CC BY
3521. Oka S. Mechanism of Antimicrobial effect of various food preservatives. In: Molin, N., Ed. Microbial Inhibitors in Food, The Fourth International Symposium of Food Microbiology. Stockholm, Sweden, Almqvist & Wiksell, 1964; pp. 3-16.
22. Hirasa K and Takemasa M. Spice science and technology. New York, Marcel Dekker Inc., 1998.
23. Kim J, Marshall MR and Wei C. Antibacterial activity of some essential oil components against five foodborne pathogens. Journal of Agricultural and Food Chemistry, 1995; 43 (11): 2839-45.
24. Juven BJ, Kanner J, Schved F and Weisslowicz H. Factors that interact with the antibacterial action of thyme essential oil and its active constituents. Journal of Applied Bacteriology, 1994; 76: 626-31.
25. Sikkema J, de Bont JAM and Poolman B. Mechanism of membrane toxicity of hydrocarbons. Microbiological Reviews, 1995; 59(2): 201-22.
26. Wilkins KM and Board RG. Natural Antimicrobial Systems. In: Gould, G.W., Ed. Mechanisms of Action of Food Preservation Procedures. London, Elsevier, 1989; pp. 285.
27. Ram Kumar P and Pranay J. Comparative studies on the antimicrobial activity of black pepper (Piper nigrum) and turmeric (Curcuma longa) extracts. International Journal of Applied Biology and Pharmaceutical Technology, 2010; 1(2): 491-501.
28. Ali MA, Alam NM, Yeasmin MS, Khan AMM and Sayeed A. Antimicrobial screening of different extracts of Piper longum Linn. Research Journal of Agriculture and Biological Sciences, 2007; 3: 852-57.
29. Erturk O. Antibacterial and antifungal activity of ethanolic extracts from eleven spice plants. International journal of Biologia, Bratislava, 2006; 61(3): 275-8.
NEW PRODUCT FROM BULGARIAN ROSE
1Nenov N, 2Atanasova T, 3Gochev V, 2Merdzhanov P., 3Girova T, 2Djurkov T, 2Stoyanova A.
1 Department of Heating Technology, University of Food Technologies,
26 Maritza Blvd, 4002 Plovdiv, Bulgaria 2 Department of Sugar, Tobacco and Essential Oils, University of Food Technologies,
26 Maritza Blvd, 4002 Plovdiv, Bulgaria 3 Department of Biochemistry and microbiology, Plovdiv University "Paisii Hilendarski",
24 Tzar Asen str., Plovdiv 4000, Bulgaria
Abstract: The chemical composition of extract from rosa (Rosa damascena Mill.) by extraction with tetrafluoroethane was analyzed using GC and GC/MS. The main compounds (concentration higher than 3%) of extract were: phenylethyl alcohol (59.08%) and citronellol (12.31%).
Keywords: Rosa damascena, extraction, tetrafluoroethane
Introduction. Bulgaria is known throughout the world as the land of the oleaginous rose (Rosa damascena Mill.). Oleaginous roses belong to the family Rosaceae, genus Rosa, subgenus Eurosa, section Gallicanae D.C. In Bulgaria, a number of difference roses are cultivated - Damask rose (R. damascena Mill.), White rose (R. alba L.) and a few others. Of commercial interest to the essential oil industry is only R. damascena Mill. The oleaginous rose was first introduced in Bulgaria during the 14th century and found most favorable growing conditions in the Eastern sub-Balkan valleys. The industrial processing of rose sets its beginning in the middle of 17th century. The former is considered as being the major type, while the latter occupies areas along the Sredna Gora ridge being more resistant to the less favorable soil and climatic conditions (Georgiev and Stoyanova, 2006).
The essential oil is deposited mostly in the petal leaves (about 93% of the total content of the flower) - in the cells of the epidermis and the parenchyma. The average oil content in the flowers is 0.035%, but varies among varieties from 0.009% to 0.062%. The composition of the essential oil is also influenced by the age of the plant or of the respective organ that is processed (Staikov et al. 1975b, 1975c). The climatic conditions both prior to rose-picking and during the picking period, for example, are crucial for the yield and the quality of the essential oil. This is the reason why during the rose-picking period from one and the same growing area different outcomes with respect to oil yield and oil quality are registered for each of the picking days or for shorter several day-periods The unification of the essential oils obtained during the whole rose-picking campaign, aimed at quality uniformity, is the step that secures the final type of rose oil, characteristic in its quality for the respective crop year and growing region (Georgiev and Stoyanova, 2006; Staikov et al., 1975a).
