Network analysis of the proteome and peptidome sheds light on human milk as a biological system.

Proteins and peptides found in human milk have bioactive potential to benefit the newborn and support healthy development. Research has been carried out on the health benefits of proteins and peptides, but many questions still need to be answered about the nature of these components, how they are formed, and how they end up in the milk. This study explored and elucidated the complexity of the human milk proteome and peptidome. Proteins and peptides were analyzed with non-targeted nanoLC-Orbitrap-MS/MS in a selection of 297 milk samples from the CHILD Cohort Study. Protein and peptide abundances were determined, and a network was inferred using Gaussian graphical modeling (GGM), allowing an investigation of direct associations. This study showed that signatures of (1) specific mechanisms of transport of different groups of proteins, (2) proteolytic degradation by proteases and aminopeptidases, and (3) coagulation and complement activation are present in human milk. These results show the value of an integrated approach in evaluating large-scale omics data sets and provide valuable information for studies that aim to associate protein or peptide profiles from biofluids such as milk with specific physiological characteristics.

Nutritional factors affecting camel (Camelus dromedarius) milk composition.

Saharan population in Algeria still depending on bovine milk, which suffers from serious constraints undermining its sustainability. Camelus dromedarius milk has experienced growing demand following the emerging market requirements for livestock production and dairy farming over the past decade. The present work aimed at analysing the effect of nutritional regime on milk quality. The differences in pH, Acidity D°, Ash and Fats were significant. The pH was negatively influenced by the intensification conditions such as the much higher use of concentrates. The major constituents of milk were strongly and positively correlated with barley, wheat bran, TN/Kg.DM (Total Nitrogen/ Kg. Dry Matter), Kg.DM, Concentrates and daily watering. The results showed that a good energy-protein balance around 73 g PDI/UFL (Protein Digestible in the Intestine/Energetic Forage Unit for milk production) was beneficial for a better milk protein ratio. The use of corn, soybeans, palm dates and VM-premix (Vitamin Mineral) supplementation were also favourable to the synthesis of fats. Crude fiber and cell walls were better valued in the synthesis of fats with the availability of concentrates and the increasing of TN /Kg.DM and VM-premix rate in dietary regime. The vitamin C content elevate following high ratio of UFL /Kg.DM and PDI/UFL. For thus, the influence of nutritional status can lead to major improvements that need also more advanced and detailed studies.

Comparative proteomic analysis of the changes in mare milk associated with different lactation stages and management systems.

Mare milk has traditionally been attributed a number of health promoting properties. However, knowledge on its composition and functionality remains scarce, with particularly limited studies on mare milk proteomics. This study deeply characterized mare milk proteome accounting for both caseins and proteins in the whey fraction, also addressing the impact of lactation stage and different management systems. Milk samples from Basque Mountain Horse breed mares belonging to three different farms and three lactation stages were analysed after in-gel and in-solution digestion using nLC-MS/MS. Among the 469 proteins identified, the content of alpha-1 antitrypsin was significantly higher in pasture-based compared to other systems. Moreover, lactation stage significantly affected the content of beta-lactoglobulin II, immunoglobulin-like domain-containing protein, interferon alpha-inducible protein 27, lactotransferrin, polypeptide N-acetylgalactosaminyltransferase, and transforming acidic coiled-coil containing protein 2. This study contributes to the deep characterization of mare milk proteome and provides new insights into the effect of different production factors.

Lipidomic and proteomic profiling identifies the milk fat globule membrane composition of milk from cows and camels.

This study was designed to detect lipidomic and proteomic differences in the milk fat globule membrane (MFGM) fractions of cow and camel milk samples. In total, 353 lipid species were detected in these analyses, including 77 PEs, 30 PCs, 28 PIs, 59 SMs, 54 Cers, 13 LPCs, 14 LPEs, 20 PSs, and 4 PGs. These included 54 polar lipid species that differed significantly in abundance between cow and camel milk. Glycerophospholipid metabolism was identified as a core metabolic pathway associated with camel milk composition. Furthermore, 547 proteins exhibiting differential abundance were identified by a label-free proteomics methodology when comparing samples of MFGMfrom camels and cows. Of these proteins, those that differed most in expression between these groups were associated with metabolic pathways, including endoplasmic reticulum activity, endocytosis, and PI3K-Akt signaling. In conclusion, our findings provide a more thorough understanding of the composition of MFGM and its physiological significance, hence offering robust evidence for the potential utilization of camel milk as a nutritional resource in future developments.

