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Results 241 to 270 of 583:

The effect of freezing storage on physical and chemical properties of wild boar meatFood Technology and Economy, Engineering and Physical Properties

Marian GIL, Paulina DUMA-KOCAN, Renata STANISŁAWCZYK, Mariusz RUDY

Czech J. Food Sci., 2018, 36(6):487-493 | DOI: 10.17221/62/2018-CJFS

The colour, chemical composition, texture parameters, hydration properties and fatty acids profile of fresh wild boar meat and meat after 2 months of freezing were compared. The research material was the M. longissimus dorsi muscle cut out of wild boar carcasses (Sus crofa). Analyses of physical and chemical properties of samples taken from 16 boars were performed. Samples were packed and frozen to -18°C and stored under such conditions for a period of two months. Freezing storage significantly increased the elasticity value and the colour of the meat as indicated by the decrease in L* and b* values. In frozen meat there slightly increased thermal drip and forced drip. The changes in the fatty acid profile under the effect of freezing were found more often in fat from muscle M. longissimus dorsi than in back fat of wild boar. In conclusion, it should be noted that freezing storage in a short time does not affect negatively the quality of frozen meat.

Effect of modified atmosphere packaging on the shelf life of chilled Ccommon carp (Cyprinus carpio) steaks: chemical and sensory attributesFood Analysis, Food Quality and Nutrition

Jelena BABIĆ MILIJAŠEVIĆ, Milan MILIJAŠEVIĆ, Danijela VRANIĆ, Jasna ĐINOVIĆ STOJANOVIĆ, Slobodan LILIĆ, Vladimir KORIĆANAC

Czech J. Food Sci., 2018, 36(3):221-226 | DOI: 10.17221/195/2017-CJFS

The effect of modified atmosphere packaging (MAP 1 - 80% O2 + 20% CO2 and MAP 2 - 90% CO2 + 10% N2) on selected chemical and sensory parameters of common carp steaks stored at 3 ± 0.5°C, and determination of the shelf life of the products was studied in this research. Samples were analysed on day 1, 3, 5, 7, 9, 11, 13, 15, and 17. An increase in TVB-N values in carp steaks followed the order: MAP 2 < control < MAP 1. From day 9 of storage FFA concentrations were higher (P < 0.01) in MAP 2 samples compared to control and MAP 1 samples. The presence of oxygen (MAP 1 and control) resulted in an increase in TBA values in comparison with samples packaged in the absence of oxygen. According to sensory evaluation, it was concluded that carp steaks packaged in modified atmosphere with 80% O2 + 20% CO2 remained acceptable up to 15 days of storage, whereas samples packaged under 90% CO2 + 10% N2 as well as samples kept on flaked ice remained unchanged until the end of the experiment.

Effect of taxifolin on physicochemical and microbiological parameters of dry-cured pork sausageFood Analysis, Food Quality and Nutrition

Anita Rokaityte, Gintare Zaborskiene, Sonata Gustiene, Raimondas Raudonis, Valdimaras Janulis, Galina Garmiene, Arturas Stimbirys

Czech J. Food Sci., 2019, 37(5):366-373 | DOI: 10.17221/57/2018-CJFS

The effect of taxifolin (TXF) with starter cultures (SC), such as Leuconostoc carnosum, or a mixture of strains Pediococcus pentosaceus and Staphylococcus xylosus, on the TXF stability was evaluated. UPLC analysis demonstrated that after 181 days of storage total TXF content was the highest in samples with TXF and L. carnosum (60%), compared to the 1st day of storage. The sausages with TXF and the mixture of P. pentosaceus and S. xylosus (56%) followed next. The samples treated only with TXF retained 40% of TXF, compared to the 1st day of storage. TXF had no significant effect on the growth of lactic acid bacteria. The accumulation of biogenic amines (BA), including histamine and putrescine, was more effectively reduced in sausages inoculated with the TXF plus P. pentosaceus and S. xylosus mixture. Using this mixture, the rate of lipolysis and processes of lipid oxidation were effectively slowed down. Fatty acid (FA) composition was stable in all cases.

