Brewery Cleaning: Equipment, Procedures, and Troubleshooting

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CH A P T ER

The Fundamentals of Cleaning

1.1 Introduction

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microorganisms may survive a heating step and could reestablish themselves, leading to quality issues.

Brewers realize that they have to clean, but they may well have difficulty deciding on the frequency or selecting the most appropriate cleaning product. To do so, they need to understand the nature of the soils that need to be removed and the factors that influence the ability of the cleaning products to perform correctly.

In addition, they need to know how to measure the effectiveness of the cleaning. Taking the time to consider and understand the basic concepts of cleaning before designing and installing equipment can reduce the chance of having to ask oneself “How am I going to clean this?”

1.2.3 Ensuring Efficient Heat Transfer A soiled surface can reduce the effectiveness of heat transfer, which can lead to increased costs and quality issues. In extreme cases, heat transfer surfaces become so badly fouled that the equipment no longer performs as required. The fouling may require intensive cleaning to restore the equipment back to a usable state, consuming both labor and time.

1.2.4 Ensuring a Quality First Culture There is a need to instill and maintain a quality first culture in any brewery and food-handling facility, because quality in equals quality out. Employees need to embrace this culture—by doing so they are more likely to take pride in their plant and products and less likely to cut corners in procedures. Establishing and maintaining a clean environment is critical to maintaining this mindset.

1.2 Why Clean?

This chapter will start by answering the question “Why do we clean?” There are four main reasons.

1.2.1 Removing Physical Soils Effective cleaning will remove soils from fouled surfaces. If not removed, the soils could fall back into the product, which could lead to quality issues and certainly a poor impression of the product.

1.3 How Is Cleaning Achieved?

There is a term routinely used in this book that describes how cleaning is carried out: cleaning in place (CIP), in contrast to cleaning out of place (COP).

CIP is a means to clean the equipment and fittings in place without having to remove them. For a thorough discussion of CIP systems, see chapter 4. COP is when equipment and fittings have to be removed to be cleaned.

1.2.2 Removing Microbes and Beer Spoilers Soils can harbor undesirable bacteria and yeast. Simply heating a soiled surface to kill the microorganisms is not an effective process. Some 1

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1.4 What Is a Clean Surface?

A clean surface can be defined as one that is free from residual films, soils, taints, and microorganisms.

Although this definition is often strictly applied, it is rarely achieved in practice. Residual films, soils, and taints can often be seen or smelled but are often hard to quantify. However, acceptable levels of microbiological contamination can be defined. For example, acceptable levels of colony forming units (CFUs) for swab samples encountered during a CIP could be ●● ●● ●●

before cleaning, >106 CFU/100 cm2 cleaned and rinsed, 102 CFU/100 cm2 sanitized, <1 CFU/100 cm2

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The factors can be divided into two groups: those that brewers have control over and others that are largely beyond their control. Brewers have the ability to influence the type of cleaning product and its concentration, the temperature and the time of application, plus the amount of mechanical action achieved. However, the types of soil, the water chemistry, the surface type and finish, and the mode of application are a function of the brewery location, the styles of beer being made, the brewery design, and the equipment. After a brewery has been built, the brewer has less ability to influence or control these factors.

The factors over which the brewer has control are interdependent and are often displayed as the so-called Sinner (or Sinnersche) circle (Fig. 1.1).

Thus, the expectation is that the sanitizer reduces the number of CFUs on cleaned surfaces by 100-fold.

For routine sampling, rinse samples are often preferred for microbiological testing because they are considered to be more representative of the entire tank surface. Swabs, on the other hand, are better suited for detecting areas that are difficult to clean, such as under the lip of the manway door (which can create cleaning shadows). Acceptable standards for swabs and rinses can be defined differently. For example, an acceptable standard for “sanitized” for a swab sample could be defined as <2 CFU/100 cm2 but for a rinse sample as <1 CFU/100 mL. Having defined what is clean, it is now appropriate to consider the factors that influence the cleaning results.

1.5 Factors Affecting Cleaning The most significant factors that affect cleaning are summarized in Table 1.1.

FIGURE 1.1. The Sinner cycle. (Courtesy R. J. Rench—

© MBAA)

TABLE 1.1. Factors affecting cleaninga Factors within the control of the brewer ●● ●● ●●

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The type of detergent selected and its concentration The temperature of the cleaning solutions The time that the cleaning solutions are in contact with the soils The degree of mechanical action achieved in the cleaning

a Courtesy

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Factors beyond the control of the brewer ●● ●● ●● ●●

The types of soil that have to be removed The water chemistry The surface type and finish The mode of application

Diversey—Reproduced by permission.

