Fine-Tuning Cheese Performance

January 5, 2006

15 Min Read
Fine-Tuning Cheese Performance

Fine-Tuning Cheese Performance

By Kimberlee J. Burrington
Contributing Editor

For those of us who love cheese, it canadd almost as many benefits to a food application as there are cheese varieties.Think of your favorite pizza with the slightly toasted color, buttery flavor,chewy texture and stretch of the mozzarella cheese still warm from the oven. Alfredo sauce would just be white sauce without the textureand flavor of Parmesan cheese. Fried cheese curds without the right meltcharacteristics would just be an empty fried shell. These are just a few of the applications that use the uniquefunctionalities, like meltability, shredability, sliceability, stretch, browningand flavor, that can be built into either a natural or process cheese product.

Cheese technology basics

Inbasic terms, cheese making is a concentration process. But it is far more thanjust a means to remove water from milk and concentrate the casein and fat. Theskilled hands of cheese-makers bring a tremendous diversity in how cheeses taste,melt, stretch, shred and slice, or whether they are hard, soft, brittle orcrumbly. It is the cheese-making process, mainly acid development by the addedstarter culture and the activity of added or native enzymes, as well asmicroorganisms, that create these characteristics.

Cheese making begins by the coagulation of the casein, themain protein in milk. Most varieties of cheese use rennet to clot the milk,but some cheeses use heat and acid (ricotta) or just acid (cottage cheese).Water, or serum, and fat are trapped in the developing mesh or network ofcasein. After the coagulum, or curd, is formed, it is cut into small pieces andthe casein network tighten and pushes the serum out to form the whey. Heatingand acid development by the starter bacteria greatly facilitate this process.After cheese-makers remove the whey, they eventually salt, then press, the curdsinto compact forms and age the product for a specific period of time to developspecific flavor and body characteristics. Cheese making, or curd manipulation, is a relatively simpleprocess.

However, it involves very complex and precise manipulations ofthe casein molecules in order for a cheese to have the desired physical orfunctional properties demanded by the consumer, especially those who wish to usethe cheese in baking. “Whether a cheese softens, flows or even stretches whenheated, or has a rough mouth-feel, is brittle, or even if it is white ortranslucent after baking, it is all about controlling casein chemistry (theinteractions of casein molecules),” says Mark Johnson, Ph.D., senior researcher, Wisconsin Centerfor Dairy Research, Madison.

The degree to which casein molecules are physically separated(the fat and moisture content of cheese) or prevented from interacting (throughcasein chemistry) determine the desired body — the firmness and smoothness —texture, and physical properties, such as melt and stretch, of the final cheese.Casein chemistry may be manipulated by the cheese-maker through strategic controlover the extent of acid development that is allowed to occur at key steps in themanufacturing process. It involves the loss of calcium from the casein and thepH of the cheese. The calcium loss from the casein increases the flow or melt ofthe cheese, but if the pH is allowed to drop too far the cheese will not flowwhen heated. Also involved is the proteolysis that occurs during the ageingprocess. Proteolysis, the breakdown of the casein molecules into smaller piecescalled peptides, might take weeks to be sufficient to influence the melt, (e.g.,it increases the melt, softens and makes the cheese less chewy and smoother).This is caused by the activity of the rennet, microorganisms and enzymesnaturally present in the milk. There are many ways to modify the functionality of natural cheese through thechemistry just described. Process and product limitations are described in the standardsof identity for natural cheese that can be found in Title 21 of the Code ofFederal Regulations (CFR), Section 133.

Culture effects

Cultures aremultifunctional ingredients in cheese. They metabolize lactose to produce energyand lactic acid, provide flavor development, contribute to cheese texture, aidmilk coagulation, and provide moisture control. In general, mesophilic cultures,like Lactococci startercultures, convert lactose to lactic acid at optimum temperatures from 86°F to90°F. Thermophilic cultures, like Steptococcusthermophilus and Lactobacillussp.,convert lactose into lactic acid and galactose at optimum temperatures from98.6°F to 112°F. Many thermophiles are unable to metabolize galactose, whichcan later create cheese defects.

Flavor development occurs by protein breakdown into peptides,amino acids, amines and ammonia. Other common flavor compounds — diacetyl,lactic acid, propionic acid and acetic acid — form during the breakdown. Texture development is a function of protein breakdown, pH andmoisture. Cultures for mozzarella or provolone type cheeses consist ofprimarily S. thermophilis for fast acidformation. Addition of a Lactobacillus willadd flavor and accelerate ripening. Lacto bacilluscasei or Leuconostoc willprovide buttery notes. Swiss-type cheese will use an S.thermophilus for acid production and possibly combinedwith a Lactococcus.Propionibacteria develop the eyes and add some flavors.

