Unhomogenized Milk Research Articles

분광분석법을 이용한 우유의 체세포수 측정기술 개발

The objective of this study was to develop models to predict SCC (somatic cell count) in unhomogenized milk by visible and near-infrared (NIR) spectroscopic technique. Total of 100 milk samples were collected from dairy farms and preserved to minimize propagation of bacteria cells during transportation. Reductive reagents such as methyl red, methylene blue, bromcresol purple, phenol red and resazurin were added to milk samples, and then colors of milk were changed based on SCC of milk. For optimal reductive reagents, reaction time was controlled at 3 level of reaction time. A spectrophotometer was used to measure reflectance spectra from milk samples. The partial least square (PLS) models were developed to predict SCC of unhomogenized milk. The PLS results showed that milk samples with reductive reagents had a good correlation between predicted and measured SCC at 5 minutes of reaction time in the visible range. The PLS models with resazurin reagent had the best performance in . The prediction results of milk samples with resazurin had 0.86 of correlation coefficient and 14,184 cell/mL of SEP.

Near-infrared spectroscopic sensing system for on-line milk quality assessment in a milking robot

A near-infrared (NIR) spectroscopic sensing system was constructed on an experimental basis. This system enabled NIR spectra of raw milk to be obtained in an automatic milking system (milking robot system) over a wavelength range of 600–1050 nm. Calibration models for determining three major milk constituents (fat, protein and lactose), somatic cell count (SCC) and milk urea nitrogen (MUN) of unhomogenized milk were developed, and the precision and accuracy of the models were validated. The coefficient of determination ( r 2) and standard error of prediction (SEP) of the validation set for fat were 0.95 and 0.25%, respectively. The values of r 2 and SEP for lactose were 0.83 and 0.26%, those for protein were 0.72 and 0.15%, those for SCC were 0.68 and 0.28 log SCC/mL, and those for MUN were 0.53 and 1.50 mg/dL, respectively. These results indicate that the NIR spectroscopic system can be used to assess milk quality in real-time in an automatic milking system. The system can provide dairy farmers with information on milk quality and physiological condition of an individual cow and, therefore, give them feedback control for optimizing dairy farm management. By using the system, dairy farmers will be able to produce high-quality milk and precision dairy farming will be realized.

Near-infrared spectroscopic sensing system for online monitoring of milk quality during milking

There has been a need in recent years for a method that will enable dairy farmers to monitor milk quality of individual cow during milking. We constructed a near-infrared (NIR) spectroscopic sensing system for online monitoring of milk quality on an experimental basis. This system enables NIR spectra of unhomogenized milk to be obtained during milking over a wavelength range of 600–1050 nm. We developed calibration models for predicting three major milk constituents (fat, protein and lactose), somatic cell count (SCC) and milk urea nitrogen (MUN) of unhomogenized milk, and we validated the precision and accuracy of the models. The coefficient of determination (r 2) and standard error of prediction (SEP) of the validation set were obtained: for fat, r 2 = 0.95, SEP = 0.42%; for protein, r 2 = 0.91, SEP = 0.09%; for lactose, r 2 = 0.94, SEP = 0.05%; for SCC, r 2 = 0.82, SEP = 0.27 log SCC/mL; and for MUN, r 2 = 0.90, SEP = 1.33 mg/dL, respectively. These results indicated that the NIR spectroscopic sensing system developed in this study could be used to monitor milk quality in real-time during milking. The system can provide dairy farmers with information on milk quality and physiological condition of each cow and therefore give them feedback control for producing milk of high quality and for optimizing dairy farm management.

The effect of ultra high-pressure homogenization (UHPH) on rennet coagulation properties of unheated and heated fresh skimmed milk

The effect of ultra-high pressure homogenization at a pressure of 179 MPa on the renneting of milk has been studied. The homogenization has a small effect on the diameters of casein micelles, because of the loss of some of their surface κ-casein. This modification of the structure leads to a slightly decreased rennet coagulation time. Interactions between the casein micelles in homogenized and unhomogenized milk samples started at a degree of proteolysis of the κ-casein of about 65–70%, although aggregation of the micelles did not start until over 90% proteolysis. Homogenization improved the coagulation properties of heated milk only slightly; however, it was shown that the removal of stabilizing repulsions between the casein micelles in the heated milk seemed to proceed in the same way as in unheated milk. The removal of the κ-casein has the same effect in heated and unheated milk samples, and the casein micelles are destabilized; it is only in the final aggregation step that the two milks differ.

