By: Tom Payette, Winemaking Consultant
The positive response from the previous article on Cross-contamination has lead to this article as enforcement to the end goal of the possible elimination of cross-contamination. If that article was not on your reading list over the past few months it may be worth reviewing to help understand why sanitation is extremely important.
Winemakers often say winemaking is 95 percent cleaning. In successful wineries this is very nearly true.
This article will broadly cover the cleaning and sanitation principals that a winery should understand in order to keep the winery facility shiny, new looking and microbe free. Do recall as well that pathogens will not grow in wine so all we are doing is fighting off microbes that may affect the quality, aromas and flavor(s) of your wine.
The first principal to understand is that water is the major cleaning agent one has. The second principal is one must have physical cleanliness before attempting to sanitize or sterilize.
This article will go into detail about how water works, the ways to have physical cleanliness, and how to understand sanitation versus sterilization.
Water (non-chlorinated) can be used to physically clean an area. This can be done by using high-pressure water to remove deposits from the surfaces to be cleaned. The other property of water is that it dilutes and dissolves particles. Water has a low surface tension that makes it physically wrap around particles and carry those particles away from the surface to be cleaned. Water is also used to form steam to sterilize surfaces. As one can conclude – water is a major component and essential for proper microbe management!
The water quality must be proper. If the water contains many minerals or it has properties that do not allow the job to be done correctly – it may not work well and may even damage some of the winery equipment. We often add things to water to help it work better.
One example of this is soda ash. Adding soda ash (sodium carbonate) will raise the pH of the water and further lower the surface tension of the water helping it to perform its cleaning function. Always remember that when using a high ph cleanser with water to follow that action with a low pH rinse water. A common winery low pH solution for this application is a citric acid and water solution.
Equipment such as steamers may be damaged by high mineral loads in the water. As the steamer does the job of creating steam it will boil off pure water leaving behind the minerals. Over time and extended use, these minerals begin to build up causing the steamer to become inefficient.
It is for this reason the author recommends the use of distilled water in winery steaming units to eliminate mineral buildup. It is a small cost when one calculates that it takes about 3 gallons of distilled water, or less, to properly steam two 20-inch cartridge filter and a 12 spout filler. At $0.85 per gallon it will cost a winery roughly $2.55, in distilled water costs, to achieve sterility before bottling.
While pursuing a Food Science Degree, one will study sanitation in great depth. From this we learn that a physically dirty surface cannot be sanitized with sanitizing agents. To understand this, we must understand that a sanitizer reacts on the surface with whatever it comes into contact.
Let’s assume one has cleaned a surface but left behind some dirt that has remained on the surface. While one may achieve a brief moment of cleanliness using a sanitizing agent, it is not properly prepared to receive a grape juice or wine product. The sanitized microbes will slough off the surface of the viable bacteria and expose living bacteria ready to grow! For this reason we want to remove all physical dirt before using a sanitizer.
It is also for this reason that stainless steel has become such a large part of our storage vessels for wineries. Stainless steel is easily cleaned physically and it holds up to chemical cleaners. For this reason – please clean your tanks and enjoy the beauties of stainless steel.
Many chemicals come to mind when we want to clean. Be careful to select the proper chemicals.
Do not use soaps or detergents. Although they are great surfactants [lowers the surface tension of water], they are very difficult to rinse from surfaces due to how they lower the surface tension of the water and often residuals remain. These residuals can cause problems in wines and their flavors. Below are the categories of chemicals that are largely used in the wine business in no particular order.
Quaternary Ammonium is used mostly to clean winery floors and walls although sometimes it is used to clean tanks, hoses and equipment. Modern formulations have made these noncorrosive and heat stable while attacking a very broad range of microbes via disrupting their cell wall resulting in death of the microorganism.
High pH Cleaners
High pH cleaners will give the water a slick feeling. This is the action of the lowering of the surface tension making the water seem soapy. Common examples of high ph cleaners are: TSP (tri-sodium phosphate); soda ash (sodium carbonate); NaOH (sodium hydroxide). High pH cleaners will also kill certain bacteria by disrupting the bacteria’s cell wall. Once the cell wall is disrupted the bacteria may die. As mentioned earlier, if using a high pH cleaner always rinse the same surfaces that came in contact with the high pH cleaner with a low pH cleaner. This will prevent any of the unwanted cleaning agents from being introduced into the wine. A common low pH rinse for this application is a solution of citric acid and water. Be sure to rinse the citric from the same surfaces with just water after using that formulation.
