Milk Protein Fractions Research Articles

Quantitative and qualitative detailed milk protein profiles of 6 cattle breeds: Sources of variation and contribution of protein genetic variants

Different fractions of milk nitrogenous compounds (not only caseins) have different effects on the nutritional value of milk, its coagulation and curd firming properties, and its cheese-making efficiency. To assess different sources of variation, especially the cows' breed and genetic variants of the main protein fractions, milk samples were collected from 1,504 cows belonging to 3 dairy breeds (Holstein-Friesian, Brown Swiss, and Jersey) and 3 dual-purpose breeds (Simmental, Rendena, and Alpine Grey) reared in 41 multibreed herds. Beyond crude protein, casein (CN), and urea, 7 protein fractions were analyzed using HPLC, and 5 other N fraction traits were calculated. All 15 traits were measured qualitatively (% of milk N) and quantitatively (g/L of milk). The HPLC technique allowed us to discriminate between the main genetic variants of β-CN, κ-CN, and β-lactoglobulin and thus to genotype the cows for the CSN2, CSN3, and BLG genes, respectively. Data were analyzed using 2 mixed models, both including the effects of herd-date, breed, parity, and lactation stage, and only one also including the effects of the genotypes of the milk proteins. Breed of cow explained 2 to 36% of phenotypic variability for all the N fractions, with the exception of the urea and total casein contents of milk and the urea and β-CN proportions of total milk N. Lactation stage had a considerable influence on the amount (g/L) of almost all the protein fractions in milk, but neither the nonprotein N fractions nor the percentage of milk N protein profile were affected. The inclusion of the CSN2, CSN3, and BLG genotypes in the model explained a large part of the total variability in all the milk protein and nonprotein fractions except urea. It also reduced the variance explained by breed and residual factors. An exception was shown by the proportion of αS1-CN variance explained by breed that moved from 13 to 28%. Similarly, for amount (g/L) of β-CN, the effect of breed became significant (12%), whereas it was almost null before inclusion of genotypes. In terms of percentage of milk N, the genotypes of CSN3 notably affected all the casein fractions, whereas the BLG genotypes had a much greater influence on most noncasein traits. The genotypes of the CSN2 gene exerted an appreciable effect on αS2-CN and not β-CN, as expected. Comparing the 2 models, we were also able to discriminate the effect of the breed on a milk N fraction, both quantitatively and qualitatively, in 2 quotas: the first due to the milk protein polymorphisms (major genes) and the second due to other genetic factors (polygene), after correcting for the effect of herd-date of sampling, parity, and lactation stage. The knowledge about the detailed milk protein profile of different cattle breeds provided by this study could be of great benefit for the dairy industry, providing new tools for the enhancement of milk payment systems and breeding program designs.

Integration of Wet-Lab Measures, Milk Infrared Spectra, and Genomics to Improve Difficult-to-Measure Traits in Dairy Cattle Populations.

