Surface Area Mapping and Rinse Procedures of Raw Produce to Determine Effectiveness of Pathogen Removal

Abstract

Bacterial pathogens on the surfaces of raw produce may be difficult to remove for identification and enumeration. The first part of this project examined whether ultrasonic treatment (40 kHz) of a rinse solution would enhance recovery of Salmonella spp. from various produce surfaces. Strawberries, apples, and cantaloupe were surface inoculated with a five-strain cocktail of nalidixic acid resistant Salmonella spp. Samples were subjected to one of six different treatments using different combinations of agitation methods (manual shaking or ultrasound), diluent temperatures (25°C and 40°C), and agitation times (60 and 120 seconds). After treatment, diluent was spiral plated onto tryptic soy agar supplemented with 50 ppm of nalidixic acid and plates were incubated at 37°C for 48 hours. Results from this study indicate that ultrasonic treatment of a rinse solution did not enhance or diminish recovery of Salmonella spp. from produce surfaces, as compared to manual agitation. The effects of diluent temperature and exposure time appeared to have a significant effect on recovery, depending on the type of produce.

The second part of this project used a computer imaging system to determine the surface area of various types of produce. The imaging system acquired and stored multiple images of the produce samples. From these images, surface fitting and approximation of a 3-D wire frame model were used to calculate surface area. From these measurements, it was determined that there were statistical relationships between surface area and weight. Surface area measurements were used to develop equations to predict surface area from weight measurements.