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Results 331 to 360 of 586:

Effect of cow energy status on the hypercholesterolaemic fatty acid proportion in raw milkOriginal Paper

Jaromír DUCHÁČEK, Luděk STÁDNÍK, Martin PTÁČEK, Jan BERAN, Monika OKROUHLÁ, Jaroslav ČÍTEK, Roman STUPKA

Czech J. Food Sci., 2014, 32(3):273-279 | DOI: 10.17221/360/2013-CJFS

We evaluated the proportion of fatty acid groups, with an emphasis on hypercholesterolaemic fatty acids, in the milk of 25 Holstein cows during the 1st period of lactation in relation to their negative energy balance (NEB). Sampling of each cow's milk started on the 7th day after calving. Milk samples (n = 425) were collected at 7-day periods during the first 17 weeks of lactation. The proportion (%) of saturated (SFA), hypercholesterolaemic (HCFA), volatile (VFA), unsaturated (UFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids in the milk fat was determined. Body condition score and fat to protein ratio in milk were applied for precise determination of the NEB breakpoint during the observed period. The effects of parity, NEB, regression on lactation week and fat to protein ratio were evaluated using SAS 9.3. Milk contained a lower proportion of SFA as well as equally higher UFA (± 2.13%; P < 0.01) during the NEB period. The overcoming of NEB caused an increase in SFA, however, and simultaneously a significant decline in total HCFA (-1.86%; P < 0.01) as well as main MUFA (-1.81%, P < 0.05). The results document the necessity of increasing Holstein cow robustness to meet the production conditions in dairy farms in relation to the requirement of higher nutrient quality as well as the potential health benefits of cow's raw milk for consumers.

Advances in the Understanding of the Chemical Reactions Responsible for Bread Flavour Quality

P. Poinot, G. Arvisenet, J. Grua-Priol, C. Fillonneau, S. Mezaize, M. De Lamballerie, A. Le-Bail, C. Prost

Czech J. Food Sci., 2009, 27(10):S54-S57 | DOI: 10.17221/1074-CJFS

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.

Evaluation of the morphologic method for the detection of animal and herbal content in minced meatFood Technology and Economy, Engineering and Physical Properties

Javad Sadeghinezhad, Bahador Hajimohammadi, Farkhondeh Izadi, Fatemeh Yarmahmoudi, Rocco Latorre

Czech J. Food Sci., 2015, 33(6):564-569 | DOI: 10.17221/167/2015-CJFS

The quantitative and qualitative accuracy of the routine histological method for the determination of unauthorised animal and herbal content in minced meat was to evaluated. Laboratory adulterated minced beef meat; each containing 5, 10, 15 and 20% of soya and chicken gizzard was prepared. Then each sample was divided into three parts and four paraffin embedded blocks were prepared from each part. The sections were stained using haematoxylin and eosin, toluidine blue and Masson's trichrome. The histological examination revealed the soya and gizzard tissues clearly in all the samples. The histometrical analysis showed that there was no significant difference between the estimated percentages of both additive tissues and the real related percentages. Overall, neither was there any significant difference between the data of the three parts of each sample and the real percentages. The findings of the present research suggest the histological technique as an effective method for qualitative and quantitative evaluations of minced meat.

The effects of butylated hydroxyanisole, ascorbic acid, and α-tocopherol on some quality characteristics of mechanically deboned chicken patty during freeze storage

Ozgul Ozer, Cemalettin Sariçoban

Czech J. Food Sci., 2010, 28(2):150-160 | DOI: 10.17221/160/2009-CJFS

In this study, the effects were evaluated of butylated hydroxyanisole (BHA), ascorbic acid (AA) and α-tocopherol (TO) on the stability of raw mechanically deboned chicken patties stored at -20°C for 6 months. pH, thiobarbituric acid reactive substance (TBARS), haem iron (mg/kg), metmyoglobin formation (%) and colour (L*, a*, b*, C* and h values) of patties were measured for 0, 2, 4, and 6 months of storage time. pH values were found to be the highest in the initial storage period. TBARS values were observed to range between 0.33 and 2.40 mg malondialdehyde/kg of sample and the L*, a*, and b* values of the patty samples during the storage period were found to range between 38.14 and 49.52, 9.01 and 20.87, and 7.28 and 14.62, respectively. The haem iron and metmyoglobin contents were found to range between 8.39 and 10.87 mg/kg and 19.26% and 45.91%, respectively. As a result, it is suggested that L-ascorbic acid and α-tocopherol can be added into chicken patty samples in view of the storage quality parameters mentioned above.