Lactobacillus helveticus providessome flavor and removes the residual sugars during pressing. Lactobacilluscasei and Lactobacillushelveticus are examples of nonstarter lactic-acidbacteria (NSLABs). NSLAB are the bacteria normally present in a cheese plant andcan cause the characteristic flavor fingerprint of that plant.

Manufacturers use adjunct cultures for different cheeses toproduce similar characteristics. “Lactobacillushelviticus will form ethyl esters due to synthesis bylipases and esterases, which develops into a fruity flavor in Cheddar or aParmesan cheese,” says David McCoy, Ph.D., principal scientist, Chr. Hansen,Milwaukee, WI. “Monterey Jack and feta can utilize the same acid-producingcultures, but their make procedures are different so the final cheeses are verydifferent.” The pH at draw and the final pH of the cheese help determine someof those differences.

Adjuncts can also control bitterness in aged cheeses. Adjunctcultures can accelerate flavor development or contribute additional flavors tocheese as it ages, depending on the make procedure and adjunct type. Somecultures used as adjuncts are “attenuated” to reduce acidification whilepreserving flavor-development properties. Addition of selected lactose-negativeor protease-negative cultures to aging cheese will increase the rate of flavordevelopment and reduce the amount of bitter peptides.

Modified meltability

Meltabilityis one characteristic that has been designed into many cheese types, but themost well known is mozzarella. When a cheese like mozzarella melts, several distinct phasesoccur. “When cheese is first put into an oven, the cheese temperature increases, but the shape does notchange,” says Carol Chen, researcher, Wisconsin Center for Dairy Research. “Oncethe cheese reaches a critical temperature called the softening point, it beginsto flow and change shape. The cheese matrix collapses and becomes one semisolidmass. The last critical point the cheese reaches in its melt profile is thecomplete melt point.” After this point, height changes are minimal and cheesetemperatures eventually reach the oven temperature. Cheese-melt properties are acombination of the decrease in height of the cheese and the actual cheesetemperature, and are quantified as a melt-profile analysis. A melt curve hasthree regions of change occurring in the cheese: softening region, flow regionand complete melt.

In the softening region, the cheese temperature increases, butthe cheese doesn’t physically change much or flow. Softening temperature is agood indicator of melted cheese structural strength. The flow region describesthe extent the cheese flows, which can predict if a cheese will melt and flowoff the edge of a pizza. Cheese-flow rates relate to the ability of caseincaseininteractions to relax and reform. After two to six weeks, mozzarella functionality stabilizes.

The pH of the cheese is related to meltability. “The higherthe pH of the cheese, the higher the softening temperature and lower the amountof flow results,” says Chen. “Softening and flow characteristics, combinedwith composition and degree of proteolysis, affect the stretch, free-oil releaseand chewiness or hardness of melted cheese,” she says. Stretch is a characteristic of melted cheese thatmakes eating pizza more fun and results from casein-casein interactions that are broken and quickly reformed. Acombination of a high concentration of intact casein within a narrow range ofcolloidal calcium phosphate provides a good stretch.

Put through the shredder

“ForAmerican cheeses, like Cheddar, firmness and fractureability are the bestpredictors of shreddability,” says Chen. “Firmness and adhesiveness are thebest predictors for mozzarella and pizza cheese.” Shreddability typicallyimproves as firmness increases and adhesiveness decreases. Mozzarella tends tobe less firm and more adhesive than American cheeses. It is typically shreddedafter a minimum of one week of aging. Colder cheese temperatures at shreddingmeans that the cheese is firmer, which helps shreddability. A colder cheese temperature does not mean the cheese is lessadhesive, though. Shred appearance is also important and has characteristicsthat can be quantified. Shred size and shred-size distribution — measured asthe percentage of long shreds — in a sample are quantifiable attributes thatcontribute to consumer acceptance of a pizza.

Shred appearance and melt are not necessarily related; goodshreddability does not necessarily mean good meltability. “Generally, we findthat consumers prefer finer (fancy) shreds on fruit and green salads and thickershreds on heartier salads, such as pasta and potato, as well as baked dishes,such as lasagnas, pizzas or enchiladas,” says Barbara Gannon, vice president, communications, SargentoFoods Inc., Plymouth, WI. “Fine shreds are also ideal for quick-meltapplications, such as microwave usage and cheese toppings that will be addedafter the food is heated so that the hot food will melt the cheese withoutadditional cooking.” Furthermore, “applications for cold use, such asslices and shreds, use natural cheese and those that require a melt with stretchalso tend to gravitate toward natural cheese,” she says.

