Goat Casein Research Articles

Reverse-phase HPLC analysis of goat caseins. Identification of αs1 and αS2 genetic variants

Summary - Separation of caprine asr, aS2-' 13-and x-caselns was achieved by a simple and reliable HPLC method, using a reverse-phase C4 column and water/acetonitrilelTFA as solven!. Identification of the fractions separated by this method was performed by both alkaline PAGE and SOS-PAGE, and confirmed by analyses of purified casein fractions, prepared using cation-exchange chromatography. Analysis of individual milk from goats homozygous at the as'- and aS2-Cnloci revealed that most of the asrcasein variants (A, B, C, D, F) and the null phenotype, as weil as as2-casein variants A and B are distinguishable. In addition, our method permits the separation of caseinomacropeptide and para x-caseln,

Quantification of αs1-Casein in Goat Milk from French-Alpine and Anglo-Nubian Breeds Using Reversed-Phase High Performance Liquid Chromatography

Samples of isoelectrically precipitated goat casein from the milks of French-Alpine and Anglo-Nubian breeds were separated into four components in a single run by reversed-phase HPLC. The proportion of αs1-casein thus resolved was determined quantitatively. The method uses a reversed-phase C-4 column and a linear gradient from 30 to 50% acetonitrile in 30min with trifluoroacetic acid constant at .1%. Sodium dodecyl sulfate-PAGE was carried out to establish the identity of the isolated components. By a comparison with previously published results for caprine and bovine milk caseins, the four peaks were identified as κ-, αs2-, αs1-, and β- casein.Quantitative variations in the chromatographically resolved αs1-casein fraction of goat milk were evident. Some individual goat milks contained high levels of αs1-casein (2.70g/L), but others contained significantly low levels (.12 g/ L). There was no statistical difference in the overall means between breeds in αs1-casein composition, but cluster analysis statistics showed three distinct categories of αs1-producers: high, medium, and low. Interestingly, 6 of 15 French-Alpine goats and only one Anglo-Nubian goat fell into the “low” producer category (.38±.2g/L). Thus, expression of the αs1- component may be genetically regulated but may not be a breed-specific trait.

Tryptophan determination of food proteins by h.p.l.c. after alkaline hydrolysis

AbstractThe alkaline hydrolysis of proteins prior to tryptophan analysis has been evaluated, and a method for the measurement of tryptophan by reverse phase h.p.l.c. after alkaline hydrolysis has been proposed and compared with published methods. Hydrolysis with either LiOH or NaOH gave similar results. Tryptophan values and the recovery of added 5‐methyltryptophan were similar when hydrolysis was made under tap‐water vacuum (1500 Pa) or at high vacuum (2 Pa). Partially‐hydrolysed starch reduced the losses of tryptophan during hydrolysis better than thiodiglycol. High levels of indolyl‐3‐propionic acid or 5‐methyltryptophan did not further improve tryptophan recovery. 5‐Methyltryptophan is the preferred internal standard; its recovery after hydrolysis more closely resembled that of protein‐bound tritiated tryptophan from goat casein than did the recoveries of α‐methyltryptophan or free 14C‐tryptophan. Under some conditions, the recovery of protein bound tryptophan was lower than the recovery of free tryptophan. The stability of tryptophan in hydrolysates was improved by using a phosphate buffer pH 7.0 containing 0.02% sodium azide.

Utilization in Rats of14C-L-Lysine-labeled Casein Browned by Amino-carbonyl Reaction

The investigation was carried out in order to elucidate the reason for the reduction in nutritive value of browned protein, by using labeled casein as a model protein. Goat casein preparation in which lysine residues had been labeled with 14C was browned by amino-carbonyl reaction with glucose at 37°C. Browned or non-browned casein was ingested by growing rats by spaced feeding. When the rats ingested the browned casein the experimental group, higher radioactivity was found in TCA-soluble fraction in the small intestine as compared with that in the control group, while radioactivity was scarecely found in feces for 22 hr. Along with absorption delay, considerably high radioactivity was found in urine. The recovery of radioactivity in expired air of rats fed the labeled casein (browned and non-browned) was measured. In the experimental group, expired 14CO2 came out slower than the control group. From these results, it is suggested that the main reason for the reduction in nutritive value by browning reaction may be the formation of a lysine derivative in a protein, which remains in the small intestinal lumen as an absorption-delayed material and is finally excreted in urine.

