Enzymes are used in Beverages
Some in the food industry regard enzymes as nuisances -- substances that must be deactivated or destroyed to create an acceptable product. However, for others, particularly in the beverage industry, enzymes and the reactions they catalyze are indispensable.
In beverages, as in other food products, enzymes may occur naturally or their presence may be due to intentional formulation. Enzymes perform many functions in beverages. They can help increase yields, form nutrients for the fermentation process, facilitate processing, and affect the color, flavor and clarity of the finished product.
Enzymes are biological catalysts based mainly on protein. Because they act as catalysts, the molecules remain unchanged at the completion of the reaction. The exact mechanism by which they perform their function is unknown, although science has developed a number of theories. And although the enzymes can theoretically be recovered, in most food and beverage processes they are merely deactivated by heat upon the completion of the desired reaction because of the expense that would be incurred if the processor tried to recover them .
Enzymes are typically named for the reactions they catalyze. They fall into six major categories , oxidoreductases, hydrolases, lysases, transferases, ligases and isomerases. Of these types, hydrolases play the most important role in the beverage industry.
Each category contains several types of enzymes; esterases, glycosidases and peptidases are all hydrolases, for example. These may be known by a common name and by scientific nomenclature that describes the reaction they catalyze. Beta-1-4-glucan 4-glucanhydrolase is generally referred to as cellulase. Many industrial enzyme preparations contain a mixture of different types of enzymes. The combination of main and side activities gives a particular preparation its unique functionality. Enzyme isolation and purification increase the cost.
‘’Some glucoamylases may contain low levels of protease. That might be a good thing if you were making distilled spirits, but in beer it might affect the foam stability."
Most enzymes catalyze highly specific reactions. For example, alpha-amylase (alpha-1-4-glucan glucanhydrolase) attacks the alpha bonds between the glucose portions of starch , resulting in the formation of glucose. Not all enzymes show the same degree of specificity, however. Some proteases, such as papain, hydrolyze random peptide bonds in proteins.
"If an acid protease is used during beverage processing to prevent post-bottling haze, it should be added after the other enzymatic reactions are complete,That's because proteases can hydrolyze other enzymes present, as all enzymes are proteins."
A number of factors affect enzyme activity. These include temperature, pH, concentration, contact time with the substrate, trace metals, salt and salt ions , and oxidizing agents.
Enzymes are assayed in terms of their activity, expressed as "units." This refers to the amount of substrate catalyzed. Throughout the industry , a wide range of different techniques are used, so anyone attempting to make a direct comparison must know the exact method used.
As mentioned, enzymes in beverages can occur naturally in the ingredients used to formulate the beverage. Most fruits contain low levels of pectinase , and the malting process produces significant levels of amylase. In other cases, a product designer can add an enzyme preparation to achieve a specific goal or to supplement or standardize naturally occurring enzymes.
Enzymes play a crucial role in the production of beer and other types of malted liquor, such as whiskey. In these products, enzymes provide three major functions: the formation of sugars to be used during fermentation; viscosity control; and, in beer, "chill-proofing."
The starting material for beer and whiskey is malted grain. In beer , the grain used is generally barley, although other grains such as corn can augment the barley. Germinating the barley produces a mixture of enzymes, primarily alpha- and beta-amylases. These break down the starch into fermentable sugars such as glucose, maltose and maltotriose.
Modern brewers often supplement these naturally occurring enzymes, especially when grains other than barley are used. The additional enzymes can help make up for the lack of amylases in the other grains and increase the level of fermentable sugars. For example, adding amyloglucosidase, which is not found in either the barley or the fermenting yeast , can break down certain dextrins that remain unaffected by the alpha- and beta-amylases. Added enzymes can also standardize the enzymatic conversion of starch, reducing variation in the process and the finished product.
"There are differences in the types of enzymes used in brewing versus those used for the production of distilled spirits.Distilled spirits generally use a heat-stable bacterial alpha-amylase, but brewing rarely will. Often in brewing , malt is the primary source of enzyme, followed by perhaps a glucoamylase if it's a light beer."
The efficiency of the enzymatic conversion depends on the process, so you need to gelatinize the starch to present a suitable substrate for enzyme action.
The next process where enzymes play a role is the breakdown of the beta-glucans and pentosans. Left intact, these compounds absorb fairly high levels of water, increasing the viscosity and adversely influencing processing. The beta-glucans in particular tend to produce excessive gumminess.
