Chemie | Biochemie | Medizin
Noée Désirée Niggli, 2003 | Oekingen, SO
Fish thiaminase I is a thiamine-decomposing enzyme which reacts by base exchange reaction with an organic base. Despite previous studies trying to find out more about the physiological significance of the enzyme, it remains unclear. This study investigated the influence of unpurified fish thiaminase I from ordinary carp (Cyprinus carpio) on the thiamine content in pork fillet by common storage in a small-scale incubator at 41°C involving measuring points after 5, 20 and 60min. Thiamine was quantified fluorometrically by reversed-phase high-performance liquid chromatography. The results proposed that carp thiaminase I significantly lowered the thiamine level in pork fillet puree. However, due to unexplained outliers and missing reproducibility checks of sample decomposition, the influence of the enzyme could not be proven beyond any doubt. Understanding the influence and action of fish thiaminase I is important, since this enzyme may cause thiamine deficiency in humans or animals if absorbed under certain conditions.
The aim of this study was to find out whether unpurified carp thiaminase I in partially decomposed cells has any influence on the thiamine content in partially decomposed pork fillet cells when stored together for 60min at 41°C.
Experimental storage was conducted three times in a row, each procedure including thiamine level determination after 5, 20 and 60min of incubation. Every procedure included a reference sample for the initial thiamine level in the pork fillet puree, a reference sample for the pH determination in the carp organ mix, three incubated reference samples containing pork fillet puree as well as six samples consisting of pork fillet puree and carp organ mix. In collaboration with SQTS (Swiss Quality Testing Services, Dietikon), fluorometrical thiamine determination was conducted by reversed-phase HPLC.
Overall, carp thiaminase I significantly lowered the thiamine content in pork fillet puree on average by 0.4mg/100g during 60min of incubation. The average initial thiamine level of 1.23mg/100g found in the reference samples is much higher than the average thiamine level of 0.55mg/100g of the reference samples incubated for 60min. Additionally, the average thiamine value of 0.15mg/100g found in the samples incubated for 60min and containing pork fillet puree as well as carp organ mix is much smaller than the thiamine level of the incubated reference samples. However, unexplained discrepancies were first that the thiamine values obtained in procedure 1 showed that enzyme-containing samples were higher in thiamine than in the incubated sample without any enzyme. Second, thiamine values of procedure 2 obtained after 5 and 20min of incubation were lower than the ones found after 60min.
Due to the average decrease in thiamine of 0.4mg/100g after 60min of incubation, the null hypothesis can be rejected. However, no reason could be found why the thiamine values obtained in procedure 1 showed that the enzyme-containing samples were higher in thiamine than the incubated non-enzyme-containing reference sample and thus, the first hypothesis can be ruled out too. Also, it needs to be considered that carp organ mix only had a limited contact area with pork fillet puree, so the enzyme is regarded to only have decomposed thiamine and its derivates on the surface of the pork fillet puree.
It could be shown that the pork fillet and carp organ cells were at least partially decomposed during sample preparation since average thiamine decrease amounted to 0.4mg/100g after 60min of incubation. Since no reason could be found why some samples showed the opposite effect, namely that thiamine was lower in samples only containing pork fillet puree than in the ones which also contained carp organ mix, and no reproducibility tests of sample decomposition were made, it could not be proven beyond any doubt that fish thiaminase I has an influence on the thiamine content in pork if they are stored together for 60min at 41°C. At a further examination, complete cellular decomposition in pork fillet and carp organs should be reached. Besides the samples used in this study, three samples of pork fillet puree as well as three samples of carp organ mix should be incubated. At the usual measuring points after 5, 20 and 60min of incubation, along with the usual samples, one sample each of the additional ones should be removed. Then, in all samples the remaining thiamine should be stabilised and preserved for the analytical determination by means of metaphosphoric acid addition.
Würdigung durch den Experten
Prof. Dr. Zehnder Beat
Die Problematik der gegenseitigen Kontamination von Lebensmitteln bei der Lagerung am Beispiel von frischem Fleisch zusammen mit frischem Fisch wurde sorgfältig recherchiert. Das ausgearbeitete Untersuchungsmodell wurde einfallsreich und gewissenhaft umgesetzt, die Messwerte transparent und systematisch ausgewertet und die Ergebnisse sorgfältig, übersichtlich, klar und fehlerfrei präsentiert. Aus der kritischen Auseinandersetzung mit den Ergebnissen wurden lösungsorientierte Vorschläge für allfällig weitere Studien entwickelt und skizziert.
Sonderpreis AO Foundation
Lehrer: Christoph Wetterwald