Medicinal plants of the family Lamiaceae as functional foods - a reviewReview

Klaudija Carović-Stanko, Marko Petek, Martina Grdiša, Jasna Pintar, Dalibor Bedeković, Mirjana Herak Ćustić, Zlatko Satovic

Czech J. Food Sci., 2016, 34(5):377-390 | DOI: 10.17221/504/2015-CJFS

Historically, species of the family Lamiaceae have enjoyed a rich tradition of use for flavouring, food preservation, and medicinal purposes, due to both their curative and their preventive properties. It is well known that each species has a special, complex mixture of bioactive compounds in which each component contributes to its overall bioactivity. Their value lays in the production of a wide range of secondary metabolites with potent antibacterial, antioxidant, anti-inflammatory, antimicrobial, antiviral, and anticancer activities. This review focuses on the Lamiaceae species and their secondary metabolites encompassing a wide array of beneficial functions and their applicability as sources of functional foods. It could help in addressing specific consumer needs as healthy diet is a part of the lifestyle that maintains or improves overall health.

Relationship between somatic cell count and milk casein level obtained by two different methodsFood Technology and Economy, Engineering and Physical Properties

Danuta Beliavska-Aleksiejuné, Rolandas Stankevičius

Czech J. Food Sci., 2016, 34(1):47-51 | DOI: 10.17221/254/2015-CJFS

The purpose of the present work was to investigate the impact of somatic cell count (SCC) on the content of milk casein and to compare the sensitivity of different methods for the determination of the casein level in milk. Two different methods were employed in order to determine the casein level: routine method - infrared spectrophotometry and reference method - Kjeldahl. Data array of 26, 169 milk samples of the livestock control was used to analyse milk casein variation by SCC limits. Mean casein values (investigated by the routine method) varied from 2.47% to 2.8% (2.65 ± 0.09) and casein number (in % on crude protein basis) - CN% varied from 79.5% to 81.1%. The present analysis showed that the relation between SCC and casein content obtained by the routine method correlated significantly (Pearson correlation rp = 0.644, P < 0.05, R2 = 0.414, Spearman correlation rs = 0.786, P < 0.05). Evaluated results obtained by the least squares method, and linear approximation of variation indicators presented a noticeable decline in casein percentage - 0.27%, when SCC increased by 80 × 103/ml, but only when the studies were done by the reference method.

Evidence for wheat, rye, and barley presence in gluten free foods by PCR method - comparison with ELISA method

Eva Mašková, Ivana Paulíčková, Jana Rysová, Dana Gabrovská

Czech J. Food Sci., 2011, 29(1):45-50 | DOI: 10.17221/171/2010-CJFS

A method of the evidence for the presence of wheat, rye, and barley in gluten free foods, based on the polymerase chain reaction (PCR), was validated. DNA was isolated from foods by chaotropic solid phase extraction. The PCR method applied was focused on the intron of the chloroplast gene trnL and utilised primers WBR11 and WBR13. Electrophoresed wheat and rye DNAs were characterised by a 201 bp fragment, barley DNA by a 196 bp fragment. The validated PCR method was applied to the selection of 18 gluten free foods, previously found by ELISA method to contain 1 mg or more of gliadin per 100 g food. The presence of wheat was confirmed by PCR method in all foods analysed. The comparison with the results obtained by ELISA method reliably verified the detection limit of PCR method, i.e., 0.02% wheat.

ELISA for free S-equol in human urine

Lucie Sosvorová, Petra Lanková, Marie Bičíková, Elena A. Prokudina, Nawaf Al Maharik, Oldřich Lapčík

Czech J. Food Sci., 2011, 29(1):57-64 | DOI: 10.17221/130/2010-CJFS

The popularity of phytoestrogen food supplements of plant origin steadily increases. They are used to solve the problems related to the climacterium. Their efficiency depends on woman's capability to metabolise the active components - isoflavonoids. Women able to convert daidzein to S-equol are supposed to get a greater benefit from these supplements. To determine S-equol urine levels, the competitive ELISA was developed. Carboxymethylequol coupled to BSA via 4'-O-position was used as an immunogen. The assay conditions, including the concentrations of the coating antigen and antisera, were optimised. The detection limit was 0.1 ng/ml (5 pg/well) and 50% intercept was 1 ng/ml (50 pg/well). The intraassay coefficients of variation (CV) varied from 4.7% to 9.9%, for the interassay CV the corresponding values of 2.6-11.6% were obtained. The recovery of the standard added to urine ranged between 89% and 104%. All examined samples were obtained from women in climacterium. The volunteers had been taking phytoestrogen food supplements for 3 months. The urine samples were collected before and after the therapy. The levels of free urinary S-equol after the therapy ranged between 0 ng/ml and 42.4 ng/ml. The equol production was observed in 57% of the examined patients. The laboratory results were confronted with patients' subjective evaluations.

