Template-Type: ReDIF-Article 1.0 Author-Name: P. Karasová Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Author-Name: V. Spiwok Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Author-Name: Š. Malá Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Author-Name: B. Králová Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Author-Name: N.J. Russell Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Title: Beta-galactosidase activity in psychrotrophic microorganisms and their potential use in food industry Abstract: Twenty-one psychrotrophic resp. psychrophilic bacterial strains were screened for presence of b-galactosidase activity which showed 8 of them. b-Galactosidase activity of these strains was determined for 2 substrates - synthetic substrate (ONPG) and lactose - and also temperature profile of this enzyme was measured. b-Galactosidase from Arthrobacter sp. C2-2 not only proved the typical properties of cold-active enzyme, but it also preferred lactose as a substrate. Therefore, it was chosen for further isolation and purification and was found that it contains two b-galactosidase isoenzymes. One of them had strong preference for lactose and was able to catalyse transglycosylation reactions at low temperature. It has, thus, potential use in food technology. Keywords: psychrotrophic microorganism, cold-active enzyme, b-galactosidase, lactose hydrolysis, transglycosylation Journal: Czech Journal of Food Sciences Pages: 43-47 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3508-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3508-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0001.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3508-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: Z. Řiháková Author-Workplace-Name: Department of Dairy and Fat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: V. Filip Author-Workplace-Name: Department of Dairy and Fat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: M. Plocková Author-Workplace-Name: Department of Dairy and Fat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: J. Šmidrkal Author-Workplace-Name: Department of Dairy and Fat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: R. Červenková Author-Workplace-Name: Department of Dairy and Fat Technology, Institute of Chemical Technology, Prague, Czech Republic Title: Inhibition of Aspergillus niger DMF 0801 by monoacylglycerols prepared from coconut oil Abstract: The objectives of the present study were to test the antifungal properties (inhibition of radial growth, inhibition of the mould spore germination) of lauroylglycerol and mixtures of monoacylglycerols synthesised from coconut oil (MIX-I and MIX-II) against Aspergillus niger DMF 0801. The content of monoacylglycerols in lauroylglycerol, MIX-I and MIX-II was 99.9% (w/w), 97.7% (w/w) and 75,1% (w/w), respectively. The content of 1-lauroylglycerol in MIX-I and MIX-II was calculated from the content of lauric acid and content of monoacylglycerols. The inhibition of the radial growth of Aspergillus niger DMF 0801 by lauroylglycerol was stronger than that caused by MIX-I and MIX-II. The inhibition effect of spore germination caused by lauroylglycerol and MIX-I was nearly the same. The inhibition of spore germination increased with increasing content of monoacylglycerol and also with increasing 1-lauroylglycerol content in monoacylglycerols. The level of spore germination inhibition was related to the purity of tested substances. The results of this study indicate that monoacylglycerols made from coconut oil have antifungal activity. Keywords: antifungal, monoacylglycerol, coconut oil, lauroylglycerol Journal: Czech Journal of Food Sciences Pages: 48-52 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3509-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3509-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0002.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3509-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: M. Vítková Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: P. Rauch Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: L. Fukal Author-Workplace-Name: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Czech Republic Title: Optimisation of indirect competitive ELISAs of a-, b-, and k-caseins for the recognition of thermal and proteolytic treatment of milk and milk products Abstract: Polyclonal antibodies were raised against six immunogens (three native and three thermally treated casein fractions: a+b-casein, k-casein and whole casein). Using these antibodies the procedures of an indirect competitive enzyme immunoassay (ELISA) were constructed, optimised and characterised for determination of each immunogen. It was found that ELISA of caseins is very specific without any interferences of whey proteins and with proportionally low cross-interactions between caseins. Detection limits for a-, b-, and k-caseins and whole casein were 110, 49, 58 and 505 ng/ml, respectively. The coefficient of variation was lower than 12% in intra-assay and lower than 9% in inter-assay. The developed ELISA format was used to study changes in casein immunoreactivity during heat-treatment and proteolytic hydrolysis. Heating below 100°C did not change the milk immunoreactivity but heating above 100°C caused its significant changes. Depending on type of proteolytic treatment (with enzyme preparation Pancreatin or with microbial cultures of Lactobacillus helveticus and Lactococcus) a decrease and an increase in casein immunoreactivity were observed. While Pancreatin reduced the casein immunoreactivity substantially (5-1000 times in dependence on the casein type), the more gentle proteolysis by bacteria caused not only its reduction (even 100 times at k-casein) but also its increase (1.5 times at a-casein). Keywords: a-casein, b-casein, k-casein, casein hydrolysates, antibody, immunoassay, ELISA Journal: Czech Journal of Food Sciences Pages: 53-62 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3510-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3510-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0003.