Template-Type: ReDIF-Article 1.0 Author-Name: J. Rössner Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: J. Velíšek Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: F. Pudil Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: J. Davídek Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Title: Strecker degradation products of aspartic and glutamic acids and their amides Abstract: 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 ammonia and yields fumaric acid whereas glutamic acid gives rise to an imine, pyroglutamic acid. A recombination of free radicals leads to dicarboxylic acids (succinic acid from aspartic acid, succinic, glutaric and adipic acids from glutamic acid). The major volatile products (besides the aldehydes) are lower carboxylic acids (acetic acid from aspartic acid and propionic acid acid from glutamic acid) that can at least partly arise by radical reactions. In both quality and quantity terms, a higher amount of degradation products arises by oxidation of amino acids by peroxodisulphate. Keywords: Strecker degradation, Strecker aldehydes, amino acids, glyoxal, sodium peroxodisulphate, aspartic acid, glutamic acid, asparagine, glutamine, radicals Journal: Czech Journal of Food Sciences Pages: 41-45 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6573-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6573-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0001.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6573-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: M. Plocková Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology, Prague, Czech Republic Author-Name: J. Stiles Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology, Prague, Czech Republic Author-Name: J. Chumchalová Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology, Prague, Czech Republic Author-Name: R. Halfarová Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology, Prague, Czech Republic Title: Control of mould growth by Lactobacillus rhamnosus VT1 and Lactobacillus reuteri CCM 3625 on milk agar plates. Abstract: 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 rhamnosus VT1 probably consists in the production of lactic acid (1.2% w/w) together with some other metabolite(s) of non-proteinaceous and non-saccharidic nature with antifungal activity Keywords: Lactobacillus, milk agar plate, mould growth control, antifungal metabolite Journal: Czech Journal of Food Sciences Pages: 46-50 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6574-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6574-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0002.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6574-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Čopíková Author-Workplace-Name: 2 Central Laboratory, Prague, Czech Republic Author-Name: M. Černá Author-Workplace-Name: 2 Central Laboratory, Prague, Czech Republic Author-Name: M. Novotná Author-Workplace-Name: 2 Central Laboratory, Prague, Czech Republic Author-Name: J. Kaasová Author-Workplace-Name: 2 Central Laboratory, Prague, Czech Republic Author-Name: A. Synytsya Author-Workplace-Name: 2 Central Laboratory, Prague, Czech Republic Title: Application of FT-IR spectroscopy in detection of food hydrocolloids in confectionery jellies and food supplements Abstract: 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. Keywords: FT-IR spectroscopy, polysaccharides, jelly, food supplements Journal: Czech Journal of Food Sciences Pages: 51-56 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6575-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6575-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0003.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6575-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: Š. Malá Author-Workplace-Name: Institute of Chemical Technology - Department of Biochemistry and Microbiology, Prague, Czech Republic Author-Name: P. Karasová Author-Workplace-Name: Institute of Chemical Technology - Department of Biochemistry and Microbiology, Prague, Czech Republic Author-Name: M. Marková Author-Workplace-Name: Institute of Chemical Technology - Department of Biochemistry and Microbiology, Prague, Czech Republic Author-Name: B. Králová Author-Workplace-Name: Institute of Chemical Technology - Department of Biochemistry and Microbiology, Prague, Czech Republic Title: Oligosaccharide synthesis using a-glucosidases of different origin Abstract: 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. Keywords: alpha-glucosidase, transglycosylation, synthesis of glucooligosaccharides Journal: Czech Journal of Food Sciences Pages: 57-61 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6576-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6576-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0004.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6576-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Kaasová Author-Workplace-Name: Institute of Chemical Technology - Department of Carbohydrate Chemistry and Technology, Prague, Czech Republic Author-Name: P. Kadlec Author-Workplace-Name: Institute of Chemical Technology - Department of Carbohydrate Chemistry and Technology, Prague, Czech Republic Author-Name: Z. Bubník Author-Workplace-Name: Institute of Chemical Technology - Department of Carbohydrate Chemistry and Technology, Prague, Czech Republic Author-Name: V. Pour Author-Workplace-Name: Institute of Chemical Technology - Department of Carbohydrate Chemistry and Technology, Prague, Czech Republic Title: Microwave treatment of rice Abstract: 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 of microwave and conventional rice drying for further use. Keywords: microwave, drying, rice, starch Journal: Czech Journal of Food Sciences Pages: 62-66 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6577-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6577-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0005.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6577-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: L. Němcová Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology Author-Name: J. Štětina Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology Author-Name: H. Valentová Author-Workplace-Name: Institute of Chemical Technology - Department of Dairy and Fat Technology Title: Proteolysis and consistency changes of Gouda and Eidamský blok cheeses during ripening Abstract: 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 as cohesiveness decreased with ripening time because of proteolysis. Based on the intensity sensory evaluations, the salt taste appears more intensive whereas the sour and bitter tastes were less intensive in Gouda cheese. Gouda cheese was evaluated as more pleasant in all three tastes in the hedonic sensory evaluation. The width and depth of ripening increased quite fast in Gouda cheese up to 10 months of maturation. In a four-week old Eidamský blok cheese the slightly lower values of ripening width and depth were obtained. The electrophoretic evaluation showed that the number of identifiable zones rose with ripening time. The growing content of g1-casein, proteose peptone fraction 5, and g2/g3-caseins, which are the products of b-caseins hydrolysis, can be observed as the increase of their zone intensity. Keywords: proteolysis, cheese, rheology, sensory evaluation, electr Journal: Czech Journal of Food Sciences Pages: 67-72 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6578-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6578-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0006.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6578-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: V. Hábová Author-Workplace-Name: Institute of Chemical Technology, Prague Department of Fermentation Chemistry and Bioengineering Author-Name: K. Melzoch Author-Workplace-Name: Institute of Chemical Technology, Prague Department of Fermentation Chemistry and Bioengineering Author-Name: M. Rychtera Author-Workplace-Name: Institute of Chemical Technology, Prague Department of Fermentation Chemistry and Bioengineering Author-Name: L. Přibyl Author-Workplace-Name: Institute of Chemical Technology, Prague Department of Fermentation Chemistry and Bioengineering Author-Name: V. Mejta Author-Workplace-Name: Institute of Chemical Technology, Prague Department of Fermentation Chemistry and Bioengineering Title: Application of electrodialysis for lactic acid recovery Abstract: 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 Corp.,Japan). The final lactic acid concentration of 157 g/l was reached in the diluate. Total required energy in both electrodialysis processes consisting of the energy consumption for lactate transfer and for its electroconversion to lactic acid was 142 Wh/mol. The fermentation broth was decolourised before electrodialysis experiments. The best decolourisation capacity was shown by granulated active charcoal filled in the column operated by a slow flow of broth. Keywords: lactic acid recovery, electrodialysis, desalting electrodialysis, water-splitting electrodialysis, decolourisation Journal: Czech Journal of Food Sciences Pages: 73-80 Volume: 19 Issue: 2 Year: 2001 DOI: 10.17221/6579-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6579-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200102-0007.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:2:id:6579-CJFS