Goat Milk Protein Research Articles

Polymorphism in β-lactoglobulin gene and its association with dairy goats’ production traits

In the dairy industry, producing milk with greater contents of fat and protein is an important goal. In addition to the phenotypic selection, it is necessary to develop a genetic profile with several polymorphisms located at genes associated with greater percentages of fat and protein in goat milk. These polymorphisms can be used in marker-assisted selection (MAS) for the productive traits of dairy goats. We assessed two polymorphisms already described in the gene that encodes the β-lactoglobulin protein (BLG gene) in goats. One is located at the 5′ promoter region of the gene and the other one is located at the exon 7. Besides that, we associated these polymorphisms with productive characteristics of milk from animals of Saanen and Alpine breeds. A sample of 130 Saanen, Alpine and crossbreed goats were randomly chosen to be genotyped for polymorphisms in the BLG gene for PCR-RFLP. To estimate the predicted breeding values, the REMLF90 application was used, and the association between the polymorphism and the predicted breeding value from the animals. In the promoter region, the single nucleotide polymorphism (SNP) at position − 60 (C/T) was associated with the percentage of milk proteins, and the TT genotype presented higher breeding values for the protein percentage. We found in the exon 7 region, two very close polymorphisms, a base substitution at position + 4601 (S1/S2) and a variable number tandem repeat (VNTR) at position + 4641 (I2/I3). The S1S2 genotype showed a higher percentage of milk fat and dry extract when compared to the S2S2 genotype, but showed no difference compared to the S1S1 for the same trait. Our results pointed out these two polymorphisms, present in the beta-lactoglobulin gene, as candidates to be used in breeding programs to increase both the protein and fat contents of goat milk. Validation tests, however, must be done through genotyping a larger sample of animals

Goat milk proteins enriched with Agaricus blazei Murrill ss. Heinem extracts: Electrophoretic, FTIR, DLS and microstructure characterization

This study aimed to characterize mixtures of goat milk proteins and Agaricus blazei Murrill (ABM) extracts (aqueous, AE and polysaccharides, PE). The mixtures showed stable particles with ζ-potential more negative than −41.1 mV. The addition of AMB extracts to goat milk did not result in a significant particle size change, whereas their addition to heated goat milk significantly increased mean particle diameter (from 194 nm to 225 nm). Fourier Transform Infrared Spectroscopy (FTIR) showed that ABM extracts provoked changes in the secondary structure of goat milk proteins and interactions between polysaccharides and milk proteins predominantly via hydrogen and/or glycoside bonds and hydrophobic interactions. The milk protein profiles revealed proteolytic activity in mixtures with AE resulting in the formation of five new polypeptides. The different microstructures of mixtures with AE and PE were found by Scanning Electron Microscopy (SEM). A schematic representation of possible milk proteins-ABM extracts interactions has been given.

The nutritional therapeutic values and chemical properties of goat milk

Goat is known as poor man’s animal. The fat globules are smaller in goat milk, which makes it easily digestible. Polyunsaturated fatty acids in goat milk fat, is mainly responsible for anticancerous behavior of goat milk. Although protein is somewhat low in goat milk than cow milk, the digestibility of goat milk protein is higher compared to cow milk protein. Taurine present in goat milk is reported to have inhibitory action on cardiovascular disease leads to synthesis of essential amino acids. Goat’s milk contains less lactose than cow’s milk, which is beneficial to lactose intolerance patients. Higher selenium concentration in goat milk, results in platelet regeneration when suffering from dengue fever. Bioactive peptides released during fermentation and invitro digestion are reported to produce antioxidant and antimicrobial peptides. Sialic acid present in caprine milk is also reported to help fast brain development. As compared to milk of other milch animals, goat’s milk has great potential to prevent various diseases. Beside nutritional properties, goat milk possesses potent nutraceutical and Therapeutic properties making it most suitable for infants, older and convalescent people. In this review, strong nutraceutical power of caprine milk is briefly explored.