Dialing-up browning

Browning istypically a desirable property for baked cheese. “The browning of cheeses likemozzarella during baking is due to the Maillard reaction, a heat-inducedreaction between sugars and protein,” says Chen. The intensity of the browningdepends on the lactose and galactose content of the cheese and the ability ofthe free-amino groups to remain hydrated during baking. However, excessive browning creates a problem for cheeses likemozzarella, pizza cheese or Parmesan.

The desire for less browning in pizza cheese is often drivenby pizzerias that use impinger ovens. Impingers expose the cheese to very hightemperatures (550°F) for six minutes or more, which stresses the cheese andcreates a much greater degree of browning than would occur in a conventionalhome oven. “In the case of mozzarella or pizza cheese, browning comes from thesplitting of the lactose into glucose and galactose by thermophilic cultures,”says Dean Sommer, cheese applications specialist, Wisconsin Center for DairyResearch. “The cultures will continue to metabolize the glucose, butthey won’t metabolize the galactose as readily. Galactose, being a more-powerful reducing sugar, willaccentuate the browning of the cheese during baking.” Typically, cheese-makers will fortify the cheesemilk withnon-fat dried milk (NFDM) or condensed skim to increase the solids and overallprotein in the milk to increase yield.

These ingredients used for fortification also contain asubstantial amount of lactose, which in turn increases the galactose levels inthe cheese and even greater browning issues. Often, cheese-makers try to useshorter make times, like three to four hours “in an effort to reduceproduction time and cost, but shorter make times will lead to a less-completefermentation of lactose, so the overall concentrations of lactose in the cheesewill be higher, and greater browning will still occur,” says Sommer.

Many solutions help to decrease browning in pizza cheese.Technologies to reduce lactose, such as using ultrafiltered milk forfortification instead of NFDM or condensed skim, are a good start. Ultra-filteredmilk has much less lactose, but does have the proteins that the cheese-makerswant. Longer make times, like five to six hours, “will allow for amore-complete fermentation of the lactose and reduce browning,” adds Sommer.Washing the curd will help remove residual galactose, which will decreasebrowning. Selecting a culture that provides a more complete fermentationwill also help reduce browning. Any one of these modifications will reducebrowning, but when used in combination, greater decreases in browning mightoccur.

Parmesan browning is a negative attribute for the dry Parmesanin the shaker can, as well as for Parmesan table cheese when it is baked. BlockParmesan cheese has about 36% moisture while “dry Parmesan is typically about18% moisture and, when it is exposed to warm temperatures, over time, itgradually browns or becomes darker in color in the container,” says Sommer.Not only is the color less appealing, but sweet, and caramel flavors will alsodevelop, which are not typical Parmesan flavors that a consumer expects.

The causes of browning in Parmesan are similar to pizzacheese. Usually, the root of the problem is incomplete fermentation of lactose.Parmesan will sometimes have uneven browning when it is shredded or grated as atopping. “The cause of the uneven browning is due to the varyinglevels of lactose breakdown and metabolism on the inside of cheese wheel, versusthe rind or the outside of the wheel,” says Sommer. Parmesan is brined after it is formed. The brine is kept cold so, when the cheese wheel sits in thebrine, the outside of the cheese gets colder faster than the inside. The coldtemperatures will reduce the fermentation occurring toward the outside of thewheel. The salt, as it penetrates the cheese, causes a loss of moisture, whichfurther inhibits the fermentation process. Brining Parmesan immediately afterthe wheel is formed will exaggerate this variation in browning throughout thecheese. The solutions for reducing browning in pizza cheese can also be appliedto Parmesan.

