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Cleaning and Sanitation
Cleaning Detergents
There are literally hundreds of detergent mixtures available that are specifically tailored to the needs of the brewer. A detergent must be capable of wetting surface(s) to allow it to penetrate the soil deposits and to thus act more quickly and efficiently. The detergent must have the capacity to break the soil into fine particles and to hold them in suspension so that they do not redeposit on the cleaned surface. Detergents also must have good sequestering power to keep calcium and magnesium salts (beerstone) in solution. There are two types of cleaning detergents: alkaline or acid that are often formulated with surfactants, chelating agents, and emulsifiers to enhance the effectiveness of the detergents. The most effective detergents in the brewery today are formulated with alkaline solutions that have chelators and surfactants.
Acid Detergents
The use of acid detergents is commonly restricted to the removal of beerstone, water scale (calcium and magnesium carbonates), and aluminum oxide. Tannins, hop oils, resins, and glucans are unaffected by acids. Acid detergents are more effective against bacteria than are alkaline detergents (34). The two most common types of acid detergents are phosphoric and nitric.
Nitric Acid: Nitric acid not only is used to remove beerstone and other inorganic deposits, it also has biocidal properties when used either as a pure acid or in more stable, less hazardous mixtures with phosphoric acid (2). In addition, nitric acid attacks protein. Nitric acid offers the added benefit of inducing a passivating effect on stainless steel by forming a protective layer of chromium oxide on the surface to prevent the leaching of iron ions into the beer.
Phosphoric Acid: Phosphoric acid is used widely as the basis of acid cleaning materials, those that find their greatest application in the removal of beerstone and similar deposits on surfaces such as protein material resins and yeasts. Its performance is greatly enhanced by adding an acid-stable surfactant, which promotes penetration of surface deposits and also assists in the process of rinsing at the end of the cleaning process. Phosphoric acid is not effective in removing beerstone until it reaches 16ºC. However, some brewers believe it lacks the strength to remove preexisting beerstone and is better at removing organic deposits. It often is used at a concentration between 2 and 3% w/v phosphoric acid for cleaning. Small quantities of complex organic acids are often added to enhance its effectiveness.
Alkaline Detergents
Alkaline detergents are most effective in removing organic soils, i.e., oils, fats, proteins, starches, and carbohydrates encountered in brewing. Alkaline detergents work by hydrolyzing peptide bonds and breaking down large, insoluble proteins into small, more easily soluble polypeptides. In general, cleaning problems associated with organic soils can be avoided by ensuring that prerinsing is carried out with the minimum of delay and by using cold water prerinses at low pressure (38). Alkaline detergents will not remove calcium oxalate and other inorganic compounds that lead to a buildup of beerstone.
Some of the more common alkalis are sodium hydroxide, sodium percarbonate, sodium hydrogen carbonate, sodium orthosilicate, and sodium metasilicate.
Sodium Hydroxide: Of the cleaning agents, sodium hydroxide (NaOH), otherwise known as caustic soda, is widely used in breweries worldwide. Its effectiveness in dissolving proteinaceous soils and fatty oils by saphonification is virtually unsurpassed. This makes it a natural choice for cleaning sludge off the bottoms of boilers and for cleaning beer kegs. Sodium hydroxide is an acutely excellent emulsifier. It is unrivaled in its ability to dissolve protein and organic matter if used in conjunction with chlorine, surfactants, and chelating agents.
Additives
Surfactants, chelating agents, and emulsifiers often are added to enhance the effectiveness of detergents.
Surfactants: Surfactants (wetting agents) are a large group of synthetic organic compounds that reduce the surface tension of water to increase the penetration of cleaning solutions.
There are three main groups of surfactants: anionic, nonionic, and cationic. All three groups have both high- and low-foaming qualities. The anionic types are negatively charged surfactants that have excellent wetting and dispersing qualities. They are most commonly used in detergent formulations, the most important being sulfated alcohols and alkyl aryl sulphonates such as Teepol®. The nonionic agents are neutral charge surfactants that principally are used in high-pressure systems. Nonionic agents are the workhorses of the brewing industry and are well-suited for use in conditions where solutions are subjected to high pressure. Both anionic and nonionic detergents have very good wetting, dispersing, and rinsing powers; but they are of little use, unaided, against most brewery deposits. The cationic wetting agents are positively charged and have the poorest detergent qualities of the group, but they do demonstrate good bactericidal action. As a result, they are used far more widely as sanitizers than as wetting agents.
Chelating Agents: Chelating agents (sequestrants) are chemicals that are incorporated into the detergent formulation and that prevent scale buildup, i.e., the precipitation of calcium and magnesium salts onto equipment surfaces. The chelating agent is purchased either as part of a proprietary formulation or as an additive for blending. Commonly used sequestrants are EDTA (ethylene diamine tetra-acetic acid), NTA (nitrilo-tri-acetic acid), ADPA (aceto diphosphonic acid), sodium gluconate, and sodium tripolyphosphate.
Chelating agents exhibit different chelating power, and so manufacturers of brewery detergents often formulate detergents for specific tasks. The makeup of the additives also can differ, depending on their physical form; powdered detergents tend to contain polyphosphates, and liquids often contain gluconic acid.
Emulsifiers: Emulsification is a measure of a detergent’s ability to break down fats and oils into smaller units that are removed more easily during rinsing. Polyphosphates function as emulsifying and dispersing agents, which are important in dispersing proteins. The phosphates also have a water-softening effect and help prevent corrosive action of alkalis.
Phosphates are employed widely in the formulation of alkaline detergents for use in brewery processing applications. Phosphates are divided broadly into two classes: the orthophosphates and the condensed or complex phosphates.
The most widely used of the orthophosphates is trisodium phosphate (TSP), which is a good soil remover and emulsifier. It is very effective in softening water by precipitation, producing an easily rinsed nonadherent precipitate. TSP is hard on the skin, so rubber gloves should be worn while using it.
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