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3510-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: F. Kotal Author-Workplace-Name: Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic Author-Name: Z. Radová Author-Workplace-Name: Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic Title: A simple method for determination of deoxynivalenol in cereals and flours Abstract: An effective and fast method for determination of deoxynivalenol (DON) in cereals and flours has been developed. The immunoaffinity column was used for the isolation of DON from wheat, corn, rice and flour extract. The determination was carried out by using the HPLC/UV method. The limit of detection was 0.02 mg/kg. The recoveries for the assay range 0.1 to 2 mg/kg were generally higher than 80%, ranging from 83 to 96% with an average relative standard deviation of 3.8%. The trueness of the method using the DON test - HPLC column was established by use of certified reference material CRM 379. The certified value was 0.67 mg/kg. The result obtained from three replicates was 0.68 ± 0.05 mg/kg. The corresponding confidence interval at 95% probability ranged from 0.63 to 0.73 mg/kg. A comparative study of the DON testTM - HPLC/UV and the Mycosep 225 - GC/ECD methods was carried out. Six naturally contaminated wheat samples were analysed by both methods. Linear regression analysis demonstrates that DON testTM - HPLC is a statistically significant predictor of the GC/ECD method using the Romer Mycosep 225 column. Keywords: mycotoxins, deoxynivalenol, HPLC, immunoaffinity chromatography Journal: Czech Journal of Food Sciences Pages: 63-68 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3511-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3511-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0004.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3511-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: M. Miyahara Author-Workplace-Name: 2 College of Bioresource Sciences, Nihon University, Fujisawa, Japan; Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: T. Matsumoto Author-Workplace-Name: 2 College of Bioresource Sciences, Nihon University, Fujisawa, Japan; Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: H. Sakurai Author-Workplace-Name: 2 College of Bioresource Sciences, Nihon University, Fujisawa, Japan; Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: P. Pipek Author-Workplace-Name: 2 College of Bioresource Sciences, Nihon University, Fujisawa, Japan; Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Prague, Czech Republic Title: The conformability of two equations for bacterial growth in pork Abstract: Pork is now distributed as cut meat, which increases the chance of contamination with bacteria. The rate of bacterial growth can be expressed by an exponential function. In order to find how the number of contaminating bacteria increases, we compared two functional equations for a growth curve. They are logistic: Yt = K (1 + m e-at) (1) and Gompertz: log Yt = log K + (log a)bt (2) equations (where Yt = the number of bacteria at the time t in min, m and a = coefficient, e = natural logarithm, K maximum number of bacteria). 90 ml of physiological salt solution was added to 10 g of pork. It was homogenized for 3 min, then incubated at 35°C for 13 hrs. The number of bacteria was counted every hour. We found from these data that the above two equations can be expressed as follows: Yt = 23 535 (1 + 16269 e-1.1608t) and log Yt = 8.9940 + (-3.1124) × 0.7839t. The theoretical and actual values matched well in equation (1), and the number of bacteria can be predicted accurately using this equation at a given time after incubation. The theoretical and actual values did not match well in equation (2) and its accuracy to predict the number of bacteria was very low except the initial number of bacteria was high. Keywords: logistic equation, mathematical model, micro-organismus, Gompertz Journal: Czech Journal of Food Sciences Pages: 69-73 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3512-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3512-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0005.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3512-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Kaasová Author-Workplace-Name: Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: B. Hubáčková Author-Workplace-Name: Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: P. Kadlec Author-Workplace-Name: Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: J. Příhoda Author-Workplace-Name: Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Prague, Czech Republic Author-Name: Z. Bubník Author-Workplace-Name: Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Prague, Czech Republic Title: Chemical and biochemical changes during microwave treatment of wheat Abstract: The effect of microwave (MW) heating on the changes in wet gluten content, Gluten Index, Falling Number and amylographic characteristics was studied in sprouted wheat grain. Different moistures of wheat in two ranges of 10-11% and 15-17% and two end temperatures of MW heated samples (60 and 80°C) were applied to wheat samples. Falling Number and Gluten Index increased with increasing absorbed energy during MW heating, whereas gluten content decreased. Amylographic maximum increased due to a-amylase inactivation progressively with increasing absorbed energy as well. The greatest relative changes occurred when the end temperature of MW heated samples 80°C and moisture 15% were used. An improvement effect on the baking quality of sprouted wheat was found due to an increase in amylographic maximum with higher energy doses and higher end temperatures of MW heated samples. It was a consequence of Falling Number increase and Gluten Index increase with lower energy doses. The negative effect of higher energy doses was proved in a decrease in wet gluten content. Keywords: sprouted wheat, microwave treatment, Falling Number, gluten Journal: Czech Journal of Food Sciences Pages: 74-78 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3513-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3513-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0006.