PROCJENA NEAKTIVNOSTI PROTUHRANJIVIH ČIMBENIKA OSJETLJIVIH NA TOPLINU U PUNOMASNOJ SOJI

The regular quality control on the adequacy of heat treatment of fullfat soybeans requires the application of rapid chemical methods. In the present work the trypsin inhibitor activity test and the urease test were applied on fullfat soya samples that were cooked in a pressured steam (toasted) or extruded at different temperatures and speed rates. In the case of toasting both of the results of the laboratory examinations proved that the heating was adequate, while in the case of the extruded samples the two tests gave different results. In the case of certain temperature and time combinations the more rapid and less accurate urease test claimed that the heat treatment reached the aim, while the results of the trypsin inhibitor activity test showed that the level of the inhibitors was still high and the fullfat soya was underheated.Redovita kontrola kakvoće primjerenosti toplinskog tretiranja punomasne soje zahtijeva primjenu brzih kemijskih metoda. U ovom radu primijenjeni su test aktivnosti inhibitora tripsina i test ureaze na uzorcima punomasne soje kuhane u pari pod pritiskom (tostirane) ili ekstrudirane na različitim temperaturama i brzinama. U slučaju tostiranja oba rezultata laboratorijskih ispitivanja su dokazala da je grijanje bilo primjereno, dok su u slučaju ekstrudiranja uzoraka oba testa dala različite rezultate. U slučaju određene temperature i vremenske kombinacije brzi i manje točan test ureaze potvrdio je da je toplinsko tretiranje postiglo svrhu dok su rezultati testa aktivnosti inhibitora tripsina pokazali da je razina inhibitora još uvijek visoka, a punomasna soja nedovoljno zagrijana

Hydrolysis of proteins performed at high temperatures and for short times with reduced racemization, in order to determine the enantiomers of D-and L-amino acids

Abstract. Racemization of free amino acids is considerably lower than that of amino acids bound in peptide. In the same experimental conditions, the rate of racemization of free amino acids is only 20-80% of that of peptide bound amino acids. When using to traditional protein hydrolysis, racemization was 1.2-1.6 times as high as that obtained at high temperatures (160-180 • C), under conditions ensuring total hydrolysis of the protein. This lower degree of racemization may be explained by the fact that, at high temperatures, the protein hydrolyses more rapidly into Key words and phrases: sample preparation; protein hydrolysis; racemization; amino acids, tryptophan, determination of D-amino acids 31 32 J. Csapó et al. free amino acids and the racemization of free amino acids is considerably slower that of amino acids bound in polypeptides. When hydrolysis is conducted at lower temperatures for longer times, the amino acids bound in the peptide chain are exposed for a longer time to the effects actually causing racemization. As a result, we may say that any factor which speeds up hydrolysis, will lower the degree of racemization. Racemization was higher for proteins in milk powder than for pure proteins. This may be explained by catalysis of racemization by the heavy metals present. After 48 hours at 110 • C and in presence of 4 M barium hydroxide, all amino acids (whether free or bound in peptide) totally racemized. Therefore the racemization of tryptophan cannot be determined using barium hydroxide promoted protein hydrolysis. High temperature hydrolysis (at 160 • C for 45 to 60 minutes, at 170 • C for 30-45 minutes and 180 • C for 30 minutes) are recommended for those who would like to hydrolyse the protein for short times and to determine the degree of racemization occurring in the polypeptide chain, but do not wish to use enzyme hydrolysis

Enhanced transmission versus localization of a light pulse by a subwavelength metal slit: Can the pulse have both characteristics?

The existence of resonant enhanced transmission and collimation of light waves by subwavelength slits in metal films [for example, see T.W. Ebbesen et al., Nature (London) 391, 667 (1998) and H.J. Lezec et al., Science, 297, 820 (2002)] leads to the basic question: Can a light be enhanced and simultaneously localized in space and time by a subwavelength slit? To address this question, the spatial distribution of the energy flux of an ultrashort (femtosecond) wave-packet diffracted by a subwavelength (nanometer-size) slit was analyzed by using the conventional approach based on the Neerhoff and Mur solution of Maxwell's equations. The results show that a light can be enhanced by orders of magnitude and simultaneously localized in the near-field diffraction zone at the nm- and fs-scales. Possible applications in nanophotonics are discussed.Comment: 5 figure

