This is how the growers should ensure the irrigation water quality, especially in leafy vegetables production
There are a lot of problems in the leafy vegetables production associated with irrigation water, including microbial risk and difficulties in water monitoring, compliance with evolving regulations and quality standards.
The fact is that the transmission of Escherichia coli O157:H7 to salad plants through spray and surface irrigation was demonstrated. [ETHAN B. SOLOMON, CATHERINE J. POTENSKI, and KARL R. MATTHEWS – Department of Food Science, Cook College, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, USA]
More generally, there is increasing evidence of the contribution of irrigation water in the contamination of produce leading to subsequent outbreaks of food borne illness. The risk is higher for leafy vegetables that will be eaten raw without cooking.
Supermarkets and Food Companies are targeting zero-risk production systems and the associated requirements for irrigation water quality have become more stringent in regulations and quality assurance schemes (QAS) followed by growers. For example, the scheme Field to Fork by Marks&Spencer, the McDonalds Standard and others, they pay a lot of attention about the acceptable limit of E.coli, requiring a monthly testing.
Usually the food safety standards require a safe water source and a sampling protocol to make sure the consistency of the E.coli results.
Why we test E.coli ?
In the baby leaf production, growers should identify water sources that are contaminated with potential pathogens through a monitoring regime and only use water free of pathogens, but the low prevalence of pathogens makes the use of faecal indicators, particularly E. coli, a more practical approach. Initially E.coli was just an indicator of Salmonella ssp.
The irrigation method could be crucial for the leafy vegetables food safety
Where growers have to use water sources of moderate quality, they can reduce the risk of contamination of the edible portion of the crop (i.e., the leaves) by treating irrigation water before use through physical or chemical disinfection systems, or avoid contact between the leaves and irrigation water through the use of drip or furrow irrigation, or the use of hydroponic growing systems.
The current alternatives available for growers to reduce microbial risks is certainly not to continue in the same way. Agronomic techniques can help the growers to eliminate the microbial risk of pathogens.
Anyway the growers use a variety of water sources for field operations and irrigation and much knowledge is needed to relate risk factors associated with the transfer coefficients for pathogens by source, concentration and use.
Probably the combination of these different factors: Agronomic techniques and Quantitative water risk assessment, can increase a lot the food safety of baby leaf production.