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3513-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Adamiec Author-Workplace-Name: Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic Author-Name: M. Doležal Author-Workplace-Name: Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic Author-Name: K. Míková Author-Workplace-Name: Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic Author-Name: J. Davídek Author-Workplace-Name: Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech Republic Title: Changes in Egg Volatiles during Storage Abstract: The quality of eggs is tightly associated with freshness. New possibilities for the determination of egg freshness were studied. The volatile compounds of eggs and their changes during storage were followed. Three methods for extraction of volatiles were compared: dynamic headspace (Purge and Trap), static headspace (Solid Phase of Microextraction - SPME) and extraction according to Likens-Nickerson by simultaneous distillation-extraction (SDE) with diethyl ether as organic solvent. The extracts were analysed by GC/FID. The volatiles in an extract obtained by SDE method were identified by GC-MS. The extract includes aldehydes, alcohols, acids and esters. The volatiles in an extract obtained by SPME and Purge and Trap have not been identified until now. The changes in volatiles during storage of eggs using the above mentioned methods were studied. Keywords: quality of eggs, changes during storage, volatile compounds, Purge and Trap, Solid Phase of Microextraction, simultaneous distillation-extraction Journal: Czech Journal of Food Sciences Pages: 79-82 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3515-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3515-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0007.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3515-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: M. Voldřich Author-Workplace-Name: 11 2 2 MICHAL VOLDŘICH , PETRA SKÁLOVÁ , FRANTIŠEK KVASNIČKA , PETR CUHRA , MARTIN KUBÍK and PETR PYŠ 1Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Author-Name: P. Skálová Author-Workplace-Name: 11 2 2 MICHAL VOLDŘICH , PETRA SKÁLOVÁ , FRANTIŠEK KVASNIČKA , PETR CUHRA , MARTIN KUBÍK and PETR PYŠ 1Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Author-Name: F. Kvasnička Author-Workplace-Name: 11 2 2 MICHAL VOLDŘICH , PETRA SKÁLOVÁ , FRANTIŠEK KVASNIČKA , PETR CUHRA , MARTIN KUBÍK and PETR PYŠ 1Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Author-Name: P. Cuhra Author-Workplace-Name: 11 2 2 MICHAL VOLDŘICH , PETRA SKÁLOVÁ , FRANTIŠEK KVASNIČKA , PETR CUHRA , MARTIN KUBÍK and PETR PYŠ 1Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Author-Name: M. Kubík Author-Workplace-Name: 11 2 2 MICHAL VOLDŘICH , PETRA SKÁLOVÁ , FRANTIŠEK KVASNIČKA , PETR CUHRA , MARTIN KUBÍK and PETR PYŠ 1Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Author-Name: P. Pyš Author-Workplace-Name: 11 2 2 MICHAL VOLDŘICH , PETRA SKÁLOVÁ , FRANTIŠEK KVASNIČKA , PETR CUHRA , MARTIN KUBÍK and PETR PYŠ 1Department of Food Preservation and Meat Technology, Institute of Chemical Technology, Title: Authenticity of 100% orange juice in the Czech market in 1996-2001 Abstract: Commercial orange juices samples obtained from the Czech market were analysed in the years 1996-2001. The quality and authenticity of samples was evaluated according to the Code of Practice of AIJN (selected main analytical criteria were followed - K+, Na+, Ca2+, Mg2+, citric, isocitric and malic acid, citric acid/isocitric acid ratio, glucose, fructose, saccharose, sorbitol, formol number, flavonoid glycosides - according to Davis and HPLC procedure, refractive index and other). The approach of producers to the quality and authenticity of juices developed during the years of observation. The main cases of adulteration in 1996 were as follows: (i) lower fruit content in juice, (ii) massive addition of sugars masked with addition of citric acid, (iii) several examples of "synthetic" orange juice were found. In the subsequent years the authenticity slightly improved, the main problems in 2000/2001 were: (i) lower refractive index, (ii) pulp wash addition, (iii) lower quality of water used for juice reconstitution, (iv) undeclared addition of sugar. The deviations were found not only in the case of the juices of Czech producers, but also in several discount and low-end products of foreign producers. Possible ways of improving the quality and authenticity are discussed (e.g. the preparation of a Czech National Standard taking over the requirements for juices and nectars according to the Code of Practice of the AIJN, Participation in the European Quality Control System [EQCS], etc.). Keywords: orange juice, authenticity, adulteration, fruit content Journal: Czech Journal of Food Sciences Pages: 83-88 Volume: 20 Issue: 2 Year: 2002 DOI: 10.17221/3514-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/3514-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200202-0008.txt Handle: RePEc:caa:jnlcjf:v:20:y:2002:i:2:id:3514-CJFS