Hi, pedant here.
Hi, pedant here. I was inspired by an interesting post on brewing iced tea in which it is stated that it is safer to brew the tea in the refrigerator. When challenged by a microbiologist (self-proclaimed - I'm sure they are, but it's the internet. We could all be claim to be clairvoyant. Who'd know?) in the comments, the post author supported himself with research he had done on materials from the CDC. What I will rebut below are the selected passages he chose to highlight as most relevant to his conclusions. Be warned, he chose a long section, so this is not short.
His quoted excerpts:
Passage 1:
"Iced tea could become contaminated with bacteria at any of several steps in its production, e.g., growing, harvesting, processing, transport, steeping, and storage of brewed tea." Cultures of smooth black leaf tea have yielded total coliform counts as high as 1,100 most probable number (MPN) per gram, fecal coliforms up to 23 MPN/g, and Klebsiella (Thomas J. Lipton Company, unpublished data). Other studies conducted at T.J. Lipton showed that tea brewed in a clean urn at 175F or higher and stored at room temperature had no detectable coliform counts during the first 16 hours of storage. After that time, total coliform counts grew exponentially. Tea brewed at lower temperatures of sampled from an irregularly cleaned urn yielded coliforms, including Klebsiella and Enterobacter, after shorter storage times. Cultures of swabs of a cafeteria urn after "routine" cleaning revealed total coliform counts of up to 12,000 CFU/gram of biomaterial collected from the faucet, but not from other parts of the urn. In other studies, Salmonella has been documented to survive in brewed tea at room temperature
Passage 2:
3. The practice of making "sun tea" by steeping tea bags in a container of water in the sun may be higher theoretical risk than brewing tea at higher temperatures because it provides an environment where bacteria are more likely to survive and multiply.
Wow. Let's start at the beginning, shall we?
"Iced tea could become contaminated with bacteria at any of several steps in its production, e.g., growing, harvesting, processing, transport, steeping, and storage of brewed tea."
Did not go back to original source, just used his excerpt. As such, this clearly applies to any form of tea, not just iced. But that said, if you brew it in the fridge, it is still subject to these potential contaminants, no?
Ok. So the next bit is a bit long, so I won't recopy it but you can see it up top.
Basically, loose leaf black tea has bacteria on it, specifically some of the tummy bug causing ones. After you brew tea with it at or above 175 degrees farenheit, AND LEAVE IT OUT AT ROOM TEMPERATURE, it takes about 16 hours before you can start culturing bacteria again. After that, it's a big old poopy bacteria stew (if you translate "coliform" as "poopy bacteria" and "counts grew exponentially" as "big old stew").
My takeaway:
If you have leftover tea after you brew it, store it in the fridge.
Ok. Next.
"Tea brewed at lower temperatures of sampled from an irregularly cleaned urn yielded coliforms, including Klebsiella and Enterobacter, after shorter storage times."
Right. So did you notice that the first bit about the hot brewed tea specifically said it was brewed "in a clean urn"? Now, not only have we changed the variable of brewing temperature (to anything under 175F), we have also changed the "clean" urn to an "irregularly cleaned" urn. My translation there would be "dirty". So we have a specific source of potential contamination other than the tea itself and we are no longer controlling for temperature effects in isolation. There's also no clarification on the relative amounts of bacteria in the under 175 tea versus 175+ tea, just "shorter storage times". Let's assume this was also at room temperature so at least one variable hasn't changed.
Moving on.
"Cultures of swabs of a cafeteria urn after "routine" cleaning revealed total coliform counts of up to 12,000 CFU/gram of biomaterial collected from the faucet, but not from other parts of the urn."
IOW, people, if you are in the habit of drinking your tea from a samovar or other publicly shared source of tea, people are touching that spigot thingy and they haven't washed their stinking paws. Probably very similar to the colloquial wisdom on drinking from water fountains. Also, the people who clean tea urns don't clean the spigots.
My takeaway:
If you are brewing your tea at home, and you are putting it in something with a spigot, don't shove the cup/mug/whatever right up against it. Let the tea flow into it from a small, non-contact distance away from the spigot. And wash your hands before you touch it, you damn dirty ape.
Next:
"In other studies, Salmonella has been documented to survive in brewed tea at room temperature_"
Ok. So not only do poopy bacteria survive in brewed tea at room temperature, as previously noted, so does Salmonella, which, from a certain perspective, could also be called poopy bacteria. Since this doesn't specify hot or cold brewed, one can only speculate.