Heating affects protein digestion of skimmed goat milk under simulated infant conditions

The objective of this research was to analyse the effects of heating on digestion of skimmed goat milk proteins. Most previous goat milk digestion studies evaluated the digestion only based on the supernatant. In this study, digestion of skimmed goat milk was studied in both supernatant and gastric clot. The results indicated that, compared to mild temperature heated samples (≤75 °C), samples heated at ≥80 °C showed more extensive gastric clot formation with a higher protein digestion rate, but also resulted in a larger amount of undigested whey proteins due to its severe aggregation. For the peptidome, β-casein was the major source of bioactive peptides. The samples heated at 65 °C showed higher bioactive peptide abundances, whereas at temperatures higher than 75 °C, it was reduced due to cleavage into smaller peptides. Overall, this study showed that different heating temperatures induced different whey protein denaturation degrees, which affected their digestion in skimmed goat milk..

Comparative Analysis of the Protein Composition of Goat Milk from French Alpine, Nubian, and Creole Breeds and Holstein Friesian Cow Milk: Implications for Early Infant Nutrition.

Simple SummaryGoat’s milk is a food that contains proteins of value for nutrition. The protein profile in the milk of goat breeds is different from that of cow milk, with a lower relative abundance of allergenic proteins. In addition, regardless of the breed, goat milk has beta-casein of type A2 in a more significant proportion than cow milk, which impacts different bioactive peptides hydrolyzed in the milk of the species.Of the diversity of proteins and high digestibility, goat milk will be a food of significant value for infant nutrition. The genetic polymorphisms of milk proteins play an essential role in the different degrees of allergic reactions. This work aimed to identify the proteins and peptides in the composition of goat milk and compare them to those in cow’s milk. The work was performed with goats French Alpine, Nubian, and Creole breeds and Holstein Friesian milking cows at the Universidad Autónoma de Querétaro, Amazcala. We investigated the relative abundance of goat and cow milk protein fractions by SDS-PAGE resolution and the densitometric analysis of gels. The protein alfa-casein was (17.67 ± 0.46) for Creole, (19.18 ± 0.88) French Alpine, (17.35 ± 0.49) Nubian, and (35.92 ± 1.96) Holstein cows. The relative abundance obtained from alfa-casein was statistically different between goats and cows, and this protein was vital because it is a protein related to allergies. On the other hand, the amino acid in position 67 of the beta-casein from three goat breeds is a Proline, so it is assumed that the beta-casein variant of goat milk is an A2-type. The latter has excellent relevance for infant nutrition and differs from cow milk.

Application of Calcium Citrate in the Manufacture of Acid Rennet Cheese Produced from High-Heat-Treated Goat's Milk from Spring and Autumn Season.

The stability of milk proteins is affected by changes in the pH value of milk, the heating temperature, and the addition of calcium compounds or chelating agents, which can cause alterations in calcium distribution. The purpose of this study was to determine the potential of the use of calcium citrate to manufacture fresh acid rennet cheese from high-temperature-pasteurized goat’s milk (90 °C, 15 s) from the spring and autumn season and the effect of the calcium dose used on the physicochemical and organoleptic properties of the cheese. Autumn milk was found to be a richer source of total solids, confirming the effect of the production season on milk quality. The applied doses of calcium did not cause the denaturation of goat milk proteins and allowed pasteurization to take place at 90 °C for 15 s. The addition of calcium citrate resulted in a significant increase in the pH value of milk and cheese compared to the control sample. Adding 15 and 20 mg of Ca 100 g−1 to milk as citrate had the most beneficial effect on increasing protein retention in cheese in both seasons, showing a rise from 1.33% to 2.40%. The production season significantly influenced the cheese yield. The control goat cheese from the autumn season showed a 6.85% higher yield compared to the spring cheese. An increase in cheese yield was also observed as the calcium dose of milk increased. The content of micro- and microelements in cheese was affected by the production season. The addition of calcium citrate to milk resulted in a significant increase in the calcium content of cheese—from 120.83 to 147.45 mg 100 g−1 in the spring season and from 130.66 to 151.21 mg 100 g−1 in the autumn season. Increasing the dose of calcium increased the hardness of cheese samples by 1.37 N in the spring and 0.90 N in the autumn. The organoleptic evaluation showed that adding calcium to milk did not significantly affect the organoleptic characteristics of goat cheese.

