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Yellow, orange, red and brown pigments are formed by air oxidation of single polyphenols or by thermal degradation of sugars to caramels. Caramels increase their colours during anaerobic heating or decrease them by air oxidation. Epicatechin and caramel undergo reversible redox reaction followed by degradation and/or polymerisation at beer aging. That is why both of these colour compounds, besides acting as acid/alkali indicators, can also represent redox indicators that gradually become irreversible. These reactions are accelerated by transient metals or buffering solutions and are therefore more distinct in tap or brewing water than in deionised water. The kind of the brewing water then predetermines not only the beer attributes but also the course of beer aging. Coloured pigments can be partially bleached by reducting agents such as yeast oxidoreductase enzymes and the colour can be then recovered by oxidation; this depends on their polymerisation degree. Methylene blue and methyl red can be used as artificial oxidation-reduction indicators for the study of the redox potential changes because they act reversibly or irreversibly under aerobic or anaerobic conditions, respectively.

The Maillard reaction, or nonenzymatic browning, includes a complex network of reactions initiated by the condensation reaction of a carbohydrate and an amino compound, and is of utmost importance for the formation of flavour and colour in thermally treated foods. Besides volatile flavour compounds, also brown-coloured polycondensation products, named melanoidins, are produced. In latest years, the interaction of lipid oxidation products in the classical Maillard reaction pathway and vice versa is of particular interest, since it has been shown that the course of both reactions can be modified by the reactants, intermediates and products of the other (ZAMORA & HIDALGO 2005). Therefore, in parallel with the formation of model melanoidins, polycondensation products resulting from the interaction of amino acids with lipid oxidation products were studied. For this purpose, various coloured water-soluble high molecular weight and water-nonsoluble reaction products were isolated from the model reactions of glycine or lysine with a lipid oxidation product (hexanal, (2E)-hexenal, (2E,4E)-decadienal) in the presence or absence of glucose. They were characterised by UV-visible absorbance measurements, elementary analysis, and thermal degradation followed by SPME-GC-MS analysis (ADAMSet al. 2003). The UV-visible absorbance spectra before and after dialysis indicated that the most important contributors to the formation of water-soluble coloured material were constituents of the low molecular fraction. Elementary analysis data showed that a higher amount of nitrogen was incorporated in the high molecular weight fractions as compared to the water-nonsoluble fractions, except for the water-nonsoluble reaction products from amino acid/(2E, 4E)-decadienal interactions, which demonstrated the lowest C/N ratio found. Volatile carbonyl compounds, furans, a liphatic compounds, pyridines, pyrroles and benzene derivatives were the main groups of compounds identified in the thermal degradation profile of each fraction tested. Aldol condensation reactions of the carbonyl compounds were very important in the initial reaction steps. Especially pyridines seem typical indicators of amino acid-lipid oxidation product interactions.

Cocoa liquor used in the confectionery industry comes from a wide range of geographical areas and may have different chemical compositions, sensory properties, and nutritional values. We found it interesting to study the polyphenolic content and composition of cocoa liquors for their potential use in industrial production. Six defatted samples originating from different countries were extracted with aqueous methanol (70%, v/v), and the polyphenolic profiles were determined using RP-HPLC method. According to our results, all samples of cocoa liquors have similar polyphenolic profiles, however, quantitatively varied. In the samples, about 13 compounds were identified by comparison of their retention times and UV spectra, and the quantified peaks were (+)-catechin, (-)-epicatechin, (-)-gallocatechin, (-)-epigallocatechin, caffeic acid derivative, caffeine, and theobromine. Also, several peaks were identified as oligomeric procyanidins. The free-radical scavenging activity was determined by the DPPH* (1,1'-dipheny-2-picrylhydrazyl) and Oxygen Radical Antioxidant Capacity (ORAC) assays. The order of antioxidant activity of the cocoa liquors studied was the same with both methods (Madagascar > Mexico > Ecuador > Venezuela > Sao Tome > Ghana samples). In addition, correlation between the antioxidant capacity and polyphenolic content was also determined, a high correlation coefficient having been obtained by both methods (R^{2 = 0.9868 for DPPH, and 0.9375 for ORAC).}

