Fulltext search in archive

The content of free SO₂ (1.3-37.9 mg/l and 5.3-19.7 mg/l for 2009 and 2010) and total SO₂ (38.3-272.0 mg/l and 52.0-102.1 mg/l for 2009 and 2010) for individual wines was in a broad interval. Results of free SO₂ found using the commercial SO₂ reagent were higher than our results since the reagent determined not only free SO₂ but also reductones. The content of titrated acids was constant with a very moderate time decrease and the values were on average about 9.1-5.3 g/l (2009) and 13.1-7.9 g/l (2010). Similarly, the content of tartaric acid was nearly constant and the values were on average about 2.37-1.47 g/l (2009) and 6.65-2.69 g/l (2010). The percentage ratio of tartaric acid in the content of titrated acids is also constant (average 24.39%-38.6% for individual wines).

We determine the effects of the technology of obtaining potato protein preparation and of different variants of enzymatic hydrolysis on the chemical and amino acid compositions of the hydrolysates obtained. Potato protein concentrates obtained through their thermal coagulation in potato juice with calcium chloride, calcium lactate or without salt addition were subjected to enzymatic hydrolysis using two commercial hydrolytic enzymes: endopeptidase (Alcalase) and exopeptidase (Flavourzyme). Chemical (contents of ash, total and coagulable protein) and amino acid compositions of the hydrolysates obtained were determined. On the ground of the findings it was stated that the type of potato protein preparation used and conditions of enzymatic modification influenced on the properties of the hydrolysates obtained. Preparations obtained during the study were characterised by similar chemical and amino acid compositions, whereas the preparation obtained through thermal coagulation with the use of calcium lactate contained insignificantly more protein and essential amino acids. The least liable to enzymatic hydrolysis was the preparation obtained by using calcium chloride, particularly when only endopeptidase was used. The application of endopeptidase enzyme enabled to obtain 60% of proteolysis efficiency and the addition of the second enzyme (exopeptidase) to the protein solution insignificantly increased the proteolysis efficiency (to ca 70%), mainly when the preparation coagulated with the use of calcium chloride was hydrolysed. Proteolysis of the protein preparations obtained with the use of two enzymes was more favourable, particularly due to the quantity of free amino acids in and amino acids composition of the hydrolysates.

We evaluated the effects of Gymnorhynchus gigas on the freshness and hygienic quality of Lepidopus caudatus. Total Volatile Basic Nitrogen (TVB-N), Trimethylamine Nitrogen (TMA-N), as well as Specific Spoilage Organisms (SSOs) are the most important freshness indicators in fish. Our study was carried-out on 65 specimens of L. caudatus kept in ice and stored at 2°C for different period of time. The microbiological charge of SSOs recovered on a portion of parasitised muscles (MP) was compared with those recovered on portions of parasite-free muscles (M). The contents of TVB-N and TMA-N on MP, M, and G. gigas larva/ae were measured using the Conway microdiffusion method. High prevalence (72.31%) of G. gigas in the specimens of L. caudatus from the Mediterranean sea was observed. No statistically significant differences (P < 0.05) between M and MP were found during storage. However, massive infestation of G. gigas on the muscle of the silver scabbardfish could negatively influence TVB-N values, without compromising the sensorial characteristic of fish.

The results of chemical and microbial analyses of raw milk samples coming from organic and conventional farming systems were statistically compared. The samples were analysed during a twelve-month period (June-May). A total of 2206 samples were collected of which 528 were organic. After raw milk was processed, sensory hedonic quality of 171 pairs of organic and conventional non-standardised pasteurised whole milk samples were evaluated using the pair comparison preference test. Four parameters in raw milk, free fatty acids, urea content, somatic cell count and coliform bacteria count, showed no significant differences between the two types of production. Significantly higher contents of protein, casein, lactose, and non-fat solids were detected in conventional milk, which also had a significantly lower freezing point. On the contrary, significantly higher contents of total mesophilic bacteria count and a higher percentage of samples with positive coliform bacteria count were found in organic milk samples. Sensory analysis of pasteurised milk showed no significant hedonic difference between organic and conventional samples.