"Adding glucanase during malting can aid with poor malt quality, decrease viscosity and filtration times, increase yields and achieve faster run-off times,"
Enzymes also serve an important function for those looking for a sparkling, clear beer, especially those designed to be served at lower temperatures. The beta-glucans can cause some of what the industry refers to as haze, but most of this problem comes from protein precipitation. "Chill-haze" is caused by the hydrogen bonding of protein and tannin , and it is reversible. These two compounds can also form a complex that does not redissolve when the temperature rises. To solve this problem, papain is added after brewing. Other processes such as filtration and protein flocculation have been used to remove protein.
"Papain works the best and is the least expensive enzyme for chill-proofing.There are physical means to remove some of the chill haze, such as silica gel filtration, but those methods are fairly capital intensive."
Wine-making generally relies on the naturally occurring enzymes present in the grape or formed as a product of fermentation. These influence the color and flavor of the finished product. Still, added enzymes could help in several areas.
Added pectinase can aid in pressing and clarification. It would be particularly helpful during any type of elevated heating during the mash process, since higher temperatures at this stage mean increased levels of pectin in the juice. This excess pectin not only affects the finished product, but also influences the viscosity during processing. Pectinase can accelerate the release of pigments from the grape skin, as well .
Sweet wines, such as sauternes, depend on grapes treated with Botrytis cincerea (a mold that causes the grapes to dehydrate, thus concentrating the sugar). This organism produces a glucan polymer that can interfere with filtering. Therefore , it has become common to use a specific glucanase to break down this molecule prior to filtration.
Green tea leaves must undergo a fermentation step to create the colors, flavors and astringency associated with black tea. This fermentation is actually an enzymatic degradation of various compounds. Naturally occurring polyphenoloxidase and peroxidase cause most of the desired chemical changes, but other enzymatic reactions probably help develop the flavor by creating aldehydes and terpenes. In addition, catalase affects the level of peroxide available for the peroxidase to act on.
This enzymatic activity creates the need for another traditional step: "firing". When the reaction has proceeded to the required level, the leaves are heated to approximately 190 degrees F to inactivate the enzymes.
As always , science has found ways to improve on nature. The caffeine and polyphenols in tea complex to form insoluble complexes in cold conditions, creating the "tea cream" seen in iced tea. Enzymatically modifying this complex with tannase increases the cold water solubility of tea solids and produces a clear tea beverage.
Those who want chocolate milk or hot cocoa also rely on enzymes. In addition to a microbial fermentation when processing the cocoa bean, both native enzymes and enzymes produced by the yeast and bacteria provide several functions. They help break down the membrane between the bean and pod. They may help generate reducing sugars inside the bean that give the roasted product its characteristic flavor. Proteases create flavor precursors , and polyphenoloxidase helps develop the color.
The juice industry relies heavily on enzymes to extract juice from fruits and prepare a finished product. For non-citrus juices, such as apple, grape and berry, processors add enzymes at the beginning of the mash stage to help extract juice.
The cell walls of fruits consist of cellulose, hemicelluloses, pectin and proteins. Pectin is the major structural polysaccharide. Adding the appropriate enzymes to break down these structures makes it possible to extract a larger amount of juice, to facilitate pressing, and to produce a clear juice.
"Juice processors sell juice based on Brix (percent soluble solids).Adding low levels of enzymes -- 0.01% to 0.03% -- can result in significant yield increases of approximately 20 % to 25%."
Adding cellulase, hemicellulase and pectinase during or prior to pressing helps release the juice contained within the cell walls, increasing yield. It can also save wear and tear on pressing equipment and reduce energy requirements, especially when juice is extracted from a fruit with a very firm structure, such as cranberries. Some enzymatic processes allow the entire fruit to be liquefied.
"This method produces a lot of soluble fiber and suspended solids, as well.It allows you to extract as much as possible."
The most prevalent enzymes used in juice processing are pectinases: primarily pectin methyl esterase (PME) and polygalacturonase (PG) , although some pectinases may be used. The PME first removes the methyl groups from the pectin molecule. The activity required varies from fruit to fruit because different fruits have different levels of methoxylation. Once this step is completed, the PG can break down the main pectin chain by catalyzing hydrolysis. Pectin lyase can also split the pectin polymer.