Effect of dipotassium phosphate addition and heat on proteins and minerals in milk protein beverages.

Our objective was to determine the effects of dipotassium phosphate (DKP) addition, heat treatments (no heat, high temperature, short time [HTST]: 72°C for 15 s, and direct steam injection UHT: 142°C for 2.3 s), and storage time on the soluble protein composition and mineral (P, Ca, K) concentration of the aqueous phase around casein micelles in 7.5% milk protein-based beverages made with liquid skim milk protein concentrate (MPC) and micellar casein concentrate (MCC). Milk protein concentrate was produced using a spiral wound polymeric membrane, and MCC was produced using a 0.1-µm ceramic membrane by filtration at 50°C. Two DKP concentrations were used (0% and 0.15% wt/wt) within each of the 3 heat treatments. All beverages had no other additives and ran through heat treatment without coagulation. Ultracentrifugation (2-h run at 4°C) supernatants of the beverages were collected at 1, 5, 8, 12, and 15-d storage at 4°C. Phosphorus, Ca, and K concentrations in the beverages and supernatants were measured using inductively coupled plasma spectrometry. Protein composition of supernatants was measured using Kjeldahl and sodium dodecyl sulfate-PAGE. Micellar casein concentrate and MPC beverages with 0.15% DKP had higher concentrations of supernatant protein, Ca, and P than beverages without DKP. Protein, Ca, and P concentrations were higher in MCC supernatant than in MPC supernatant when DKP was added, and these concentrations increased over storage time, especially when lower heat treatments (HTST or no heat treatment) had been applied. Dipotassium phosphate addition caused the dissociation of αS-, ß-, and κ-casein, and casein proteolysis products out of the casein micelles, and DKP addition explained over 70% of the increase in supernatant protein, P, and Ca concentrations. Dipotassium phosphate could be removed from 7.5% of protein beverages made with fresh liquid MCC and MPC (containing a residual lactose concentration of 0.6% to 0.7% and the proportional amount of soluble milk minerals), as these beverages maintain heat-processing stability without DKP addition.

Milk beverage base with lactose removed with ultrafiltration: Effect of fat and protein concentration on sensory and physical properties.

Our objectives were to determine the effect of fat (skim to whole milk) and protein (3.4%-10.5%) concentration on the sensory and physical properties of milk beverage base that had lactose and other low molecular components removed by ultrafiltration (UF). In experiment 1, a matrix of 16 treatments was produced to achieve 4 levels of lactose removal (0%, 30%, 70%, and 97%) at each of 4 fat levels (skim, 1%, 2%, and whole milk). In experiment 2, a matrix of 12 treatments was produced to achieve 4 levels of lactose removal (0%, 30%, 70%, and 97%) at each of 3 protein concentrations (3.4%, 6.5%, and 10.5% protein). Physical and sensory properties of these products were determined. Removal of >95% of milk lactose by UF required a diafiltration volume of approximately 3 times the milk volume. Lactose and low molecular weight solute removal increased whiteness across the range from skim to whole milk while decreasing viscosity and making milk flavor blander. In addition, lactose (and other low molecular weight solute) removal by UF decreased titratable acidity by more than 50% and increased milk pH at 20°C to >7.0. Future work on milk and milk-based beverages with lactose removed by UF needs to focus on interaction of the remaining milk solids with added flavorings, changing casein to whey protein ratio before removal of lactose by UF, and the effect of lactose and low molecular weight solute removal on heat stability, particularly for neutral-pH, shelf-stable milk-based beverages.

Advances in separation and identification of biologically important milk proteins and peptides.

Milk is a rich source of biologically important proteins and peptides. In addition, milk contains a variety of extracellular vesicles (EVs), including exosomes, that carry their own proteome cargo. EVs are essential for cell-cell communication and modulation of biological processes. They act as nature carriers of bioactive proteins/peptides in targeted delivery during various physiological and pathological conditions. Identification of the proteins and protein-derived peptides in milk and EVs and recognition of their biological activities and functions had a tremendous impact on food industry, medicine research, and clinical applications. Advanced separation methods, mass spectrometry (MS)-based proteomic approaches and innovative biostatistical procedures allowed for characterization of milk protein isoforms, genetic/splice variants, posttranslational modifications and their key roles, and contributed to novel discoveries. This review article discusses recently published developments in separation and identification of bioactive proteins/peptides from milk and milk EVs, including MS-based proteomic approaches.

