Browsing by Author "Lasheva V."
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Item Antimicrobial active packaging paper based on dill weed essential oil(2020-01-01) Kostova I.; Lasheva V.; Georgieva D.; Damyanova S.; Stoyanova A.; Stefanov S.; Gubenia O.Antimicrobial active packaging based on dill weed essential oil (DWEO) was investigated. Three types of packaging paper (100% bleached pulp 40 g/m2, 100% unbleached pulp 40 g/m2, and 100% recycled paper weighing 70 g/m2) were analysed. The antimicrobial activity was tested against the Gram-positive bacteria Staphylococcus aureus ATCC 6538 and Bacillus subtilis ATCC 6633; the Gram-negative bacteria Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027 and Salmonella abony NTCC 6017; the yeast Saccharomyces cerevisiae ATCC 2601 and Candida albicans ATCC 10231; and the fungal strain Aspergillus brasiliensis ATCC 16404. The activity of the bleached paper treated with DWEO against moulds (Aspergillus brasiliensis) and yeasts (Candida albicans) during the five-day study period decreased from 100 to 47%, against Gram-positive bacreria (Staphylococcus aureus and Bacillus subtilis) decreased from 100 to 69%, and against Gram-negative bacteria (Salmonella abony and Escherichia coli) decreased from 76 to 12%. Unbleached paper, treated with DWEO, had stronger antimicrobial potential against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), compared to other test microorganisms. Recycled paper treated with DWEO showed fungicidal activity.Item APPLICATION POSSIBILITIES OF BIOMASS FROM FENNEL FRUITS(2023-01-01) Nikolova М.; Pencheva M.; Dimov M.; Bozadzhiev B.; Lazarov L.; Damyanova S.; Lasheva V.; Stoyanova A.; Yavorov N.During the processing of fennel fruits (Foeniculum vulgare Mill.) for obtaining essential and vegetable oils, biomass is released. It is mainly used as an additive for feeding or as an organic fertilizer. The aim of this research is to investigate the possibilities of using biomass obtained during the processing of fruits from harvest 2020 and 2021 as a biosorbent of Cr (VI) from aqueous solutions or as a biofuel. The two biomasses were milled and the final fractions obtained by sieve analysis (between 384 and 413 μm) were analyzed. The FTIR spectrum was recorded as 4000 - 400 с-1. Both biomasses act as biosorbent under the following conditions: pH 1.0, agitation speed 300 rpm, adsorbent dose 1.05 g L-1, initial Cr (VI) concentration 80 mg L-1, temperature 30°C. The energy indices used in the assessment of fennel fruit biomass potential as conditional biofuel were calculated: calorific value (15783.40 - 15968.16 kJ kg-1), density (464.19 - 582.91 kg m-3), and heat equivalent (250.05 - 317.68 kJ m-3)Item CHARACTERIZATION OF ACTIVE PAPER PACKAGING MATERIALS WITH CORIANDER ESSENTIAL OIL (CORIANDRUM SATIVUM L.)(2020-01-01) Kostova I.; Lasheva V.; Georgieva D.; Damyanova S.; Fidan H.; Stoyanova A.; Gubenia O.This study aims to investigate the antimicrobial activity of paper-based packaging materials including coriander (Coriandrum sativum L.) essential oil. Three types of packaging papers (bleached, unbleached, and recycled) are treated with an essential oil and then stored for 2 h, 24 h, and 5 days. The antibacterial activity of coriander oil is tested against Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and Bacillus subtilis ATCC 6633); Gram-negative bacteria (Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027, and Salmonella abony NTCC 6017); an yeast (Candida albicans ATCC 10231), and a fungal strain (Aspergillus brasiliensis ATCC 16404). Ahigh fungicidal potential is observed in case of all packaging materials. The antimicrobial action of the bleached paper coated with coriander oil against Gram-positive bacteria during the five-day storage period decreases slightly from 100 % - 94 % to 79 % - 81 %.Item Chitosan-Coated Packaging Papers—Strength and Thermal Stability(2023-05-01) Vrabič-Brodnjak U.; Yavorov N.; Lasheva V.; Todorova D.The aging of paper depends on various factors, including environmental conditions, microbiological factors and chemical composition. Chitosan-coated paper is an eco-friendly material that has potential use in various packaging applications due to its mechanical, barrier and antibacterial properties. In this study, the aging stability of chitosan-coated wood-free wrapping paper was evaluated by examining pulp and four paper samples with different quantities of chitosan. Accelerated thermal aging and dynamic thermogravimetric analysis were used to assess the aging stability, while color changes were examined to understand the impact of chitosan coating. The study found that increasing chitosan coating led to improved aging stability due to the improved crosslinking process between chitosan and paper. The coated paper samples displayed a yellowish hue after 72 h of aging, with increased strength and resistance to weight loss. TGA results indicated that the temperature of complete burning of the sample increased with increasing chitosan coating. Additionally, coated paper samples exhibited a more even surface and improved