POLISH JOURNAL OF FOOD AND NUTRITION SCIENCES www.pan.olsztyn.pl/journal/ e-mail: joan@pan.olsztyn.pl © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences Pol. J. Food Nutr. Sci. 2009, Vol. 59, No. 1, pp. 61-66 INTRODUCTION Onion may be among the first cultivated crop in the world due to its prolonged storage time and portability. At this point in time, Allium family has over 500 members, each differing in colour and taste, but close in biochemical, phytochemical and neutraceutical contents [Topal 1989; Phay et al., 1999; Yin & Tsao, 1999; Benkeblia, 2004, 2005]. Onion aqueous extracts are effective against many yeast species and several G(+) bac- teria but ineffective against G(-) bacteria [Yin & Tsao, 1999; Benkeblia, 2004; Elnima et al., 1983; Zohri et al., 1995; Kivanc & Kunduhoglu, 1997; Ghahfarokhi-Shams et al., 2006]. Ali et al. [2000] reported that a strong antimicrobial (antibacterial) effect of fresh onion homogenates was due to both methyl- cysteine sulfoxide and S-n-propyl cysteine sulfoxide from which the corresponding thio-sulfinates are formed enzymati- cally [Phay et al., 1999; Kyung & Lee, 2001]. Alliums were concurred to possess antimicrobial activi- ties, and they contain numerous phenolic compounds beside of sulphurous compounds which arouse great interest [Yin & Tsao, 1999; Benkeblia, 2004; Elnima et al., 1983; Zohri et al., 1995; Kivanc & Kunduhoglu, 1997]. The flavonoids ex- hibit various antimicrobial activities [Puupponen-Pimia et al., 2001]. Earlier researches on the flavonoid content of onions (Allium cepa L.) have indicated that the main flavonoids are quercetin, quercetin-4’-glucoside, quercetin-3,4’-diglucoside, quercetin-7,4’-diglucoside and isorhamnetin glycoside [Fos- sen et al., 1998]. The researches show that Allium plant extracts as a natu- ral preservative, could be an alternative to synthetic antimi- crobial compounds in various industries. The use of plant parts and extractives helps in designing new drugs as thera- peutic agents or controlling food-related microorganisms [Thangadurai et al., 2004]. Onion is commonly used as spice in Turkey especially in ground beef, doner kebab (it is a popular meat product consumed widely in Turkey and in many countries), meat balls and raw meat balls-cig kofte (it is a traditional food which is consumed in Turkey, it is prepared by adding boiled and powdered wheat, onion, gar- lic, tomato sauce, parsley and different spices into ground meat); it may also be used to reduce pathogenic microor- ganisms whether they could be contaminated during unhy- gienic productions. The purpose of this study was to investigate the anti- bacterial and anticandidal activities of two forms of onions (white and red) against some pathogen bacteria and a yeast in vitro. Also basically, this study examines the effect of an- timicrobial activity of onion phenolic compounds which are present in red onion extracts and establishes whether antimi- crobial effects between the white and red onion varieties can be possible. MATERIALS AND METHODS Allium cepa samples Two varieties of onions (Allium cepa L., white and red), were selected for this research. Onions were cultivated in Erdek region of Turkey, during July 2007. The freshly harvested sam- ples were classified for homogeneity and lack of flaws and prepared for analyses. Author’s address for correspondence: Nurcan Degirmencioglu, Balikesir University, Vocational High School of Bandirma, 10200 Bandirma, Balikesir, Turkey; e-mail: dnurcan@balikesir.edu.tr SURVIVAL OF SOME MICROORGANISMS IN THE PRESENCE OF ONION (ALLIUM CEPA L.) EXTRACTS IN VITRO Nurcan Degirmencioglu 1 , Reyhan Irkin 2 1 Balikesir University, Vocational High School of Bandirma, 10200 Bandirma, Balikesir, Turkey; 2 Balikesir University, Vocational High School of Susurluk, 10600 Susurluk, Balikesir, Turkey Key words: antibacterial activity, anticandidal activity, Allium cepa, white onion, red onion By using disc diffusion assay, the antibacterial and anticandidal activities of extracts prepared from two varieties of onion (red and white) with water and different solvent extracts (ethyl alcohol, methyl alcohol, acetone and diethyl ether) at different concentrations (800, 400, 200 and 100 mg/ mL) were evaluated against six bacteria: Enterobacter aerogenes (ATCC 13048), Escherichia coli (ATCC 25922), Salmonella enteritidis (ATCC 13076), Salmonella typhimurium (ATCC 14028), Staphylococcus aureus ssp. aureus (ATCC 29213), Bacillus subtilis (test microorganism of sterilization) and one genus of yeast Candida albicans (ATCC 10231). The research clearly indicates that white Allium cepa (diethyl ether, water and methyl alcohol) and red Allium cepa (diethyl ether, methyl alcohol, water and acetone) extracts were inhibitory against the tested microorganisms. White Allium cepa extract of ethyl alcohol at 800 mg/mL dose was found to be able to inhibit Candida albicans and other extracts were definitely non-inhibitory (p<0.01).