Antimicrobial bioactive peptides from goat Milk proteins: Insilico prediction and analysis.

The main goal of this study was to assess the potential proteins of goat milk (i.e. α-s1-casein, α-s2-casein, β-casein, κ-casein, α-lactoglobulin and β-lactalbumin) as precursors of antimicrobial peptides (AMPs). Bioinformatics tools such as BIOPEP-UWM (enzyme action) were used for the in silico gastrointestinal digestion via a cocktail of pepsin, trypsin, and chymotrypsin A. The antimicrobial activity of peptides was predicted by using four algorithms, including Random Forest, Support Vector Machines, Artificial Neural Network and Discriminant Analysis on CAMPR3 online server, which works on Hidden Markov Models. Different online tools predicted the physiochemical properties, allergenicity, and toxicity of peptides as well. In silico gastrointestinal digestion simulation of proteins by enzymes cocktail yielded a total of 83 potential AMPs, with thirteen peptides being confident by all four algorithms. More AMPs were released from β-casein (21) than from β-lactoglobulin (16), α-s1-casein (15), α-s2-casein (12), κ-casein (11) and α-lactalbumin (9). A total of 17 peptides were cationic, and the majority of the peptides were extended AMPs. These peptides were released from α-s1-casein (SGK, IQK), α-s2-casein (SIR, AIH, TQPK), β-casein (GPVR, AVPQR, AIAR, GVPK, SQPK, PVPQK, IH, VPK), k-casein (AIPPK, QQR, IAK, TVPAK). All of the AMPs were anticipated to be non-toxic, and 54 of the 83 peptides were confirmed to be non-allergic, with the remaining 29 suspected of being allergenic and 31 to be predicted to have good water solubility. Further the molecular docking was used to evaluate the potent dihydropteroate synthase (DHPS) inhibitors. On the basis of ligand binding energy, 17 predicted AMPs were selected and then analyzed by AutoDock tools. Among the 17 AMPs, 3 AMPs were predicted as high-potent antimicrobial. Based on these findings, in silico investigations reveal that proteins of goat milk are a potential source of AMPs. These peptides can be synthesized and improved for use in the food sector. PRACTICAL APPLICATIONS: Goat milk is regarded as a high-quality milk protein source. According to this study, goat milk protein is a possible source of AMPs, and therefore, most important AMPs can be synthesized and developed for use in the food sector.

In silico identification of antidiabetic and hypotensive potential bioactive peptides from the sheep milk proteins-a molecular docking study.

An in silico approach was used for hydrolysis of sheep milk proteins (α-s1, α-s2, β-casein, κ-Cn, α-lactalbumin, and β-lactoglobulin) by gastrointestinal enzymes in order to generate bioactive peptides (BAPs) that can inhibit ACE and DPP-IV. Sheep milk proteins showed higher similarity with goat milk proteins. These data were acquired via the Clustal Omega tool to perform sequence alignment analysis. The BIOPEP-UWM database was used to examine the ability of sheep milk protein sequences to generate BAPs, which included a description of their potential bioactivity as well as the frequency of fragments with specified activities. Using the "Enzyme(s) action" tool (BIOPEP-UWM), digestive enzymes pepsin, trypsin, and chymotrypsin, and three enzyme combinations were selected to computationally hydrolyze milk proteins for obtaining information about ACE and DPP-IV inhibitory peptides. Other online programs were used to test potential peptides for bioactivity, toxicity, and physicochemical properties. BAPs produced from PTC-hydrolyzed proteins were analyzed using a peptide ranker, and their inhibitory effects on ACE and DPP-IV were determined using molecular docking. Consequently, the results of molecular docking analysis show that the peptide PSGAW (αS1-Cn f155-159) binds to DPP-IV with binding energy (-8.9kcal/mol). But in the case of ACE, two potential BAPs were selected: QPPQPL (β-Cn f161-166) and PSGAW. These two BAPs revealed a higher binding affinity for ACE with a binding energy of -9.8kcal/mol. Thus, the results showed that sheep milk proteins were a promising source of antidiabetic and hypotensive peptides. However, experimental and pre-clinical studies are necessary to assay their therapeutic effects. PRACTICAL APPLICATIONS: Sheep milk proteins are known as a high-quality milk protein resource. Effective enzymatic hydrolysis of sheep milk proteins can release bioactive peptides and also release potential ACE and DPP-IV inhibitory peptides. This in silico study specifies a theoretical root for sheep milk proteins as a novel source of potential bioactive peptides and may offer guidance for invitro hydrolysis of proteins for the production of bioactive peptides valuable for human consumption.

