Obecnie na świecie wzrasta zainteresowanie składnikami bioaktywnymi, w tym peptydami biologicznie aktywnymi. Prekursorami takich peptydów mogą być białka ro-ślinne i zwierzęce, w tym białka mleka (kazeina i białka serwatkowe). Peptydy bioaktywne mogą powstawać w wyniku ograniczonej proteolizy białek zachodzącej podczas różnych procesów technologicznych (np. zastosowanie proteolitycznych kultur starterowych wykorzystywanych do przeprowadzenia fermentacji mleka). W przewodzie pokarmowym człowieka takie związki mogą powstawać podczas hydrolizy białek/peptydów prowadzonej przez enzymy trawienne (pepsynę, trypsynę i chymotrypsy-nę). Peptydy bioaktywne wpływają na funkcjonowanie układu krwionośnego, układu nerwowego i pokarmowego oraz immunologicznego. Peptydy korzystnie wpływające na układ krążenia to peptydy obniżające ciśnienie krwi (peptydy przeciwnadciśnieniowe), hamujące agregację płytek krwi (peptydy przeciwkrzepliwe), zmniejszające rozpuszczalność cholesterolu, co w konsekwencji prowadzi do obniżenia absorpcji jelitowej tego związku (peptydy hipocholesterolemiczne). Zidentyfikowano również peptydy hamujące enzymatyczną (hamowanie lipooksygenazy) i nieenzymatyczną peroksydację niezbędnych kwasów tłuszczowych (peptydy antyoksydacyjne). Peptydy bioak-tywne są składnikami wielu produktów określanymi jako „żywność funkcjonalna” lub „nutraceutyki”.
Tlie aim of the research was to study the effect of heating the water solutions (pH 7.1 ) of the milk protein concentrate obtained with ultrafiltration on the content of nitrogen (N), calcium (Ca) and phosphorus (P) and the composition of proteins in the pellets after the ultracentrifugation of rennet curds (pH 6.6) and acid-rennet curds (pH 6.0). It was found that heating the concentrate solutions did not have any influence on the content of Ca and P in the insoluble fractions of rennet curd. However, it contributed, irrespective of the temperature of heating, to an increase in the share of total N by 0.3% (significant differences at p=0.05). Electrophoretic analysis of the proteins in pellets after ultracentrifugation of the curds indicates that heating to 92°C caused an increase in the share of whey proteins by 1% on average. At the same time, a decrease in the share of ß-lactoglobulin (ß-lg) by 4.7% and BSA + Ig by 2.8% was noted in the proteins of the soluble fraction after ultracentrifugation of the curds. αs- and ß-casein were not found in the soluble fractions. On the other hand, para-K-casein was found (from 2.3% in the unheated substrates to 2.7% in the substrates heated to 92°C). With acid-rennet coagulation heating the substrates at 92°C.contributed to a decrease in the share of Ca and P in the pellets after ultracentrifugation of the curds by 1.8% and 1.7%, respectively, with the unchanged share of total N. The content of ß-lg, α-lactalbumin (α-la) and BSA + Ig in the soluble fractions of the curds in the substrates heated at 92°C decreased by 13.7%, 1.6% and by 3.9%, respectively. Heating the substrates at 92°C contributed to a decrease in the share of para-K-casein in the soluble fractions of acid-rennet curds from 1.7% to 0%. At the same time, it limited the incorporation of dissociated ß-casein into a gel network. Its content in the soluble fraction after ultracentrifugation of the curds increased from 0% in the case of the unheated substrates to 2.7% in those heated to 92°C.
The aim of the research was to study the effect of heating (72°C/15 s, 92°C/60 s) water solutions of milk protein concentrate (pH 7.1), obtained by ultrafiltration, on the enzymatic phase during chymosin activity at 32°C at pH 7.1, 6.6 and 6.0. It was found that heating at 72°C limited the number of peptides released at pH 7.1 by 33.3%, and heating at 92°C - by 25.0%. It was affected by differences in the access of the enzyme to glycosylated K-casein. After reducing pH to 6.6, it was observed that heating both at 72°C and 92°C influenced the limitation of the number of released peptides by 13%. The level of the temperature, however, influenced significant differences in RCT which was longer by 17.0% and 34.0% in the substrates heated to 72°C and 92°C. After reducing pH to 6.0, it was found that heating at 72°C and 92°C limited the number of released peptides by 11.2%. However, significant (p=0.05) elongation of RCT (by 8%) was observed only after heating at 92°C.
