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Managing Postharvest Water in a Packhouse
51 Plays1 month ago
This episode features Phil Tocco, an MSU Extension Educator for on-farm produce safety, and Claire Murphy, an assistant professor and extension specialist in produce safety at Washington State University. Claire discusses their research on the safety of postharvest water, including how they’re sampling for sanitizer levels and the presence of bacteria. Together, Phil and Claire share best practices that growers and packhouses can consider implementing based on preliminary findings, particularly around monitoring and maintaining postharvest water quality.
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Transcript
Introduction to Produce Safety Podcast
00:00:00
Speaker
Hello, and welcome to the Agri-Food Safety Produce Bites podcast, where we discuss all things produce safety and dive into the rules and regulations surrounding the Food Safety Modernization Act Produce Safety Rule.
Expert Introductions and Backgrounds
00:00:13
Speaker
I'm Phil Toko. I'm with Michigan State University Extension, and I'm based in Jackson, but I cover the whole state with respect to on-farm produce safety. My name is Claire Murphy. I'm an assistant professor and extension specialist in produce safety at Washington State University.
00:00:29
Speaker
And I'm located at the Prosser Irrigated Agriculture Research and Extension Center, ah which is in the Yakima Valley.
Post-Harvest Water Use and Cross-Contamination Concerns
00:00:38
Speaker
So, Claire, you're here in Michigan.
00:00:40
Speaker
I am. Doing some interesting work. I'm curious, what prompted you to get involved with this work? Yeah, so and spent a lot of time working with the tree fruit industry in Washington.
00:00:51
Speaker
So apples, pears, and cherries. And we use a lot of post-harvest water. So flume systems, dump tanks, whether that is to help remove debris or help move product through the packing facility.
00:01:03
Speaker
And the tree fruit industry has gotten a lot of questions lately about... How do they know that their post-harvest water is indeed not causing cross-contamination? Is that process validated?
00:01:14
Speaker
And then also they have a lot of questions about if they're managing and maintaining their water, how long can they hold that water for?
Experiment Design for Water System Validation
00:01:20
Speaker
Because they're getting a lot of demands in terms of like how much water and how they're allowed to discharge that water.
00:01:26
Speaker
Yeah, I know in in Michigan it's the same way. so we have the Department of Environment, Great Lakes, and Energy that is regulating folks with respect to discharges of water. So a lot of our growers, apple growers particularly, have flume systems and they try really hard to manage those flume systems so they don't have to discharge water all the time and change it all the Yeah.
00:01:49
Speaker
Yeah. So you have these folks that are interested in in figuring out, sort of validating their systems. so Tell me how you went about designing an experiment to show whether or not what they're doing is making sense. Yeah. So the big goal of this project is to show that if they're maintaining their water...
00:02:10
Speaker
that there is not an increase in bacterial load on the product before it enters the water system versus after it enters the water system. pretty straightforward idea, but to develop the protocol for how we were going to do this, we spent a lot of time ah talking to people because we wanted to make sure that it was a protocol that could be used beyond just this research project.
00:02:31
Speaker
ah So we started out as a team on this research grant, which is myself, Laura Strawn at Virginia Tech, Michelle Daniluk at University of Florida, and Faith Kreitzer at University of Georgia. And we sat down and we developed a protocol, and then we took that protocol to different groups of people.
00:02:47
Speaker
So we spent some time working with individuals who are on the packing line, who are the ones that are actually managing the post-harvest water on a day-to-day basis. We talked to them about like what they test for, how they make those decisions on a day-to-day basis.
00:03:02
Speaker
And then we took it to some of the larger operations that have many packing houses and talked to like their head of food safety.
Monitoring and Maintaining Sanitizer Levels
00:03:10
Speaker
So they might manage larger companies or or multiple packing houses um because they're the ones that kind of get a little bit more of the say about if they're going to change the water and that kind of thing.
00:03:19
Speaker
And we also brought it to some extension specialists, as well as some of the third-party labs, because most of this testing would be collected but then done by a third-party lab. So we also brought it to them to make sure it was feasible tests that they could conduct and that it wasn't going to be extremely extensive.
00:03:35
Speaker
It sounds like you did your homework with respect to designing sort of what you were going to do. If things are going well, if the if the process that a grower is using or a packus is using is going well, what should that what should we find?
