In the trend toward low-carb and no-trans-fats foods, whatever happened to no-fat or low-fat products? As food manufacturers are discovering, demand is still there. Kathryn Cooper and Dr. John Michaelides explore the market for the latest innovations in food texturants
Fat is a major multitasker. It provides nutrition; determines the physical structure of food during processing, packaging and storage; and shapes the sensory characteristics of the food, including appearance, texture, flavour and mouthfeel.
Nutritionally, fat provides essential fatty acids (eg, linolenic and linoleic) and fat-soluble vitamins. This can be a problem for some fat substitutes. For instance, Procter and Gamble?s olestra, marketed under the trade name Olean, has been criticised for reducing absorption of fat-soluble nutrients such as carotenoids and vitamins A, D, E and K. Manufacturers need to add these vitamins back into olestra-containing foods to ensure their nutritional content.
The nature and amount of fat also determines shear-sensitivity, tackiness, fat migration and dispersion after processing and during packaging. Physically, fats can de-emulsify, migrate or separate during storage. Chemically, they can oxidise and become rancid.
Over the years, many new and redesigned fat replacers and extenders have been introduced to help processors produce good tasting, nutritious and visually acceptable food products. (See table, below.)
The greatest challenge of formulating low-fat/no-fat products is to deliver the sensory characteristics consumers demand. Usually, multiple ingredients are needed to mimic the physical and sensory properties of a full-fat product, and each different product requires its own unique set of solutions. There are three basic types of fat replacers: carbohydrate-based, protein-based and fat-based.
Carb-based fat replacers
Carbohydrate-based fillers, such as processed starches and fibres, mimic fat by binding water, and providing lubricity, body and a pleasing mouthfeel. They add bulk, viscosity, structure, ?slip? and texture to products. Their energy values are lower than fat and only small amounts are required to bind water and fill the void left by the fat removed.
Starches: Resistant starches, waxy, highly cross-linked and modified starches work well in high-moisture systems such as salad dressings, low-fat spreads, meat emulsions and bakery products, such as layer cakes. They are not recommended for use in low-moisture systems such as cookies and crackers, nor can they replace frying oils. However, fat absorption can be reduced by coating the product with speciality starches.
Fibres: Refined fibres such as microcrystalline cellulose or carboxy-methylcellulose can reduce fat in a crude way. Their effectiveness is based on their ability to hold water and provide a somewhat smooth mouthfeel, and they are frequently used in baked goods, dressings and sauces.
Other modified fibres include Oatrim, Nu-TrimX and Z-Trim.
Oatrim is a new fibre-based product used in no-fat or low-fat formulas. It was developed and patented by the US Department of Agriculture and contains a mixture of beta-glucans and amylopectins. Oatrim also contains minute quantities of lipids, proteins and minerals. Beta-glucan (soluble dietary fibre) also helps lower blood cholesterol, blood glucose and insulin response, making attractive health claims possible. Oatrim succeeds because of its ability to form, through heating and cooling, a shorteninglike gel, which has about nine times less energy value than fat.
Nu-TrimX is a new generation of hydrocolloids containing solubilised beta-glucan from oat and barley endosperm with greatly reduced insoluble cellulose. This provides greater ability to produce functional foods with more beta-glucan and less fat.
Z-Trim is a zero-calorie fat replacer produced from low-cost agricultural by-products, such as hulls of oats, rice, corn, soybean and peas, or bran from corn and wheat, by completely disintegrating their cellular structure to form greatly reduced particle size powders that form gels with a smooth texture and increased water-holding capacity.
Oatrim, Nu-TrimX and Z-Trim can be used in processed meats, pasteurised cheeses, baked products, frozen desserts, salad dressings, non-dairy creamers, canned soups and other food products, and may be mentioned on the label as hydrolysed oat or corn flour.
Fruit pur?es and powders: Fruits and fruit pur?es can be effective fat mimics. Pur?es of bananas, plums, pears and apples can perform many of the functions of fat due to their pectin, fibre and sugar content. In particular, the complexes of fibre and pectin provide texture and body. Fruit sugars provide additional solids and water-binding. Added health benefits may include antioxidant activity. Manufacturers have resolved issues with colour by using new spray-drying techniques to produce cream-coloured powders. These replacers may partially or completely replace fat in cookies, muffins, cakes and other bakery mixes. Since these replacers are not modified to the extent others are, their addition must be carefully managed on a case-by-case basis.
Sugars and dextrins: Sugars and dextrins (tapioca, corn, potato and rice derivatives) are traditional ingredients modified to provide enhanced functionality in reduced-fat systems. The degree of digestible carbohydrates determines their ability to lower the overall caloric content as well as fat content.
