Enzymes and Cultures
by Lori Dahm
While use in cheesemaking continues, other applications are beginning to expand.
The use of cultures and enzymes in the dairy industry is by no means new — combinations of enzymes and cultures are often used in cheese production to foster proper flavor development and to help reduce aging times. This continues to be an integral aspect of cheese manufacturing in the United States for desired efficiency in cheese production.
What is new is the use of enzymes and cultures in an expanded repertoire of dairy applications, such as fluid milk products to help eliminate spoilage and extend shelf life; whey fractionation; and reduced-lactose dairy products. And finally, the use of certain cultures as prebiotic or probiotic strains is starting to become more widespread.
While the use of enzymes and cultures in cheese production continues to be a foundation of cheese science in the United States, the use of these live microorganisms is being expanded into other applications both within dairy and outside of dairy, where they are proving to have even wider benefits.
In today’s traditional manufacturing processes, cheese is produced when starter cultures are added to milk in order to begin fermenting the lactose into lactic acid and begin digesting and breaking down the milk protein casein. Typical enzymes used as starter cultures are proteases and peptidases, which drive acidification and also coagulate the milk, at which time cheese flavor begins naturally developing.
But the manufacturing pressures that currently face cheese producers call for the addition of adjunct cultures to yield faster ripening times. Several cultures are used for this purpose.
“When adjunct cultures are used to accelerate cheese flavor development and reduce aging times, the strains that are chosen contain protease, aminopeptidase and in some cases, esterase enzymes,” says Terri Rexroat, market and product manager of cultures and enzymes at Cargill Texturing Solutions, Waukesha, Wis. “These provide the best flavor ‘package’ for most flavorful cheese varieties.”
Accelerated cheese ripening requires that cheese flavor development be sped along by the addition of adjunct cultures so that the desired flavor is realized faster than it would be without their addition.
“When these protease and aminopeptidase enzymes are released by the bacterial cells, they allow for faster development of the types of flavors desired in that cheese, and they also help prevent the development of undesirable off-flavors such as bitterness,” Rexroat says. “These enzymes break down bitter peptides into flavor compounds, which in turn helps to reduce bitterness and accelerate cheese flavor development.”
Shortening the cheese aging period by accelerating flavor development and thereby accelerating the ripening of the cheese also helps manufacturers reduce cheese storage costs. But certain varieties of cheese are better candidates for this process than others.
“The cheese varieties that are the best candidates for accelerated flavor development are those that are aged for extended periods, like over six months,” Rexroat says. “These include cheddar and related varieties such as parmesan-type and Swiss cheese. Mild-flavored cheeses or unaged cheeses such as mozzarella are not good candidates.”
Much work has been spearheaded in the world of cheddar cheese flavor by Dr. Mary Anne Drake, associate professor of food science at the Department of Food Science at the Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, N.C.
The flavor profiles of cheddar cheese can vary widely, and in 2001 Drake developed a comprehensive “cheddar cheese lexicon” that identifies and describes each of the flavor compounds of cheddar cheese. This lexicon has been a useful tool to quantify and document the different flavor effects upon cheddar cheese that result from factors such as region, manufacturer, levels of fat, micoflora and age.
Cheddar cheese that has been aged a significant amount of time develops a nutty flavor that consumers find most pleasing in this variety of cheese, and the latest project with Drake’s lexicon studied whether the use of adjunct cultures could help younger cheddar cheeses develop this desirable nutty flavor.
Drake worked with Don McMahon and Jeff Broadbent of the Western Dairy Center at Utah State University, Logan, Utah, on the Nutty Flavor Development project. When a particular strain of Lactococcus lactis was used as an adjunct culture in cheddar cheese manufacturing, the resulting cheese did have an increased nutty flavor, even after less ripening time, and beefy/brothy notes, were fostered by higher ripening temperatures.
How enzymes and cultures can affect flavor development goes hand in hand with reducing aging times, since the addition of the adjunct cultures affects the overall ripening process and resulting flavor. Cheese manufacturers today choose a package that will work throughout the life cycle of the cheese development to appropriately develop the desired flavor balance.
“The enzymes used to develop cheese flavor are basically the same as those used to accelerate cheese flavor development — aminopeptidases and proteases,” Rexroat says. “In cheese varieties that benefit from fruity flavor compounds such as parmesan, bacteria with strong esterase enzyme activity will be beneficial. In some cases, combining strains with different types of enzyme activity can provide a synergistic benefit to cheese flavor.”
These adjunct cultures are added to the fluid milk at the initial stages of cheese production at the same time that the acid-producing cultures are added. They are activated after the acid-producing cultures begin fermenting the milk, and technical experts recommend that several trials runs be conducted to determine the exact package of enzymes and cultures necessary for desired flavor and targeted ripening effects.
Keeping It Fresh
One of the areas of excitement in the dairy world with regard to the use of enzymes and cultures is their use in fluid milk products to prevent spoilage, sometimes in place of additives and preservatives.
