Where There's Smoke, There's Flavor

July 2003

Where Theres Smoke, Theres Flavor

By Kimberly J. DeckerContributing Editor

In the annals of brilliant ideas, it ranks right up with the wheel: Some 400,000 years ago, Homo erectus rubbed two sticks together and lit his first fire. Soon thereafter, our prehistoric ancestors noticed that fires heat not only made a wooly mammoths meat easier to chew, but the smoke seasoned it with a woodsy flavor.

Flash forward a few hundred millennia and humans still toss pork butts into the barbecue, satisfying a universal taste for smoky, flame-cooked flavor thats an artifact of our stick-rubbing past. But lighting up the backyard barbecue can be troublesome, especially if its covered in a foot of snow. Even manufacturers face practical and economic challenges when trying to create fire-cooked flavors via traditional means. Rare is the facility with a competition-grade pit cooker or a smoking shed like grandpas. So instead of summoning the genie out of the bottle the old-fashioned way, smoke is captured in bottles turning the spirit of fire into another ingredient.

The soul of woodWhen wood combusts, it sends its soul to heaven as smoke. But for flavor, the right kind of wood is needed dry, mature hardwoods, such as hickory, apple and mesquite. Green woods and softwoods dripping with resins and saps, such as pine or spruce, are best left in the shed. Their astringent smoke coats the tongue like floor wax and they can give rise to carcinogens, leading USDA to approve less-resinous hardwoods for the production of smoke flavors.

To yield heavenly smoke, wood has to slowly smolder at low temperatures in a closed environment with minimal moisture and oxygen. Red-hot flames actually consume smoke, spitting out carbon dioxide and water neither of which adds flavor.

Once liberated, woods smoky soul plays host to thousands of chemicals that react with foods to yield flavor, color, texture, and the shelf-life protection that historically has made smoke a valued preservative. These chemicals bide their time in woods cellulose, hemicellulose and lignin fractions until pyrolysis sets them free.

Cellulose releases tars, acids and volatiles in smoke. But this glucose polymers main gifts are the carbonyl compounds that react with a foods external proteins to produce tawny colors and a detectable surface bite. Hemicellulose releases some carbonyls, but its more important as smokes primary acid source. By lowering smokes pH, the acids act as natural preservatives, while producing a recognizable tang. By drawing moisture to the surface for evaporation, they help carbonyls tighten the foods texture, too.

Finally, theres lignin, the network of crosslinked phenolic polymers that Patrick Moeller, Ph.D., technical director of functional flavors, Mastertaste, Brentwood, TN, calls the glue that holds wood together. Its phenol units make up the lions share of smokes flavor, protect foods from oxidation and keep bacteria at bay. Theres a lot of press lately about the antibacterial effects of various spices and spice extracts, he notes. If you look closely at what theyre talking about, its typically the phenolic fraction thats doing the work the same kinds of phenols present in smoke, but in different proportions.

The relative weight of phenols, acids and carbonyls in a smoke corresponds to the proportions of lignin, hemicellulose and cellulose in the wood. That depends on the woods species, age and growing conditions. For example, with more lignin than most hardwoods, mesquite smoke trumps its cousins for the amount of flavor-forward phenolics. On the other hand, hardwoods, such as oak, hickory and maple, tend to be more moderate in their levels of lignins, Moeller says. With proportionally more cellulose and hemicellulose, they give you more color and a milder flavor.

Certain woods, like mesquite, are easily distinguished, but labels hyping apple-wood-smoked this or maple-smoked that often amount to so much smoke and mirrors. As Moeller says, You dont get fruit flavor from a fruitwood. If you approach your fireplace and know theres wood burning in there, he asks, Do you know what kind it is just from the smell? Dont expect maple smoke to taste like maple syrup, and if an apple-smoked sausage needs apple flavor, stuff some fruit into the casing.

Barbecuing: smokings kinIf Grandpa were to set a side of pork in his smoking shed at 70º to 90ºF for two weeks, it may come out draped in more smoke than the Tennessee hills, but it wont be ready to eat. The same goes for hams, sausages and anything else similarly cold-smoked, which flavors and preserves foods without fully cooking them. Hot-smoking the pork by raising the shed temperature to between 100º and 190ºF will both smoke and partially cook it after a matter of days. But if Grandpas going to go that far, he might as well go whole-hog and put the pig in the barbecue pit.