Traditional rose products are rose oil, rose water, concrete and absolute.
The essential oil is obtained from rose blossoms by water distillation. The oil which floats upon the water is separated by decantation and the oil is known as the "primary oil". The yield of this oil is derived (10 - 15%). The distillation waters are re-processed by distillation (cohobation) and the secondary rose oil is obtained (85 - 90% of total oil yield). The two fractions are then combined in their natural proportion and the Bulgarian type of rose oil is finally obtained.
The distillation waters after the cohobation are known as rose water.
Rose oil is an oily, clear liquid or a heterogeneous mass (at temperatures below 23°C), with yellow to yellow-green color and specific odor. Approximately 400 oil components have been identified. They are divided in two categories of substances: carriers and fixators of fragrance. The fragrance carriers comprise the liquid part of the oil, the so-called "eleoptene". The fragrance fixators are scentless and solid at room temperature. They constitute the solid fraction of the oil, the so-called "stearoptene". Eleoptene composes 75-92% of the oil, and stearoptene - 8-25%. About 62-77% terpene compounds are found in oil's composition: hydrocarbons (monoterpenes up to 2% and sesquiterpenes 3-5%), oxygen-containing derivatives (monoterpenes 64-71% and sesquiterpenes 0.52%), fatty hydrocarbons and their oxygen derivates (18-25%), phenylpropanoids (3-5%), and others (0.5-2%) (Georgiev and Stoyanova, 2006).
In the end of the picking campaign rose water containing about 0.2-1.2% essential oil is also obtained, which composition incorporates ethyl alcohol and phenylethyl alcohol (33% each), citronellol and geraniol (11% each), nerol (7%) (Georgiev and Stoyanova, 2006).
By extraction of rose blossoms with petroleum ether rose concrete is obtained in Bulgaria, the yield being 0.20-0.25%. Conrete's composition incorporates over 200 components, of which hydrocarbons, aldehydes, ketones, alcohols, esters, fatty acids, etc. (Georgiev and Stoyanova, 2006).
The absolute of rose is prepared from the concrete by extraction with alcohol. This extract is cooled to precipitate the waxes. Absolute's composition includes the components of the essential oil, with phenylethyl alcohol being the major ingredient (70%), followed in order by: citronellol (11 -12%), geraniol and nerol (2% each). Rose absolute contains fatty acids from the Ci0_28 homologous order (mainly C22 and C24), homologs belonging to the groups of substances found in rose wax, but dominated by lower molecular weight members. Polycyclic compounds are also identified - ursolic and other acids, the pentacyclic triterpenoid amyrin, p-sitosterol, sterol, etc. (Georgiev and Stoyanova, 2006).
The aromatic products obtained from rose blossoms - essential oil, concrete, absolute and rose water, are extensively applied in perfumery, cosmetics and medicine. They all have well-defined antimicrobial activity (Georgiev and Stoyanova, 2006).
Instead of above listed classical methods for production of aroma preparations from rose blossoms, in 2012, Bulgarian scientists applied new and nontraditional methods for obtaining the aromatic products based on the manipulation of pulsed electric fields (Dobreva et al., 2013; Tintchev et al., 2012), surfactant and maceration (Dobreva and Lambrev, 2011; Dobreva et al., 2011). Authors reported that these methods are unsuitable in industrial conditions, independently of higher yield of oil.
New perspective method for production of rose aromatic product is extraction with liquid gases. The installations for extraction with liquefied gases characterized with high working pressure (0.6 MPa when butane is used, 1.5 MPa when propane is used and 4-7 MPa when C02 is used) and increased capital investments are needed. There are one laboratory installations with liquefied C2H2F4, situated in University of Food Technologies in Plovdiv, and two industrial working with liquefied C02
and one with liquefied C2H2F4 These installations are used for processing of different essential oil bearing plants in Bulgaria, for example lavender, coriander, fennel and etc.
In this paper we showed also the possibility for obtaining the rose aromatic products by extraction with liquid C2H2F4.
The aim of present study is producing of new plant extracts from rose growing in Bulgaria, by using liquefied gas (1,1,1,2-tetrafluorethane) in laboratory installation and determination of their chemical composition and characteristics for possible application in cosmetics products.