The final excerpt:
"The practice of making "sun tea" by steeping tea bags in a container of water in the sun may be higher theoretical risk than brewing tea at higher temperatures because it provides an environment where bacteria are more likely to survive and multiply."
So the risk is theoretical. Knowing that he excerpted these passages, notwithstanding there is possibly other more rigorous information in the source documents (or not, you might be sad reading a lot of published research), it is not logically possible to conclude from these excerpts that brewing tea under 175F (inferring that is what is meant in this context by "higher temperatures") "provides an environment where bacteria are more likely to survive and multiply."
Do you get bacterial growth after 16 hours sitting out at RT (room temp)? Yep. Does this happen faster if you brew tea below 175F? If you use a dirty urn, yep. Do the bacteria you can find include Klebsiella, Enterobacter, and Salmonella? Yep.
If you brew your tea in a clean container in the sun, does it grow more bacteria at every time point than if you hot brew your tea? Unknown. If you store your tea, however brewed, in the refrigerator less than 16 hours after brewing it, does it grow bacteria at any point; when; how much? Unknown.
Exactly how do you translate "most probable number" into an equivalent for "omg, am I gonna die?" anyway, because that's probably more relevant than artificially constructed units of measure that are an attempt to create reproducible quantitative data. And that matters if someone is going to look and say, omg, 1,100 is a big number, that sounds bad! without knowing what it really means in terms of causing real human illness.That being what is implied by "safe" or "unsafe".
Here's the thing. It might really be relatively safer to cold brew tea in the fridge. Or it might not. You cannot draw those conclusions from this information. If that information is in the original paper, by all means present it. If it is, though, you picked the wrong stuff to support those claims.
Ergo, sorry, you cannot broadly assume that it is less safe to brew tea in the sun than in the fridge based on this information.
Thank you for listening. This has been your occasional pedantic broadcasting post. Brought to you by Lipton, culturing coliforms since 1871. We now return you to our regularly scheduled postings.
His quoted excerpts:
Passage 1:
"Iced tea could become contaminated with bacteria at any of several steps in its production, e.g., growing, harvesting, processing, transport, steeping, and storage of brewed tea." Cultures of smooth black leaf tea have yielded total coliform counts as high as 1,100 most probable number (MPN) per gram, fecal coliforms up to 23 MPN/g, and Klebsiella (Thomas J. Lipton Company, unpublished data). Other studies conducted at T.J. Lipton showed that tea brewed in a clean urn at 175F or higher and stored at room temperature had no detectable coliform counts during the first 16 hours of storage. After that time, total coliform counts grew exponentially. Tea brewed at lower temperatures of sampled from an irregularly cleaned urn yielded coliforms, including Klebsiella and Enterobacter, after shorter storage times. Cultures of swabs of a cafeteria urn after "routine" cleaning revealed total coliform counts of up to 12,000 CFU/gram of biomaterial collected from the faucet, but not from other parts of the urn. In other studies, Salmonella has been documented to survive in brewed tea at room temperature
Passage 2:
3. The practice of making "sun tea" by steeping tea bags in a container of water in the sun may be higher theoretical risk than brewing tea at higher temperatures because it provides an environment where bacteria are more likely to survive and multiply.
Wow. Let's start at the beginning, shall we?
"Iced tea could become contaminated with bacteria at any of several steps in its production, e.g., growing, harvesting, processing, transport, steeping, and storage of brewed tea."
Did not go back to original source, just used his excerpt. As such, this clearly applies to any form of tea, not just iced. But that said, if you brew it in the fridge, it is still subject to these potential contaminants, no?
Ok. So the next bit is a bit long, so I won't recopy it but you can see it up top.
Basically, loose leaf black tea has bacteria on it, specifically some of the tummy bug causing ones. After you brew tea with it at or above 175 degrees farenheit, AND LEAVE IT OUT AT ROOM TEMPERATURE, it takes about 16 hours before you can start culturing bacteria again. After that, it's a big old poopy bacteria stew (if you translate "coliform" as "poopy bacteria" and "counts grew exponentially" as "big old stew").
My takeaway:
If you have leftover tea after you brew it, store it in the fridge.
Ok. Next.
"Tea brewed at lower temperatures of sampled from an irregularly cleaned urn yielded coliforms, including Klebsiella and Enterobacter, after shorter storage times."
