Czech Journal of Food Sciences, 2001 (vol. 19), issue 2
Strecker degradation products of aspartic and glutamic acids and their amides
J. Rössner, J. Velíšek, F. Pudil, J. Davídek
Czech J. Food Sci., 2001, 19(2):41-45 | DOI: 10.17221/6573-CJFS 
Aspartic and glutamic acids, asparagine and glutamine were oxidised with either potassium peroxodisulphate or glyoxal. Nonvolatile products were derivatised and analysed by GC/FID and GC/MS. Volatile reaction products were isolated and analysed by the same methods. It was found that the degradation reactions of amino acids are complex. Amino acids are principally degraded via the corresponding a-keto acids to Strecker aldehydes (aspartic acid to oxalacetic and 3-oxopropionic acids and glutamic acid to a-ketoglutaric and 4-oxobutyric acids), which are unstable and decomposed by decarboxylation to the corresponding aldehydes. Aspartic acid also eliminates...
Control of mould growth by Lactobacillus rhamnosus VT1 and Lactobacillus reuteri CCM 3625 on milk agar plates.
M. Plocková, J. Stiles, J. Chumchalová, R. Halfarová
Czech J. Food Sci., 2001, 19(2):46-50 | DOI: 10.17221/6574-CJFS
The possibility to control mould growth by Lactobacillus rhamnosus VT1 and Lactobacillus reuteri CCM 3625 in a milk environment was assessed using the milk agar plate method. Higher antifungal activity was exhibited by actively growing cells of both lactobacilli strains compared with the MRS broth supernatants of both bacterial strains containing metabolites with antifungal activity. The control of mould growth by Lactobacillus reuteri CCM 3625 was proved to be associated with the production of the mixture of lactic (0.9% w/w), acetic (0.2% w/w), and succinic (0.2% w/w) acids. The mechanism of mould growth control by Lactobacillus...
Application of FT-IR spectroscopy in detection of food hydrocolloids in confectionery jellies and food supplements
J. Čopíková, M. Černá, M. Novotná, J. Kaasová, A. Synytsya
Czech J. Food Sci., 2001, 19(2):51-56 | DOI: 10.17221/6575-CJFS
FT-IR spectra of isolated high molecule fractions were measured and used for identification of food hydrocolloids in confectionery jellies and food supplements. The simple comparison of spectra of standards and samples proved that this technique is useful for the monitoring of food hydrocolloids in particular food products.
Oligosaccharide synthesis using a-glucosidases of different origin
Š. Malá, P. Karasová, M. Marková, B. Králová
Czech J. Food Sci., 2001, 19(2):57-61 | DOI: 10.17221/6576-CJFS
a-Glucosidase from Aspergillus awamori and intestinal a-glucosidase (saccharase-isomaltase complex) exhibited high transglycosylation activity and were able to synthesize tri- and tetrasaccharides during maltose hydrolysis. Both tested enzymes were also able to transfer the glucose residue to all tested monosaccharide acceptors (D-mannose, D-xylose, L-sorbose and D-galactose). Their transfer activity towards respective acceptors varied and their acceptor preference also depended on the origin of the enzyme. Out of the acceptors tested, both enzymes exhibited high transfer activity in xylose.
Microwave treatment of rice
J. Kaasová, P. Kadlec, Z. Bubník, V. Pour
Czech J. Food Sci., 2001, 19(2):62-66 | DOI: 10.17221/6577-CJFS
The effect of microwave treatment on wet rice was studied. Power output used was 90, 160, 350 or 500 W; final heating temperatures were 40, 60 and 80°C; initial moisture content of rice was 11, 21 or 30%. Temperature of treated sample during microwave heating was measured by means of NoEMI fiber-optic temperature system. Temperature of rice gelatinization, expressed as alkali spreading values and total starch content, was used to evaluate the influence of microwave heating on physicochemical properties of rice. Drying time reduction and the stability of total starch content during microwave treatment of rice makes it possible to recommend the combination...
Proteolysis and consistency changes of Gouda and Eidamský blok cheeses during ripening
L. Němcová, J. Štětina, H. Valentová
Czech J. Food Sci., 2001, 19(2):67-72 | DOI: 10.17221/6578-CJFS
Composition and rheological and sensory properties of Gouda cheese with different time of ripening (4 weeks, 4, 10, and 14 months) was evaluated. The level of proteolysis was measured by both the determination of nitrogenous compound fractions and the electrophoretic determination of casein proteolysis products. These properties were compared to those determined in Eidamský blok cheese with ripening time of 4 weeks. According to rheological evaluation, cheese hardness increased with ripening time. Sensory evaluation showed that hardness between fingers and in mouth increased and, on the other hand, the elasticity between fingers and in mouth as well...
Application of electrodialysis for lactic acid recovery
V. Hábová, K. Melzoch, M. Rychtera, L. Přibyl, V. Mejta
Czech J. Food Sci., 2001, 19(2):73-80 | DOI: 10.17221/6579-CJFS
The paper deals with the possibility of using two-stage electrodialysis for recovery of lactic acid from model solutions and from fermentation broth. In the first step lactate was concentrated with desalting electrodialysis using ion exchange membranes Ralex (Mega,Czech Republic). The highest final concentration of 111 g/l was reached in the concentrate, it means an increase more than 2.5-times in comparison with the initial concentration. At the most 2 g of lactate per litre remained in the feed. The second step was the electroconversion of sodium lactate to lactic acid by water-splitting electrodialysis with the bipolar membranes Neosepta (Tokuyama...