Due to the shortcomings of dietary fiber itself, there are shortcomings of low taste, flavor and acceptance when added to food. Resistant starch is similar to starch in color, taste, texture, and flavor, so it can be used as an additive or directly as a food alone without affecting the taste and texture of the food itself, effectively solving the shortcomings of ordinary dietary fibers, and at the same time, it also has functional components, which makes it a hot research topic in the food processing industry.

Resistant Starch, RS for short, is a special polysaccharide compound first discovered in the early 1980s, also known as anti-enzymatic starch, which belongs to a kind of indigestible starch. Resistant starch is mainly classified into five categories, namely physically embedded starch (RS1), natural uncooked starch granules (RS2), regenerated starch (RS3), chemically modified starch (RS4), and starch lipid complexes (RS5).

Applications in bakery products

In order to improve the situation of less dietary fiber in people’s daily diet, the food industry related people add barley flour, a kind of traditional dietary fiber in bread making to improve the nutritional value of bread, but the content of dietary fiber in bread is too high, it will make the bread darker, and the dietary fiber such as gluten, which is often added to the bread, will produce a rough taste, a granular texture, a very dark color, and will also cover the original aroma of food, which is the main reason why it is used in bread. Adding resistant starch to bread can solve these problems.

Maziarz et al. increased the water content of bread made by replacing part of the flour with resistant starch, which resulted in a darker surface color, drier and firmer texture, and greater density, without changing the texture. Due to the high water retention of resistant starch, the addition of pea resistant starch to bread will result in a significant increase in the water absorption of the flour, and the adhesion and hardness of the dough will be improved, while the hardness and chewiness of the bread will be enhanced with the increase of resistant starch, and the acceptance of the consumers will be higher.

Application in cookie making

Laura et al. added resistant starch to cookies because resistant starch has a lower moisture content than flour, contains less wheat protein, and also has a certain degree of water retention, so the higher the proportion of resistant starch, the dough hardness decreases with the increase in the proportion of addition. Higher moisture content and water activity in the cookie system increases the volume of biscuits and makes the texture softer and looser, and the total fiber content of cookies increases.

Resistant starch can dilute the pigment (egg yolk) in the cookie formulation, make the surface color of cookies brighter, and reduce the golden color or melanoidin formed by the interaction of reducing sugar and amino acid or due to the Melad reaction.

Chen Lei et al. made different formulations of cookies and determined their slow-digestible starch content, observing the changes in starch digestibility before and after baking for starch-lipid complex, high straight-chain corn starch, wheat starch, low-gluten flour, and high-gluten flour, respectively. It was concluded that due to the formation of a large number of crystalline structures in the amylose-lipid complex, it was more stable than the structure of high straight-chain starch and wheat starch, and its content of slow-digestible starch was higher. The slowly digestible amylose content of cookies baked with 25 % amylose-lipid complex was higher, up to 23.56 %.

Application in noodle making

Noodles are a kind of food often consumed by people in their daily life, with high starch content, and high-quality noodles not only have high nutritional value, but also have better cooking time and water absorption than other noodles.

The addition of resistant starch granules to noodles can increase the brightness and make the noodles softer, as well as reduce the digestibility of the noodles, but these changes do not affect the texture, toughness, chewiness, and hardness of the noodles, which means that the addition of resistant starch to noodles does not affect the texture of the noodles.

Bustos et al. added RS2 and RS5 to noodles and found that RS5 favored the reduction of cooking losses and RS2 significantly improved the process and nutritional properties of cooked noodles. The addition of 3.96 % RS2 and 12.6 % RS5 produced noodles with cooking losses lower than 6 % and a lower glycemic index, which was acceptable to consumers.

The gelatinization temperature and enthalpy of the noodles with the addition of resistant starch were reduced, and during cooking, the gelatinization rate was accelerated, and the noodles were less viscous with no significant change in hardness. As more resistant starch was added, it made the dough softer, which was attributed to the decrease in gluten index, and the dilution of gluten weakened the cross-linking between proteins and ultimately reduced the cohesion of the gluten network.

As shown by X-ray diffraction, the addition of resistant starch noodles showed increased crystallinity and decreased in vitro digestibility, but the reduced yellowness of the uncooked noodles may reduce the attractiveness of the noodles to consumers.

Application in microencapsulation

Microencapsulation is a packaging technology that encapsulates a substance in a polymer film in a closed structure, protected from the environment. Resistant starch that is not enzymatically degraded in the small intestine acts as a wall material when passing through the gastrointestinal tract, which can protect the encapsulated material from or delay the degradation and absorption by the digestive tract enzyme system for the purpose of releasing it at a specific site.