Phosvitin phosphopeptide preparation using immobilised trypsin and enhancing calcium absorption in growing ratsFood Analysis, Food Quality and Nutrition

Qiang Zhong, Xing-Ling Li, Wei-Dong Hu, Bo Zeng, Ren-Ming Liang, Hui Liu, Zai-Xin Li, Zhi Zhang

Czech J. Food Sci., 2016, 34(4):325-331 | DOI: 10.17221/425/2015-CJFS

We demonstrate a new, efficient method for the preparation of phosvitin phosphopeptides using immobilised-trypsin enzymolysis technology. Immobilised trypsin was prepared using a covalent binding method, and then was added to degrade egg yolk phosvitin for the production of phosphopeptides. In our results, the prepared immobilised trypsin demonstrated a higher hydrolysing activity toward phosvitin than free trypsin, and the hydrolysing activity was retained well even after trypsin was repeatedly used up to five times. Interestingly, the phosvitin phosphopeptides prepared with immobilised trypsin demonstrated a lower N/P ratio and a higher calcium-binding efficiency than those prepared with free trypsin. Furthermore, phosphopeptides significantly increased the rate of calcium absorption and serum calcium content in vivo. Based on these results, we conclude that trypsin immobilised onto chitosan has a greater phosvitin hydrolysing activity than free trypsin, and the prepared phosphopeptides can be used as a new calcium supplement to significantly increase calcium absorption in growing rats.

Evaluation of wheat/non-traditional flour compositeOriginal Paper

Taťana Hofmanová, Marie Hrušková, Ivan Švec

Czech J. Food Sci., 2014, 32(3):288-295 | DOI: 10.17221/311/2013-CJFS

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.

Preparation of conjugated linoleic acid enriched derivatives by conventional and biphasic isomerisationFood Chemistry and Safety

Jan Kyselka, Lukáš Thomes, Simona Remišová, Miroslav Dragoun, Markéta Berčíková, Vladimír Filip

Czech J. Food Sci., 2016, 34(6):511-521 | DOI: 10.17221/362/2016-CJFS

The preparation of conjugated linoleic acid (CLA)-enriched free fatty acids by industrial processes compared with our biphasic isomerisation experiments in a special designed reactor enabling the preparation of CLA esters was evaluated. Our experiments further revealed the main disadvantage of semi-synthetic alkali isomerisation to be the formation of conjugated E,E-octadecadienoic acid isomers (2.92-3.44%) and the bioavailability of free fatty acid products. Urea fractionation technology improved the quality of the reaction mixture, but at the same time the yield of rumenic acid was decreased on purification. Therefore, we decided to apply complexes of noble metals in order to isomerise linoleic acid ester derivatives. The known Wilkinson's hydrogenation catalyst, RhCl (PPh3)3, was found to be the most effective. We investigated the preparation of bioavailable CLA-enriched triacylglycerols. Special attention was paid to recycling of Wilkinson's catalyst.

Quality of eggs in different production systemsFood Technology and Economy, Engineering and Physical Properties

Guler Yenice, Ozgur Kaynar, Mustafa Ileriturk, Feryaz Hira, Armagan Hayirli

Czech J. Food Sci., 2016, 34(4):370-376 | DOI: 10.17221/33/2016-CJFS

This experiment was carried out to compare morphological egg quality parameters, as well as lipid and protein profiles, of brown eggs laid by chickens reared under different production systems: cage, free-range, and family type. A total of 270 brown eggs were obtained from commercial poultry companies raising Lohmann Brown laying hens in a cage system and free-range unit as well as families possessing hens in their yards. The egg lipid and protein contents, as well as lipid and protein profile, varied among the production systems. However, eggs from the free-range system had similar characteristics to those from the cage system. Quality of eggs from the family type system was quite variable. In conclusion, egg quality can be affected by the production system.