Cooking and drying conditions of the shea butter extraction process were determined using a response surface methodology. The influence of cooking time, temperature, and nuts/water mass ratio, drying time, and temperature on the content of free fatty acids, the peroxide value, as well as on the extraction yield was investigated. Results showed that both the free fatty acid content and the peroxide value were significantly affected by cooking and drying temperature; the cooking time and nuts/water ratio also affected significantly the peroxide value. Increasing cooking and drying temperature reduced the FFA content but contributed to increase the peroxide value. The cooking and drying temperature range of 75-80°C and < 54°C, respectively; cooking time of 70-100 min; drying time < 40 h, and cooking nuts/water mass ratio < 400 g/l of water were found to be optimum conditions for the extraction of shea butter.

The aim of this work was to characterise influence of whey proteins-pectin interaction on emulsification properties of whey. As the first, structural characteristics of pectin-protein complexes were evaluated for pure β-lactoglobulin by both dynamic light scattering method for measuring of the particle size distributions and Doppler laser electrophoresis for measuring the ξ-potential (surface electrical potential) of particles. In mixed pectin-β--lactoglobulin systems, it was observed that the addition of pectin prevent from the protein-protein interaction, which caused production of huge protein aggregates (2000-2500 nm) at pH values near β--lactoglobulin isoelectric point and at temperatures near its denaturation temperature. However, these protei-pectin complexes had large hydrodynamic diameters (monomodal size distribution at 350 and 1000 nm for high esterified and low esterified amidated pectin, resp.), which can slow down their diffusion to the oil-water interface in emulsions. The ξ -potential values indicated improvement of colloid stability by addition of pectin. The evaluation of the influence of the protein-pectin interaction on emulsification properties was performed by the determination of a surface weighted mean (D [3,2]) of oil droplets in o/w emulsions measured by the laser diffraction, further by microscope observations, the determination of emulsion free oil content and observations of creaming. The emulsifying properties were influenced by the pectin addition, more negatively by the high esterified than by the low esterified amidated pectin addition.

This work aimed at analysing bread extracts obtained under headspace and artificial mouth conditions in order to study the reactions responsible for bread flavour quality. Selected extraction conditions were first compared according to the odour and aroma representativeness of the bread extracts. The optimal conditions were then applied to extract volatiles of a conventional gluten bread formulation and an innovative gluten-free bread formulation. Results reveal that an extraction duration of 10 min in the artificial mouth was sufficient to obtain a representative aroma extract. Yet, 30 min of headspace extraction were necessary to obtain a representative odorant extract. The comparison between these both extracts shows that significantly higher quantities of bread compounds were extracted with artificial mouth. This innovative device could thus be used to better understand the mechanisms involved in the formation of those volatiles that are responsible for the perceived bread odour and aroma.

Many studies show that the consumption of juices rich in polyphenols may increase serum antioxidant capacity, improve blood lipid profile, and endothelial function. The relation between the consumption of chokeberry juice and changes in the antioxidant capacity, blood lipid profile, and endothelial function as important indicators in the assessment of cardiovascular risk were determined. The study was conducted on a group of 11 healthy volunteers, who consumed chokeberry juice for three weeks. The research included determination of serum antioxidant capacity, blood lipid profile analysis, and measurements of endothelial function. The 3-week consumption of chokeberry juice significantly increased serum antioxidant capacity, and the best results were observed just after one week of the experiment. However, there was no significant change in the blood lipid profile, except for the persons with a higher level of triglycerides, in whom the consumption of chokeberry juice reduced these compounds to normal values. The endothelial function was normal in all patients and did not significantly change during the study.

The important nutritional characteristics of the Rubiota spelt variety, grown in the Czech Republic, were reported. We evaluated the contents of total dietary fibre, protein, wet gluten, total starch, and starch fractions, i.e. rapidly digested starch, slowly digested starch, and resistant starch in pearled grain of spelt and in pearling fines. We measured these properties depending on the degree of kernel abrasion. Small differences were found between the sequential pearling cycles in the pearled spelt but significant differences were observed in the fines. In this study we also compared two methods for determining total and resistant starch.

