Purpose: The purpose of this study was (i) to evaluate the transfer and cross contamination of Salmonella, and (ii) to evaluate the process of cleaning of wood and plastic crates used for tomato transportation in Central America.
Methods: Salmonella Poona and Salmonella Typhymurium strains were used to inoculate tomatoes at 7.0 log CFU/tomato. Ten inoculated tomatoes were passed on clean plastic and wood crates, followed by passing ten uninoculated tomatoes on the contaminated surfaces. Transfer coefficients were determined by estimating log CFU/tomato of Salmonella recovery from uninoculated tomatoes. For the sanitation, two treatments of cleaning were applied on inoculated crates with E. coli: washing with water and washing with chlorine solution (200 ppm) and detergent. Transference coefficient between plastic and wood crates was compared using t-test, and efficiency of washing treatments was compared by ANOVA. Significant differences among treatments were determined by Duncan test at significant level of 0.05.
Results: Cross-contamination of tomato at levels of 2.5 log CFU/tomato occurred on both type of surfaces. There was not significant difference between transfer coefficients on wood or plastic crates (P > 0.05). Sanitation with chlorine solution showed E. coli reduction of 99.999% in plastic crates and 98.38% in wood crates (P < 0.05).
Significance: Regardless the material of crates, both materials may suffer cross contamination. It is strongly recommended to substitute the use of wood for plastic crates and perform correct Standard Sanitation Operating Procedures to reduce risk contamination of fresh produce.