Technical Look on Microbiological Risk Factors in Pre-Harvest Crops

Food monitoring procedures are strongly focused on hygiene to avoid microbiological hazards such as bacterial or viral contamination. A general increase in microbiological safety has already been achieved over the past decades through the establishment of various standards (HACCP, IFS/BRC, ISO 22000). Despite greater safety and longer-lasting products, microbiological control must be improved particularly with respect to fresh products. Most foodborne microorganisms that cause illnesses are zoonotic or geonotic but some have human origins, such as the Hepatitis A, Salmonella phi, and Vibrio cholera. These contamination can occur during the food manufacturing process.

A significant increase in diseases stemming from microbiological infections can be expected in the future. The Federal Institute for Risk Assessment stated that foodborne infections will pose a serious problem to the global public health in the coming years. In the last two decades, there has been an  overall increase in foodborne illness outbreaks and cases linked to fresh fruits and vegetables:

• Vegetables, juices, and related products comprised 4.4 percent of all foodborne outbreaks in the EU between 2008 and 2013.
• In the U.S., 13 percent of foodborne outbreaks between 1990 and 2005 have been associated with fresh produce. Green salad, lettuce, seed sprouts, tomatoes and cantaloupes were identified as the main sources of foodborne illness outbreaks.

Frequent combinations are: Salmonella and cantaloupes, sprouts, or tomatoes; E. coli and leaf green vegetables; Cyclospora and raspberries; and Hepatitis A with green onions.

Within the structured approach to food safety management (Risk Analysis framework), Food Safety Objectives (FSO) are essential tools to meet public health goals. FSOs define the maximum level of microbiological hazards permitted in various foods at the point of consumption. Maximum hazard levels at different points along the food chain represent further performance objectives.

Unlike other commodities, such as beef or chicken that is rigorously inspected, microbiology is often neglected when testing fresh fruit and vegetables because adequate strategies are lacking. Fruits and vegetables are foods with generally short shelf life: however, investigations of microbiological risk take some time. A number of different microbiological testing can be used by industry and government actors. Within-lot testing is one of the most common methods when measuring the hazard against a pre-defined limit but the sampling plans are generally time-consuming and resource-inefficient.

Point source contaminations that cause individual consumer illnesses might occur in fresh produce due to bird feces, for example. However, these kinds of risks are difficult to detect once the product is packed and optical control is insufficient. General or nonpoint source contaminations could cause foodborne epidemics because of the effect on a broad range of products. Pre-harvest sources of nonpoint source contamination are most often soil, feces, irrigation water, water used to apply fungicides and insecticides, dust, insects, inadequately composted manure, wild and domestic animals, and human handling.

The earlier a risk is detected, the better the odds for effective measures and lower overall costs.

On the basis of the European Food Safety Authority results and personal experiences with more than 400 microbiological samples and over 2,500 field visits within the last two years, Analytica Alimentaria has developed a new risk analysis process when testing fruit and vegetables:

1. Effective microbiological risk assessment in the field with a new evaluation system, structured questionnaires, and defined approval policies;
2. Synergies via the efficient linking of risk analysis with pre-harvest sampling;
3. Risk-oriented sampling and laboratory analysis of the correct parameters;
4. Clear escalation scheme in the case of positive findings; and
5. Fast decision-making for retailers.

This article describes the complete process of microbiological risk assessment, which can be a general or nonpoint source contamination of the sampled object (field, warehouse) that can cause a foodborne epidemic or individual illness. As the result of the process, the risk can be calculated and mitigated.