Papers by velichka yanakieva
Journal of Apicultural Science
Propolis (bee glue), a valuable biological mixture produced by European honey bees (Apis mellifer... more Propolis (bee glue), a valuable biological mixture produced by European honey bees (Apis mellifera L.), is widely used as a remedy in traditional and alternative medicine, as an effective food biopreservative and as a nutritional value enhancer. The present study aimed to investigate eighty propolis samples collected from all twenty-eight districts of Bulgaria in the period of 2020–2022 in order to determine their physicochemical properties as well as their antioxidant and antimicrobial potential. The raw propolis samples exhibited brown or green colour depending on the climatic zone from which they are collected and pH values from 4.82 to 5.87, while the moisture content ranged between 0.98% and 2.97%. The total phenolics content (TPC) and total flavonoids content (TFC) varied from 63.14 mg GAE/g to 737.27 mg GAE/g, and from 29.22 mg QE/g to 234.17 mg QE/g, respectively. The propolis samples demonstrated significant antioxidant potential determined by DPPH and FRAP methods, from 18...
Acta Alimentaria, 2018
The development of food products that contain value-added dietary fi bre beside different classes... more The development of food products that contain value-added dietary fi bre beside different classes of phytochemicals is of great interest nowadays. The present research aimed to evaluate the powder obtained from onion processing waste (OPW) for its potential use as a value-added by-product in food sector. Data on chemical and microbiological characterization of onion processing waste powder (OPWP) were obtained. The dietary fi bre content and antioxidant activity were also determined. The results showed that the OPWP was a low-calorie natural source of insoluble fi bres (60.52±0.13 g/100 g dw), total phenols (41.04±1.22 mg GAE/g dw), and total fl avonoids (20.44±1.22 mg QE/g dw). Moreover, the OPWP could be considered as an important source of total fructans (9.04±0.28 g/100 g dw), fructooligosaccharides (2.76 g/100 g dw), and inulin (2.41±0.18 g/100 g dw). In conclusion, this OPWP could be used as a value-added and healthy food ingredient.
The current scientific research is focused on the moisture equilibrium data (adsorption and desor... more The current scientific research is focused on the moisture equilibrium data (adsorption and desorption) of defatted grape seeds flour at 10, 25 and 40 °C using the static gravimetric method of saturated salt solution and relative humidity from 0.11 to 0.90. The results showed that the sorption capacity decreased when the temperature increases in the conditions of constant water activity. The modified Henderson model describe satisfactorily the sorption isotherms. The MMC was determined using Brunauer-Emmett-Teller (BET) equation that results for adsorption were in the range of 2.61 to 4.81 % and for desorption-from 2.67 to 4.25 %. We were optimized the storage regime up to six-month of the flour in plastic bags at temperature 25 ºC and relative humidity 75 %. No living cells of pathogenic organisms (Escherichia coli, Staphylococcus aureus and Salmonella spp.) or apparent molding were detected. The flour particle size has not changed either.
Food and Environment Safety Journal, Feb 7, 2017
A successful intergeneric recombination by protoplast fusion between Lactobacillus acidophilus 2 ... more A successful intergeneric recombination by protoplast fusion between Lactobacillus acidophilus 2 and Bifidobacterium bifidum L1 is performed. The strain Lactobacillus RL15 with high reproductive capacity and moderate acidity, that doesn't cause sliming of milk is selected. Using modern molecular genetic methods it has been found that the hybrid inherits the genome of one of the parental strains. It is shown that in the united genome occur changes, which are expressed in the hybrid's phenotypic properties, enzyme profile and technological parameters.
Food Science, Engineering and Technologies 2009, Plovdiv, Bulgaria. 23-24 October, 2009., 2009
Food Science, Engineering and Technologies 2009, Plovdiv, Bulgaria. 23-24 October, 2009., 2009
Zeitschrift für Naturforschung C, Jun 21, 2021
The purpose of this study was to investigate the microbiological (number of viable lactic acid ba... more The purpose of this study was to investigate the microbiological (number of viable lactic acid bacteria and bifidobacteria), physicochemical (dry matter, protein and fat contents, titratable acidity, and pH), and sensory characteristics (appearance of coagulum, taste and aroma, structure at cutting, color, and consistency at shattering) of probiotic Bulgarian yoghurts obtained by ultrafiltration of goat’s milk. These yoghurts were obtained using volume reduction ratios of 2 and 3 with the probiotic starters MZ2f, MZ2f + Bifidobacterium bifidum BB – 87, and MZ2f + Lactobacillus acidophilus LAB – 8. The increase in the level of the concentration by ultrafiltration led to an increase in the dry matter, protein and fat contents of the yoghurts, in the number of lactic acid bacteria and titratable acidity, and to a decrease in the pH. The twofold concentration by ultrafiltration resulted in a higher number of lactic acid bacteria in comparison with yoghurts made without ultrafiltration, and with better sensory characteristics compared to yoghurts without and with threefold ultrafiltration. The higher number of viable cells and better sensory characteristics were obtained for yoghurts with MZ2f + Bifidobacterium bifidum BB – 87 and MZ2f + Lactobacillus acidophilus LAB – 8 in comparison with MZ2f alone.