Evaluation of ELISA Test Kits for Detection of Milk Protein in Frying Oil Treated at Different Temperatures.

Milk is a common ingredient in fried foods. Allergen cross-contact can occur through the reuse of frying oil. To enable assessment of the allergy risk of reused oil, methods for quantification of milk protein in oil are needed. This study evaluated four commercial ELISA test kits in comparison with the 660 nm total protein assay for the detection of milk protein in oil after frying. Corn oil spiked with nonfat or whole milk powder were fried at 150 °C or 180 °C for 3 min and were analyzed by ELISA kits either directly or after preextraction with phosphate-buffered saline containing 0.05% Tween (PBST). All four ELISA kits performed well in quantifying milk protein in unheated oil, achieving normalized recoveries of 72.1-115.9% compared with that determined in reference solutions (PBST spiked with nonfat or whole milk powder, 100%). Frying lowered the amount of protein detected, but the extent of reduction differed between test kits. In nonfat milk powder-spiked oil fried at 150 °C, normalized recoveries determined by Veratox Total Milk and BioKits BLG Assay (49.9% and 43.6%, respectively) were higher than that determined by the 660 nm assay (25.4%). Normalized recoveries determined by ELISA Systems Casein and Beta-Lactoglobulin (BLG) kits were substantially lower (9.7% and 2.4%, respectively). In samples fried under typical frying temperature (180 °C), very little protein (0.1-7.4%) was detected. Inclusion of PBST preextraction improved the detection of the two test kits targeting BLG but lowered the level of protein detected by Veratox and ELISA Systems Casein in fried samples. Overall, the ELISA kits evaluated could effectively quantify milk protein in unheated oil without the need to remove the oil phase prior to analysis. Heat treatment was the key factor negatively affecting protein quantitation. Such impact needs to be considered when ELISA test results are used for assessing the allergy risk of reused frying oil.

Physicochemical properties of micellar casein retentates generated at different microfiltration temperatures.

Processing temperature has a significant influence on the composition and functionality of the resulting streams following microfiltration (MF) of skim milk. In this study, MF and diafiltration (DF) were performed at 4 or 50°C to produce ß-casein (ß-CN)-depleted and nondepleted (i.e., native casein profile) micellar casein isolate retentates, respectively. Microfiltration combined with extensive DF resulted in a 40% depletion of ß-CN at 4°C, whereas no ß-CN depletion occurred at 50°C. Microfiltration at 4°C led to higher transmission of calcium into permeates, with retentate generated at 4°C containing less total calcium compared with retentate generated at 50°C, based on the volume of retentate remaining. Higher heat stability at 120°C was measured for retentates generated at 4°C compared with those at 50°C, across all pH values measured. Retentates generated at 4°C also had significantly lower ionic calcium values at each pH compared with those generated at 50°C. Higher apparent viscosities at 4°C were measured for retentates generated at 4°C compared with retentates generated at 50°C, likely due to increased voluminosity of ß-CN-depleted casein micelles. The results of this study provide new information on how changing the composition of MF retentate, by appropriate control of processing temperature and DF, can alter physicochemical properties of casein micelles, with potential implications for ingredient functionality.

Comparative evaluation of milk proteins and oil-seed-cake-derived proteins extracted by chemical and biological methods for obesity management.