The objective of this study was to evaluate the contribution of Fourier-transformed infrared spectroscopy (FTIR) data for dairy cattle breeding through two different approaches: (i) estimating the genetic parameters for 30 measured milk traits and their FTIR predictions and investigating the additive genetic correlation between them and (ii) evaluating the effectiveness of FTIR-derived phenotyping to replicate a candidate bull’s progeny testing or breeding value prediction at birth. Records were available from 1,123 cows phenotyped using gold standard laboratory methodologies (LAB data). This included phenotypes related to fine milk composition and milk technological characteristics, milk acidity, and milk protein fractions. The dataset used to generate FTIR predictions comprised 729,202 test-day records from 51,059 Brown Swiss cows (FIELD data). A first approach consisted of estimating genetic parameters for phenotypes available from LAB and FIELD datasets. To do so, a set of bivariate animal models were run, and genetic correlations between LAB and FIELD phenotypes were estimated using FIELD information obtained at the population level. Heritability estimates were generally higher for FIELD predictions than for the corresponding LAB measures. The additive genetic correlations (ra) between LAB and FIELD phenotypes had different magnitudes across traits but were generally strong. Overall, these results demonstrated the potential of using FIELD information as indicator traits for the indirect genetic improvement of LAB measures. In the second approach, we included genotype information for 1,011 cows from the LAB dataset, 1,493 cows from the FIELD dataset, 181 sires with daughters in both LAB and FIELD datasets, and 540 sires with daughters in the FIELD dataset only. Predictions were obtained using the single-step GBLUP method. A four fold cross-validation was used to assess the predictive ability of the different models, assessed as the ability to predict masked LAB records from daughters of progeny testing bulls. The correlation between observed and predicted LAB measures in validation was averaged over the four training-validation sets. Different sets of phenotypic information were used sequentially in cross-validation schemes: (i) LAB cows from the training set; (ii) FIELD cows from the training set; and (iii) FIELD cows from the validation set. Models that included FIELD records showed an improvement for the majority of traits. This study suggests that breeding programs for difficult-to-measure traits could be implemented using FTIR information. While these programs should use progeny testing, acceptable values of accuracy can be achieved also for bulls without phenotyped progeny. Robust calibration equations are, deemed as essential.

Simulating the ultrafiltration of whey proteins isolate using a mixture model

Ultrafiltration (UF) is widely used in the fractionation and concentration of milk proteins. During this process, proteins concentrate at the membrane surface, increasing the resistance of the membrane system, and decreasing permeate flux leaving the process unit. In this study we use Computational Fluid Dynamics (CFD) to examine the UF of whey proteins. Specifically we employ a multiphase mixture model to predict the solid concentration and velocity distributions near the membrane, under both dead-end and crossflow modes. As whey proteins have a fairly compact globular structure we use hard sphere theory to model the suspension permeability and osmotic pressure: Notably these properties depend only on parameters that can be independently measured, such as protein size and concentration. Model predictions are found to be in good agreement with experimental flux data for both flow modes, significantly in the absence of any additional resistance models representing (for example) pore blockage, surface adsorption or gel/cake formation. We find that during dead-end filtration, the extent of flux decline is logically dependent on the concentration film thickness and maximum solids concentration attained at the membrane surface. Under crossflow conditions suspension advection from the bulk towards the membrane increases the permeate flux, particularly along any upstream membrane area edges. Simulating the system using simplified 2D geometries produces qualitative, rather than quantitative agreement with experiment, highlighting the need to capture the system geometry accurately when modelling concentration polarisation (CP) effects. This work shows that industrially relevant whey protein filtration can be predicted via the multiphase modelling of hard sphere suspensions, using as-measured particle sizes, and points to more accurate methods for optimising and designing whey UF systems.

Spectroscopic studies of the interaction between isolated polyphenols from coffee and the milk proteins

In this work, the binding of polyphenols isolated from coffee (PIC) with milk protein fractions was investigated by using different spectroscopic techniques as Fourier Transform Infrared Spectroscopic technique, high-performance liquid chromatography, and fluorescence quenching emission method. The polyphenols fraction was isolated from coffee powder using a chromatographic column packed with lipophilic Sephadex LH-20 gel, while there are different types of milk proteins skim milk 3% protein (SM), acid casein (β-Casein (β-CN), α-Casein (α-CN), κ-Casein (κ-CN)), and whey protein isolate (WPI) (β-lactoglubulin (β-Lg) and α-lactalbumin (α-La)) were investigated. From our study, the optimum pH for precipitating complex from the interaction of polyphenols with milk proteins, WPI, acid casein was 5, 8, and 7, respectively. Also, the fluorescence quenching method for polyphenols-proteins interaction exhibited fluorescence quenching in the descending order of α-CN > β-Lg > SM3% > WPI > α-La > acid casein > β-CN > κ-CN for milk proteins. Furthermore, vibrational absorption mode of the functional groups confirmed of the appearing the polyphenols-proteins interaction. Besides, the percentage of interaction between milk protein fractions with PIC was mentioned using HPLC technique.

