Czech Journal of Food Sciences, 2010 (vol. 28), issue 5
'GAB' generalised equation as a basis for sorption spectral analysis
Jiří Blahovec, Stavros Yanniotis
Czech J. Food Sci., 2010, 28(5):345-354 | DOI: 10.17221/146/2009-CJFS 
The transformed sorption isotherm (represented by the ratio of water activity and moisture content (d.b.) versus water activity) was approximated by polynomials of 2nd-6th order. It is shown that the relative derivative of the transformed equation expresses the deviation of the sorption isotherm from the linear relationship between the moisture content and water activity either to the sorption isotherm of the Lagmuir's type (the positive relative derivative) or to the sorption isotherm of the solution type (the negative relative derivative). The relative derivative plotted versus water activity then serves as a spectral indicator...
Kinetics of hydrolysis of egg white protein by pepsin
Chang-Qing Ruan, Yu-Jie Chi, Rui-Dong Zhang
Czech J. Food Sci., 2010, 28(5):355-363 | DOI: 10.17221/228/2009-CJFS
Taking into account the enzyme inactivation and substrate inhibition, the bioreaction mechanism and kinetics characteristic of egg white protein (EWP) enzymatic hydrolysis by pepsin were investigated. A logarithmic equation h = (1/b) ln (1 + abt) indicating the relationship between the degree of hydrolysis (DH) and time was established. For EWP-pepsin system, the reaction mechanism could be deduced from a series of experimental results at different temperatures, pH values, substrate concentrations, and enzyme concentrations. The reaction kinetics and thermodynamic constants (KS = 3916.5 g/l, k2...
Sodium chloride or heme protein induced lipid oxidation in raw, minced chicken meat and beef
Hamid R. Gheisari, Jens K.S. Møller, Christina E. Adamsen, Leif H. Skibsted
Czech J. Food Sci., 2010, 28(5):364-375 | DOI: 10.17221/182/2009-CJFS
The objective of this study was to evaluate the effect of the salt (NaCl) level (0%, 1% and 6%) or the addition of metmyoglobin (MetMb) in the amount twice that in the natural muscle content on the oxidative stability of minced chicken meat or beef. The minced meat samples with the added NaCl or added MetMb were stored for 3 weeks during which the analyses of TBARS, peroxide value, and volatiles coming from lipid oxidation were assessed together with the quantification of vitamin E and fatty acid profiles. Heme pigment and indices of lipid oxidation were higher for beef than for chicken, except the volatile octanal regardless of the pretreatment. Peroxide...
Biochemical parameters and oxidative resistance to thermal treatment of refined and unrefined vegetable edible oils
Rajko Vidrih, Sergeja Vidakovič, Helena Abramovič
Czech J. Food Sci., 2010, 28(5):376-384 | DOI: 10.17221/202/2008-CJFS
In human nutrition fats are physiologically important food constituents but also the components most liable to oxidative degradation. The oils included in the study were refined (sunflower, extra-sunflower, soybean, and rapeseed) as well as unrefined (olive and pumpkin-seed) oils. The aim of our study was to determine the fatty acid composition, tocopherol content, and quality parameters such as the free fatty acid content, peroxide value, and induction time. Extra virgin olive oil had the highest average peroxide value, while unrefined pumpkin seed oil had the lowest one. The acid value of the unrefined oils was higher on average than that of the...
The synergistic effect of daidzein and α-tocopherol or ascorbic acid on microsome and LDL oxidation
Heya Wang, Masibo Wanyonyi Martin, Shian Yin
Czech J. Food Sci., 2010, 28(5):385-391 | DOI: 10.17221/104/2009-CJFS
Isoflavone daidzein brings potential health benefits. Its antioxidant properties are considered to be responsible in part for its protective effects. We investigated the antioxidant effects of daidzein and its interactive effects withα-tocopherol or ascorbic acid on Fe2+/ascorbate-induced oxidation of rat liver microsomes and copper-induced human low-density lipoprotein (LDL) oxidation. Although the inhibitory effect of daidzein on lipid peroxidation in microsome was weak, it effectively prevented LDL against oxidative modification by prolonging the lag time, decreasing the propagating rate, and suppressing malonaldehyde (MDA) and carbonyls...
Effect of milk chocolate supplementation with lyophilised Lactobacillus cells on its attributes
Dorota Żyżelewicz, Ewa Nebesny, Ilona Motyl, Zdzisława Libudzisz
Czech J. Food Sci., 2010, 28(5):392-406 | DOI: 10.17221/217/2009-CJFS
Manufacturing of novel foodstuffs supplemented with live probiotic bacteria has recently been intensively investigated. The supplementation of confectionery with probiotics is troublesome since some unit technological processes are conducted at high temperatures and the products are usually stored at ambient temperature. Our group has developed a method of the production of milk chocolate, sweetened with either sucrose or isomalt and aspartame, containing 32, 36, or 40 g/100 g fat, and supplemented with live cells of probiotic bacterial strains: Lactobacillus casei and paracasei. This new milk chocolate displayed the same sensory...