BACKGROUND: In light of the exponential rise in global population, there is a critical requirement to reduce food waste on a global scale. According to studies, agricultural wastes such as oil-seed cakes offer great nutritional value. Acid precipitation (A) and alkaline extraction methods (traditional methods) were used to extract protein from oil-seed cakes; however, both procedures are linked to decreased protein quality and quantity, which prompted the development of a novel strategy known as the biological/microbial/probiotic (B) method. Therefore, the present study aimed to highlight the optimal way of protein extraction from oil-seed cakes and the effect of extraction methods on protein efficacy against obesity. The outcomes were also compared with milk proteins. RESULTS: In vitro study provided evidence that proteins from both sources (plant and milk) suppressed adipogenesis and stimulated adipolysis in 3T3L-1 cells. For the in vivo study, mice were fed with different protein extracts: soya protein preparation (SPP), ground protein preparation (GPP), whey protein (WP) and casein protein (CP) containing 40% of their calories as fat. Body weight decreased significantly in all the rats except CP-fed rats. Body mass index, atherogenic index, plasma triglyceride and very-low-density lipoprotein cholesterol level decreased significantly in all the groups in comparison to the model group (high-fat-diet group), but the decrease was more pronounced in plant proteins than milk proteins. In hepatocytes, the expression of fasting-induced adipose factor, carnitine palmitoyltransferase I and peroxisome proliferator-activated receptor α genes was increased significantly in SPP-fed groups. Adiponectin gene expression was upregulated significantly in visceral fat tissue in groups fed SPP-B, GPP-A and CP, whereas leptin gene was downregulated significantly in all groups except SPP-A. CONCLUSION: This study demonstrates that SPP-B showed the most effective anti-obesity property, followed by WP. Additionally, we found that the biological precipitation approach produced better outcomes for plant proteins isolated from oil-seed cakes than the acid precipitation method. © 2023 Society of Chemical Industry.

The effect of whey source on heat-induced aggregation of casein and whey protein mixtures of relevance to infant nutritional product formulation.

Sweet and, to a lesser extent, acid whey protein ingredients can be used for the formulation of infant nutritional products. Unlike acid whey, sweet whey contains caseinomacropeptide (CMP), a heat-stable peptide liberated from κ-casein during cheese and rennet casein manufacture. Four protein systems-sweet whey (SW) and acid whey (AW), with or without standardization for CMP protein content-were added to skim milk (50/50, wt/wt) and unheated or heated to 85 or 110°C. These 12 samples were assessed for physicochemical stability in the presence of added calcium at pH 6.8. The effect of CMP content on the physicochemical properties of the protein systems was also assessed. Without preheat treatment, mixtures of AW and skim milk (SM) were more heat stable than SW and SM, demonstrating the effect of whey protein type on heat stability. Preheat treatment of the SW in the presence of SM significantly improved the heat stability of the resultant protein systems on subsequent heating. All of the protein systems had significantly lower heat stability with the addition of Ca, although the reduction was significantly smaller for the heated protein systems than the unheated controls. The findings can help identify heating parameters and ingredients for optimizing processing stability and physicochemical characteristics of nutritional beverages such as infant formulations.

A three-year comparison of once-a-day and twice-a-day milking in seasonal-calving pasture-based systems.

Globally, the majority of dairy cows are milked twice a day (TAD); however, in pasture-based production systems, such as in Ireland, the idea of milking once a day (OAD) is being considered for reasons such as improved work-life balance. The immediate effects within a lactation, as well as the multilactation consequences of OAD, compared with TAD milking, require understanding. The objective of this randomized experiment was to compare OAD and TAD milking, over a 3-yr period, by examining the differences in milk production and composition, body weight (BW), body condition score (BCS), dry matter intake (DMI), udder characteristics, locomotion score, and milking time. Over the 3-yr period, 83 cows were enrolled in the experiment; 32, 44, and 48 cows in yr 1, 2, and 3 of the experiment, respectively. Each year, 23% of the herds were primiparous animals, while the remainder were second lactation or greater in parity. All cows were milked in the morning at 0700 h; only cows milked TAD were milked a second time each day at 1600 h. Cows rotationally grazed pastures for the duration of the lactating period and were housed during the nonlactating period. Milking cows OAD reduced cumulative milk yield by 26%, and milk solids yield (kg of fat + kg of protein) by 21%, across the 3 yr of the experiment when compared with cows milked TAD which produced 4,126 and 365 kg/cow, respectively. A contributory factor to the reduced production was a shorter lactation length (9.7 d) of the cows milked OAD compared with TAD (294 d). Milk fat percent of cows milked TAD was similar for all 3 yr of the study (5.05%), whereas milk fat percent of the cows milked OAD increased year on year, with each year being greater than the previous year (5.02%, 5.32%, and 5.70% for yr 1, 2, and 3; respectively). Milk protein percent was greater (+0.19%) for cows milked OAD compared with TAD which was 3.78%. Compared with cows milked TAD, total DMI for cows milked OAD was 22% less at the start of lactation (<167 d), but as the lactation progressed (>167 d) we observed no difference in DMI between treatments. Similar to the literature, milking cows OAD significantly increased average somatic cell score, both during (+16%) and at the end of lactation (+19%), compared with milking cows TAD which were 4.69 and 4.79, respectively. We detected positive aspects associated with OAD milking such as greater BW, BCS, and fertility performance. Milking OAD reduced both milking time per cow per day (reductions ranged from 34% in the first 4 mo of lactation to 43% during mo 5-9 of lactation) and milking time per liter of milk (-3.5 s/L) throughout lactation, leading to less labor inputs on-farm which can have positive implications for farmer work-life balance. The significant time saving and potential savings in costs (e.g., electricity) need to be considered in conjunction with the milk production reduction when considering OAD milking for the entire lactation.