Change of selected antioxidant parameters of red wines during maturationFood Technology and Economy, Engineering and Physical Properties

Ján Mezey, Peter Czako, Ivana Mezeyová, Daniel Bajčan, Radoslav Kobolka

Czech J. Food Sci., 2016, 34(4):356-361 | DOI: 10.17221/517/2015-CJFS

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.

Purification and characterisation of the bacteriocin produced by Lactobacillus plantarum, isolated from Chinese pickleOriginal Paper

Fang Zhou, Hongfei Zhao, Fengling Bai, Piotr Dziugan, Yuen Liu, Bolin Zhang

Czech J. Food Sci., 2014, 32(5):430-436 | DOI: 10.17221/270/2013-CJFS

119 strains of lactic acid bacteria from Chinese pickle were tested for production of antimicrobial compounds (bacteriocins). Among them, strain C8 showed strongly antibacterial activity against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8739. Strain C8 was identified as Lactobacillus plantarum based on phenotypical, physiological tests and 16S rDNA identification. The antibacterial substance produced by strain C8 was sensitive to protease but not affected by lipase and amylase and designated as bacteriocin C8. Bacteriocin was purified by salting-out, dialysis and Sephadex G50 column chromatography. Based on SDS-PAGE, bacteriocin C8 was 16.5 kDa in size, which was different from that of other bacteriocins and it might be a novel bacteriocin. Bacteriocin C8 showed a wide range of antimicrobial activity especially as it inhibited some Gram-negative bacteria. This bacteriocin was heat resistant (20 min at 121°C) and stable in the pH range of 3 to 6.

Antibacterial and antifungal effects of alcoholic extracts of 41 medicinal plants growing in Turkey

Ömer Ertürk

Czech J. Food Sci., 2010, 28(1):53-60 | DOI: 10.17221/144/2008-CJFS

The antibacterial and antifungal activities of crude ethanolic extracts of 41 traditional medicinal plant species belonging to 26 families were tested against four bacteria and two fungi: Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. Of the 41 plants tested, 39 showed antimicrobial activity against one or more species of microorganisms. While the crude extracts from Nigellea arvensis did not show antimicrobial activity against the test microorganisms, Pistasia lentiscus showed only antifungal activity against A. niger. The most active antimicrobial plants were Cuminum cyminum, Jasminium officinale, Thymus capitatus, Viscum album, Tanecetum sorbifolium, Pimpinella anisum, Galega officinalis, Liguidamber orientalis, Rhus coriaria, Alnus glutinosa, Pimental officinalis, Achillea coarctata, and Cameli sinensis.

Effect of storage temperature on the quality of dry fermented sausage Poličan

Josef Kameník, Alena Saláková, Gabriela Bořilová, Zdeněk Pavlík, Eva Standarová, Ladislav Steinhauser

Czech J. Food Sci., 2012, 30(4):293-301 | DOI: 10.17221/284/2011-CJFS

The influence of different storage temperatures (5°C and 15°C) on the quality of vacuum-packed dry fermented sausage Poličan was determined. The salami mixture, finished salamis (the maturing period of 30 days), and salamis stored for 30, 60, 90, and 120 days were analysed. The analyses performed (physical/chemical, sensory, microbiological) found no differences in sensory properties or basic physical/chemical and microbiological parameters in the products after storage under different temperature conditions for 120 days. When stored at 15°C, the total content of biogenic amines in samples was higher than that for samples stored at 5°C with statistical differences P ≤ 0.05. If the principles of good manufacturing practice are observed at all phases of the technological process, the storage temperature of 15°C does not represent a risk as the consequent concentration of biogenic amines and polyamines remains extremely low.