Low pH cleaner
A low ph cleaner will also penetrate the cell wall of some bacteria causing them to die. This action happens at approximately a pH of 2.6. Very few low pH cleaners are used in the wine industry except to rinse away the high pH cleaner, usually with citric acid as mentioned in the paragraph above. Larger wineries may use a phosphoric acid solution for its low pH microbe killing power.
Ozone, a strong oxidizer, has strong killing power when used properly. Many vintners find it helpful when using it with barrels that have had a microbial infection. Most agree that once a barrel has a spoilage microbe inside, it is difficult to completely remove or kill the microbes beneath the surface of the wood cells. Ozone is very effective in killing all microbes when it contacts the microbe. Research and be very careful with Ozone use safety wise.
Commonly used in the wine cellar as an everyday tool, winemakers must realize this chemical does little to sterilize and is limited in its sanitizing power. It should always be used in combination with citric acid, as a cleaning agent, since the lower ph water will increase the effectiveness of the sulfur dioxide thereby releasing more sulfur dioxide in the “free form” to be reactive. Winemakers should continue to use this combination realizing it is just a good practice for everyday cleaning but it is gaining us very little toward true microbe killing power.
Iodine / Chlorine
Both of these are strong oxidizers. Caution is expressed when thinking of using these chemicals since they leave residuals when not handled properly. Chlorine has been discouraged from use in wineries due to the possible link with TCA. Iodine has been used in the past as a sanitizer. Rinsing must be performed diligently since Iodine has a strong aroma that may be detected in minute quantities in wine. The author does not use these and does not recommend their use.
Paracetic Acid (PAA)
Paracetic acid is a strong oxidizer that breaks down into water, oxygen and acetic acid. Its use started in the milk and beer industries and is now starting to be used in the wine industry. Special precautions when handling this strong oxidizer are recommended. For those wanting to explore this option, contact a chemical-cleaning representative for applications to the wine industry.
Hot water is a great tool for many applications of cleaning in the winery. An ample hot water supply is great for cleaning crush equipment, filters and tanks. One area where hot water may cause some problems is with pumps and hoses. It can be very hard on them and cause accelerated deterioration of the impellers in the pumps and discoloration and malformation of hoses.
Steam is an excellent sterilization tool prior to bottling but one must be very careful with its use. Steam is very effective in killing all microbes even below the surface of a possible colony buildup on equipment as discussed above.
Alcohol is a great cleaning/sterilizing agent that will kill microbes that it contacts. Most people purchase Everclear™ and use it directly from the container or with a spray bottle. Research has shown that 100% Everclear™ may actually embalm a bacteria or yeast allowing it to become active later when it is a proper media for growth and regeneration. When using alcohol, blend the Everclear™ with 30% water to make the application more lethal to a larger spectrum of microbes.
Sanitation versus Sterilization
Sanitation is a cleaning operation with a bacteria killing agent that will reduce the microbial population but it may not eliminate the complete bacterial load. This reduction may be enough for product stability at certain points of the production. Sterilization is the complete “kill” of all microbes and it is recommended for the bottling equipment, at bottling, to insure the product will remain bacterially stable.
With proper use of water, high ph cleaners, low ph cleaners, sulfur dioxide, 70% ethanol, steam and a medium grade oxidizer, the author believes great wines can be made, bottled and stored soundly if unsanitary conditions are not allowed to get ahead of the winemaker and the cellar staff. If a certain microbe or microbes are allowed to become established, the winemaker may need to review other more pronounced sanitation measures for several years to come. After several years it is possible to have the winery back to a state where one can go back to the normal sanitation measures. The simple message here: Don’t let your winery get dirty. An ounce of prevention is worth a pound of cure or a little time now will save you a lot of time later. Keep up with your sanitation – it is worth it!