Impact of ultrasound processing on some milk-borne microorganisms and the components of camel milk

Inactivation of pathogenic bacteria Escherichia coli O157: H7 and Salmonella Typhimurium in camel milk was investigated using ultrasound processing (900 W, 20 kHz, 100% power level). In addition, the effect of ultrasound treatment on raw camel milk components was studied to detect changes in fatty acid profile, lipid peroxides, protein fractions, and volatile compounds. Bacterial strains (106 CFU/ml) were added to pasteurized camel milk samples (70 ml) and transferred into a sterile aluminum container (30 mm x 120 mm, 100-ml total capacity) and then subjected to continuous ultrasound processing for 15 min in an ice water bath using a 13-mm diameter probe. The standard plate count (SPC) agar method and the in vivo imaging system (IVIS) were used to evaluate the viability of bioluminescence-transformed bacteria (E. coli O157: H7 and S. Typhimurium). The continuous ultrasound processing of camel milk resulted in significant (P<0.05) reductions in S. Typhimurium and E. coli O157: H7. Relative to unsonicated raw camel milk, the cis-9, trans-11 conjugated linoleic acid (CLA) and trans-10, cis-12 CLA contents were not affected (P>0.05) by the ultrasound processing. The TBAR values, a marker of lipid peroxidation, and milk protein fractions were also similar (P>0.05) between the sonicated and unsonicated raw camel milk. A total of 24 volatile compounds (VC) were identified including 8 aldehydes, 3 ketones, 5 acids, 5 esters, 2 aromatic hydrocarbonate, and 1 sulfo compound. Of these 24 VC, eleven VC increased (P<0.05) and seven decreased (P<0.05) after sonication. In conclusion, the results of this study showed that ultrasound processing of camel milk was efficient in inactivating subsets of milk-borne pathogens without detrimental effects on camel milk fatty acids, lipid peroxides, and protein fractions. However, there were some changes in milk VC which may affect the sensory quality of milk.

Effect of low-frequency pulsatile crossflow microfiltration on flux and protein transmission in milk protein fractionation

ABSTRACT Pulsatile crossflow has often been suggested as a fouling mitigation concept for microfiltration. Besides beneficial effects regarding flux in the filtration of model suspensions, little is known about the effects on the fractionation efficiency when separating proteins in complex multi-component systems. Therefore, this study focusses on the impact of low-frequency pulsatile crossflow on fractionation efficiency during microfiltration of skimmed milk. We found a relaxation of the deposited casein layer during low-crossflow and thus low-transmembrane pressure phases. However, during high-crossflow and high-transmembrane pressure phases, the deposit layer is rapidly re-compressed. The results indicate that, due to this cyclic stress, the overall packing of the deposit layer increases over time and impairs the separation efficiency.

Milk protein fractionation by custom-made prototypes of spiral-wound microfiltration membranes operated at extreme crossflow velocities

Compared to tubular membranes, spiral-wound membranes (SWM) cannot be operated at very high crossflow velocities due to mechanical instabilities of the module. We therefore applied a novel approach using custom-made microfiltration SWM modules to study the effects of crossflow velocities beyond the level currently applicable for commercial SWM. First, we used a modified industrial SWM (0.96 m) to measure flux and protein permeation spatially resolved within the limits of crossflow conditions applied in routine operation (maximum ΔpL of 1.3 bar). Secondly, we applied a short SWM (0.24 m) to assess the effect of extreme crossflow velocities with a corresponding ΔpL of up to 2.8 bar m−1. The goal was to investigate the effects of deposit formation reduced to the minimum, and thus, to measure the theoretically achievable improvement of flux and protein permeation even though this is currently not practicable. As key result, we found a critical crossflow velocity up to which a significant increase of protein mass flow could be achieved; beyond which, however, no further reduction in filtration resistance caused by deposit formation was observed. The filtration became independent of the transmembrane pressure. Based on these findings, more rigid modules could potentially improve the performance of SWM.

