Carbohydrate-based fat replacers

to heat, pH, shear and salt (Nielsen 1996). There is more than one form available commercially: Slendid®100 and 110 are LM pectins, while Slendid®200 is HM pectin. Slendid® line of products can replace up to 100 per cent of the fat in a wide range of food products including mayonnaise, salad dressings, processed meats, ice cream, processed cheeses, soups and sauces, desserts, and bakery products (Artz and Hansen 1994). The use of Slendid® can reduce the fat content in mayonnaise from 80 per cent to 3 per cent, and in a frankfurter from 25±35 to 3±5 per cent (Nielsen 1996).

Oatrim is a fat replacer developed and patented by the US Department of Agriculture (USDA) in 1991. Oatrim is produced from the partial hydrolysis of oat flour or bran by a-amylase with the 0-glucan contents of 1±10 per cent (Cho and Prosky 1999). Oatrim is a soluble, tasteless powder that can be incorporated into food as a dry powder (4 kcal/g) or as a gel (1 kcal/g). Oatrim is heat stable for baking and can withstand pasteurization processing conditions, but is not suitable for frying (Calorie Control Council, 1996; Van der Slvijs et al. 1999). Oatrim or its gel gives the sensory property of natural taste and fatty texture to foods. Oatrim applications include pasteurized cheeses, dairy products, confectionery, frozen desserts, cereals, baked goods, and meat products (Inglett 2001). ,3-Glucan components in the oatrim have been reported to have a serum cholesterol-lowering effect (Inglett 1997, 2001). Oatrim is licensed for commercialization to ConAgra (Omaha, NE), Quaker (Chicago, IL) and Rhone-Poulenc (Cranbury, NJ).

Z-trim was also developed by the USDA. It is made from the high-cellulose portion of the hulls of oats, corn, rice, soybean, and peas, or bran from corn or wheat (Bollinger 1995; Akoh 1998), and is a tasteless, insoluble and indigestible fiber with zero calories. Z-trim gel contributes fiber, moistness, large water-holding capacity, high viscosity, and smooth texture. These properties make it possible for the reduced fat foods to taste like the traditional foods that are rich in fat. Z-trim has food applications in reduced-calorie cheeses, hamburgers and baked goods, but it is not suitable for deep fat frying (Cho and Prosky 1999).

Polydextrose was invented at Pfizer Inc. in the mid-1970s (Rennhard 1975). Polydextrose has been used primarily as a low-calorie bulking agent, but it is also used as a fat replacer. Polydextrose is made up from randomly cross-linked D-glucose polymers containing a small amount of sorbitol and citric acid (LaBarge 1988). Polydextrose has reducing carbonyl groups that participate in the Maillard browning reaction. It is only partially hydrolyzed by digestive enzymes (Dziezak 1986; Mitchell 1996) and contributes 1 kcal/g, which is quite attractive to health-conscious individuals. However, a laxative effect may be observed from excessive consumption of 90 g/day because a large proportion of polydextrose is excreted intact (Artz and Hansen 1994). Products with more than 15 g of polydextrose per serving must be labeled. Polydextrose is available as a powder with a pH of 2.5±3.5 and a 70 per cent solution with a pH of 5.0±6.0 (Dziezak 1986). Polydextrose is odorless, nonsweet, and highly soluble in water. It exhibits high viscosity when dissolved in water, resulting in creaminess and mouthfeel similar to fat (Dziezak 1986). Polydextrose is commonly used in several food categories, including frozen dairy desserts, baked goods, chewing gums, frostings, salad dressings, puddings, hard and soft candies, spreads, sweet sauces, and syrups (Artz and Hansen 1994). Litesse® is a polydextrose-type product manufactured from Pfizer, Inc. (Mahungu et al. 2002) and may be used as a fat replacer, bulking agent and humectant.

