Skip to main content
Food SafetyPodcast Interviews

C Bot, Retort Processing and Shelf Stability – “Drips and Draughts” Podcast

Written by Brendan Hanson of the ‘Drips and Draughts’ podcast

Episode Overview

Today, we’re joined by food scientist Rachel Zemser to discuss C. bot, retort processing and obtaining shelf stability, particularly with respect to cold brew coffee. Rachel bring a wealth of information to the show and gives some good insights on why anyone looking to can or bottle should be working with a process authority.

Listen Here

Highlights & Takeaways

  • C Bot can produce a neurotoxin given the right environment
  • If not maintaining refrigeration, retort should be used to obtain shelf stability
  • Use a process authority when canning/bottling and looking for any type of shelf stability

Episode 83 Transcript

Brendan: Hey there welcome back and thanks for tuning in to another episode of The Drips and Draughts podcast. We’ve got another show for you today that was born out of your request. A few weeks back we had on Mike Brown from Death Wish Coffee. We got a lot of requests shortly after the Death Wish Coffee recall because there were a lot of questions surrounding that why it was recalled, what processes were they using. People were just curious.

By the way that was epIndicators are it’s back to business, as usualisode number 80 if you’re looking to go back and listen to that one if you haven’t heard it yet. You can also find it on our website After that episode we had more people reach out asking about the retort process, what that is exactly because Mike in that episode mentioned that they’re looking into retort processing for their future cans of Nitro Cold Brew. That led us to start doing some research and we came across today’s guest Rachel Zemser who is a food scientist.

While our show normally focuses on the companies that produce cold brew and the craft behind it, today we’re switching gears a little bit to explore canned products and the proper practices and procedures that need to be taken in order to achieve shelf stability. Rachel’s got a ton of good information that she share’s with us today and we’ll make sure to link up to her profile and her website in our show notes, which you’ll be able to find on our website. With that let’s get into today’s episode with Rachel Zemser.


Brendan: You’re listening to The Drips and Draughts podcast as always I’m Brendan Hanson and today I’m joined by Rachel Zemser who is a food science consultant. How are you Rachel?

Rachel: Hi, I’m doing great.

Brendan: Great, thanks for joining us today. I’m a little out of my league when it comes to food science so you’ll have to pardon some of what might be stupid questions. I think there’s a need to ask a lot of the questions that I’ve got and hopefully you’ve got some stuff that you can elaborate on in terms of food safety when it comes to cold brew coffee. Before we get into all those questions would you mind telling us a little bit about yourself and your certifications.

Rachel: I’m a food scientist. I have a Bachelors and a Masters in Food Science, that’s what the MS is after my name. I’m also a certified Food Scientist and this is a certification that the Institute of Food Technologist gives to people who have proven that they are well versed in everything food science based on their sets of criteria and what they think a food scientist should be.

I’m also a certified Culinary Scientist and that’s a certification through the Research Chef Association, which means that I’m well versed in culinary arts and food science and they have their own set of criteria and tests that we have to pass to have these credentials. I’ve been in the business for about 25 years and I’ve been working as a consultant for the past 10 years.

Brendan: Wow! You’ve got plenty of certifications and you really seem to like food science. Where did your interest in that come from?

Rachel: I was very lucky when i went off to college in the ’90s. I was looking through the book of majors, I was getting ready to go to UMass Amherst, it was a huge university and I saw food science and I didn’t really understand it but I thought it looked cool and I thought it looked fun. When I went to the university to start off my freshman year, I went over to the department and they told me a little more about it and I got excited about it and that became my major from day one. It was just luck that it intrigued me enough to follow up and dig a little deeper into the program. It was a good choice because I’ve been doing it for a long time and I love just being in the industry.

Brendan: Awesome. Just out of my own curiosity, what’s a typical day for a food scientist? You’re a food science consultant so I imagine you’re working with a bunch of different companies and not just on contract with a single company. Your days have to be pretty out there I would imagine.

Rachel: Yes, my schedule is very unpredictable on a day to day basis. I have five or six clients that I work with and they are all working on different products, baked goods, confections, beverages, smoothies, energy bars and I have a separate laboratory where I keep all of my lab equipment, my Ph meters, refractometers. I am usually there three or four days a week either working with clients or with my assistant or making prototypes for clients.

