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Fresh Take
Post-Harvest Water Use and Strategies to Mitigate Food Safety Risks on Your Farm
We welcome back Dr. Keith Schneider for a discussion on post-harvest water use. Dr. Schneider shares strategies to keep produce safe.
Tune in to hear about:
- Why harvest and postharvest water quality is important
- How cross-contamination can occur
- Which mitigation strategies are effective
- The use of sanitizers and their role in growing safe produce
Learn more on our website: https://foginfo.org/food-safety-for-producers/
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https://www.fda.gov/food/guidance-regulation-food-and-dietary-supplements/food-safety-modernization-act-fsma
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Welcome to Florida Organic Growers podcast series Food Safety for Farmers. A project funded by the USDA National Institute of Food and Agriculture Food Safety Outreach Program, our podcast provides information on food safety topics that farmers can use to better understand how to comply with the Food Safety Modernization Act regulations. Thanks for tuning in regulations.
Speaker 2:Thanks for tuning in. Welcome everyone to our latest Food Safety for Farmers podcast, which is part of the Road to Safe and Healthy Food Project. Today, we're very happy to welcome back Dr Keith Schneider, who is a professor and extension specialist at the Food Science and Human Nutrition Department at the University of Florida. We're going to be talking about post-harvest water use. Welcome, Keith. Thank you so much for joining us again.
Speaker 3:Thanks for having me again.
Speaker 2:I think we should just jump right into it. This is one of the questions that we get a lot from farmers, and is the type of water that they can and cannot use. One of the questions that I've heard from organic farmers, for instance, is is there any specific thing that they need to know with the water that they use, whether it be pre-harvest or post-harvest? Today, we'll be talking about mostly post-harvest water and what it is that the Food Safety Modernization Act says about what farmers need to know about the use of their post-harvest water farming activities.
Speaker 3:This information is covered in Module 5, specifically Module 5.2, which is the use of harvest and post-harvest water. We always say post-harvest but it also includes those activities during harvest up until the items are actually packed and shipped. Module 5.1 is pre-harvest and probably the reason we're not talking about that today is that that rule is changing. So we're waiting for FDA to kind of sort that out. But post-harvest and post-harvest water is pretty much staying the same as far as we know, and the rules can be found again Again 21 CFR 112. You can go and kind of read what the regulation requires.
Speaker 2:In our last episode, I remember you telling us and telling our audience, our farmers, that there is no way to completely eliminate pathogens from the field.
Speaker 3:Oh, absolutely. Again, even FDA knows this and they're not trying to make our food sterile, which is good. They realize that again, we're growing stuff outside, they're going to be exposed to the elements. The goal here is to minimize the risk as much as possible, and we do that by several different ways, and we talked about this on the last podcast. Again, monitoring worker health and hygiene, proper use of fertilizers and manures, preventing or limiting the amount of animal activity within a field, proper use of irrigation water and the proper application of water that we use during harvest and post-harvest All these things are going to help minimize the risk. So we're never going to get that risk down to zero, but what we're going to try to do is keep that risk as small as possible, and sort of the mantra is we don't want to turn a small problem into a large problem.
Speaker 2:Right, and so you're talking about proper use of water. Can you give us examples of what may be improper uses of water that can, as you just said, potentially make a small problem into a very, very large problem, and one that obviously farmers wouldn't want to deal with?
Speaker 3:Yeah, this is one of those things where I'm going to backtrack just a little bit, and anybody who's ever heard me talk, my colleague and I. When we talk about water, we can get quite long-winded about it. The amount of information that we usually cover takes about an hour to an hour and a half. But first of all we have to realize what we're using water for and for post-harvest. That's a lot of different things. It could be used for washing field bins or shears or something to that effect. It could be water used to wash workers' clothing.
