Expert: John Locke - 9/9/2007

Question
QUESTION: This question is kind of trivial I suppose, but I work in a restaurant, and people tend not to change the dish water on a regular basis when washing dishes. There is always obvious food floating on the surface, and you certain can't see to the bottom of the sink. In my experience I think dishes get a lot cleaner when you can always see the bottom of the sink, and you spray most of the food off before just throwing it into the sink. Is there anything out there I could use to encourage people to do things my way, or is their no proof that it makes much of a difference? I think the amount of debree in the water effects the temperature of the water as well. What do you think? And also on an unrelated note how did you end up being called John Locke? Were your parents aware of the previous one? lol. Thank you. :)

ANSWER: Thanks for using AllExperts, James. You're the first person, if I recall correctly, to notice the name's historical significance; I must regretfully tell you that it's a pseudonym, chosen simply because of my appreciation for the philosopher. Locke believed that man could prosper through reason, and that people could (and should!) ultimately tolerate each other; I hope to pay tribute to him, though what little effort I put forth here absolutely pales in comparison to his quest for truth. It's even on his tombstone: "Bred a scholar, he made his learning subservient only to the cause of truth." How amazing is that?

But more to the point of your question. When you stop to think about it, restaurants can, without the proper precautions, be quite disgusting. The major points of concern here are pathogenic (disease-causing) bacteria and viruses; much of what I'll say about bacteria below also applies to viruses, with the exception of growth conditions.

Customers transfer bacteria between their mouths and their dinnerware by eating, talking, and drinking; they are both exposing the restaurant staff to their bacteria and exposing themselves to any bacteria left on the dinnerware from the staff. Now, most of these bacteria are harmless and entirely familiar--we all have many of the same species of microbes growing in our mouths and on our skin, but that's hardly a guarantee of safety. Beyond that, of course, there is the risk of pathogenic organisms that may be carried in food (E. coli, Salmonella, and Listeria, to name a few). If pathogenic bacteria can thrive in the dishwater environment you've described, that could pose a health risk to your coworkers and your customers.

Bacteria are marvelously adaptive--they can be found living in hot springs, on the tops of moutains, inside caves, in airless containers, and so forth. Earth bacteria have even survived inside equipment that was exposed to the vacuum of space during the Apollo missions. Let's consider only the relevant environments for bacteria that restaurant-goers might be exposed to, however; these bacteria prefer warm (though not extremely hot--usually less than 110 degrees Farenheit), moist, and dark environments with plenty of nutrients. Since bacteria have simple digestive systems, they can only use simple sugars for energy. They also need enough space to grow so that they won't overcrowd each other--when bacteria are placed in their optimal environment, they increase in number very quickly.

Unfortunately, the situation you describe sounds very much like a favorable one for the growth of bacteria. Stagnant water with food scraps, particularly warm water, can allow for the explosive growth of bacteria. Pathogenic or not, having huge bacterial growth in the water that you're planning to use for cleaning is not a good idea. Now, I understand that this is dishwater, and it is true that the detergent that's present will destroy some of the bacteria; however, the microbes can still continue to grow unimpeded. In fact, I've found a reference in the scientific literature that's exactly on point: a baker who vomited in a sink and then cleaned it wound up transmitting norovirus--a nasty gastrointestinal disease--to 248 other people who either ate or served food prepared by him using that same sink.

To repeat: the situation you describe does have the potential for allowing bacteria and viruses to be transmitted between dirty and clean dishware. Scraps of hot food in the dishwater will make the situation even worse, as they will indeed raise the temperature of the water to allow for microbial growth, but not high enough to cause microbial death.

What can you do to prevent this? I suggest that for starters, you or the restaurant owner contact the local health department to determine what guidelines and requirements exist (I gather from your letter that this is not an area of concern for many other people; use your best discretion in how you proceed with this). There are automated dishwashers that spray hot, soapy water and are designed for the commercial kitchen; these eliminate many of the concerns described above. At the very least, the dishes could be rinsed off in one sink, soaked in another with soap (change the water regularly, too!), and washed/rinsed over a third. Whatever steps you can take to get dirty dishes out of stagnant water should improve the situation.

