selection method which value of Evaluat is 10d can effectively improve validation set model precision, but precision of the former is higher and characteristic wavelength is least, and its characteristic wavelength point reduces from 220 to 4, R2 of protein model validation set is 0.8010929, RMSEP is 0.0207505, R2 of fat model validation set is 0.91007989, RMSEP is 0.045329, relative standard deviation RSD<3%. These prove that the method for rapid testing of raw milk components is feasible.

Assessment of lactation stage and breed effect on sheep milk fatty acid profile and lipid quality indices

Information on fatty acid (FA) profile is critical for the production and promotion of sheep milk and derivative dairy products. The presence of the essential ω-3 and ω-6 FA in milk fat as well as other less common FA, like linoleic acid isomers, has gained an increasing interest due to the consumer demand for a healthy diet. This research assesses the FA profile and estimates the lipid quality indices (ratio between hypocholesterolaemic and hypercholesterolaemic fatty acids, peroxidisability index, atherogenic index, and thrombogenic index) of raw milk and cream fat from two indigenous Greek sheep breeds (Karagouniko and Chios) at different lactation stages. Raw milk and cream fat presented a favorable ω-6/ω-3 ratio below 4:1. Atherogenic and thrombogenic indices of all studied milk fat fluctuated in sufficiently low levels (<3). The FA profile and lipid quality indices in both raw milk and cream samples differed significantly depending more on the lactation stage compared to the breed type. Raw milk fat from late lactation had more beneficial fatty acid profile compared to early and middle lactation stages. Differences among breeds were highlighted when raw milk and cream samples were compared within the same lactation stage. Raw milk and cream fat from Karagouniko breed were characterised by higher ω-3 proportion, lower ω-6/ω-3 ratio and lower thrombogenic index value compared to those from Chios breed.

Changes in Protein Components and Size Distribution of Bovine Milk Fat Globules Caused by Heat Treatment

The effects of heat treatment on the changes in the protein components and size distribution of bovine milk fat globules were investigated. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that some membrane proteins, such as xanthine oxidase and butyrophilin, had disappeared or were weakly stained in the gel due to heating of milk. The volume surface average diameter of raw milk fat globules ranged from 1.15 to 7.42 μm. When the heating temperature was above 90 °C or the heating time was prolonged above 10 min, the average diameters of heated milk fat globules increased significantly (P &lt; 0.05).

Detection of non-milk fat in milk fat by gas chromatography and linear discriminant analysis

Gas chromatography was utilized to determine triacylglycerol profiles in milk and non-milk fat. The values of triacylglycerol were subjected to linear discriminant analysis to detect and quantify non-milk fat in milk fat. Two groups of milk fat were analyzed: A) raw milk fat from the central region of Mexico (n=216) and B) ultrapasteurized milk fat from 3 industries (n=36), as well as pork lard (n=2), bovine tallow (n=2), fish oil (n=2), peanut (n=2), corn (n=2), olive (n=2), and soy (n=2). The samples of raw milk fat were adulterated with non-milk fats in proportions of 0, 5, 10, 15, and 20% to form 5 groups. The first function obtained from the linear discriminant analysis allowed the correct classification of 94.4% of the samples with levels <10% of adulteration. The triacylglycerol values of the ultrapasteurized milk fats were evaluated with the discriminant function, demonstrating that one industry added non-milk fat to its product in 80% of the samples analyzed.

Qualidade do leite de cabra in natura e do produto pasteurizado armazenados por diferentes períodos

QUALITY OF IN NATURA GOAT MILK AND PASTEURIZED PRODUCT STORED FOR DIFFERENT PERIODS. Different periods (0, 3 and 6 days) and 2 temperatures (4 °C and 10 °C) of raw goat’s milk storage and its impact on pasteurized product quality and shelf life were evaluated. In the described periods, slow pasteurization (65 °C/30 min) was carried out and the pasteurized product was stored at 10 °C for 6 days. Raw milk samples were characterized after milk handling and after 3 and 6 days of storage. Pasteurized milk was evaluated immediately after heat treatment and after 3 and 6 days of storage at 10 °C. The counting of mesophiles, total, lipolytic and proteolytic psichotrophic bacteria, total and fecal coliforms, acidity, fat and free fatty acid (FFA) contents were determined. The microorganisms’ populations had a higher growth at 10 °C than 4 °C. Acidity remained in acceptable levels during storage at 4 °C for 6 days, but not at 10 °C. There was a significant decrease (p < 0.05) in raw milk fat content during storage in both temperatures and a gradual increase of free fatty acids (FFA). Pasteurization was efficient in the reduction of bacteria populations and the lipolytic and proteolytic psichrotrophic microorganisms were non-detectable after heat treatment. However, alterations during raw milk storage affected physical-chemical characteristics of pasteurized milk. During storage, values of pasteurized milk acidity and fat content remained stable, while the amount of FFA increased significantly. It was concluded that raw goat’s milk can be stored for up to 3 days at 4 °C before heat treatment. This condition promotes 6 days of shelf-life after pasteurization. In addition, 10 °C is not a suitable