Gums, also often referred to as hydrocolloids, are high molecular weight carbohydrates that have traditionally been used as thickeners, stabilizers, and viscosity enhancers at very low concentrations of 0.1±0.5 per cent to form gels. The type of gum used for a particular food application depends on pH, temperature, and concentration, which can affect viscosity and gel-forming characteristics (Lucca and Tepper 1994). Gums are not used directly as fat replacers, but they are used in formulating low-fat products because they mimic the sensory property of fat such as a slippery and creamy mouthfeel. Agar, alginate, gum arabic, carrageenan, guar gum, locust bean gum, and xanthan gum are frequently used in salad dressings, icings and glazes, desserts, ice cream, dairy products, ground beef, baked goods, soups, and sauces.

Galactomannan gum is most widely used in food products and guar gum and locust bean gum belong to this type. Guar gum is obtained from the seeds of an annual leguminous plant (Cyamopsis tetragonolobus). The locust bean gum, also known as carob galactomann, is the common name for the seeds of the carob tree (Ceratonica siliqua) and has been used as a food source for thousands of years, whereas guar gum was developed and launched recently to the market owing to a lack of locust bean gum (Clegg 1996). Both gums are neutral polysaccharides composed of a linear chain of a-1,4 linked Q-D-mannose to which single a-D­galactose units are attached via a-1,6 linkages (Clegg 1996; Lazaridou et al. 2000). Guar gum and locust bean gum are different in their ratio of mannose to galactose (M:G ratio) and the position of the galactose side chains on the main chain backbone.

Guar gum has a highly substituted structure with an M:G ratio of about 1.8±2.0, whereas locust bean gum has an M:G ratio about 3.5±4.0 (Schorsch et al. 1997). Guar gum is soluble in cold water and produces highly viscous, pseudoplastic solutions (Clegg 1996; Herald 1986). In contrast, locust bean gum is not easily soluble in cold water and needs heating (80ëC) for complete hydration to give a highly viscous solution. Locust bean gum gel is not affected by pH change or ionic strength. Galactomannan is not directly used as a fat replacer and the main function of galactomannan gums in low-fat foods is that they control viscosity by holding water (Setser and Racette 1992). This becomes important as the fat level in foods is reduced. Guar gum and locust bean gum have many food applications, including ice cream, frozen desserts, low-fat cheese products, bakery goods, sauces, and dres­sings. Locust bean gum is preferred in frozen desserts because it retards ice crystal growth. Guar and locust bean gum have a synergistic effect with xanthan gums.

Xanthan gum was discovered about 50 years ago and is produced by fermentation of bacterium Xanthomonas campestris. The main polymer chain consists of 3-1,4 linked D-glucose units identical to that of cellulose but substituted on every second residue with a charged trisaccharide group. This side group consists of two mannose units separated by a glucuronic acid residue (Clegg 1996; Schorsch et al. 1997). Xanthan gum is readily soluble in cold or hot water and exhibits a highly viscous, pseudoplastic rheology. Like galactomannan gums, xanthan gum does not serve as a direct fat replacer, but can be used as a stabilizer in low-fat foods by controlling viscosity and texture. Xanthan gum is stable over a wide range of pH and temperature, whereas other gums lose their viscosity under the same conditions. Such properties persist even at very low concentrations (0.1 per cent) and functions as a very effective stabilizer in low-fat foods such as dressings, sauces and mayonnaises to exploit its weak-gel (Clegg 1996). Kelco (Clark, NJ) has a line of products made from xanthan gum such as Keltrol, Keltrol BT, Keltrol GM, and Keltrol SF.

The role of fat replacers in reducing cardiovascular disease

There is a general consensus that a high-fat diet is linked with the development of obesity, high serum cholesterol level, and cardiovascular disease. In addition, there is evidence that high fat intake may increase the incidence of breast, colon, and prostate cancers (National Cancer Institute 1984). The relationship between dietary fat and the development of cardiovascular disease has been well documented. Latta (1990) reported that reduction of fat consumption lowered the risk of heart disease by 10 per cent, and the risk of cardiovascular disease by 20 per cent in people who were overweight by losing their weight and altering their diet. Hooper et al. (2001) reported that the reduction of dietary fat resulted in the decrease in cardiovascular events by 24 per cent in participants after a period of 2 years. Recent research indicates that the amount and the type of fat in diet are also associated with the prevention of cardiovascular and coronary heart disease.

