Annual Report 1991
Contents
- Flavour compounds as indicators of the oxidative fat deterioration
- A comparative study on the potent odorants of different virgin olive oils
- Investigation into the ripening of cheddar
- Microvariant of the Rrpid-
mix- test - Thin-
layer electrophoresis of thickening agents - Detection of soya in sausage after electrophoretic separation
- Detection of rough potatoes in doughs for dumplings
- Nutrition tables
Food Chemistry, Biochemistry and Microbiology
- Sensory study on the character-
impact flavour compounds of dill herb (Anethum graveolens L.) - Potent Ooorants causing the warmed-
over flavour in boiled beef - Detection of furanoid fatty acids in soya-
bean oil. Cause for the light- induced off- flavour - Identification of volatile compounds having a roasty smell
- Studies on the formation of wheat bread flavour
- Peptide patterns of HMW subunits of glutenin from different wheat varieties
- Breadmaking quality and HMW glutenin subunits of wheat varieties: qualitative and quantitative investigations by RP-HPLC
- Redox experiments with HMW glutenin subunits from wheat
- Disulfide bonds in wheat glutelin
- Isolation and characterization of HMW-
glutelin subunits from rye - Sugars and sugar derivatives: structure-
taste rellationships
Summaries
1. FOOD ANALYSIS
1.1. Flavour compounds as indicators of the oxidative fat deterioration
Oxidative fat deterioration was studied with butter oil as example. The volatiles of fresh and stored butter oil were compared by aroma extract dilution analysis (AEDA). AEDA of the fresh sample resulted in 19 odour compounds with dilution factor (FD) values between 32 and 4096. Of these compounds, 16 were identified as: diacetyl, acetic and butyric acid, 1-hexen-
1.2. A comparative study on the potent odorants of different virgin olive oils
The flavour of virgin olive oil from Italy (fruity, green, fatty) and Spain (black currant-
1.3. Investigation into the ripening of cheddar
Analytical methods, which give insight into the ripening state of cheese are important for processing. A control is possible via the protein degradation, especially by following degradation products with chromatographic and electrophoretic methods.
The ripening of two Cheddar samples of German and English provenience was followed by RP-
1.4. Microvariant of the rapid-
The German wheat varieties are classified according to the loaf volumes in the Rapid-
A 10 g-microvariant of the Rapid-
1.5. Thin-
Thin-
1.6. Detection of soya in sausage after electrophoretic separation
Soya proteins in foodstuffs are detectable by unspecific staining methods after electrophoretic separation. Disturbances may be caused by matrix proteins. Therefore some specific detection methods for soya proteins were tested in combination with SDS-
1.7. Detection of raw potatoes in doughs for dumplings
Doughs for dumplings made with rough potatoes ("Rohe Klöße") are industrially produced by mixing of raw and cooked potatoes, but also solely from partial cooked potatoes. An analytical method has been developed for the differentiation between the two products, which is based on activities of phosphatases and proteinase inhibitors of different thermal stability.
1.8. Nutrition tables
Food composition and nutrition tables are essential for administration, nutritional guidance, economy and science. The large, scientific work "Souci, Fachmann, Kraut: Food Composition and Nutrition Tables" is kept up to date by a continuous survey of the scientific literature with the aid of the data bank LINDAS. The same is true for the related small table "Der kleine 'Souci, Fachmann, Kraut': Lebensmitteltabelle für die Praxis", which was developed for the daily requirements of the consumer.
The preparation of the manuscript for the 5th edition of the large table has been continued. Focal points of activity were fatty acids, trace elements (selenium, copper, zinc, manganese, iron, nickel, chromium, and iodine), vitamins (E, A, and A-active carotinoids), and purines.
The 2nd edition of the small table was published in March 1991.