Corn syrups and maltodextrins are fully digestible carbohydrates that provide structure, viscosity and creaminess, but can also give an undesirable watery mouthfeel.
Fructo-oligosaccharides such as inulin not only replace fat but also provide prebiotic effects and help in the absorption of vitamins.
Gums: Gums are long-chain polymers from plant materials such as seaweed, seeds and tree exudates. They may also be produced by the chemical modification of polysaccharides or from microbial fermentation. They dissolve or disperse in water, increasing viscosity, and, in combination with bulking agents, may be used to reproduce the texture of dispersed fat. Gums most often used in low-fat food include carrageenans, gellan, xanthan, guar and locust bean.
Proteins can act as simple fat replacers, such as gelatin, or be modified (heated and blended at high speed) to mimic the properties of fat, as is the case with Simplesse, a microparticulated whey protein normally available in gel form (about 42 per cent solids) or in powder form. Controlled denaturation using heat or enzymes can change the structure and behaviour of the protein. Such changes can provide characteristics that make them suitable as fat replacers. They can also help stabilise emulsions. Only small amounts are needed, which drops the caloric content of the final product.
The following are examples of protein-based fat replacers.
- Egg whites can act as limited fat extenders in some food products due to their structural properties.
- Gelatin as a fat replacer can provide structure, viscosity and smooth mouthfeel.
- Soy and whey proteins can impart structure, viscosity, creaminess and opacity but a somewhat powdery mouthfeel in some products.
- Microparticulated egg white and milk proteins (eg, Simplesse) can provide structure, viscosity, creaminess and opacity, a clean flavour base and good flavour-release qualities with only one-third the calories of fats. They cannot be used in high-temperature frying, though they may be used in traditional baking and cooking applications, canning, pasteurisation and UHT processing; they work well in ice cream, butter, salad dressings and margarine. Protein blended with gums and food starches can also be an effective option.
The majority of fat-based replacers are emulsifiers, emulsions with little fat or lipid analogues. Emulsifiers stretch the functionality of low-fat levels and replace the functionality of fat when used in combination with other ingredients. Lipid analogues are either triglycerides with tailored configurations to reduce their caloric content, or substances with chemical structures similar to triglycerides but with reduced or zero caloric content. They behave in many ways like normal fats.
Manipulating the composition of the fatty acids esterified to the glycerol reduces the calories while maintaining the chemical structure of the triacylglycerol. Replacing the fatty acids of triglycerides with alternative acids is achieved through hydrolysis and random transesterification of medium-chain and long-chain triglycerides to create these low-calorie fats.
Generally, these fats are neither hydrolysed nor absorbed by the body in the same manner as normal fat and, thus, contribute substantially fewer calories. Physically and chemically they resemble triglycerides, are stable to cooking or frying temperatures, and theoretically replace fat on a one-to-one, gram-for-gram basis.
The following are examples of lipid analogue fat-based replacers:
- Olestra (trade name Olean) is a sucrose polyester designed by Procter and Gamble. The arrangement of sucrose and triglycerides prevents absorption of the fat in the gut. It is approved in the US for use in salted snacks and crackers, and can be used for frying, dough conditioners, oil sprays and flavours.
- Benefat (trade name Salatrim) is made up of short- and long-chain acyl triglyceride molecules. It can be used in chocolate and confections, baked goods, dairy products and snacks, but not for frying.
- Enova Oil (an ADM trademark) has an increased concentration of diacylglycerol, a component metabolised differently from triglycerides, with more being burned directly by the body as energy rather than stored as fat. It can be used for salads and frying.
- Neobee MLT-B (a Stepan Co trademark) is a medium-chain triglyceride that mimics the solid fat index of partially hydrogenated vegetable oil. It has fewer calories and one-eighth the metabolising time of long-chain fats. It uses a unique metabolic pathway, travelling directly to the liver rather than through the lymphatic system, and, thus, does not accumulate as fat in the body.
Fat and food: a long history
Aesthetically, fat provides elusive sensory characteristics of appearance, texture, flavour and mouthfeel. These attributes in many food products tend to suffer with the replacement of fats. While health-consciousness is higher than ever, it is still hard to persuade consumers to try reduced-fat products unless they taste good. Aside from the fat replacers discussed, product developers should also be watching advances in the research on the benefits of healthy fats such as omega oils. These developments, along with a new focus on substituting saturates/trans fatty acids, provide another avenue by which fat replacement in food products can provide benefits to the consumers.
New ingredient development is embracing this challenge and providing product developers with more and better tools to achieve this goal.
Dr. John Michaelides is technical director at Guelph Food Technology Centre. Kathryn Cooper is vice president of marketing and client services at Guelph Food Technology Centre, which provides confidential technical solutions to the food processing industry.
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