A Tour of Brewery Cleaning & Sanitization by Greg Foss The mechanics: Almost all professional brewers use clean-in-place (CIP) techniques to cut down the work load and make regular cleaning efficient and effective. CIP involves circulating detergent or sanitizer through a spray ball in the top of the kettle (or mash tun, whirlpool, fermentor, bright beer tank, or any other enclosed equipment), pumping it out the bottom drain, and then pumping it back up to the top spray ball. The Principles of Cleaning A cleaning and sanitizing program must address four basic principles of cleaning. These guidelines are very general; every brewer must form his or her own cleaning program based on the the recommendations of equipment manufacturers and chemical suppliers. Detergent concentration Too little detergent might prove ineffective, while too high a concentration can reduce its effectiveness, make it more difficult to rinse, and waste money. No-rinse sanitizers must be properly measured to kill microbes without leaving residue that might alter the end product. Manufacturer recommendations vary considerably, but proper levels of the active ingredient can be tested by the brewer (sodium hydroxide, iodophor, chlorine dioxide, and other commonly used brewing chemicals have test kits available). Time The amount of time a surface is exposed to a cleaner or disinfectant will vary (cleaning encrusted heat exchanger plates with acid will require more time than an acid wash on a fermentor, for example). Too little time yields poor results, while too much time can be redundant or counterproductive. When in doubt, follow recommendations from the product supplier. Temperature Most alkaline cleaners work better at hotter temperatures but can lose effectiveness if used at too high a temperature. Caustics always work more effectively with hot water (generally 130–180 °F [54–82 °C]); non-caustic alkaline cleaners tend to run at temperatures slightly lower than caustics; and disinfectants, as a rule, are used at cold or tepid temperatures. Mechanical agitation Some physical action is required to effectively remove debris, whether that be hand-scubbing or CIP scouring. A small brewery performs a CIP by simply using pumps and hoses to circulate the water and detergent or disinfectant around the equipment for an effective amount of time (anywhere from five minutes to an hour, depending on what works). In larger breweries, the entire process — including chemical additions, cycle times, rinse cycles, and sanitization — is controlled by computer. In either case, the procedure works like a big washing machine, circulating detergent and water power to generate a mechanical scouring effect. Manual cleaning is still a necessity for small parts (clamps and spigots, for example), the outside of the equipment, and the surrounding brewery area. It is occasionally necessary for brewers to climb inside their fermentors and personally scrub them down, but this is a last resort and may indicate that the cleaners aren’t doing a good job. The process: Generally speaking, brewers will clean each time the wort or beer is transferred from a vessel. The kettle, for example, must be cleaned after the wort is boiled and sent off through the heat exchanger and into the fermentor. The basic procedure begins by circulating a cold or tepid prerinse of plain water for 10–20 minutes (hot rinses are not recommended because the heat can bake on debris that otherwise would come off very easily). After prerinsing, the kettle is drained and refilled with a predetermined volume of water, and an alkaline cleanser (usually caustic soda) is introduced. This cleanser is then circulated for 15–30 minutes at a temperature that varies depending on the cleanser (generally between 140 and 180 °F [60 and 82 °C]). Typical Cleaning/Sanitization Procedure 1. Prerinse: Cold or tepid plain water · Removes as much organic soil as possible. 2. Cleaning: Hot water and cleanser (typically, caustic soda) Removes protein by hydrolysis, emulsification, and/or saponification. 3. Acid rinse: Cold or warm water (generally no hotter than 130 °F [54 °C], depending on the manufacturer’s directions) and acid- based solution (typically, phosphoric acid blend) Removes inorganic material (for example, beer stone), neutralizes caustic (if applicable), and possibly passivates stainless steel (nitric acid). 4. Water rinse: Cold water rinse 5. Postrinse sanitation: Tepid water and disinfectant Kills microorganisms (no rinse necessary). A very thorough rinse after this step is absolutely necessary. An acid solution can be used about every third cleaning, following the caustic, to remove the inorganic material and to brighten up the stainless steel. The acid must then be rinsed also. Unless you need to neutralize caustic each time you clean, the frequency required depends on how much beer stone and other deposits you have to contend with. It’s expensive and time-consuming to acid rinse every time if it’s not necessary. Sanitizers come next (except for kettles), but do not need to be rinsed. Note that this is a general cleaning policy, and, as I said earlier, all brewers have their