Diets rich in polyunsaturated or monounsaturated fatty acids tend to reduce the risk of cardiovascular and coronary heart disease. Conversely, diets rich in saturated fatty acids increase the risk of cardiovascular and coronary heart disease (Dyerberg et al. 1978; Grundy 1994). Therefore, restriction of fatty foods in diet is an effective way of reducing the risk of chronic diseases such as cardiovascular and coronary heart disease. Reducing fat and calories in the everyday diet has become a number one concern for most health-conscious individuals in the US.

Many health-related authorities including the US Dept. of Health and Human Services, US Surgeon General, American Heart Association, American Diabetes Association, American Dietetic Association, American Cancer Society and National Institutes of Health have recommended dietary energy from fat should be reduced to 30 per cent with saturated fat intake to less than 10 per cent. Fat intake has been generally decreased since the 1970s. A national food consumption survey showed that total fat intake has decreased from 36 per cent in 1978 to 34 per cent in 1990 (Carroll et al. 1983; Lenfant and Ernst 1994), but the proportion of energy obtained from fat is still higher than the recommended level (Frazao 1996). The main sources of dietary fat in the US are meat, poultry, fish, baked goods, fats and oils, and dairy products, which accounts for about 90 per cent of total fat intake (Mattes 1998). The decrease in energy and fat consumption may be due to the awareness of health issues and increased availability of low- and reduced-fat products. A national survey in 2000 (Calorie Control Council 2001) showed that 163 million adult Americans (79 per cent of the adult US population) consume low-fat or reduced-fat foods and beverages. The rapid increase in reduced and low-calorie food products has resulted in confusion about labeling standards. Therefore, food labels bearing information on a reduction in fat or calories are important to consumers and food manufacturers. The US nutrition labeling regulations provide claims for the use of reduced fat- and calorie-related terms as shown in Table above (US Food and Drug Administration 1999). Food manufacturers have developed a number of fat replacers and more than 5000 reduced-fat, nonfat or low-calorie food products have been introduced to the market (Wylie-Rosett 2002). Fat replacers have opened the door for a new age of reduced-fat or fat-free options in variety of foods.

There are some studies in the literature that show that fat replacers provide health benefits to the public, such as weight loss, reduction in cholesterol, and lower incidence of cardiovascular disease. Most of the health benefit studies of fat replacers have been concentrated on one fat replacer, olestra. Patterson et al. (2000) reported that subjects consuming olestra had significantly reduced total serum cholesterol levels compared with subjects without consuming olestra. Other studies have shown that olestra has potential to lower total and low-density lipoprotein (LDL) cholesterol levels in both normal and hyper­cholesterolemic individuals (Fallat et al. 1976; Glueck et al. 1979, 1983; Jandacek et al. 1990). Olestra also may be a promising tool for weight reduction.

Roy et al. (2002) reported that a significant weight loss was observed in men and women who replaced one third of dietary fat with olestra during the study period. One study involving obese patients with and without diabetes mellitus was conducted by Grundy et al. (1986). He reported that there was a decrease in total and LDL-cholesterol level in people without diabetes and a marked decrease in plasma triglycerides but no uniform change in LDL-cholesterol in people with diabetes when a low-calorie diet with or without olestra was supplied. Considering the report that the annual incidence of cardiovascular disease is increased more than two times in people with diabetes (American Diabetes Association 1996), consumption of foods containing olestra would be advantageous in reducing total and LDL-cholesterol.

Nutrient content claims, indicating reduced fat and calorie food*.Less than 0.5 g of fat/serving25% or less fat than a reference product/serving40 or fewer calories than regular product /serving25% or fewer calories than regular product/serv ing1/3 fewer calories or 50% of the fat in a reference foodA large number of fat replacers have been developed and are being used in partial or complete replacements for fat in foods. Each fat replacer has unique characteristics and uses. Some of fat replacers have been already approved by the Food and Drug Administration (FDA), while others are under review, and still others are in the developmental stage. Fat replacers represent a diverse chemical structure, functional and sensory properties and food applications.