Phytosterols and -stanols are added to food products because of their known ability to lower serum cholesterol levels. They are applied either in their free or esterified forms, i.e. as fatty acid esters. Sterols are known to form variety of oxidation products under exposure to heat, light and metal contaminants, for example in food processing conditions. Since these oxides may have adverse health effects, the oxidation process needs to be studied. Until recently, sterol oxidation studies have concentrated on following the formation of secondary oxidation products in free sterol and steryl esters, but little is known about the oxidation of steryl esters as intact molecules. The aim of this experiment was to study primary autoxidation of intact steryl ester by measuring hydroperoxide formation in bulk cholesteryl ester. Cholesteryl linoleate was maintained at 60°C for 0-72 h after which formed hydroperoxides were determined with normal phase high performance liquid chromatography connected to diode array detector (HPLC-DAD). Also peroxide value (PV) was measured to indicate the total amount of formed hydroperoxides. With HPLC method steryl ester -OOH's could be analysed as intact esters, without saponification. A gradient elution was performed with 0.3-10% methyl-tert-butyl ether (MTBE) in heptane followed by cleanup with 30% MTBE. Compounds were detected with DAD at wavelengths 206 nm and 234 nm. Peroxide value indicated that the formation of hydroperoxides reached the maximum after 12 h of prolonged heating. According to HPLC data, at this time point less than 10% of the hydroperoxide groups were located in the sterol moiety and more than 90% in the fatty acid chain. The proportion of sterol-OOH's increased as the heating continued; at 24 h 20% and at 48 h 30%. However, after 72 h no hydroperoxides were observed. In conclusion, oxidation of cholesteryl linoleate started in the fatty acid moiety and as the reaction progressed more of the sterol -OOH's were observed, though at all time points fatty acid -OOH's were dominating.

Atomic absorption spectrometry is a powerful technique for determination of tin in canned foods. Homogenous samples of syrup and solid parts were digested by means of microwave digestion system MLS 1200 MEGA where hydrochloric and nitric acid were used as reagents. The measurements were carried out using a Perkin-Elmer AAnalyst 700 atomic absorption spectrometer. Detection limit was 4 mg/kg in nitrous oxide and acetylene flame. There were analysed 222 samples of 26 various kinds of canned fruit (e.g. pineapple, peach, mandarin), vegetables (e.g. bean, mushroom, tomato) and meat (sea products) in this work. The analytical results indicated tin total concentrations from under 4 mg/kg to 353 mg/kg. Different concentrations of tin between syrup and fruit were observed. The concentration of tin was higher in solid parts than in syrup. Relationship between the concentration and time period after opening was studied. The corrosion of the tinplate surface was accelerated by air and the amount of dissolved tin was significantly increasing in syrup as well as fruit when cans were opened and stored for two days at 6°C.

The influence of microwave heating (microwave oven Electrolux, 2450 MHz, 400 W) from 8 up to 24 min on the oxidation and fatty acid composition of lipids of common carp (Cyprinus carpio) and Atlantic mackerel (Scomber scombrus) minced fish flesh were studied. The heating treatment at all conditions reduced moisture and therefore, increased lipid and dry matter contents. The isolated lipids were subjected to the following analyses: peroxide value, acid value and content of conjugated dienes (by absorbance at 232 nm). The free fatty acid content in the lipid fraction of the fish flesh was significantly reduced by cooking. Conjugated diene levels in fish muscle increased and peroxide values decreased for all cooked samples. Changes in fatty acids composition were only small.