00:03:49
Speaker
Yeah. So we should find that there are active sanitizer levels throughout the water hold time. So if you are using peroxyacetic acid, you'll use some kind of test strip or or titration kit to just make sure you have active levels.
00:04:04
Speaker
If you're using chlorine-based one, we're going to use free chlorine as our indicator. And a lot of these operations might be dosing every hour or so, or they might have an automatic injection ah that is monitoring things like that free chlorine level or ah millivolts or ORP, so oxidation reduction potential, to see when they need to be injecting.
00:04:26
Speaker
So we want to make sure that they have active sanitizer. And then if that active sanitizer is there, then we should see ah hopefully no bacteria in the water. So that's also what we're testing for as well.
00:04:38
Speaker
Cool. Okay. So that that makes sense. So having an active sanitizer, if you've got active sanitizer, then you shouldn't have bacteria. Uh-huh. Yeah, and we're also monitoring for some of our other water physiochemical properties. So turbidity, pH, and temperature, all of which will just help us have a better understanding of if that sanitizer is working effectively and it's working in the way it should be.
00:05:03
Speaker
So we don't know the outcome of the data yet. Not yet. we're We literally just collected it and are putting together the the data sets and the results of some of this stuff.
00:05:14
Speaker
I'm curious what some of the best practices that a grower might want to implement or a packhouse might want to implement ah based on at least the preliminary information that you've gathered from the packhouses.
00:05:26
Speaker
Yeah, so I think there's so many best practices that we could talk about if we're thinking about post-harvest water. i know we spend a lot of time talking about sanitation chemistry because I think that's really important.
00:05:39
Speaker
and And from the preliminary results we've seen, we're seeing that if you have active sanitizer level, your water quality is is going to be maintained. We do want to make sure we're keeping track of what sanitizer we're using and and what that active level is um because it does fluctuate. And if it's too low, we might have a microbial concern.
00:06:00
Speaker
But we've also seen that it fluctuates really high. And then we might have concerns about worker health as well as maybe some of the burning of our products because some of our products are a little more susceptible to high chemistries.
00:06:13
Speaker
And so maintaining and managing and then recording what those sanitizer levels are is a really good thing to to get started as a best practice. Okay. So far if a pack ops were doing this, what kind of frequency would you recommend?
00:06:26
Speaker
Yeah, so I think that's something that you'll want to establish as part of your ah prerequisite programs, part of whether that is your standard operating procedures for sanitation or standard operating procedures for your HACCP program.
00:06:39
Speaker
um You want to set something that's realistic. ok So it's going to be different for every operation. If you write down that you're going to record it every hour, you have to go in and record it every hour.
00:06:50
Speaker
and So if hourly doesn't make sense for you, maybe every two hours, but you'll want to make sure you're at least doing it at the beginning of the day before you get started and a few intervals throughout the day. Okay. So i mean I'm guessing that if I took samples, let's say once every two hours, and after every two hours I realized I needed to add sanitizer to my water,
Differences in Sanitizer Monitoring Methods
00:07:10
Speaker
antimicrobials to my water, would it make sense for me to shorten the frequency of me test days? Yeah, so we want to adjust. If you are taking every two hours and you notice that you do not have active or it's lower than you you thought it was and you're manually adding sanitizers, then yeah, maybe we need to adjust every hour or so.
00:07:28
Speaker
And it's nice because a lot of these results, whether it's a test strip, I like titration kits, ah but they give you instantaneous results. So you'll know right away. ah what your sanitizer levels are.
00:07:39
Speaker
Okay. So if I'm testing, what are the differences between titration kits and and test strips? Yeah. So test strips are truly just like a little piece of paper.
00:07:49
Speaker
You'll put it into your system following like what the time says on the bottle. So a lot of them you hold in the water for three seconds, pull it out, and then you wait like 30 seconds. You match it to a color.
00:08:00
Speaker
So those ones often go by different types of intervals. So they'll go from like 5 to 10 to 15 to 20. Or if we're doing a higher dose, of like 25, 50, 75, 100. And so it's hard with those ones to to read in between some of those intervals of a test strip.
00:08:16
Speaker
I also find them difficult because a lot of them are like 50 shades of blue ah where you have different increasing intensities of blue and I find sometimes I struggle with telling like is it this shade of blue or is it that second shade of blue um but a great option for people if they need ah a quick test or if you can find one that does really work for your system.
