The Chemistry of . . . Fat Substitutes

The Next Generation of fake fats has arrived, but does anyone want them?

By Josie Glausiusz|Thursday, March 01, 2001
RELATED TAGS: NUTRITION, OBESITY


The ingredients of a bona fide italian mortadella from Bologna are enough to make a cardiologist cringe. Fat-rich pork scraps gleaned from the shoulders of "fairly old and heavy" pigs are finely minced and mixed with chunks of lard from the cheeks and neck of the animals. Toss in some spices and salt, cram into casings, cook, and squisito: a bulging sausage with a fat content of 30 to 35 percent. "You can imagine that a product like that, today, is seen more like a poison than like a food," says Roberto Chizzolini, a food scientist at the University of Parma. With that in mind, and with the aid of a grant from the European Union, Chizzolini has set out on a quest to create what others might see as an oxymoron: a low-fat mortadella.


A mortadella with fake fats could be a boon to 120 million overweight Americans.
Photo by Eric Weeks
Chizzolini knows his task isn't easy. Fat contains more energy per gram than any other edible substance— more than twice as much as carbohydrates or protein— which is why humans have evolved to crave it and conserve it. Not coincidentally, it has unique properties that make it difficult to mimic. Fat has what chemists call mouth-feel: a creamy texture and a tendency to melt onto the tongue. It gives off an unmistakable aroma when fried. And most important, its structure is such that it can carry certain flavor compounds as well as vitamins. Take out the fat, and what have you got? An awfully dull diet.

Given the well-known health risks of fat, it was inevitable that chemists would try to create substances that can make food taste fattier without being fattening. The perfect fat substitute could be cooked and fried, would taste like real fat, and be digestible. Yet therein lies a paradox: Any food that can be digested must carry calories into the body, but anything that can't be digested is liable to cause intestinal discomfort as the body tries to expel it— as popular experience with olestra, the most famous of all fake fats, seemed to show. Recent studies suggest that olestra's side effects aren't so bad, and it might even lead to better health. But researchers continue to search for an even better substitute.

Chizzolini has chosen to avoid the high-tech route. He makes his mortadella with carrageenan, a gel derived from red seaweed and used for years in toothpastes and puddings. Carrageenan is a short-chain sugar. When linked with water, it mimics the texture of fat. Just as pork fat is solid at room temperature and liquid when heated— which is why it melts in the mouth— so short-chain sugars join with water molecules to form a semisolid structure when cool. When heated in the mouth, the links between the sugars and the water weaken, and small sugar molecules spread smoothly out onto the tongue. With the aid of this gel, Chizzolini has been able to reduce the fat content of mortadella to just under 14 percent.

There's only one problem: Carrageenan may feel like fat, but it certainly doesn't taste like it. A volunteer panel at the University of Parma found the new meat "acceptable, but not the best quality," which could explain why it's not yet on sale. "It's nearly impossible to make the mortadella taste the same," explains Chizzolini, because fat has an affinity for aromatic compounds called esters and aldehydes that give flavor to food and, like fat itself, are hydrophobic: They hate water. Place a blob of fat on your tongue, and it will spread out like an oil slick on a wet road. Water-loving gels not only lack flavor but also can be swept away by saliva.

Faced with such obstacles, it's no wonder that Procter & Gamble modeled olestra, a yellowish goo with the consistency of shortening, on the real thing. A typical fat consists of two parts: a backbone of glycerol, a type of alcohol, linked to three long-tailed hydrocarbons called fatty acids, which vary in type depending on the fat. Enzymes in the intestines called lipases have evolved over eons to tear off two of the fatty acids, leaving truncated molecules small enough to be absorbed through the intestinal wall. In olestra, however, the glycerol has been replaced by a molecule of sucrose, a sugar, which has enough free arms to attach to eight fatty acids. Lipases cannot clamp onto such a large particle, so olestra passes, unscathed, through the intestines.

Olestra tastes like fat but contains, in effect, no usable calories, and two recent studies— both funded by Procter & Gamble— suggest that consuming it can be helpful to those with high cholesterol or heart problems. The first indicates that people who eat olestra can reduce their cholesterol levels by more than 10 percent; the second found a more than 10 percent increase in blood flow to the heart among people who had just eaten an olestra-filled banana muffin.

But olestra still has what can only be described as an image problem. Stamped on every can or bag of chips is an ominous— and unappetizing— warning mandated by the Food and Drug Administration:

"Olestra may cause abdominal cramping and loose stools." Since its approval five years ago olestra has also been the target of a campaign by the Center for Science in the Public Interest, which claims to have collected more than 2,500 complaints of abdominal upsets among people who have eaten olestra potato chips.


Graphic by Matt Zang

Procter & Gamble isn't giving up. They've petitioned the FDA to remove the warning, citing a study showing no difference in abdominal ailments between moviegoers given either a bag of potato chips made with olestra or a bag of chips cooked with regular fat. The biggest study of olestra-chip eaters, conducted on 3,200 subjects for six weeks by physician Robert Sandler of the University of North Carolina, found no increase in abdominal upsets or cramps in those who indulged. But olestra eaters did have more frequent bowel movements. Perhaps for that reason, and because olestra consumption decreases absorption of fat-soluble vitamins, the FDA has declined to announce when or if it will remove the label.

Meanwhile, food scientist Casimir Akoh of the University of Georgia is developing fats that contain fast-burning short- and medium-chain fatty acids, in addition to the long-chain fatty acids found in other fats. Derived from fish oils and other natural substances, they taste as good as regular fats, he says, contain 45 percent fewer calories, and are also digestible, sidestepping the problems faced by olestra. Akoh uses regular lipases, rather than elaborate chemicals, to chop up the fatty acid chains, and mice that consume his lipids have reduced their cholesterol levels by 49 percent. Akoh's low-fat fats could be sold as oils or semisolid shortenings and used in baking, frying, and in making chocolate, mayonnaise, and other foods. Yet he has been unable to find a company willing to market them.

Other researchers have emulated the olestra approach. They've replaced glycerol with glucose rather than sucrose, or with sorbitol, a sugar-alcohol used in some chewing gums. Chemists at Nabisco are creating fat substitutes that have long-chain alcohols instead of fatty acids. Perhaps the most promising substitute is being developed by a small company in Pennsylvania called Viritech. Known as EPG, it has the same glycerol and fatty acids as a normal fat, but chemists have strung ladderlike units of propylene glycol between the two components, making it too awkward for digestive enzymes to grasp.

Not one of these fake fats has FDA approval, and that's because the inventors haven't applied. In 1998, the first year olestra products were marketed nationally, sales topped $400 million. But by last year they had dropped to $200 million. According to Barry Swanson, a food scientist at Washington State University, fake fat developers recognize that it cost Procter & Gamble about a quarter of a billion dollars to develop olestra and petition the FDA to approve it. "Now everybody's just sitting back and waiting to see what happens."









The recipe for low-fat mortadella is online at www.unipr.it/arpa/facvet/annali/1999/zanardi1/zanardi.htm (Zanardi et al., "Low-Fat Mortadella: Experimental Formulations with Some Fat Substitutes").

More information about olestra can be found at Procter & Gamble's Web site: www.pg.com/main.jhtml. Or for an alternative view and news about potential side effects, see the Center for Science in the Public Interest's Web site at www.cspinet.org/olestra/index.html.

Casimir Akoh's Web site is at www.uga.edu/~fst/faculty/akoh.


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