Total starch (TS), amylose and resistant starch (RS) were determined in the sets of smooth pea and wrinkled pea varieties in the years 2006-2008. Starch content of smooth peas varied in the range 53.61-57.23%. Average amylose content was 27.8%. Resistant starch content varied from 2.07% to 6.31%. Content of starch at wrinkled pea varied from 26.57% to 32.55%. Average amylose content was 76.82% of total starch. Content of total starch increases continually during seed development. The dependence of total starch on determined dry mass in harvested sample can be defined by equation γ = 1.2427 × -6.5611, by determination coefficient R² = 0.8936 and highly significant correlation coefficient r = 0.945. Total starch content in dry seed reached final average value 29.56%. In garden pea, the level of maturity (by tenderometric measurement) and dry matter were determined. Resistant starch content of 11 garden pea cultivars was studied in three different terms of technological harvest.

The presence of masked or hidden forms of Fusarium mycotoxins (deoxynivalenol, DON, zearalenone, ZEN and fumonisins B1, B2 and B3) were studied in wheat and maize derived products. Significant amounts of these forms were found both in raw and in processed food commodities. Deoxynivalenol-3-glucoside was found in wheat products up to 30% of DON concentration. Bound forms of fumonisins often account for an equal or even higher amount in comparison with the free forms.

Comparative study was conducted on the basis of free amino acids and biogenic amines of Hungarian sparkling wines originated from 3 producers (Törley, Hungária, Balaton Boglár). Determination of amino acids and biogenic amines was accomplished by ion-exchange chromatography using an amino acid analyser. The dominant free amino acids in sparkling wines were proline and arginine and the major biogenic amine was spermidine. Based on results of chemometric analyses, free amino acid and biogenic amine contents seemed to be closely related to quality and the technology of sparkling wine making.

The objective of this research was to evaluate the effect of blackcurrant mash blended with apple pulp during juice production and storage on its phenolic composition, antioxidant activity, L-ascorbic acid, and colour. Five variants of samples were prepared: apple juices from two cultivars: the Shampion and Idared cultivars without and with 20% of blackcurrant pulp and blackcurrant juice which were stored at 4°C and 30°C for 6 months. The apple juices prepared from the Idared and Shampion cultivars had a very low L-ascorbic acid contents (1.32 mg/l and 6.26 mg/l, respectively) whereas blackcurrant juice showed the highest amount of L-ascorbic acid, i.e. 704.3 mg/l. The addition of 20% of blackcurrant pulp before apple crashing resulted in a great difference between L-ascorbic acid contents in juices. The addition of blackcurrant fruits before apple crushing had a statistically significantly different (P < 0.05) influence on phenolic compounds, especially in Idared blended pulp. As compared with the control samples, flavan-3-ol concentration increased 4 times in juices made from 80% of Idared apples blended with 20% of blackcurrant fruits. Apple pulp blended with blackcurrant was richer in hydroxycinnamic acids (especially caffeic, p-coumaric, and neochlorogenic acids) than juices made only from apples. The results ranged from 83.05 to 3297.6µM T/100 ml for DPPH (1,1-diphenyl-2-picrylhydrazyl radical), from 20.64 to 490.93µM T/100 ml for ABTS (2,2'azinobis-(3-ethylbenzthiazoline-6-sulphonic acid)), and from 1.52 to 37.35µM T/ml for FRAP (Ferric reducing antioxidant power assay) for apple juice made from the Idared cultivar and for blackcurrant juice, respectively. The highest level of the antioxidant capacity (P < 0.05) observed in the blackcurrant sample was due to the effect of the high anthocyanin and ascorbic acid contents. The apple juice colour showed a moderate degradation with time as indicated by the slight reduction of L* values in the samples stored at 4°C for 6 months, and a much higher decrease of L* values in the samples stored at 30°C. The lightness of the apple blended with blackcurrant increased during storage as a result of the coloured anthocyanin degradation. The temperature during the sample storage (30°C) had a significant influence, resulting in a higher degradation of all phenolics compounds analysed, colour and antioxidant activity.

