CHAPTER 1
BREWING QUALITY OVERVIEW

Overview. Bonesaw Brewing Co. Glassboro, NJ.

Photo: Naomi Hampson.

We wrote this book to help you better understand, appreciate, and apply the science behind the materials and processes of making beer. The better your grasp of brewing science, the more dependably you will be able to make delicious beer, and the more reliably you will be able to devise new beers to meet changing consumer preferences. So what is beer? How does beer differ from its fermented beverage brethren? The US legal definition is given in Section 19.3: "Flavored Malt Beverages"; a commercial definition encompasses the wide variety of products that are included in beer marketing, but in a book on brewing science, we will use a scientific definition. Beer is an alcoholic beverage derived from a source of starch without concentrating the alcohol content. "Derived from" covers a complex series of interacting steps, each of which influences the character of the final product and is ultimately the focus of this book. Brewing beer differs from fermentation of wine in that for brewing, a source of starch must first be converted into fermentable sugars. The brewer is responsible for management and control of all steps of the brewing process to produce a beer of reliable and reproducible quality.

There are four main ingredients in beer: water, malt, hops, and yeast. If randomly combined, these four ingredients might turn into an alcoholic beverage of questionable quality, but in this chemical process, the brewer is like a catalyst, a substance that guides and speeds up a reaction. Mastering the science of raw materials and the process steps of beer production is essential to making quality beer. We will start with a broad overview of the brewing process followed by a scientific history of beer and the scientific method. In learning how to conduct an experiment, you will begin to understand the process of troubleshooting problems in the brewery. Finally, as our major goal is to brew beer of excellent quality and consistency, we will discuss beer quality as defined in several contexts. Each of these topics will be discussed further in depth in the chapters that follow.

1.1 INGREDIENTS

In addition to the main ingredients, beer may be brewed with adjuncts and processing aids. Adjuncts are sources of starch or sugar other than malt. Processing aids are materials used to help give the beer desirable characteristics. Some common processing aids are filtration media, finings, carbon dioxide, foam enhancers, and coloring materials. In this overview, we will touch upon the main four ingredients. Adjuncts and processing aids are covered in later chapters.

Water

Beer is usually more than 90% water. Beer production can take as much as 12 volumes of water to make 1 volume of beer. Some breweries have been able to cut this ratio to three or less. Less water means less energy use, less wastewater for disposal, and less negative impact on the environment. Pure water is a characterless compound of fixed composition. It is supplied to breweries as a mixture with many components present in trace amounts. The nature and concentrations of these trace components are important to the character and quality of the beer. Water is usually modified to adjust the trace components. Water that is to be made into beer is sometimes called brewing liquor. Chapter 4 discusses brewing water in detail.

Malt

Brewing beer requires starch, which is usually derived from cereal grain. Malt is prepared from seeds of cereal grain by steeping (soaking in water), germinating, and drying. The malting process produces enzymes that convert starch to fermentable sugars. The most common grain for malting is barley (Hordeum vulgare), but wheat, rye, and oats can also be malted. Rice and maize (corn) can also be used as sources of starch for brewing but require special treatment. Since medieval times, malting has been a separate craft from brewing, requiring specialized facilities. Nonetheless, brewers need a basic understanding of the malting process to fully understand and apply malt as a raw material. Malt and malting will be discussed in Chapter 5.

Hops

The hop (Humulus lupulus) is a climbing plant, more specifically a bine. The fruits of the hop plant, hops, are boiled with the beer wort to provide bitterness and other flavors. Hops may also be added to the fermenter in a process called dry hopping. Hop compounds provide an antibacterial effect to help preserve the beer. There are many varieties of hops with different flavor profiles, as well as advanced hop products that can be easier to use than natural hops. Chapter 6 provides details about hops and their processing.

Yeast

Yeast is a single-cell fungus that converts sugar to ethanol and carbon dioxide. The action of yeast on sugar is fermentation. Most beer fermentation is carried out by one of two species of yeast: Saccharomyces pastorianus, used for lager beer, and Saccharomyces cerevisiae, used for ale. Some specialty beer styles are fermented with Brettanomyces bruxellensis, Brettanomyces lambicus, or related species. Within a particular yeast species, there are many variations, called strains. The species and strain of yeast affects the flavor and character of the beer. Yeast may be cultivated at the brewery or pitched directly from wet or dry commercial products. Processes and practices involving yeast are covered in detail in Chapters 10 and 11.

1.2 BREWING OVERVIEW

A graphical overview of the brewing process is provided in Figure 1.1. In brief:

• Malt and other grains are crushed in the mill. Crushed grain is called grist.
• The grist is loaded into the grist case until mashing.
• The grist is mixed with hot water in the premasher on its way into the mash tun.
• In the mash tun, enzymes from the malt cause the starch in the grist to be converted to soluble extract, which contains sugars that the yeast can ferment.
• The solution of extract, called wort, is separated from the remaining grist particles in the lauter tun. Extract that sticks to the particles is washed out with hot water in a process called sparging.

  Figure 1.1 Overview of the brewing process in a four-vessel brewhouse.

  Source: Drawing: Marcy Barth.

• The clear wort is boiled in the kettle. Hops are added.
• The remains of the hops and solids that form during boiling (hot break or trub) are removed in the whirlpool.
• The clear, boiling-hot wort is cooled in a heat exchanger called the wort chiller.
• During knockout, oxygen and yeast are added to the cool wort while it is pumped into a fermenter.
• After several days to more than a month of fermentation and conditioning, the yeast is removed from the beer, and the beer is pumped into the bright beer tank. Separation of yeast and solids may be facilitated by special equipment such as a centrifuge or filter. Carbon dioxide is added under pressure to provide the characteristic lively mouthfeel.
• The beer is served directly from the tank or packaged into secondary containers.

A summary of the duration and temperature ranges for each step in the brewing process is provided in Table 1.1. This table represents a general summary and overview; different breweries using different equipment and brewing different styles of beer may have quite different programs.

Milling

Malt is delivered to breweries in bulk (loose in a truck or rail car), in super sacks, or in bags. Malt must be milled, that is, crushed into small pieces to expose the starch, before it is used for brewing. Crushed grain is called grist. The device that performs the operation is a mill (Figure 1.2). The primary purpose of milling is to allow starch from the grain, enzymes from malt, and water to come into contact during the mashing step. A seed of grain is protected by a water-resistant seed coat, and a woody shell called the hull. Milling splits the hull, breaks open the seed coat, and crushes the interior of the seed, producing additional surfaces where water can react with starch. Milling details affect the character of the beer and the efficiency of the process. It is preferred that the malt hulls be split but not pulverized because they will be needed to aid wort separation later in the process.

TABLE 1.1 Brewing Steps, Durations, and Temperatures