Speaker 3:More largely, the water that we're using for maybe spraying off produce or a dump tank or flume tank. We use it for making ice, we can use it for, we use it in the restroom facilities, we use it to wash the workers' hands and we're using it to sanitize the equipment. So there's a lot of different places where water again has that potential for making a small problem into a large problem. But one classic example you're using water to spray down your produce and rather than getting that from you know the tap, municipal water or from a deep well, that water is coming from a retention pond or from surface water source that we don't have any control over and we've you know we talk a lot about.
Speaker 3:You know all the care that goes into making sure that the produce is as safe as possible before we harvest it, by controlling again workers and animals and the water we use for irrigation, only to bring it in during harvest and then spray with with dirty water. And that's one of the things we want to. We want to prevent. We want to make sure that any water that we use is adequate for its intended use. That's kind of a term that FDA throws around, but again, we're washing with clean water. You wouldn't buy produce and wash it in your bathtub, right? You're going to wash it in your kitchen sink and hopefully that kitchen sink wasn't used for, you know, prepping a chicken or a turkey just moments before. So we want to make sure that the facilities and the water that we use are clean and that we don't make that small problem worse by cross contaminating or using water that is not of adequate quality to in our produce.
Speaker 2:That is not of adequate quality in our produce. So let me ask you a question because when it comes to that and we can get we consumers and even farmers so concerned about, is my water clean? If it's drinking water, potable water, we know that you can trust that that water is clean. But in terms of just making other assumptions or you know water that's coming from a well you mentioned surface water what are maybe some of the mitigation strategies that can be used, or testing or things that farmers and you know, those things that you're telling farmers that they need to watch out for, that they can test for?
Speaker 3:Okay. So I guess we should start out what is considered adequate for its intended use. So according to FDA, the quality standard we have to meet is no detectable generic E coli per 100 mil sample. So we want to test very large amounts of sample and there are different ways we can test for that, but we should have no detectable generic E coli. Detectable generic E coli. And what we're really saying is we're going to have no detectable fecal associated bacteria like E coli in that very large 100 mil samples. And that's a pretty good, a pretty clean sample. It doesn't mean it's bacteria free, it just means that there's no fecally associated bacteria in that case generic E coli.
Speaker 3:So for harvest and post-harvest activities, if we're using municipal water, we can pretty much guarantee that's not going to have any generic coli because that's tested for and that water's been treated. If we have a well, specifically a deep well that's well-maintained, those water sources again typically do not harbor fecal contamination. Again, the way they're set up, if the well casing is well maintained, we're not going to have any fecal material filtering down through the aquifer and then being pulled back up again. The difficulty here is is if we're using surface water, we no longer can guarantee that that water is going to be E coli free, and if we were to test for it by the time we got the test results back again, it would be the next day and we wouldn't have been able to operate. So for harvest and post-harvest activities we're looking to use either well water or municipal water. Untreated surface water is not going to be applicable in this situation. We're not going to be able to use that unless that surface water is treated somehow.
Speaker 3:Now the treatment is a whole nother story. We can. If we decided that surface water was our only option, we could go in with something like using some type of filtration to get some of the particulate out. We might use chlorine again. It's using pools, something very simple. We can use something like UV light to sterilize that water. There are some folks with lots of money using things like ozone, but it really depends on what the nature of the operation is. Something like treating the water using sodium hypochlorite or calcium hypochlorite would be fine. But if I'm on organic production, that may not be. That may not work for me. I may have to use something like a UV light to make sure that my my water meets that standard. But typically, what we're we're we're talking using well or municipal water for those harvest and post-harvest activities for those harvest and post-harvest activities.
Speaker 2:What about? One of the things that I believe can be part of this discussion is the use of sanitizers and the role that they play when it comes to producing safe produce and, as we're talking about post-harvest water, is that something that you hear farmers talk about or be concerned about?
