Zs. Csapó-Kiss

Composition of mares' colostrum and milk. Fat content, fatty acid composition and vitamin content

Changes in the fat content, fatty acid composition and vitamin contents of mares colostrum and milk during the flrst 45 days of lactation were studied. Milk samples (300{800 ml) from 29 lactat- ing mares, were collected daily at the beginning of the lactation and weekly from 5 to 45 days postpartum. Colostrum and early milk samples were obtained by hand, without oxytocin administration, while the foal nursed. Later milk samples were from mixed milk of the totally-milked udder. Each sample was analysed for total solids, fat content, fatty acid

Composition of mares' colostrum and milk. Protein content, amino acid composition and contents of macro- and micro-elements

Changes in the protein content, protein fractions and amino acid composition of mares colostrum and milk, and biological value of milk protein during the flrst 45 days of lactation were studied. Milk samples (averaging 300{800 cm 3 ) from 29 lactating mares were collected daily at the beginning of the lactation and weekly from the 5 th to 45 th days post-partum. Colostrum samples were obtained by hand milking without oxytocin administration, while the foals nursed and milk samples

USE OF AMINO ACIDS AND THEIR RACEMISATION FOR AGE DETERMINATION IN ARCHAEOMETRY

Abstract After reviewing previous attempts to use the extent of amino acid racemisation (AAR) for the determination of the age of archaeological samples containing proteins, the authors describe their own approach. Following an optimised protein hydrolysis with low racemisation the d - and l -amino acid content in fossil bone samples of known age (radiocarbon method) was determined by HPLC after precolumn derivatisation. Based on the obtained half-lives of racemisation and plotting the d / l ratio as a function of time for various amino acids, calibration curves are obtained which can be used for the age determination of fossil bone samples in the range of 2000–500 000 years. Another method is presented for the determination of age of textiles in the range of 100–1800 years. This method is based on the determination by an amino acid analyser of the age-dependent alteration of amino acid composition of proteins. Cystine, methionine and tyrosine content decreases, while cysteic acid content increases with age. Prediction equations were developed as linear regressions of the age of wool based on cysteic acid, cystine and tyrosine contents.

Quantitative determination of protein of bacterial origin

Abstract Several methods have been developed for the determination of the proportion of nitrogen-containing substances of microbial origin in the digestive tracts of cattle. These include assays that use nucleic acids and adenosine triphosphate as indicators, radioisotopes 35 S, 15 N, 32 P and 33 P incorporated into bacterial protein and phospholipids, duodenal amino acid composition with amino-ethylphosphonic acid, diaminopimelic acid and d -alanine ( d -Ala) contents as indicators. On the basis of the data in the literature on d -amino acid content of milk and milk products the authors came to the conclusion that d -glutamic acid ( d -Glu) and d -aspartic acid ( d -Asp) can be considered as markers for proteins of bacterial origin. To demonstrate this, experiments have been carried out and some of the results are reported here.

Separation of D- and L-amino acids by ion exchange column chromatography in the form of alanyl dipeptides

SummaryA method of ion exchange column chromatography was developed for the determination of D- and L-amino acids in the form of diastereomeric dipeptide. First the protein containing samples were hydrolyzed with 6 molar hydrochloric acid, then the single amino acids were separated in an LKB automated amino acid analyzer with the LKB fraction collector. Following lyophilization, the single amino acids were transformed into alanyl dipeptides with tertiary-butyloxycarbonil-L-alanine-N-hydroxy-succinimide (t-BOC-L-Ala-ONSu) active ester. The alanyl dipeptides were easily separated from one another and the initial amino acids. Determination of the D- and L-amino acids in this form is relatively accurate and reproducible but takes some time (33–38 min). Accuracy of the determination is satisfactory. The coefficient of variation amounts to 3–5%. The use of the method is suggested to laboratories having an amino acid analyzer and wish to determine D-and L-amino acids in synthetic-amino acids complements, peptides or natural materials.

Quantitative determination of protein of bacterial origin on the basis ofd-aspartic acid andd-glutamic acid content

SummaryIn recent decades several methods have been developed for determination of the proportion of nitrogen-containing substances passed from the rumen into the abomasum, or small intestine, which are of microbial origin. Recently, when examining thed-amino acid content of foodstuffs, particularly milk and milk products, it was observed that, in addition tod-alanine (d-Ala,d-glutamic acid (d-Glu) andd-aspartic acid (d-Asp) can also be detected in similar quantities, primarily in products which have links with bacterial activity. This gave rise to the idea of examining the diaminopimelic acid (DAPA),d-Glu, andd-Asp content of bacteria extracted from the rumen of cattle, and that of chyme from the same cattle, to establish whetherd-Asp andd-Glu can be used to estimate protein of bacterial origin.The investigations performed have provided evidence that bothd-Asp andd-Glu might be appropriate for determination of protein of bacterial origin. The results obtained using these two bacterial markers (d-Asp andd-Glu) proved to the approximately 10% lower than those obtained using DAPA; this was not because of to error attributable to the new markers but rather to the unreliability of determination using DAPA Analyses performed on samples of known bacterial protein content indicate thatd-Asp andd-Glu gave almost identical results for bacterial protein content which were very close to the theoretical (calculated) values.