Fat Content In Raw Milk Research Articles

Melatonin suppresses milk fat synthesis by inhibiting the mTOR signaling pathway via the MT1 receptor in bovine mammary epithelial cells.

Milk fat content is an important criterion for assessing milk quality and is one of the main target traits of dairy cattle breeding. Recent studies have shown the importance of melatonin in regulating lipid metabolism, but the potential effects of melatonin on milk fat synthesis in bovine mammary epithelial cells (BMECs) remain unclear. Here, we showed that melatonin supplementation at 10μmol/L significantly downregulated the mRNA expression of lipid metabolism-related genes and resulted in lower lipid droplet formation and triglyceride accumulation. Moreover, melatonin significantly upregulated melatonin receptor subtype melatonin receptor 1a (MT1) gene expression, and the negative effects of melatonin on milk fat synthesis were reversed by treatment with the nonselective MT1/melatonin receptor subtype melatonin receptor 1b (MT2) antagonist. However, a selective MT2 antagonist did not modify the negative effects of melatonin on milk fat synthesis. In addition, KEGG analysis revealed that melatonin inhibition of milk fat synthesis may occur via the mTOR signaling pathway. Further analysis revealed that melatonin significantly suppressed the activation of the mTOR pathway by restricting the phosphorylation of mTOR, 4E-BP1, and p70S6K, and the inhibition of melatonin on milk fat synthesis was reversed by mTOR activator MHY1485 in BMECs. Furthermore, in vivo experiments in Holstein dairy cows showed that exogenous melatonin significantly decreased milk fat concentration. Our data from in vitro and in vivo studies revealed that melatonin suppresses milk fat synthesis by inhibiting the mTOR signaling pathway via the MT1 receptor in BMECs. These findings lay a foundation to identify a new potential means for melatonin to modulate the fat content of raw milk in Holstein dairy cows.

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.

Influence of Preservative Concentration, pH Value and Fat Content in Raw Milk at Detection Limit of Microbial Inhibitor Tests (Delvotest® Accelerator) for Amoxicillin and Oxytetracycline

The presence of antibiotic residues in raw milk is a big threat not only to the dairy industry but also to public health. Therefore, it is very important to detect antibiotic residues in raw milk. There are many reliable antibiotic test used in dairy laboratories. Unfortunately, some factors can affect the results causing, so-called false-positive results. The aims of this paper are to check the detection limits of microbiological inhibitor test with test organisms Geobacillus stearothermophilus var. calidolactis, which are provided on Delvotest® Accelerator instrument (DSM, The Netherlands) for antibiotics amoxicillin and oxytetracycline and to examine the influence of variations of milk fat contents, pH values and azidiol concentrations in raw milk on detection limits, e.g., test results. The obtained results showed that detection limit for amoxicillin is 3 μg/L and oxytetracycline 250 μg/L; concentration of preservative azidiol of 0.1 mL per 40 mL of milk does not affect the detection limits of the test; microbiological inhibitor test is extremely sensitive to low pH value of samples so, it is recommended to avoid testing milk samples with low pH value, or to adjust the sample’s pH value by addition of some base; and that fat content in raw milk up to 5 % does not affect the detection limit of the methods for amoxicillin and for oxytetracycline.

Visible and near-infrared bulk optical properties of raw milk

The implementation of optical sensor technology to monitor the milk quality on dairy farms and milk processing plants would support the early detection of altering production processes. Basic visible and near-infrared spectroscopy is already widely used to measure the composition of agricultural and food products. However, to obtain maximal performance, the design of such optical sensors should be optimized with regard to the optical properties of the samples to be measured. Therefore, the aim of this study was to determine the visible and near-infrared bulk absorption coefficient, bulk scattering coefficient, and scattering anisotropy spectra for a diverse set of raw milk samples originating from individual cow milkings, representing the milk variability present on dairy farms. Accordingly, this database of bulk optical properties can be used in future simulation studies to efficiently optimize and validate the design of an optical milk quality sensor. In a next step of the current study, the relation between the obtained bulk optical properties and milk quality properties was analyzed in detail. The bulk absorption coefficient spectra were found to mainly contain information on the water, fat, and casein content, whereas the bulk scattering coefficient spectra were found to be primarily influenced by the quantity and the size of the fat globules. Moreover, a strong positive correlation (r≥0.975) was found between the fat content in raw milk and the measured bulk scattering coefficients in the 1,300 to 1,400nm wavelength range. Relative to the bulk scattering coefficient, the variability on the scattering anisotropy factor was found to be limited. This is because the milk scattering anisotropy is nearly independent of the fat globule and casein micelle quantity, while it is mainly determined by the size of the fat globules. As this study shows high correlations between the sample’s bulk optical properties and the milk composition and fat globule size, a sensor that allows for robust separation between the absorption and scattering properties would enable accurate prediction of the raw milk quality parameters.