Food and Environment Safety Journal, Apr 21, 2016
Probiotics help restore the balance of the gastrointestinal microflora, but only strains with cer... more Probiotics help restore the balance of the gastrointestinal microflora, but only strains with certain properties can be included in their formulations. One of the requirements for a strain to be probiotic is to exhibit inhibitory activity against pathogens.The antimicrobial activity of the strain Lactobacillus delbrueckii ssp. bulgaricus GB against the pathogens E.coli ATCC 25922, E.coli ATCC 8739, Salmonella abony NTCC 6017, Salmonella sp., Staphylococcus aureus ATCC 25293 and Proteus vulgaris J is determined by joint cultivation at 37±1°C. Lactobacillus delbrueckii ssp. bulgaricus GB inhibits the growth of the pathogens-for 60-72 hours the numbers of viable cells of the pathogens are reduced. It has been shown that the changes in the proportions in the mixed populations are due to the accumulation of lactic and other organic acids which acidify the medium and change the conditions for the growth of the pathogens, leading to reduction of the number of viable cells of the pathogens. The demonstrated inhibitory activity of Lactobacillus delbrueckii ssp. bulgaricus GB makes the strain potentially probiotic and after additional studies it can be included in the composition of probiotics and functional foods.
ABSTRACT The strain LAB BP15 was isolated from naturally fermented cereal beverage (boza). The id... more ABSTRACT The strain LAB BP15 was isolated from naturally fermented cereal beverage (boza). The identification of the strain was determined by conducting biochemical tests with the system API 50 CHL (BioMerieux SA, France) and moleculargenetic studies - ARDRA analysis and sequencing of the 16S rRNA gene. The results of the molecular-genetic studies identified the studied strain as a representative of the species Weisella confusa.
BIO web of conferences, 2023
Akademik Gıda, Sep 1, 2016
The strain BT17 was isolated from a naturally fermented cereal beverage (boza), which is traditio... more The strain BT17 was isolated from a naturally fermented cereal beverage (boza), which is traditional in Balkan countries. The colony characteristics and cell morphology of the strain were determined after its cultivation on a solid culture medium and coloring of microscopic preparations. The strain was identified by biochemical methods-API 50 CHL kit system, followed by apiweb software processing, as well as molecular techniquesamplified rDNA restriction analysis (ARDRA) with the endonucleases Eco RI, Hae III and Alu I, and nucleotide sequencing of the 16S rRNA gene. The results obtained from the biochemical identification showed that the isolated strain of BT17 is related to the species Lactobacillus plantarum 1 (the rate of reliability with 59.1%) and Lactobacillus pentosus (the rate of reliability with 41.2%). The comparative 16S rRNA gene sequence-based phylogenetic analysis revealed 99% pairwise similarity of the studied strain to the bacterial species Leuconostoc lactis. The aim of this study was the identification, biochemical and molecular characterization of a strain Leuconostoc lactis BT17, isolated from a spontaneously fermented cereal beverage (boza).
Molecular-genetic and biochemical characterization of Saccharomyces cerevisiae strain 36-6G. Yeas... more Molecular-genetic and biochemical characterization of Saccharomyces cerevisiae strain 36-6G. Yeast strain 36-6G isolated from naturally fermented cereal beverage (boza) is selected. It is identified as a representative of the species Saccharomyces cerevisiae applying molecular-genetic method-partial sequencing of the 26S rDNA. The enzymatic profile of the strain is determined applying the kit system API ZYM (BioMerieux, France). Its proteolytic and amylase activities are examined as well. It is shown that the Saccharomyces cerevisiae strain 36-6G exhibits amylase activity. The strain is suitable for inclusion in the composition of starter cultures for the production of fermented cereal foods and beverages.
In this experimental work, the microbiological, physicochemical, organoleptic and rheological cha... more In this experimental work, the microbiological, physicochemical, organoleptic and rheological characteristics of probiotic Bulgarian yoghurts produced by ultrafiltration of goat’s milk using different volume reduction ratio (2 and 3) and several probiotic starters (MZ2f, MZ2f + Bifidobacterium bifidum BB – 87, MZ2f + Lactobacillus acidophilus LAB – 8) were studied. It was established that the dry matter, protein, fat contents, the number of lactic acid bacteria, titratable acidity and the dynamic viscosity increased and the pH decreased with the rise of volume reduction ratio during ultrafiltration. All yoghurts exhibited Bingham plastic flow behavior. We recommend to use a volume reduction ratio of 3 and MZ2f + Bifidobacterium bifidum BB – 87 to produce probiotic Bulgarian yoghurts with the highest dry matter, protein, fat contents; counts of viable lactic acid cells, viscosity and the best sensory characteristics in the range of this experiment.