The technology of a functional fermented buttermilk-based beverage was developed and the impact of beverage consumption on the health parameters of young volunteers was studied. Three functional beverages were made on the basis of buttermilk, which differed in the composition. The beverage containing the buttermilk-skimmed milk-milk protein concentrate (0.3%) as a product with the preferred quality characteristics (synaeresis, viscosity, sensory properties, and acceptability) was used for further studies regarding the impact on human health. The medical nutrition experiments did not show any statistically significant effect on the biochemical blood parameters of 25 young volunteers after a 21-day period of the consumption of fermented buttermilk beverage with milk protein concentrate, although some of them (e.g. total, low- and high-density cholesterol, triacylglycerol concentrations, etc.) slightly decreased. The anthropometric and body composition, arterial blood pressure, and pulse evaluation indicators of recipients did not change significantly.

Durum semolina was replaced with 10, 15, and 20% of chestnut flour. Pasta was produced on a single screw extruder with the temperature profile of 80/90/90°C and on a laboratory minipress. Pasta samples were dried at room temperature and physical and sensory properties were determined. Generally, the chestnut flour addition to durum wheat pasta decreased optimum cooking time, hardness, cohesiveness, and chewiness, but increased cooking losses and pasta adhesiveness. Samples made on an extruder showed shorter optimum cooking times in relation to samples made on a minipress. Absorbed water was decreased with chestnut flour addition. Pasta made on an extruder showed a higher sensory score in comparison with pasta made on a minipress. The addition of chestnut flour influenced the colour of the samples. Samples made on an extruder showed darker colour in dried and cooked pasta samples in relation to minipress samples. In dried pasta samples, the extruder gave yellower samples in relation to the minipress, while in cooked pasta samples it was reversed. Overall, the extruder gave higher-quality pasta compared to the minipress.

The effects of red wine maturation on the contents of selected parameters of bioactive compounds in wine were determined. Samples of Alibernet, Cabernet Sauvignon, and Torysa wines were studied by spectrophotometric analysis after 3, 7, 11, 19, and 28 months of aging and the selected parameter content was statistically evaluated. Statistically highly significant changes in total polyphenol content, total anthocyanin content, antioxidant activity, and wine colour density were found depending on the aging according to the used statistical analyses. The obtained results can be used for the optimisation of the wine aging process and they allow producers to time the optimal date of wine release onto the market, depending on the desired content parameters.

Toxic metals (cadmium, lead, and mercury) in the tissues of common carp fished from three reservoirs (Pilská, Domaninský, and Matějovský) in the Bohemian-Moravian Highlands were measured in the period from April 2013 to September 2014 and the risk of consuming the fish from these localities was evaluated. During this project 25 fish specimens from each locality were analysed. The concentration of metals in muscle tissue and liver was determined by atomic absorption spectrometry. A variation in the content of heavy metals in fish samples and fish tissues was demonstrated and discussed. Higher concentrations of cadmium in the fish tissue were found in 50 samples of carp liver. Because the fish liver is not commonly consumed, common carp from the Moravian-Moravian Highlands does not pose any health risk for consumers. Concentrations of the other monitored toxic metals in fish tissue were low and were complying with the maximum residue limit in all cases.

The results of nutritional research on fatty acids have led to the recommendation that the level of trans-fatty acids in foods (the products of partial hydrogenation of oils) should be reduced as far as possible. Palm oil and palm kernel oil are readily available and economical sources of solid fat. Formulae using oils to make fats for the main types of food products are reviewed.