Diastase number changes during thermaland microwave processing of honey

Stanisław Kowalski, Marcin Lukasiewicz, Szczepan Bednarz, Marzena Panuś

Czech J. Food Sci., 2012, 30(1):21-26 | DOI: 10.17221/123/2010-CJFS

The presented paper covers the preliminary studies on microwave inactivation of honey enzymes described as diastase number (DN). All the investigations were done on commercially available honey from Polish local market. Microwave processes were compared to the conventional ones. In the case of conventional conditions, the constant rate of diastase enzyme inactivation was estimated using the first order kinetics. In the case of microwave heated samples, it was impossible to establish the rate constant; however, the investigation proved the suitability of such kind of processing for short-term thermal treatment of honey.

Antioxidant activities of two novel synthetic methylbenzenediol derivativesOriginal Paper

Yan Huang, Zhiwu Jiang, Xianyan Liao, Jianping Hou, Xinchu Weng

Czech J. Food Sci., 2014, 32(4):348-353 | DOI: 10.17221/283/2013-CJFS

2-(tert-Butyl)-5-methylbenzene-1,4-diol and 3-(tert-butyl)-5-methylbenzene-1,2-diol were synthesised by Friedel-Craft reaction of 2-methylbenzene-1,4-diol and 4-methylbenzene-1,2-diol, respectively, with tertiary butanol providing reasonable yields. The antioxidant activities of these two products, mother compounds and 2-(tert-butyl)benzene-1,4-diol were investigated and compared by means of 2,2-diphenyl-1-picrylhydrazyl radical and Rancim at test; 3-(tert-butyl)-5-methylbenzene-1,2-diol is the most potent antioxidant tested by using Rancimat test experiment. The 2,2-diphenyl-1-picrylhydrazyl radical scavenging abilities of 2-methylbenzene-1,4-diol, 4-methylbenzene-1,2-diol and 2-(tert-butyl)benzene-1,4-diol are almost equal and more than twice as strong as 2-(tert-butyl)-5-methylbenzene-1,4-diol and 3-(tert-butyl)-5-methylbenzene-1,2-diol. The antioxidant activities of the five compounds evaluated by Rancimat test mainly depend on their steric synergist effects between the two phenolic hydroxyl groups in their molecules. The antioxidant activities of the five compounds mainly depend on how many 2,2-diphenyl-1-picrylhydrazyl radicals can be scavenged by one mole of them in 2,2-diphenyl-1-picrylhydrazyl test. One mole of 2-methylbenzene-1,4-diol, 4-methylbenzene-1,2-diol and 2-(tert-butyl)benzene-1,4-diol can scavenge four moles of 2,2-diphenyl-1-picrylhydrazyl radicals, but one mole of 2-(tert-butyl)-5-methylbenzene-1,4-diol or 3-(tert-butyl)-5-methylbenzene-1,2-diol can only scavenge two mole 2,2-diphenyl-1-picrylhydrazyl radicals because 2,2-diphenyl-1-picrylhydrazyl radicals are very bulky.

Nourishing and health benefits of coenzyme Q10

Martina BOREKOVÁ, Jarmila HOJEROVÁ, Vasiľ KOPRDA, Katarína BAUEROVÁ

Czech J. Food Sci., 2008, 26(4):229-241 | DOI: 10.17221/1122-CJFS

Coenzyme Q10 is an important mitochondrial redox component and endogenously produced lipid-soluble antioxidant of the human organism. It plays a crucial role in the generation of cellular energy, enhances the immune system, and acts as a free radical scavenger. Ageing, poor eating habits, stress, and infection - they all affect the organism's ability to provide adequate amounts of CoQ10. After the age of about 35, the organism begins to lose the ability to synthesise CoQ10 from food and its deficiency develops. Many researches suggest that using CoQ10 supplements alone or in combination with other nutritional supplements may help maintain health of elderly people or treat some of the health problems or diseases. Due to these functions, CoQ10 finds its application in different commercial branches such as food, cosmetic, or pharmaceutical industries. This review article gives a survey of the history, chemical and physical properties, biochemistry and antioxidant activity of CoQ10 in the human organism. It discusses levels of CoQ10 in the organisms of healthy people, stressed people, and patients with various diseases. This paper shows the distribution and contents of two ubiquinones in foods, especially in several kinds of grapes, the benefits of CoQ10 as nutritional and topical supplements and its therapeutic applications in various diseases.