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The circle is named after Herbert Sinner, who was the former head of detergent application and engineering at the company Henkel. If one of the four factors in the Sinner cycle is reduced, it may be compensated for by an increase in one or more of the other three. The relationships between the factors are not directly proportional; for example, halving the concentration may not necessarily be compensated for by doubling the contact time. Let us consider all of the factors in more detail.

1.5.1 Detergent Concentration Establishing and maintaining the concentration of a detergent at the desired level is fundamental for achieving a consistent cleaning. Generally, the reaction rate, depending on the reaction mechanism, increases with the concentration of the detergent.

Formulated detergents are designed to perform best within a designated range. There tends to be an optimal concentration; for example, 3% caustic (sodium hydroxide, NaOH) is effective in removing most organic soils. There is no advantage to using higher than designated concentrations. In fact, cleaning costs will be increased, and more water may be needed to remove the detergent at the end of the cleaning. This can increase effluent charges as well.

1.5.2 Temperature The temperature can influence how well a surface is cleaned. For caustic-based detergents, raising the temperature by approximately 10°C (18°F) will double the rate of reactions. There tends to be a limit to this rule of thumb—at temperatures above 65–70°C (149–158°F) there is no further cleaning benefit. Temperatures higher than 65–70°C can help kill microbes; this is useful if the detergent cannot be in direct contact with the microbes. However, some of the components of the detergent may break down at high temperatures, making them less effective. In addition, high temperatures can result in premature deterioration of gasket materials, creating areas that can harbor microbes and also result in leaks. Regular exposure to high temperatures in the presence of ions such as chloride can cause significant corrosion in stainless steel.

Acidic detergents are usually designed to work at ambient temperature. There may be a benefit in cleaning at 25–30°C (77–86°F) compared with 10–15°C

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(50–59°F), but higher temperatures may be detrimental.

In some formulations, components may become insoluble and thus exhibit reduced effectiveness at higher temperatures. However, when acidic products are used for removing scale, higher temperatures, such as 50–60°C (122–140°F), may accelerate the rate of descaling. For best results, users should follow the instructions detailed in the technical data sheets provided by the supplier of the chemical.

Rinsing of vessels can be enhanced by using ambienttemperature water rather than cold water, particularly when trying to remove caustic detergents. In addition, care must be taken when rinsing with cool water after a hot wash. Many tanks have been badly damaged due to the creation of a vacuum when a hot solution is followed by a cold solution. Not only should antivacuum breakers be fitted and functioning on a tank, but many brewers will clean with the manway door cracked and able to open.

1.5.3 Time Reducing cleaning times can help increase the productivity of a plant and reduce operational costs.

However, it is important to allow sufficient time for the chemicals to work effectively. This will depend on the soil load, temperature, concentration, and degree of mechanical action. For most applications, a chemical contact time of between 20 and 60 min is sufficient to remove the majority of organic soils. Longer times may be necessary when trying to remove scale (descaling) or to remove odors from tanks that have contained products with added flavors. When descaling a surface, additional time and descaling agent may be required because the descaling agent reacts with the scale and the concentration decreases over time.

1.5.4 Mechanical Action Mechanical action refers to the shearing force of a solution across the surface. A cleaner surface is obtained with greater shearing action. In a vessel, high impingement helps physically lift soils that are attached to a surface. In a pipe a slightly different situation exists. For liquid flowing in a pipe, three zones can be identified (Fig. 1.2).

The area closest to the pipe surface is called the boundary or streamline zone, where there is little or The Fundamentals of Cleaning

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no flow. Next to the boundary layer is the transition zone, where there is laminar flow with some mixing.

The turbulent zone is in the center of the pipe, where contents are well mixed and there is substantial shearing action. These concepts are well understood in fluid dynamics.

Effective cleaning requires turbulent flow at the walls of the pipe. The thickness of the boundary layer is related to the flow rate (Timperley and Lawson 1981). As the flow rate increases, the thickness of the boundary layer decreases (Fig. 1.3). In addition, the laminar flow rate next to the boundary layer is related to the mean flow rate in the pipe (Fig. 1.4).

