edited by
GEORGE8.
KAUFFMAN
California State University. Fresna Fresna, CA 93740
The Development of Olestra, a for Dietary Fat R. J. Jandacek Procter and Gamble Miami Valley Laboratories, Cincinnati, OH 45239
Dietary Fat-Culture and Calorles Fat in the diet has made the hit lists of the National Cholesterol Education Program, the American Surgeon General, and the American Heart Association (1-3). Each of these groups has recommended that the American public eat less fat. The food industry is beginning t o respond to concerns about dietary fat with the development of reduced-fat foods and substitutes for dietary fat that maintain taste and eating qualities of the foods they replace. A recent approach is the use of engineered fats that offer the potential to provide all of the advantages of conventional fats in food preparation without contributing calories or saturated fat. This paper reviews the properties and development of olestra, an example of these engineered fats. What is this substance calledfat thatweare being asked to remove fromour diets? Why do we like it somuch? How does it differ from carbohydrates? Does i t have any benefits? How does the body use fat? Is it possible for chemistry to provide the joys of fat-the cream in ice cream, the smooth melting of chocolate in the mouth, the crispness of a potato chip-without the concerns raised by today's nutritional guidelines? In this article I will try to answer some of these questions. Nearly all of the fat that we eat is in the form of triglycerides (Fig. I), the common term for glycerol esterified with three fatty acids, or triacylglycerol compounds. Unsaturated fatty acids with cis double bonds, such as oleic and linoleic acids, do not easily align to pack in a crystalline array and therefore melt at low temperatures. The long-chain saturated fatty acids more readily pack together and form higher melting crystals. The properties of a fat molecule are dependent on its constituent fatty acids. For example, oleic acidbased olive oil is a liquid while stearic acid-based tallow is a solid a t room temperature. The desirability of fatty foods is not a recent dietary development. Fat once ranked with silk, gold, and perfume among one's wish list. The promise in the Bible, "And ye shall eat the fat of the l a n d (Genesis 45:18), underscores fat's desirability in previous millennia when the fatted calf was a banquet's piPce de resistance. A brief look a t the human form as depicted by Rubens three centuries ago is further evidence that the transfer of fat from food to body insulation was desirable and considered a mark of beauty. So today we find ourselves carrying centuries of fat-loving culture and recipes into our diets and are faced with ever476
Journal of Chemical Education
FI
F-O-S-(CHl)&H, CHIOH I ~-O-~-(CH~,-CHI CH-OH CH2- 0-C-(CH2).CH1
I
P
HO~C-(CH&CH,
CHIOH
Figure 1. The structural formula of a triglyceride and its constituents, fatty acids and glycerol.
increasing amounts of evidence that too much fat in the diet, especially saturated fat from animal sources, increases the risks of developing atherosclerosis, heart disease, and other health problems. Additionally, the rounded figures of Ruhens have now been replaced by the trim figures of athletes as the paragons of the body beautiful and presumably healthful. In the United States fat tvoicallv accounts for a o ~ r o x i mately 37q of the energy (csioiiesj in the diet ( 4 ) compared with less than 10%in societies where rice is a maior comDo. nent of the diet (5).Although some fat in the diet is necessary for healthand development as a source of essential fatty acids, we consume more fat than that required for optimum health. Dietary guidelines promulgated by public health organizations call for a reduction of total calories from dietary fat to 30% and areduction of calories from saturated fat to 710%of total dietary calories (1-3). The attainment of a high level of dietary fat by affluent societies reflects an enjoyment of foods with high levels of fat. The change in the economic status of Japan has been accom~aniedbv a doubling of oer caoita fat intake from 1960 to 1985 (6j. The reasons behind o& taste for chocolate andFrench fries DerhaDs originated inlean times when energy-dense foods were a benefit to health and survival. Triglycerides make up nearly all of the body's mass of fatty tissue and its stored energy. When the body is in need. of energy not provided by its small carbohydrate stores, triglycerides are hydrolytically broken down by lipase enzymes to produce fatty acids. These fatty acids are enzymatically oxidized to release usable energy, carbon dioxide, and water. Because of the large number of oxidizable carbon atoms, triglycerides are excellent sources of energy. By contrast, the oxygen-bonded carbon atoms of carbohydrate
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