Purpose: The purpose of this study was to evaluate the effectiveness of organic acids and saline solutions as antimicrobial treatments against Salmonella spp. and E. coli O157:H7, during wheat tempering.
Methods: To inoculate the wheat, cocktails were prepared using either five serotypes of S. enterica or five kanamycin-resistant strains of E. coli O157:H7. To prepare the inoculum, each strain/serotype was grown independently at 37°C for 24h, and mixed in equal proportions. Wheat was then inoculated to achieve a 5.0 log CFU/g, followed by a resting time (24h). Besides water, solutions containing acid (acetic or lactic - 2.5% or 5%) and salt (NaCl - 1%) were used for tempering (24h) the wheat. Samples were then plated before and after tempering on Tryptic Soy Agar (TSA) with an overlay of Xylose-Lysine-Tergitol 4 agar for S. enterica, and TSA+kanamycin (50μl/g) for E. coli and incubated (37°C for 24h). The log reduction in the pathogenic populations was calculated and differences in treatments compared using ANOVA.
Results: The initial load of pathogens was reduced significantly by all treatments when compared to the control which was tempered with water (P < 0.05). The best results for S. enterica and E. coli O157:H7 were achieved using lactic acid 5%+NaCl 1% solution, which resulted in 2.0 and 1.8 log reduction in CFU/g, respectively.
Significance: Implementation of organic acids and salt in tempering water prior to milling could benefit the milling industry and consumers by preventing or reducing the risk of microbial contamination in milled products.