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We determine the effects of the technology of obtaining potato protein preparation and of different variants of enzymatic hydrolysis on the chemical and amino acid compositions of the hydrolysates obtained. Potato protein concentrates obtained through their thermal coagulation in potato juice with calcium chloride, calcium lactate or without salt addition were subjected to enzymatic hydrolysis using two commercial hydrolytic enzymes: endopeptidase (Alcalase) and exopeptidase (Flavourzyme). Chemical (contents of ash, total and coagulable protein) and amino acid compositions of the hydrolysates obtained were determined. On the ground of the findings it was stated that the type of potato protein preparation used and conditions of enzymatic modification influenced on the properties of the hydrolysates obtained. Preparations obtained during the study were characterised by similar chemical and amino acid compositions, whereas the preparation obtained through thermal coagulation with the use of calcium lactate contained insignificantly more protein and essential amino acids. The least liable to enzymatic hydrolysis was the preparation obtained by using calcium chloride, particularly when only endopeptidase was used. The application of endopeptidase enzyme enabled to obtain 60% of proteolysis efficiency and the addition of the second enzyme (exopeptidase) to the protein solution insignificantly increased the proteolysis efficiency (to ca 70%), mainly when the preparation coagulated with the use of calcium chloride was hydrolysed. Proteolysis of the protein preparations obtained with the use of two enzymes was more favourable, particularly due to the quantity of free amino acids in and amino acids composition of the hydrolysates.

Healthy Holstein-Friesian cows (n=22, parity: 2-4) were subjected to an intravenous glucose tolerance test 10-15 days after calving. AluI genotype of growth hormone, several plasma metabolites and metabolic hormones were determined, and current and previous lactation yields were recorded. We also used the Revised Quantitative Insulin Sensitivity Check Index (RQUICKI) and its modified version (RQUICKIBHB) for the estimation of peripheral insulin sensitivity. Eighteen cows were leucine homozygous (LL), four were heterozygous (LV). AluI polymorphism was not associated with any of the calculated glucose and leptin indicators of the intravenous glucose tolerance test. LV cows were prone to higher basal insulin levels, longer time to reach half of the maximal and basal insulin concentrations and larger insulin area under the curve. Both RQUICKI and RQUICKIBHB estimated decreased insulin sensitivity in LV compared to LL cows. Higher plasma NEFA and BHB levels accounted for slower glucose disappearance and lower insulin release and insulin clearance rate. Average yield was inversely related to glucose area under the curve and time to reach baseline concentration. Plasma cortisol lowered glucose clearance rate and prolonged time to reach basal levels. More weight loss was associated with higher glucose peak and prolonged glucose disappearance time. All cows became cyclic and showed signs of estrus. There were no differences between LL and LV animals in the onset of ovarian activity and in the time of first observed estrus. We conclude that Holstein-Friesian cows heterozygous for AluI polymorphism of the growth hormone gene may be more likely to develop insulin resistance during early lactation than leucine homozygous cows.

The aim of this study was to examine the physicochemical properties and amino acid composition of rabbit meat after the enrichment of rabbit diet with oregano, sage, and Eleutherococcus senticosus extracts, and to make a comparison with the commercial product XTRACT and control samples. The addition of oregano and sage extracts as well as El. senticosus in the rabbit diet positively influenced the physicochemical properties of rabbit meat by increasing its energy value (P less than 0.05 - sage). Supplementing rabbits feed with oregano and sage extracts led to an improvement of the amino acid composition (P less than 0.01). These findings are also supported by the good health state of rabbits. The diet enriched with the plant extracts is beneficial for the health state of rabbits and the nutritional quality of rabbit meat.

Amino acid composition of the meats of wild and farm pheasants were compared. The following amino acids were determined: Asp, Thr, Ser, Glu, Pro, Gly, Ala, Val, Ile, Leu, Tyr, Phe, His, Lys, Arg. An improved amino acid profile was found in the breast muscle of pheasants kept at the farm in comparison with that of wild pheasants.