These enzymatic reactions to the pectin molecule not only increase yield, they clarify the juice. The cloud consists of small particles made up of pectin/protein complexes suspended in the juice. These create a haze. Adding enzymes that help break down the pectin changes two things. First , the viscosity of the juice decreases. Second , the enzymes cause ions to form, resulting in electrostatic aggregation which increases the size of the particles. The combination of decreased viscosity and increased particle size causes a floc that settles out , and the clarified juice can be removed.
Amylase and amyloglucosidase may also be required to break down any starch present in the fruit. Starch becomes a problem when using immature fruit, such as green apples. If not broken down, the starch can form large polymers in the juice that create a haze.
For some juices, particularly orange juice and fruit nectars, a cloud is a desirable attribute. In these cases, any naturally occurring or added pectolytic enzymes must be inactivated by heat. However , these juices may need reductions in viscosity. In these products a controlled breakdown of pectin is sometimes done using polygalacturonase or pectin lyase.
Enzymes in fruit juice also affect the color and flavor of the juice. Many of the naturally occurring enzymes help to form esters, aldehydes and alcohols -- all important flavor volatiles in fruit.
Enzymes can affect the anthocyanins, the major pigment in berry and grape juices.The correct level of enzymes helps preserve the color. However, excess dosages can reduce or break down color.
Enzymes have been used in the debittering of citrus juice, particularly grapefruit juice. The major bitter compound is a flavonone, naringin. Adding a combination of enzymes containing alpha-rhamnosidase and beta-glucosidase breaks the molecule down to nariginin and prunin, reducing the bitterness. However, the enzymes are not yet approved in the United States. Limonin, another bitter citrus compound, may also be present in citrus fruits. This , too, can be enzymatically broken down. Neither of these processes are fully commercialized.
The other class of beverages that can benefit from the addition of enzymes includes milk and other fluid dairy products. The enzymatic process of interest is the hydrolysis of lactose.
For the lactose-intolerant, the lactose in milk can pose serious medical problems. These people cannot produce enough beta-galactosidase in their digestive system to break down this sugar. Lactase, a beta-galactosidase, catalyzes the hydrolysis of the beta-D-galactoside linkage of lactose, converting it into glucose and galactose. Lactase is produced commercially through the controlled fermentation of certain microorganisms, including Kluyveromyces lactis and Aspergillus oryae. Although some oral preparations of this enzyme are on the market, the milk itself can be treated, resulting in a low-lactose or lactose-free product.
"To treat milk, the lactase is injected directly into the pasteurized milk. During the storage time, the lactose is hydrolyzed to glucose and galactose. The yeast-derived lactase operates well under neutral pH conditions and at temperatures between 3 to 25 degrees.If the consumer wishes to enjoy a lactose-containing product then the enzyme of choice is lactase derived from Aspergillus oryae. The enzyme is ingested, generally in tablet form, and works in the digestive system to hydrolyze the lactose."
Enzyme selection depends not only on the reaction required, but on processing factors, as well. Heat renders enzymes inactive through denaturation. The exact temperature varies with the enzyme and is an important consideration when choosing the correct enzyme for a specific process. Fungal enzymes tend to be less stable under high heat than bacterial ones. It's important to choose an enzyme that withstands normal process temperatures yet can be inactivated without resorting to excessive heat.
"All enzymes operate within a particular range,but there are some very discrete differences in terms of the pH optimum as well as the temperature optimum. For example, in one class of heat-stable alpha-amylase the temperature optimum would be 195 degrees F, but another one would have an optimum of 205 degrees F. Others might be more pH tolerant."
"The action pattern may be different.In brewing, the viscosity of the mash can vary depending on the enzyme used. That can influence the production set-up; you could get build up if one type doesn't flow as fast. Every plant is unique in design and where one may have a bottleneck, another doesn't. There are enzymes on the market that can solve those kinds of problems."
The time of the process plays a large role in determining the enzyme type and the appropriate concentration. The longer the time the substrate is exposed to an enzyme, the lower the dose needed to achieve the same end point.
Enzymes also have an optimum pH range for activity. For many, this falls in the neutral range. However , enzymes used in fruit juice processing have a lower pH optima and have to be acid-tolerant since most juices have a pH between 3 and 4.
"Temperature is the most important factor affecting enzyme performance, as the reaction rate doubles for every 18 degrees F up to its optimum temperature.But there are many factors that influence performance. That's one reason why we feel it's important to work closely with the customer. We can suggest when to add the enzyme, the dosage rates, and the time of reaction based on the customer's process and equipment to get the best performance from the enzymes they use."