Hundreds of miles away, other technicians will determine the protein content of the sample after digesting it with sulfuric acid, converting nitrogen in the sample to ammonia, next turning the solution alkaline, then distilling, titrating and finally measuring the amount of ammonia (NH3). That will reveal the amount of nitrogen, which, in turn, by multiplying by 6.25 will provide a percentage of protein: the assumption being that most protein is about 16 percent nitrogen.
The determination of fiber content-a digesting of a small sample of the shrimp mixture with acids and neutralizing bases-will take twice as long, Reimann explains, virtually all day. This for what in many cases totals less than 1 percent of sample weight.
The remaining procedure calls for chemists to place a treated sample of known weight into a special oven called a muffel furnace, the dial set for 550 degrees Centigrade (1,022 degrees Fahrenheit). The procedure tests for the logical output of such an inferno: ash. Reimann identifies this tiny amount of uncombusted remains as a residue of inorganic salts such as sodium chloride and potassium chloride. The human body also derives no energy from these salts, Reimann explains, adding, ”If you`re on a diet (and not hypertensive), you can put all the salt you want on your food; it`s not going to change the calories.”
Calories. Indeed, that`s what I`d come in search of. So far, there`d been test upon test. More steps than an Arthur Murray dance class. Samples had been cooled in a desiccator, to keep measurements from drifting so much as 1 percent out of line. Then weighed on a metric balance, accurate so far to the right of the decimal point that Littlejohn has to use gloves in handling samples because the oil of a single fingerprint would affect the reading. In a word, precision.
And I realize that somehow troubled me. For when the percentage of fat and protein would finally be measured, and the percentage of carbohydrate in the sample determined after subtracting from 100 these two percentages and the percentages for moisture and ash, the lab`s four-decimal-point precision would suddenly give way to whole-number approximations. The 4-4-9 Rule would take over. These hard-sought percentages, penultimately converted to grams
(figuring a package weight of 10 ounces, or 282 grams) would be multiplied by Atwater`s system of assigning 4 calories to each gram of protein, 4 calories to each gram of carbohydrate and 9 calories to each gram of fat. It would be akin to a bank teller taking in money all day, carefully counting deposits of $13, $89, $137 and so on and then, upon closing the window, totaling the deposits by measuring the stacks of ones, fives and tens with a yardstick.
”It does seem kind of goofy,” Reimann agrees, hastily adding that in conducting a nutritional analysis of many animal feeds, Woodson-Tenent often spends an extra day, and considerably more lab work, to arrive at a truer estimate of protein than one that concludes by multiplying by 6.25.
”You mean you`re more precise with animal food than human food?” I ask. ”Sure,” he says, and then quickly unknots the paradox. ”Many times animals get only one source of feed, so it had better be nutritionally complete.”
But what about the last-stage surrender of laboratory precision? Doesn`t that trouble him? Not really, he says, except for one unironed wrinkle: ”One big stinker is the fiber-whether you subtract it or not when figuring the calorie content of the carbohydrates.” Though not subtracted in figuring the carbohydrate content of a food sample because fiber contains a good deal of carbohydrates-undigestible ones-it would make sense to remove this amount before multiplying by 4. Fiber, remember, contains no calories. The USDA allows, but does not require, the subtraction of fiber content in the carbohydrate portion of the calorie count. So some labs don`t bother to analyze for fiber. Result: inflated carbohydrate figures and calorie counts that may drift unnecessarily high. Reimann points to the Benihana package.
”With some of these frozen entrees,” he says ”you`re talking about a difference of as much as 10 calories.”
But, do 10 or even 20 calories really matter? Reimann asks. ”Are you going to run an extra mile? There`s a guy here at work who can eat tremendous amounts of food, and he doesn`t gain an ounce, whereas others here are on constant diets and are still chubby. People digest food differently and metabolize food differently. So let`s not make a big thing out of something that`s not needed to be that precise. I admit, though, that I look at the calorie listings when I go shopping. They`re a good indicator.”
The USDA appears to be of like mind. It justifies use of the 4-4-9 Rule, and such other blurring factors as its count-it-or-not policy for fiber, by pointing to a host of uncertainties. Says Wells Willis, a spokesman in the nutrition branch: ”No two crops of beans are exactly the same. No two carcasses of animal. Package weights may not be precise, either. Due to faulty plant equipment, there may be some degree of overfill or underfill.” There is also the matter of rounding. Products containing more than 50 calories must be rounded to the nearest 10, according to USDA regulations. Furthermore, allowing for batch differences and other manufacturing uncertainties, companies are given a 20 percent leeway, high or low, on total calories-meaning a product claiming under 300 calories could actually have 360 without incurring governmental wrath.
Knowing all this, I`m enlightened and bemused at what I see on the bottom of one of the beakers that lipid chemist Linda Littlejohn removes from the heat strip late in the day of my visit to Woodson-Tenent. All that remains, after the evaporation of the ether, is a thin film, spread not much bigger than a quarter and about as distinguishable as an unconsumed half-swallow of coffee discovered hardened to the bottom of a forgotten cup. This is the fat. Littlejohn later records its weight as 1.21 grams.
That smudge on the bottom of the beaker is my parting shot of calorie counting. A few days later, after he receives the results via computer from Des Moines and converts laboratory measurements to corresponding package weights, Reimann mails me a certificate of analysis. I read: moisture-220.5 gm; protein-9.995 gm; fat-3.61 gm; fiber-.864 gm; ash-2.905 gm; carbohydrates- 45.01 gm (this before subtracting the fiber).
The package pegged the calories at 230. Now aware of such things as batch differences and rounding allowances, I don`t expect a perfect match from the laboratory. I reach for my pocket calculator and personally invoke the 4-4-9 Rule. The calculations mirror the bottom line on the Woodson-Tenent certificate of analysis: 248.9 calories. Only now do I realize I still haven`t tasted the shrimp-and-rice dish.