The chemical composition, solubility, and dispersity of milk powders obtained from milks with the 10% and 15% additions of whey and rennet coagulation time (RCT), heat and alcohol stability of the reconstituted milk were studied. The change in the proportion between casein and whey proteins in modified milk powders was found to increase the denaturation degree of ß Mactoglobulin. With an increase of the whey addition, the heat and alcohol stability decreased, and solubility index and dispersity of modified milk powders increased. The effect of whey addition on RCT of modified milk powders was different. The correlation (r=-0.99) was found between RCT and weight ratio of calcium to casein nitrogen.
The solubility of sodium coprecipitate in water and in salt solution of the composition corresponding to simulated milk ultrafiltrate was studied at 3000, 8000, 19000 and 110000 g. The molecular state of protein determining its solubility was defined together with the contribution of Ca, Mg, P, K and Na to the formation of this state. The (Ca+Mg)/(Na+K) weight ratio in the protein aggregates insoluble in the salt solution decreased with an increase in gravity. The constant (Ca+Mg)/N weight ratio and protein composition of the protein aggregates insoluble in the salt solution in the gravity ranging from 3000 to 110000 g suggested increased contributions of hydrophobic interactions and covalent bondings in the integration of protein particles as their size increased.
W pracy przeprowadzono analizę in silico w celu oceny reaktywności krzyżowej białek orzecha ziemnego (Arachis hypogaea L.), ze szczególnym uwzględnieniem białka Ara h 9 – markera reaktywności krzyżowej w odniesieniu do białek owoców. Określono możliwość występowania reakcji krzyżowych między różnymi białkami orzecha ziemnego, jak również między białkami orzecha ziemnego a białkami innych alergenów pokarmowych, w tym powszechnie znanych alergenów soi, soczewicy, pomidora, orzecha laskowego, jabłoni zwyczajnej i brzoskwini oraz m.in. chińskiego liczi i daktylowca. Podobieństwo sekwencji epitopów białek orzecha ziemnego na poziomie > 80 %, oceniane na podstawie komputerowych baz danych: UniProtKB i BIOPEP oraz programu EVALLER, stwierdzono głównie w stosunku do epitopów soi, pomidora, orzecha laskowego, jabłoni i brzoskwini.
Background. Proteomic analysis is emerging as a highly useful tool in food research, including studies of food allergies. Two-dimensional gel electrophoresis involving isoelectric focusing and sodium dodecyl sulfate polyacrylamide gel electrophoresis is the most effective method of separating hundreds or even thousands of proteins. In this study, albumin and globulin fractions of pea seeds cv. Ramrod were subjected to proteomic analysis. Selected potentially alergenie proteins were identified based on their molecular weights and isoelectric points. Material and methods. Pea seeds (Pisum sativum L.) cv. Ramrod harvested over a period of two years (Plant Breeding Station in Piaski-Szelejewo) were used in the experiment. The isolated albumins, globulins and legumin and vicilin fractions of globulins were separated by two-dimensional gel electrophoresis. Proteomic images were analysed in the ImageMaster 2D Platinum program with the use of algorithms from the Melanie application. The relative content, isoelectric points and molecular weights were computed for all identified proteins. Electrophoregrams were analysed by matching spot positions from three independent replications. Results. The proteomes of albumins, globulins and legumin and vicilin fractions of globulins produced up to several hundred spots (proteins). Spots most characteristic of a given fraction were identified by Computer analysis and spot matching. The albumin proteome accumulated spots of relatively high intensity over a broad range of pi values of -4.2-8.1 in 3 molecular weight (MW) ranges: I - high molecular-weight albumins with MW of -50-110 kDa, II - average molecular-weight albumins with MW of -20-35 kDa, and III - Iow molecular-weight albumins with MW of-13-17 kDa. 2D gel electrophoregrams revealed the presence of81 characteristic spots, including 24 characteristic of legumin and 14-of vicilin. Conclusions. Two-dimensional gel electrophoresis proved to be a useful tool for identifying pea proteins. Pattems of spots with similar isoelectric points and different molecular weights or spots with different isoelectric points and similar molecular weights play an important role in proteome analysis. The regions characteristic of albumin, globulin and legumin and vicilin fractions of globulin with typical MW and pl values were identified as the results of performed 2D electrophoretic separations of pea proteins. 2D gel electrophoresis of albumins and the vicilin fraction of globulins revealed the presence of 4 and 2 spots, respectively, representing potentially allergenic proteins. They probably corresponded to vicilin fragments synthesized during post-translational modification of the analysed protein.
The aim of this study was to evaluate plots showing a linear correlation between the parameters characterising protein content in the spots obtained using two-dimensional electrophoresis (scatter plots). The correlation coefficient of normalized spot volume may be used to determine regions with increased reproducibility. In our experiment, conducted using pea seed proteins, the correlation coefficient reached 0.980 in such regions, compared with 0.917 noted for the entire gel surface. The correlation coefficient calculated based on scatter plots may serve as a tool for the preliminary selection of regions characteristic of a given proteome.
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