For the purist, barbecue isnt a thing, but an event. You cook meat, poultry or fish in the presence of smoke, at a slow pace (half-days, as opposed to half-hours) and with indirect heat that rarely exceeds 300ºF. The heat source is the same hardwoods or hardwoods burnt down to coals that fuels the smoking process. The smoke slowly sinks into the meat. According to Reid Wilkerson, president, McClancy Seasoning Co., Fort Mill, SC: Good barbecue will actually have a band of red around the outside. Thats what we call red-bone barbecue down here, and it happens when that smoke goes all the way into the meat.

For the nonpurist, however, barbecue can be a tomatoey sauce, a seasoning blend or a general spicy-smoky flavor appropriate on everything from chicken wings to pork rinds. While true barbecuers scoff at barbecue from a bottle, even the strictest devotees allow extrinsic seasoning; plenty of purists baste their Q with some sort of paste or rub. Even Wilkerson admits that barbecue needs that extra flavor. Without it, he says, The smoke is just the smoke. And by fully cooking the product, barbecuing makes it immediately edible and introduces yet another collection of savory flavors: the cooked flavors that come from the interaction of proteins, sugars and fats with fire.

The flavor of cookingGrilling, another technique that draws from our flame-fed heritage, accomplishes similar feats, leading many to equate it with barbecuing. But the common threads unravel when examining the two processes closely. Grilling cooks food over direct heat and at temperatures that char the outside quickly while maintaining moisture within vs. barbecues indirect-heat, low-and-slow philosophy.

Then theres the fuel debate. In the official barbecue doctrine, burning logs or charcoal briquettes is sacred, and its heresy to sneak an ignition boost from lighter fluid or replace coals with gas. But neither act merits excommunication from the Church of the Grill. In fact, grilling with gas has grown so much that shipments of gas-fueled grills have exceeded charcoal grill shipments every year since 1995, according to the Hearth, Patio & Barbecue Association, Arlington, VA.

Despite its popularity, gas grilling is not without consequences in terms of flavor. Gas doesnt carry the same woodsy smoke flavor as woodsy smoke. And even with coals or wood chips, the short duration of grilling limits the ability of what little smoke does emerge to penetrate food.

That shifts the spotlight onto the charred-protein and melted-fat flavors grilling generates. Whats happening is that the extreme high heat is producing a char effect on the meat, actually burning the meats fats and proteins, and producing some caramelization, says Wilkerson. So that char flavor you wind up with is really a burnt meat flavor.

But smoke isnt totally absent. When meat cooks on a grill, its juices drip onto the fire below. Those juices, Andrew Bosch, senior creative flavorist, Kraft Food Ingredients Corp. (KFIC), Memphis, TN, explains, which are filled with an unbelievable mixture of fats and proteins and water-soluble materials, hit that flame, and in that instant, that flames so hot that it turns those juices into a smoky vapor that wafts back up and is absorbed into the meat.

Hardwood charcoals send some of their own wood smoke into the meaty vapor; a pan of moistened hardwood chips next to the coals multiplies the effect. With grilling systems, youre seeing more and more people who want to get effects closer to a true smoky barbecue, says Ron Foster, senior food technologist, research and development, Red Arrow Products Company, Manitowoc, WI. To bring the barbecue to the grill, just douse the food with a barbecue sauce that has smoke already built in.

Super-sizing smokeHow do you bring the barbecue to barbecue sauce, or the smoke to smoked almonds? And how do you bring the grill to 500 lbs. of grilled steam-cooked chicken strips? One of the most effective means of cooking is steam, whether in a bag or in a steam oven, explains Bosch. It allows manufacturers to cook very quickly, and it doesnt take a lot of energy. Its cleaner, too witness the tar deposits on an old smokehouses walls, or the carbon crust on a grills grate. Such sediment would take a toll on ductwork, equipment and the factory environment, so its no wonder that manufacturers appreciate steam. Whether from a grill, a smokehouse or a barbecue wood box, smoke poses risks. They have to do with processing safety, with the dangers of dealing with hot fats, with liability, says Lucien Vendôme, senior executive chef at KFIC. And most processors just cannot afford that.