barrier properties. Overall, chitosan-coated paper is a promising material for sustainable and eco-friendly packaging, printing and wrapping applications. This study’s findings have important implications for the development of environmentally-friendly packaging materials that possess desirable mechanical and barrier properties.Item COMPARATIVE ANALYSIS OF ANTIBACTERIAL ACTIVITY AND PHYSICOCHEMICAL PROPERTIES OF PEPPERMINT AND CORNMINT ESSENTIAL OILS AND THEIR MAIN COMPOUND MENTHOL(2023-01-01) Gandova V.; Fidan H.; Iliev I.; Lasheva V.; Stankov S.; Stoyanova A.; Yavorov N.The aim of the present paper was to study and present a comparative analysis of the antibacterial activity and physicochemical properties of commercial mint essential oils from two different species - peppermint (Mentha piperita Huds. (L.)) and cornmint (Mentha arvensis L.). Peppermint oils exhibited weak antibacterial activity, but were more pronounced against Gram-positive bacteria Staphylococcus aureus (1.3 - 2.0 mm) and Gram-negative bacteria Escherichia coli (1.2 - 1.9 mm) and Klebsiella sp. (2.6 mm). The essential oil of the species M. arvensis did not exhibit antimicrobial activity against the tested cultures. L-menthol, which is a commercial sample isolate, exhibited activity against all tested microorganisms, with the exception of Gram-positive bacteria Listeria monocytogenes and Bacillus cereus. The diameter of the inhibition zones was the largest against Gram-positive bacteria Bacillus subtilis (3.4 mm), and the smallest was against Gram-positive bacteria Staphylococcus aureus (1.6 mm) and Gram-negative bacteria Klebsiella sp. (1.4 mm). The surface tension, density and refractive index of different mint essential oils were determined experimentally. The surface energy and surface heat capacity were calculated based on the calculations of surface tension. All experiments and calculations were provided at a temperature range between 6℃ and 30℃. A dependence between surface tension and temperature was not observed.Item Deinging of recycled paper with offset printing through flotation and use of enzymes(2013-11-05) Lasheva V.; Ilieva B.; Kotlarova S.; Kamburov M.Use of recycled fiber material for the production of paper and paperboard has a significant share in solving problems related to environmental protection and conservation of energy resources. One of the most important processes for the paper recycling with printing press is a deinking. Perspective method for deinking of waste paper by the method of flotation is the enzyme treatment at neutral pH. The aim of this work is to study the deinking of recycled paper with offset printing press through flotation and use of enzymes.Item EFFECT OF CHITOSAN ADDITION DURING PAPER-MAKING ON AGEING STABILITY OF DOCUMENT PAPER(2021-09-01) Todorova D.; Lasheva V.The aim of the present work has been to study the influence of chitosan addition into the composition of paper intended for documents on its ageing stability, with a view of enhancing the resistance of paper strength and optical properties over time. The chitosan solution was added during the formation of the paper sheets in various amounts: 0.2%, 1% and 2% o.d.f. Paper samples of different fibrous compositions were prepared from bleached sulphate softwood pulp (BSWP) and bleached sulphate hardwood pulp (BHWP) in the following ratios: 50% BSWP:50% BHWP, 80% BSWP:20% BHWP, 100% BSWP and 100% BHWP. Then, paper samples were subjected to accelerated thermal ageing for 24 hours at 105 °C. It was found that the use of chitosan as additive in the composition of bleached cellulose paper samples led to improved strength and hygroscopic properties. The study showed that chitosan could be used in the production of kraft document papers comprising aluminium sulphate, as the presence of aluminium sulphate had no negative effect on the action of the biopolymer. Regarding the complex evaluation of the properties of the obtained papers, it could be summarized that, for the studied fibrous compositions, the optimum amount of the additive was 1% chitosan for a fibrous composition of 50% bleached softwood pulp and 50% bleached hardwood cellulose. Therefore, preparing document paper with the addition of chitosan is a convenient procedure to enhance a number of paper properties, even after the ageing process.Item Effect of clary sage (Salvia sclarea L.) essential oil on paper packaging materials(2020-01-01) Kostova I.; Lasheva V.; Fidan H.; Georgieva D.; Damyanova S.; Stoyanova A.Introduction. The aim of research to determine the effect of clary sage (Salvia sclarea L.) essential oil on paper packaging materials. Materials and methods. Three packaging materials have been studied based on paper coated with clary sage essential oil. The chemical composition of the clary sage essential oil is determined chromatographically. Antimicrobial effect of essential oil was determined against Gram-positive, Gram-negative bacteria, yeasts, and fungi using the agar diffusion method. Results and discussion. The chemical composition of the clary sage essential oil showed a predominant