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

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

Apparent ζ-potential as a tool to assess mechanical damages to the milk fat globule membrane

The apparent ζ-potential ( ζ ap) of raw milk fat globules, either natural or mechanically damaged by homogenization or shear, was measured by laser Doppler electrophoresis. Upon homogenization, ζ ap increased in a non-linear way as a function of the surface coverage of the milk fat globule membrane (MFGM) with casein micelles and whey proteins (from −13.5±0.9 mV for natural globules to −20±1 mV for strongly homogenized ones). A model was calculated to estimate the MFGM deteriorations after mechanical stress, using ζ ap measurements. This new method to assess technological damages to raw milk fat globules can be considered as simple when comparing particle size distributions is not possible.

Determination of Fat in Raw Milk: Comparison of Mojonnier (Ether Extraction) and Gerber Method

Results are compared for the approved Gerber method that specifies a TC 11.07 mL pipet and 2 modifications that specify a TC 10.77 mL pipet or a weighed 11.125 g sample of milk rather than a pipetted sample. All results were also compared with results obtained with the Mojonnier method for determining the fat content of raw milk. The standard deviation is somewhat lower for the Mojonnier method than for any of the Gerber methods; among the Gerber methods, the standard deviations were lower for the TC 10.77 mL and 11.125 g modifications. It is recommended that one of these modifications replace the current specified TC 11.07 mL pipet method.

Isolation and composition of milk fat globule membrane material

SummaryThe material surrounding the fat globules in commercial pasteurized homogenized milk was isolated by centrifugation of the freeze – thaw extract of the fat globules through a 52·5% (w/v) sucrose solution in simulated milk ultrafiltrate. The purified membrane material contained higher neutral lipid levels than fresh raw milk fat globule membrane (MFGM) material. Caseins and whey proteins, mainly β-lactoglobulin (β-lg) were found to be the major protein components of homogenized milk membrane material. Native MFGM polypeptides comprised only a small proportion of the total protein in these membranes. The total amount of membrane material isolated from homogenized milk was substantially higher than that from fresh raw milk. Analysis of homogenized milk membrane material by linear sucrose density gradient centrifugation showed a different pattern to that found with other milks, indicating the presence of new lipoprotein complexes. Commercial ultra heat treated (UHT) milks were also examined, but it was difficult to obtain isolated MFGM material free from core fat. However, fat globule fractions were isolated from these products by high speed centrifugation and these were analysed intact. Membrane material in these milks contained caseins and whey proteins (mainly β-1g). Natural MFGM polypeptides were present at extremely low levels. Phospholipid levels in UHT milk membranes were greatly reduced compared with membrane material isolated from other milks.

Gas Liquid Chromatography of Triglyceride in Ice Cream Fat

The distribution of triglycerides constituting various fats and oils was determined by gas liquid chromatography, and it was confirmed that only the distribution of triglycerides in raw milk fat was different from those in other fats and oils.On this finding, the authors devised a criticism to discern whether ice creams contained foreign fats and oils.The evaluation was made that when the distribution of triglycerides constituting ice cream fats was similar to that of milk fat, the ice cream fat did not contain other fats and oils except milk fat. On the other hand, the distribution differing from milk fat, it was suggested that the ice cream fat contained foreign fats and oils. In cases of the latter, quality and quantity of foreign fats and oils added to the ice cream were also estimated.

Collaborative Study of the Babcock and Foss Milko-Tester Methods for Measuring Fat in Raw Milk

Abstract A rapid test for fat content in fluid milk, based on the measurement of light scattered by fat globules, was studied collaboratively. The Milko-tester instrument, developed by Danish scientists, was used. The milk is homogenized to produce uniformsized fat globules and then diluted with a Versene solution which eliminates the turbidity caused by the casein micelle. The amount of dilutant is adjusted so that the values obtained agree with the reference method being used for calibration. In two collaborative trials involving 6 laboratories and 9 samples, and 5 laboratories and 12 samples, respectively, the standard deviations were ±0.069 and ±0.074 for the Milko-tester and Babcock methods, respectively. The corresponding averages for the 21 samples were 4.70 and 4.69%. The standard deviation of difference between Milkotester and Babcock average values for the 21 samples was ±0.045%.

Lactone Precursor in Fresh Milk Fat: Isolation and Characterization of the Precursor

Fresh, raw milk fat was separated into polar and nonpolar glyceride fractions by silicic acid chromatography. The polar fraction contained the lactone precursor. Hydrolysis of this fraction at 140C for 30min resulted in the production of a series of saturated delta lactones of even-numbered chain lengths of from 8 to 18 carbon atoms. Gamma undecalactone was also identified. Presumptive evidence was obtained that the lactone precursor consists of hydroxy triglycerides.