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The boundary layer becomes thinnest when the flow rate reaches approximately 1.5 m/s (5 ft/s). As the boundary layer becomes thinner it is easier for the chemicals to reach the soil on the surface of the pipe. In addition, the velocity at the edge of the boundary layer increases proportionately with the mean velocity in the pipe, as illustrated in Figure 1.4. Soils sticking out of the boundary layer experience greater shear forces. Thus, by achieving a flow rate of 1.5 m/s, turbulent flow is achieved through most of the pipe, and the cleaning action is enhanced through mechanical and chemical action.

If pipes are not cleaned properly, then they accumulate soils that harbor and protect microbes.

FIGURE 1.2. Flow layers in a pipe. (Courtesy R. J. Rench—© MBAA)

FIGURE 1.3. Thickness of the boundary layer at different flow rates in two pipes of different diameter. (Adapted from Timperley and Lawson, 1981. Courtesy R. J. Rench— © MBAA)

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FIGURE 1.4. Relationship between the velocity at the pipe surface and the mean velocity in pipes of different diameters.

(Adapted from Timperley and Lawson, 1981. Courtesy R. J. Rench—© MBAA)

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In addition, in the absence of good cleaning action, biofilms (a group of microorganisms that stick to each other and surfaces, often within exuded extracellular polymeric substances, rather like a slime) may form, and these can be difficult to remove. Thus, it is important when designing equipment to verify the flow rate that will be generated during CIP.

FIGURE 1.5. The formation of a dipeptide. (Courtesy Diverseyâ&#x20AC;&#x201D;Reproduced by permission)

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1.5.5 Types of Soil to Be Removed What is the nature of the soil, and where has it come from? If we know that then we can select the most appropriate product to remove it. Typically, soils encountered in a brewery are organic, inorganic, or a combination of the two. Organic matter is derived from the malt, hops, and yeast and is composed of proteins, carbohydrates, and possibly fats, plus complex reaction products. Inorganic material is derived from the water, added salts, and ions such as phosphates derived from the malt.

Proteins are large, complex biomolecules comprising one or more chains of amino acids linked through amide bonds, and they perform a vast array of functions in a living cell (Fig. 1.5). Acids and alkalis can hydrolyze the amide bonds (reintroduce water), creating smaller molecules that are more soluble in water. Oxidizing agents react with proteins and break them down to smaller molecules.

Carbohydrates such as starch are large, complex biomolecules composed of long chains of simple sugars linked through glycosidic bonds (Fig. 1.6). Acids and alkalis can hydrolyze the glycosidic bond, creating smaller molecules that are more soluble in water.

FIGURE 1.6. The structures of simple sugars and more complex carbohydrates. (Courtesy Diverseyâ&#x20AC;&#x201D;Reproduced by permission)

The Fundamentals of Cleaning

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Soils with fats are probably less of an issue in breweries compared with other food-producing facilities, because the fat content of the main ingredients, malt and hops, is low. Fats are complex molecules composed of longchain fatty-acid esters and glycerol. Alkalis can disperse fats and hydrolyze them, resulting in smaller molecules that are more soluble in water. Surfactants (described in chapter 2, section 2.7) can emulsify fats (break them into smaller droplets), which will enhance the ability of the alkali to solubilize the soil.

In the malting and brewing process, complex products are created as a result of the Maillard reaction (Fig. 1.7). The reaction starts during malt kilning and continues in the brewhouse until wort cooling. The reaction requires the presence of heat, sugars, and amino acids and is responsible for color and flavor development. The initial product created is an amino carbonyl product, but following molecular rearrangement, further reactions can occur and create more complex molecules. Some of these products form hard scales that are difficult to remove during cleaning.

Usually, hot alkaline solutions with plenty of mechanical action are required to remove these soils.

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1.5.6 Water Chemistry and Quality Water not only is a fundamental component of beer but also plays a key role in the type of beer being produced. Traditionally, before water chemistry was understood, breweries were located at places where the water quality lent itself to producing beer of a certain style. In other instances, if a source of good potable water was plentiful, then entrepreneurs would build a brewery at that site and produce beers for the local community.

After water chemistry was understood, brewers were able to adjust the ionic composition to produce a range of beer styles using one source of water.

Water is the largest component not only of beer but also of the cleaning solutions. Water can play a significant role in the type of soils formed. The water brings in dissolved solids, and their composition depends on the source of the water. Some of the ions that make up the dissolved solids are Ca2+, Mg2+, Na+, Cl–, SO42–, and HCO–3 .

Water hardness is caused by dissolved calcium and magnesium ions. The calcium and magnesium ions can form insoluble precipitates such as carbonate, sulfate,

FIGURE 1.7. The Maillard reaction. (Courtesy Diversey—Reproduced by permission)

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