The term fat replacer is a general term to encompass any ingredients used to replace fat. Generally, fat replacers are categorized into two groups ± fat mimetics and fat substitutes. Fat mimetics are substances that imitate organoleptic or physical properties of triacylglycerol (triglycerides, conventional fats, and oils) but that cannot replace fat on a 1:1 weight basis (Shand 1997; McClements and Demetriades 1998; Akoh 2002). Fat mimetics have different chemical structures from triacylglycerols and protein- or carbohydrate-based fat replacers belong to this category. The caloric value of fat mimetics ranges from 1 to 4 kcal/g. Fat mimetics entrap a substantial amount of water and denature or caramelize at high temperatures, so they are not suitable for frying. Fat mimetics carry water-soluble flavors but not lipid-soluble flavor compounds and are generally less flavorful than fat (Akoh 2002). Fat substitutes are ingredients that resemble triacyglycerols chemically and physically. They can replace fat on a 1:1 weight basis and contribute either fewer calories than fat or no calories. Lipid-based fat replacers belong to this category. They are stable to cooking and frying temperatures. The terms fat replacer and fat substitute have been differentiated (Miraglio 1995; Shand 1997; Akoh 2002), but they are used interchangeably to cause confusion and misunderstanding. An ideal fat replacer should be safe with a significant caloric and fat reduction while maintaining the functional and organoleptic properties of a conventional fat (Warshaw and Franz 1996). Since no single ingredient is an ideal fat replacer, several fat replacers are often used in combination as part of a functional blend in one food system. Therefore, the search for an ideal fat replacer continues.

Fat replacers represent a variety of chemical types with diverse physicochemical and sensory properties, so it is not easy to provide a simple classification. Fat replacers may be classified as carbohydrate-based, protein-based, or lipid-based replacers, depending on chemical composition of the ingredients (Hassel 1993; Warshaw and Franz 1996).

Lipid-based fat replacers

Lipid-based fat replacers are a stable group and include the synthetic compounds. They have chemical structures similar to triacylglycerols, but have reduced or zero caloric content because they are not fully hydrolyzed by digestive enzymes. Examples for lipid-based replacers are sucrose polyester (olestra), sucrose fatty acid esters, structured lipids, caprenin, salatrim, medium chain triacylglycerols, dialkyl dihexadecylmalonate (DDM), esterified propoxylated glycerol (EPG), and trialkoxytricarballylate (TATCA).

Sucrose polyesters or SPE, commonly known as olestra (Olean, Procter & Gamble Co., Cincinnati, OIT), is the common name for the mixture of sucrose esters with the addition of six, seven or eight fatty acids. The common fatty acids are C16:0, C18:0, C18:1, C18:2, and C18:3 fatty acids (Rizzi and Taylor 1978; Akoh 2002). Sucrose polyesters are prepared from the reaction of fatty acids with the hydroxyl groups of sucrose in the presence of catalysts (Gardner and Sanders 1990). The types of fatty acids determine the physicochemical properties of olestra (Akoh 2002) and can be formulated for a variety of foods such as fried foods, cooking oils, shortenings, baked goods and spreads (Giese 1996b; Dziezak 1989). Olestra prepared from saturated fatty acids is solid, whereas olestra prepared from unsaturated fatty acids is liquid at room temperature (Peters et al. 1997). Olestra is non-caloric because the molecule is too large to be absorbed or metabolized by pancreatic lipase (Mattson and Nolen 1972; Grossman et al. 1994). It has the organoleptic and thermal properties of fat. For this reason, it can be used in high-heat applications such as baking and frying. Olestra was approved by the FDA in 1996 as a food additive. It can be used as a replacement for up to 100 per cent of the fats and oils used in the preparation of savory snacks such as potato, tortilla and corn chips, crisps and crackers (Prince and Welschenbach 1998; Warshaw and Franz 1996).