Trans-free fats with the products of the oil palm - a selective review

Kurt G. Berger

Czech J. Food Sci., 2007, 25(4):174-181 | DOI: 10.17221/688-CJFS

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.

Preparation of high Fischer ratio oligopeptide by proteolysis of corn gluten meal

Ying MA, Li LIN, Da-Wen SUN

Czech J. Food Sci., 2008, 26(1):38-47 | DOI: 10.17221/1138-CJFS

A method to obtain an oligopeptide with high Fischer ratio is described. Corn gluten meal (CGM) was hydrolysed with Alcalase 2.4L using a two-step hydrolysis. In the first-step hydrolysis, the enzyme reaction conditions for hydrolysing CGM were optimised by using the orthogonal experimental design, while pH = 8.0, temperature = 55°C, enzyme to substrate ratio (3:97, w/w), and the substrate concentration = 5% were identified as the optimum conditions, under which up to 11.62% degree of hydrolysis (DH) could be obtained. The hydrolysate was then fractionated by ultrafiltration using a membrane with the molecular cutoff of over 10 kD at 20 kPa. For the second-step hydrolysis, the filtrate was adjusted to pH 6.0, then papain was added at 50°C and the mixture was maintained for 3 hours. The hydrolysate was obtained after inactivating papain and centrifuging. Then the salt (mainly NaCl) in the hydrolysate was removed with an ion exchange resin at the speed of 8 times bed volume per hour, and aromatic amino acids were removed through absorption by active carbon. By using Sephadex G-25 gel filtration chromatography, a peptide mixture with low molecular weights between 1000 and 1300 was obtained. Finally, tests on amino acid composition and free amino acid concentration of oligopeptide solution showed that the oligopeptide had a high Fischer ratio of 34.71 and the yield of 11.59%.

New model for flavour quality evaluation of soy sauceOriginal Paper

Jie Feng, Xiao-Bei Zhan, Zhi-Yong Zheng, Dong Wang, Li-Min Zhang, Chi-Chung Lin

Czech J. Food Sci., 2013, 31(3):292-305 | DOI: 10.17221/524/2011-CJFS

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.

Prediction of the average surface heat transfer coefficient for model foodstuffs in a vertical display cabinet

Karel Hoke, Aleš Landfeld, Jiří Severa, Karel Kýhos, Rudolf Žitný, Milan Houška

Czech J. Food Sci., 2008, 26(3):199-210 | DOI: 10.17221/1590-CJFS

Calculations of transient temperatures of food products after they are transferred from a warm environment into a display cabinet, require data on the surface heat transfer coefficient (SHTC). There is no forced air flow in an ordinary display cabinet, so the energy transfer is achieved mainly by free convection, conduction to a supporting plate, and radiation. Theoretical analysis of the heat transfer to a cylindrical sample demonstrates the relative influences of these mechanisms. This work investigates the apparent surface transfer coefficients with metal models. Heated models were placed individually (bare) in containers with and without lids. Each model was surrounded by identical containers filled with water. These were initially at the same temperature as the model or at the mean cabinet temperature. There were one, two, or three layers of these water containers. From the measured time-temperature histories of the model and the air surrounding the model, the SHTCs were calculated as functions of time and transformed into the dependencies between SHTC and temperature difference. The highest SHTCs were observed when the model was placed directly on the metal shelf of the display cabinet. The models surrounded by cool water containers showed lower SHTC values. The lowest SHTC values were found with the models placed in the middle of three layers of warm water containers. Placing the model on an insulating base leads to a lower SHTC. This effect confirms that the heat conduction through the substrate increases the heat transfer from the model and thus increases the average value of the apparent SHTC.

