Most people believe that kitchen countertops made of natural or quartz stone are food safe, mainly because kitchen remodelers and manufacturers claim this as fact. However, these companies have a vested interest in making this claim and does not mean it is true.  As a concerned homeowner, you have a responsibility to look more closely into it.

Quartz countertops are manmade and often come with documentation about the bacteriostatic properties of the product. They are also non-porous, so that bolsters the idea that it is safe for food preparation. However, natural stones such as marble and granite have a certain level of porosity, and do not come with manufacturer warranties about bacteriostatic properties. Are marble and granite countertops food safe?

To answer this question, a researcher at the Hospitality Institute of Technology and Management carried out a study in 2006. The author compared the cleanliness factor of four types of popular stones after cleaning with ordinary household products.  You will find a summary of results of that study below.

Materials

The study looked at four stone kitchen countertops: Cambria quartz (Snowdon), Carrara white marble, local granite from the US, and granite imported from Brazil. The marble and granite countertops had a polished treatment, but had no application of impregnating sealers. The author compared the two granite countertops based on the rate and number of pitting on the surface.

Method

The author carried out the test by inducing contamination of the four surfaces with E. coli bacteria. This common pathogen found in food, especially uncooked meat, can cause serious health problems to humans if ingested.

He cultured a non-toxic variant of E. coli in the laboratory and spread one milliliter of the culture on each one of the kitchen countertops. This replicates the way bacterial contamination from food preparation typically occurs on kitchen countertops, such as when cutting meat.  The author allowed 15 minutes of exposure to the air to dry the bacterial medium.

To clean the countertops, the author readied two regular dishcloths and two stainless steel bowls. He filled one bowl with 2000 ml of tepid clean water, and another bowl of 5 ml of Dawn brand dishwashing soap mixed with 2000 ml of clean water.

He cleaned the countertops by immersing one dishcloth in the Dawn dishwashing soap solution, wringing it out, and wiping the area with the dried culture in a clockwise motion 10 times.  He immersed the cloth in the solution again to rinse it, wrung it out, and wiped the same area again, this time 10 times in a counterclockwise motion. The author then rubbed the surface with a Hydra Sponge for 30 seconds to collect a sample of any microorganisms remaining on the surface.

After collecting the sample, the author took a clean, dry dishcloth and dampened it in the bowl of clean water. He then wiped it on the recently cleaned area to rinse it before collecting another sample using a fresh Hydra Sponge. Finally, the author sprayed the area with a 0.5% white vinegar solution, leaving it for 35 minutes to dry, and collecting a sample using a third Hydra Sponge.

After tagging the sponges, the author left them in an incubator. After 24 hours, he took each one out to count the number of E. coli microorganisms.

Results

Results showed that using a greatly diluted solution of commercially available dishwashing soap to clean the kitchen countertops was enough to reduce the microorganism count to almost the required sanitation level for kitchen countertops of the Food and Drug Administration. The numbers went down even further for all the surfaces after rinsing with regular water well below FDA requirement.  Sanitizing with a very weak solution of white vinegar reduced the count to zero in all the surfaces except for the Brazilian granite, which did exhibit an appreciable reduction in the microorganism count.

Discussion

The author showed that marble, granite, and quartz countertops are safe to use as kitchen countertops because it takes minimal effort to clean them. Using regular, commercially available dishwashing soap and water was all that was necessary to reduce bacterial count to negligible levels for all of the surfaces. Using a weak vinegar solution to sanitize them brought these numbers even further, with the exception of the imported granite.

The study indicates as well that while homeowners can safely use special cleaners for granite and marble, they are not necessary to keep them food safe. However, since they typically serve other functions such as sealing and polishing the stones, it is unlikely to harm anything but the homeowner’s wallet. 

The author speculated on the likely effect of using warm or hot water in cleaning and rinsing the surface. The study used only tepid water and yielded strong results. Using warm or hot water might possibly make sanitizing the surface unnecessary to bring the microorganism levels to zero.

The study also seems to indicate that the porosity of natural stones did not mean it would harbor the growth of bacteria. Both granite and marble exhibited natural pitting on the surface and did not have a seal, but this did not affect the ease of cleaning or food safety of the material.

Homeowners should note that the study used a weak acid to sanitize marble successfully, but this is not recommended for cleaning marble. Marble countertops are very reactive to acids. If you want to sanitize marble countertops, it would be better to use isopropyl alcohol for this purpose.

Conclusion

One of the biggest concerns of homeowners when it comes to granite and marble for kitchen countertops is porosity. They believed that this encouraged the growth of bacteria. The study discussed above shows that this is not true, and that granite and marble, as well as quartz, are food safe and easy to keep that way.

If this has convinced you to take the plunge with granite, marble, or quartz countertops, contact us immediately. Keystone Granite & Tile is can help you in the areas of Columbus, Ohio, Delaware cities, Lancaster and Philadelphia, Pennsylvania.

We are experts at fabricating and installing engineered stone and granite countertops, so you can be confident that you will get the very best in product and service quality.

We have showrooms in Lancaster and Horsham, Pennsylvania as well as New Castle, Delaware and Columbus, Ohio. We will walk you through each slab and explain how each can benefit you in your kitchen or bathroom remodel. If you prefer engineered stones, we also carry the top brands in the industry such as Cambria, Caesarstone, Silestone, and MSI, all with manufacturer warranties.

Once you have chosen your slabs, we provide free professional design consultation and quotes so you know exactly where you are before committing. We also have a quick turnaround, so you will get your products on time and on budget.

Give us a call or send us an inquiry through our website to set the ball rolling!