own methods. A different approach to cleaning. One manufacturer of non-caustic cleaners advises a different approach to the cleaning procedure: an acid wash first, then the cleaner. The theory is that noncaustic cleaner leaves a “chemical passivation” that makes it hard for soil to stick to the surface. Generally, however, acids work better after alkaline cleaners. Bright tanks. One chemical company recommends cleaning the bright beer tanks with acid every cleaning and using a caustic only once every five cleanings. The idea is that by the time the beer has reached the bright beer tank, most of the organic soil load should be gone; at this point, the main foe is mineral scale deposits. These deposits can be tackled with the tank cold, which translates to less heat stress on the stainless steel. Phosphoric is the recommended acid cleaner for this job (but hey, it’s your voodoo). Chemicals for Cleaning and Sanitization Safety: A thorough treatment of safety considerations is outside the scope of this article. Suffice it to say, however, that safety is an immensely important subject when dealing with cleaning and sanitization chemicals. Strong acids and alkalis are not user-friendly. Each brewery must develop a very serious safety program in cooperation with its chemical supplier. Three types of chemicals: The types of chemicals used in brewery cleaning can be broken down into three general groups: · Highly alkaline detergents for removal of proteinaceous, organic soil. · Highly acidic cleaners for removal of inorganic soil (water stains and beer stone). · Disinfectants for killing microorganisms. Alkalis, acids, and the function of pH: The bulk of brewery cleaning is accomplished by the actions of alkalis and acids. So how do these different solutions accomplish their tasks? When you wash your dishes at home, you need a detergent (alkali) to break down the grease and dirt and distribute it in the water. Though the dishes get clean, after a while you may notice that your favorite teacup develops a nasty stain. Detergents are limited in the type of substances they can break down, and no matter how hard you scrub that tea stain with soap, it probably won’t come off. A brief soaking in household vinegar, however, will usually remove it; vinegar is acetic acid, a weak monocarboxylic acid. What your detergent couldn’t penetrate, the acid dissolves. This is basically what happens in a brewery (minus the tea). To understand how cleaners work (and to know what you’re sticking your [gloved] hands into), it helps to know something about pH. This article presents a very basic explanation. Any substance with a pH below 7 is considered an acid; anything above 7 is an alkali. The pH scale indicates acid or alkaline strength on a comparative rather than absolute scale, with each number representing a difference of 10 times the adjacent number. A pH of 4 is 10 times more acidic than a 5, for example, and 100 times more acidic than a 6; an 8 is 10 times less alkaline than a 9. The number, however, does not tell the whole story. To say that a solution is acid or alkaline is as meaningless as saying water is hot or cold. On the other hand, if we say water is 145 °F (63 °C), we know how hot it is, even if we do not necessarily know what Fahrenheit means. Similarly, we don’t have to know the exact meaning of the term pH to make determinations about the aggressiveness of acids and alkalis. Talking about the amount of acidity or alkalinity simply refers to a compound’s concentration in solution. Two different solutions with equal amounts of different acids, for example, can have very different pH values. So let’s talk about what these terms really mean. What to Look for in a Detergent In general, look for the following qualities in a detergent you plan to use in your brewery: · Rapid penetration and wetting power. · Ability to control water hardness. · High degree of detergent force for soil removal. · Ability to suspend removed soil and prevent its redeposit on cleaning surfaces. · Easy rinsability. · Noncorrosive to cleaning surfaces. Common Detergent Ingredients Sodium hydroxide: Commonly known as caustic soda, this is the strongest alkaline product available. It is excellent for the saponification of fatty and proteinaceous soils. Its emulsifying and deflocculating properties are fair. It is hard to rinse and is corrosive to some metals. Still, sodium hydroxide is by far the most widely used brewery cleaning chemical. Sodium hydroxide is also capable of being reused, adding cost savings to the equation. Sodium percarbonate: Produced by coating hydrogen peroxide with sodium carbonate, this is one of the primary ingredients in noncaustic cleaners. When combined with water, the hydrogen peroxide generates oxygen bubbles, which aid in loosening debris from the cleaning surface. The hydrogen peroxide may also aid in combatting pathogens. Sodium carbonate: Commonly referred to as soda ash, this moderately strong alkali contributes to the total alkalinity of a cleaning formula. Sodium carbonate is less corrosive than either sodium or potassium hydroxide. It works well with other liquid detergents, but has