NOVE MOGUĆNOSTI ZA ODREĐIVANJE ENANTIOMERA TRIPTOFANA

Diastereoisomers of L- and D-tryptophan were formed with a chiral reagent 1-thio-Dijastereoizomeri L. i D-triptofana formirali su se s kiralnira reagensom L-thio- -D tetracetatom glukoze (TATG) io-phthaldialdehidom (OPA) te su odvojeni od derivata drugih aminokiselina, što se nalaze u bjelančevinama u hrani, u kiralnom stupcu (vrlo djelotvorne) tekuće kromatografije visoke performance. Merkaptoetansulfonična kiselina, odgovarajući agens za hidrolizu bjelančevina, onemogućila je derivaciju OPA/TATG suprotno reakciji dovršenoj u prisutnosti p-toluenlulfonske kiseline. Za vrijeme vrenja racemizacija triptofana mogla se uočiti nakon 12 sati iznad pH=9, ali stopa konverzije bila je niža od očekivane (<1%). Smanjenje koncentracije Ltriptofana nakon 24 sata bilo je 2 do 5%, ovisno o pH. Osim racemizacije druge su reakcije, npr. slabljenje oksidacije, mogle igrati ulogu u gubitku L-triptofan

Gas chromatographic analysis of conjugated linoleic acidś

Abstract. The aim was to determine the conjugated linoleic acids in beef with GC-FID. Perfect separation of all of the isomers cannot be achieved, though conjugated linoleic acid isomers proved to be separable from the other fatty acids that are present in beef in a significant amount related to conjugated linoleic acids. Lipid-extraction was carried out with n-hexane/i-propanol, giving 6.8 percent higher yield than Soxhlet extraction. The variance -due to different parts of the sample preparation process -was quantified. The accuracy of the whole process and the efficiency of triglyceride conversion/fatty acid methyl ester extraction were determined

SEPARIRANJE I ODREĐIVANJE ENANTIOMERA AMINOKISELINA KOJE SADRŽE SUMPOR POMOĆU TEKUĆE KROMATOGRAFIJE VISOKE PERFORMANCE

Performic acid oxidation of cysteine and methionine resulting in the formation of cysteic acid and methionine sulphon has been applied in order to avoid the loss of these two sulphur containing amino acids during the acidic hydrolysis of proteins that is necessary prior to amino acid analysis. The aim of the research was assigned by the increasing demand for the determination of the amount of amino acid enantiomers: the applicability of performic acid oxidation was evaluated from this point of view. Racemization of L-cysteine and L-methionine was found not significant during oxidation with performic acid, therefore this process can be applied before hydrolysis during quantification of cysteine and methionine enantiomers. Additionally, the quantification of cysteic acid and methionine sulphon enantiomers was accomplished in the form of their diastereoisomer derivatives via the development of a reversed phase of high performance liquid chromatography method.Proces oksidacije performičnom kiselinom cisteina i metionina, što rezultira stvaranjem cisteične kiseline i sulfona metionina primijenjen je kako bi se izbjegao gubitak te dvije aminokiseline koje sadrže sumpor, za vrijeme acidične hidrolize bjelančevina, potrebne prije analize aminokiselina. Cilj istraživanja potakli su sve veći zahtjevi za određivanjem količina enantiomera aminokiselina: primjenjivost oksidacije performične kiseline ocijenjena je s tog gledišta. Racemizacija L-cisteina i L-metionina nije se pokazala značajnom za vrijeme oksidacije s performičnom kiselinom pa se, stoga, taj proces može primijeniti prije hidrolize tijekom kvantifikacije cisteinskih i metioninskih enantiomera. Osim toga, kvantifikacija cisteične kiseline i enantiomera metionskog sulfona izvedena je u obliku derivata njihovih dijastereosomera putem razvoja obrnute faze metode tekuće kromatografije visoke performance

Micro droplet formation towards continuous nanoparticles synthesis

In this paper, micro droplets are generated in a microfluidic focusing contactor and then they move sequentially in a free-flowing mode (no wall contact). For this purpose, two different micro-flow glass devices (hydrophobic and hydrophilic) were used. During the study, the influence of the flow rate of the water phase and the oil phase on the droplet size and size distribution was investigated. Moreover, the influence of the oil phase viscosity on the droplet size was analyzed. It was found that the size and size distribution of the droplets can be controlled simply by the aqueous phase flow rate. Additionally, 2D simulations to determine the droplet size were performed and compared with the experiment.Marek Wojnicki, Magdalena Luty-Błocho, Volker Hessel, Edit Csapó, Ditta Ungor and Krzysztof Fitzne

The Gifted and Gifted Education in Hungary

The real challenge is to see value that is not yet in its true form. Becoming gifted is a process, during which characteristics of giftedness are present throughout, but not necessarily in a form perceptible or acceptable to the environment. Giftedness does not hide itself, only to the extent that the environment believes it hidden. Perception defines the pattern that manifests itself. The beginning of the 20th century is a success story of Hungarian gifted education. Outstanding teachers and their students have reached outstanding achievements through gifted education linked to everyday education. Their methods and ideas are durable, and are therefore worth recalling