2. FOOD CHEMISTRY, BIOCHEMISTRY AND MICROBIOLOGY
2.1. Sensory study on the character-
The dependence of the characteristic odour note of dill herb from the concentration levels of five compounds, having the highest odour units in an extract obtained from the fresh material, was studied. (S)-alpha-
2.2. Potent odorants causing the warmed-
The flavour compounds showing higher odour units and resulting from a peroxidation of unsaturated fatty acids were comparatively analysed in freshly boiled beef and in a stored (48 h, 4°C) sample exhibiting WOF. The results obtained by aroma extract dilution analysis revealed that hexanal, 1-octen-
2.3. Detection of furanoid fatty acids in soya-
The following furanoid fatty acids were detected in soya-
2.4. Identification of volatile compounds having a roasty smell
Application of an aroma extract dilution analysis to freshly prepared popcorn revealed 23 odorants among which 2-acetyl-
2.5. Studies on the formation of wheat bread flavour
Recently we could establish bakers yeast as a potent source of precursors for the roast-
To reveal their role in the formation of both odorants, the concentrations of free amino acids occurring in bakers yeast were determined. Eleven amino acids present in concentrations above 60 mg/100 g of dry yeast were separately reacted with 2-oxopropanal in model solutions and the amounts of ACPY and ACTPY formed, determined by a stable isotope dilution assay. ACPY was formed from proline and ornithine, while ACTPY was exclusively liberated from proline. The remaining amino acids were ineffective. Further experiments revealed that the formation of ACPY from ornithine proceeds via 4-aminobutyraldehyde and 2-pyrroline as intermediates.
The amount of free ornithine in yeast was more than three times the amount of free proline. Furthermore, additions of either proline or ornithine to wheat doughs enhanced the amounts of ACPY in the bread crust by a factor of two or four, respectively. The data allowed the conclusion that ornithine is the most important precursor for the formation of ACPY during baking.
2.6. Peptide patterns of HMW subunits of glutenin from different wheat varieties
Functional properties of wheat varieties have been often correlated more or less succesful with the pattern of HMW glutenin subunits, obtained by SDS-
2.7. Breadmaking quality and HMW glutenin subunits of wheat v: qualitative and quantitative investigations by RP-
The significance of the type as well as of the amount of HMW glutenin subunits relatively to the functional properties is well known. Former results were reinvestigated with four varieties of known baking performance from the USA. The varieties were quantitatively analyzed for HMW glutenin subunits. The correlation between the amount of subunits of the X-type (2, 5, 7, 17) and the mixing time and the loaf volume was very high (r = 0.997 and 0.991, respectively), while subunits of the Y-type (8, 18) delivered significantly lower values (r = 0.773 and 0.791, respectively).
2.8. Redox experiments with HMW glutenin subunits from wheat
In the literature, different bread making properties of wheat varieties have been related to the degree of polymerization of the HMW glutenin subunits, which may be dependent from the structure of these proteins. To get further insight, the reoxidation of reduced mixtures of subunits from strong (Rektor) and poor (Apollo) wheat varieties was followed by SH/SS-
2.9. Disulfide bonds in wheat glutelin
Inter-
Therefore, the glutenin fraction of gluten from the wheat variety Rektor was hydrolyzed with trypsin. The hydrolyzate was separated by RP-
2.10. Isolation and characterization of HMW-
Rye is phylogenetically closely related to wheat, but unable to form gluten. Structural differences of the HMW glutenin subunits of the two cereals may be responsible. To verify this hypothesis, the subunits of the rye variety Danko were isolated and compared with the subunits of the wheat variety Rektor. The amounts of HMW glutenins were different: Rektor contained the 2.5fold amount according to flour, and the 1.7fold amount according to protein. Four subunits were detected in Danko by SDS-
2.11. Sugars and sugar derivatives: structure-
The compatability of sugars and sugar derivatives with a recently developed basic model for sweet compounds should be proved. Sugars, sugar alcohols, anhydrosugars, glycosides and halogenated sugars interact with a receptor analog to diols via vicinal hydroxy groups. Sucrose could be inserted into the receptor model 1 (cf. DFA Bericht 1990, p. 162 ) with the groups OH3'/OH4' and OH3'/OH2, respectively, as e/n-
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