Speaker 3:Yeah, matter of fact, that's one of my favorite lectures to give. Is that something that you hear farmers talk about or be concerned about? Yeah, Matter of fact, that's one of my favorite lectures to give and it also can be one of the I don't want to say the most confusing, but one of those kind of scratch your head moments. So, yeah, we do use sanitizers and typically you see the most in recirculated water systems. I remember water being those areas where we have the largest potential for making that small problem into a large problem. But again, we use sanitizers for, again, washing our hands, whether that be a gel sanitizer. You just even soap and water to sanitizers we use in the wash center equipment. But when we talk about water and sanitizers, typically we're talking about its use in water treatment, and those are in possibly single pass water systems or recirculated water systems. But here's sort of the kind of the scratch your head moment.
Speaker 3:Under the produce safety rule, you're not required to use a sanitizer in either single or recirculating water, Exactly. So the reason is well, why is that? Well, there's some legal reasons why FDA doesn't mandate that. What they do mandate is, again, that if you are using a single or recirculating water system that you maintain that no detectable generic E coli per 100 millisample throughout your production period. Now, in a single pass you might be more likely to be able to do that. If you're doing a recirculated system, it'd be almost virtually impossible to guarantee that you're not going to pick up some fecal contamination from the field and then use it and start spreading that around for commodities. So while you're not legally required to use a sanitizer, we highly recommend, even in single pass water, two reasons. One, we're trying to prevent the cross-contamination of clean produce by contaminated produce. Remember we're never going to get our produce a hundred percent pathogen free, but what we can do is prevent that pathogen from getting onto uncontaminated fruit and sanitizers are a great way to do that.
Speaker 2:And I imagine that when we're speaking of sanitizers, there's different types of sanitizers and their efficacy also may vary depending on the type of sanitizer that you're using.
Speaker 3:Oh, absolutely. Again, some common sanitizers out there. We have chlorites and again that could be calcium hypochlorite or sodium hypochlorite. Sometimes you might know that as bleach we have peroxyacetic acid, which may or may not have a certain part of that being hydrogen peroxide, and a lot of our PAA type chemistries have proxetic acid, hydrogen peroxide and even a surfactant or wetting agent. All of those are efficacious. Especially, again, if you're being sold a sanitizer.
Speaker 3:You're going to ask your chemical supplier to show you the studies that have been done. They're going to be registered with EPA. Don't use anything that's not registered by EPA. So your bottle will again have an EPA registration number on it and it's also going to have it's going to be labeled for its intended use. Now you can buy bleach or sodium hypochlorite for home use and, you know, for cleaning your laundry. But the sodium hypochlorite you're going to use in your farming operation is going to say for ag water or for vegetable and produce washing, and in that case you're going to follow those label instructions. And for sodium hypochlorite, in those types of operations they'll give you a use dilution. So they'll say 25 or 50 or a hundred part per million. They'll give you typically a contact time and then if you have to follow it up with a freshwater rinse. So each chemical will have its manufacturer's recommendations and they all have to be EPA registered before they're allowed to be used on food. So we're only using food grade chemistries, and that's one thing.
Speaker 3:Now these sanitizers can be very efficacious, but they're also going to have some limitations. So there's no one perfect one out there. Some of them are better dealing with higher organic load in the water. Something like a proxy acetic acid is much more resistant to dirt buildup over the course of a day. It just happens to be more expensive. Sodium hypochlorite is super effective and very inexpensive. The problem with that is it's highly affected by the pH of the water. So if I'm not careful monitoring my pH, something like sodium hypochlorite may be completely ineffective or very ineffective at reducing the amount of microbes. Well, I may smell like I have a lot and I may test it. It may look like I have a lot. It may be in a form that's not efficacious because I'm not maintaining the proper pH.
Speaker 3:Another thing that we also are really concerned about is the buildup of biofilm. So one of the reasons we highly recommend even though it's not required to use a sanitizer. The use of a sanitizer or regularly cleaning your equipment helps reduce the potential for a biofilm, and biofilms, as we mentioned in our last podcast, or build up microorganisms that can one either be pathogenic or harbor pathogenic microorganisms. So if we build up a biofilm, a sanitizer that would work on Monday may not work on Friday if that biofilm gets established. So it's important that we make sure that we don't build these biofilms up, and one of the ways that we prevent this is by the use of sanitizers and proper cleaning on a regular basis.