Animal cognition

Animal cognition

Milk-quality monitoring by near-infrared spectroscopy for artificial intelligence in dairy farming

Abstract A near-infrared (NIR) spectroscopic sensing system was constructed on an experimental basis. This system enables NIR spectra of unhomogenized milk to be obtained during milking over a wavelength range of 600 to 1050 nm. The NIR system can be used forreal-time monitoring of fat, protein, lactose, somatic cell count, and milk urea nitrogen during milking with sufficient precision and accuracy. By using this NI Rsystem, dairy farm management could proceed to the next step in the transition to artificial intelligence in dairy farming based on information of each individual cow.

Determination of Fat, Protein, Casein, Total Solids, and Somatic Cell Count in Goat's Milk by Near-Infrared Reflectance Spectroscopy

Analysis using near-infrared reflectance spectroscopy (NIRS) was investigated as a means of predicting quality parameters of goat's milk. Calibration equations were developed with samples from individual goats of Malagueña and Murciano-Granadina dairy breeds at different stages of lactation to obtain a wide range of variation in milk composition. Prediction equations for milk fat, protein, casein, total solids, and somatic cell count (SCC) were developed with 2 sample presentations, liquid drawer (homogenized milk) and aluminium cup (unhomogenized milk), to measure absorbance values, and accuracy of measurements was compared. The multiple correlation coefficient (R) values for homogenized milk were 0.98, 0.96, 0.91, 0.94, and 0.79 and for unhomogenized milk were 0.98, 0.95, 0.92, 0.95, and 0.74 for fat, protein, casein, total solid, and SCC, respectively. To validate the calibrations, an independent set of samples was used. The best simple correlation coefficient (r) values were 0.97, 0.95, 0.91, 0.93, and 0.72 for homogenized milk and 0.97, 0.95, 0.92, 0.95, and 0.79 for unhomogenized milk. The study showed that NIRS is a useful technique for the prediction of fat, protein, casein, total solids, and SCC in unhomogenized goat's milk.

Effect of commercial-scale high-temperature, short-time pasteurization on the viability of Mycobacterium paratuberculosis in naturally infected cows' milk.

Raw cows' milk naturally infected with Mycobacterium paratuberculosis was pasteurized with an APV HXP commercial-scale pasteurizer (capacity 2,000 liters/h) on 12 separate occasions. On each processing occasion, milk was subjected to four different pasteurization treatments, viz., 73 degrees C for 15 s or 25 s with and without prior homogenization (2,500 lb/in(2) in two stages), in an APV Manton Gaulin KF6 homogenizer. Raw and pasteurized milk samples were tested for M. paratuberculosis by immunomagnetic separation (IMS)-PCR (to detect the presence of bacteria) and culture after decontamination with 0.75% (wt/vol) cetylpyridinium chloride for 5 h (to confirm bacterial viability). On 10 of the 12 processing occasions, M. paratuberculosis was detectable by IMS-PCR, culture, or both in either raw or pasteurized milk. Overall, viable M. paratuberculosis was cultured from 4 (6.7%) of 60 raw and 10 (6.9%) of 144 pasteurized milk samples. On one processing day, in particular, M. paratuberculosis appeared to have been present in greater abundance in the source raw milk (evidenced by more culture positives and stronger PCR signals), and on this occasion, surviving M. paratuberculosis bacteria were isolated from milk processed by all four heat treatments, i.e., 73 degrees C for 15 and 25 s with and without prior homogenization. On one other occasion, surviving M. paratuberculosis bacteria were isolated from an unhomogenized milk sample that had been heat treated at 73 degrees C for 25 s. Results suggested that homogenization increases the lethality of subsequent heat treatment to some extent with respect to M. paratuberculosis, but the extended 25-s holding time at 73 degrees C was found to be no more effective at killing M. paratuberculosis than the standard 15-s holding time. This study provides clear evidence that M. paratuberculosis bacteria in naturally infected milk are capable of surviving commercial high-temperature, short-time pasteurization if they are present in raw milk in sufficient numbers.

Calibration of somatic cell count in milk based on near-infrared spectroscopy

A PLS model for prediction of somatic cell count (SCC) based on near-infrared (NIR) spectra of unhomogenized milk is presented in the study. Samples of raw milk were collected from cows in the early lactation period (from 7th to 29th day after parturition). The NIR spectra were measured in the region 400–1100 nm. As reference method a fluoro-opto-electronic method was applied. Different preprocessing methods were investigated. The robust version of PLS regression was applied to handle outliers present in the dataset and the uninformative variable elimination–partial least squares (UVE–PLS) method was used to eliminate uninformative variables. The final model is acceptable for prediction of SCC in raw milk.

