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A10-P: ANTIMICROBIAL PROPERTIES OF FUNCTIONAL FOOD PRESERVATIVES
IN FRESH BASIL-BASED "PESTO" SPREADS

D. Mitić-Ćulafić (1), M. Pavlović (2), T. Lukić (1), S. Ostojić (1), J. Gvozdenović (3)

1 Faculty of Biology, University of Belgrade, Studentski trg 3/II,  Belgrade, Serbia

2 Institute of General and Physical Chemistry,  Studentski trg 12/V,  Belgrade, Serbia

3 Faculty of Technology, Bul. Cara Lazara 1, Novi Sad, Serbia

 

In order to increase food safety, new approaches, such as using bacteriocines [1], eukaryotic antibacterial proteins [2] and natural humectants [3] to control pathogenic and spoilage microorganisms and produce beneficial effects on organism [2, 4], have been developed. Fresh basil-based spreads, similar to “pesto”, an Italian pasta sauce, is limited to the very short shelf life. The main contaminants in pesto are yeasts, moulds, Bacillus sp. and Clostridium sp. The microbiological stability of pesto sauce is usually obtained by lowering the pH value at about 4.5 to inhibit the growth of Clostridium botulinum  and applying pasteurisation to reduce bacterial population, which lead to organoleptic degradation. Water activity (aw) is, also, an important factor affecting pesto stability [2]. The aim of our research was to reduce microbial load in basil-based spreads with addition of natural preservatives, avoiding thermal treatment. We have tested natural biopreservatives: lactoferrin, the main iron-binding protein in mammaliian milk, which  has antimicrobial activity against a wide range of Gram-positive and Gram–negative bacteria and yeasts [2], bacteriocin nisin, which is bactericidal aganst broad range of Gram-positive bacteria and inhibit outgrowth of germinating spores [1] and natural poliol xylitol, which is humectant and has antibacterial effects [5]. Combinations of nisin, lactoferrine and xylitol were tested against Staphylococcus aureus, Listeria innocua, Bacillus sp., Lactobacillus sp. and Pseudomonas aeruginosa.  Antibacterial effect of nisin, lactoferrine and xylitol was examined by well-diffusion test, with overnight bacterial cultures prepared in LB medium at 37° C. Microbiological analysis were done after varying periods of storage of  basil-based spreads (pH value 5.2 – 4.4)  at 4oC, containing different concentration of lactoferrin, nisin and xylitol. A total number of bacteria and yeasts in the products were determined by the pour-plate method using appropriate media. Different concentrations of nisin and nisin/lactoferrin showed strong antibacterial effect against S.aureus, L. innocua, Bacillus sp., and P. aeruginosa. Antimicrobial effect of xylitol in well-diffusion test was not detected against all tested bacteria. Also, Lactobacillus sp. bacteria were resistant to all tested substances. When nisin (150 mg/g) was added in pesto spreads, the counts of bacteria were 10 fold decreased after 15 days. Addition of xylitol (2-4 %) in pesto spreads resulted in 4 to 8 fold decrease in total number of bacteria, after the same period while water activity decreased from 0.882 to 0.870 - 0.863. Therefore, we propose that reduction of aw is responsible for the antibacterial effect of xylitol. Our findings suggest a potential application of low concentration of lactoferrine or xylitol and bacteriocines, in preservation of minimally processed food.

References

1. E. Chollet, A. Martial-Gros, P. Degraeve, Food Control, 2008, 19, 982-989.
2. A. S. Naidu, Food Technol., 2002, 56, 40-45.
3. C. Severini, M. R.Corbo, A. Derossi, A. Bevilacqua,  R. Giuliani,  Int. J. Food Science Technology, 2008, 43, 1041-1046.
4. F. Brouns, C.Vermeer,  Food Science & Technology, 2000,  11, 22-23. 
5. T.T. Tapiainen, T.Kontiokari, L. Sammalkivi, I. Ikaheimo, M. Koskela, M. Uhari, Antimicrobial Agents and Chemotherapy, 2001,  45, 166-169.
6. V. Mota da Silva,  L . Almeida Silva., J.B. de Andrade, Quim. Nova, 2008, 31, 901-905.