Right. So did you notice that the first bit about the hot brewed tea specifically said it was brewed "in a clean urn"? Now, not only have we changed the variable of brewing temperature (to anything under 175F), we have also changed the "clean" urn to an "irregularly cleaned" urn. My translation there would be "dirty". So we have a specific source of potential contamination other than the tea itself and we are no longer controlling for temperature effects in isolation. There's also no clarification on the relative amounts of bacteria in the under 175 tea versus 175+ tea, just "shorter storage times". Let's assume this was also at room temperature so at least one variable hasn't changed.
Moving on.
"Cultures of swabs of a cafeteria urn after "routine" cleaning revealed total coliform counts of up to 12,000 CFU/gram of biomaterial collected from the faucet, but not from other parts of the urn."
IOW, people, if you are in the habit of drinking your tea from a samovar or other publicly shared source of tea, people are touching that spigot thingy and they haven't washed their stinking paws. Probably very similar to the colloquial wisdom on drinking from water fountains. Also, the people who clean tea urns don't clean the spigots.
My takeaway:
If you are brewing your tea at home, and you are putting it in something with a spigot, don't shove the cup/mug/whatever right up against it. Let the tea flow into it from a small, non-contact distance away from the spigot. And wash your hands before you touch it, you damn dirty ape.
Next:
"In other studies, Salmonella has been documented to survive in brewed tea at room temperature_"
Ok. So not only do poopy bacteria survive in brewed tea at room temperature, as previously noted, so does Salmonella, which, from a certain perspective, could also be called poopy bacteria. Since this doesn't specify hot or cold brewed, one can only speculate.
The final excerpt:
"The practice of making "sun tea" by steeping tea bags in a container of water in the sun may be higher theoretical risk than brewing tea at higher temperatures because it provides an environment where bacteria are more likely to survive and multiply."
So the risk is theoretical. Knowing that he excerpted these passages, notwithstanding there is possibly other more rigorous information in the source documents (or not, you might be sad reading a lot of published research), it is not logically possible to conclude from these excerpts that brewing tea under 175F (inferring that is what is meant in this context by "higher temperatures") "provides an environment where bacteria are more likely to survive and multiply."
Do you get bacterial growth after 16 hours sitting out at RT (room temp)? Yep. Does this happen faster if you brew tea below 175F? If you use a dirty urn, yep. Do the bacteria you can find include Klebsiella, Enterobacter, and Salmonella? Yep.
If you brew your tea in a clean container in the sun, does it grow more bacteria at every time point than if you hot brew your tea? Unknown. If you store your tea, however brewed, in the refrigerator less than 16 hours after brewing it, does it grow bacteria at any point; when; how much? Unknown.
Exactly how do you translate "most probable number" into an equivalent for "omg, am I gonna die?" anyway, because that's probably more relevant than artificially constructed units of measure that are an attempt to create reproducible quantitative data. And that matters if someone is going to look and say, omg, 1,100 is a big number, that sounds bad! without knowing what it really means in terms of causing real human illness.That being what is implied by "safe" or "unsafe".
Here's the thing. It might really be relatively safer to cold brew tea in the fridge. Or it might not. You cannot draw those conclusions from this information. If that information is in the original paper, by all means present it. If it is, though, you picked the wrong stuff to support those claims.
Ergo, sorry, you cannot broadly assume that it is less safe to brew tea in the sun than in the fridge based on this information.
Thank you for listening. This has been your occasional pedantic broadcasting post. Brought to you by Lipton, culturing coliforms since 1871. We now return you to our regularly scheduled postings.
Man, every time I see a self-identified microbiologist vomiting screeds like this somewhere, I am taken aback anew. My training in microbiology left me ever-more confident that a) there's no point trying to avoid all bacteria, the fuckers are everywhere and b) with a few admittedly terrifying exceptions, infectious doses of bacteria are really pretty high, and unless you're immunocompromised, just eat the damn sandwich.
ReplyDeleteWell. I may have phrased this poorly, but the microbiologist was trying to tell Mr. Lopez-Alt that he might be mistaken, and Mr. Lopez-Alt responded by quoting those passages from CDC published stuff. Mr. Lopez-Alt said more than once in his post on brewing iced tea that sun tea was not as safe as brewing in the refrigerator. If he quoted data that genuinely supported his contention, neither the self-declared microbiologist nor I would have taken him to task. As it is, he tripped my BS alarm.
ReplyDelete