Effect of slurry incorporation into retentate on proteolysis of Iranian ultrafiltered white cheeseFood Technology and Economy, Engineering and Physical Properties

Rahele Nezhad Razmjoui Akhgar, Javad Hesari, Sodeif Azadmard Damirchi

Czech J. Food Sci., 2016, 34(2):173-179 | DOI: 10.17221/361/2015-CJFS

The effect of addition of ripened cheese slurry into retentate on the proteolysis of Iranian ultrafiltered cheese was investigated during 60-day ripening. No significant differences were found in gross composition between experimental samples, however, pH values were significantly higher (P > 0.05) in slurry-containing cheese. Urea-polyacrylamide gel of the pH 4.6 insoluble fractions showed that αs1-casein was hydrolysed more rapidly than β-casein. There was no significant difference in the hydrolysis rate of αs1- and β-casein between the two cheeses. The levels of water soluble nitrogen were significantly higher (P > 0.05) in slurry-containing samples from day 15. The incorporation of ripened slurry into retentate influenced the peptide profiles obtained by RP-HPLC of the pH 4.6-soluble fractions of the cheeses. The ratio of hydrophilic to hydrophobic peptides was higher in slurry-containing cheese. Total and individual free amino acids were significantly higher (P > 0.05) in cheeses containing slurry. It was concluded that the incorporation of ripened cheese slurry into retentate has a beneficial effect on proteolysis acceleration and development of aroma and flavour in Iranian ultrafiltered white cheese.

Spent brewer's yeast extracts as a new component of functional foodFood Technology and Economy, Engineering and Physical Properties

Bartłomiej Podpora, Franciszek Świderski, Anna Sadowska, Rita Rakowska, Grażyna Wasiak-Zys

Czech J. Food Sci., 2016, 34(6):554-563 | DOI: 10.17221/419/2015-CJFS

The use of yeast extracts as a natural and valuable additive ingredient intended for the production of functional food and dietary supplements were demonstrated. The chemical composition, amino acid analysis, determination of protein molecular weights, antioxidant properties, and sensory evaluation were carried out for two yeast extracts. It was found that the tested extracts are characterised by high essential amino acid content, exceeding the levels of reference protein developed by the FAO/WHO, and high antioxidant activity. Sensory characteristics of tested extracts may favourably influence the quality of the proposed functional foods and dietary supplements. The obtained results indicate that the tested extracts can be utilised as a source of free amino acids and peptides in the design of functional foods and dietary supplements.

Antilisterial activity of lactic acid bacteria against Listeria monocytogenes strains originating from different sourcesOriginal Paper

Ivana SLOŽILOVÁ, Sabina PURKRTOVÁ, Michaela Kosová, Miroslava Mihulová, Eva ŠVIRÁKOVÁ, Kateřina DEMNEROVÁ

Czech J. Food Sci., 2014, 32(2):145-151 | DOI: 10.17221/475/2012-CJFS

Eight individual bacteriocin-producing lactic acid bacteria (LAB) strains and three bacteriocin-non-producing cheese starter cultures were evaluated for their ability to inhibit the growth of six Listeria monocytogenes strains, originating from the guinea-pig lymph nodes, raw cow milk, and manufacturing dairy equipment. Results showed that either live cells or cell-free neutralised supernatant (CFNS) and/or heated CFNS of six individual LAB strains (Lcc. lactis subsp. lactis CCDM 416 and NIZO R5, Lbc. plantarum HV 11 and DC 1246, P. acidilactici HV 12, and Ent. mundtii CCM 1282) and one starter culture (DELVO-ADD® 100-X DSF) were effective in the suppression of at least one listeria strain. Neither any individual LAB strain nor starter culture was antagonistic toward all studied L. monocytogenes strains, indicating diverse sensitivity/resistance among L. monocytogenes strains to antimicrobial compounds of LAB. The significant susceptibility of listerias isolated from raw milk and dairy equipment together with the strong antilisterial activity of DELVO-ADD® 100-X DSF could be applied in dairy technology, where commonly used starter cultures could play both the biopreservative and fermentation role.

Microbiological quality of raw milk in the Czech RepublicFood Microbiology and Safety

Kateřina Bogdanovičová, Marcela Vyletělová-Klimešová, Vladimír Babák, Libor Kalhotka, Ivana Koláčková, Renáta Karpíšková