00:08:38
Speaker
I like the titration kit, so it's a really easy kit that comes with instructions with a few reagents. And you add your water to a vial and add a few chemicals. And then usually you add a neutralizer and every drop you add will tell you a parts per million. and And you get those in really different levels. So this week we used one that was a half a part per million.
00:08:59
Speaker
And so when the titration kit turned our water sample from pink back to clear, we knew that if we added 30 drops that we had a parts per million of 15 because every drop was 0.5 parts per million. So that one gets us a little bit more exact, um but it does cost a little bit more than our test strips. Gotcha. It also sounds like it's a lot more time consuming too.
00:09:23
Speaker
Not too kind-consuming. We can do it in about a two minutes, so not not too bad. Okay. So I guess if I'm using test strips, I want to make sure that whatever my operating concentration is, that it falls somewhere within the range of those test strips. Yeah. So you'll want to make sure that your test strips fall on that operating limit.
00:09:41
Speaker
ah You'll also want to make sure they're not expired. In that you're right using the right one, which seems kind of silly, but they come in a lot of different types of test strips. So if you're using a PAA system, you'll want to make sure you're not using a chlorine test strip because they do sometimes look a little similar.
00:09:57
Speaker
And then when we test for chlorine, we want to also make sure we're using a free chlorine test strip instead of a total chlorine test strip. So it should never just be a chlorine test strip. Yeah. you labeled that on the bottler. So when we're talking about the chemistry of post-harvest water, when specifically with chlorine, so what happens with chlorine is chlorine is ah really good at attacking or absorbing organic material.
00:10:23
Speaker
And so it will attach to organic material, which can be dirt, debris, or bacteria. um And then it's utilized. So we will have a much higher level of total chlorine because it also takes into account the chlorine that is being attached or being utilized by some of our organic material.
00:10:42
Speaker
So you could have a really high level of total chlorine but have no free chlorine and the free chlorine is what's going to continue to attack things like bacteria and microbes that is going to inactivate them.
00:10:53
Speaker
And so
Impact of Turbidity and Water Quality Management
00:10:54
Speaker
we really want to make sure we have that free chlorine level because that's what's actually available for doing any of that sanitation. Cool. And it sounds like, too, that because chlorine tends to bind with that organic matter, we need to watch. That's why we're watching turbidity. That's why we're watching. Yeah. So we're watching turbidity in this project. And I think it'll help us understand little bit more about that interaction between turbidity and water quality.
00:11:19
Speaker
ah Because we know that relationship between turbidity and free chlorine or sanitizer levels. It just has a higher demand if you have more. ah turbidity but we're hopefully going to see that if you manage your sanitizer and you have active even as we have increasing turbidity throughout the day which we know is going to happen because stuff is coming in on those apples dirt ah leaves etc but if we're hopefully if we have active sanitizer level even as our turbidity gets higher it should still have disinfectant and protect from cross-contamination but then we get back to that idea of at some point in time your turbidity is so high
00:11:57
Speaker
you're just going to keep adding so much chlorine. my Cool.
Comparison of Sanitizers: Peroxyacetic Acid vs. Chlorine
00:12:00
Speaker
Cool. What are the benefits of using peroxycytic acid versus chlorine? Yeah, so peroxyacetic acid does not bind as much with the organic material, so it is better with high organic material loads. um There are obviously higher costs associated with peroxyacetic acid, and then you also need to think about the type of equipment you're using ah because all of these different sanitizers will react with different types of metal differently, um and so you don't want to choose something that's going to either rust or wear down your equipment ah because
00:12:34
Speaker
ah We don't want to have to shorten the the life of that equipment. So you you mentioned chlorine being cheaper. I'm curious if there are things that a grower who uses chlorine or a Pacos who uses chlorine needs to look out for with respect to the systems associated with disbursement?
00:12:54
Speaker
Yeah, so there are different types of chlorine. Usually we see it as calcium hypochlorate or sodium hypochlorate. Regardless, you'll want to get a chlorine that is approved by the EPA for use in post-service wash systems.
00:13:10
Speaker
You'll be able to look that up based on the EPA number, and there's a lot of resources out there that show which ones are approved. um And so when you're thinking about chlorine, you can do it, again, as the sodium hypochlorite or that calcium hypochlorite.
00:13:23
Speaker
And they both have different types of injection systems. what Some are liquids that you can inject in or some are like solid pucks that the water will go over and will slow release water.