Materials and methods. The rose flowers were harvested in 2014 in the vicinity of the town of Karlovo, Bulgaria.
The conditions of the extraction are following: The extract obtained by a 1 dm3 volume C2H2F4 (1,1,1,2-tetrafluorethane) laboratory-extractor under temperature 20 - 25oC, pressure 5,7 - 6,5 bar and time 90 min.
The physical-chemical properties of extract were measured according to ISO 9842:2006. GC analysis was performed using gas chromatograph Agilent 7890A; column HP-5 ms (30m x 250^,m x 0.25^,m); temperature: 35oC/3 min, 5oC/min to 250oC for 3min, total 49min; carrier gas helium 1ml/min constant speed; split ratio 30:1. GC/MS analysis was carried out on a mass spectrometer Agilent 5975C, carrier gas helium, column and temperature as the same as the GC analysis. The identification of chemical compounds is made by comparison to their relative retention time and library data. The identified components are arranged in order to the retention time and quantity in percentage.
Antimicrobial activity of extract was determined against pathogenic and spoilage bacteria and yeasts from clinical and food isolates and also against reference strains, which are deposited in the microbial culture collection of Department of Biochemistry and microbiology, "Paisii Hilendarski" University of Plovdiv, Bulgaria. Minimal Inhibitory Concentration (MIC, ^g/ml) and Minimal Bactericidal Concentration (MBC, ^g/ml) of extract were determined by reference methods for broth dilution antimicrobial susceptibility tests for bacteria that grow aerobically and reference method for broth dilution antifungal susceptibility testing of yeasts (National Committee Clinical Laboratory Standards, 1990).
Results and Discussions. The produced extract is liquids with characteristic odor. The yield and some of physical and chemical characteristics are following: yield - 1.2 - 1.5% (w/w); appearance - light yellow solid, liquid bellow 20 - 22 OC; dry substance - 20.5% (105oC); refractive index (n D) -1.4800; acid value (mg KOH/g extract) - 1.2. As seen the results for the yields of extract is comparable with literature data and values of the physical and chemical characteristics of the extract are almost equal with these for the absolute.
Chemical composition of the extract is listed in Table 1. As seen 25 components representing 93.90% of the total content were identified. Eight of them were in concentrations over 1 % and the rest 17 constituents were in concentrations under 1%. The main compounds (concentration higher than 3%) of extract were: phenylethyl alcohol (59.08%) and citronellol (12.31%). According to qualitative and quantitative content of the major constituents the produced extract is equal to the rose absolute, published by above listed authors.
Distribution of major groups of aroma substances in the extract is shown in Figure 1. Phenylpropanoids are the dominant group in the extract, followed by oxygen monoterpenes and aliphatic hydrocarbons.
%
80 -|-
70----
60---
50---
40---
30---
20------ -
10--- -
0 -I-—-1---1-—-1---1--
1 2 3 4 5
Fig. 1. Group of components in the extract, %. 1- monoterpene hydrocarbons (1.09%), 2 - oxygen monoterpenes (16.55%), 3 - sesquiterpene hydrocarbons (0.95%), 4 - phenylpropanoids (67.45%), 7 - aliphatic hydrocarbons (13.96%).
Table 1. Chemical composition of rose extract.
№ Compounds RI %
1. a-Pinene 939 0.35
2. P-Pinene 979 0.41
3. Limonene 1029 0.26
4. Eucalyptol 1031 0.33
5. Phenylethyl alcohol 1107 59.08
6. (R)-(+)-Citronellal 1145 0.49
7. beta-Citronellol 1226 12.31
8. beta-Citral 1238 0.46
9. trans-Geraniol 1253 0.43
10. Phenethyl acetate 1259 2.59
11. alfa-Citral 1267 0.43
12. Citronellyl acetate 1353 0.21
13. Eugenol 1359 1.32
14. Geranyl acetate 1381 0.88
15. Methyleugenol 1404 0.35
16. beta-Caryophyllene 1425 0.89
17. n-Pentadecane 1500 0.47
18. n-Heptadecane 1700 0.34
19. (9E)-9-Nonadecene 1878 2.05
20. n-Nonadecane 1900 3.52
21. n-Eicosane 2000 0.64
22. (9E)-9-Icosene 2017 0.80
23. n-Heneicosane 2100 2.18
24. n-Tricosane 2300 0.44
25. n-Tetracosanol-1 2690 2.67
According to qualitative and quantitative content of the major constituents the produced extract is equal to the rose absolute (Table 2).