Speaker 2:Right, right, and that makes a lot of sense. It's just you know, continue to do that on a regular basis. I guess one of the things that, in the case of organic farmers those organic farmers that are listening to our episode today the sanitizers themselves have to be approved by your certifier before you can actually use them. There's reasons for that, but everything that is being used to produce that organic produce must be approved by your, by your certifier. In this case, when we're talking about all farmers, one of the things that I think maybe you've said is important is for them to know whether or not you know these sanitizers are working. So I think having a way to either monitor or keeping good records and making sure that even you know these sanitizers that have to be approved by the EPA are doing what they're supposed to do, you know, having some sort of standard operating procedures even for how these sanitizers are going to be used, you can look up a list of what is an organically approved sanitizer.
Speaker 3:There are plenty of options out there. Your certifier, your chemical supplier, they can all help choosing a sanitizer that is going to meet your requirements. Now, one of the key things we always tell people follow the label's instruction. What may be certified organic at one level may not be if you overuse it or if you double the strength. Chemistries like sodium hypochlorite, you might say you know, one ounce per gallon is good, so two must be better. Not in all cases. Matter of fact, it may make the efficacy worse. So again, using those approved sanitizers, and again, if you're using it for organic, just make sure they're certified for use in organic. But then sanitizers, and again, if you're using for organic, just make sure they're certified for use in organic. But then using them properly is really key, because if you don't use them properly you can actually make things worse.
Speaker 3:Um, on certain, on smaller operations, even larger operations, having written standard operating procedures.
Speaker 3:Sops are our key.
Speaker 3:That makes sure that everybody's using that chemistry properly, that is being stored, uh, and we're making sure that we're applying the right amount to the right type of produce.
Speaker 3:And by keeping good records and having standard operating procedures. One thing that we can all do, whether it be organic or conventional, is that we want to be as judicious as possible with the amount of chemistry as we're releasing into the environment, because every drop of water we extract whether it's brushing our teeth, cooking, applying to our produce it has to go back into the environment someday. So we want to make sure that every drop of water that we're using and, if we have to use a sanitizer, that we're putting just enough to do the job we're monitoring it so we get the most efficacy out of it and we're not overusing. We we're monitoring it so we get the most efficacy out of it and we're not overusing. We want to be good stewards of the environment and again, whether you're using organic or conventional, again, if we use them properly, things will go better, and that's always the thing that we stress when we do these lectures.
Speaker 2:Right, absolutely. One of the things I was just thinking that I've heard from farmers, especially as we talk about, you know, water and post-harvest water use, is the concepts or ideas of what cleaning, you know, washing, sanitizing and maybe even disinfecting mean. I under the impression that they don't actually mean the same, and when people are talking about cleaning or washing, or sanitizing or even disinfecting, some people might think oh well, you know it's clean because I, you know I triple wash or it's you know. Is that true? Or is there something that I think you know you can share with us in terms of you know what all these terms really mean and what people really should be concerned about or not concerned about?
Speaker 3:Sure, there's a couple of terms that are used sort of synonymously and they really mean completely different things for microbiologists. So we have sanitizing, disinfection and sterilization. Sterilization usually means inactivating both what we call vegetative cells actively growing cells and ones that are maybe dormant, things like spores. When we disinfect things like spores, when we disinfect, we're usually eliminating those vegetatives that are actively growing organisms, but not necessarily the spore-forming organisms. And then sanitizing is reducing microbes to a safe level that one has a little bit of wiggle room in it. So if I'm reducing to a safe level, well, if I'm starting out with a million microorganisms, I have a much harder job to get to a safe level than if I was starting out with, say, a thousand microorganisms. So sanitizing is a little bit more vague, but really what we're doing is making that surface or water clean to a point that it's not going to cause illness, and it really depends on how dirty the water is to begin with. So they mean different things.