What's something you could use to convince other people of this problem? Well, you could start with the norovirus example above. Here's another: a restaurant in Nigeria was found to contain seven (!) types of pathogenic bacteria all commingled together in the freezers. What allowed this to occur? Stagnant water in the bottom of the units. Let me provide you with some more select quotes from scientific papers (if you'd like to look for yourself, go to the PubMed website--address below--and search for "restaurant bacteria dishwater"):

Using a 3-bowl system (soak in the first, wash in the second, rinse in the third) reduces bacterial concentrations, while using a single bowl can re-contaminate the food: "Bacterial load on contaminated tins is reduced when the 3-bowl system is used. Uncontaminated tins become contaminated in bowl 1, but this is then reduced in subsequent bowls."

"Further experiments used a washing-up process simulation, where soiled dishes contaminated with bacteria were washed in a bowl of warm water containing detergent...a proportion of sterile dishes washed after contaminated dishes became contaminated with pathogens but transfer from dishes onto food was rare." Although bacteria did not transfer from dishes to food, the transfer of bacteria from dishes to hands and vice versa is well-documented.

This study involved a proper dishwasher, rather than handwashing, but it highlights the importance of rinsing before putting the dishes in the sink: "Different adherent soils, both with and without bacterial contamination, were used to show the effectiveness of the dishwasher to remove this type of soil. It was shown that contamination will occur from the dishwater to crockery with adherent soil. These results demonstrate the importance of cleaning soiled surfaces of crockery mechanically in the dishwashing process."

Make of all that what you will. I wish you the best of luck!

PubMed: http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed


---------- FOLLOW-UP ----------

QUESTION: I finally caught you after you mysteriously went on vacation right after answering this first question. I have a followup for you. :) First off in college I was a psych major so we learned the history of many early psychologists and philosophers so I became aquainted with the work of John Locke and some other very interesting characters. And as for sanitation I was going to say that I think food floating in the water actually seems to cool the water. I tend to wash with very hot water whenever possible. I actually work at Taco Bell so I know that there are food sickness issues to be worried about. lol. We wash everything by hand and have a three sink system. One for soaking, one for rinsing, and the last for sanitizing. I soak and scrub in the first one after spraying off all hard buildup stuff into the center sink where most of the food collects as to keep my soapy water clean and use the last sink for both rinse and sanitizing. I feel I get the dishes cleanest as other people end up putting dishes away that still clearly have food on them. I'd really be curious to see our kitchen under a black light or something to see whos methods work best. What do you think? Also I believe that maybe 4 out of 5 states require the use of gloves when working in restaurants? What do you think of that? I personally think we could make a fastfood restaurant out of this Taco Bell if we didn't have to work our fingers into these flimpsy gloves, have trouble with seperating wrapping papers, work with the ingredients accurately, etc. And change the gloves every time they rip and our built up sweat comes pooring out of them. I would think if we washed our hands often enough things would be just as well? In the Taco Bell training videos they don't even wear gloves. What do you think?

Answer
"And as for sanitation I was going to say that I think food floating in the water actually seems to cool the water."

Thanks for catching that, James. The physics regarding this situation is quite simple: heat will flow from the hotter body to the cooler body, meaning that whatever is hotter will lose heat until it equilibrates with the surroundings. In the case of a sink full of hot water, you're right--any food that comes off of plates would most likely be cooler than the water. The scraps of food will absorb heat from the water, which is really just another way of saying that the food cools down the water. Regardless, the presence of food creates what could properly be called a banquet for the growth of bacteria.

"I actually work at Taco Bell so I know that there are food sickness issues to be worried about. lol."