Olestra passes through the gastrointestinal tract without being absorbed and it may be associated with cramping, loose stools and reduced absorption of fat-soluble vitamins and nutrients. Therefore, use of olestra in foods requires the addition of specific amounts of vitamins A, D, E, and K to these foods. Research has shown that olestra does not significantly interfere with the absorption of macronutrients such as carbohydrates, proteins, or water-soluble vitamins and minerals (Bergholz 1992). Olestra is a lipophilic compound and its impact on the absorption and efficacy of lipophilic drugs such as oral contraceptives, diazepam and propranolol was investigated. Results indicate that there was little possibility of interfering with the absorption or bioavailability of lipophilic drugs (Miller et al. 1990, Prince and Welschenbach 1998). Toxicologic feeding studies in animals concluded that olestra is not toxic, carcinogenic, mutagenic, or teratogenic (Wood et al. 1991; Bergholtz 1992). Gastrointestinal testing showed that olestra has no significant effect on bowel movement, total transit time, or pancreatic response. Olestra is not metabolized by gut microflora in anaerobic conditions, nor does it affect the fermentation of other substrates by microflora in the colon (Huck et al. 1994).

Many clinical studies have shown that olestra has potential to benefit some individuals. For example, replacement of conventional fat with olestra can benefit people at high risk of cardiovascular disease, coronary heart disease, obesity, and colon cancer by helping them to lower total fat intake and blood cholesterol level, and to lose weight (Crouse and Grundy 1979; Glueck et al. 1979, 1983; Grundy et al. 1986; Jandacek et al. 1990; Patterson et al. 2000; Bray et al. 2002; Roy et al. 2002).

Protein-based fat replacers

The protein-based fat replacers include microparticulated protein derived from milk, egg, whey or vegetable proteins. The limitation of protein-based fat replacers is that they cannot be used in high-temperature frying because the protein will denature and lose its creaminess. However, some forms may be used in traditional baking and cooking applications. Common uses are in dairy products such as ice cream, butter and sour cream as well as in oil-based products such as salad dressings and margarines.

Simplesse® (NutraSweet, Deerfield, IL) was the first fat replacer developed with protein. Simplesse received GRAS approval by the FDA in 1990 for use in frozen desserts (Singer and Moser 1993). It is an all-natural versatile product made from milk and/or egg white protein, sugar, pectin, and citric acid (Gershoff 1995). Simplesse is produced by a patented process known as `micro­particulation’. Microparticulated protein is created by homogenizing and pasteurizing simultaneously at high temperatures to develop microscopic particles of uniform size of approximately 1 pm in diameter (Singer et al. 1988, Singer and Moser 1993). The resultant small spherical particles float over the tongue, giving creamy and smooth texture similar to fat (Gershoff 1995; Warshaw and Franz 1996). Protein particles smaller or larger than 0.5±3 pm in diameter do not provide the fat-like mouthfeel. The nutritive quality of the protein is unchanged during the microparticulation process and the caloric value is 4 kcal/g on a dry basis. However, microparticulate proteins that make up Simplesse are hydrated during manufacturing process and the final caloric value is actually 1±2 kcal/g (Anon 1990; Singer and Moser 1993). Therefore, the use of Simplesse provides a caloric reduction in many food products.

Simplesse is widely used to enhance the quality of low-fat foods. It provides fat-like creaminess in high-moisture foods such as dairy products, baked goods, sour cream, salad dressings, mayonnaise, margarine, sauces, and soups, but is not suitable for use in frying. Simplesse retains the biological property of the protein used, so the individuals who are allergic to egg or milk proteins can experience allergic reactions to it (Singer and Moser 1993; Gershoff 1995). There is more than one form of Simplesse available. Original Simplesse was sold as wet ingredient with solids content about 20±40 per cent. Simplesse D 100, a dry form, is derived from whey protein concentrate without egg protein and is readily hydratable to produce a thixotrophic fluid that can be used in a wide variety of dairy and bakery products.