Structural Characterisation of Deposit Layer during Milk Protein Microfiltration by Means of In-Situ MRI and Compositional Analysis.

Milk protein fractionation by microfiltration membranes is an established but still growing field in dairy technology. Even under cross-flow conditions, this filtration process is impaired by the formation of a deposit by the retained protein fraction, mainly casein micelles. Due to deposition formation and consequently increased overall filtration resistance, the mass flow of the smaller whey protein fraction declines within the first few minutes of filtration. Currently, there are only a handful of analytical techniques available for the direct observation of deposit formation with opaque feed media and membranes. Here, we report on the ongoing development of a non-invasive and non-destructive method based on magnetic resonance imaging (MRI), and its application to characterise deposit layer formation during milk protein fractionation in ceramic hollow fibre membranes as a function of filtration pressure and temperature, temporally and spatially resolved. In addition, the chemical composition of the deposit was analysed by reversed phase high pressure liquid chromatography (RP-HPLC). We correlate the structural information gained by in-situ MRI with the protein amount and composition of the deposit layer obtained by RP-HPLC. We show that the combination of in-situ MRI and chemical analysis by RP-HPLC has the potential to allow for a better scientific understanding of the pressure and temperature dependence of deposit layer formation.

INFLUENCE OF ORIGIN ON MILK PRODUCTIVITY AND REPRODUCTIVE PROPERTIES OF SYCHEVSKAYA BREED COWS

The results of researches on studying of sires influence on milk production and reproductive properties of Sychevskaya breed cows, bred in the breeding farm, JSC "Vostok", Smolensk region. In order to determine sires, cows, which are able to increase milk productivity of the herd without compromising reproductive properties, population of full-aged cows, according to their origin, was divided into six groups. Their milk yield was analyzed for first and third lactations, mass fraction of milk fat and milk protein, live weight, coefficients of milk yield of cows and the sustainability of lactation. The most stable, in all groups, is the first lactation, then there is a decrease to the fifth lactation. Cows received from the bull of Sychevskaya breed Pyl 6782, for the first lactation have a productive advantage over livestock received from other bulls. In full-aged animals derived from this bull, this advantage is lost. The daughters Hanke 6749, Holstein red-and-motley breed, have intensively promoting milk productivity, indicators of milk fat and protein is higher in daughters of Holstein bull Marder 6721. Reproductive properties were studied: open days and calving interval, age at first calving, days to first fertilization in lactation. The best reproductive properties have Sychev bulls. After calving, reproductive function in daughters Naliv 6791(sychevskaya breed) were restored earlier, in daughters Hanke 6749 - for longer period. The correlation of signs is defined: milk yield between lactations, milk productivity with mass fraction offat%, live weight, age of the first calving, the period of days before the first insemination in lactation.

Genomic Analysis of Milk Protein Fractions in Brown Swiss Cattle

Simple SummaryMilk protein fractions are hugely important in the dairy industry because of the key role they play in milk technological properties. The selection of cows for milk protein fractions may, therefore, improve both the nutritional and technological characteristics of milk, and, consequently, the processing efficiency and value of the dairy product. This study estimated the genetic parameters of the major milk protein fractions (four caseins, and two whey proteins) determined variously as: (i) milk content (g/100g milk), (ii) percentage of milk nitrogen (%N) and (iii) daily yield (g/d) in Brown Swiss dairy cattle. The results showed that the (co)variances and genetic parameter estimates differed according to how the proteins were measured. These results provide useful information for developing selection strategies in dairy cattle breeding programs aimed at improving both the nutritional and technological properties of milk.Depending on whether milk protein fractions are evaluated qualitatively or quantitatively, different genetic outcomes may emerge. In this study, we compared the genetic parameters for the major milk protein fractions—caseins (αS1-, αS2-, β-, and к-CN), and whey proteins (β-lactoglobulin, β-LG; α-lactalbumin, α-LA)—estimated using the multi-trait genomic best linear unbiased prediction method and expressed variously as milk content (g/100g milk), percentage of milk nitrogen (%N) and daily yield per cow (g/d). The results showed that the genetic parameter estimates varied according to how the milk protein fractions were expressed. Heritability estimates for the caseins and whey protein fractions expressed as daily yields were lower than when they were expressed as proportions and contents, revealing important differences in genetic outcomes. The proportion and the content of β-CN were negatively correlated with the proportions and contents of αS1-CN, αS2-CN, and к-CN, while the daily yield of β–CN was negatively correlated with the daily yields of αS1-CN and αS2-CN. The Spearman’s rank correlations and the coincidence rates between the various predicted genomic breeding values (GEBV) for the milk protein fractions expressed in different ways indicated that these differences had a significant effect on the ranking of the animals. The results suggest that the way milk protein fractions are expressed has implications for breeding programs aimed at improving milk nutritional and technological characteristics.