Steams rapidity, efficiency and safety comes at the expense of the deep, rich flavors, colors and textures that develop only with time and specific cooking conditions. Steam cant generate those characteristics, because the moist heat and moderate temperatures inhibit Maillard reactions. As Wilkerson says, You cant take a bag, put a pot roast in it, steam it at low heat and expect it to come out with a smoked flavor unless you introduce smoke into that system.

Foster concludes, You need to bring back the type of flavor that you generated originally, but in a more stable form, so it can withstand what is becoming more-common processing. As Vendôme says: The only way to get that cooked note is through adding it in an ingredient form.

Bottling the genieThe basic recipe for turning pure smoke into an ingredient looks a lot like the method the cavemen used: take wood; add heat. The biggest misconception is that smoke flavors come from some group of guys in white coats mixing up chemicals in the lab, Moeller says. What we do is, in fact, just a more automated and controlled version of what goes on in the smokehouse.

The process begins by collecting hardwood sawdust from furniture, construction, even the production of tool handles. After standardizing the sawdust for size and drying it to a constant moisture, we smolder the sawdust in very controlled-environment furnaces to create the maximum amount of smoke possible, Moeller explains. Channels catch undesirable gases, such as methane, and recycle them as combustion fuel. Meanwhile, the clean, aromatic smoke collects in a condensing chamber, cold mountain water flows through and, in a manner similar to alcohol distillation, the water condenses the smoke and traps it in a versatile, safe and consistent liquid.

Usually, an aging period follows; the smoke liquid rests in stainless steel tanks for several days. During that time, carcinogenic benzopyrene compounds, resins, and tars settle out and await removal via multistage filtration. Also, any remaining heavy oils are recycled for combustion. The process yields a totally natural product.

When speaking of natural smoke flavors, Foster says, its important to realize that were not talking about a chemical reproduction of real smoke. I am often approached at classes and seminars by people who tell me, If you want real smoke flavor, youve got to burn real wood. And theyre correct. Through meticulous control of the wood-burning process, smoke vapor is created and captured in water.

Form and functionThese smoke flavors not only do Grandpa proud they one-up him. We can take that flavor forward, Moeller explains, and refine it, purify it, filter it and change it to make it applicable to any need or use the customer wants.

Atomization, for example, uses pressurized air to force a stream of liquid smoke through nozzles, turning it into a mist. Youre recreating that vapor you originally condensed for use on food, Moeller says. This straightforward process pays off in small but consistent throughput increases typically about 10% to 15% and a smoother, more-stable surface color.

Because these primary liquid smokes arent entirely water-soluble, they require an emulsifier or further refinement to suit them to drenching operations, which shower a products surface with the smoke flavor. Drenching produces a consistent color, texture and flavor, and lets processors upgrade from a batch to a continuous smoking process. That, says Moeller, saves a lot of time, cutting down a traditional smokehouse application cycle from 20 to 45 minutes to about 1.0 to 1.5 minutes.

For applications cured in a nitrite brine, smokes acidity matters more than its water-solubility. The typical pH levels are so low that they chemically reduce nitrites, prohibiting them from participating in crucial curing reactions. So, to keep nitrites effective in a ham or bacon, Moeller says, you need a smoke that is buffered to a pH that doesnt allow those reduction reactions to occur.

Oil-based smokes have a higher pH by virtue of their production, which uses the oil to extract flavor from a liquid smoke, according to Moeller. That allows certain chemical components to transfer such as the relatively oil-soluble phenols while leaving the tangy, less-soluble acids behind. Without that acidic bite, smoke oils are mellower and harmless to nitrites. Their abundant phenols also protect fatty products, such as bacon, from oxidation.

Smoke oils dont have as many color-generating carbonyls as aqueous smokes; that, and their limited binding ability, makes buffered smokes better choices for brined applications. On the other hand, in dried, fermented and aged items sausages and cheeses, for instance oils durability gives it an advantage over aqueous smokes. At reduced levels, an oils milder flavor will register less as smoky than as savory and hammy. In that capacity, Moeller says, an oil-based smoke is used when products have a lot of subtle flavors to enhance instead of mask.