Using the dual isotope method to assess cecal amino acid absorption of goat whey protein in rats, a pilot study.

Measurement of ileal amino acids (AA) bioavailability is recommended to evaluate protein quality. A dual isotope tracer method, based on plasma isotopic enrichment ratios, has been proposed to determine true digestibility in humans. In a pilot study, we aimed to evaluate whether this method could be implemented in rats to determine AA bioavailability based on isotopic enrichment ratios measured in cecal digesta or plasma samples. Goat milk proteins were intrinsically labeled with 15N and 2H. Wistar rats were fed a meal containing the doubly labeled goat whey proteins and a tracer dose of 13C-spirulina. Blood samples were collected 0, 1h and 3h after meal ingestion from the tail vein. The rats were euthanized 4h (n = 6) or 6h (n = 6) after meal to collect plasma and intestinal contents. True orocecal protein digestibility and AA bioavailability were assessed by means of 15N and 2H enrichment in cecum content and compared with absorption indexes determined at the plasma or cecum level using isotopic ratios. Plasma kinetics of isotopic enrichment could not be completed due to the limited quantity of plasma obtained with sequential blood collection. However, the absorption indexes determined from cecal 15N or 2H/13C ratios gave coherent values with true orocecal AA bioavailability. This dual isotope approach with measurements of isotopic ratios in digestive content could be an interesting strategy to determine true AA bioavailability in ileal digesta of rats.

Inclusion of Barley Fodder in Alfalfa/Grass-Based Diets on Milk Production in Goats and Milking Sheep

The purpose of this study was to determine the effect of Barley Sprout Fodder (BSF) on milk production and milk composition of Saanen goats and Friesian ewes. Twenty Saanen does (1-year-old) and twenty East Friesian ewes (1 to 5 years old), were selected for this experiment, where each species was divided into four treatment groups. Goat treatments consisted of 0 (CRTL), 758 (BSF1), 1498 (BSF2) and 2270 (BSF3) g wet BSF/d added to an alfalfa/grass hay mix provided in random order. Sheep treatments were similar, but 0, 454, 908, and 1362 g wet BSF/d. The dry matter content of the fodder was 10.7%. A grain mix was fed to the goats (798 DM g/d) and sheep (400 DM g/d) during morning and evening milking. Treatment periods were fifteen days. Feed consumed was measured and milk yield and samples were collected on days 13 and 14. Milk samples were analyzed for milk fat, protein, and lactose. The cheese was made from day 14 milk and milk and cheese were analyzed for fatty acid composition. Total DM intake was between 2.7 and 2.9 kg/d for does and was different (P<0.05) between BSF treatments, 2.6 to 3.0 kg/d for ewes. Milk yield was not affected by BSF treatment. Goat milk yield averaged 2681 g/d across the treatments, while sheep was 1021 g/d. Milk fat content increased numerically from 77 to 82 g/d for goats and 50 to 58 g/d for sheep. BSF did not affect goat milk protein g/d, but sheep milk protein increased from 46 to 53 g/d. Goat milk lactose was not changed with BSF inclusion, while sheep milk lactose increased from 47 to 54 g/d. Total solids were not different from BSF in the diet for goats but was for sheep increasing from 143 to 164 g/d. There were no differences in cheese fatty acid composition for either species. The CRTL diet cost $0.82/day for goats and $0.72/d for sheep, while the high level of BSF inclusion cost $1.06/d for goats and $0.91/d for sheep. Based on the parameters of this study, the inclusion of BSF had relatively no effect on goat milk parameters but did improve milk solids in sheep milk, with no increase in milk yield.