Milk and dairy product analyses at the Dairy Chemistry Division in Mauritius: an overview

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Effect of freezing on the “creamatocrit” measurement of the lipid content of human donor milk

Abstract Objective To determine, by the creamatocrit measurement, the effect on fat content of freezing raw and pasteurised donor milk at −20 °C for 3 months. Methods The evolution of the creamatocrit measurement (following Lucas technique) on frozen (−20 °C), raw and pasteurised human milk, was analysed during 3 months. Results The fat content of raw milk (n = 44) was 3.19 g/dl at the beginning and 2.86 g/dl after 3 months frozen (p = 0.02). In pasteurised milk (n = 36) fat content at the first determination was 2.59 g/dl and 2.20 g/dl after 1 month frozen (p = 0.01). Afterwards there were no significant changes up to 3 months frozen. Variability was observed in the intermediate values. Conclusions A reduction on the fat content measurement of raw and pasteurised donor human milk after freezing was observed. Freezing does not inactivate the milk lipase but does destroy the fat globule. Creamatocrit measurement may not be the best method to determine the fat content of processed human milk.

Medida por crematocrito del contenido calórico de la leche materna donada congelada

ObjectiveTo determine, by the creamatocrit measurement, the effect on the fat content of raw and pasteurized donor milk of freezing during 3 months at −20 °C. MethodsThe evolution of the creamatocrit measurement (following Lucas technique) on frozen (−20 °C), raw and pasteurized human milk, was analyzed during 3 months. ResultsThe fat content of raw milk (n=44) was 3.19 g/dl at the beginning and 2.86 g/dl after 3 months frozen (p=0.02). In pasteurized milk (n=36) fat content at the first determination was 2.59 g/dl and 2.20 g/dl after 1 month frozen (p=0.01). Afterwards there were no significant changes up to 3 months frozen. Variability was observed in the intermediate values. ConclusionsA reduction on the fat content measurement of raw and pasteurized donor human milk after freezing was observed. Freezing does not inactivate the milk lipase but does destroy the fat globule. Creamatocrit measurement may not be the best method to determine the fat content of processed human milk.

Effect of fat content and homogenization under conventional or ultra-high-pressure conditions on interactions between proteins in rennet curds

The objective of this study was to investigate the influence of conventional and ultra-high-pressure homogenization on interactions between proteins within drained rennet curds. The effect of fat content of milk (0.0, 1.8, or 3.6%) and homogenization treatment on dissociation of proteins by different chemical agents was thus studied. Increasing the fat content of raw milk increased levels of unbound whey proteins and calcium-bonded caseins in curds; in contrast, hydrophobic interactions and hydrogen bonds were inhibited. Both homogenization treatments triggered the incorporation of unbound whey proteins in the curd, and of caseins through ionic bonds involving calcium salts. Conventional homogenization-pasteurization enhanced interactions between caseins through hydrogen bonds and hydrophobic interactions. In contrast, ultra-high-pressure homogenization impaired hydrogen bonding, led to the incorporation of both whey proteins and caseins through hydrophobic interactions and increased the amount of unbound caseins. Thus, both homogenization treatments provoked changes in the protein interactions within rennet curds; however, the nature of the changes depended on the homogenization conditions.

An attempt of applying the electrical properties for the evaluation of milk fat content of raw milk

This manuscript presents outcomes of a study aimed at determining a correlation between milk fat content as the key indicator of raw milk quality and the conductance and capacitance properties of milk.The analysis of correlation and linear regression of fat content (F) in the function of changes in impedance (Z), admittance (Y), parallel equivalent capacitance (Cp) and series equivalent capacitance (Cs) of milk demonstrated that within a frequency range of 100Hz to 100kHz, correlations were observed that could be described with the following equation: y=ax±b. The highest correlations (0.934⩽r⩽0.990; α=0.006 – 0.000) were achieved between fat content of raw milk and values of the parallel equivalent capacitance (Cp). This means that the most accurate determination of fat content (F) of raw milk is feasible through the measurements of Cp and calculations based on mathematical equations, e.g. F=a×Cp+b. The correlations achieved in the measuring voltage frequency range of 100Hz to 100kHz encourage to continue investigations aimed at developing a rapid method for the assessment of fat content of raw milk based on measurements of electric parameters of conductance and capacitance.