In total 228 enterococci strains isolated from food were studied. Enterococcus faecalis, E. faecium, and E. casseliflavus were found to be the dominant strains while E. durans and E. mundtii were present in a smaller extent. Antimicrobial activity determined by double layer technique revealed that 150 (65.7%) strains showed antimicrobial activity against the individual tested pathogenic strains of Listeria monocytogenes, Staphylococcus aureus, and methicilin resistant S. aureus (MRSA). Cell-free neutralised supernatants (CFNS) were prepared from 150 potential bacteriocin producers. Of these 150, CFNS 107 (71.3%) strains were active in the bacteriocin production against one or more pathogenic strains tested. S. aureus and MRSA were found to be more sensitive to the antimicrobial substances than L. monocytogenes. Multiplex PCR for the detection of seven virulence genes in bacteriocin producing strains showed that 47.6% of strains were able to amplify one or more virulence genes. E. faecalis was the most virulent species. The presence of tyrdc gene was seen in all bacteriocin producing strains. None of the strains carried genes encoding the resistance to vancomycin.

The soy sauce samples established a model for its flavour quality evaluation. Initially, 39 types of flavour compounds, organic acids and free amino acids in six different types of soy sauce were identified and determined by HS-SPME GC/MS and HPLC. The model was developed based on the principal component analysis method for assessing and ranking of flavour quality of soy sauce. Using the principal component analysis which simplifies complex information, our correlative evaluation model was established, tested by comparing the traditional sensory evaluation method, providing a new methodology for objective evaluation of the flavour quality of soy sauce.

The antioxidant potential of a leaf extract of Moringa oleifera Lam. (Moringaceae) - LEMO was studied for the stabilisation of butter at refrigeration temperature. LEMO was obtained by extracting the ground and dried leaves with 80% ethanol at room temperature for 48 hours. LEMO was added into butter at three different concentrations, i.e. 400 ppm (T₁), 600 ppm (T₂), and 800 ppm (T₃) and compared with a treatment which was not supplemented with LEMO, i.e. control (T₀). The addition of LEMO at all three levels did not have any effect on butter composition. Free fatty acids, peroxide value and p-anisidine value (AnV) of T₂ after 90 days of storage were 0.10%, 0.71 meq/kg and 14.85 as compared to the control 0.16%, 1.24 meq/kg and 28.85, respectively. Peroxide value of the control and T₂ in Schaal oven test after 5 days in oven was 8.19 and 2.99 meq/kg, respectively. Induction period and overall acceptability score of the control and T₂ were 6.35 h, 8.91 h and 7.6, 7.2, respectively. The results of this study suggest that LEMO at 600 ppm may be used for reasonable storage stability of butter at refrigeration temperate with acceptable sensory characteristics.

Pistachios from Italy and Turkey were stored at different temperatures (10, 20, and 30°C) and the moisture of the pistachios, the free fatty acids (FFA) content, the peroxide value, and triacylglycerols (TGs) composition of the extracted oils were evaluated. The content of FFA decreased during storage at 10°C and increased at 20 and 30°C. No differences between the peroxide values were found during storage at 10°C. A significant increase in the peroxide values was observed after 20 days at 20°C and 5 days at 30°C in both the Italian and Turkish samples. The main TGs found in the pistachio oil of both origins were OLO, OLL, OLP, LLL, LLP, OOP, OLLn, and OOO; these accounted for approximately 85% of the total TGs content. A decrease was observed in the amounts of TGs esterified with polyunsaturated fatty acids, such as LLP, OLP, LLL and OLL, and an increase of the relative amounts of TGs with monounsaturated and saturated fatty acids, such as OOO and OOP, with the increasing storage time and temperatures in both samples.

We evaluated the effect of three different cooking methods on antioxidant content and radical scavenging activity of sweet corn. Both fresh and frozen sweet corn kernels were boiled, microwaved, and stir-fried for 1, 3, and 5 min, respectively, then total phenolic (TP) and total carotenoid (TC) contents were determined by spectrophotometric methods. The free radical scavenging activity of the samples was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The results showed that there was a significant increase in TP (1.2-1.9 times) and TC (1.1 to 1.8 times) content of fresh sweet corn after each cooking session for 1, 3, and 5 min, the same treatment of frozen corn resulted in 47-80% losses of TP and 10 to 39% losses of TC content. The free radical scavenging activity (RSA) exhibited by cooked fresh and frozen sweet corns was found to be different, neither of them was very high, in the range of 70.2-78.6%, and the fresh cooked ones had higher values of RSA.

