Considerations for Field Sampling Romaine Lettuce for Microbiological Testing
1. Introduction (Scott Coates)
In 2010, the Food Safety and Technology Council of United Fresh Produce Association
developed a white paper known as
Microbiological Testing of Fresh Produce
that considered
the use of microbiological sampling and testing procedures for fresh fruit and vegetable
products. This paper provided much valuable information, but left open the question of how
many samples to collect under what conditions.
In 2012, the International Stakeholder Panel for Alternative Methods
(ISPAM) determined that it
would fund a project to advance the cause of food safety in the produce area. With input from
the produce industry, ISPAM determined two high priority areas: 1) standard methods for the
detection of
Salmonellae
in leafy greens; and 2) standard sampling plans for field sampling of
leafy greens, focusing on romaine lettuce as an example. Two working groups were created to
consider the two priorities. The intention is to create a standard for methodology and a standard
sampling plan that are complementary to one another.
1.1. Objective
The objective of this paper is to build on the
Microbiological Testing of Fresh Produce
white
paper by providing specific recommendations regarding the number and location of test
samples to collect, and the best practices for collecting test samples to detect
Salmonella
from
pre-harvest fields of romaine lettuce.
1.2. Scope of the paper
This paper considers the current reasons for field sampling and industry production practices
and controls of known hazards, the most likely sources of field contamination and
recommended controls. Limitations because of product shelf-life such as inability to
resample/retest and the need for rapid test method will are examined. The different types of field
contamination patterns are also considered and recommendations are provided. This paper
also reviews the ICMSF (ref) and Codex (ref) sampling plans and their assumptions.
For the purposes of this start-up project, the working group, and therefore this paper, is focused
specifically on the detection of
Salmonella
in pre-harvest fields of romaine lettuce. However,
this project is expected to be the first in several projects in which the recommendations
contained in this paper are considered and applied with appropriate refinements to additional
pathogens, use with leafy greens and at other points in the food chain, such as after harvest but
before processing.
1.3. Audience for the paper
Food safety is a universal challenge, with several well-publicized produce contamination events
occurring in both Europe and the United States in recent years. However, surely produce
contamination events are occurring all around the world all of the time, just not as well detected,
1
ISPAM is funded and organized by the AOAC Research Institute, a subsidiary of AOAC
INTERNTIONAL.