Changes in amino acid composition of alfalfa (Medicago sativa L.) phloem sap were studied in response to a water deficit. Sap was collected by stylectomy. As the leaf water potential decreased from -0.4 to -2.0 MPa, there was a significant increase of the total amino acid concentration, due to that of some amino acids: proline, valine, isoleucine, leucine, glutamic acid, aspartic acid, and threonine. Asparagine concentration, which is the main amino acid assayed in the phloem sap of alfalfa (it accounts for 70% of the total content), did not vary with the plant water status. The other amino acid concentrations remained stable as leaf water potential varied; in particular, gamma-amino butyric acid concentration remained unchanged, whereas it varied in response to wounding. The more striking change in the sieve tubes was the accumulation of proline which was observed below a leaf water potential threshold value of about -0.9 MPa (concentration x60 for a decrease of leaf water potential from -0.9 to -2.0 MPa). The role of such changes in phloem sap amino acid concentration in osmotic adjustment of growing tissues is discussed

High performance liquid chromatography (HPLC) method with the pre-column derivatisation by AccQ.Tag agent and following determination of these derivates after their separation in reverse phase column followed by fluorescent detection was used for the determination of amino acids in cheeses. The contents of sixteen free amino acids in twenty five cheeses commercially available in the Czech Republic were measured. The total content of free amino acids in the studied cheeses varied in the range from 27 g/kg to 160 g/kg. Among individual amino acids, seven amino acids were more concentrated in all cheese samples and came from three distinctive taste groups: bitter tasting amino acids (leucine, lysine, and phenylalanine), bitter sweet amino acids (proline and valine), and salty-umami amino acids (glutamic acid and aspartic acid). The differences in the contents of the total and individual free amino acids were influenced by the kind of cheese and mainly by the duration and intensity of proteolysis.

This review article gives a survey of principal pathways that lead to the biosynthesis of the proteinogenic amino acids of the alanine-valine-leucine group starting with pyruvic acid from the glycolytic pathway and serine-cysteine-glycine group starting with 3-phospho-D-glyceric acid from the glycolytic pathway. A survey is further given to the aromatic and heterocyclic amino acids (phenylalanine, tyrosine, tryptophan, histidine) starting with 3-phosphoenolpyruvic acid from the glycolytic pathway and D-erythrose 4-phosphate, an intermediate in the pentose phosphate cycle and Calvin cycle.

The relative proportions of free amino acids as well as the amino acid compositions of hydrolysed unprecipitated peptides and hydrolysed whole carcasses were quantified for two aphid species: the gall-dwelling social aphid Pemphigus spyrothecae and the pea aphid Acyrthosiphon pisum. The whole-tissue amino acid profiles of the two taxonomically distant species had a surprisingly high level of correspondence. In contrast, when comparing the A. pisum profiles obtained in the current study to those obtained in an earlier study, major differences were identified. It is concluded that there are good prospects for developing an artificial diet for P. spyrothecae. There may also exist considerable scope for tailoring the existing diets of A. pisum to suit specialised populations which develop poorly on the standard diet. The amino acid profile of P. spyrothecae is the first such profile that has been reported for a gall-forming aphid.

The objective of this work was to verify the effect of the lean meat proportion (LMP) on the chemical composition of the meaty parts (loin and ham) of pork. A total of 116 hybrid pigs commonly used in the Czech Republic were fattened for this purpose. The pigs were divided according to the lean meat proportion criterion into 3 groups, i.e. more than 60.0%, 55.0-59.9% and 50.0-54.9%. Representative muscle samples were taken from the right halves of these pigs. They were then homogenised and submitted to chemical analysis. The values of water content, intramuscular fat (IMF), crude proteins, and ash matter were as follows: in the loin: 72.50-72.80%, 1.56-1.96%, 23.20-23.40%, and 1.37-1.40%, respectively, in the ham: 70.43-71.59%, 3.52-4.26%, 21.67-21.95%, and 1.42-1.56%, respectively. The higher the LMP, the lower the IMF content. The ash content increased with increasing LMP. The analyses of amino acid composition of musculus longissimus lumborum et thoracis (MLLT) and musculus semimembranosus (MS) showed that when the LMP increased, threonine, isoleucine, lysine, aspartic acid, serine, and proline concentrations in MLLT decreased, whereas valine, isoleucine, phenylalanine, lysine, serine, proline, and glycine conc. in MS increased. The values of IMF in MLLT, water content, IMF, ash matter, threonine, valine, phenylalanine, lysine, aspartic acid, serine, glycine, and alanine in MS differed significantly among the groups studied.