Czech J. Food Sci., 2016, 34(3):189-196 | DOI: 10.17221/25/2016-CJFS

The microbiological and hygienic quality of cow's, goat's and sheep's milk in the Czech Republic was evaluated. Milk (230 samples) was collected on 41 farms and investigated from May 2012 to October 2014. Milk was analysed for the presence of selected groups and types of bacteria: mesophilic microorganisms (total plate count - TPC), enterococci, Enterobacteriaceae, Escherichia coli, Staphylococcus aureus, Salmonella spp., Campylobacter spp., and Listeria monocytogenes. Besides these indicators and pathogenic agents, somatic cell count was determined as one of the indicators of mammary gland health in cows. TPC ranged between 8.3 × 102 and 1.2 × 109 CFU/ml and somatic cells between 1.6 × 104 and 6.8 × 106 cells/ml. The presence of E. coli was confirmed in 86.3% of samples and the colony counts ranged from 1.0 × 101 to 4.0 × 106 CFU/ml. The presence of verotoxigenic E. coli was confirmed in 3 samples (1.3%) (cow's milk 0%; goat's milk 6.3%; sheep's milk 4.4%). The presence of S. aureus was confirmed in 29.1% of the samples (cow's milk 26.9%; goat's milk 34.4%; sheep's milk 39.1%), but the numbers were very low (< 5.0 × 102 CFU/ml). L. monocytogenes was confirmed in 3 examined samples (1.3%) (cow's milk 0.6%; goat's milk 3.1%; sheep's milk 4.4%). Salmonella spp. and Campylobacter spp. were not detected in any of the samples tested.

Alcohol and Health: Standards of Consumption, Benefits and Harm - a ReviewReview

Isabela Maria MONTEIRO VIEIRA, Brenda Lohanny PASSOS SANTOS, Denise SANTOS RUZENE, Tomáš BRÁNYIK, José António TEIXEIRA, João Batista DE ALMEIDA E SILVA, Daniel PEREIRA SILVA

Czech J. Food Sci., 2018, 36(6):427-440 | DOI: 10.17221/117/2018-CJFS

In order to establish a clear limit between protective and harmful effects of alcohol consumption, it is necessary to define patterns of consumption. However, there is no universally recognized quantitative classification for patterns of consumption by alcohol doses. This is because the pattern of alcohol consumption does not only describe how much alcohol was consumed, but also takes into account a number of boundary conditions. This review deals with variabilities in the definitions of standard alcohol doses and patterns of alcohol consumption. These terms are being discussed with respect to the benefits and harms associated with alcohol consumption as well as the risks intrinsic to studies of such a complex phenomenon as the effect of alcoholic beverages on human health.

Geographical origin of honey from eight sub-regions of Bosnia and HerzegovinaFood Analysis, Food Quality and Nutrition

Vildana Alibabić, Melisa Oraščanin, Nada Vahčić

Czech J. Food Sci., 2017, 35(6):488-495 | DOI: 10.17221/82/2017-CJFS

Principal component analysis (PCA) and cluster analysis (CA) were used to define the geographical origin of three types of monofloral (chestnut, linden, and acacia), two types of multifloral (meadow and mixed), and forest honey produced over two consecutive harvest seasons in the Una-Sana Canton (Bosnia and Herzegovina), which is geographically divided into eight sub-regions. Statistical analysis was applied to the measurement of physico-chemical and sensory parameters, as well as micro- and macronutrient (K, Na, Mg, Zn, Fe, Mn, and Al) content, along with some heavy metals (Cd, Pb, and As). Using the PCA method the characteristic parameters for all eight sub-regions were determined, while the CA grouping method was used to determine the characteristic parameters for six sub-regions. Chestnut honey is predominantly found in Cazin, chestnut and linden honey in Bosanska Krupa, chestnut and acacia honey in Bužim, acacia honey in Sanski Most, mixed honey in Velika Kladuša and forest honey in Ključ.

Convective and microwave drying of onion slices regarding texture attributesFood Technology and Economy, Engineering and Physical Properties

Özge SÜFER, Hande DEMIR, Seda SEZER

Czech J. Food Sci., 2018, 36(2):187-193 | DOI: 10.17221/310/2017-CJFS

The textural characteristics of onion slices (Allium cepa L.) of 3- and 7-mm thicknesses undergoing convective drying (50, 60, and 70°C) and microwave drying (68, 204, and 340 W real effective power levels) techniques with or without pre-treatment were evaluated. Pre-treatment consisted of dipping into brine solution (8% NaCl). Texture profile analysis at 25% compression was applied and hardness, chewiness, springiness and gumminess values of onions were recorded. As the temperature (convective) or real effective power level (microwave) increased, the hardness and chewiness levels of dried onion slices were enhanced. The values of these parameters were higher in response to microwave application compared to convective drying. Pre-treatment had an additive effect on hardness and chewiness in convectively dried samples. Maximum springiness was observed in response to convective drying. Dipping in brine solution generally caused no significant changes among slices of the same thickness (P < 0.05). With respect to gumminess, the results were quite similar to those for hardness and chewiness, i.e., markedly higher in microwave-dried onions.

