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В системе NCBI в соответствии с данными, полученными при секвенировании генома B. avium был проведён in-silico анализ соответствия аннотированным протеомам - идентифицировано 5574 белка. Среди них были отобраны те, которые соответствовали бы молекулярному весу протеомов, полученных нами при электрофоретическом их разделении.
Выводы
В результате проведенных исследований нами были изучены основные биологические свойства бактерий вида Bordetella avium. Данный вид растет на средах для выделения возбудителя коклюша, таких как среда Борде- Жангу и Бордетелагаре, так и на среде для энтеробакерий, агаре МакКонки. Бактерии B.avium проявляют биохимические свойства характерные для представителей рода.
В результате проведенного исследования было проведено профилирование протеома B. avium, дана его биологическая характеристика по электрофореграмме и анализу in-silico.
По результатам проведенного анализа становится очевидным, что каждому из выявленных белков может соответствовать антиген. Таким образом, данное исследование может быть использовано в дальнейшей работе изучения антигенной структуры B. avium и разработке соответствующих серологических диагностикумов.
Список литературы
1.Мастиленко А. В., Минаева А. Н., Ломакин А. А. Основные ростовые характеристики бактерий вида Bordetella trematum //Вестник Ульяновской государственной сельскохозяйственной академии№ 2 (50), апрель-июнь 2020. - 2020.
2.Eldin W. F. S. et al. Prevalence, virulence attributes, and antibiogram of Bordetella avium isolated from turkeys in Egypt //Tropical Animal Health and Production. - 2020. - Т. 52. - №. 1. -С. 397-405.
3.Harrington A. T. et al. Isolation of Bordetella avium and novel Bordetella strain from patients with respiratory disease //Emerging infectious diseases. -2009. - Т. 15. - №. 1. - С. 72.
4.Kadlec K., Schwarz S. Antimicrobial resistance in Bordetella bronchiseptica //Antimicrobial Resistance in Bacteria from Livestock and Companion Animals. - 2018. - С. 365-375.
5.Kersters K. et al. Bordetella avium sp. nov., isolated from the respiratory tracts of turkeys and other birds //International Journal of Systematic and Evolutionary Microbiology. - 1984. - Т. 34. - №. 1. -С. 56-70.
6.McLaughlin K. et al. Biofilm formation and cellulose expression by Bordetella avium 197N, the causative agent of bordetellosis in birds and an opportunistic respiratory pathogen in humans //Research in microbiology. - 2017. - Т. 168. - №. 5. -С. 419-430.
ABOUT QUALITY OF PULSED ELECTRIC FIELDS PROCESSED MILK AND EGG PRODUCTS
Уразова Рано Станиславовна
Канд. биол. наук, доцент кафедры зоологии, Самаркандский государственный университет, Самарканд, Узбекистан
Rano Urazova
PhD in biology, associate professor, Department of Zoology, Samarkand State University,
Samarkand, Uzbekistan
ABSTRACT
The objective of this work was to review the quality of influence of pulsed electric field processed milk and egg products. The PEF-treatment as a nonthermal method, which allows to preserve the natural quality, color, and vitamin constituents of food products.This processing is based on electroplasmolysis phenomena. Applications of PEF in food processing are discussed.
Key words: pulsed electric field, electroplasmolysis, treatment chamber, high voltage application, milk, egg products.
Introduction
Amongst various non-thermal processing techniques used in food technologies, the pulsed electric field (PEF) treatment is one of the most perspective. It involves a short bump of high voltage application to a foodplaced between two electrodes. As high electric voltage isused, a large flux of electric current runs through food materials, which may act aselectrical conductors due to the presence of electrical charge carriers such as large concentration of ions (Barbosa-Cánovas et al. 1999).
In an attempt to improve, or replace, existing food processing methods, several novel technologies have been investigated. Some of these technologies, now known as "emerging technologies," have become, especially in highly competitive markets, a very interesting alternative for the food industry, as a means of developing new foods, or improving the safety and quality of existing ones, while reducing energy consumption.