Milk protein fractionation by spiral-wound microfiltration membranes in diafiltration mode - Influence of feed protein concentration and composition on the filtration performance

Washing steps by adding diafiltration medium are needed to completely fractionate caseins and whey proteins from skim milk by microfiltration. The amount of diafiltration medium and the fractionation performance depend on the feed concentration factor (CF). However, an investigation on the optimum process conditions during fractionation by spiral-wound membranes (SWMs) has not been carried out yet. At the optimum transmembrane pressure, CF 2 performed best with regard to the whey protein mass flow. The protein concentration in the permeate and the flux were limiting factors at lower and higher CFs, respectively. Regarding industrial plants with multiple stages for the fractionation, the casein to whey protein ratio varies in each stage. Since no changes in the length-dependent filtration behaviour was observable with the casein to whey protein ratio at a constant axial pressure drop, the optimisation of SWMs regarding length dependency can be conducted independently of the stage.

Subclinical Mastitis Survey on Milk Composition in Dairy Sheep in Kurdistan Region of Iraq

Mastitis is an inflammatory condition of the mammary gland, characterized by the changes in the physical characteristics of the udder or milk. A cross sectional study was carried out in June, 2017 to December, 2018 to estimate the effect of subclinical mastitis (SCM) on milk composition in dairy sheeps in Kafri city of Kurdistan region of Iraq. Milk samples were gathered from residences of 295 sheeps with subclinical mastitis (California mastitis test (CMT) positive and somatic cell counts (SCC) >600,000 cells/ml in individual quarter foremilk), as well as from 50 healthy controls. Contrasted to the levels watched in milk from healthy quarters, milk from quarters with subclinical mastitis exhibited raised high chloride (>0.12 in contrast with <0.12 g/dl), pH (5.65 in comparison to 5.57), sodium (86.87 vs 47.81 mg/dl), albumin (4.52 in contrast with 1.75 g/dl), immunoglobulins (24.66% in comparison to 5.73%) and lactate dehydrogenase (LDH) activity (1344.14 vs 449.84 IU/L). In compare, reduced values were discovered for potassium (147.47 in comparison to 161.34 mg/dl), inorganic phosphorous (19.42 in comparison to 26.48 mg/dl), calcium (86.35 vs 121.12 mg/dl), β-lactoglobulin (30.22% in comparison to 52.18%) and α- lactalbumin (19.15% vs 24.52%). In this study, no changes were seen in blood serum LDH activity. Moreover, an increase in positive response to CMT was found to be accompanied by an almost proportionate increase in immunoglobulin values to 44.32% and reduce of α-lactalbumin levels in milk serum (p<0.01). These alterations in LDH activity, pH, mineral concentrations and protein fractions in milk of quarters display the presence of tissue injury provoked by SCM. Therefore, these parameters can be used in the diagnosis of mastitis. The current study revealed that changes of the foremilk chemical composition are connected to the subclinical mastitis; and that mastitis progression of quarters (CMT scores) influenced protein fractions in milk.