No difference in symptoms and receptor expression in lactose-intolerant and in milk-hypersensitive subjects following intake of homogenized and unhomogenized milk

Abstract Theoretically, unhomogenized milk compared to homogenized milk may be better tolerated by milk-hypersensitive subjects due to different distribution of protein particles in fat droplets. We studied whether symptoms and complement receptor expression are different following unhomogenized milk, homogenized milk or milk-free drink in milk-hypersensitive, lactose-intolerant and healthy subjects. In a randomized, double-blind, cross-over study, lactose-intolerant subjects (n=6), milk-hypersensitive subjects with immune-mediated reactions and mainly abdominal symptoms (n=8) and control subjects (n=8) were challenged with homogenized milk, unhomogenized milk and milk-free placebo drink. Each challenge period took 3 days. Subjects recorded their symptoms, and complement receptor expressions (CR1 and CR3) were measured before and after the challenges using flow cytometry. No statistical differences were observed in either the symptoms or receptor expression between challenge periods in any of the groups. It is unlike that homogenization of milk is a major factor determining abdominal reactions in lactose-intolerant and in milk-hypersensitive subjects.

Near-Infrared Spectroscopy for Dairy Management: Measurement of Unhomogenized Milk Composition

The potential of near-infrared spectroscopy to measure fat, total protein, and lactose contents of unhomogenized milk was studied for use in dairy management, as a new tool for on-line milk analysis in the process of milking. Influence of the spectral region, sample thickness, and spectral data treatment on the accuracy of determination was investigated.Transmittance spectra of 258 milk samples, collected at different stages of the milking process, were obtained with a spectrophotometer (NIRSystems 6500; FOSSNIRSystems, Silver Spring, MD) in the wavelength range from 400 to 2500nm with sample thicknesses of 1mm, 4mm, and 10mm.The spectral region and sample thickness were found to be significant factors for milk fat and total protein determination but not the lactose determination. The best accuracy was obtained with the 1100 to 2400nm region, 1-mm sample thickness, and the first derivative data transformation. For the spectral region from 700 to 1100nm, close accuracy was obtained for fat with a 10-mm sample and for total protein with a 1-mm sample thickness. The sample thickness did not change signifi- cantly the accuracy of lactose determination. Different treatments of spectral data did not improve the calibrations for fat and protein.For the region from 700 to 1100nm, where inexpensive on-line sensors could be used, the highest positive coefficients for fat were at 930, 968, 990, 1026, 1076, and 1092nm; for lactose were at 734, 750, 786, 812, 908, 974, 982, and 1064nm; and for total protein were at 776, 880, 902, 952, and 1034nm.

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.

Determination of Fat, Protein, and Total Solids in Ovine Milk by Near-Infrared Spectroscopy

Analysis by near-infrared spectroscopy (NIRS) was investigated as a means of predicting quality parameters of ovine milk. Calibration equations were developed with samples of ovine milk obtained from a flock of Manchega and Lacaune dairy ewes at different stages of lactation for a wide variation in milk composition. Prediction equations for milk protein, fat, and total solids content were developed by use of reflection or transflection methods to measure absorbance values. Accuracies of measurements were compared. R2 (squared multiple correlation coefficient) values were satisfactory in most cases. The highest R2 value for milk protein content (0.92) was obtained in transflectance mode with unhomogenized milk. The highest R2 values for fat (0.99) and total solids (0.98-0.96) content were obtained in both a transflectance mode without sample conditioning and in a transflectance mode with milk homogenized at 40 degrees C. To validate the calibration, an independent set of 40 milk samples was used. The best r2 (simple correlation coefficient) values for protein, fat, and total solids were 0.92, 0.97, and 0.92, respectively. The study showed that NIRS is a potentially useful technique for evaluating the composition of unhomogenized ovine milk.

Effect of the Modification of Fat Particle Size by Homogenization on Composition, Proteolysis, Functionality, and Appearance of Reduced Fat Mozzarella Cheese

The effect of the homogenization of milk (0.8% fat) and cream (20% fat) on cheese-making performance, composition, proteolysis, functionality, and appearance of reduced fat Mozzarella cheese was determined. Three vats (230kg of milk per vat) of cheese were made in 1 d using unhomogenized milk (control), homogenized milk, and milk standardized with homogenized cream. Cheese manufacture was repeated on 3 different d using a randomized complete block design. The homogenized milk treatment had a large amount of curd shattering during cheese manufacture, but the control and the homogenized cream treatments did not. The chemical composition of all cheeses was similar, although the moisture contents of the cheese made from the homogenized products tended to be higher. Homogenization of the milk or cream did not have a large effect on unmelted textural properties of the cheese at 10°C. All cheeses had limited free oil release and melt and excessive browning during pizza baking. Homogenization of the milk increased the nitrogen that was soluble at pH 4.6 in the cheese but did not make this cheese more meltable. The most significant difference between treatments was the appearance of the unmelted cheese. Hunter L values and visual appearance indicated that the cheeses made from homogenized milk or cream were significantly whiter and more opaque than the control. Homogenization significantly improved the appearance of unmelted reduced fat Mozzarella cheese; however, because of improved cheese-making performance, homogenization is recommended of only the cream portion.