Some days just won’t involve any lab work. I’ll just be in front of my computer doing nutrition calculations or catching up with a client on information that they need to know or scheduling production runs at the actual manufacturing plant because I don’t manufacture. I just do all the pre-testing and the creation but then we have to move into the production facility to actually make the product itself. There is a lot of coordinating, of test runs and doing actual R&D work in the lab and experimenting with flavors and textures and working with different fibers and basically having a good time playing in the lab and making food.

Brendan: So you are part of every part of the process from start to finish it sounds like?

Rachel: Yes the one part that I’m not involved in and I always make this very clear to my clients is I don’t do their web design, their sales, their marketing. I don’t help them get it into the stores, I don’t do any of the non-scientific work. That’s all on them. I always make it very clear before you begin the R&D part make sure that you have the proper funding in place for actually taking this to the bitter end. You have enough money for production.

Brendan: Sales distribution.

Rachel: Yes, because you have to pay the stores, the slotting fees and you have to pay to have trucks to move your product all around, and warehouse, your marketing, your website, and your Facebook. There’s a lot of work that the food scientist doesn’t get involved in but I am involved in all the technical aspects of it, guiding them along and helping them make it a reality.

Brendan: Awesome. That’s why I reached out to you. We had some people reach out to us regarding some recent news where Death Wish Coffee issued a recall for all their nitro coffee cans and we’ve had people reach out to us saying, “Well, can you guys get any more information on botulism?” I really don’t know anything here so that’s why I’m bringing you in. Thank you for taking the time to come and answer some questions. Can we just jump into this and can you tell us a little bit about, and I’m gonna butcher this, clostridium botulinum. Is that even close?

Rachel: Yes, Cbot. We call it Cbot for short.

Brendan: I could’ve said that.

Rachel: Cbot is probably the most deadly bacteria pathogen that we know of in the world of food producing and food making. There are other pathogens like salmonella and E. coli and listeria and those can make you very sick and they can kill you but botulism is really one of the most serious deadly pathogenic bacteria. It’s not the bacteria itself that makes you sick, it produces a toxin and the toxin cannot be inactivated with regular pasteurization method.

It has to be heated at a much higher temperature. The botulism is a spore-former and when the bacteria grows it produces this deadly toxin and it’s the toxin that when it gets into your food would make you sick. It’s actually toxic poisoning as opposed to the bacterial poisoning. There’s other bacteria like salmonella, E. coli where it’s the bacteria itself making you sick but in this case it’s the toxin.

Brendan: Okay. So the bacteria itself has to be present in order for botulism to grow?

Rachel: Right. The bacteria actually produces the toxin, that’s their mode of protection. They produce this toxin and that’s their deadly weapon.

Brendan: Got it. What’s the environment like that would cause this growth? Obviously, the bacteria has to be present at the start and then is there an ideal environment for it?

Rachel: Yes. Cbot grows best in anaerobic environments. Any food product that is in a sealed anaerobic container for example a can of food, a can of meat, a can of Dinty Moore stew, anything like that is an anaerobic environment that will allow the Botulism to grow. The pH and the water activity are also environmental conditions that will support or suppress its growth. It grows well if the pH is above 4.6, which is a non-acidic environment and it also grows well if there’s some water in there. The bacteria basically needs water and it needs a nice not too acidic environment and it needs no oxygen. Again that’s why I always use the can of meat as a prime example.

A can of meat has protein and it’s got water and it’s in a can so it’s anaerobic, there’s no oxygen getting in there and the pH is neutral, maybe five or six. In the food industry cans of meat, canned meat, canned tuna fish, canned anything that is anaerobic with that kind of a pH is always going to be subject to special food processing conditions that will ensure that the bacteria is killed as well as any toxin that may have been produced and somehow gotten into the food without anyone knowing it.

Brendan: I’m assuming that you can’t really test each can prior to canning or maybe the whole batch for this bacteria, right? That’s probably out of the question in terms of just a process or a procedure?

Rachel: Yes. The way it works in the canning industry and the FDA and the USDA have been researching and working on these procedures for years and years and you don’t really hear people getting botulism from canned foods at all. Sometimes you hear about it in the news, there was something random about a cheese sauce and a 7-Eleven and there’s flukes that happen.