amount of oxygenated monoterpenes (83.43%), followed by monoterpene hydrocarbons (7.86%), and sesquiterpene hydrocarbons (5.16%). The major components of the clary sage essential oil were linalyl acetate, B-linalool, α-terpineol, limonene, and geranyl acetate that determined the antimicrobial action of the oil. The essential oil exhibited a fungicidal action against the tested molds and yeasts. Its high antimicrobial properties could be probably due to the high content of linalyl acetate (40.31%) and B-linalool (22.72%). Our results showed high fungicidal efficacy for the three types of packaging materials. The suppressive action against C. albicans during the investigated shelf life period was about 100%. It was found a high efficiency of the recycled paper against A. brasiliensis (99.2%-81.9%). It was determined that the bactericidal effect of the tested packaging materials was lower than the Gram-negative bacterium S. abony. Conclusions. Clary sage essential oil could be used as an antimicrobial agent in the food industry due to its antimicrobial properties, in order to improve the quality of the products and extend their shelf life.Item Investigation on the kinetics of coated paper thermal aging(2019-01-01) Todorova D.; Lasheva V.; Radeva G.; Cenkova R.The paper aging is primarily attributed to the presence of carbonyl groups formed as a result of the oxidation of the hydroxyl groups at the second and third carbon atom in the elementary unit of the cellulose macromolecule and the presence of both aldehyde and carboxyl groups in the cellulose materials. Reduction of paper whiteness degree is mainly connected with the presence of lignin, hemicelluloses, the presence of metals and the sizing agent type. The paper as an elasto-plastic, capillary porous material quickly breaks down at an elevated temperature. The latter accelerates the chemical reactions that occur in paper in the course of aging. The depth of the paper changes depends not only on the temperature but also on the duration of the impact. For different paper types differing in composition the reaction rate constant is different. Its temperature dependence is described by the Arenius equation. The aim of this work is to carry out a kinetic analysis of the influence of the temperature increase on the ageing of coated paper used for book covers. The accelerated thermal aging is conducted at three different temperatures-90°C, 105°C and 120°C with duration of 6 h, 12 h, 18 h, 36 h and 48 h. In order to examine the kinetics of the process the level of whiteness is determined. The data obtained from the thermal aging of the paper are treated using the laws of polychrome kinetics.Item Lavender Essential Oil as Antibacterial Treatment for Packaging Paper(2023-01-01) Todorova D.; Yavorov N.; Lasheva V.; Damyanova S.; Kostova I.Based on many years of experience, packaging is considered as an inactive barrier that protects materials and goods from environmental factors. The applicability of native chemical additive such as essential oils in wrapping papers can be used in the forms of films, treatments, coatings or others. Essential oils or extracts from different aromatic plants are used as bioactive substances for antimicrobial activity. In this research, lavender essential oil treatment of packaging papers is examined for its inhibition activity under nine microorganisms—two Gram-positive bacteria, three Gram-negative bacteria, two yeast and two fungal strains. The effectiveness of the treatment on the structural and strength indicators of the obtained paper samples is monitored. In detail, a five-day examination is conducted on the antibacterial effectiveness of lavender essential oil treatment. Results indicate that the lavender treatment of the obtained packaging paper is successful and the antifungal effect is more pronounced. The antimicrobial efficiency of paper treated with lavender essential oil is between 60 and 90% in the first two hours after treatment and gradually decreases to 40%–50% at the end of the 120 h period. The lavender essential oil treatment of wrapping paper has a promising perspective for preserving products from microbial spoilage and extending their shelf life.Item Microscopic Analysis Of Japanese And Wax Paper Used For The Preservation Of Written Cultural Heritige(2021-01-01) Tsvetanska-Tsekova I.; Lasheva V.; Yankova I.; Peteva I.; Vasileva R.; Stancheva S.The paper is an integral part of our cultural development. Its’ properties are determined by the properties of the fibrous materials of which it is composed by and from the technological regime in its production. The good knowledge of the fibrous materials used, their chemical composition, morphological and anatomical structure in the restoration practice is essential for proper conduction of the recovery procedures. In world restoration practice, Japanese paper is the most often used material for the renovation of paper documents. The examination and microscopic analysis of Japanese paper contributes to its proper use in restoration practice.Item POSSIBILITIES FOR IMPARTING ANTIBACTERIAL