Effect of Fat Replacer (Salatrim®) on Chemical Composition, Proteolysis, Functionality, Appearance, and Yield of Reduced Fat Mozzarella Cheese

A no brine, stirred-curd procedure was used to manufacture reduced fat (9% fat wet basis) Mozzarella cheese. Skim milk was standardized to 0.8% fat with unhomogenized milk fat (control), an equal blend of fat replacer Salatrim® types 1 and 3 (Pfizer, Inc., Milwaukee, WI) (solid at room temperature), and 100% Salatrim® type 3 (liquid at room temperature). A stable dispersion (20% fat, wt/wt) was made by homogenizing Salatrim® in skim milk. Cheese making was repeated on each of 3 d using a randomized complete block design. All cheeses had similar pH, salt contents, and calcium contents; cheese made with Salatrim® had higher moisture and fat, but lower protein contents. Nitrogen that was soluble at pH 4.6 was higher for Salatrim® cheeses and increased for all cheeses during refrigerated storage. The meltability and apparent viscosity of all cheeses were similar, but the control had a significantly higher score for hardness and more free oil release, and cheese shreds scorched less during pizza baking. Hunter L, a, and b values of the unmelted cheese indicated that the Salatrim® cheeses were whiter and less yellow than the control, and all cheese decreased in whiteness over time. Salatrim® cheeses had significantly lower fat losses in the whey and stretching water and had higher actual and moisture-adjusted yields. Homogenization was probably responsible for the differences between the control and Salatrim® cheeses in chemical composition, proteolysis, functionality, appearance, and yield. Despite the large differences in fat properties, Salatrim® was probably responsible only for the lack of yellowness in cheese color.

Infrared Analysis of Milk: Effect of Homogenizer and Optical Filter Selection on Apparent Homogenization Efficiency and Repeatability

Abstract The apparent homogenization efficiency (AHE) and repeatability of one instrument was measured with 5 instrument homogenizers that differ in true homogenization efficiency (THE) to determine if instrument characteristics change when different fat A and B optical filters are used in the same machine. Inefficient homogenizers demonstrated both poor repeatability and poor AHE with both sets of fat B filters. One set of fat A filters produced infrared readings that were influenced less by differences in homogenization efficiencies than the other set. The most inefficient homogenizer demonstrated poor repeatability and failed AHE evaluation with both pairs of fat B filters and one pair of fat A filters. Differences in the transmission characteristics of the 2 sets of fat A filters influenced results of AHE evaluation for the most inefficient homogenizers. However, a very efficient homogenizer passed evaluation of AHE and demonstrated good repeatability on both unhomogenized and homogenized milks regardless of differences in the spectral characteristics of filters. A second objective was to determine if AHE test values are correlated with true differences in milk fat globule (MFG) size distribution. A good correlation was found between AHE and THE data for a group of homogenizers for one reference milk. A weakness of the AHE tesl is that the MFG size distribution of the externally homogenized reference milk may vary from one evaluation to another, resulting in an inconsistent reference point for AHE values. The preferred method of evaluating homogenization efficiency of infrared milk analyzers is analysis of the MFG size distribution resulting from instrument homogenization of unhomogenized milk.

Quantitation and Stability of Fumonisins B1 and B2 in Milk

The well-documented presence of fumonisin mycotoxins B1 and B2 (FB1 and FB2) in corn raises the possibility that these toxins are carried over into the milk of animals fed with contaminated feed. The presence of FB1 and FB2 in milk has not been assessed because of the lack of sensitive analytical techniques for this matrix. Two methods, liquid chromatography (LC) and enzyme-linked immunosorbent assay (ELISA), were adapted for the analysis of milk. The ELISA, produced commercially for screening corn, required no sample preparation and was reproducible but was of low sensitivity [concentration that inhibits color development by 50% (IC50), 1200-1600 ng FB1/mL]. The more sensitive LC method involves serial extraction of milk with methanol-acetone and strong anion exchange followed by derivatization with naphthalene-2,3-dicarboxaldehyde. Recoveries of 50 ng FB1 and FB2/mL from unpasteurized and unhomogenized milk were 84 and 83%, respectively (limit of detection, 5 ng/mL). Recoveries of FB1 from whole homogenized milk (76%) were slightly lower. Heating milk for 30 min at 62 degrees C, to mimic pasteurization, did not significantly reduce FB1 or FB2 recovery, nor did storing milk for 11 days at 4 degrees C. The LC method was applied to 165 samples of milk, only 1 of which was positive. This finding suggests that exposure of humans to FB1 and FB2 from milk is low.