Features of the formation of specific Igg4 antibodies to milk proteins in healthy young children living in different megalopolises of the Russian Federation

Objective: Study specific Igg4 antibodies to milk proteins indexes in healthy babies living in different Russian megalopolises.Methods: The complex research of the specific Igg4 antibodies to milk proteins during cohort study of 259 healthy babies of the first year of life. Children lived in five Russian cities: 60 children in Moscow, 50 newborns – in Saint Petersburg, 55 children came from Kazan, 43 children lived in Khabarovsk and 51 – in Vladivostok. Non-competitive enzyme-linked immunosorbent assay was used to quantify specific Igg4 antibodies to cow milk proteins (CMP), beta-lactoglobulin (β-LG), alpha-lactalbumin (α-LA), casein and goat's milk protein (GM) in coprofiltratesResults: The highest frequency of the high Igg4 was discovered to CMP and goats’ milk was observed among children from Saint Petersburg during comparative assessment of the frequency of defining Igg4 to milk proteins in healthy newborns aged 2.5 months living in Moscow and Saint-Petersburg. The highest frequency of Igg4 increased rates to milk proteins among newborns from Kazan, Khabarovsk and Vladivostok was diagnosed during first three months of life on breastfeeding without any clinical symptoms of food intolerance. With age decrease of the frequency of specific Igg4 to milk proteins were observed among all babies from above-mentioned cities. By 8 month of life it made isolated cases.Conclusions: High frequency of increased Igg4 to milk proteins among 2 months old babies on breastfeeding was observed in the cities of Central and Far Eastern districts of Russian Federation. In this regard it can be supposed that Igg4s were got from mothers in the prenatal period and after birth through breastfeed. The presence of high frequency of the increased indexes of specific Igg4 to milk proteins probably was related to mothers’ nutrition habits during pregnancy and lactation periods.

Особенности сенсибилизации к молочным белкам у здоровых детей раннего возраста, проживающих в разных мегаполисах РФ

There is no clear answer so far, why, under normal conditions, there is no active immune response to food antigens that are supplied daily with food, while oral tolerance develops in a child. A cohort study of 259 healthy children of the first half year of life who lived in different megalopolises of the Russian Federation showed a high frequency of latent (asymptomatic) sensitization (LS) to milk proteins, which was formed under breast feeding. Despite the transfer to bottle feeding, there was a statistically significant decrease in the frequency of LS to cow and goat milk proteins in babies from Moscow by 5 months of age, and in babies from St. Petersburg by 6 months of age. The frequency of LS to casein, β-LG and α-LA in breastfed babies from Vladivostok during the first three months of life was statistically significantly higher than in babies from Kazan and Khabarovsk during the entire observation period. The data obtained indicate that the immune mechanisms forming latent (asymptomatic) sensitization in the observed children were of an indirect nature, and their implementation was a response to the exposure of maternal allergens that entered the baby’s body in the antenatal and postnatal periods.

Influence of aqueous yam extract and goat milk casein powder on the characteristics of goat Greek-style yogurt

This study proposed the production of goat Greek-style yogurt with added aqueous yam extract and goat milk casein powder. Yam brings health benefits when consumed, as it is rich in fiber and antioxidant compounds that help in the treatment of various diseases such as diabetes and cancer, and goat milk proteins are precursors of bioactive peptides that have antioxidant, anti-hypertensive and anti-glycemic action. Furthermore, yam is rich in starch, which, like casein, are components with a recognized hydrocolloid function. So to verify the influence of aqueous yam extract and goat milk casein powder on the physicochemical, technological, microbiological characteristics, and sensory acceptance of goat Greek-style yogurt, four formulations varying the proportion of milk: aqueous yam extract (100:0; 100:0; 90:10; and 80:20) (v/v) and varying the concentration of goat milk casein powder (0%; 2%; 2%; and 2%) (w/v) in relation to the volume of milk plus aqueous yam extract were prepared. The supplementation of goat milk casein powder enhanced the yield, water holding capacity, viscosity, sensory acceptance, and purchase intention score of goat Greek-style yogurt. Meanwhile, the aqueous yam extract reduced grain concentration in the formulation with the proportion of 80:20 milk: aqueous yam extract, and increased viscosity in the formulation with the proportion of 90:10 milk: aqueous yam extract. The results of this study presented the incorporation of the goat milk casein powder and aqueous yam extract as ingredients of a new goat dairy product with nutritional quality, and added market value owing to its potential functional properties.