Potential of Individual Cow Scatter Correction for an Improved Accuracy of near Infrared Milk Composition Analysis

Near infrared (NIR) spectroscopy has the potential to quickly analyse raw milk composition on the farm. The accurate determination of individual cow's milk composition changes can indicate health imbalances and, hence, support herd management. The accuracy of NIR calibration models are highly influenced by individual cow scatter effects in the NIR spectra based, to a large extent, on individual scattering effects of milk fat globules (MFG). In this study the potential of an individual cow scatter correction was investigated. A total of 1151 milk samples were taken from 12 Holstein cows and used for spectra acquired in the 851–1649 nm wavelength range with a diode array spectrometer. Corresponding milk samples from the composite milkings were used for reference analysis. Individual cow scatter correction factors were developed from raw milk samples and homogenised milk samples. Calibration models based on the partial least squares (PLS)-regression method from corrected and uncorrected spectra were compared with regard to their prediction accuracy of fat (%), protein (%), lactose (%) and urea content (mgL−1) as well as logarithmised somatic cell count (log SCC) in milk. Prediction of fat content in raw milk was excellent both with and without scatter correction. Improved calibration results were obtained particularly for predicting the content of protein, lactose, urea and log SCC in raw milk when calibration models were based on the corrected spectra. Compared to prediction results of the uncorrected dataset, root mean square error was reduced by up to 25%.

Effect of Multiplicative Scatter Correction on Wavelength Selection for near Infrared Calibration to Determine Fat Content in Raw Milk

The effect of multiplicative scatter correction (MSC) on wavelength selection for near infrared (NIR) calibration to determine fat content in raw milk was investigated. Short-wave NIR spectra (700–1100 nm) of raw milk samples were measured. The calibration equations for fat content were performed by multiple linear regression (MLR) using original, second derivative and MSC-treated spectra. It was found that first wavelength selection from the fat absorption band for a calibration equation was generally effective in all cases of original, second derivative and MSC-treated spectra. However, correlation plots did not always work well because of the multiplicative scatter effect presented in the samples. Whereas, correlation plots were still useful in the case of MSC-treated spectra and normalised second derivative spectra, even when the original spectra exhibited a multiplicative scatter effect.

Development of Calibration with Sample Cell Compensation for Determining the Fat Content of Unhomogenised Raw Milk by a Simple near Infrared Transmittance Method

A simple near infrared (NIR) transmittance measuring method for unhomogenised raw milk was developed using test tubes as sample cells and a specially designed sample holder which could control sample temperature. Shortwave NIR spectra (700–1100 nm) of 154 unhomogenised milk samples from eight cows, under different nutritional conditions, were measured at 40°C using this method. The calibration and validation for fat content in raw milk were performed by partial least squares regression in two ways, using either a specific test tube or any individual test tube as a sample cell. A functional calibration model for determining fat content in raw milk with relatively high accuracy (multiple correlation coefficient of 0.99 and SEP of 0.19%) was obtained, which is applicable even when using individual test tubes as sample cells. By examining the loading weight of each factor included in the calibration model for fat determination in milk, it was found that the model consisted of, not only the factor for fat, but also factors which worked as adjusting terms, eliminating any effects caused by the other major components of milk such as lactose, casein and water and by the sample cell.

Performance Evaluation of the Babcock and Ether Extraction Methods: 1989 through 1992

Abstract Results of the collaborative studies of the performance of the Babcock method (989.04) and the modified Mojonnier ether extraction method (989.05) for the determination of the fat content of raw milk were published in 1988. Method performances were characterized by using the harmonized International Organization for Standardization–International Union of Pure and Applied Chemistry–Association of Official Analytical Chemists (ISO/IUPAC/AOAC) guidelines for method validation, and the methods were approved official first action. During 1989 through 1992, the split-sample collaborative study format was used to monitor the performance of these methods as a part of an ongoing quality assurance program for a group of laboratories. Seven blind duplicate samples of raw milk were sent from a central laboratory once every 2 months to each participating laboratory (11 to 17 laboratories). Data were analyzed by using the same statistical procedures used in the 1988 study. Over time, both the within- and between-laboratory performances of both methods were as good as or, in most cases, better than the results from 1988. The data demonstrate that the statistical protocol for collaborative studies can be used effectively as the basis for a multilaboratory quality assurance program and that the method performance achieved in a collaborative study can be maintained and even improved with time.

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.