Objective of this work was determination of processing contaminant known as 3-MCPD (3-chloropropane-1,2-diol) in its free and bound form in breads with defined parameters of processing. Selected and analysed were 24 samples, which represented two sets of breads produced in bakeries equipped with a continual line. In all cases determinations were carried out for breadcrumb and crust separately. The first set of samples were wheat-rye breads produced chronologically in ten days in the bakery Michelská pekárna, slightly different in temperatures and times of baking. The second set contained 14 samples of wheat-rye breads with a content of rye flour less than 40% differing in the yeast type and acidity. These breads were produced in the bakery Kontinua. The fat content was determined in all samples by Soxhlet extraction. Free and bound 3-MCPD was determined by gas chromatography-mass spectrometry method. Concentration of free 3-MCPD in samples was at interval < 9-54.5 μg/kg. Concentration of bound 3-MCPD was at interval 1.56-23.60 mg/kg of fat (i.e. 5.7-84.9 μg/kg of sample).

A scientific shelf-life study for Listeria monocytogenes in the typical Slovak cheese "bryndza" was performed in accordance with the requirements of the Commission Regulation (EC) 2073/2005. Based on the previous positive findings of L. monocytogenes in the final products, the producer decided to perform laboratory tests, the results of which would allow him a different evaluation of these positive results. Both the physico-chemical (pH, a_w) and microbiological examinations of "bryndza" cheese stored at 5.8-6.2°C were performed every two days till the end of the product shelf-life (7 days). Microbiological analyses were performed after artificial contamination of the final product with a mixture of three L. monocytogenes strains. The growth potential of L. monocytogenes was calculated as the difference in the counts of this bacterium between the last day and the first day of the test. The Slovak traditional "bryndza" cheese has been found not to support the growth of L. monocytogenes. Thus, the counts of L. monocytogenes must not exceed 50 CFU/g at the beginning and 20 CFU/g at the end of the product shelf-life in order to ensure its safety for the consumer.

The addition of plant proteins into meat products is nowadays a commonly used practice especially for the technological and economical reasons. Their properties have been known and used in meat products production for a long time. In the past, wheat protein or flour had been used most frequently, however, in these days they are being replaced by soya protein which has much more favourable properties in its use. Considering the possible misuse of raw materials of plant origin for the adulteration of meat products, the existence of highly sensitive and accurate procedures for their detection is needed including the determination of their content. Soya protein can be detected using various methods. In our work, an immunohistochemical method was used with image analysis for the quantification of soya protein. Model meat products with the addition of known amounts of soya protein in various forms were made for this experiment.

As far as honey is concerned, microwave oven heating finds its use especially for crystallised honey reliquefying. We focused on monitoring the changes in hydroxymethylfurfural content which is an indicator of heat damage done to honey, among others. Microwave honey heating was carried out in four degrees of microwave power levels over seven variously long time periods. In total, 22 analysed honey samples came directly from bee-keepers from the Czech Republic from the 2004 and 2006 harvests. Hydroxymethylfurfural content was determined by HPLC method using a liquid chromatograph Alliance 2695 with a PDA detector 2996. We obtained relatively interesting results: despite the honey having reached relatively high temperature levels (80-90°C) at the highest power levels and the longest time periods, there was no gradual significant increase in hydroxymethylfurfural content which could be expected at conventional heating. On the other hand, hydroxymethylfurfural content varied in the course of heating of the individual samples, which is a very interesting result. A significant role was played also by the botanic origin of the honeys because the course of the changes in hydroxymethylfurfural content due to microwave heating was not the same in all honeys analysed.

The sources of reducing sugars and free asparagine of two different cracker products were identified, and acrylamide formation during baking was measured. The application of an asparaginase decreased the acrylamide content by at least 70% in both products. Replacing ammonium hydrogencarbonate by sodium hydrogencarbonate as baking agent and replacing reducing sugars by sucrose resulted in almost 80% less acrylamide in the wheat cracker. Decreasing free asparagine and reducing sugars in the ingredients and a lower end-temperature during baking lowered the acrylamide content of the potato cracker by about 50%.

