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Właściwości i zastosowanie lewanu

81%
Lewan jest wielkocząsteczkowym β-(2→6)-fraktofuranozylo-fruktanem z β-(2→1) terminalną resztą przyłączoną do α-glukopiranozy. Wiedza o występowaniu, biosyntezie i właściwościach tego fruktanu jest obszerna. Wyniki badań wskazują na duży aplikacyjny potencjał lewanu i produktów jego hydrolizy w obszarze żywności o właściwościach prozdrowotnych. Głównymi czynnikami ograniczającymi zastosowanie lewanu w żywieniu jest jego dostępność i brak jednoznacznych wyników dotyczących kompleksowego oddziaływania lewanu na organizm człowieka i/lub zwierząt doświadczalnych. Praca jest studium dotyczącym wskaźników prozdrowotnego działania lewanu i niektórych lewanooligosacharydów. Dokonano również przeglądu możliwości zastosowania lewanu.
Levan – as a fructose homopolymer – because of its physicochemical properties as well as physiological effect on the human organism, has been the subject of numerous research. The aim of this study was to investigate the course of the synthesis of this polymer with the addition of crude enzymatic preparation isolated from the cell-free culture liquid of the Bacillus subtilis DSM 347 bacterium. Saccharose was the donor of fructofuranosyl residues. The effects of some metal ions during synthesis were determined. The innovation in these experiments was the usage of Candida cacaoi DSM 2226 yeasts which were introduced into the dialysing membrane (situated in reaction mixture). The yeasts selectively removed glucose from the reaction media because this mono-sugar is considered as an inhibitor of levansucrase. It was found that the decrease of glucose concentration in the medium by 16-19% resulted in the increased degree of levan polymerisation (by 6 to 9%) and efficiency of levan synthesis (by 9 to 11%). The isolated preparation of levansucrase showed high stability during 140 h synthesis at 37°C which allowed to achieve a compromise between the quantity of released glucose in time and the possibilities of Candida cacaoi DSM 2226 yeast to utilise that free glucose. The Mn2+ ions (at a concentration of 2.5 mmol/L) activated levansucrase (twice increased the initial transferase rate of enzyme) and in reaction medium supplemented with that metal ions the efficiency of levan synthesis increased up to 39%. Associated action of levansucrase and yeasts in the presence of Mn2+ effected in the increase of levan synthesis efficiency to 64%.
The tested strain of Bacillus subtilis DSM 347 was employed in investigations determining the impact of temperature and saccharose concentrations on the in vivo yield of levan synthesis. The best results were obtained in the treatment at 15% saccharose supplementation at 37°C. The obtained levan was subjected to acid and enzymatic hydrolysis and the composition of hydrolysates was examined using the spectrophotometric and densitometric methods on TLC plates.
Introduction. The E 1450 sodium salt of starch octenylsuccinate which exhibits emulsifying properties is used as food additive and is also recommended as yolk replacer in the process of mayonnaise production. Commercial E 1450 preparations reveal excellent functional properties in mayonnaise production. However, sodium salt of starch octenylsuccinate produced in the course of the suspension process (as well as the product of its hydrolysis in a membrane reactor), despite high surface activity, is unsuitable for this purpose. Therefore, a hypothesis was put forward that the cause of the unsuitability of these preparations for mayonnaise production is their improper profile of molecular mass distribution and the objective of this study was to verify the above thesis. Material and methods. E 1450 preparations of different degree of substitution obtained altemately by means of reactive extrusion or enzymatic hydrolysis preceded by esterification in suspension were investigated. Preparations were characterised physico-chemically by determining the degree of substitution, viscosity, emulsifying activity index (EAI) and their capability to stabilise model emulsions (ME). Their molecular mass distribution profiles were determined and their suitability for the manufacture of low-fat mayonnaises was assessed. These investigations were also carried out for mixtures of preparations obtained as a result of a reactive extrusion and hydrolysis of the ester obtained during the suspension process. Results. Despite the fact that the preparations obtained in suspension were characterised by 100% values of the ES parameter, all attempts to manufacture with their assistance of mayonnaise by way of a simple substitution in the formulation of dried egg yolk by E 1450 starch failed. Similarly, attempts to manufacture mayonnaise using any of the preparations obtained by means of reactive extrusion or enzymatic hydrolysis of the reaction product in suspension also ended in failure. The only successful solution was the application of equilibrium mixtures of E 1450 preparations obtained by way of reactive extrusion with a hydrolisate. Conclusion. The performed investigations fully corroborated the correctness of the proposed hypothesis that the suitability of the starch octenylsuccinate sodium salt as an emulsifier for low-fat mayonnaises is associated with the appropriately high polydispersify of this polymer.
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