Every manufacturing facility that produces canned foods, they have a processing authority and a team of microbiologists on staff that look at the product, they look at the pH, they look at all of the factors surrounding that food and they put together a process that will ensure that everything in that can is commercially sterile when the production run is complete, which means they really just cook the crap out of it. They cook it to 250 degrees Fahrenheit and higher.

It’s really at the point where they understand their process so well and they know what kind of a process they need to schedule for every kind of product that you really don’t even have to test the cans after they’ve been put through this process because they know that their math is right and they’ve done it correctly. And history has taught them that they can do post-test but as long as the math was done and the scientists knew what they were doing then there’s really no need to test it on a regular basis because the process is that fine tuned and perfected.

Brendan: There’s really no point. Interesting. Let’s say cbot did get into a can or a jar what’s the incubation period for it to start developing a toxin and then likewise if somebody were to consume the toxin what’s the incubation period in a human to start showing signs or symptoms of botulism?

Rachel: I’m not quite sure how long it would take for the organism to produce enough toxin to kill a person and get it into the food. That would really depend on how much of the bacteria was in the food to begin with. For example carrots, they’re pulled out of the earth, they’re very dirty, if they weren’t washed properly there could be some Clostridia on there that would start growing and producing the toxin in the can or in the container. But once the person eats it I believe from what I read on the internet it could be very quick. It could be 12 to 72 hours after ingestion is how long it would take to potentially make someone sick.

And at that point they would have difficulty speaking, I think there’s some paralysis and there’s death. It’s a pretty scary disease. The food industry has zero tolerance for botulism and the rules are just so tight and so strict that it just rarely happens. Most of the examples of botulism that take place are in home canned foods or someone who is not a manufacturing facility or is not really informed. They’ve done something wrong and they didn’t know what they were doing, that’s what usually ends up causing it. It really rarely happens in canned goods nowadays.

Brendan: Got it. Anything else we should mention there? I’ve got to know here to ask about any other serious bacteria or anything else that might be of concern to coffee producers.

Rachel: Well, we should talk a little bit about the process of how food manufacturers inactivate this toxin. What is this process, what is this procedure that they use to make it happen? That is the whole concept of retort and a retort is basically a very large massive pressure cooker where huge truckloads worth of bottles and containers are put into this retort. The food is in the can and the cans go into the retort and then the retort cooks it to 250 degrees plus to inactivate the toxin.

The process that the team of microbiologists and the processing authorities will put together ensures that the can that is in the innermost center of that huge retort is able to hit that 250 degrees Fahrenheit. The cans on the outside might actually go to 270 or even higher but then the can that’s on the innermost that’s protected by all the other cans, they have to make sure that that innermost can is hit with the temperature that will render the product commercially sterile.

That is how it’s all done and when I say can of food, it’s not just a can, it could be a flexible pouch, it could be like those tuna fish packets that you see at the supermarket that are wrapped in foil. That is essentially the modern day version of a can. It’s a flexible shelf stable packaging that will withstand heating up to 250 degrees. It’s important to always think about the pH in the scenario and in the case of the coffee products, the pH of those cold brew coffees was well above the 4.6 pH, which means that when a coffee producer is going to make this coffee product shelf stable, they want it to be in a closed sealed anaerobic can on the shelf.

They have to make sure that they thermally process it, taking into account the fact that its pH is above the 4.6. Usually a coffee maker will have a couple of choices. They can either add acid to drop the pH of their cold brew coffee, which they probably don’t want to do because that will affect the flavor of their coffee.

Brendan: That’s going to change the flavor and it’s not going to be the product that they want.

Rachel: Or they could refrigerate the product and sell it in the refrigerated section because the botulism is not going to grow in a refrigerated environment, it grows best at room temperature. Even if it is refrigerated, there could still be some botulism risk if it’s sealed and if the pH is high because refrigeration temperatures vary. In general if the pH is above 4.6 and they don’t want to bring down the pH with citric acid or another kind of acid and they don’t want to sell in the refrigerated section of the supermarket, they just want it to be a shelf stable can of coffee, they do have to go through this very rough temperature process of the retort, which essentially just boils it and cooks it to an extremely hot high temperature and could kill the flavor.