Speaker 3:When we say cleaning, well, typically if we're going to sanitize, let's say, a surface, you can't sanitize a dirty surface. So the first thing we do is we clean a surface which you know we can brush it off, we could you know use, you know wet, and you know use maybe a soap or some other type of agent to list any dirt off. Um, and then we usually rinse that off and then we apply our sanitizing agent afterwards, so remove all those things that are going to be antagonistic to our sanitizer. So first we have to clean the surface, then we, you know, rinse it, then we sanitize it and occasionally we'll wash it after that. If we have a sanitizer that requires a fresh water rinse, and then we will, we'll try it typically.
Speaker 3:So think of the analogy of when you're doing your dishes at home. If you have a dishwasher, you typically don't stick it in the dishwasher. Dirty, you, you clean it off first, then you, you may rinse it, then you stick it in the dishwasher and then the dishwasher then can adequately sanitize. And now certain dishwashers claim they can, you know, wash, clean, wash and sanitize. Mine's not that good. So again, but that's the operation. We're cleaning it off first so that the the sanitizing step can be most efficacious right.
Speaker 2:So we've been talking about and just to recap, about post-harvest water use and, as you've indicated, the use of water during post-harvest has the ability to make a small problem into a large problem, and you've given us really good tips and we really again thank you for all of the information that you provided. Sanitizers are not necessarily required under the produce safety rule but, as we've been discussing, there's some really good things that can come out of people. You know properly using their sanitizers don't always work the same and that there's certain things that farmers also need to keep in mind when selecting their sanitizers and how they affect the way that the produce is being handled. Do you have any other tips or recommendations for farmers today regarding post-harvest? What are you using in some of the things that we've been discussing?
Speaker 3:I think you pretty much summed it up One. Just remember that when we talk about post-harvest, what are you using in some of the things that we've been discussing? I think you pretty much summed it up One. Just remember that when we talk about post-harvest, that's including those activities during harvest as well as post-harvest. We do recommend, even though they're not required, using some type of sanitizers, again to prevent the buildup of the biofilms that we talked about.
Speaker 3:Whatever chemistry that you settle on on that you've decided that you're going to use one, learn about it. Learn everything you can what affects its efficacy, whether it be the pH of the water, water hardness, the buildup of organic material in the water. Learn what makes it most effective and what hinders it the most. The more you learn about it again, you're going to save money. You're going to choose an effective sanitizer and reduce the amount of problems that you're going to have Again.
Speaker 3:The the biggest one again is like when you're dealing with chlorine chemistry learn how, learn how that works and why adding more makes things actually more problematic. And learn how to properly pH. Again, we keep telling people to pH chlorine sanitizers, but at home, never mix chlorine in vinegar. It's one of those things where that's way over. Too much of an acid is going to make problems worse. Too little of acid is going to make things worse. You want to learn how to do that effectively. When we talked about standard operating procedures, when we're working with any type of chemical, we want to make sure we're going to do it safely, not only for the environment, but for the workers themselves. So again, learn about your sanitizers. Learn how to use them safely and most effectively, because it saves money and it helps out the environment.
Speaker 2:Great. Thank you so much again, keith, for talking to us. We look forward to talking to you in our Road to Safe and Healthy Food podcast series. For the next episode and everyone listening, we invite you to stay tuned. We will continue to share very valuable information as it pertains to the Food Safety Modernization Act, food safety of produce in general and what are some of the requirements that you need to be mindful of. Thank you so much for joining us today.
Speaker 1:Thank you for tuning in. Visit our Food Safety for Farmers podcast page on our website, wwwfoginfoorg, to find more information about episodes and webinars. Subscribe to our email list for updates and submit any questions you may have about food safety.