That's the truth. Almost every major restaurant chain has at some point been involved in a food-borne illness situation. I'm not impugning your capacity or that of your employer: more restaurants simply mean more opportunities for the spread of disease. Once a disease develops, however, the outbreak is often associated with the chain, rather than just the store in question (e.g., a foodborne illness outbreak due to a Taco Bell in New York City versus a foodborne illness outbreak due to Taco Bell). Of course, there are also the problems of contaminated food that may be distributed widely between many restaurants--that is a more serious reproach to the food service industry.

"I feel I get the dishes cleanest as other people end up putting dishes away that still clearly have food on them. I'd really be curious to see our kitchen under a black light or something to see whos methods work best."

Obviously, if there are visible food particles on the dishes after cleaning, I would think that the cleaning protocol is not sufficient. That said, the mere absence of visible food particles is not a fail-safe indicator of cleanliness (bacteria, viruses, fungi, etc. can still survive on surfaces even when they appear clean--indeed, there is a significant danger of transmitting foodborne illness from surfaces that appear clean). A good test of your kitchen's sanitation would indeed be to check for the presence of bacteria on cleaned dishware; unfortunately, bacteria themselves do not fluoresce under UV light (bodily fluids do show up under UV light, but not the vast majority of microorganisms), but there are products that have been developed to test hand-washing/surface cleaning effectiveness in conjunction with UV lamps. I leave it to you to determine if the use of such a product is warranted in your case:

http://www.glogerm.com/

"I personally think we could make a fastfood restaurant out of this Taco Bell if we didn't have to work our fingers into these flimpsy gloves, have trouble with seperating wrapping papers, work with the ingredients accurately, etc. And change the gloves every time they rip and our built up sweat comes pooring out of them. I would think if we washed our hands often enough things would be just as well? In the Taco Bell training videos they don't even wear gloves. What do you think?"

Working with gloves is no guarantee of protection, either for the employee or the customer; working without gloves does not necessarily increase the risk of transmitting disease. Sorry to be so circumspect, but it is hard to generalize because so many factors come into play when discussing the issue.

As you rightly note, gloves can decrease your dexterity; gloves that aren't changed regularly become harbors for bacteria as much as any unwashed hand. Hospitals go through tremendous amounts of latex and nitrile gloves because their personnel change gloves after almost every task--and that's precisely how they're supposed to be used. The longer gloves are worn, the more surfaces that one will touch, and the greater risk that the gloves themselves will become contaminated. Additionally, wearing gloves in a restaurant setting perhaps increases the chance that one doesn't wash his hands; rather that go into detail on this point, let me simply point out that surgeons vigorously wash their hands before and after surgery, even though they wear gloves (which are changed regularly) during the entire process. The two must go together to be effective.

Of course, not wearing gloves and relying on hand washing alone has it own obvious drawbacks. People touch their own bodies (faces, clothing, hair, etc.) far more often than they realize, and I can guarantee you that they don't wash their hands after every such contact. Bacteria grow on human  skin quite readily, and readily transfer from skin to surface and back to skin again. The solution to this, which is often something like mandating hand-washing at regular intervals, might fail because of lack of sink space, inconvenience, or apathy. Vigorous enforcement of hand-washing at regular intervals tends to wane over time, like the enforcement of any rule.

What would I recommend? Well, first keep in mind that I might generously be described as in interested amateur, not a food safety expert. The solution might well be to hire a food safety consultant to review restaurant practices; absent that, let me make a few suggestions. Wear gloves for all food preparation tasks, and have instant hand sanitizer stations around the kitchen. Employees should use the sanitizer after they take their gloves off, and wash their hands completely after certain specific situations (i.e., going outside, using the bathroom, handling cleaning materials, handling money, washing dishes). Gloves should be changed whenever somebody leaves or reenters a food preparation area, along with using the hand sanitizer. The downside to this approach is that many gloves and much hand sanitizer are consumed, but the payoff is significant: fewer foodborne illnesses and a generally cleaner kitchen.

James, I wish you the best of luck. You seem like a gentleman who's honestly interested in the health and safety of your customers, and for that you deserve significant credit.