Taimsete lisandite antibakteriaalne toime valitud bakteritele
Käesoleva uurimistöö eesmärgiks oli välja selgitada taimsete lisandite antibakteriaalne toime valitud bakteritele. Taimsetest lisanditest uuriti rabarberit (varred, juur), must sõstart (mari, leht), aroonia marja ja söödava kuslapuu marja ning tunnusainetest resveratrooli, emodiini ja rapontiini. Uurimistöösse valiti järgmised bakterkultuurid: Campylobacter jejuni, Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli, Bacillus cereus, Yersinia ruckeri, Kocuria rhizophila, Bacillus subtilis ja Bacillus pumilus. Tulemustes selgus, et in vitro uuringutes olid kõige efektiivsemad rabarberi juur "Dea Victoria" ja musta sõstra mari "Ben Alder" 96% etanoolis, sest omasid toimet kõigi üheksa testitud bakteri suhtes. Mõõdetud pidurdustsoonid jäid vahemikku vastavalt 11-18 mm ja 9-15 mm. Neile järgnesid tume rabarberi (nr. 303) juur ja võrse (pidurdustsoonid jäid vahemikku 8-20 mm) ning musta sõstra lehed "Pamjati Vavilova" (d=9-13 mm) ja aroonia marjad (d=8-15 mm), mis inhibeerisid vähemalt seitsme testitud bakteriliigi kasvu. Kõige efektiivsemateks taimseteks lisanditeks osutusid eraldi Gram-positiivsetele bakteritele 96% etanoolis tume rabarberi (nr. 303) juur ja 96% etanoolis rabarberi juur "Dea Victoria" ning eraldi Gram-negatiivsetele bakteritele 96% etanoolis tume rabarberi (nr. 303) juur ja võrse ning rabarberi juur "Dea Victoria". Sellest tulenevalt võime järeldada, et in vitro katseseeriates osutus kõige efektiivsemaks taimseks lisandiks rabarberi juur. Uurimistöö tulemustes selgus ka, et uuritud tunnusainetest emodiin ja resveratrool omasid antibakteriaalset mõju mõnede bakterite (C. jejuni (d=10-12 mm), S. Enteritidis’e (d=10-12 mm), L. monocytogenes’e (d=8 mm), E. coli (d=12 mm)) suhtes. Sellest järeldub, et neid tunnusaineid, mida leidub ka taimsetes lisandites, võib seostada antibakteriaalse toimega.Food-borne infections have been one of the major public health concerns worldwide and account for considerably high cases of illnesses attacking human. Growth of microorganisms in food may cause food spoilage or food-borne disease. For this reason, to avoid the growth of microorganisms in foods, synthetic additives are widely used, especially in animal-origin foods with longer shelf-life. For example nitrates and nitrites in processed meat products are used already very long time. Nitrite prevents the growth of a harmful bacterium called Clostridium botulinum and it may have preservation effects on the other harmful and spoilage bacteria. In addition, nitrite develops cured meat flavour and colour. Unfortunately, nitrites, which can form from nitrates, react with naturally occurring components of protein called amines, and this reaction can form nitrosamines, which are generally known as cancer-causing compounds. In recent years, there has been increased search for natural substances, especially of plant origin to replace or substitute the use of synthetic additives in foods. Indeed, herbal spices and other plants and berries have been found to be a promising source of phenolics, flavonoids, anthocyanins and carotenoids, are more intensively used to impart flavor and enhance the shelf-life of dishes and processed food products. The main aim of present study was to identify the antibacterial effect of certain plant additives on selected bacteria and to find good candidates for further research using meat matrix. Good candidates should have good functional properties to avoid or diminish the microbial growth in meat products and to give reasonable shelf-life. In this study, rhubarb (stalk, roots), black currant (berries, leaf), black chokeberry (berries), edible honeysuckle (berries) were selected to determine the antimicrobial characteristics. Additionally, the reference substances such as resveratrol, emodine and rhapontin that can be found in these plants were studied. Among all the bacterial species used in present study, the gram-positive bacteria were represented by Listeria monocytogenes, Bacillus spp. and Kocuria rhizophila. The Gram-negative bacteria were represented by Campylobacter jejuni, Salmonella, Escherichia coli and Yersinia ruckeri. As a result it was found that the rheum "Dea Victoria" roots and black currant berries "Ben Alder" in 96% ethanol solution had a higher antimicrobial activity against strains of all nine bacterial species tested in this research. Also, rheum "Dea Victoria" showed good antimicrobial activity against eight bacteria while dissolved in 20% ethanol solution. Among all the tested plants additives the highest inhibitory zone in average was determined for the dark rheum root in 96% ethanol solution (no. 303) and for rhubarb root "Dea Victoria" in 20% ethanol solution. The most effective plant additives against the gram-positive bacteria in the 96% ethanol were individually dark rhubarb (no. 303) root and rhubarb root "Dea Victoria". The most effective plant additives against the gram-negative bacteria in 96% ethanol were dark rhubarb (no 303) both root and a stalk and plant additives of a rhubarb root "Dea Victoria". The aforementioned results confirm that during the in vitro experimental series the most effective plant additives were found to be rhubarb roots ("Dea Victoria" and rhubarb no. 303). Taking this into account we believe that these rhubarbs could be investigated as a good functional ingredient candidates for using in meat products but more studies are necessary to assess the rhubarb root’s ability to inhibit growth of bacteria in vivo. Also, it was found that studied reference substances such as emodine and resveratrol had the antibacterial effect on the selected bacteria. The latter means that the reference agents, which are also found in the studied plant additives, can attribute an antimicrobial activity. However, it should be further chromatographically analyzed which kind of beneficial substances, additionally to the mentioned ones, studied plants may contain and in which combination and concentrations. Additionally, concentrations which have an effective antibacterial and antioxidant activity should be found with subsequent experiments.