The effects of inulin HPX and maltodextrins, and also the potentially probiotic Lactobacillus plantarum 14 strain, used separately and in combination in white cheese production, on the gastrointestinal microflora of Wistar rats was investigated. The prebiotic addition to the cheese was 2.5%, whereas probiotic and synbiotic cheeses contained at least 10⁷ CFU/g of live L. plantarum cells. The counts of Bifidobacterium sp., Lactobacillus, coliforms, and the most probable number of anaerobic proteolytic bacteria were evaluated. After a 10-day feeding experiment, significant changes (P < 0.05) were noted in the most probable number of anaerobic proteolytic bacteria spores, which was the highest in the group receiving a diet with the cheese containing the potentially probiotic strain and inulin HPX. A short-time ingestion of low doses of prebiotics or synbiotics did not alter the counts of Lactobacillus, Bifidobacterium, and coliforms in healthy rats.

The applicability was evaluated of 16 different oats species and varieties of different provenance in the coeliac diet in view of the composition of the protein complex and immunological testing during two-year experiments (2001 and 2002). Determination was carried out of total nitrogen content (average of evaluated oats collection in 2001 was 2.21%, in 2002 2.78%), protein nitrogen content (average 2001 1.94%, 2002 2.28%), and crude protein (N × 6.25) content (average 2001 13.80%, 2002 17.37%). The proportions of different protein fractions play a decisive role for the aims of this study because, based on the existing knowledge, coeliacally active protein components are present particularly in the prolamin fraction. The percentage of prolamins (determined by discontinual fractionation after Osborne) in the author's evaluated collection of oats species and varieties under the conditions of Central Bohemia reached on average 17.68% of the total protein in 2001, and 15.36% in 2002. The average percentage of albumins and globulins of the total protein reached 36.97% in 2001 and 41.04% in 2002, the average percentage of glutelins of the total proteins was 37.61% in 2001 and 34.10% in 2002, and residual was on average 7.55% in 2001 and 8.70% in 2002, respectively, of the total protein. Electrophoretic analysis of reserve (gluten) proteins (SDS-PAGE ISTA) showed in the oats collection evaluated the percentage of LMW + prolamins in the range 56-77% of the total reserve proteins in 2001, and 52-73% in 2002. The results of A-PAGE electrophoretic analysis of prolamin proteins confirmed the presence of α-prolamins, that ranged in the total content of prolamins from 50 to 88% in 2001, and from 77 to 100% in 2002, while β- + γ-prolamins ranged in 2001 from 11 to 49%, and in 2002 from 0 to 22%. These values do not give serious guarantees for the possible utilisation of oats in the gluten-free diet. The results of the immunological evaluation of the amount of prolamins in oats grains using ELISA showed great differences between different varieties and the experimental years. In 2001, 7 oats samples out of 13 evaluated, and in 2002 10 samples out of 12 evaluated were below the limit for the gluten-free diet (10 mg prolamins (gliadins)/100 g of sample dry matter), but the other varieties exceeded the limit, particularly in 2001, very significantly. The results obtained in the evaluated collection of species and varieties of oats revealed a great variability in the structure of the protein complex and in the immunological testing. In addition a significant effect of the year on the results of all analyses was evident. Based on our results, the use of oats in the diet for coeliac disease can be very risky for these reasons.

The purpose of this study was to investigate the relationship between the carcass weight and the level of skatole in boar back fat samples with descriptive sensory profiles (trained sensory panel) immediately after heating the fat samples (warm). A weak correlation was found between the carcass weight and skatole level in fat (P > 0.05). Between skatole levels in the fat of boars, whose carcass weight was below 70 kg, and of those with the carcass weight equal or above 70 kg, there was a statistically significant difference (P < 0.05). The average content of skatole in the fat tissue of the boars < 70 kg, (0.18 ± 0.09 mg/kg fat, respectively) was below the commonly used respective thresholds for tainted meat (0.20 mg/kg fat), 53% of the samples showed the values of ≤ 20 mg/kg, and 73% of the samples the values of ≤ 25 mg/kg. In the group ≥ 70 kg (0.40 ± 0.39 mg/kg fat, respectively), 80% of the samples revealed the values of ≥ 20 mg/kg, and 66% of the samples the values of ≥ 25 mg/kg. Our results show that a positive, compelling and statistically highly significant correlation exists between the skatole level and the sensory assessment of skatole intensity in fat.