Process-cheese technology

Controllingcheese functionality is the cornerstone of process-cheese technology. Process cheese represents a range of products with specificstandards and allowable ingredients that are listed in 21 CFR, Sections 133.169to 133.180 (available online at www.access.gpo.gov/nara/cfr/waisidx/21cfr133_99.html) underthe main categories of pasteurized process cheese, pasteurized process cheesefood and pasteurized process cheese spread. “Process cheese representedbreakthrough technology in 1915 when J. L. Kraft successfully marketed hisAmerican- Cheddar process-cheese tins,” says Jim Wild, senior businessmanager, Kraft Food Ingredients, Memphis, TN. “Innovation continues a centurylater as KFIC offers food processors a line of specialty process cheesesdeveloped to deliver flavor and functionality at an economically advantagedprice point compared to standard of identity process cheeses.” Furthermore,“flexibility in formulation allows for unique product features in thespecialty line ranging from melt restriction to high-impact bases,” he says. Though some of us cheese lovers prefer the taste and textureof natural cheese, there are reasons for selecting a processed cheese over anatural cheese in a food application. “In general, processing conditions andstorage can have a greater impact on natural cheeses than process cheeses,”says Jill Norcross, associate principle scientist, Kraft FoodIngredients. “The flavor and body of natural cheese continues to develop withage. Processors who can’t consume natural cheese within a short timeframe willface inconsistencies in their finished products,” she adds. Formulating withnatural cheese can offer some functional challenges. “Natural cheeses do not lend themselves readily to smooth,silky sauces and fillings,” she continues, “Emulsification and/or processingexpertise must be applied to natural cheese to prevent oiling-off in theseapplications. Process cheeses contain significant amounts of natural cheese,but the resultant textural characteristics are quite different from naturalcheese.”

“Process cheese is homogeneous, provides a more-uniformmelt, and has improved keeping quality throughout the recommended shelf life,”she notes.

Like the chemistry of natural cheese, the chemistry of processcheese is quite complex. Fortunately for formulators, certain companies haveinvested a lot into the chemistry and formulation of process-cheese products. Afood formulator only has to provide some knowledge of the application, processand desired cheese functionality in order to get a process-cheese ingredientthat works for them. “There continue to be opportunities for developers tolearn advantages of using process cheese as an ingredient,” says Wild. “Some of the key advantages include: increased functionality, multiple cheese varieties, consistentflavor and texture over an extended shelf life.”

Many factors contribute to the overall functionality ofprocess-cheese formulations. “Key to the formulation approach is theemulsifying salt selection,” says Gannon. With various emulsifiers, the scientist canformulate a product that has a high degree of melt, or one that ismelt-restrictive. “Generally, higher-melt formulations use sodium phosphateand/or sodium citrate emulsifiers, whereas melt-restricted formulations usehexa-metaphosphate or pyrophosphates. Firmness is impacted by the amount ofsolids, hydrocolloid selection, fat content, and other components. Flavordelivery can be modified based on dairy-component selection, cheese type and/orage and additional flavoring agents,” she adds. Standards of identity forprocess cheese allows for greater flexibility than natural cheese, and hence theability to further-modify formulas to meet consumers’ needs. “High-flavoredprocess cheeses used at low levels are more desirable in systems that sustainthermal abuse,” says Norcross. “Additionally, combinations of KFIC’sspecialty process cheeses and highly flavored cheese powders create uniquesolutions for customers,” she adds.

“With lower-cheese formulations, such as dips,enzyme-modified cheeses (EMCs) are frequently used to boost cheese-flavorimpact, and is an excellent way to boost overall cheese flavor while controllingcosts,” says Gannon.

“Flavor improvements in process cheese have come fromdevelopment of EMCs with stronger and more-intense flavors with a balance ofproteolytic and lipolytic character. Better delivery systems like EMC powderswith different release mechanisms, such as encapsulation, have also providedflavor improvements to process-cheese products. Other developments in blends offlavor compounds and enzyme-modified dairy ingredients have also madeimprovements,” says Nachi Adaikalavan, director of marketing, dairy flavorsand process cheese industry, Chr. Hansen. Adding these flavor systems at different stages of themanufacture can also change the impact of the flavor. Before, flavors were always added in the cooker with all theother ingredients, but the high cook temperatures often destroyed much of theflavor. Now, adding flavors inline can minimize heat damage and flavorloss.

“Acceptance of process-cheese products has been mostsuccessful through educational and promotional programs that highlight value andconvenience,” says Wild.

Future developments

The futureof cheese looks promising. “We expect growth in the natural cheese category to bedriven by continued interest in ethnic and specialty cheeses, as a reflection ofconsumers’ broader experiences and demographics,” says Mary Taylor, business manager, Kraft Food Ingredients.“In response to these interests, KFIC recently introduced a natural Italiancheese blend of Asiago, Parmesan and Romano.” Flavorful, high-impact artisan cheese blends helpmanufacturers “achieve productivity goals without sacrificing quality andtaste,” she adds.

“Growth in process cheese will continue as more developersbecome aware of its versatility, increased cost stability, consistency,efficiencies in handling and extended shelf life as compared to natural cheese,”says Wild. Food formulators can look forward to formulating with better-tastingand highly functional cheeses in years to come.

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