FSMA Compliance: Water Usage for Produce

Water has many food-related uses. Many of these uses will impact compliance under the Food Safety Modernization Act (FSMA). Pre-harvest uses of water and FSMA compliance have recently been re-opened by FDA to address the concerns brought forward by many parties in the agricultural community across the country.

At this time, specific new rules have not been promulgated under FSMA regarding cooling or wash water. However, the general guidelines of FSMA apply, implying that one needs to know:

1. What is the process?
2. Why is it the process?
3. How do you know that you did the process?

It is important to recognize that cooling and washing are part of the process and that there is generally no kill step to mitigate failures in control when dealing with produce. Frozen products that are blanched are the major exception.

To address these three questions, it is easier to start with why it is the process. Cooling rapidly removes field heat and slows the metabolism of the product, conserving sugar and thereby preserving shelf life. Washing removes foreign matter and reduces microbial load to some degree. It’s essential to do no harm during both the cooling and washing of these products. For doing no harm, the most important food safety objective associated with both of these processes is mitigation of cross-contamination by managing the water chemistry. This management is complicated by the reuse of water in these processes to reduce energy costs. In any event, allowing trace sporadic contamination to spread is not acceptable. Increasing the microbial lethality of wash processes to a 4 log kill remains the holy grail of produce washing. Unfortunately, a 4 log kill remains out of reach without rendering products unacceptable, but there may be improvements on the horizon.

Challenges

At this point, a diligent processor who wishes to comply with FSMA encounters three important challenges relative to mitigation of cross-contamination. First, there is no gold standard process for washing or chilling that has regulatory standing and that by definition controls cross-contamination. There is no safe harbor. Unfortunately, it is also unreasonable to expect FDA to provide a safe harbor as it would absolve the industry from utilizing the best practical process. Second, there is no standard assay or objective measure for cross-contamination. Without a procedure, no numeric standard can be established. A qualitative standard, such as “no detectable cross-contamination,” is a meaningless bandage unless a procedure sets a standard for how hard one must look. Existing analytical tools such as most probable number (MPN) techniques permit detection of minute levels of cross-contamination. And third, there are limited options for testing whether cross-contamination is mitigated. Taking even a benign organism into a food processing facility is unacceptable. Intentionally inoculating a food or a processing line should not be done. Additionally, no acceptable surrogate has been identified. SafeTraces continues to develop a non-living surrogate but much work remains before it has a commercial product for demonstrating cross-contamination control.

Controlling Cross-Contamination

According to Journal of Food Protection’s “Guidelines to Validate Control of Cross-Contamination During Washing of Fresh-Cut Leafy Vegetables,” featured in the February 2017 issue, authors suggest three options for demonstrating cross-contamination control:

1. Using a surrogate to demonstrate cross-contamination control;
2. Using antimicrobial sensors to demonstrate that a critical antimicrobial level is maintained during worst case conditions; or
3. Validate placement of sensors to assure that a critical antimicrobial level is always maintained.

Figure 1.
Image credit: Yi Zhang MS

Option 1 is direct but subject to all the problems just considered. Options 2 and 3 assume a critical level is known. A critical level can only be established with a standardized assay for cross-contamination and an objective target for control. Neither the assay nor the objective target exist as discussed above. Option 2 also requires an understanding of the worst-case conditions. It is frequently asserted that the worst-case conditions are at high organic load. Research done in the SmartWash Solutions pilot plant using spent water from a commercial operation shows that used water provided better cross-contamination control than fresh water as shown in Figure 1. This figure shows a model system in a Product in Tote washer with steady state free chlorine control provided by a SmartWash Solutions ASAP, cross-contamination from inoculated spinach to uninoculated spinach is largely mitigated even at low chlorine concentrations in spent process water for three commodities in a system where fresh city water failed to control the migration of E. coli inoculum. The spent water included residual SmartWash Solutions SW. Measures sharing a letter within chlorine levels are not significantly different. The identification of the worst-case conditions is more complex than most people realize.