Survival and growth of Salmonella Typhimurium, Escherichia coil O157: H7 and Staphylococcus aureus in eggplant dip during storage

Eggplant dip is an internationally popular appetizer, prepared in some instances under uncertain hygienic conditions with inconsistent refrigeration. This study examined the effects of citric acid on the survival of pathogenic microorganisms (Salmonella Typhimurium, Escherichia coil O157:H7 and Staphylococcus aureus) and naturally present organisms (lactic acid bacteria, LAB, aerobic bacteria, APC and yeast and mold, YM) in eggplant dip during storage. Eggplant dip with 0, 0.2,0.4, 0.6 or 0.8% citric acid was inoculated with S. Typhimurium, E. coil O157:H7 or S. aureus and stored at 4, 10 and 21 degrees C for <= 15 d. Throughout the study, the survival of the inoculated microorganisms was monitored, and LAB, APC, YM numbers and pH were determined. There was no significant (p > 0.05) effect of citric acid on inoculated S. Typhimurium and E. coil O157:H7. Salmonella and E. coli O157: H7 survived > 7 d with little reduction in viability. Reduction of S. aureus viability increased with citric add concentration and reached > 3.0 log(10) CFU/g by 15 d at 4 degrees C. Citric acid had no effect (p > 0.05) on the background YM during storage at 4, 10 and 21 degrees C or LAB stored at 4 and 10 degrees C, while at 21 degrees C, 0.6 and 0.8% citric acid significantly reduced LAB. Citric acid had no effect (p > 0.05) on the APC in samples stored at 4 degrees C but it had significant effects on samples stored at 10 and 21 degrees C. Work reported showed that the use of citric acid at 0.4-0.8% can inhibit the growth of S. aureus in eggplant dip, but adequate refrigeration is essential to minimize risk from this and other pathogens in this product. (C) 2014 Published by Elsevier B.V.