Novel details on the dissociation of casein micelle suspensions as a function of pH and temperature.

Membrane filtration is a widespread process for fractionation and recombination of milk components. Although the dissociation of micellar caseins has been studied in detail in skim milk, it is important to better understand the dissociation dynamics occurring between the colloidal and noncolloidal fractions in systems of modified composition. This research aimed at understanding the dissociation of casein proteins in micellar fractions depleted of whey proteins. Casein micelle dispersions were tested at neutral pH and pH 6 (using glucono-δ-lactone as acidulant), after incubation at 4°C or 22°C, and compared with skim milk. The ionic composition of the serum phase was measured using inductively coupled plasma-mass spectrometry, and the protein distribution analyzed using reversed phase-HPLC coupled with mass spectrometry. When incubated at 22°C, there were no differences in casein micelle dissociation between skim milk and whey protein-depleted micelles (∼2.6% dissociated casein). No additional dissociation occurred by lowering the pH from 6.8 to 6 at 22°C, albeit there were more soluble ions at low pH (71% Ca and 65% P). At 4°C, there was an increased amount of ß-casein found in the serum phase (23-33% of total ß-casein). In addition, there was an uneven dissociation behavior of the various genetic ß-casein variants, whereof A2 was more readily released with cooling. In skim milk, approximately 22%, 18%, and 14% of κ-, αS2, and αS1-caseins, respectively, were dissociated from the micellar phase upon cooling and acidification to pH 6.0. This was in contrast to whey protein-depleted casein suspensions, in which only 6%, 5%, and 3% of κ-, αS2, and αS1-caseins, respectively, had dissociated. The results suggested that the whey proteins in the serum phase play a role in the equilibrium between colloidal and soluble caseins in milk. This is of great relevance in processes such as cold membrane fractionation, where more attention should be given to the protein composition in the serum phase, especially when concentration is combined with fractionation of the serum proteins.

Detection of the ß-lactoglobulin genotype in zebu cattle (Gangatiri) milk using high-resolution accurate mass spectroscopy.

We studied the genetic polymorphism of beta-lactoglobulin (ß-Lg) whey protein in Gangatiri zebu cows for this Research Communication. The polymorphic nature of milk protein fractions and their association with milk production traits, composition and quality has attracted several efforts in evaluating the allelic distribution of protein locus as a potential dairy trait marker. Genetic variants of ß-Lg have highly significant effects on casein number (B > A) and protein recovery (B > A) and also determine the yield of cheese dry matter (B > A). Molecular techniques of polyacrylamide gel electrophoresis and high-resolution accurate mass-spectroscopy were applied to characterize the ß-Lg protein obtained from the Gangatiri breed milk. Sequence analysis of ß-Lg showed the presence of variant B having UniProt database accession number P02754, coded on the PAEP gene. Our study can provide reference and guidance for the selection of superior milk (having ß-LgB) from this indigenous breed that could potentially give a good yield of ß-Lg for industrial applications.

Influence of ß-casein genotype on physicochemical properties and functionality of bovine milk.