Effects of different saccharides on the microstructure and functional properties of protein in goat milk during processing

AbstractThis study investigated the changes in the characteristics of goat milk protein in the presence of trehalose, chitooligosaccharide and pectin during two practical dairy processing operations of pasteurisation and spray drying. The highest denaturation temperature and the largest particle size of milk protein were found in goat milk added with pectin after pasteurisation. And particles with more uniform and compact morphology were observed in goat milk protein with these three saccharides. An elevated emulsifying activity index of 24.37 m/g−2 was observed in protein after spray drying due to chitooligosaccharide. And the foam stability was also improved significantly in the presence of trehalose and pectin during pasteurisation. During spray drying, saccharides showed the stabilizing effect on goat milk protein. This study revealed a complex interplay between the type of saccharides and the processing operation applied to goat milk, which might be of great significance for the production and processing of goat milk.

Effects of quantity and source of calcium on the behavior of goat milk after heating and acidification

This study investigated changes in the behavior of goat milk protein and physicochemical characteristics of high-pasteurized goat milk and goat milk yogurt during storage caused by calcium chloride and natural milk calcium addition and decalcification. Compared with the control group, the denaturation temperature of goat milk protein dropped in all the treated groups. The addition of both types of calcium accelerated the transition of goat milk protein from β-sheet to β-turn and random coil structure. But opposite results were found in the decalcification process. Compared with calcium chloride, natural milk calcium showed more positive influence on the stability of high-pasteurized milk during storage. The addition of both types of calcium improved significantly the water-holding capacity of yogurt during 7-day storage, and the natural milk calcium dramatically inhibited the post-acidification of yogurt. This study provides a theoretical basis for further study and the development of calcium-based functional goat milk products.

​Importance of Genetic Polymorphism of Goat Milk Proteins on Human Nutrition and Health: A Review

The objective of the study is impotance of casein protein genetic polymorphism of goat milk. Goat milk is highly digestible and has medicinal properties in human being. Goat milk and its value added dairy products have higher demand in many contries of world. Due to evolution process, much genetic variability has been developed in casein protein genes. This is originatd due to point mutation; addition/deletion and many other factors lead to huge genetic variation in goat casein genes. Because of this goat milk, chemical and biological properties have been affected. Goat milk casein contents decide the cheese making properties as well as nutritional and medicinal values. Goat milk is good alternative source of nutrition in human when people have cow milk problems. Goat milk has humerous inactive bioactive peptides in their casein protein. These have important place for human health and nutrition. In the future, this is great possibility for development of medicinal value functional dairy products from functional bioactive peptides.

Proteomic analysis of differentially expressed whey proteins in Saanen goat milk from different provinces in China using a data-independent acquisition technique

Whey proteins of Saanen goat milk samples from 3 provinces in China (Guangdong, GD; Inner Mongolia, IM; Shaanxi, SX) were characterized and compared using data-independent acquisition quantitative proteomics technique. A total of 550 proteins were quantified in all 3 samples. There were 44, 44, and 33 differentially expressed proteins (DEP) for GD versus IM, GD versus SX, and IM versus SX, respectively. Gene ontology annotation analysis showed that the largest number of DEP for the 3 comparisons were as follows: for biological processes: response to progesterone, glyceraldehyde-3-phosphate metabolic process, and negative regulation of megakaryocyte differentiation; for molecular functions: antioxidant activity, binding, and peroxiredoxin activity; and for cellular components: the same category of extracellular regions for the 3 comparisons, respectively. Pathways for the DEP of 3 comparisons were (1) disease; (2) synthesis and metabolism; and (3) synthesis, degradation, and metabolism. Protein-protein interaction network analysis showed that DEP for GD versus SX had the most interactions.

A High-Throughput Comparative Proteomics of Milk Fat Globule Membrane Reveals Breed and Lactation Stages Specific Variation in Protein Abundance and Functional Differences Between Milk of Saanen Dairy Goat and Holstein Bovine.