What about placing an oils mild flavor in a dry rub? Oil-based smoke flavors are well-suited for plating onto salt or other dry ingredients for incorporation into seasoning blends and dry rubs, Foster says. Looking for a stronger smoke flavor? Turn a tangier aqueous smoke into a powder. Foster has seen increased interest in topical application of these smoke and grill flavors, and not just in meat or poultry products. Recent trials with dry mesquite smoke imparted wonderful barbecue notes to snack chips, he says.

Moeller cites a smoke-flavored malted barley flour (made by drying the smoke flavor together with the flour) that gives snacks a mild smoky flavor, but also has this malted note, which is a little bit sweet and grain-like. Its very pleasant, and compatible with items like potato chips.

The technologies all point toward increased flexibility in flavor, form and function. There was a time, Foster recalls, when, if you were looking for a product, one of the main questions that a flavor supplier like me would ask is, How are you going to use it? Now suppliers can identify the clients target flavor first, account for the product and processing constraints, and design a flavor system that bridges the gap.

Going in for the grillThe reactions that yield grill flavors enter into more complex territory, being, as Foster explains, more complicated in terms of starting materials vs. finished flavors. Meat on a grill rests above a heat source onto which juices drip. The resulting vapor contains many of the flavors we associate with grilled taste. This process is the basis of modern grill technology, in which we substitute oils for the wood in a smoke-generating system. And although we do not actually burn the oils as we do the wood, we develop the flavor characteristics of outdoor grilling processes. So meats proteins, fats and sugars round out a grilled profile, but dont underestimate the role of fuel. Gas or charcoal, lighter fluid or mesquite: Each leads to a different class of grilled flavor.

Different oils produce different grill flavors. Whether its soybean or sunflower or a soybean-cottonseed blend, Foster notes, different combinations let you create different flavor profiles, such as something that is very strong and distinctive, or maybe more subtle and mild. By combining starting materials, it is possible to create a product with more of a savory note that imparts the flavor of grilled meat or grilled poultry.

Taking things to the next level, flavor artists now create collages of smoked, grilled and barbecue flavors. Weve taken several of our existing grill flavors and blended them with smoke flavors to create some truly unique flavors, Foster says. Weve tried to focus on specific flavors, like a very ashy, hickory-type flavor, or a light mesquite combined with a more refined grill taste. Weve even begun to create the taste profiles of specific types of grilling charcoal grilling vs. gas grilling vs. flame-broiling.

Beyond the backyardProduct developers can apply those effects to products outside the traditional backyard milieu. Beyond the barbecue pit, says Melissa Ventura, CEC, corporate research chef at Red Arrow, hearth-baked or wood-fired ovens lend a distinct and subtle smoke to a variety of foods. Thus, bread has come in for a blast of smoke with smoky malted barley flour. Because its a full-grain flour with sufficient gluten, Moeller adds that it doesnt reduce the doughs protein development. So designers can send a smoke trail through an entire barbecue-themed pizza from the barbecue sauce and smoked mozzarella to the grilled chicken and smoke-scented crust all without lighting a fire.

Since smoke flavors are made from sawdust, vegetarians wont balk at the meaty depth they bring to meat mimics. By using these flavors at low levels, Ventura says, you can achieve a smoked, meaty taste without adding meat.

For example, in a vegetarian-hot-dog formulation, Moeller would probably add smoke oil to the interior portion to get some of the low-level hammy, meaty character. Then, he adds, I would apply a more-typical smoke flavor to the outside to remind me more of what I get from a smoked hot dog made with meat.

Even if the goal isnt to make meat-free meaty, vegetables get a savory boost from smoke and grill flavors. I think that the vegetable category is becoming a very innovative arena, Foster says. A grill-flavor in a shake-on seasoning blend may be all it takes to give vegetables a straight-from-the-fire flavor. Weve done some great work with mesquite smoke in veggie demos that we freeze, thaw, and then steam or just sear on a flattop, he notes. It really does take you outside.

While smokes have shown up in cheese for years, manufacturers have a number of ways of introducing them. You see some smoked cheeses, like Gouda and Provolone, that actually have a smoked rind on the outside, Moeller says. You actually dip a hoop or block of cheese into a liquid and warm it to form that color and skin. But blending smoke oil into the curds spreads a more-pervasive smoked effect.

