A bit foolish and slightly chilled. That`s how I`m feeling, seated on a plane bound for Tennessee, with a 10-ounce, 230-calorie package of Benihana Oriental Style Shrimp with Rice squeezed between my back and the seat. I forgot to take it out of the freezer last night, and I`m helping it thaw, belatedly following the instruction of Lars Reimann, who agreed to let me visit his lab and look in as his chemists churn it, burn it, boil it, dehydrate it, even digest samples of it with acid.
Why? Because I had finally been made curious by a nagging refrain:
”Under 300 calories.” This claim appears again and again on all kinds of so-called gourmet frozen entrees. In our weight-conscious, diet-crazy society, the word ”calorie” is ever-present, so commonly used it`s taken for granted. Many of us probably know that calories represent the available energy in food and that our bodies burn them or store this unmetabolized energy as fat.
(Conservation of energy and all that.) But how many of us know how calories are counted? Reimann invited me to his lab to find out.
Reimann is director of Woodson-Tenent Laboratories Inc., one of the more prominent of a couple dozen labs that apply the methods and equipment of analytical chemistry to food products. Labs like his have been more in demand since a 1969 White House Conference on Food, Nutrition and Health led to more comprehensive labels on many food products. (The U.S. Department of Agriculture (USDA), incidentally, has authority over products containing at least 2 percent cooked or 3 percent uncooked meat or poultry. The Food and Drug Administration (FDA) oversees all other foods.) Some big food companies such as Con Agra, makers of the Morton and Banquet frozen dinners, do their own nutritional analyses, but most send their products out for analysis, as does Benihana, which taps Woodson-Tenent. What they get in return is a kind of nutritional box score, a percentage breakdown including such key components as carbohydrates, fat and protein, and, generally, a calorie count.
Thousands upon thousands of calories are toted up daily in private labs like Woodson-Tenent`s, which is located on the outskirts of downtown Memphis in an unmemorable earth-toned building frequently brightened at curbside by colorful air-freight vans dropping off everything from apple strudel to ziti. Reimann greets me wearing a dazzlingly white, crisply starched lab coat, his name stitched in blue letters over the left breast pocket. His office, too, seems straight out of Central Casting. The wall to the left of his desk is covered with a periodic chart of the elements, and his bookshelves contain both a microscope and balance.
Reimann accepts the now unfrozen, $2.79 package of Benihana Oriental Style Shrimp (which, incidentally, is not sold in the Chicago area) a bit like a quarterback handed a new football. The photo of the entree, boxed not much bigger than a paperback novel, shows a mound of shrimp, some green peppers and peas, a couple water chestnuts and a drizzling of white sauce-all atop rice. Especially now, just short of noon, the meal looks pretty good.
It looks considerably less appetizing a few minutes later, after he walks it down to the lab and Rosie Webber, a ”sample preparation person,” cuts open the two ”microwavable” boilable pouches, empties everything into the huge, 10-cup bowl of the largest Cuisinart made-and then flicks the switch. In seconds all is baby food, a thin, pale-green mush. Still, the machine churns on.
”It must be perfectly homogenized,” says Reimann over the noise. When the blade stops whirling, he outlines the work to come. Different tiny portions of this mush, each deemed representative of the entire product, will be attacked differently. From this lab will come a determination of the moisture content and a fat analysis. Cramped work quarters, nothing more, shift the remaining tests to a sister lab in Des Moines. There, other technicians will pinpoint protein content, also ash and fiber. Carbohydrate content will be figured indirectly, in effect the odd man out, after subtracting all these percentages. First, though, Reimann calls on a lipid chemist named Linda Littlejohn.
”We add about two grams of the sample to each of these tin dishes, fold them up and weigh them,” she says, starting in on the moisture, or water determination. Each dish is about the size of a Mason jar lid. Littlejohn literally presses them into service. After dabbing each with a small blob of the mixture, she carefully crimps them into sealed half moons. Why two samples? As a check against inadvertent error, she says, recording Sample A as 2.3060 grams and Sample B as 2.1082 grams. ”Now we put them in a vacuum oven at 98 degrees Centigrade (208.4 degrees Fahrenheit) for about five hours, and then afterward, transfer them to a desiccator till they cool. Then we weigh each sample again, and the (before-and-after) difference in weight is the amount of moisture that`s been removed,” she says.
Reimann points to an adjacent piece of equipment about the size of a microwave oven and explains that inside are moisture-absorbing silica crystals. ”If you simply removed the samples from the oven, they might re-absorb moisture, as much as 1 percent relative moisture from the air, as they returned to room temperature,” he says.
With the minute samples of the shrimp dinner dehydrating in the oven, Littlejohn turns to pinpointing the amount of fat in the mixture. With a transfer pipette, a chemist`s eyedropper, she bull`s-eyes 10 drops of the green mush into the bottom of an odd-looking flask, a two-bulbed affair shaped roughly like a dumbbell and bearing a valve in the middle. Ditto for a companion flask. To a third she adds 10 drops of a control mixture, in this case rabbit food, with a predetermined fat content.