the major disadvantage of forming calcium carbonate and other insoluble salts in hard water. Silicates: This is another ingredient found in popular noncaustic cleaners. Silicates exist in several crystalline forms with a range of useful properties. Sodium othosilicate works as well as caustic soda as a saponification agent but also displays similar corrosive characteristics toward soft metals. Sodium sequesilicate is lower in alkali content than orthosilicate but is still somewhat aggressive toward soft metals. It does, nonetheless, possess good emulsifying and soil-suspending properties. Sodium metasilicate has very good cleaning properties: It possesses good wetting ability, a high rate of emulsification and deflocculation, and is noncorrosive toward soft metals and skin. On the down side, it has a lower solubility rate and a greater tendency for moisture absorption, which can negatively affect the free-flowing characteristics of the cleaning composition. Phosphates: Phosphates embody all of the qualities that make up a good detergent but are not strong enough to provide saponification. Trisodium phosphate (TSP) has been used in the industry for years because of its good emulsification, dispersion, and wetting qualities. It actually softens water by precipitation, but the precipitate is finely divided and easily rinsed. Polyphosphates possess the same good cleaning ability, but also can modify the behavior of hard water and therefore have many uses as water softeners. Specialty Additives EDTA: EDTA (ethylenediaminetetra acetic acid) is an organic compound based on polycarboxylic acid. It possesses excellent water-conditioning properties at pHs below 11 and has excellent mineral sequestering ability. It is often used in conjunction with caustic soda. Phosphonates: Phosphonates are organic compounds based on phosphonic acid chemistry. They exhibit dispersing, deflocculation, and sequestering abilities. They have excellent stability at high temperatures and high pH. These materials also demonstrate good threshold, or free-rinsing, abilities. Sodium gluconate/glucoheptonate: These organic materials derived from sugar compounds demonstrate excellent water-conditioning abilities at high pH and high temperatures. They are often used in conjunction with sodium hydroxide cleaners. Surfactants: Surfactants are organic materials capable of being manufactured for a broad spectrum of activity. Their properties depend on whether they are considered hydrophobic (water-hating), hydrophilic (water-loving), or both. If the hydrophobic and -philic properties are in balance, the compound will behave more as a detergent. If the compound is more hydrophobic, detergency and water solubility decreases, while emulsifying properties increase. If the compound is more hydrophilic, detergency, solubility, and wetting properties increase. Basically, surfactants are added to increase detergency, produce or restrict foaming, improve penetration, and increase rinsability in cleaning and sanitizing materials. Acids and alkalis are composed of molecules that split up into smaller particles, called ions, when in solution. Ions are atoms or groups of atoms that carry small electrical charges. The process of molecules splitting up (dissociating) into ions is called ionization. Acids owe their acidity to the formation of hydrogen ions (H + ) in water solutions, whereas alkalis have higher concentrations of hydroxyl ions (OH – ). Acids and alkalis ionize to different degrees, a fact that differentiates them in terms of their aggressiveness, or activity. Hydrochloric acid — a strong acid — ionizes about 90%, for example, while acetic acid — a weak acid — ionizes about 2%. Boric acid, an even weaker acid, ionizes only about 0.005%. The relevance of activity is apparent when you realize that hydrochloric acid can dissolve iron or severely burn skin, but boric acid is weak enough to use in eye drops. On the alkali side, caustic soda is so strong it can be corrosive to metals as well as burn skin, whereas sodium bicarbonate can be taken internally. The pH scale describes the degree of ionization (aggressiveness) of the hydrogen or hydroxyl ions present; the lower the pH of an acid or the higher the pH of an alkali, the more aggressive the ionization. Alkalis: The active ingredient in caustic is an active alkali, sodium hydroxide. Its pH is above 8.4. Because caustics are strong corrosives that break down proteinaceous matter into a water-soluble soil, many brewers use them at almost every cleaning. Caustics work best in water temperatures between 130 and 185 °F (54 and 85 °C); check your manufacturer’s recommendations for proper usage. Alternatives to caustic. Caustics have been the work horse of the industry for years. Although these powerful cleaners have a definite place in the meat and dairy industries, where high volumes of protein and fat need to be removed, a growing contingent of brewers thinks that using caustics in the brewery constitutes overkill. Some new products specifically formulated for breweries are now being used with great success as alternatives to the hazards of caustics. Alkaline cleaners are available