Quality of shiitake stipe steamed bun

Yu-Hsiu Tseng, Joan-Hwa Yang, Chi-En Lee, Jeng-Leun Mau

Czech J. Food Sci., 2011, 29(1):79-86 | DOI: 10.17221/171/2009-CJFS

Shiitake [Lentinula edodes (Berk.) Pegler] stipe was incorporated into steamed bun. Quality attributes including the specific volume, colour and sensory evaluation, and taste components in shiitake stipe steamed buns were analysed and compared with those of white steamed buns. With 2% and 5% additions of shiitake stipe flour, specific volumes of steamed buns increased by 5.8% and 5.0%, respectively. White steamed buns contained more reducing sugar, fat, and protein whereas fiber and soluble polysaccharide contents were higher in shiitake stipe steamed buns. Furthermore, shiitake stipe steamed buns contained more total soluble sugars and total free amino acids. Shiitake stipe steamed buns showed lower lightness and whiteness index values and became browner with more shiitake stipe flour added. On a seven-point hedonic scale, all sensory results were 4.07-5.80. Overall, shiitake stipe could be added into steamed bun formula to provide its beneficial health effects.

Reduced microbiological contamination following irrigation of germinated seed for foodsFood Technology and Economy, Engineering and Physical Properties

Honorata DANILČENKO, Elvyra JARIENÉ, Dalé TELEVIČIUTÉ, Skaidré SUPRONIENÉ, Jurgita KULAITIENÉ, Živilé TARASEVIČIENÉ, Alvyra ŠLEPETIENÉ, Judita ČERNIAUSKIENÉ

Czech J. Food Sci., 2018, 36(2):139-145 | DOI: 10.17221/267/2017-CJFS

Germinated seeds are rich in various nutrients but are vulnerable to fungal contamination which favours micromycete formation on the sprouts. The main aim of this work was an investigation of strategies to reduce the contamination of sprouted seed foods. Over the course of 96 hours of sprouting, seeds of organic spring wheat (Triticum aestivum L.), winter wheat (Triticum aestivum L.), naked oat (Avena nuda L.), triticale (xTriticosecale) and rye (Secale cereale L.) were irrigated in water filtered using the Pazdroid Med-1500 filtration device with and without 4% ethyl alcohol. Germinated seeds were stored at 18°C for one, three and seven days and the levels of Mucor spp., Penicillium spp., Alternaria spp., Aspergillus spp., Fusarium spp. and Bipolaris spp were determined. Micromycete numbers were greater in sprouted winter wheat and rye but were reduced when these were soaked and irrigated with filtered water and filtered water containing 4% ethyl alcohol. Filtered water led to greater reductions in micromycete numbers in sprouted winter and spring wheat than in other seeds.

Identification of biphenyls - contaminants responsible for off-flavour in soft drinksFood Chemistry and Safety

Iveta ŠÍSTKOVÁ, Vojtěch KRUŽÍK, Aleš RAJCHL, Helena ČÍŽKOVÁ

Czech J. Food Sci., 2018, 36(1):16-21 | DOI: 10.17221/297/2017-CJFS

Off-flavour in soft drinks is one of the main threats to manufacturers, which can result in expensive recalls, and discredit the brand. Off-flavours can occur for a variety of reasons (e.g . chemical contamination of raw material). The presented case study has proved there is a relationship between the identification of biphenyl and its derivatives in the used preser vative (benzoate) and off-flavours in the drink . The project consisted of three phases: (1) the assessment of the probable cause of off-f lavours based on sensor y evaluation and GC-MS -Olfactometr y profiling of volatiles; (2) the quantification of biphenyls and the characterisation of their sensor y properties; (3) the screening of commercially available benzoates for the presence of biphenyls. Based on the odour threshold obtained by GC-O (0.03 mg/l for 4-methyl-1,1'-biphenyl and 0.02 mg/l for biphenyl in an aqueous solution) and the common benzoate content in soft drinks (0.14 g/l), the 'non-obser vable sensory' levels of contamination were determined to be maximally 0.143 mg/g of benzoate for biphenyl and 0.214 mg/g of benzoate for 4-methyl-1,1 '-biphenyl .