Studies on the nutrition of browned protein. I. Utilization in rats of 14C-L-lysine-labeled casein browned by amino-carbonyl reaction.

The investigation was carried out in order to elucidate the reason for the reduction in nutritive value of browned protein, by using labeled casein as a model protein. Goat casein preparation in which lysine residues had been labeled with 14C was browned by amino-carbonyl reaction with glucose at 37°C. Browned or non-browned casein was ingested by growing rats by spaced feeding. When the rats ingested the browned casein the experimental group, higher radioactivity was found in TCA-soluble fraction in the small intestine as compared with that in the control group, while radioactivity was scarecely found in feces for 22 hr. Along with absorption delay, considerably high radioactivity was found in urine. The recovery of radioactivity in expired air of rats fed the labeled casein (browned and non-browned) was measured. In the experimental group, expired 14CO2 came out slower than the control group. From these results, it is suggested that the main reason for the reduction in nutritive value by browning reaction may be the formation of a lysine derivative in a protein, which remains in the small intestinal lumen as an absorption-delayed material and is finally excreted in urine.

Allergenicity of cow's milk proteins: IV. Relationship to goat's milk proteins as studied by serum-agar precipitation

Summary Double-gel-diffusion precipitation analysis of the relationship between cow's and goat's milk reveals: 1. Cow's milk and goat's milk casein have precipitin patterns of almost complete identity with each other. This tends to confirm previous opinions that goat's casein is closely related to cow's casein, antigenically. 2. Although it had been generally accepted that the whey proteins of the goat and cow are species specific, our precipitation-in-gel experiments indicate that goat's lactoglobulin and lactalbumin are immunologically related to bovine lactoglobulin and lactalbumin. 3. Our experiments cast doubt on the value of substituting raw goat's milk for cow's milk preparations in the treatment of infants and children allergic to cow's milk.

Inhomogeneity of alpha-casein from goat milk.

IT is now known that α-casein from cow milk, which appears electrophoretically homogeneous under many different conditions, consists of at least two compounds which have been designated α- and k-casein1. α-Casein from goat milk, which has similar properties to that from cow milk2 and the same phosphorus content3, showed signs of inhomogeneity during electrophoresis by the moving-boundary method2. Using zone electrophoresis on filter paper it has now been found that the α-component of freshly prepared goat casein does consist of at least two electrophoretically distinct fractions which, until further characterization, will be called α1- and α2-casein in order of decreasing electrophoretic mobility.

A comparison of the electrophoretic patterns of cow, goat and rabbit casein.

DURING the course of some work involving the fractionation of proteins from goat milk, we have found a marked difference between the electrophoretic patterns obtained with goat-milk and cow-milk casein.

Sensitivity to casein in infantile eczema confirmed by biologic titration of the testing extract

T HE antigenic power of casein is not diminished by heat.‘> 2 Cow b and goat casein are immunologically identical or almost identical 3, 4, 5 I . The presence or absence of hypersensitivity to casein in milksensitive persons is, therefore, of considerable practical importance, for if it is present, heated cow’s milk or goat’s milk would not be indicated in dietetic treatment, as Anderson, Schloss, and Stuart3 suggested in 1932. It is certain that lactalbumin is immunologically far more important th,an casein. Little attention has been paid to the latter by allergists. Some have even doubted that hypersensitivity to casein exists. Inasmuch as it is originally in colloida,l solution and is then coagulated in the stomach, while most of the laa when the casein

THE BIOLOGIC RELATIONSHIP BETWEEN COW'S, GOAT'S AND HUMAN CASEINS

Clinical observations indicate the possibility that there is an immunologic relationship between human, cow's and goat's milks. It is a matter of common experience that eczema and other manifestations of hypersensitiveness in the nursing baby are frequently aggravated by the addition of cow's milk, and conversely that eczema in the milk-sensitized infant is unrelieved by reverting to human milk or by the substitution of goat's milk. The work of Fleischer1Bauer,2Wells3and von Versell4suggested that this interrelationship may reside in a biologic similarity of the caseins of the three milks. The establishment of this fact seemed to be of sufficient importance, because of its practical application, to warrant further investigation. With this end in view, we undertook a series of experiments in which we used purified cow's, human and goat's caseins. The results of this work form the basis of the present communication. The