Effect of Infrared Analyzer Homogenization Efficiency on Repeatability of Uncorrected Fat A and Fat B Signals

Poor repeatability by infrared milk analyzers may be caused by inefficient homogenization as a result of light scattering and the Christiansen effect. The objectives of this study were to identify instruments with good and poor homogenization efficiency and to determine if a difference exists in repeatability performance between instruments with good vs poor homogenization efficiency. Unhomogenized and homogenized portions of the same milk were tested 20 times consecutively on 22 instruments. An instrument was considered to have poor homogenization efficiency if the mean difference in the uncorrected signal between unhomogenized and homogenized portions of the same milk was > or = 1.43% of the fat test (i.e., > or = 0.05% at 3.5% fat). Instruments were evaluated for repeatability by calculating the sample standard deviation and the range of the latter 19 uncorrected readings for unhomogenized and homogenized milks. When repeatability was evaluated as a function of homogenization efficiency, there was a significant (p = 0.001) correlation between poor homogenization efficiency and poor repeatability when testing unhomogenized milk but not when testing homogenized milk. Improved homogenizer performance within infrared milk analyzers is needed to improve the repeatability of raw milk testing.

Structural changes in oil-in-water emulsions during the manufacture of ice cream

Ice cream was manufactured on a pilot plant and the product was analysed in terms of droplet size distribution and protein composition of the aqueous phase at three stages of the process: after homogenization, after aging and after freezing-aeration-hardening stages. The components (fat 8% wt, skim milk powder 8% wt, glucose syrup 40 DE 6% wt, sucrose 16.75% wt, stabilizer 0.45% wt) and water were homogenized using a two stage high pressure homogenizer (19 MPa + 3 MPa, 70°C). The fat used was either butteroil or fresh unhomogenized milk cream. After an aging period (4°C, 18 h), ice cream mixes were frozen and aerated using a continuous ice cream freezer (overrun = 100%, outlet temperature = − 4°C), hardened in a blast air hardening tunnel (−40°C, 20 min) and stored (−30°C). Droplet size measurements in homogenized and aged mixes did not show any influence of the type of fat used: fat globule distributions were monomodal with an average surface/volume diameter d 32 ≃ 0.50 μm. For both fats, the aging stage did not affect the initial droplet size distribution. The freezing-aeration-hardening stage led to a partial flocculation of aged mix, the effect being more pronounced in butteroil ice cream than in cream ice cream. Protein analysis carried out on the aqueous phase of butteroil ice cream showed a preferential adsorption of caseins over whey proteins during the homogenization stage. Aging and freezing-aeration-hardening stages gave rise to a partial desorption of the proteins from the surface of fat globules, especially during the freezing-aeration-hardening stage.

Effect of Infrared Analyzer Homogenization Efficiency on Linearity of Uncorrected Fat A and Fat B Signals

The objective of the survey was to determine if poor homogenizer performance causes nonlinear behavior of the uncorrected fat A or fat B signal that is not detected when an instrument's residual nonlinearity is determined by using dilutions of homogenized milk instead of unhomogenized milk. Unhomogenized and homogenized (17238 kPa) portions of the same 6.1% fat milk were tested on 20 instruments to determine homogenization efficiency. Instruments with differences of > or = 0.087% fat between homogenized and unhomogenized portions of the same milk had inefficient homogenization, on the basis of criteria established in a previous study. Four and 12 instruments out of 20 demonstrated inefficient homogenization for the fat A and fat B channels, respectively. Uncorrected signal linearity for the fat channels was evaluated quantitatively by using a series of dilutions of homogenized (17238 kPa) and unhomogenized milks. Most instruments passed the linearity evaluation for dilutions of either homogenized or unhomogenized milk, even though many of the same instruments failed the homogenization efficiency evaluation. Thus, using dilutions of homogenized milk is valid for linearity evaluation of instruments being used for testing unhomogenized milk in the range of fat concentrations used for payment testing.