Several studies have been focused on the effect of milk protein genetic variants on milk physicochemical properties and functionality in recent years. ß-casein, an important protein related to milk processibility, has been reported to have 2 main genetic variants A1 and A2, for which cows may be homozygous or heterozygous. In this study, several physicochemical properties of milk with ß-casein variants A1A1, A1A2, and A2A2 from 3 collection occasions were analyzed. Higher manganese content and lower pH were found to be associated with the A1A1 variant compared with the other 2 genotypes. Better rennet and acid coagulation were found in A1A1 milk compared with A1A2 and A2A2 milk (although P > 0.05), whereas A2A2 milk was more stable to creaming compared with the other 2 genotypes, which may be linked to its smaller fat globule size. Thus, milk from cows with A1A1 genotype could be preferable for cheese making, while that with A2A2 variant can be used in formulations requiring good stability against creaming, and for example, yogurt making, where the softer yogurt texture may be easier to digest.

Effect of temperature and protein concentration on the protein types within the ultracentrifugation supernatant of liquid micellar casein concentrate.

Liquid micellar casein concentrate (MCC) is an ideal milk-based protein ingredient for neutral-pH ready-to-drink beverages. The texture and mouthfeel of liquid MCC-based beverages depend on the beverage protein content, as well as the composition of soluble proteins in the aqueous phase around the casein micelle. The objective of this study was to determine the composition of soluble proteins in the aqueous phase around the casein micelles in skim milk and liquid MCC containing 7.0% and 11.6% protein content. Skim milk was pasteurized and concentrated to 7% protein content by microfiltration and then to 18% protein content by ultrafiltration. The 18% MCC was then serially diluted with distilled water to produce 11.6% and 7.0% protein MCC. Skim milk, 7.0% MCC, and 11.6% MCC representing starting materials with different protein concentrations were each ultracentrifuged at 100,605 × g for 2 h. The ultracentrifugation for each of the starting materials was performed at 3 different temperatures: 4°C, 20°C, and 37°C. The ultracentrifugation supernatants were collected to represent the aqueous phase around the casein micelle in MCC solutions. The supernatants were analyzed by Kjeldahl to determine the crude protein, casein, and casein as a percentage of crude protein content, and by sodium dodecyl sulfate PAGE to determine the composition of the individual proteins. Most of the proteins in MCC supernatant (about 45%) were casein proteolysis products. The remaining proteins in the MCC supernatant consisted of a combination of intact αS-, ß-, and κ-caseins (about 40%) and serum proteins (14-18%). Concentrations of αS-casein and ß-casein in the supernatant increased with decreasing temperature, especially at higher protein concentrations. Temperature and interaction between temperature and protein explained about 80% of the variation in concentration of supernatant αS- and ß-caseins. Concentration of supernatant κ-casein, casein proteolysis products, and serum protein increased with increasing MCC protein concentration, and MCC protein concentration explained most of the variation in supernatant κ-casein, casein proteolysis products, and serum protein concentrations. Predicted MCC apparent viscosity was positively associated with the dissociation of αS- and ß-caseins. Optimal beverage viscosity could be achieved by controlling the dissociation of these proteins in MCC.

Production and functional evaluation of nonfat dry milk with whey proteins as fibrils.

Commercial manufacturing of dairy products involves the addition of dairy ingredients (such as nonfat dry milk and milk protein concentrates), as well as nondairy additives (such as gums, stabilizers, emulsifiers, and texture modifiers) to get the best product appearance, maintain the product quality, and extend shelf life. Though these nondairy additives are not harmful, consumers do not prefer them in dairy food formulations. Therefore, the dairy industry is working on improving the inherent functionality of dairy ingredients using different processes. Recently, fibrillation emerged as a new technique to convert globular proteins such as whey proteins into fibrils, which provide enhanced viscosity, foaming, and emulsification capacity. Therefore, skim milk was subjected to microfiltration followed by ultrafiltration of microfiltration permeate to fractionate whey proteins. Then, whey proteins were selectively fibrillated and mixed back with other streams of microfiltration and ultrafiltration to get fibrillated skim milk. Fibrillated skim milk was spray-dried to get fibrillated nonfat dry milk (NDM). Visible whey protein fibrils were observed in reconstituted fibrillated NDM, which showed survival of fibrils in fibrillated NDM. Fibrillated NDM showed significantly higher viscosity than control NDM. Fibrillated NDM also showed higher emulsification capacity, foaming capacity, and stability than the control NDM but lower gel strength. Considering the improved functionality of fibrillated NDM, they can be used in product formulations such as ice cream mix, where the thickening of a solution, good emulsification, and foaming properties are required.

Effect of whey protein isolate addition on set-type camel milk yogurt: Rheological properties and biological activities of the bioaccessible fraction.