In addition, resistant starch can be used as a carbon source for colonic microorganisms after entering the colon, and can be degraded to produce short-chain fatty acids such as propionic acid, butyric acid and carbon dioxide which are beneficial to the human body.

In the food industry, probiotic activity can be greatly enhanced by the use of resistant starch-based microencapsulation technology, which encapsulates sensitive substances (e.g., minerals, antioxidants) to isolate them from unfavorable environments.

Used in the preparation of microcapsules of resistant starch is mainly RS2, RS3 and RS4, but also because of its effective protection of probiotic vitality of the anti-enzymatic properties, as a slow-release carrier to provide stable transport and slow-release effect of the crystalline structure as well as a good quality of extrusion and film molding characteristics, is gradually being used in the preparation of microcapsule wall material, often compounded with alginate, embedded and slow-release effect is good, but the application of the field But the field of application is still limited to the food industry.

Puffed food

Adding RS to food can improve the expansion coefficient of extruded cereals and snack foods, so it can be applied to puffed food, which can reduce the adverse effects of hardness, brittleness, and overall poor quality caused by the traditional dietary fiber on food puffing.

It has been pointed out that the expanded volume of oat food increased after adding a certain amount of RS, and the expansion coefficient increased with the increase of RS content within a certain range.

In addition, RS can also improve the soaking resistance of grains, added RS puffed food by milk and other beverages after soaking, the texture of the texture is softened, but can still maintain a good crunchy taste.

Application in fried food

The higher stability of regenerated starch compared with other RS allows it to be better used in fried foods to increase the dietary fiber content and improve the nutritional value of fried foods.

Relevant research shows that when replacing 20% of fried food flour with regenerated starch, the dietary fiber content of fried food flour increases by 8.2%, and can deepen the color of fried food, improve the hardness and crispness of fried food.

Application in dairy products

The water content of cheese with added resistant starch increases and the hardness decreases, but it does not affect the bonding and fluidity of cheese. When the content of resistant starch is increased from 21.3% to 43.2%, the fat content of cheese is reduced from 10% to 0%, and the fat can hardly be seen under the light microscope, so it can be used as a fat substitute for making low-fat cheese.

However, the disadvantage is that the hardness of the cheese increases dramatically. The texture of the cheese deteriorates further when the sample is hot, probably due to the swelling of the starch granules when heated, causing the cheese to stick to the roof of the mouth.

The addition of resistant starch during yogurt fermentation and storage will solidify the yogurt with a more compact structure, increase the elasticity and viscosity indices, aggregate the casein, reduce the amount of whey separation, strengthen the gel network structure, reduce the formation of air holes, and improve the quality of the yogurt while protecting the probiotics.

Sodium Yang et al. found that the use of potato RS as an emulsification stabilizer alone has good color, texture and taste, but the tissue state is not good, and the use of pectin, agar compound can make up for each other’s deficiencies, when the potato RS additive amount of 1.50%, the pectin additive amount of 0.03%, agar additive amount of 0. 15%, the overall quality of yoghurt reaches the best.

Application in meat products

Although resistant starch is mainly used in bakery products, its application in meat products is more significant. Resistant starch forms a gel with myosin in meat, and due to the hydrophilicity of resistant starch and the mobility of water inside the gel, it plays a role in retaining water and juice in meat products, and some studies have shown that polysaccharides such as starch can enhance the viscoelasticity of meat products.

Wang Xixi et al. studied the effect of corn resistant starch on the thermal gelation properties of chicken breast muscle gelatin and found that resistant starch can absorb the water in the gel mixing system, thereby reducing the mobility of the internal gel, forming a continuous, dense, uniform three-dimensional network structure, increasing the modulus of elasticity, and increasing the strength of the gel.

Resistant starch can be used as a fat substitute in low-fat meat products. Addition to fish also proved its feasibility.Acosta-Perez et al. added resistant starch to rainbow trout and found that the whiteness of the fish increased slightly with the addition of resistant starch. This was attributed to the effect of resistant starch in diluting some of the pigments and proteins, thus making the meat color whiter and brighter.

The decrease in malondialdehyde content in fish meat indicates that the addition of resistant starch can delay fat oxidation during storage while improving consumer acceptance. The combination of resistant starch and meat products has good research prospects.

Conclusion

Chinese people consume more than 370 g of starch per day, which is one of the highest intake of starch in the world. Under the advocacy of balanced dietary pattern, the nature of starch needs to be changed appropriately in order to achieve the purpose of balanced nutrition. China has abundant starchy food, with the increasing market demand for dietary fiber-based food, the food processed with resistant as raw material has a broad application prospect.