DergiPark (Istanbul University), Sep 1, 2016
The strain BT17 was isolated from a naturally fermented cereal beverage (boza), which is traditio... more The strain BT17 was isolated from a naturally fermented cereal beverage (boza), which is traditional in Balkan countries. The colony characteristics and cell morphology of the strain were determined after its cultivation on a solid culture medium and coloring of microscopic preparations. The strain was identified by biochemical methods-API 50 CHL kit system, followed by apiweb software processing, as well as molecular techniquesamplified rDNA restriction analysis (ARDRA) with the endonucleases Eco RI, Hae III and Alu I, and nucleotide sequencing of the 16S rRNA gene. The results obtained from the biochemical identification showed that the isolated strain of BT17 is related to the species Lactobacillus plantarum 1 (the rate of reliability with 59.1%) and Lactobacillus pentosus (the rate of reliability with 41.2%). The comparative 16S rRNA gene sequence-based phylogenetic analysis revealed 99% pairwise similarity of the studied strain to the bacterial species Leuconostoc lactis. The aim of this study was the identification, biochemical and molecular characterization of a strain Leuconostoc lactis BT17, isolated from a spontaneously fermented cereal beverage (boza).
Bulgarian Journal of Agricultural Science, 2019
The current scientifi c research is focused on the grape seeds-a waste product retrieved after al... more The current scientifi c research is focused on the grape seeds-a waste product retrieved after alcoholic fermentation of wine, in the form of grape seeds fl akes. Recently, the grape residue has been considerated as a functional food product, a source of bioactive compounds (BAC) including antioxidants. The present study presents data about the antioxidant activity of grape seeds fl akes of different grape varieties of Bulgarian origin, analysed via four analytical methods differ in mechanism and reaction conditions, namely DPPH, ABTS, FRAP and CUPRAC. The obtained results were expressed as mM TE/g extract (842.50
Irish Journal of Agricultural and Food Research, 2020
Ultrafiltration of skim cow’s milk with a UF10-PAN membrane at volume reduction ratios (VRRs) of ... more Ultrafiltration of skim cow’s milk with a UF10-PAN membrane at volume reduction ratios (VRRs) of 2 and 3 was performed. The ultrafiltration retentates obtained were used for production of probiotic yoghurts with three different starters. A control sample was prepared using skim cow’s milk. All yoghurts were analysed according to the following parameters: titratable acidity, dry matter, organoleptic characteristics, number of specific microorganisms (Lactobacillus bulgaricus and Streptococcus thermophilus) and the total count of viable lactic acid bacteria for 28 d of storage. The results showed that the increase in the VRR during ultrafiltration increased the titratable acidity, as well as the dry matter of all yoghurts. Ultrafiltration concentration led to an increase in the count of viable lactic acid bacteria in all yoghurts which improved their functional properties. The highest values of the total number of viable lactic acid bacteria were determined in yoghurts obtained with s...
Acta Materialia, 2005
A system of partial differential equations was derived to describe diffusion in the two-phase reg... more A system of partial differential equations was derived to describe diffusion in the two-phase region of a ternary alloy by assuming that the mixture concentration in an infinitesimally small volume can be changed by external fluxes over the boundaries of this volume. A numerical procedure was developed for solving the system of partial differential equation (PDE) and treating the problem with the moving boundaries between various single-phase or two-phase layers. The mathematical model was applied for numerical simulation of the formation and growth of the single-phase and two-phase layers, developed in ternary alloy specimen, through diffusion from the surface to the core.
The antimicrobial activity of Lactobacillus plantarum BG 24 isolated from naturally fermented cer... more The antimicrobial activity of Lactobacillus plantarum BG 24 isolated from naturally fermented cereal beverage (boza) against pathogens-Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa 1390-2 and Listeria monocytogenes-by co-cultivation at 37±1°C was determined. It has been found that the strain Lb. plantarum BG 24 inhibits the growth of pathogenic microorganisms, the reduction being strain specific, and within 60 to 72 hours practically no viable pathogenic cells were detected. In co-culturing of Staphylococcus aureus ATCC 25923 and Lb. plantarum BG 24 complete inhibition occured at the 72 nd h, while in co-culturing of Lb. plantarum BG 24 and Pseudomonas aeruginosa 1390-2 or Listeria monocytogenes-at the 60 th h. It has been shown that the inhibition of the growth of the pathogens is a result of the produced lactic acid and other organic acids which acidify the medium and change the conditions of growth and development of the pathogens. Въведение Полезната микрофлора (лакто...
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Papers by velichka yanakieva