The aim of the work presented here was the evaluation of the profile of free amino acids as the possible precursors of biogenic amines (BAs) in tomatoes and its changes during tomato ripening. Hygienically significant amounts of BAs can be formed by the action of amino acid decarboxylases provided the tomatoes contain a high enough amount of free amino acids. In view of this, the effect was studied of Lactobacillus plantarum strains 976H and 3626 on the BAs formation in green tomatoes. Homogenates of green tomatoes were adjusted to the model conditions of conservation by the addition of NaCl to the concentration of 1.5% (w/w) and of glucose to the concentration of 2.0% (w/w). The homogenates were subsequently inoculated with the two strains given above. The formation of BAs was monitored for 186 h and compared with that in the control non-inoculated samples. The changes in the BAs content taking place during fermentation were estimated by means of statistical methods. It was found that, during fermentation of green tomatoes with the two strains of Lactobacillus plantarum used, the conditions were not fulfilled that enable BAs formation, i.e. as sufficient amount of free amino acids together with a sufficient production of decarboxylases.

The antioxidant activity of 17 Czech medicinal plants was studied and compared with the antioxidant activity of green tea. The antioxidant activities of water and ethanol extracts of the plants tested were determined by a spectrophotometric method using the stable free radical DPPH (2,2-diphenyl-1-picrylhydrazyl), and further the contents of the compounds with reducing properties in water extracts were determined by flow injection analysis with amperometric detection (using a detection potential +0.7 V). Considerable antioxidant activities were found in the extracts of plants from the Rosaceae family (rosehips and leaves of raspberry, blackberry, and strawberry), the Lamiaceae family (oregano, sweet balm, thyme, dead-nettle, and mint), and flowers of linden and elder.

Peanut skins were isolated from deshelled and dried conventional and high-oleic peanuts. In order to obtain simpler mixtures of phenolics with other components of the respective extract, the samples were extracted with solvents of increasing polarity (hexane, ethyl acetate, and methanol). The amounts of extracts were as follows: methanol > hexane > ethyl acetate, and the contents of phenolic constituents in the extracts: ethyl acetate > methanol > hexane. Ethyl acetate extracts from the skins of both conventional and high-oleic peanuts were about the same. The amount of peanut skin ethyl acetate extract was higher than that of tea leaves, but lower than those of Labiatae plants which were also analysed. Antioxidant activities under the conditions of the Schaal Oven Test in lard and in rapeseed oil were only moderate, lower than in the case of synthetic antioxidants (butylated hydroxytoluene, butylated hydroxyanisole, ascorbyl palmitate). The reducing power, free DPP* radical scavenging, inactivation of hydroxylic, and superoxide free radicals were medium, comparable to those of synthetic antioxidants; these activities also resembled to those in the extracts of conventional and high-oleic peanut skins.

We examine the nutritional effect of selected non-traditional grain samples added into wheat flour. In a form of flour, amaranth, quinoa, lupine, 5 hemp types, 2 teff types and 2 chia types were used for wheat flour substitution on a low and high level. Samples with amaranth and lupine flour showed the best improvement in terms of protein content (in the range between 21.1 and 26.0%). The highest total dietary fibre was found in lupine composites (7.1 and 9.8%). Hemp samples contained a significant amount of minerals in comparison with the control wheat sample (from 1.16% to 1.98%). According to the above-mentioned differences, flour composites containing single tested grains were distinguished by principal component analysis. All examined plant materials could be recommended for wheat flour fortification in terms of nutritional improvement. The addition of non-traditional flours partially changed both the volume and shape of laboratory prepared bread correspondingly to the type and added amount.

Bile salt hydrolase (BSH) activity of intestinal bacteria (including lactobacilli) is one of the indirect ways of decreasing a cholesterol level in human body. Tested Lactobacillus strains were isolated from various sources (faeces of fully breast-fed infants, cow's colostrum, cow's raw milk cheeses, and cow's raw milk) and identified by genotypic and phenotypic methods. All strains, including three commercial probiotic strains and six culture collection strains, were subsequently tested for their BSH activity via two methods - thin layer chromatography (TLC) and plate assay. Among all the 59 Lactobacillus strains, 15 strains were shown to be BSH positive by TLC method and only 8 of them by plate assay. Most of the BSH positive strains (9 strains) were isolated from faeces. Differences between BSH activities for sodium salts of cholyltaurine and cholylglycine were demonstrated. The TLC method was shown to be more sensitive compared to the plate assay for BSH activity determination.