The sera from 690 slaughtered fattening pigs from 15 farrow-to-finish swine herds (12 herds of unknown Salmonella status, 3 herds known as latently infected) in the Czech Republic were examined for Salmonella antibodies in a cross sectional study using an ELISA test. Salmonella seroprevalence ranging from 0% to 20% was found in 14 herds. Seroprevalence of 73.9 was found in 1 herd with previously unknown Salmonella status. A longitudinal study of the three previously identified latently infected herds found seroprevalence ranging from 23.9% to 83.4% in sows after farrowing. Salmonella findings from faeces in the farrowing sections ranged between 1.8 and 24.5, and in the environmental samples between 0 and 25. In weaned piglets, Salmonella findings from faeces ranged from 6.3 to 48.0, and in environmental samples from 0 to 90%. The most prevalent serotypes were S. Derby (56.8) and S. Typhimurium, phage type DT104 (18.5). The seroprevalence comparison in sows and slaughtered fattening pigs revealed variations in the course of Salmonella infection in swine herds.

The aim of this project was to study changes in the content of trans-resveratrol in berries and leaves of grapevine (Vitis sp.) infested by fungal diseases, especially by Botryotinia fuckeliana Whetzel, called as grey mildew, Plasmopara viticola (Berk. & M.A. Curtis) Berl & De Toni, called downy mildew and Uncinula necator (Schw.) Burr, called powdery mildew. In our experiments two white and two blue varieties were used. Contents of trans-resveratrol were determined in healthy and infested leaves and in healthy berries. Infested leaves of white varieties contained more trans-resveratrol than those of blue varieties. The content of trans-resveratrol in berries was lower than that in leaves.

White wines of Debina cultivar were made from musts clarified by flotation using nitrogen as foaming agent. Flotation using air as the foaming agent (must hyperoxidation), without SO₂ addition, was also applied. Turbidity and suspended solids were lower in must clarified by flotation using nitrogen than in that clarified by sedimentation (control). Flotation with hyperoxidation led to a reduction of must phenolics. All experimental wines exhibited similar gross compositions (alcohol, reducing sugars, total acidity, and volatile acidity). Wines made from musts clarified by flotation using nitrogen had similar total phenolic content, browning capacity, and organoleptic quality as the control wines. Wines made from musts clarified by flotation using air had lower total phenolic contents and browning capacity than were those in control wines. These wines were of well acceptable quality but exhibited a slightly oxidised aftertaste. The results indicate that flotation using nitrogen can be effective in the production of typical Debina wine, while flotation using air may be useful in that of table wine without SO₂ addition. Orange juice was clarified by flotation using nitrogen or air as the foaming agent. Orange juice clarified by flotation using nitrogen as the foaming agent exhibited lower turbidity and a similar pulp content to that clarified by centrifugal separator (control). It had an acceptable taste and aroma. Juice clarified by flotation using air as the foaming agent, along with pectolytic enzyme treatment, exhibited much lower turbidity and pulp content compared to control. The clear juice had an acceptable taste but no aroma. The fermented clear juice was averagely rated, exhibiting a pleasant aroma and only a slightly bitter taste. The results indicate that flotation using nitrogen can be effective in the production of natural orange juice, while flotation using air may be useful in the production of orange drink.