Effects of somatic cell score on milk yield and mid-infrared predicted composition and technological traits of Brown Swiss, Holstein Friesian, and Simmental cattle breeds

High milk somatic cell count (SCC) influences milk production and quality; however, very little is known about the effect of low SCC on milk quality, especially in terms of mineral content and coagulation properties. Thus, the present study aimed to investigate the effects of somatic cell score (SCS), calculated as log2(SCC/100) + 3, on milk yield, composition (fat, crude protein, casein, lactose, milk urea nitrogen, protein fractions, and mineral contents), and coagulation properties of Brown Swiss, Holstein Friesian, and Simmental cows from multibreed herds. Milk composition and coagulation traits were predicted using mid-infrared spectroscopy. The data set comprised 95,591 observations of 6,940 cows in 313 multibreed herds, collected from January 2011 to December 2017. Observations were divided into 8 classes based on SCS. Statistical analysis was performed using a linear mixed model, which included breed, parity, stage of lactation, SCS class, and their interactions as fixed effects, and herd test day, cow, and residual as random effects. The probability that cows experienced SCS > 4.00 at 30 ± 5, 60 ± 5, or 90 ± 5 d after the observation test day was calculated for each SCS class, and odds ratios to the reference class (-1.00 < SCS ≤ 0.00) were reported. Results showed that the relationship between SCS and milk traits followed a third-order polynomial regression. The average loss of milk, fat, and crude protein yields were 0.43, 0.01, and 0.01 kg/d, respectively, for each SCS unit higher than 1.00. Very low SCS (<-1.00) had detrimental effects on milk yield and quality traits similar to or even stronger than high SCS (>4.00). Moreover, cows with SCS lower than -1.00 on a test day were about 7 times more likely to present high SCS within the following 90 ± 5 d than cows with SCS between -1.00 and 0.00. Breeds responded similarly to the increase of SCS, but the overall loss of fat and crude protein yields, and several minerals among Holstein Friesian were lower with increasing SCS. The best milk yield and quality were observed between SCS 0.00 and 1.00, but milk quality of Holstein Friesians started to decrease at lower SCS compared with milk quality of Brown Swiss and Simmental cows. Results suggest a breed-dependent optimum of SCS, and highlighted that very low SCS can be an indicator of udder health problems and, thus, may be used for early detection of mastitis.

Milk protein polymorphism in Amiata donkey

Interest in donkey milk for human nutrition has been growing steadily, especially in the therapeutic-diet field, due to its similarity to human milk. Caseins are one of the main allergenic components of milk. Whereas cow milk has a high casein content, in donkey milk the casein concentration is lower and is characterized by a greater digestibility. In fact, recent studies have shown that donkey milk can be consumed by children with cow milk protein allergy. The aim of this study was to evaluate the protein profile of individual samples of Amiata donkey milk and to quantify the different protein fractions in order to better understand the characteristics of donkey milk. Protein fractions of 57 individual whole milk samples were analysed by isoelectric focusing (IEF). The main milk protein fractions were quantified both by IEF gel image analysis and directly on milk using the Agilent 2100 Bioanalyzer. The IEF analysis identified 10 different electrophoretic patterns, which differ from each other in terms of the presence of bands that correspond to homozygous or heterozygous genotypes, as well as the presence/absence of specific protein bands. In addition the quantification of different caseins (αS1, β and κ-CN) and whey proteins (β-LG, α-LA and LZ), highlighted a significant phenotypic variability among individuals which seems to be related to the patterns identified. In particular, different casein:whey protein ratios were identified among jennies and this is known to affect the nutritional, allergenic and technological properties of milk. These findings could be useful in the selection of donkeys with specific milk protein polymorphisms.