in many variations, including some that contain silicates, metasilicates, carbonates, and per-carbonates, all of which have a lower pH than caustics. These cleaners are advantageous because they are less harmful to the skin compared with caustics, they can be dumped as waste water without first being tempered (see the box, “Environmental Considerations”), they are less corrosive to soft metals, and they can often be used at lower temperatures. These cleaners are relative newcomers to the brewing marketplace, and their effectiveness compared with sodium hydroxide is a subject of great debate; it often comes down to personal choice (where have I come across that before?). Cleaning Compound Selection Selection of the proper cleaner is dependent on a number of interrelated factors: Type and amount of soil on the cleaning surface. Type of surface to be cleaned. Physical nature of the cleaning compound (liquid or powder). Cleaning method (foaming, CIP, manual cleaning). Water quality. Chemical cost. Time available. Temperature allowance. Acids: Acidic products are effective against inorganic deposits. Acids dissolve and remove water scale (a buildup of calcium and magnesium carbonate), rust (iron oxide), alkaline scale (carbonates and hydroxides that remain after repeated alkaline cleanings), aluminum oxide, and other soils of a mineral or metallic nature. Common Disinfectants and Their Properties The chemicals market offers a myriad of disinfectants from which to choose, and this is typically where brewers get finicky. Most of the brewers that I talked to based their choices on cost, odor, and foaming characteristics. Decisions tend to be strictly personal. Some disinfectants can smell pretty bad, which can get obnoxious in a small brewing area. I personally find iodophors to be offensive to the olfactories, but they are still one of the most common germ killers on the market. Foam is something that people either love or love to hate. The sight of foam coming out the open ports of a fermentor while running a CIP operation gives some brewers a more secure feeling because it means that these port areas are getting contact with the disinfectant (although a simple spray bottle of disinfectant also works well on these areas). The foam lovers generally open up the bottom drain of the fermentor, power out the foam with carbon dioxide, and hope for an adequate floor drain to deal with the aftermath. To those who have smaller breweries with smaller fermentors, foam can be a nightmare to eliminate and may leave enough residue to affect the flavor and smell of the finished product. Common Disinfectants Acid-anionic surfactants: Combinations of acid, usually phosphoric acid, with surface-active agents (surfactants). These disinfectants are stable, odorless, relatively nontoxic, and available in both low-and high-foaming formulas. They are effective at removing and controlling mineral films on stainless while disinfecting, but are effective only below pH 2.5. Chlorine dioxide: This disinfectant works by oxidizing microorganisms. An excellent low-foam sanitizer, it offers a wide spectrum of activity (operates within a large pH range). It can possess good residual effects; that is, any remaining unreacted chlorine dioxide left in the water will continue to sanitize. Once activated, however, the sanitizing will cease when the gas is dissipated. Chlorine dioxide was formerly available only in gas form, but it is now available in liquid form as sodium chlorite. Sodium chlorite needs to be activated with an acid such as a citric or food-grade phosphoric. When the acid is added, the pH is lowered, which destabilizes the solution and turns it into a very aggressive disinfectant. Though a little more expensive, chlorine dioxide is probably the best disinfectant available in terms of activity, odor, and handling, and it creates no foam. One drawback, however, is that once it’s destablized it tends to break down quickly, though it breaks down into very harmless, environmentally friendly substances. This is not the type of disinfectant you can leave sitting around in a bucket all day long (you’ll be left with a bucket of water, baking soda, and salt). lodophor : lodophor is an inexpensive, widely used sanitizer. It typically ranges from 1.6 to 3.5% iodine mixed with nonionic detergents in a phosphoric acid solution, Iodophor can be used as a no-rinse sanitizer at up to 25 ppm; when used at 50 ppm the method of sanitizing becomes chemical oxidation. It is noncorrosive, breaks down slowly, and is available in both low- and high-foaming formulas. It often has a mild odor and can affect beer flavor even in low concentrations. It will stain skin, clothing, and plastic equipment. Peroxyacetic acid: This compound is based on peracetic acid and hydrogen peroxide. Peroxyacetic acid sterilizes by oxidizing microorganisms. Though the acid is low-foaming and offers a wide spectrum of activity, it is often expensive, foul smelling, dangerous, hard to use, and somewhat corrosive. Quaternary ammonium compounds: These compounds sanitize by poisoning or rupturing the cell walls of microorganisms. The spectrum of activity