To each flask, Littlejohn next adds 2 milliliters (mls) of ethanol and 10 mls of hydrochloric acid-the ethanol to help dissolve the fats, the acid to begin the process of freezing them from the rest of the mixture. Next she gives each flask a startup shake. Immediately the mixtures grow cloudy; a visible sign of digestion. Finally, she transfers the flasks from the lab table to a heat strip, a heating element stretched beneath a row of glass-tubed condensers. There, each flask hooked up to a condenser, the mixtures will be brought to a boil and the evaporated solvent returned to the flasks.
”We`ll come back in about 45 minutes,” says Littlejohn, adding, ”There`s nothing fast about analytical chemistry.”
Through the years a lot of calories have been burned-the food literally ignited-by chemists zeroing in on the energy awaiting in various foods. Human metabolism, which expends oxygen and gives off carbon dioxide, water and heat, consumes food in a manner that can be roughly compared to a fire reducing a woodpile. We digest our food less flamboyantly, of course. And less completely. We`re unable to extract the potential energy of such woody fibers as lignins, which is why fiber adds no calories to food and why nutritionists often distinguish between the gross energy value of food and its digestible energy. In search of the former, they call upon a capsule-shaped apparatus, externally about the size of a loaf of Italian bread, and made of heavy stainless steel. Inside, a device that resembles a spark plug ignites the food.
This nifty piece of equipment, known as a bomb calorimeter, calls to mind a terrific sucker bet. Consider: A bomb calorimeter determines the gross energy value of food via the rise in temperature of the water into which the
”bomb” is immersed. Consider, too: A so-called large or kilogram calorie is the amount of heat needed to raise the temperature of 1 kilogram of water 1 degree Centigrade. Which means: Scientists, in fact, actually measure food energy in kilocalories, not calories. So, the next time you`re a little strapped for cash, simply bet everyone in the room the Lean Cuisine in their home freezers contains about 300 thousand calories. Technically, you`ll not be wrong. The human body, of course, doesn`t digest zeroes, so most of us chew on-ingenuously, though to no bodily effect-off the mark in our calorie counting by no less than three orders of magnitude.
The individual most responsible for the federally approved methods of calorie counting was an Ohio Wesleyan University chemistry professor named Wilbur O. Atwater. Often called ”the father of American nutrition,” Atwater worked around the turn of the century on behalf of the USDA. All told, he conducted hundreds of experiments, some completed in minutes, the food under study burned in a bomb calorimeter; others lasting as long as five days, with human subjects confined to a four-foot-by-eight-foot sealed room dubbed a respiration calorimeter.
With this chamber helping to provide a closed, energy-balancing system, Atwater carefully prescribed and measured all food delivered through an airlock into the room. He was equally precise on the other end of the human equation. He noted increased room temperature to measure the subject`s conversion of food energy to heat, and by burning dried samples of bodily wastes in a bomb calorimeter, he also calculated the undigestible energy in the food. Atwater`s work and opinions raised some controversy in his time. Many scorned his recommendation that Americans cut down on fat in their diets. Teetotalers bristled that he sometimes served alcoholic beverages to students confined in his respiration calorimeter-and were no doubt even more enraged when he declared his studies showed that alcohol could be considered an energy-bearing food.
Overall, his work gave rise to a thick book of tables published by the USDA, a book commonly known these days as Agriculture Handbook No. 8. In it one finds caloric values for some 2,500 food items. (For instance: 100 grams chicken/dark meat without skin/roasted-184 calories.) Chefs consult Handbook 8 in preparing reduced-calorie restaurant meals. Food-company nutritionists thumb their copies, especially when a product has but few and consistent ingredients.
Moreover, Professor Atwater`s seminal work provided nutritionists with what has come to be called the Atwater System-in essence, a simple way to count calories for such mixed-bag products as Benihana`s Oriental Style Shrimp. The system, which is also known as the 4-4-9 Rule, assigns 4 calories to each gram of protein, 4 calories to each gram of carbohydrate and 9 calories to each gram of fat. Those numbers, Atwater found, represent good averages no matter what food is on the fork. If royalties followed the use of these averages, Atwater`s descendants would be well off; the 4-4-9 Rule is applied daily across the country in labs such as Woodson-Tenent.
On schedule, three-quarters of an hour later, Littlejohn returns to her trio of flasks. The mixture in each is now the color of cola. And still a long way from giving up its results. To each, Littlejohn adds 10 mls of denatured alcohol and sets them on the lab table to allow them to cool for an hour.
When she returns, she pours 20 mls of petroleum ether into each flask and shakes them, like handbells, one by one. ”The fatty acids don`t really want to be in solution with the ethanol,” explains Reimann. ”They prefer to be in a solvent like ether.” Already, like oil atop water, two layers are beginning to separate: at the bottom, the ethanol; on top, the ether containing the fats from the shrimp dinner.
While the mixture continues to settle out, Littlejohn outlines the continuing process. Using the halfway valve on each flask she will carefully pour off the ether layer, then filter it several times to remove any undigested food particles. Then she`ll return the mixtures, now in 250-ml beakers, to the heat strip-this time to boil off the solvent.
Meantime, Reimann smiles at my labored attempts to dust off high school chemistry lessons and patiently explains the procedures that will take place later in the week in the Des Moines facility-the analyses for protein, fiber and ash. More painstaking lab work.