Concentration-triggered liquid-to-solid transition of sodium caseinate suspensions as a function of temperature and enzymatic cross-linking

Casein, the major milk protein fraction, is responsible for structure formation in fermented dairy products, and enzymatic cross-linking of caseins represents a possibility to modify texture and physical product properties. In this research, casein cross-linking by microbial transglutaminase (mTGase) was characterised from a colloid rheological perspective. Sodium caseinate (NaCn) at 50 g kg−1 was not (0 h), moderately (3 h) or excessively cross-linked (24 h) using 3 U mTGase per g protein, and subsequently freeze-dried and redissolved at 10–300 g kg−1. The resulting suspensions were characterised in steady and oscillatory shear rheology to obtain viscosity-concentration plots and to evaluate shear thinning and viscoelastic properties. Additional molecular analysis was done by dynamic light scattering and asymmetric flow field flow fractionation, showing that NaCn molecules were associated to hydrated nanoparticles with hydrodynamic radii of ~12 nm and cross-linked predominantly within the same particle, leading to an increased apparent density of the particles with ongoing incubation. This resulted in a transition from soft particles towards a more hard sphere like behaviour in the rheological experiments. While concentrated suspensions of uncross-linked NaCn (0 h) showed properties of a viscoelastic liquid in frequency sweeps over the tested temperature range (5–40 °C), a true liquid-to-solid transition upon cooling was observed for the cross-linked samples. The threshold for this transition was lower for moderately (3 h) than for excessively cross-linked NaCn (24 h), i.e., at lower concentration and higher temperature, presumably because interpenetration of the particles was still possible to some extent.

Productivity and biological value of milk of cows of various eco-genetic types

The article gives comparative characteristics of the quality indicators of dairy raw materials obtained from Holstein first-calf heifers delivered to the Volgograd region of Russia from different countries. The research study consisted in processing the data of qualitative and quantitative indices of the cow’s milk production and assessing the nutritional and biological parameters of milk according to current standards. Differences on productivity, in the nutritional and biological values of milk depending on the ecological and genetic types of animals have been revealed. In terms of the milk yield for 305 days of lactation, the research has established the superiority of animals of American selection compared with ones of German, Danish and Australian selection by 100 kg, 600 kg and 620 kg, respectively. The cows of German selection were registered to have the highest content of the weight fraction of milk fat, i.e., 4.01%. Australian Holstein heifers had the highest weight fraction of milk protein (3.24%) and amino acids (valine, isoleucine, leucine, lysine, methionine, tryptophan, phenylalanine, aspartic acid, cystine, arginine and histidine). Animals of Danish Holstein breed were noted for a higher content of macro- and microelements, i.e., calcium, magnesium, zinc, manganese, iodine and silicon. For animals of Danish and American selections, some activities to increase the weight fraction of milk protein have been recommended to perform.

The surface properties of milk fat globules govern their interactions with the caseins: Role of homogenization and pH probed by AFM force spectroscopy

The surface of milk fat globules consists of a biological membrane rich in polar lipids and glycoproteins. However, high shear stress applied upon homogenization disrupts the membrane and leads to the adsorption of casein micelles, as the major protein fraction of milk. These changes in the interface properties could affect the interactions between native or homogenized milk fat globules and the surrounding protein matrix, at neutral pH and upon acidification. In this study, macroscale rheometry, microscopic observations, nanoscale AFM-based force spectroscopy and physico-chemical analysis were combined to examine the interfacial composition and structure of milk fat globules and to evaluate their interactions with casein micelles. We showed that the surface properties of milk fat globules (biological membrane vs. caseins) and pH govern their interactions with casein micelles. The adhesion between individual fat globules and casein micelles was higher upon homogenization, especially at acid pH where the work of adhesion increased from 3.3 x 10-18 to 14 x 10-18 J for native and homogenized fat globules, respectively. Consequently, casein-coated homogenized fat globules yield stiffer milk acid gels. These findings cast light on the importance of colloidal particle’s surface properties and pH on their connectivity with the surrounding matrix, which modulates the bulk microstructure and rheological properties with potential functional consequences, such as milk lipid digestion.

Biocompatible Nanocomposite Tailored to Endure the Gastric Niche Renders Effective in Vitro Elimination of Intestinal Pathogenic Bacteria and Supports Adhesion by Beneficial Bacteria.