Unfortunately those are the consequences of being in the shelf stable food industry. There’s really no way of getting around either adding acid to it because if you do add acid, you’re allowed to heat, you don’t have to go through the retort. If you were to drop your pH to under 4.6, you could work with a processing authority, which is a qualified person that the FDA says that you must work with to put together a process to make your acidified or low acid canned food. If you drop your pH, then you are allowed to pasteurize at 185, 195 which I believe is similar to what the Death Wish Coffee people did. They said that they pasteurized it but they didn’t drop their pH to under 4.6. Technically even though their product probably didn’t have any botulism in it, the FDA’s point of view is, it could in theory support the growth of botulism because you have water in there, you have no oxygen and you have a pH of above 4.6. Most likely there was no botulism but as far as the FDA is concerned, there could be.

That’s why there’s a recall and most products that are recalled with the botulism word written on it, it’s usually a scenario like that where there’s probably no botulism but there could be. Something in the process told the FDA or the USDA that not all the proper rules were followed and therefore just to be on the safe side, they’re going to take it off the market.

Brendan: Sure, better safe than sorry.

Rachel: Right.

Brendan: Let’s say their cold chain was a hundred percent controlled meaning that they knew for a fact that their cans were going to be refrigerated from the time they packaged them to the time that the consumer got them. Would that recall still be initiated or is it that the cans are up in the air at the point that the consumer takes them? You don’t know that they’re going to maintain refrigeration at that point. I’m just thinking out loud here.

Rachel: If the product was going to be a refrigerated sealed product, anaerobic product but it is refrigerated then, I don’t believe they would have to go through the retort process. I’m not one hundred percent sure about this but I don’t believe that they would have to go through the retort if it was refrigerated. However really any entrepreneur or any person who wants to bring a food product to market, if they’re going down this path of working with anaerobically sealed container or bottle of a beverage that has a high pH, they really should be working with an unofficial processing authority because these guys are like the experts.

They’re usually seasoned microbiologists who’ve been working in food safety for years and years and years and the entrepreneur needs to work very closely with them to determine if their product needs to be retorted or not. Because there’s always a lot of different rules and conditions and the whole product has to be evaluated as a whole to make that final decision. Maybe if they added a little acid then the processing authority would say, “okay you’re good, you don’t actually need to do the retort now”.

The entrepreneur cannot make that decision on their own, they have to enlist the help of this processing authority by law according to the FDA, USDA law. I’m not a processing authority. I believe there’s a very expensive course that I could be taking in Washington DC that would make me processing authority if I want to go down that path but I’ve worked with many processing authorities. Their job is to go into the manufacturing plants and look at the system that’s going to be processing that food product and determine what needs to be done to ensure commercial sterility and shelf stability and safety.

That way, if an entrepreneur were to have a recall, the first question the FDA is going to ask them is, who is your processing authority? They really need to have one, they need to say our processing authority was this person, this is how he advised us, this is why we did what we did. Not we didn’t know, we didn’t know that we needed a processing authority. You have to have one anytime you make any kind of a shelf stable product, not refrigerated. Probably the refrigerated they would be fine but they still want to check in with one just to be on the safe side, just to make sure that they’re not missing anything.

Brendan: Sure, you still want to have the best processes and procedures that you can.

Rachel: Correct.

Brendan: I’m just thinking out loud how you mentioned taking the pH level down below 4.6. Is that why we see citric acid added to so many products these days? Whether it be a packaged good or a canned good. I feel like citric acid shows up on almost everything when you look at a label.

Rachel: In some situations citric acid might be added for flavoring because it makes things tangy. If you were to make like an orange flavored candy or an orange soda you might want to use an orange flavoring but maybe the flavoring doesn’t have that citrus, mouthwatering tang so they’ll add a little bit of citric acid. Sometimes it’s used for flavoring but a lot of the times, especially in shelf-stable beverages and products, it would be added to drop that pH to allow the food maker to pasteurize instead of retort and there’s a lot of situations where pasteurization is easier for a variety of reasons.

One is there’s way more manufacturers who can do pasteurization versus retorting. You have to really produce extremely high volumes to get in with a retort facility and have them produce your product for you like hundreds and thousands of bottles and cans because it’s a serious process. They are not just going to make a couple of thousand for you. It’s once you’re in you’re in big time with the retort people. But pasteurization you could get away with smaller production runs, there’s more processors out there who can do acidification of foods.