The main chemoprotective polyphenolic compounds in the Vitis vinifera berries, rachis, and pedicels of 10 cultivars classified for the production of wine and growing in Southern Moravian vineyards, the Czech Republic, were studied. The following compounds were determined in the frozen fresh berries: gallic acid (1.8-13.3 mg/kg), catechin (70.3-659.1 mg/kg), epicatechin (67.1-237.2 mg/kg), trans-resveratrol (0.1-1.5 mg/kg), and pterostilbene (in traces); in the freeze-dried rachis and pedicels: rutin (10.5-68.6 mg/kg), isoquercitrine (29.8-218.3 mg/kg), catechin (283.7-2227 mg/kg), epicatechin (47.2-215.2 mg/kg), trans-resveratrol (2.6-37.1 mg/kg), and pterostilbene (0.01-0.13 mg/kg), respectively. The contents of polyphenolic compounds were different in various cultivars. The highest levels of catechin and epicatechin were found in the grapes of cv. Blauer Burgunder (3195 mg/kg), in which the second highest content of trans-resveratrol (33.2 mg/kg) was also found. The content of pterostilbene in the whole berries or stems was estimated for the first time. The rachis and pedicels could serve as a prospective source of polyphenolic compounds.

Experimental samples simulated the composition of vermouths. In all experiments, 0.01% quinine was used as a standard bitter substance. Sucrose increased the acceptability in the concentration range of up to 14%, remaining constant at higher concentrations, both in aqueous and 16% ethanolic solutions. A decrease of bitterness was observed in water but not in 16% ethanol. Ethanol did not affect the sweetness appreciably at the concentrations of up to 16%, but 32% ethanolic solutions appeared less sweet. Ethanol enhanced the bitterness only at high concentrations; interactions were similar in the samples containing 10% and 16% sucrose. Aspartame and Neotame sweetness increased the acceptability and decreased the bitterness similarly to sucrose, both in aqueous and in 16% ethanolic solutions.

A precise design of the equipment for thermal sterilisation of rice, potato starch, and oat flakes by dry heat requires the knowledge of the relevant values of physical properties of these products. Water activity and enthalpy are presented as functions of temperature and humidity. Water activity was measured as a function of the moisture content and temperature in the desorption process that reproduces the real conditions existing during dry heat processing in the pilot rotating steriliser equipment. The heat of evaporation can be predicted from these data as a function of the moisture content of these products. DSC (differential scanning calorimetry) method was used for measuring the enthalpy of these products as a function of temperature during desorption of moist products starting from various levels of the moisture content. The total energy Ec necessary for heating the product and evaporation of the given amount of water can be calculated.

Grape anthocyanins not only play an important role in the colour quality of red wines but they also have many beneficial effects on human health, e.g., reduction of coronary heart disease incidence, or anticarcinogenic and antioxidant properties. Therefore, a rapid and efficient extraction technique prior to chromatographic analysis is of primary interest. Pressurised Fluid Extraction (PFE) presents a fast, effective, and environmentally friendly extraction method for the analysis of red grape pigments. In this study, PFE in static mode was utilised for the extraction of 3-monoglucoside anthocyanins from the grape skin of highly pigmented variety Alibernet. The effects of the type of the extraction solvent and the extraction temperature were studied. The identification of the above given compounds were performed by high-performance liquid chromatography with diode array detection (HPLC-DAD) based on Synergi C-12 column separation. The wavelength was set at 520 nm. All compounds were determined and identified during 50 minutes.

Oxidation changes of different types of vegetable oils were studied during microwave heating. Samples of vegetable oils (rapeseed, sunflower, soybean and corn oil), commercially available at the market in the Czech Republic, were heated in a microwave oven. Parameters as peroxide value, conjugated dienes and trienes levels were determined in oil samples before and after heating in the period from 3 to 30 minutes.

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 during the production process (the contamination of food products was lower than that of raw material). However, the contamination of food contact surfaces was relatively high even after sanitation. Moreover, specific microbiological profiles were found on the inside equipment surfaces in dairy facilities, where genetically closely related multi-resistant strains persisting in biofilm communities may occur as demonstrated for staphylococci. Although the occurrence of potentially significant pathogens was not high, the microorganisms such as L. monocytogenes, Salmonella spp., and shiga-toxin positive E. coli principally contaminated the meat processing plants. B. cereus isolates, among which 76% were positive for diarrhogenic enterotoxin, typically occurred on the inside equipment surfaces and in the heat-treated products.