Imagine the opportunities for improving the standard grilled-cheese sandwich which, technically, isnt grilled. By slipping grill flavor into the cheese, that sandwich would taste as if it were made outdoors over a smoky grill, without your ever setting foot outside, Vendôme points out.

Mining the sandwich scene further, Foster notes the promise grill and smoke flavors show in sandwich spreads: With steam-cooked chicken breasts, you could create a spread that contains a grill or smoke flavor. Adding such a condiment to the chicken or the bread would give it that outdoorsy, grilled taste even in the middle of winter.

Wilkerson has even helped turn the standard Philly cheesesteak into a smoky potato chip: The seasoning was actually a combination of char and smoke flavors, plus pepper and cheese, and a sautéed onion flavor on top. Youd eat one of these things and youd swear you were eating a Philly cheesesteak.

All-American favorites, such as grilled cheese, Philly cheesesteaks and barbecue, dont have a monopoly on the flavor of fire. A subtle but rich mesquite smoke will complement an Indonesian satay or teriyaki marinade, Ventura suggests. And she recommends using a grill-smoke combination to lend to an Argentinean chimichurri marinade the authentic taste of being grilled over a campfire.

Or consider Mexican mole. The true flavor of mole comes from drying its chiles and roasting them over a charcoal-heated surface, says Vendôme. The smoke you get that way is the key element of mole, not the chiles. Its the flavor of cook that makes the mole.

Smoke that isnt smokyIts not necessarily axiomatic that where theres smoke, theres smoke flavor. Moeller says that smoke flavors at low levels become just a savory flavor enhancer.

The reason lies in the generation of subtle, savory-cooked flavors courtesy of the Maillard reaction. Foster explains: When youre creating some of those flavor intermediates, youre recreating or replacing some of the Maillard-reaction products that might not be generated in a rapid cooking process. Enhancing the production of these flavor intermediates is an effective way to improve the overall taste and body of a product.

Thats especially the case if the flavor has a browning component. Increasingly, processors are calling upon smoke flavors as much for color development as for flavor. Moeller notes that when liquid smoke contacts foods, carbonyls react with proteins to form color in the classic Maillard reaction. While the reaction usually gives rise to smoky, browned flavors, by stripping out the smokes phenols the portion responsible for smoke flavor the browning reactions take precedence. A toasty color results from a standard oven roast, minus any heavy smoke.

The new generation of products separate out a lot of these functions to let you tailor the proportions of one component to another, based on what you want to get out of it in the end, Moeller says. A lot of these deli-loaf products (such as smoked turkeys and chickens) have a nice brown surface coating. And a lot of that is done with smoke products that dont carry a very strong smoke flavor.

To bring a golden glow to baked goods, apply a minimum level of low-phenol smoke to the surface. Wash with a bit of whey or other protein to guarantee that the carbonyls have enough proteins to interact with. But Moeller promises a simple bread dough offers enough Maillard-ready protein without any help.

By crosslinking a foods surface proteins, smoke-driven Maillard reactions also help knit together cooked, crispy textures. The difference between the outside of a hot dog and the inside comes about purely because of the presence of the smoke, Moeller says. A hot-dog mixture is initially stuffed into a casing thats removed later. Smoke penetrates casing pores and reacts with surface proteins to form color, flavor and the crosslinked structure of a built-in skin. You can vary the ingredient strength to get more or less skin formation, more or less color formation, and more or less smoke flavor, he says. All of it can now be done, essentially, independently.

Nowadays, flavor technology can achieve flavors and other effects of cook without the cooking that not only match, but sometimes surpass, their role models. As Foster observes, In this industry, the question is always, Can you help me recreate that traditional smoking or slow-barbecue taste? Not long ago, the answer was no. Today, we look to the many advances in technology that have yielded numerous new opportunities to consider. With the genies smoke under control, the consumers wish is our command.

Ronald C. Deis, Ph.D., is the director, product and process development at SPI Polyols, Inc., New Castle, DE. Deis has 20 years of experience in the food industry, both in food ingredients (starches, polyols, high potency sweeteners, bulking agents) and in consumer-product companies (cookies, crackers, soups, sauces). He has been a short-course speaker (polyols, fat replacers) and a freelance writer on a number of food-science-related subjects in food journals, and has contributed chapters on sweeteners and fat replacers for several books.

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