PEF is a nonthermal food processing technology involving the application, to a food placed between two electrodes, of short duration high intensity electric fields. Such treatments cause, in cells, a phenomenon known as "electropermeabilization,'
Electropermeabilization is a temporary or permanent permeabilization of the cell membrane. This permeabilization has shown to have very useful effects in food technology such are the inactivation of microorganisms or the extraction of cell components.
In general, a PEF system consists of a high-voltage power source, an energystorage capacitor bank, a charging current limiting resistor, a switch to dischargeenergy from the capacitor across the food and a treatment chamber. The bank ofcapacitors is charged by a direct current power source obtained from amplified andrectified regular alternative current main source. An electrical switch is used todischarge energy (instantaneously in millionth of a second) stored in the capacitorstorage bank across the food held in the treatment chamber. Apart from those majorcomponents, some adjunct parts are also necessary. In case of continuous system apump is used to convey the food through the treatment chamber. A chamber coolingsystem may be used to diminish the ohmic heating effect and control food temperatureduring treatment. High-voltage and high-current probes are used to measure thevoltage and current delivered to the chamber.
The type of electrical field waveform applied is one of the importantdescriptive characteristics of a pulsed electric field treatment system. Theexponentially decaying or square waves are among the most common waveforms is used. To generate an exponentially decaying voltage wave, a DC power supplycharges the bank of capacitors that are connected in series with a charging resistor.When a trigger signal is applied, the charge stored in the capacitor flows through thefood in the treatment chamber. Exponential wave forms are easier to generate from thegenerator point of view. Generation of square wave form generally requires a pulse forming network (PFN) consisting of an array of capacitors and inductors. It is
more challenging to design a square wave form system compared to an exponentialwaveform system. However, square waveforms may be more lethal and energyefficient than exponentially decaying pulses since square pulses have longer peakvoltage duration compared to exponential pulses (Zhang et al. 1995). In order to produce effective square waveformusing a PFN, the resistance of the food must be matched with the impedance of the PFN. Therefore, it is important to determine the resistance of the food in order to treatthe food properly.
Application of PEF in food industry
Generally, applications ofPEF in food processing have been directed to two main categories: microbialinactivation and preservation of liquid foods, and enhancement of mass transfer and texture in solids and liquids.
Large portion of works on PEF have been focused on reducing microbial load in liquid or semi-solid foods in order to extend their shelf life and ensure their safety. These studies and others have reportedsuccessful PEF-inactivation of pathogenic and food spoilage microorganisms as well as selected enzymes, resulting in better retention of flavors and nutrients and fresher taste compared to heat pasteurized products (Barbosa-Cánovas et al. 1999).
Quality of PEF-processed foods
This section tries to summarize the information available about various quality parameters of PEF-processed foods, such as color, flavor retention, protein functionality, among others. Potential applications include mainly liquid or semisolid foods which can continuously flow between two electrodes. The use of PEF in solid foods has generally a different objective, which is not the production of a safe and stable food, but the extraction of components or acceleration of processes. Thus, this section is focused on the effects of PEF on constituents and quality parameters of liquid foods.
Milk
Milk was the first product proposed to be processed by PEF. Many studies have been focused on the inactivation of several pathogenic and spoilage microorganisms, as well as various enzymes of interest. Results regarding microbial inactivation clearly show that PEF could be an adequate alternative to heat pasteurization treatments, since it attains between 3 and 6 log cycles of destruction of most vegetative pathogenic species studied. Concerning enzyme deactivation, results are contradictory. Nevertheless, information available suggests that enzyme inactivation in milk is lower than in buffer systems, and that insufficient inactivation
of lipases and proteases could be expected. However, enzymatic activity of lipases and proteases, while is the most important factor determining shelf life of sterilized milks, play a minor role in pasteurized milk stability.
Although it is assumed that the small amount of heat generated during PEF should not cause detrimental changes in milk components and properties, little research effort has been done to prove it. There is a lack of documentation about the effect of PEF treatments
under different experimental conditions on milk constituents, and conclusions exposed in this section have been taken from scattered investigations.