Rapid detection of microbial contamination in UHT milk: practical application in dairy industryFood Analysis, Food Quality and Nutrition

Martina KRAČMAROVÁ, Hana STIBOROVÁ, Šárka HORÁČKOVÁ, Kateřina DEMNEROVÁ

Czech J. Food Sci., 2018, 36(5):357-364 | DOI: 10.17221/24/2018-CJFS

Microbial quality of ultra-high temperature (UHT) milk is usually ascertained by a total bacterial count (TBC) cultivation. But this is time consuming, so there is a tendency to search for faster and simpler methods. We compared three instruments, focusing on shortening the detection time and their suitability for practical use in dairy plants. Two of them, RapiScreen Dairy 1000 and Promilite III, detect microbial contamination by measuring adenosine triphosphate bioluminescence; the third, GreenLight, is based on oxygen consumption analysis. In the laboratory experiments, samples of UHT milk, were spiked with low concentration of microorganisms and then the level of microbial contamination was evaluated using the above-mentioned instruments together with cultivation method as a control. The instruments were also applied in a dairy plant to test 182 real samples. All investigated methods determined microbial quality faster than the TBC, but in some cases false positive and false negative results were obtained. Therefore, precise testing including optimizing pre-incubation time for bacteria enrichment is needed prior to industrial use.

Phytochemical changes in mango fruit in response to Alternaria alternata infectionFood Analysis, Food Quality and Nutrition

Jiao LI, Liangang MAO, Yanning ZHANG, Lan ZHANG, Hongyun JIANG

Czech J. Food Sci., 2018, 36(3):227-232 | DOI: 10.17221/328/2017-CJFS

Changes in mango fruit quality, malondialdehyde content, and enzymatic activities in response to pathogen Alternaria alternata infection were studied. A. alternata significantly affected the appearance of mango fruit at 5 and 7 days after treatment (DAT). The quality of pathogen-infected fruit first showed a significant decrease in titratable acidity and vitamin C content and a significant increase in pH since 3 DAT. The malondialdehyde content was higher than that in the untreated controls at 3 and 7 DAT. The enzyme activities of ascorbate peroxidase and polyphenol oxidase showed significant increases since 3 DAT. Significant increases in l-phenylalanine ammonia-lyase and superoxide dismutase activities were observed at 7 DAT. These results indicate that A. alternata infection first significantly affects some biochemical constituents and enzyme activities in mango fruit since 3 DAT and that there was no significant effect on appearance until 5 DAT.

Changes in the levels of selected organic acids and sugars in apple juice after cold storageFood Technology and Economy, Engineering and Physical Properties

Ján MEZEY, Ivana MEZEYOVÁ

Czech J. Food Sci., 2018, 36(2):175-180 | DOI: 10.17221/165/2017-CJFS

Apples are a source of sugars, acids, and various biologically active compounds, such as phenolic compounds, which are responsible for most of the antioxidant activities of the fruit. The aim of this study was to evaluate how the cold storage of apple fruits affects the nutritional composition of selected organic acid and sugar content in juice in comparison to juice from fresh fruits. Statistical differences were confirmed between the content of citric acid, malic acid, total acid, pH, sucrose, fructose and glucose in juice from fresh fruits and from juice stored for 140 days. No statistical differences were observed between juice from fresh fruit and juice from fruits stored for 140 days in the content of acetic acid, tartaric acid, total sugar and sweetness index.

Development of a triplex real-time PCR for simultaneous detection of allergenic ingredients in processed foodFood Chemistry and Safety

Wenju ZHANG, Yulei ZHAO, Qingjin XU, Qin CHEN

Czech J. Food Sci., 2018, 36(1):22-27 | DOI: 10.17221/28/2017-CJFS

SYBR Green real-time or quantitative PCR (Q-PCR) is a suitable system in which to establish a multiplex method to detect allergenic ingredients in food. In this study, a triplex Q-PCR method was developed to detect trace amounts of peanut, soybean and sesame in processed food. Specific PCR primer sets were designed and the concentration of the primers used in the triplex PCR was optimised. The triplex method showed high specificity and sensitivity which were similar to those of the simplex method, and it was applied for the detection of allergenic ingredients in commercially available processed food. The results demonstrate that the developed triplex Q-PCR is a quick, reliable and efficient method for the detection of allergenic ingredients in processed food.