The results of antimicrobial testing are presented in Table 3. The studied rose extract demonstrated antibacterial activity against used test bacterial cultures, with the exception of both species belonging to the genus Pseudomonas tested by Agar Disc Diffusion Test. Probably it is due either to the diffusion limitations into the agar medium or to the increased resistance of these bacterial species. It is well known that Serial Broth Dillution Method is more reliable and reproducible and overcome the disadvantages of the Agar Diffusion Method. For these reasons it was applied parallel to the diffusion test. The results obtained by both methods shown that Gram-positive bacteria belonging to the species Bacillus and Staphylococcus are more sensitive in comparison with Gram-negative species Citrobacter, Escherichia and Pseudomonas.
Table 2. Comparative chemical composition of rose aromatic products
Compounds, extract with C2H2F4 essential oil absolute
% ISO 9842:2006 17381-96 (H-65)
Phenylethyl alcohol 59.08 max 3.5 45.0 -71.0
Citronellol 12.31 20.0 - 34.0 6.0 - 12.0
Nerol 0.43 5.0 - 12.0 1.5 - 6.5
Geraniol - 15.0 - 22.0 2.5 - 7.5
Eugenol 1.32 - 0.9 - 2.2
Methyleugenol 0.35 - 0.3 - 0.8
n-Heptadecane 0.34 1.0 - 2.5 -
n-Nonadecane 3.52 8.0 - 15.0 -
n-Heneicosane 2.18 3.0 -5.5 -
Probably the so called "external membrane" which is typical for the Gram-negative bacteria deteriorated the diffusion of the extract from the nutritive medium trough the cell wall and membrane into the cytoplasma.
Table 3: Antimicrobial activity of rose extract
Test microorganisms Origin Rose extract
IZ, mm MIC, ^g/ml MBC, ^g/ml
B. cereus ATCC 11778 15 512 512
C. diverus Clinical isolate 12 1024 1024
E. coli ATCC 8739 12 1024 1024
E. coli Food isolate 12 1024 1024
P. aeruginosa ATCC 9627 0 1024 2048
P. aeruginosa Clinical isolate 0 1024 2048
P. fluorescens Food isolate 0 1024 2048
S. abony Clinical isolate 10 1024 1024
S. abony ATCC 6017 10 1024 1024
S. aureus ATCC 6538 12 512 512
S. aureus Food isolate 14 512 512
S. epidermidis Clinical isolate 14 512 512
C. albicans ATCC 10231 12 512 512
C. albicans Clinical isolate 10 512 512
C. glabrata ATCC 90030 9 1024 1024
C. glabrata Clinical isolate 9 1024 1024
The rose extract also demonstrated antimicrobial activity against three species of medically important yeasts belonging to genus Candida. Non albicans candida (NAC) species C. glabrata are more resistible in comparison with C. albicans. The antimicrobial activity of rose extract is equal to the traditional aromatic products from rose, published by above listed authors.
Conclusion. For the first time in Bulgaria new extract from rose (Rosa damascena Mill.) was produced by extraction with tetrafluoroethane. This method is suitable for industrial production of absolute, because it is energy saving and also the obtaining of absolute and application of dangerous and combustible solvents is suspended.
The produced extract was almost quantitative and quality identical with absolute from the rose flowers, according to its chemical composition and antimicrobial activity. The extract is prospective for possible application in cosmetics products.
REFERENCES
1. Bulgarian State Standart 17381- 96 H-65. Concrete and Absolute of rose. pp 8.
2. Georgiev, E., and Stoyanova, A. (2006). A guide for the specialist in aromatic industry, Plovdiv.
3. Dobreva, A., and Lambrev, H. (2011). Application of Tween 80, Tween 85 and Cremophor RH 40 by distillation of Rosa damascena Mill. Science and Technologies. Plant studies, 1, 39-43.
4. Dobreva, A., Kovatcheva, N., Astatkie, T., and Zheljazkov, V. (2011). Improvement of essential oil yield of oil-bearing (Rosa damascena Mill.) due to surfactant and maceration. Industrial Crops and Products, 34, 1649-1651.