Bacteriocins produced by lactic acid bacteria (LAB) are potent therapeutic arsenals for targeting gastrointestinal pathogens and a promising alternative to antibiotics, because of their selective activity and reduced propensity to trigger collateral damage to the beneficial gut microbes. However, proteolytic inactivation in the gastric niche renders bacteriocins ineffective. The present study addresses this challenge and demonstrates that a biocompatible milk protein fraction can be leveraged to generate a robust nanocargo, which renders protection from proteolysis in the gastric milieu and facilitates delivery of the encapsulated bacteriocin pediocin. In a simulated gastric transit experiment, pediocin-loaded milk protein nanocomposite (Ped-MNC) could render a 3.0 log reduction in the viability of model gastrointestinal pathogens. Ped-MNC is nontoxic to cultured human intestinal cells (HT-29 cells) and effectively abrogates pathogenic bacteria adhering onto intestinal cells. In a combinatorial regimen, Ped-MNC and the beneficial LAB Lactobacillus plantarum DF9 could substantially reduce the levels of the pathogen Enterococcus faecalis MTCC 439 adhering onto HT-29 cells and interestingly the nanocomposite does not hinder adhesion of intestinal cells by the beneficial LAB. The developed nanocomposite holds promise as a niche specific therapeutic for selective mitigation of intestinal pathogens.

Milk Protein Fractionation by Means of Spiral-Wound Microfiltration Membranes: Effect of the Pressure Adjustment Mode and Temperature on Flux and Protein Permeation.

Protein fractionation by means of microfiltration (MF) is significantly affected by fouling, especially when spiral-wound membranes (SWMs) are used. We investigated the influence of the mode of transmembrane pressure (ΔpTM) increase to target level and the deposit layer pressure history on the filtration performance during skim milk MF at temperatures of 10 °C and 50 °C. Two filtration protocols were established: No. 1: ΔpTM was set directly to various target values. No. 2: Starting from a low ΔpTM, we increased and subsequently decreased ΔpTM stepwise. The comparison of both protocols tested the effect of the mode of ΔpTM increase to target level. The latter protocol alone tested the effect of the deposit layer history with regard to the ΔpTM. As expected, flux and protein permeation were both found to be functions of the ΔpTM. Further, both measures were independent of the filtration protocol as long as ΔpTM was held at a constant level or, as part of protocol No. 2, ΔpTM was increased. Thus, we can state that the mode of ΔpTM increase to target level does not affect filtration performance in SWM. We found that after completion of a full cycle of stepping ΔpTM up from 0.5 bar to 3.0 bar and back down, flux and deposit layer resistance were not affected by the deposit layer history at 10 °C, but they were at 50 °C. Protein permeation, however, was lower for both 10 °C and 50 °C, when the ΔpTM cycle was completed. The processing history had a significant impact on filtration performance due to remaining structural compression effects in the deposited layer, which occur most notably at higher temperatures. Furthermore, temperatures of 50 °C lead to deposit layer aging, which is probably due to an enhanced crosslinking of particles in the deposit layer. Apart from that, we could show that fouling resistance does not directly correlate with protein permeation during skim milk MF using SWM.

Life Cycle Assessment of a milk protein fractionation process: Contribution of the production and the cleaning stages at unit process level

This paper aims at presenting a consistent Life Cycle assessment of the environmental impact of an industrial milk protein fractionation process at the level of unit processes (gate to gate approach), focusing on the effective contribution of both the production and the cleaning steps. The precise assessment of the impact of cleaning stages could indeed constitute key issues for the optimisation and management of food plants. The results show that the production phase accounts for approximately two-thirds of the environmental impact of the entire food manufacturing process, and the cleaning phase for more than 30% of the total impact. The latter is, however, underestimated due to methodological drawbacks and partly unavailable data. Among both the production and the cleaning stages the most impacting unit processes are the membrane and the thermal operations mainly due to the single-use of cleaning solutions and several temperature changes. Hence, for reduction of the overall environmental impact of the milk protein fractionation process it is advisable to primarily focus on improvement and optimisation of the microfiltration operation and secondly, on the thermal units.