00:13:35
Speaker
chlorine into the
Managing Antimicrobial Levels for Safety
00:13:36
Speaker
system. So it's kind of whatever works best for the setup of your operation. um but you'll want to make sure that you kind of think about how that process and then also thinking about the safety of the people who are working with that chlorine.
00:13:48
Speaker
Gotcha. Cool. So tell me a little bit about how a grower or how ah someone who runs a pack house should manage water with respect to the amount of antimicrobial in the system.
00:14:03
Speaker
Yeah, so I think that there are few ways you'll want to do this. ah So the label is the law. And so the label is going to have a requirement on it that you want to be within a specific range during post-harvest water. So if it says you want to be between 20 80, you'll want to make sure you keep it in between that range for that reason. So usually the low is what they want for you to be able to maintain um quality of the water and the high is where we are at for like worker safety.
00:14:34
Speaker
um The other thing you'll wanna do is you'll wanna set something called an operational limit and then a critical limit. So the operational limit is what your facility is hoping to run at. And then also what if it falls below, you'll wanna take action to raise that limit above.
00:14:50
Speaker
So if you really want your sanitizer to be at 30 parts per million, we usually see that operating limit a little bit higher. So 35 or 40. And so still within that range of this example that I've come up with.
00:15:04
Speaker
But you'll want to keep it a little bit higher. And so you know that if you are at your operating limit, you're safe. So i can I can use the operating limit to figure out when I need to make changes to the system to add, maybe to add sanitizer to it.
00:15:20
Speaker
But I don't – but I still know that if I'm making changes to the system, it's not at a point where it's going to impact product quality or safety. Yeah. So the product quality safety limit is going to be your critical limit. So you'll want to set a limit that if your sanitizer level falls below what you've established to be your critical limit – ah that there is going to be some kind of concern for safety. You're going to have to make a decision about either sending that product for a secondary market um because one of the things with post-harvest water is we are not washing produce.
00:15:55
Speaker
So we're not taking bacteria off the surface of the produce. We're just preventing cross-contamination. So if bacteria were to get into that post-harvest water system, whether that be from the apple or from debris that goes in, ah we're preventing it from contaminating another product in that line. Gotcha. And so if we
Enhancing Water Use with Filtration Systems
00:16:15
Speaker
fall below our critical limit, which is where we're concerned about safety, we can't just rewash that because now we don't know if cross-contamination happened.
00:16:25
Speaker
And so we have to act as if cross-contamination did happen. So we like to set... our operating limit higher than our critical limit so that we still have a little bit of wiggle room between that operating and that critical limit.
00:16:38
Speaker
It just helps us protect our product from having to go ah out to secondary market or get discarded or called. So some of the other ways we could also think about how we might extend the longevity of our post-harvest water is having like a split system.
00:16:53
Speaker
And so we see that sometimes where the ah product comes into a dump tank and then leaves that dump tank before. and So it goes up a conveyor belt out of the water and then to and to a secondary flume.
00:17:06
Speaker
And then those two flumes are not connected to each other because that first one is going to get a lot of that debris that might come in from the product or from the the bins or whatever that packing infield was.
00:17:19
Speaker
And then we can change that one a little more frequently than our second one ah because it's taking a lot more of that organic load, which is going to help us maintain the second one better. So that's one way we can manage water. It's having two tanks because we can then have two different change systems on them. Sure.
00:17:35
Speaker
um We can also have like a filtration system, which is going to help like settle out or remove some of that organic material that might build up. So if I had a filtration system, that could conceivably not only decrease the amount of sanitizer, the amount of antimicrobial that I use, but it also could potentially lengthen the amount of time I could use that water. effect Yeah, so it might help you lengthen that water because it'll help maintain some of that other physiochemical water quality.
00:18:01
Speaker
ah It might not, what it would do, and I don't want to say it'll change how much sanitizer, you'll still want to operate at your operating at your critical limits, but it might help with some of that sanitizer demand.
00:18:12
Speaker
And so you might not need to add sanitizer as frequently, but you'll still want to hit your required parts per million. Gotcha. Cool. Thanks a lot for joining us. I appreciate it. Yeah, absolutely.
00:18:23
Speaker
Links to anything
Conclusion and Additional Resources
00:18:24
Speaker
referenced in this episode are provided in our show notes, which can be accessed on the website at canr.msu.edu slash agrifood underscore safety.
00:18:36
Speaker
Thank you to everyone for listening, and don't forget to tune in next month for another episode of our Produce Bites podcast.