Safety and regulatory issues of fat replacers

Manufacturers of fat replacers must be aware of existing legislative require­ments to obtain approval for the use of fat replacers as well as the labeling of foods. Safety of fat replacers are regulated under two FDA approval categories, GRAS and food additives. GRAS substances are defined as ingredients that are produced from common food components and generally recognized by experts qualified by scientific training or by scientific procedures to be safe under conditions of its intended use (Middlekauff 1974; Warshaw and Franz 1996). GRAS category was established in 1958 and many new substances including fat replacers have been approved (Middlekauff 1974, 1989; Vanderveen 1994).

There are two approaches to submit GRAS affirmation petition to the FDA. The first is a manufacturer’s self-determination of the substance claiming as GRAS. The other is petitioning FDA to grant the ingredient as GRAS. The majority of fat replacers have received GRAS status by FDA (Warshaw and Franz 1996; Clydesdale 1997). The determination of the ingredients as GRAS is based on long history of safe use or scientific data that support the safety of the ingredients for specific applications (Warshaw and Franz 1996; Mattes 1998). Examples of fat replacers approved as GRAS are starches, gums, and microparticulated proteins.

Obtaining a new ingredient approval as a food additive is more complex than a GRAS affirmation petition. A food additive is defined as a substance the intended use of which results or may reasonably be expected to result, directly or indirectly, in its becoming a component or otherwise affecting the characteristics of any food (Middlekauff 1974). Food additives, unlike a GRAS substance, cannot be added in the foods or marketed before the FDA approves their use. Therefore, a food additive petition requires submission of extensive research data on the new ingredient’s safety and intended use. Only olestra has received food additive approval for a lipid-based fat replacer.

Fat replacers could substitute a significant proportion of fat in the diet and be consumed in gram quantities each day by some individuals, so their safety must be examined more carefully. Traditional safety evaluation methods are not adequate to evaluate the fat replacers because most other food additives are consumed in only 1±2 per cent of food products, whereas fat replacers are consumed in large amounts. Because of this, a specially designed safety evaluation program must be developed with the consideration of exact chemical structure, stability during production, and identification of degradative byproducts of fat replacers. Consideration also should be made in the toxicological, physiological, and nutritional testing (Artz and Hansen 1994; Borzelleca 1996). Safety testing of fat replacers should be conducted on animals and the results from animal testing could be confirmed in human studies. If the fat replacers are not absorbed, effects on gastrointestinal tract, colonic microflora ecology, toxicity of degraded metabolites, and laxative effects should be considered (Gershoff 1995; Mahungu et al. 2002). If the fat replacers are absorbed, their absorption and elimination pathway must be assessed.

Since dietary fats are a source of essential fatty acids and a carrier for fat-soluble vitamins, reduced consumption of traditional fats by consuming fat replacers could lead to a depletion of these nutrients. So the studies to investigate the long-term effects of fat replacers on the absorption or utilization of essential fatty acids and fat-soluble and water-soluble nutrients should be conducted. It has been shown that olestra-containing products lowered the serum concentration of carotenoids and fat-soluble vitamins (Westrate and van het Hof 1995; Schlagheck et al. 1997; Broekmans et al. 2003). With the exception of olestra, few studies have been undertaken that relate consuming fat replacers to the nutritional status of dietary components. In addition, the effects of the interaction of the fat replacer or its metablite with orally dosed drugs also should be considered (Vanderveen 1993, 1994; Mahungu et al. 2002). The effect of fat replacers on selected population groups with health problems such as obesity, cardiovascular disease, and diabetes as well as with healthy people should be considered.

The majority of fat replacers approved by the FDA are GRAS substances because they are created from common food components of carbohydrate or protein, so the minimal requirement for safety testing was required. However, olestra has received food additive approval and more extensive research data including toxicological, clinical, nutritional, and gastrointestinal testing was required for the food additive petition.

Considering both the scientific literature and the FDA review process, the fat replacers that are currently available in the market are safe. As new fat replacers are developed, their safety and availability will be regulated by the GRAS or food additive petition process.