5. Dobreva, A. (2013). Dynamics of the headspace chemical components of Rosa damascena Mill. flowers. TEOP, 16, 404-411.
6. Dobreva, A., Tintchev, P., Dzhurmanski, A., and Toepfl S. (2013). Effect of pulsed electric fields on distillation of essential oil crops. Comptes rendus de l'Acad'emie bulgare des Sciences, 66, 1255-1260.
7. Irinchev, .I, and Delev, P. (1965). The significance of cohobation in the production of rose and other essential oils. Bulletin for the Development in the Essential Oil Industry, 3, 16-35.
8. ISO 9842:2006. Oil of rose (Rosa x damascena Miller). pp 12.
9. National Committee Clinical Laboratory Standards (1990). Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. Approved Standard. NCCLS Publication M7-A2. Villanova. PA. USA.
10. Nenov, N., Dichev, S., and Atanasova, T. (2008). Efficient method for obtaining high quality natural additives for foods, cosmetic and medicinal preparation by liquefied gas extraction,
Food and Flavour Industry, 2, 40-42.
11. Staikov, V., Balinova-Tzvetkova, A., Decheva, R., and Kalaidjiev I. (1975a). Rose flower storage conditions and quality of rose oil. Rivista Italiana EPPOS, 57, 176-180.
12. Staikov, V, Decheva, R, and Balinova-Tzvetkova, A. (1975b). Studies on the composition of rose oil obtained from the flowers in different stages of their development. Rivista Italiana EPPOS, 57, 192-195.
13. Staikov, V., Decheva, R., and Balinova-Tsvetkova, A. (1975c). Studies on composition of rose oil obtained from the flowers in different stages of their development. Rivista Italiana EPPOS, 57, 192-195.
14. Tintchev, P., Dobreva, A., Schulz, H., and Toepfl, S. (2012). Effect of pulsed electric fields on yield and chemical composition of rose oil (Rosa damascena Mill.). Journal of Essential Oil Bearing Plants, 15, 876-884.
BEARING CAPACITY FOR RECTANGULAR REINFORCED CONCRETE SECTIONS, SUBJECTED TO BIAXIAL BENDING AND ALL-SIDED FIRE EXPOSURE ACCORDING METHOD „ISOTHERM 500°C" IN BDS EN 1992-1-2
Neshev Hristian
PhD Student University of Architecture, Civil engineering and Geodesy, Sofia, BulgariaDepartment of Reinforced Concrete Structures
Abstract. Based on the presented simplified calculation method „Isotherm 500°C" in BDS EN 1992-1-2 is a composed procedure for determining the fire resistance of reinforced concrete rectangular sections of columns, subject of all-sided fire exposure. Conclusions and recommendations are made for practical application.
Keywords: fire resistance of reinforced concrete columns
1. Introduction. Reinforced concrete columns are loaded to biaxial bending when unbalanced moments of floor structure are transmitted on the main axes, when eccentrically loads in two mutually perpendicular directions of beams are footing, when asymmetrical section is changing, and when is taking into account the effect of imperfections and second order effects for each direction of the element. The determination of stress distributions is considerably more complicated than uniaxial bending. In fire exposure on all sides the bearing capacity of section compounded determining. Usually, in practice, these sections civil engineer reinforcing with symmetrical rebar located around the perimeter of the section.
2. Calculation of rectangular concrete sections subjected to biaxial bending and all-sided fire exposure. Coefficient of thermal expansion of cement and aggregates are different and arise considerable stress, disruption of adhesion, and formation of cracks in the concrete structure. The temperature in element is changing from directly heated surface towards the center of the cross-section, which leads to irregularly deformation and occurrence of internal stresses. As a result of physical and chemical changes, chemical processes and nonuniformity thermal expansion, rapid heating and temperature rise in reinforced concrete element arise temperature stresses. They lead to partial or complete cracking of reinforced concrete columns. The strength properties of concrete from the exposed surface to the inside in the section decreased. Based on this phenomenon, there has been a developed method, "Isotherm 500°C" [1], which is based on the hypothesis that concrete with temperatures higher than 500°C is neglected in the calculation of load-bearing capacity, while concrete with temperatures below 500°C is assumed to retain its full strength. The thickness of the damaged concrete a500 is determined by the average depth of the 500°C Isotherm, using temperature profiles given in Annex A of [1] or other specialized literature.
In the methodology for calculation of rectangular cross-sections of concrete columns, subjected to biaxial bending and all-sided fire exposure, for determining characteristic value of yield