“Fluid milk and other fresh products such as yogurt and sour cream can benefit from the use of cultures that produce substances called bacteriocins, which are metabolites that are naturally produced by the cells,” Rexroat says. “They inhibit the growth of certain specific types of bacteria, which is desirable if those bacteria are pathogens or spoilage organisms.”
This is particularly of interest in the world of organic dairy products.
“We are expanding our line of DURAFresh, all-natural fresh-keeping products to include products that will be certified organic. The basis for the DURAFresh technology is controlled fermentation using proprietary cultures and a patented process,” says Doug Allen, commercial director of dairy at Kerry Bio-Science, Hoffman Estates, Ill. “The process results in naturally produced acids and metabolites that are effective in controlling spoilage organisms.”
DURAFresh is a spray-dried powder that is added to a variety of products.
The use of cultures can possibly extend shelf life in optimal conditions, and the use of these cultures and the resulting metabolites have the potential to replace chemical preservatives. But again, choosing cultures carefully is important for a successful end application.
“The types of spoilage bacteria or pathogenic bacteria that are killed by such cultures vary by type of bacteria. Some species in the lactic acid bacteria family such as Lactococcus, Leuconostoc and Pediococcus are especially useful producers of bacteriocins,” Rexroat says. “The bacteriocin-containing culture can either be added as a live culture or as attenuated (inactivated) cells that are useful because of the bacteriocins that they produced when they were alive.”
These developments are rapidly becoming more important and topical in today’s market where consumers want fresh, natural and organic dairy products.
“The demand for organic products and the ingredients that go into them will continue to increase,” Allen says. “There will be greater scrutiny over the ingredients used in organic products, and having an all-natural and organic ingredient to help products maintain freshness is of significant value.”
How Sweet It Is
One of the enzymes most frequently used in dairy applications is lactase, because its sensory effect is one of sweetness that is useful in certain products such as yogurt, and also because it breaks down the milk sugars into digestible components for the lactose-intolerant consumers.
“The use of lactase is growing, primarily because of its use to make reduced lactose products such as fluid milk, or even yogurt,” Rexroat says. “The sales of lactose-reduced fluid milk are growing due to increased availability of products, in tandem with increased awareness of these products.”
Awareness of lactose intolerance is increasing for several reasons. For one, it is now understood that as humans age, the body’s ability to digest the milk sugar lactose disappears of natural accord.
In addition, lactose intolerance is common to several ethnicities, and as these segments of the population in the United States grow larger and become more substantial in purchasing power, products that are formulated to help with lactose intolerance are being rapidly introduced to market.
“Lactose-reduced milks continue to grow in volume versus declines in other milk categories. The whole area of lactose reductions in dairy products fits in well with the ‘health and wellness’ trend as it opens up the consumption of dairy products to a large segment of the population,” Allen says. “We can see processors building designer milk beverages combining lactose reduction with our ‘healthy’ ingredients.”
Whey Relevance
And finally, the big area of the future for dairy ingredients — whey — is also a factor in the use of enzymes. Treating whey with enzymes has been standard in the dairy industry for several years.
“Enzymes can be used to hydrolyze whey so that it has different functional properties and different nutritional properties,” says K.J. Burrington, director of dairy applications at the Wisconsin Center for Dairy Research, Madison, Wis. “When whey protein is hydrolyzed, some of the smaller peptides are split from the protein molecule, which changes the way the protein binds water and also provides better heat stability.”
In addition to changing the functional properties of whey, treating whey with enzymes also changes the nutritional attributes of the ingredient.
“Treating whey with enzymes breaks the protein into different components, which changes the digestibility of the protein with the idea that it is more readily absorbed in the body,” Burrington says. “Hydrolyzed whey proteins are used in weightlifting supplements because of this association. But hydrolyzed whey proteins can become bitter, and although some companies have their own propriety technology to reduce that bitterness by cleaving the protein molecule at specific points, most still have bitterness.”
For that reason, usually the level of hydrolysis for commercial whey protein ingredients is relatively low, such as 5 percent or 10 percent, unless the product is being used for medical situations such as tube feeding of surgical patients in the hospital.
Although treating the whey sugar lactose with enzymes is less common, this process also has a purpose.
“The technology to treat whey to convert the lactose into glucose and galactose has been around for some time,” Allen says. “The resulting whey syrup can be used as a partial replacement for sweeteners in products like ice cream and yogurt, and if sweetener costs begin to increase, this technology may become more important and more practical from a cost-benefit standpoint.”
The enzymes used to hydrolyze whey into different components are typically protease and pepidases. While whey protein ingredients are starting to become valued, the lactose has yet to find its mirrored market niche. However, new enzyme technology is being used to convert the lactose into higher priced prebiotics, which might be the opportunity for lactose to find market value as an ingredient.
All told, enzymes and cultures use continue to be important in the dairy industry, and their use is being expanded and further developed on multiple fronts: for whey conversion, for shelf life optimization and for accelerated cheese ripening and flavor development.  
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