Fat is one of the three major energy substances and an essential nutrient for the human body, but excessive intake can cause a variety of diseases, such as cardiovascular disease, obesity, diabetes, hypertension and so on. As early as the 1970s, Western countries began to emphasize the control of fat in the proportion of total food energy, the United States proposed that the total intake of fat should be reduced to about 10% of the total energy.

With the enhancement of people’s health consciousness, low-fat or fat-free food came into being, fat substitutes are precisely in line with this requirement and the development of. Fat substitutes can be categorized into 3 types according to their composition; protein-based fat substitutes, carbohydrate-based fat substitutes, and fat-based fat substitutes.

Fat Substitutes

1.1 Protein-based fat substitutes
Protein-based substitutes have some limitations in their application; they cannot be used as cooking oils and their products cannot be deep fried, this is due to the fact that high temperatures denature proteins, thus losing their fat-mimicking properties.

In addition, proteins tend to react chemically with some flavor components, reducing or causing the loss of flavor components. These reactions vary with the proteins used and other ingredients in the food.

Common types: whey protein fat substitutes, micronized protein fat substitutes, soy protein

1.2 Carbohydrate-based fat substitutes
Carbohydrate-based fat substitutes provide a creamy, smooth texture by stabilizing a significant amount of water, primarily through a gel-like matrix, which produces lubricity and flow similar to that of fat, increasing the viscosity and volume of the food. However, they cannot be used for frying foods or dissolving oil-soluble flavor substances. Carbohydrate-based fat substitutes are the safest fat substitutes for consumption.

Common types: starch-based fat substitutes, fiber-based fat substitutes, hemicellulose-based fat substitutes, colloidal fat substitutes, β-glucan fat substitutes

1.3 Fat-based fat substitutes
Fat-based substitutes not only look and feel like fat, but also have fat-like physical properties. They can theoretically replace all or part of the fat in a food.

Common types: emulsifiers, medium chain triglycerides, constructed fats, and calorie-free synthetic fats.

Applications of fat substitutes in food

2.1 Application of fat substitutes in baked goods
In baked goods, fats are used to maintain the physical structure of the product and to provide the sensory and flavor profile of the fat. Fat substitutes are mainly some of the fillers, which serve to increase the firmness of the product. Various celluloses, as well as many cereal and vegetable fibers, meet this requirement. Aqueous colloids, soluble fillers, and sugars can give foods the sensory properties that fats have. Aqueous colloids produce fluidity by forming a paste or colloid.

Colloids and starches are commonly added in the preparation of pastry.Glicksman et al. used colloids and cellulose (extracted from citrus) to make a low-fat, halved-calorie cake.

Pfizer used egg whites and egg spices as well as adjusting the colloid and starch content to achieve satisfactory results. The National Starch Company made fat-free cakes with colloids, starches and emulsifiers (e.g. N-Flate).

In many instances, aqueous colloids are critical in that they not only produce sensory effects, but also increase the volume of the cake and yield a more homogeneous organization. In addition, they extend the shelf life.

2.2 Fat substitutes in meat products
Conventional meat products contain a lot of fat. Hamburgers contain 20% to 30% fat, while hot dogs contain about 15% fat.

Egbe~ et al. used carrageenan to replace the fat in meat patties and produced excellent low-fat meat patties by adding edible modified starch. It is important to consider the organoleptic and textural structure of the food when making low-fat foods. Lower fat content can be obtained by using lean meat or water, but using too much lean meat makes the food tough, dry, and increases the cost of the food, while using water alone softens the food. It has been found that by adding starchy fat substitutes it is possible to make a meat pie containing 10% fat almost indistinguishable organoleptically from one containing 20% fat.

2.3 Fat substitutes in flavorings
The easiest and simplest application of fat substitutes is in flavorings. Condiments are basically oil-in-water emulsion systems flavored with salt, sugar, vinegar and vanilla.

The oils used to replace the flavoring can be selected from a number of aqueous colloids that have the same fluidity as the oil to provide a lubricating, creamy texture. Of course the flavor in a low-fat or fat-free dressing may be different than without substitution, so the flavor must be reconstructed.

One dressing is one in which the oil phase can be completely replaced by a mixture of denatured, high straight-chain corn starch and xanthan gum, which is blended into a 6.1% solution and then dispersed in water with the other ingredients to form a tasty, fluid dressing. A fat-free Italian dressing is made from a mixture of maltodextrin and xanthan gum made from potato starch to replace the fat, resulting in a creamy texture.

2.4 Fat substitutes in frozen foods
Since the 1970s, low-fat ice creams have been developed in response to the requirements of the development of low-calorie foods. The role of aqueous colloids in traditional ice cream products is to stabilize the frozen oil-in-water emulsifier to increase volume and prevent solid-liquid separation. The stabilizer system includes a small amount of carrageenan, and several thickeners such as guar gum, CMC, locust bean gum, etc., which are used in very low amounts.

However, in order to obtain fat-like tissue properties, it is necessary to use large amounts of aqueous colloids and to select different mixtures to simulate fat. One type of fat-free ice cream consists of gel, microcrystalline cellulose and CMC as stabilizers, mixed with sorbitol as a filler to produce a smooth, creamy texture by adjusting the proportions of the components. Dextran can also be used in place of sorbitol. These low-fat or fat-free ice creams can be prepared by the usual methods.

Prospects for fat substitutes

Fat substitutes started late but are developing rapidly. So far, a variety of substitutes have been developed, but unfortunately there is no single fat substitute that can completely replace fat. In order to simulate the taste, texture and other properties of fat well, two or more composite fat substitutes are often added to foods to try to meet the needs.

There are still many problems with fat substitutes, which require the continuous efforts of researchers.
In addition to the development of fat substitutes at the same time, we should also see that fat has an important role in the human body can not be ignored, people still need to consume a certain proportion of fat to meet the needs of the human body metabolism. Therefore, we should take the right attitude towards fat substitutes and use them reasonably to avoid excessive fat intake and maintain the original flavor of food. From the development trend, in the 21st century, the future of the development of fat substitutes will be brilliant.