Denyse I. LeBlanc

Simulation of Escherichia coli O157:H7 behavior in fresh-cut lettuce under dynamic temperature conditions during distribution from processing to retail.

The temperature of packaged lettuce was recorded throughout a retail supply chain in Canada during the various stages of storage and shipping from the processor to retail. Temperatures were monitored in 27 cases of lettuce destined for three stores in three replicate trials conducted during the winter. A dynamic model that predicts the effect of temperature on the growth or die-off of Escherichia coli O157:H7 in packaged fresh-cut lettuce was applied to simulate the behavior of E. coli O157:H7 in the system. Simulations were carried out using distributions to account for variation in the temperature parameter and the die-off coefficient of the dynamic growth/death model. The results indicate that there was a predicted overall mean decline in cell numbers of 0.983 log cfu g⁻¹ and that the extent of cell death was proportional to the total time spent in the cold chain. Slight growth was predicted in a few instances when the dynamic temperature was above the permissive temperature of 5°C. These results suggest that generally there would be little or no growth of E. coli O157:H7 in product maintained at the proper temperature in the chain. Moreover, the predicted decline in cell numbers at refrigeration temperatures suggests that storage at 5°C or below prior to consumption would reduce populations of the pathogen in fresh-cut lettuce.

Invited review: Engineering aspects of physical treatments to increase fruit and vegetable phytochemical content

Vigneault, C., Leblanc, D. I., Goyette, B. and Jenni, S. 2012. Engineering aspects of physical treatments to increase fruit and vegetable phytochemical content. Can. J. Plant Sci. 92: 373–397. The levels of phytochemicals in fruit and vegetables are affected by many preharvest and postharvest factors, such as cultivars, farming practices, environmental conditions, harvest techniques, and postharvest handling and treatment. Postharvest factors are generally the easiest to manage since produce handling takes place mainly under controllable conditions. Although specific physical treatments, such as heat and ultraviolet radiation, have been developed to increase the phytochemical content of horticultural produce, very little information is available on the engineering aspects of these treatments. A review of the engineering aspects related to phytochemical-enhancing physical treatments was undertaken to identify the process parameters required to obtain repeatable results, the basic information required for scale-up of the process, and the key parameters required to ensure appropriate monitoring and control of commercial applications. The uniformity, efficiency, efficacy, ease of control and ease of scale-up of various physical treatments were compared to support the development of a new phytochemical-enhancing treatment for potential commercial application. These treatment methods were considered independently of the physical characteristics of the produce treated (type of produce, size, shape, and positioning) to reduce the number of parameters to be studied with a view to scale-up processes, following identification of the optimal processing conditions through laboratory-scale testing.

Spatio-temporal assessment of food safety risks in Canadian food distribution systems using GIS.

While the value of geographic information systems (GIS) is widely applied in public health there have been comparatively few examples of applications that extend to the assessment of risks in food distribution systems. GIS can provide decision makers with strong computing platforms for spatial data management, integration, analysis, querying and visualization. The present report addresses some spatio-analyses in a complex food distribution system and defines influence areas as travel time zones generated through road network analysis on a national scale rather than on a community scale. In addition, a dynamic risk index is defined to translate a contamination event into a public health risk as time progresses. More specifically, in this research, GIS is used to map the Canadian produce distribution system, analyze accessibility to contaminated product by consumers, and estimate the level of risk associated with a contamination event over time, as illustrated in a scenario.