Journal on Processing and Energy in Agriculture 19 (2015) 4 193 Biblid: 1821-4487 (2015) 19; 4; p 193-196 Original Scientific Paper UDK: 579:5832.794 Originalni naučni rad THE CHANGE IN MICROBIOLOGICAL PROFILE AND WATER ACTIVITY DUE TO THE OSMOTIC TREATMENT OF CELERY LEAVES AND ROOT PROMENA MIKROBIOLOŠKOG PROFILA I AKTIVNOSTI VODE USLED OSMOTSKOG TRETMANA LIŠĆA I KORENA CELERA Milica NIĆETIN * , Biljana LONČAR * , Vladimir FILIPOVIĆ * , Violeta KNEŽEVIĆ * , Tatjana KULJANIN * , Lato PEZO ** , Dragana PLAVŠIĆ *** * University of Novi Sad, Faculty of Technology, Bulevar cara Lazara 1, 21000 Novi Sad, Serbia, ** University of Beograd, Institute of General and Physical Chemistry, Studentski trg 12-16, 11000 Beograd, Serbia *** University of Novi Sad, Institute for Food Technology, 21000 Novi Sad, Bulevar cara Lazara 1, Serbia e-mail address: milican85@live.com ABSTRACT The aim of this study was to investigate effects of osmotic treatment on microbiological profile and water activity (a w ) in celery leaves and root, in order to indicate the usefulness of this drying technique. Samples of celery leaves and root were dehydrated in sugar beet molasses and aqueous solution of sodium chloride and sucrose, at three different temperatures. a w values of processed celery leaves and root were determined and the change of the microbiological profile between the dehydrated celery leaves and root was examined. The process of osmotic treatment improve the initial microbiological profile due to increasing dry matter content and lowering a w value of the all processed celery samples. Better microbiological load reduction was observed in samples of leaves compared with samples of roots. Measuring results were fitted to mathematical models using Response Surface Methodology and statistically evaluated using analysis of variance. Key words: Osmotic treatment, celery leaves and root, sugar beet molasses, microbiological profile. REZIME Ovo istraživanje, sprovedeno je sa ciljem da se ispita uticaj osmotskog tretmana na mikrobiološki profil i aktivnost vode (a w ), lišća i korena celera, kako bi se ukazalo na korisnost ove tehnike sušenja. Uzorci lišća i korena celera su dehidrirani u melasi šećerne repe i vodenom rastvoru natrijum hlorida i saharoze, pripremljenom korišćenjem saharoze u količini od 1200 g/kg vode, NaCl u količini od 350 g/kg vode (ternarni rastvor), na tri različite temperature (20 o C, 35 o C and 50 o C), nakon 1, 3 i 5 sati. Izmerene su a w vrednosti tretiranih uzoraka lišća i korena celera, a analizirane su promene u mikrobiološkom profilu između dehidriranih uzoraka lišća i korena celera. Uočeno je da proces osmotske dehidratacije ne uzrokuje pogoršanje inicijalnog mikrobiološkog profila lišća i korena celera, već ga naprotiv poboljšava, usled povećanja sadržaja suve materije i snižavanja a w vrednosti, kod svih dehidriranih uzoraka celera. Zapaženo je smanjenje mikrobiološkog opterećenja u svim tretiranim uzorcima celera. Bolji rezultati u smislu redukcije prisutnih mikroorganizama, dobijeni su nakon osmotskog tretmana u melasi, na višim temperaturama i nakon dužeg vremena imerzije, kako za lišće, tako i za koren celera. Redukcija mikrobiološkog opterećenja više je izražena u uzorcima lišća celera, u odnosu na uzorke korena. Rezultati su obrađeni regresionom analizom na razvijenim matematičkim modelima upotrebom metode odzivne funkcije, a statistička procena je urađena pomoću analize varijanse. Ključne reči: Osmotski tretman, lišće i koren celera, mikrobiološki profil, melasa šećerne repe. INTRODUCTION Celery leaves and root are a rich source of proteins, fats, vitamins, minerals and many bioactive components, therefore are widely used in human diet as a healthy vegetable and spice (Ponjičan et al., 2013). High water content (more than 80 %) in celery is the main cause of the relatively rapid perishable or damaging changes of the sensory and nutritive characteristics. To enhance the sustainability of celery, it is desirable to apply the appropriate method of drying (Ježek et al., 2008). The application of osmotic treatment (OT) at mild temperature in food preservation has many advantages as compared to traditional drying treatments. Celery is not exposed to high temperatures, minimizing, in that way, sensory characteristics changes, and preserving nutritional values of the fresh celery: vitamins, minerals, etc. Furthermore, OT is environmentally acceptable and energy efficient process due to the low temperature and energy requirements and low waste material (Ratti, 2009). OT process represents partial removal of water from food (fruit, vegetable, meat), which is performed by immersing them in various hypertonic solution (Koprivica et al., 2010). Mass transfer mechanism and quality of final product are affected by many factors such as composition and concentration of osmotic agents, immersion time of the product in the solution, agitation /circulation of osmotic solution, operating temperature, solution to sample ratio, nature and thickness of food material (Ćurčić et al., 2013). Concentrated sucrose solution, sodium chloride solutions and their combinations are usually used as hypertonic solution (Mišljenović et al., 2010). Previous research of Lević at al. (2007) was shown good behavior of molasses as hypertonic solution in OT. High content of solids (around 80 %) provide high osmotic pressure in the solution and allows greater loss of water during OT , enhances, on that way, the efficiency of this process. On the other hand, specific chemical composition of molasses (over 200 nutritional valuable compounds) enriches chemical and nutritional composition of dehydrated products (Filipović et al., 2012, Ćurčić et al., 2013). By OT initial microbiological profile of the celery root and leaves should be improved due to increasing dry matter content and lowered a w value of the treated samples (Filipović et al., 2012). The objective in this study was to investigate the influence of immersion time, temperature of the process and the type of