Qin et al. (1995) suggested that milk could be processed at 40 kV/cm for 80 ^s, and a maximum temperature of 50 0C, rendering a product with a shelf life of 2 weeks in refrigeration. According to these authors, no apparent changes in the physical and chemical properties of milk were induced. Grahl and Mark described in 1996 that several vegetative cells could be effectively inactivated by PEF treatments while some components such as vitamin A and whey protein did not undergo changes. Sensory evaluations showed no deterioration of milk. However, experimental conditions were not detailed. The lack of effect of PEF on milk properties was confirmed by Michalac et al. (2003). These authors used a PEF treatment consisting of 188 ^s (bipolar pulses of 3 ^s length) at 35 kV/cm in a continuous bench scale system. Maximum temperature attained by processed milk was 52 0C. Color, particle size, total solids content, protein content, pH, electrical conductivity, viscosity, and density analysis showed no differences between PEF-treated and heat-pasteurized (73 0C/30 s) milk. However, reduction of the natural microflora of milk was greater in heat-pasteurization (2.7 log vs. 1 log).
Also, distribution of fat globules in milk and cream does not change with PEF treatment, as it has been discussed previously (Barsotti et al., 2002). Vitamins are also preserved after PEF treatments, except ascorbic acid, whose content decreases slightly (Bendicho et al., 2002b). Finally, structural studies on ß-lactoglobulin (Barsotti et al., 2002) also support the view that no major modifications are caused by PEF treatments in proteins of milk.
Egg Products
Egg products, liquid whole egg, egg white, or egg yolk, are normally heat-treated and distributed frozen, dehydrated, or refrigerated. Heat pasteurization is required to guarantee the inactivation of pathogenic microorganisms such as Salmonella, which are common contaminants of these foods. The effects of heat on egg constituents are especially harmful because egg products are used as ingredients in the manufacturing of many other foods, due to their foaming, emulsifying, and gelling properties, among others. Therefore, the maintenance of their functional quality, besides their microbiological quality, is essential. Most of the functional properties of egg and egg products rely on their proteins, which are especially thermosensitive. Thus, nonthermal methods that guarantee the microbiological safety and stability of egg and derivatives have been sought for years. PEF is one of the procedures that have been proposed. The first difficulty encountered for the application of PEF
treatments on egg and egg derivatives is the high conductivity of these foods. Most PEF equipments currently available require samples of low conductivity to obtain electric field strengths of high intensity, therefore some of the research works published have been performed with egg products with reduced salt content, through dialysis or ultrafiltration.
Most authors have reported no protein coagulation after different PEF treatments in liquid whole egg or egg white (Femandez-Dfaz et al., 2000; Ma et al., 2001). With regards to other quality parameters of egg and egg products, very little is known. Qin et al. (1995) reported that liquid whole egg with 0.15% citric acid processed at 35 kV/cm for 20 ^s and at a maximum temperature of 45 0C was preferred over a commercial brand in an acceptance test. Also, scrambled eggs prepared with PEF-treated were not distinguished from a control in a triangle test. Hermawan et al. (2004) did not detect significant changes in the viscosity, °Brix, and color parameters (L, a, and b), between untreated liquid whole egg controls and
samples treated by PEF (25 kV/cm, 250 us) plus a following heat treatment at 55 0C for 3.5 min. These treatment conditions were chosen to obtain a product with a long shelf life in refrigeration temperatures (more than 60 days) since PEF alone resulted insufficient. It is noteworthy that the combination of PEF processing with moderate heat treatments and/or antimicrobial substances has been suggested by various researchers as the most suitable alternative (Calderon-Miranda et al., 1999; Hermawan et al., 2004; Jeantet et al., 2004) to completely assure the safety of the product with regards to pathogenic microorganisms such as Salmonella or Listeria.
From these data, it can be concluded that PEF processing is unlike to cause any detrimental effect either on egg protein functionality or color, viscosity, flavor characteristics, proven treatments are carried out at low temperatures. However, information available is scarce and more research effort is needed to fully characterize possible changes in egg product treated by PEF, especially in combination with moderate heat treatments.
Conclusions
Pulsed electric field (PEF) treatment has a promising futurefor agro-food processing. The emerging and new technologies presented are at different stages of development with high hydrostaticpressure technology for food preservation and quality retention being the most advanced.
Pulsed electric field applications are on the verge of industrial use. It posses a great potential for food modification purposes and are generally more sustainabletechnologies than conventional thermal ones.
Fig. 1. Experimental setup
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