That’s actually the plus and that’s why a lot of people choose to drop their pH with an acid versus going down the retort path although in many cases the retorted beverage would probably taste better. You almost have to pick your poison like what’s worse, cooking your products for really really really high hot 250 degrees F temperature or adding a bunch of acid to it? Unfortunately, we are all used to eating canned food and canned meats and canned tuna fish and it does have a certain flavor associated with it that we’re used to and I would much rather have tuna from a retort than tuna fish that’s had a bunch of acid added to it.

So the retorting process is just so expensive that it’s not really a path that many can afford to go down. So this is going to be difficult for the cold brew coffee entrepreneurs who don’t want to thermally process their coffee to make it shelf stable. They’re going to have to add the acid and they’re going to have the processing authority tell them how much acid they’re going to have to add and how long they are going to have to heat it up the pasteurization temperatures.

Brendan: Okay got you. What about for me just at a personal level, cold brewing coffee on my counter and then throw it in the fridge? Anything I need to worry about there?

Rachel: No, if you’re putting it in the refrigerator, then you’re okay, you’re keeping it cold. There’s not really a concern there. I know that sometimes you hear about the dangers of making sun tea. I know years ago you could make sun tea on your porch and you were just brewing that tea at room temperature and then sealing it up.

Anytime you go down that anaerobic path where you’re sealing it and you’re not refrigerating it, there is some potential for botulism, for the toxin to be produced if the bacteria was in there to begin with. Making it at home and refrigerating it you’re fine. It’s only if you were to make it and then seal it up and not put in the refrigerator, on your counter, then you would be making a potentially hazardous food. Potentially. It might not be but it could be.

Brendan: Got it. That’s where we could start running into problems.

Rachel: Right.

Brendan: Awesome. Well, Rachel, I think we have all just about covered everything here. If people want to reach out to you or follow you online where could they go to do that?

Rachel: My website is and that’s pretty much my space on the internet. They can find me there, they can contact me through the website and I’m happy to talk to anyone about food safety or acidification of foods or the retort. There’s a lot of articles out there as well, lot’s of information available. Once people know what they’re looking for and they know what they have to be concerned about then they know how to search for it on Google and all of a sudden there’s just a wealth of information that will come their way.

Brendan: Right, and that’s actually how I found you. You do a good job of getting yourself out there. I think I was googling retort processing and your name popped up and you were nice enough to respond to my message so thank you.

Rachel: Well, I’ve worked with companies before that had botulism recalls. Not because there was any botulism in the products but there was the potential for it to grow and I learned a lot. You always learn when bad things happen and when our company went through this I got to spend a lot of time with processing authorities and understanding what went wrong and how to avoid it in the future. I’m always happy to share that information with other entrepreneurs because it’s just something that you don’t really encounter until you encounter it happening to you and that’s really the worst time to encounter. You want to be aware of what could happen before it happens.

Brendan: Yes, stay ahead of the curve.

Rachel: Definitely, you got to stay ahead of the curve and just be aware of what can cause it and how to make sure you line up all of your ducks and do everything right the first time around.

Brendan: Yes, absolutely. Thank you so much for joining me today and hopefully, we can send some people your way.

Rachel: Yes, absolutely. I’m glad that I could shed some light on botulism.

Brendan: All right, thanks Rachel.


Brendan: Alright another big thank you to Rachel for joining me today. Lots of good information there and I think she really helped to highlight some of the processes and procedures that should be taken when producing cold brew, especially when you’re trying to achieve shelf stability. If you’ve got any questions for Rachel, you can check out her website at . Rachel actually has an ebook as well, it’s called The Food Business Toolkit for Entrepreneurs.

That might be something that you want to check out if you’re looking to get into cold brew and canning or bottling cold brew especially. Again, we’ll put links to Rachel’s website in the show notes. A couple of big takeaways from today’s show. One, if you’re looking to can or bottle cold brew you’ve got to make sure that it stays refrigerated. If it’s not going to be staying refrigerated then it’s either got to be retort processed or it’s got to have a pH less than 4.6.

Another take away is if you are canning or bottling your cold brew you should definitely be working with a process authority, somebody who will review your processes and procedures and tell you all the necessary steps that you need to take in order to ensure that your product is shelf stable. All right guys, if you’re looking for links or show notes from this episode, you can find those by going to One final thank you to Rachel Zemser for joining me today.

Check out the podcast and learn more about ‘Drips and Draughts’
Enter your MyShopify URL



Access The Best Selling Guide Here! 
Best Selling E-book