they offer is limited by water hardness and pH (they operate best in a neutral pH environment). They are not widely used because they are dangerous, expensive, and they have a reputation for residue (though they do possess good residual sanitizing ability). Low foam. Sodium hypochlorite (chlorine bleach): A low-cost sanitizer most effective in a weak or neutral pH range. It works by chemically oxidizing microorganisms. Though very inexpensive, it is not widely used in the brewing industry because of its odor and the availability of other less corrosive, less toxic, and more effective sanitizers such as iodophor. Low foam. Acids are not rated in the same way as alkalis. Unlike alkalis, which are rated according to whether they are active or inactive, acids are rated by their mineral-dissolving capability. At pH values above 3.9, the mineral dissolving capability decreases rapidly. Acids such as nitric acid (the most powerful acid used in the brewing industry) exist at 0.5 pH. The bulk of acid cleaning is done with phosphoric acid, or a phosphoric–nitric mix. Some people use a nitric acid wash once a year to passivate their stainless steel, which oxidizes the stainless steel surface enough to form a chromate coating. (It’s sort of like buffing the paint on your car down a coat and applying wax.) Nitric acid is very dangerous, however, and the need for passivation is often debated among brewers. A quick phone call to the equipment manufacturer is always the best solution when in doubt about the care and maintenance of your brewing equipment. Acid-based sanitizers. I have known some brewers who use acid-based sanitizers to help control beer stone. The effectiveness of this practice depends on the hardness of your water, the rinsability of the cleaner, and individual standards for cleanliness. Consumers can choose from several on the market. Make Sure the Chemicals Are Right for Brewing When you’re shopping for chemicals, exercise caution in the marketplace. It pays to shop around. You may notice big price differences for what may amount to the same chemicals under different names. I had to filter through a lot of different, sometimes contradictory information to put this article together. There are almost as many chemical companies as breweries, but they all fall into three categories. The basic manufacturers do just that: they manufacture the raw ingredients. This category includes companies such as Dow Chemical (Midland, Michigan) and Huntington Labs (Huntington, Indiana). Commodity distributors (companies such as Van Waters [Seattle, Washington] and Great Western Chemical [Portland, Oregon]) sell the raw ingredients. Blenders such as Nol-Chem (Portland, Oregon) and Loeffler Chemical Corp. (Atlanta, Georgia) make proprietary blends out of the raw chemical ingredients. These are the companies that sell to the breweries and wineries and to the meat, dairy, and food processing industries. Great Western is an exception, serving both as the manufacturer and the distributor for the Sanichem line. Environmental Considerations Be aware of the effect your brewing can have on your community. Brewing chemicals are corrosive, sometimes toxic, and if untreated they can adjust water pH to unacceptable levels. Their corrosive aspect is easy to understand; caustics and acids both eat away at things like sewage pipes. Consequently, it is a federal offense to dump any liquid with a pH below 5 or above 12.5 down your drain. In some areas, such as where I live in Portland, Oregon, this is monitored and enforced locally (the allowable pH range in Portland is 5.55–11.5). In addition to the harm these chemicals may do to pipes, they could potentially mix with other substances on the way to the treatment plant. Suppose a brewer dumped a large quanity of nitric acid solution, and down the line someone else dumped a cyanide solution; the two chemicals mixed could produce a deadly gas in certain situations. Dumping solutions with extreme pH levels also alters the pH level in your municipal sewage treatment plant. Like most environmental concerns, it comes down to a question of balance. Municipal treatment plants like to keep the pH as close to neutral (pH 7) as possible; big fluctuations in pH upset the balance and can kill the beneficial bacteria that eat away at the waste. Once this happens, everything goes anaerobic, the place starts to stink, and water treatment technicians have to start all over by bringing the pH up or down and introducing more beneficial bacteria. (What most people don’t realize is that the sewage treatment plant is adjusting the pH with caustics and acids!) The real issue with the municipality is cost and time. That being said, most microbreweries are too small to make a difference in the pH at the local treatment center (though it is still important that they abide by dumping laws). Larger breweries may be given a range of water dumping parameters aimed more at governing pH than volume. In other words, the breweries may be given a range of, say, pH 5–9 within which they are allowed to dump, and anything higher or lower must be tempered before it leaves the facility. Caustic must be
