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

EFFECT OF MICROORGANISMS ON FREE AMINO ACID AND FREE D-AMINO ACID CONTENTS OF VARIOUS DAIRY PRODUCTS

Free amino acid and free D-amino acid contents of milk samples with different microorganism numbers and composition of dairy products produced from them were examined. Total microorganism number of milk samples examined varied from 1.25x106 to 2.95x106. It was established that concentration of both free D-amino acids and free L-amino acids increased with an increase in microorganism number. However, increase in D-amino acid contents was higher considering its proportion. There was a particularly significant growth in the microorganism number range from 1.5x106 to 2.9x106. Based on analysis of curds and cheese samples produced using different technologies we have come to the conclusion that for fresh dairy products and for those matured over a short time there was a close relation between total microorganism number and free D-amino acid and free L-amino acid contents. At the same time it was found that the ratio of the enantiomers was not affected by the total microorganism number. For dairy products, however, where amino acid production capability of the microbial cultures considerably exceeds, production of microorganisms originally present in the milk raw material, free amino acid contents of the milk product (both D- and L-enantiomers) seem to be independent of the composition of milk raw material

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

CHANGES IN FATTY ACID COMPOSITION OF DIFFERENT MILK PRODUCTS CAUSED BY DIFFERENT TECHNOLOGY

The fatty acid composition of cow’s milk with fat contents of 3.6%, Dalia cheese with fat contents of 44%, butter with fat contents of 80% and margarine with fat contents of 24% was determined after a heat treatment performed on cooking plate and microwave treatment, respectively of different durations. The biggest difference was obtained for oleic acid and elaidic acid since, with the exception of the margarine, in each case proportion of the cis-configurated oleic acid decreased while that of the trans-configurated elaidic acid increased. For all of the other fatty acids in the foodstuffs examined no such differences were obtained regarding change in fatty acid composition whose differences could influence healthy nutrition to considerable extent. Therefore we can take it as a fact that neither heat treatment performed on a traditional cooking plate nor microwave treatment affects considerably the composition of food fats

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

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

Influence of Soil Moisture and Crust Formation on Soil Evaporation Rate: A Wind Tunnel Experiment in Hungary

In both arid and semiarid regions, erosion by wind is a significant threat against sustainability of natural resources. The objective of this work was to investigate the direct impact of various soil moisture levels with soil texture and organic matter on soil crust formation and evaporation. Eighty soil samples with different texture (sand: 19, loamy sand: 21, sandy loam: 26, loam: 8, and silty loam: 6 samples) were collected from the Nyírség region (Eastern Hungary). A wind tunnel experiment was conducted on four simulated irrigation rates (0.5, l.0, 2.0, and 5.0 mm) and four levels of wind speeds (4.5, 7.8, 9.2, and 15.5 m s−1). Results showed that watering with a quantity equal to 5 mm rainfall, with the exception of sandy soils, provided about 5–6 h protection against wind erosion, even in case of a wind velocity as high as 15.5 m s−1. An exponential connection was revealed between wind velocities and the times of evaporation (R2 = 0.88–0.99). Notably, a two-way ANOVA test revealed that both wind velocity (p &lt; 0.001) and soil texture (p &lt; 0.01) had a significant effect on the rate of evaporation, but their interaction was not significant (p = 0.26). In terms of surface crusts, silty loamy soils resulted in harder and more solid crusts in comparison with other textures. In contrast, crust formation in sandy soils was almost negligible, increasing their susceptibility to wind erosion risk. These results can support local municipalities in the development of a local plan against wind erosion phenomena in agricultural areas