Rapid evaluation of fresh chicken meat quality by electronic noseFood Technology and Economy, Engineering and Physical Properties

Edita RAUDIENÉ, Darius GAILIUS, Rimanté VINAUSKIENÉ, Viktorija EISINAITÉ, Gintautas BALČINAS, Justina DOBILIENÉ, Laura TAMKUTÉ

Czech J. Food Sci., 2018, 36(5):420-426 | DOI: 10.17221/419/2017-CJFS

A prototype of electronic nose (e-nose) with the gas sensor system for evaluation of fresh chicken meat freshness was developed. In this paper a rapid, simple and not expensive system for fresh chicken meat spoilage detection was investigated that provides objective and reliable results. Quality changes in fresh chicken meat during storage were monitored by the metal oxide sensor (MOS) system and compared with the results of traditional chemical measurements. Gas sensor selection was tested for evaluation of volatile fatty acids (VFA) mainly representing meat spoilage.The study demonstrated that a correlation coefficient (R2 = 0.89) between e-nose signals and traditional chemical method was high. These results prove that the developed e-nose prototype has a potential for assessing fresh chicken meat freshness and allows discriminating meat into fresh, unsafe and spoiled.

Influence of modified atmosphere packaging on freshness parameters of organic chicken meat - short communicationShort Communication

Fouad Ali Abdullah Abdullah, Hana Buchtová, Peter Turek

Czech J. Food Sci., 2017, 35(5):466-468 | DOI: 10.17221/32/2017-CJFS

The effect of modified atmosphere packaging (MAP1 80% O2/20% CO2 and MAP2 70% N2/30% CO2) on the selected parameters (ammonia, thiobarbituric acid reactive substances /TBARS/) and antioxidant capacity in chilled meat (2 ± 2°C) of organic chickens (breast and thigh) was evaluated. Control samples were packaged using a polyolefin film. The experiment was conducted on day 2 and repeated on day 7, 10, and 14 of storage. TBARS of samples in MAP1 were higher than in samples stored in MAP2. Ammonia in meat in MAP2 was constant during storage. In general, the DPPH inhibition percentage of meat in MAP1 was lower than that in meat in MAP2. Results of the present study indicated that MAP2 could be preferable for the packaging of organic chicken meat.

Biochemical changes of Iranian probiotic Lighvan cheeseFood Technology and Economy, Engineering and Physical Properties

Alireza SHAHAB LAVASANI

Czech J. Food Sci., 2018, 36(2):181-186 | DOI: 10.17221/453/2016-CJFS

Lighvan cheese from ewe and goat milk was produced according to a traditional protocol, and with the addition of 9 log10 cfu/g fresh cells of Bifidobacterium lactis subsp. animalis. Probiotic Lighvan cheese was studied to determine the survival of B. lactis subsp. animalis and biochemical changes during 60 days of ripening of probiotic Lighvan cheese. Lipolysis level and organoleptic assessments were analysed. B. lactis subsp. animalis cells survived in cheese samples at concentrations up to 6.84 log10 cfu/g for at least 60 days of storage time. The lipolysis level increased continuously until the end of the ripening period.The ripening stage was the main factor affecting the cheese sensory properties.

A negative correlation between mercury content in muscle and body weight in carp from uncontaminated pondsFood Technology and Economy, Engineering and Physical Properties

Lenka Sedláčková, Jiří Jarkovský, Jiří Kalina, Gorzyslaw Poleszczuk, Zdeňka Svobodová

Czech J. Food Sci., 2015, 33(3):204-209 | DOI: 10.17221/165/2014-CJFS

The relationship between body weight and total mercury content in the muscle of common carp (Cyprinus carpio) from 13 uncontaminated ponds in South and West Bohemia was investigated. In total, 215 three-years-old marketable carps and 26 samples of bottom sediment were analysed. Total mercury contents (THg) in muscle and sediments were determined using an single-purpose atomic absorption spectrophotometer. The correlation between body weight and mercury content in muscle was found to be negative and statistically significant (Pearson correlation: rp = -0.269, P < 0.001). THg content in muscle significantly decreased as the body weight of carp from uncontaminated ponds increased. This is likely due to the intensive weight gain of marketable carp.

Antioxidant activity of peanut skin extracts from conventional and high-oleic peanuts

Van Ha HOANG, Petra APOŠTOLOVÁ, Jana DOSTÁLOVÁ, František PUDIL, Jan POKORNÝ

Czech J. Food Sci., 2008, 26(6):447-457 | DOI: 10.17221/29/2008-CJFS

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.

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