The manufacture of camel milk (CM) yogurt has been associated with several challenges, such as the weak structure and watery texture, thereby decreasing its acceptability. Therefore, this study aimed to investigate the effect of whey protein isolate (WPI) addition on the health-promoting benefits, texture profile, and rheological properties of CM yogurt after 1 and 15 d of storage. Yogurt was prepared from CM supplemented with 0, 3, and 5% of WPI and compared with bovine milk yogurt. The results show that the water holding capacity was affected by WPI addition representing 31.3%, 56.8%, 64.7%, and 45.1% for yogurt from CM containing 0, 3 or 5% WPI, and bovine milk yogurt, respectively, after 15 d. The addition of WPI increased yogurt hardness, adhesiveness, and decreased the resilience. CM yogurt without WPI showed lower apparent viscosity, storage modulus, and loss modulus values compared with other samples. The supplementation of CM with WPI improved the rheological properties of the obtained yogurt. Furthermore, the antioxidant activities of yogurt before and after in vitro digestion varied among yogurt treatments, which significantly increased after digestion except the superoxide anion scavenging and lipid oxidation inhibition. After in vitro digestion at d 1, the superoxide anion scavenging of the 4 yogurt treatments respectively decreased from 83.7%, 83.0%, 79.1%, and 87.4% to 36.7%, 38.3%, 44.6%, and 41.3%. The inhibition of α-amylase and α-glucosidase, angiotensin-converting enzyme inhibition, cholesterol removal, and degree of hydrolysis exhibited different values before and after in vitro digestion.

The effect of heat treatment on the lactosylation of milk proteins.

Protein lactosylation is a significant modification that occurs during the heat treatment of dairy products, causing changes in proteins' physical-chemical and nutritional properties. Knowledge of the detailed lactosylation information on milk proteins under various heat treatments is important for selecting appropriate thermo-processing and identifying markers to monitor heat load in dairy products. In the present study, we used proteomics techniques to investigate lactosylated proteins under different heating temperatures. We observed a total of 123 lactosylated lysines in 65 proteins, with lactosylation even occurring in raw milk. The number of lactosylated lysines and proteins increased moderately at 75°C to 130°C, but dramatically at 140°C. We found that 6 out of 10, 9 out of 16, 6 out of 12, and 5 out of 15 lysine residues in κ-casein, ß-lactoglobulin, α-lactalbumin, and αS1-casein, respectively, were lactosylated under the applied heating treatment. Moreover, different lactosylation states of individual lysines and proteins can indicate the intensity of heating processes. Lactosylation of K14 in ß-lactoglobulin could distinguish pasteurized and UHT milk, while lactosylation of lactotransferrin can reflect moderate heat treatment of products.

Milk coagulation properties are moderately heritable in dairy cows: a meta-analysis using the random-effects model.

This study aimed to conduct a meta-analysis using the random-effects model to merge published genetic parameter estimates for milk coagulation properties (MCP: comprising rennet coagulation time (RCT), curd-firming time (k20), curd firmness 30 min after rennet addition (a30), titrable acidity (TA) and milk acidity or pH) in dairy cows. Overall, 80 heritability estimates and 157 genetic correlations from 23 papers published between 1999 and 2020 were used. The heritability estimates for RCT, a30, k20, TA, and pH were 0.273, 0.303, 0.278, 0.189 and 0.276, respectively. The genetic correlation estimates between RCT-a30, RCT-pH, and RCT-TA were 0.842, 0.549 and -0.565, respectively. Genetic correlation estimates between RCT and production traits were generally low and ranged from -0.142 (between RCT and casein content) to 0.094 (between RCT and somatic cell score). Moderate and significant genetic correlations were observed between a30-pH (-0.396) and a30-TA (0.662). Also, the genetic correlation estimates between a30 and production traits were low to moderate and varied from -0.165 (between a30 and milk yield) to 0.481 (between a30 and casein content). Genetic correlation estimates between pH and production traits were low and varied from -0.190 (between pH and milk protein percentage) to 0.254 (between pH and somatic cell score). The results of this meta-analysis indicated the existence of additive genetic variation for MCP that could be used in genetic selection programs for dairy cows. Because of the moderate heritability of MCP and small genetic correlations with production traits, it could be possible to improve MCP with negligible correlated effects on production traits.