PROPERTIES TO PAPERS(2023-01-01) Lasheva V.; Todorova D.; Yavorov N.; Damyanova S.; Kostova I.Paper is widely used as a packaging material because it is biodegradable and completely safe for the environment. The use of antimicrobials as a coating on paper can improve its mechanical, optical, physical and antimicrobial properties. Antimicrobial packaging suppresses the development of pathogenic microorganisms in order to ensure the safety of the product, extend the shelf life and protect the quality of the product. Giving antibacterial properties to papers and cardboards expands their use in different areas and for different purposes. Antibacterial paper prevents the entry and development of harmful microorganisms such as bacteria, fungi, mould. Antimicrobials that occur naturally in nature have a number of advantages, as they are considered to pose less risk to the consumer. One of the modern directions in research is the inclusion of different types of active substances in the packaging material, which can give it additional functions, such as elimination of oxygen, moisture, ethylene, ethanol emission, antimicrobial activity and others. The present work aims to obtain plant extracts, their characterization and their surface application on paper. Extracts of Bulgarian herbs St. John’s wort, cumin, rosemary, thyme and basil were obtained and characterized and studied. Plant extracts are applied by spraying on the surface of various papers. The antimicrobial effect of treated papers on gram-positive and gram-negative bacteria was studied. The results of the analysis of the obtained papers show the possibility of using plant extracts containing biologically active ingredients for the production of papers with barrier properties. The use of plant extracts is a promising and innovative solution.Item SPECTROSCOPIC TECHNIQUE FOR STUDYING THE CHARACTERISTICS OF PAPER, PIGMENTS AND INKS IN THE AGING PROCESS (REVIEW)(2022-01-01) Ivanova L.; Spiridonov I.; Lasheva V.For many centuries paper has been the mainstay material for recording cultural achievements around the world. Paper is produced mainly from cellulose with small amounts of organic and inorganic additives, which allow its identification and characterization and can contribute to the decomposition of the paper. Spectroscopic technique is a powerful tool for examining the constituent elements of paper documents to establish their identification and their state of degradation. This review describes the application of selected spectroscopic technique used to characterize paper and inks. Spectroscopic technique that has been reviewed include: Infrared spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray fluorescence analysis, Inductively Coupled Plasma Mass Spectrometry, SEM-EDX, energy dispersion X-ray fluorescence.Item THERMAL STABILITY OF PACKAGING PAPERS TREATED OF SILVER WATER(2022-01-01) Yavorov N.; Todorova D.; Brodnjak U.V.; Lasheva V.Paper aging depends on the type and chemical composition of the fiber raw materials, the chemical additives used, such as dyes, fillers, sizing additives, pH and others as storage conditions of the paper (relative humidity and temperature) and the degree of exposure of temperature, light and some microbiological factors. The durability of paper is its ability to retain certain physic-mechanical, optical and chemical properties unchanged over time. In this context and in line with the increased consumption of coated or treated printing and packaging papers, the aging resistance of treated or coated paper is of a great scientific, research and applied interest. This research work inherently involves preparation and properties evaluation of thermal stability of packaging papers treated of silver water. In order to examine this process for woodfree packaging paper, accelerated thermal aging for 72h at temperature of 105°C and dynamic thermogravimetric analysis (TGA) was carried out of a pulp sample and four paper samples (three of them treated with silver water – 1, 2 and 3 ml) together with the structural-dimensional and strength properties of the laboratory obtained paper samples. The degree of colour changes in the CIELab colour space have been studied, bearing in mind that the changes in colour characteristics define the stability over time and even more – the influence of the silver water treatment. As a result of the studies carried out it was found out that paper do not change significantly during 72h of accelerated thermal ageing, but it is not recommended to be used more than 2 ml of silver water, as silver ions probably catalyze the aging process and the paper darkens and turns yellow in a greater degree. The change of the weight of the paper samples as a function of temperature was monitored by TGA. When comparing the weight losses, it was found out that for the paper sample treated with 2 ml of silver water the temperature of complete burning of the sample increased by 2.28°C. In addition, the surface of the treated paper samples is more even compared to the untreated due to the callandering effect of the manufacturing process.