Ex vivo digestion of carp muscle tissue--ACE inhibitory and antioxidant activities of the obtained hydrolysates.

In the digestive tract of humans, bioactive peptides, i.e. protein fragments impacting the physiological activity of the body, may be released during the digestion of food proteins, including those of fish. The aim of the study was to establish the method of human ex vivo digestion of carp muscle tissue and evaluate the angiotensin I-converting enzyme inhibitory and antioxidant activities of hydrolysates obtained after digestion. It was found that the hydrolysates of carp muscle tissue obtained with the three-stage method of simulated ex vivo digestion showed ACE inhibitory as well as antioxidative activities. It was demonstrated that the degree of hydrolysis depended on the duration of individual stages and the degree of comminution of the examined material. Although the applied gastric juices initiated the process of hydrolysis of carp muscle tissue, the duodenal juices caused a rapid increase in the amount of hydrolysed polypeptide bonds. The antihypertensive and antioxidative activities of the hydrolysates of carp muscle tissue increased together with progressive protein degradation. However, the high degree of protein hydrolysis does not favour an increase in the activity of free radical scavenging. The presented results are an example of the first preliminary screening of the potential health-promoting biological activity of carp muscle tissue in an ex vivo study.

The effect of glycosylation on emulsifying and structural properties of bovine beta-casein.

A number of attempts have been made to improve the functional properties of milk proteins by chemical modifications. One of such modifications is glycosylation which was carried out to determine the effect of covalent binding of glucose molecules to beta-casein (beta CN) on its emulsifying properties. It was found that up to six molecules of glucose were bound to one molecule of beta CN. Glycosylated beta CN produced smaller emulsion droplets than the intact beta CN. Increases in emulsion-forming and -stabilizing properties were observed. A prerequisite of proteins to form emulsions is their adsorption onto oil/water interface. Therefore the secondary structure of intact and glycosylated beta CN, both in solution and adsorbed onto a hydrophobic teflon/water interface also were studied by far-ultra violet circular dichroism (CD). It appeared, that after glycosylation the degree of helicity of intact beta CN decreased and the incorporation of glucose moieties most likely resulted in a type beta-turn formation after adsorption onto the interface.

Dephosphorylation-induced structural changes in beta-casein and its amphiphilic fragment in relation to emulsion properties.

To promote the understanding of the relationship between emulsifying and molecular properties of proteins/peptides, intact beta-casein (betaCN) and its amphipathic fragment, i.e., betaCN (1-105/107) were dephosphorylated. Dephosphorylation was found not to change significantly their emulsifying properties. Since it is known that the structure of proteins can change upon adsorption onto an interface, the secondary structure of intact beta-casein, its amphipathic fragment, and their dephosphorylated forms, both in solution and after adsorption onto a hydrophobic teflon/water interface, were studied by far-UV circular dichroism spectroscopy. An increased content of secondary structure, especially alpha-helix, was found for all samples after adsorption onto teflon. Dephosphorylation increased the helix-forming propensity, especially for amphipathic fragment of beta-casein. No influence of the secondary structure properties on the emulsion-forming and -stabilizing properties was observed, but a relationship between the maximum surface load and the emulsion-stabilizing properties was found.

Some physico-chemical properties and structural changes of bovine beta-casein upon glycation.

The studies on casein structure modification contribute to better understanding of the role of nonamino acid components in forming casein complexes and improving ways of protein functionality. The objective of the experiments was to explain the influence of bovine milk casein glycation on some physico-chemical properties and structural changes. From the the analysis of glycation rate curve the reaction of the first order range can be assumed during the first 24 h, turning to a mixed type afterwards. The isoelectric point and molecular weight of beta-casein increased after glycation and the electrophoretic mobility was slightly modified. The structural changes were also confirmed by different absorption spectra in UV and a better heat stability of the modified beta-casein. The findings showed higher solubility with modified beta-casein. The glycation caused changes in beta-casein, modifying its susceptibility to the trypsin hydrolysis.

[Content of micro- and macro-elements, lead and cadmium in albumins and globulins of fresh and stored, dried seeds of the Faba bean]. / Zawartosc mikro- i makroelementów, olowiu i kadmu w albuminach i globulinach swiezych oraz przechowywanych i suszonych nasion bobiku.

The content of micro/macroelements, lead and cadmium in Faba bean proteins from the seeds after their harvest and from the seeds stored (2 months, 6-8 degrees C) and dried (6h at 35 degrees C up to 15-15% moisture) was determined. Proteins were extracted with water (pH 8.0). Globulins were precipitated from water protein extract at pH 4.2. The microelements (Cu, Mn, Fe and Zn) content in albumins and globulins from the seeds after their harvest and from stored and dried seeds were as follows: 37.4 and 27.1; 46.7 and 35.8; 15.4 and 18.9; 179.2 and 229.7 micrograms/g (albumins) and 24.9 and 31.9; 20.0 and 28.1; 92.1 and 205.4; 68.7 and 102.9 micrograms/g (globulins). These findings indicate that Faba bean albumins and globulins form the labile and neutral nucleo-glycoprotein complexes with Cu, Mn, Fe and Zn. The process of storage and drying caused the migration of the micro and macroelements between albumins and globulins. Generally, one may say that Faba bean albumins and globulins are the source of the biologically active micro- and macroelements.