Large variations in the bioactivities and composition of milk fat globule membrane (MFGM) proteins were observed between Saanen dairy goat and Holstein bovine at various lactation periods. In the present study, 331, 250, 182, and 248 MFGM proteins were characterized in colostrum and mature milk for the two species by Q-Orbitrap HRMS-based proteomics techniques. KEGG pathway analyses displayed that differentially expressed proteins in colostrum involved in galactose metabolism and an adipogenesis pathway, and the differentially expressed proteins in mature milk associated with lipid metabolism and a PPAR signaling pathway. These results indicated that the types and functions of MFGM proteins in goat and bovine milk were different, and goat milk had a better function of fatty acid metabolism and glucose homeostasis, which can enhance our understanding of MFGM proteins in these two species across different lactation periods, and they provide significant information for the study of lipid metabolism and glycometabolism of goat milk.

Goat milk protein digestibility in relation to intestinal function

ABSTRACTBackgroundMilk is an important high-quality animal protein source in low- and middle-income countries (LMICs). Although the true ileal digestibility and absorption of milk has been shown to be high in French adults, this may be lower in individuals from LMICs who are at risk of environmental enteropathy.ObjectiveTo determine the true ileal indispensable amino acid (IAA) digestibility of intrinsically labeled goat milk protein in South Indian women of reproductive age (WRA), using the dual-isotope tracer technique, and to measure intestinal absorption of amino acid and inert sugar in the same participants using L-allo-isoleucine and a dual-sugar assay.MethodsMilk with 2H-labeled protein collected from a lactating goat fed intrinsically 2H-labeled fodder (maize and cowpea) was spray dried. Labeled milk protein was administered in a plateau feeding protocol to WRA with normal BMI, in whom urinary lactulose and mannitol recovery and the lactulose/mannitol ratio (LMR) were measured, to determine its true ileal IAA digestibility by the dual-isotope tracer technique with a reference U-13C–amino acid mixture. A phenylalanine absorption index was calculated from the plasma to meal ratio of 13C9 phenylalanine within the digestibility protocol. On a separate day, the allo-isoleucine absorption index was estimated from the ratio of plasma allo-isoleucine enrichments after oral 13C6-15N-L- and intravenous 2H10-L-allo-isoleucine administration.ResultsThe means ± SDs of true ileal IAA digestibility of goat milk protein, lactulose and mannitol recovery, LMR, allo-isoleucine and phenylalanine absorption index were 94.0 ± 2.9%, 0.09 ± 0.03%, 7.9 ± 2.3%, 0.012 ± 0.004, 88.4 ± 3.8% and 24.5 ± 1.6%, respectively. The LMR correlated with the allo-isoleucine absorption index (rs = –0.93, P = 0.008).ConclusionThe true ileal digestibility of goat milk protein in South Indian WRA with normal intestinal absorptive function and integrity was comparable to earlier estimates in healthy French adults.

Post translational modifications of milk proteins in geographically diverse goat breeds

Goat milk is a source of nutrition in difficult areas and has lesser allerginicity than cow milk. It is leading in the area for nutraceutical formulation and drug development using goat mammary gland as a bioreactor. Post translational modifications of a protein regulate protein function, biological activity, stabilization and interactions. The protein variants of goat milk from 10 breeds were studied for the post translational modifications by combining highly sensitive 2DE and Q-Exactive LC-MS/MS. Here we observed high levels of post translational modifications in 201 peptides of 120 goat milk proteins. The phosphosites observed for CSN2, CSN1S1, CSN1S2, CSN3 were 11P, 13P, 17P and 6P, respectively in 105 casein phosphopeptides. Whey proteins BLG and LALBA showed 19 and 4 phosphosites respectively. Post translational modification was observed in 45 low abundant non-casein milk proteins mainly associated with signal transduction, immune system, developmental biology and metabolism pathways. Pasp is reported for the first time in 47 sites. The rare conserved peptide sequence of (SSSEE) was observed in αS1 and αS2 casein. The functional roles of identified phosphopeptides included anti-microbial, DPP-IV inhibitory, anti-inflammatory and ACE inhibitory. This is first report from tropics, investigating post translational modifications in casein and non-casein goat milk proteins and studies their interactions.