The differentiation of thermotolerant Campylobacter spp. on the species level (C. jejuni, C. coli, C. lari, and C. upsalien-sis) was provided. Identification is based on different banding patterns obtained for individual species during simple multiplex PCR where regions within the 23S rRNA gene are amplified using newly designed specific forward primers.

Several multivariate methods including partial least squares (PLS) regression, principal component regression (PCR) or multiple linear regression (MLR) have been applied to predict wine quality, based on the definition of chemical and phenolic parameters of grapes and wines harvested at different ripening levels. Three different models including grape phenolic maturity parameters (grape), wine phenolic parameters (wine) and a combination of grape and wine phenolic parameters (grape + wine) were analysed for each of the wine sensory attributes. The grape parameter model has been presented as the best test to predict wine quality based on sensory scores. On the other hand, wine models showed lower accuracy. The combination of grape and wine parameters presented intermediate results showing sometimes good predictability. Moreover, PLS and PCR appeared as more accurate multivariate methods compared to MLR. Although MLR showed higher correlation coefficients, lower RPD values were observed, displaying thus its lower prediction accuracy. Multivariate calibration statistics appeared as a promising tool to predict wine sensory quality in an easy and inexpensive way.

The water of the breads was replaced with phenolic aqueous extracts from chicory, cabbage, celery, fennel, olive leaf, or grape marc wastes obtained through microwave-assisted extraction. The highest phenolic concentrations were found in the grape marc and in the bread enriched with it. The highest antioxidant activity values were measured in the crust of bread produced with the grape marc extract and in the crumb of bread with olive leaf extract. Generally, the replacement of water caused significant decreases of the specific volume, the shift of the crumb colour towards redder and yellower tones, and modification of gustatory and tactile attributes.

Recycled paper is commonly used in food packaging industry, especially for disposable products. The material coming into direct contact with food products must not represent a source of contamination for food in accordance with the Framework Regulation (EC) No. 1935/2004 containing the general requirements on all food contact materials. In the present study, the microbial purity of 31 paper-based materials with different contents of recycled matter (0-100%) was evaluated using a standard method based on the disintegration of paper. The results of the present study indicate the existing relation between the use of recycled fibers and the content of microorganisms. The increased amount of recycled fibers significantly increased the amount of bacteria in the paper samples. The highest content of microorganisms was observed in the case of paper with the highest recycled fiber content. Total counts of bacteria ranged from 5.0 × 10¹ to 1.2 × 10⁵ CFU/g. Moulds were detected only in three paper samples. As the microorganisms present in food packaging may penetrate into foodstuffs (particularly those with high contents of water or fat) and have an adverse effect on end-consumers' health, microbial criteria for food packaging should be included into the EU legislation.

The "Breme" onion is a red-skinned cultivar growing in the northwest Italy. To date, its nutrient composition has not been described. In this study, we quantified the contents of quercetin (Q) and its glycosides and we studied their stability in the dependence on the local home-storage methods storage at 4°C and freezing. Quercetin-3,4'-O-diglycoside (3,4'-Qdg) was the most abundant form, followed by quercetin-4'-O-diglycoside (4'-Qmg ) and Q. We observed the reduction in the contents of all the analysed flavonols after storage at 4°C and after storage in frozen state. No changes have been observed in the ratio Q/3,4'-Qdg + 4'-Qmg, as well as in 3,4'-Qdg /4'-Qmg between the fresh, stored at 4°C, and frozen onions. This could suggest an overall condition of instability, not the activation of a selective deglycosylation pathway. In conclusion, our study shows that the "Breme" onion is mainly rich in 3,4'-Qdg and that home-storage methods do not preserve the stability of some important health-promoting molecules.