Perspectives and applications of immobilised β-galactosidase in food industry - a review

Zuzana Grosová, Michal Rosenberg, Martin Rebroš

Czech J. Food Sci., 2008, 26(1):1-14 | DOI: 10.17221/1134-CJFS

β-Galactosidase is an important industrial enzyme in the hydrolysis of milk and whey lactose. The enzymatic hydrolysis of lactose allows to avoid health and environmental problems posed by this disaccharide. In addition, this enzyme catalyses the formation of galacto-oligosaccharides, which are prebiotic additives for the so-called "healthy foods". β-Galactosidase is one of the relatively few enzymes that have been used in large-scale processes in both free and immobilised forms. This article presents a review of recent trends in immobilisation of β-galactosidase and their application in food industry.

Antioxidant potential of Moringa oleifera leaf extract for the stabilisation of butter at refrigeration temperatureOriginal Paper

Muhammad NADEEM, Muhammad ABDULLAH, Imtiaz HUSSAIN, Saima INAYAT, Arshad JAVID, Yasir ZAHOOR

Czech J. Food Sci., 2013, 31(4):332-339 | DOI: 10.17221/366/2012-CJFS

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.

Functional bioactive compounds and biological activities of Spirulina platensis lipids

Mohamed Fawzy Ramadan, Mohsen Mohamed Selim Asker, Zeinab K. Ibrahim

Czech J. Food Sci., 2008, 26(3):211-222 | DOI: 10.17221/2567-CJFS

The compositions and concentrations of lipid classes, fatty acids, tocopherols were determined in the lipids from blue-green microalga Spirulina platensis. Total lipids (TL) recovered using chloroform: methanol (2:1, v/v) were found to be 163.5 g/kg (on dry weight basis). The level of neutral lipids was the highest, followed by glycolipids and phospholipids, respectively. Among TL and lipid classes, palmitic, γ-linolenic and linoleic acids were the dominating fatty acids. Compared to the neutral lipids, the polar fractions were generally characterised by higher percentages of saturated fatty acids. The recovered lipids were characterised by high percentage of tocopherols, wherein γ-tocopherol constitutes about 73% of total tocopherols present, the rest being γ-tocopherol. Spirulina platensis lipids exhibited a strong radical scavenging activity towards stable DPPH free radicals, whereas 27% of DPPH radicals were quenched after 2 h incubation. TL and lipid classes inhibited the growth of different microorganisms except gram-negative bacteria. At high concentrations, the tested lipids appeared more effective against A. niger (28.3 ± 1.53 mm). The information obtained in the present investigation is useful for lipid characterisation and further chemical and nutritional investigations of Spirulina platensis.

Effect of postharvest storage temperatures on the quality parameters of pistachio nutsOriginal Paper

Elena ARENA, Gabriele BALLISTRERI, Biagio FALLICO

Czech J. Food Sci., 2013, 31(5):467-473 | DOI: 10.17221/69/2013-CJFS

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.

Formation of carboxylic acids during degradation of monosaccharides

Ondřej Novotný, Karel Cejpek, Jan Velíšek

Czech J. Food Sci., 2008, 26(2):113-131 | DOI: 10.17221/2465-CJFS

The formation of low molecular carboxylic and hydroxycarboxylic acids as well as sugar and deoxysugar acids from monosaccharides (D-glucose, D-fructose, D-arabinose, DL-glyceraldehyde, and 1,3-dihydroxyacetone) was studied in three different model systems: aqueous and alkaline solutions of potassium peroxodisulfate (K2S2O8), and sodium hydroxide solution. In total, 3 low molecular carboxylic acids (formic, acetic and propionic), 24 hydroxycarboxylic acids, and 12 corresponding lactones were identified and quantified by GC/MS. Formic, acetic, and propionic acids were isolated by extraction with diethyl ether and directly analysed by GC/MS; hydroxycarboxylic acids and their lactones were monitored as their trimethylsilylated derivatives using the same method. Formic, acetic, L-lactic, glycollic, DL-2,4-dihydroxybutanoic acids and aldonic acids derived from the parent sugars were the most abundant compounds in all model systems. Within the models investigated, the yield of carboxylic acids and hydroxycarboxylic acids (together with their lactones) ranged between 9.3-22.2% (n/n) and between 3.6-116.9% (n/n), respectively. The amount of acids was significantly lower in aqueous solutions of K2S2O8 than in the alkaline solutions. The data obtained indicate that lower carboxylic acids are formed by both subsequent reactions (oxidation and/or intramolecular Cannizzaro reaction) of the sugar fragmentation products and direct decomposition of some intermediates such as uloses or hydroperoxides derived from the parent sugars. The acids possessing the original sugar skeleton are formed as a result of sugar oxidation or benzilic acid type rearrangement of deoxyuloses. Lower acids may also be formed by a recombination of free radicals.