The modified CPEM (cooked potato effective mass) method: an instrumental assessment of potato sloughing
Anna Hejlová, Jiří Blahovec
Czech J. Food Sci., 2010, 28(5):407-411 | DOI: 10.17221/225/2008-CJFS
The cooked potato effective mass (CPEM) method for potato sloughing assessment involves cooking the potato flakes on the sieve in a stirred water bath and periodically determining their effective mass during cooking. The final cooking curve divided into the cooking and breaking parts provides two parameters: the cooking time (CT) is the time required for starting disintegration, while the slope of the breaking part (SBP) describes the disintegration rate. The method enables a detailed analysis of the cooking properties in relation to the tuber density. The modified analysis of the cooking curve is based on polynomial approximation...
Contents of major phenolic and flavonoid antioxidants in selected Czech honey
Jaromír Lachman, Alena Hejtmánková, Jan Sýkora, Jindřich Karban, Matyáš Orsák, Barbora Rygerová
Czech J. Food Sci., 2010, 28(5):412-426 | DOI: 10.17221/202/2009-CJFS
The chemical constitution of antioxidants contained in honey is derived from its origin. Forty honey samples (harvest 2006), which came from various locations of the Czech Republic and varied in their origins, were evaluated spectrophotometrically for their total polyphenol content, total flavonoids and 3',4'-dihydroxyflavones and flavonols, and major antioxidants were identified by HPLC-DAD and GC-MS. The kind of honey, location, and date of the honey harvest were shown to have a significant effect on the contents of phenolic antioxidants (average content 11.02 mg gallic acid equivalents/100 g), total flavonoids (0.66 mg quercetin equivalents/100...
Rapid detection of dimethyl yellow dye in curry by liquid chromatography-electrospray-tandem mass spectrometry
Fernando Tateo, Monica Bononi, Franco Gallone
Czech J. Food Sci., 2010, 28(5):427-432 | DOI: 10.17221/135/2009-CJFS
An accurate and rapid method, was devised for the identification and quantitation of dimethyl yellow dye in curry, based on liquid chromatography-tandem mass spectrometry interfaced with electrospray. Mass spectral acquisition was done in positive ion mode applying two fragmentation transitions to provide a high degree of selectivity. The extraction system provided a very high recovery (100.0% to 105.8%) and good results were obtained for the limit of detection (5 μg/kg) and limit of quantitation (16 μg/kg). The applicability of the method to identifing and quantifing the unauthorised dimethyl yellow dye in curry was demonstrated.
The effects of rheological properties of wall materials on morphology and particle size distribution of microcapsule
Yanli Xie, Airong Wang, Qiyu Lu, Ming Hui
Czech J. Food Sci., 2010, 28(5):433-439 | DOI: 10.17221/49/2009-CJFS
The effects of rheological properties of the wall materials on the morphology and particle size distribution of microcapsules prepared by spray-drying were evaluated. Gelatin-sucrose (Gel-Suc), gelatin-peach-gum-sucrose (Gel-PG-Suc), and HI-CAP 100 were used as wall materials with vitamin A as a model core material. Scanning electron microscopy (SEM) showed that microcapsules produced with Gel-Suc exhibited cracks while Gel-PG-Suc produced a smooth surface with few pores, and HI-CAP100 a rounded surface containing characteristic concavities. The volume average diameter (D4,3) showed significant variations from 73.9 ± 1.02 µm...
Occurrence of biogenic amines and amines degrading bacteria in fish sauce
Muhammad Zukhrufuz Zaman, Fatimah Abu Bakar, Jinap Selamat, Jamilah Bakar
Czech J. Food Sci., 2010, 28(5):440-449 | DOI: 10.17221/312/2009-CJFS
The contents of biogenic amines histamine, putrescine, and cadaverine in fish sauce were determined and the bacteria isolated from the samples were evaluated for their amines degradation activity. Five fish sauce samples contained 62.5-393.3 ppm of histamine, 5.6-242.8 ppm of putrescine, and 187.1-704.7 ppm of cadaverine. Thirty three bacterial isolates produced all three amines, seven isolates produced one or two amines, and one isolate did not produce any amine in differential agar media. Since the strains that produced amines were not supposed to degrade them, only eight isolates were further identified and evaluated for their amines degrading capability....
Microbial contamination after sanitation of food contact surfaces in dairy and meat processing plants
Jarmila Schlegelová, Vladimir Babák, Martina Holasová, Lucie Konstantinová, Lenka Necidová, Frantisek Šišák, Hana Vlková, Petr Roubal, Zoran Jaglic
Czech J. Food Sci., 2010, 28(5):450-461 | DOI: 10.17221/65/2009-CJFS
The occurrence of Listeria monocytogenes, Salmonella spp., Bacillus cereus, Staphylococcus spp., Enterococcus spp., and Escherichia coli in raw food materials, food products, and on food contact surfaces after sanitation was investigated during the period of 2005-2006 in three dairy cattle farms (120 samples), one dairy (124 samples), and two meat processing plants (160 samples). A total of 1409 isolates were identified. The epidemiological characterisation and determination of the virulence factors and antimicrobial resistance were performed on selected isolates. The level of bacterial contamination generally decreased...
Thermoelectric effect on potato tuber (Solanum tuberosum L.) - short communication
Světla Vacková, Josef Vacek
Czech J. Food Sci., 2010, 28(5):462-464 | DOI: 10.17221/73/2010-CJFS
For scaning rheological properties of tuber tissue during heating, different physical techniques are used. The experiments done on low solids tubers of cv. Magda have shown that maximum thermoelectric effect was obtained at about 60°C in the temperature region where the gelatinisation process of intra-cellular starch starts and some few cell disruptions occur.