Effect of cooking methods on total phenolic and carotenoid amounts and DPPH radical scavenging activity of fresh and frozen sweet corn (Zea mays) kernelsOriginal Paper

Jiangfeng SONG, Chunquan LIU, Dajing LI, Lili MENG

Czech J. Food Sci., 2013, 31(6):607-612 | DOI: 10.17221/396/2012-CJFS

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.

Relation between free amino acids and the biogenic amines contents in green tomatoes inoculated with Lactobacillus plantarum

M. Veselá, M. Drdák, S. Standara

Czech J. Food Sci., 2003, 21(2):51-58 | DOI: 10.17221/3477-CJFS

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.

Antioxidant activity and sensory changes of strawberry tree fruits during cold storage and shelf lifeFood Technology and Economy, Engineering and Physical Properties

Costantino Fadda, Paolo Antonio Maria Fenu, Giampaolo Usai, Alessandra Del Caro, Yolanda Matia Diez, Anna Maria Sanguinetti, Antonio Piga

Czech J. Food Sci., 2015, 33(6):531-536 | DOI: 10.17221/171/2015-CJFS

The influence of storage time on a range of quality parameters, in vitro antioxidant activity, and the sensory acceptability of fully ripe strawberry tree fruits packaged into polypropylene trays under plastic film was assessed. Fruits were stored at 0°C for 6, 12 or 18 days and then transferred to shelf life at 20°C for 2 days. The parameters most influenced by cold storage and shelf life were firmness, colour, and antioxidant activity. Firmness decreased significantly during storage and colour parameters showed a decrease in saturation. Significant increases in polyphenols and anthocyanins were registered during storage, with a resulting increase in total antioxidant activity. The sensory analysis demonstrated that fruits maintain an acceptable quality level for up to 1 day under shelf life conditions following 18 days of cold storage.

The "Breme" red onion: effects of home-storage methods on quercetin and quercetin-glycoside contentsFood Chemistry and Safety

Elena DOZIO, Alessandra BARASSI, Alessandro RAVELLI, Ilaria ANGELI, Franco LODI, Gian Vico MELZI d'ERIL, Massimiliano M. CORSI ROMANELLI

Czech J. Food Sci., 2015, 33(5):405-409 | DOI: 10.17221/622/2014-CJFS

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.

Different peach cultivars and their suitability for minimal processingOriginal Paper

Maria Del Carmen Fuentes-Pérez, Sergio Nogales-Delgado, Maria Concepción Ayuso, Diego Bohoyo-Gil

Czech J. Food Sci., 2014, 32(5):413-421 | DOI: 10.17221/320/2013-CJFS

Consumption of minimally processed fruits has been increased lately mainly due to their fresh-like quality characteristics. One of the major alterations that limit the shelf-life of these products is browning caused by polyphenol oxidase (PPO) activity on phenolic compounds. Six yellow-flesh peach cultivars, Spring Lady, Royal Glory, Ruby Rich, Summer Rich, Ryan Sun, and O'Henry, were selected. Peaches were hygienised and then samples were processed in a clean room. Slices were washed in cold tap water, dried, packaged in modified atmosphere, and stored at 4°C during 9 days; physicochemical and other quality parameters were studied. Principal Component Analysis (PCA) and correlation study were carried out in order to evaluate the relation between variables and cultivars. In conclusion, Spring Lady, Royal Glory, and Ruby Rich cultivars were the cultivars that offered the most suitable fruits for fresh-cut processing, mainly due to their low BP and PPO activity.

Species differentiation of thermotolerant Campylobacters based on distinctive banding patterns obtained by multiplex PCRFood Microbiology and Safety

Lucie VONDRÁKOVÁ, Sabina PURKRTOVÁ, Jarmila PAZLAROVÁ, Kateřina DEMNEROVÁ

Czech J. Food Sci., 2015, 33(1):27-31 | DOI: 10.17221/267/2014-CJFS

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.

Microbiological quality of ice cream after HACCP implementation: a factory case study

Emmanuel N. Kokkinakis, Georgios A. Fragkiadakis, Souzana H. Ioakeimidi, Ilias B. Giankoulof, Aikaterini N. Kokkinaki

Czech J. Food Sci., 2008, 26(5):383-391 | DOI: 10.17221/1126-CJFS

The microbiological quality of the final product and the safety of the production procedures were screened in an ice cream factory, after implementation of a Hazard Analysis Critical Control Points (HACCP) system. We analysed 30 vanilla (IC1), 30 strawberry (IC2), and 30 chocolate flavoured (IC3) samples of ice cream; 30 of water; 90 of personnel's hands flora; 150 of plastic ice cream containers flora; 50 of sanitised equipment-surfaces flora. After HACCP introduction, Staphylococcus aureus was not further detectable in ice cream and Escherichia coli was mostly less than 10 CFU/g, while the spoilage markers (total coliforms - TC, aerobic plate counts - APC) in ice cream and the environment were reduced by 20-35%. Mean log CFU/g, for IC1: TC from 2.20 reduced to 1.57, APC from 4.58 reduced to 3.62. For IC2: TC from 2.29 reduced to 1.65, APC from 4.61 reduced to 3.49. For IC3: TC from 2.67 reduced to 1.76, APC from 5.08 reduced to 3.81.

Short overview of food consumption databasesReview

Viktória SZŰCS, Erzsébet SZABÓ, Diána BÁNÁTI

Czech J. Food Sci., 2013, 31(6):541-546 | DOI: 10.17221/160/2013-CJFS

The utilisation of food consumption databases is widespread and involves for example, the risk assessment, understanding of consumers' food consumption trends, health education, and planning of prevention projects. Harmonisation of national consumption data for international comparison is an important and challenging work. First attempts started in the 70's and have been continuing up to now. The present study gives an overview of the collection methods, types and utilisation of food consumption data, as well of the most important phases of the international harmonisation work. As this study shows, it is crucial to harmonise the surveys parameters like the time of the data collection, method, number of participants, and number of the analysed days for an internationally comparable consumption database. From this point of view, the efforts of the EU menu project are promising.

Optimised procedure to analyse Maillard reaction-associated fluorescence in cereal-based products

Cristina Delgado-Andrade, José A. Rufián-Henares, Francisco J. Morales

Czech J. Food Sci., 2008, 26(5):339-346 | DOI: 10.17221/39/2008-CJFS

Fluorescent Maillard compounds measurement provides more specific information on the extent of the Maillard reaction than other unspecific tools to monitor the reaction, and is suitable, as the first approach, to assess the nutritional quality of foods as related to protein damage. This work presents an optimised laboratory procedure for the measurement of total fluorescent intermediate compounds (FIC) associated with Maillard reaction, described and evaluated in a cereal-based product. Total FIC are evaluated using increased pronase E concentrations and different incubation times for the enzymatic hydrolysis, as well as three different sample clean-up steps after the enzymatic digestion. The effects of basic/acid media are considered for the stability of the fluorescent compounds. The standardised procedure is finally applied to breakfast cereals as a model of cereal-based products, analysing the correlation between total FIC production and fibre and protein contents. It is demonstrated that fluorescent compounds are mainly linked to the protein backbone in ready-to-eat breakfast cereals. Fluorescence measurement is presented as an inexpensive, rapid and accurate procedure to study the extent of Maillard reaction in breakfast cereals.

Jan Velíšek, Karel Cejpek - Biosynthesis of Food Components

J. Davídek

Czech J. Food Sci., 2008, 26(5):392 | DOI: 10.17221/178/2008-CJFS

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