Resistant starch exists in some natural foods, such as potatoes, bananas and rice. Especially corn starch with high amylose content contains 60% resistant starch. This kind of starch is more difficult to degrade than other starches, and it is digested slowly in the body, absorbed slowly and enters the blood slowly. Its properties are similar to soluble fiber, and it has a certain slimming effect. In recent years, it has been favored by beauty lovers.
Chinese name: resistant starch mbth: resistant starch, also known as: resistant starch function: it has a certain slimming effect. Subordinate: dry starch: raw chestnut resistant starch accounts for 78% of the total starch content. Physical and chemical properties, classification, RS 1, RS2, RS3, RS4, preparation method, hydrothermal treatment method, debranching degradation method, ultrasonic method, microwave radiation method, steam heating method, reuse, flour food, baked food, puffed food, beverage, physical and chemical properties 1) insoluble in water, soluble in 2. 2) the average polymerization degree DPn is 30-200; 3) Amylose crystals are melted at 100 ~ 165℃; 4) X-ray diffraction type is B type; 5) High heat resistance, almost no loss after high-temperature cooking; 6) Low water holding capacity, only 1.4 ~ 2.8 g, which is the lowest among all dietary fibers; 7) The calorie content is low, and the calorific value generally does not exceed10.0 ~10.5 kj/g. Classification According to the latest nutritional classification, starch can be divided into three types: fast digestible starch (RDS), slow digestible starch (SDS) and resistant starch (RS). At present, there is no accurate chemical classification of RS, because the quality of resistant starch is related to the ratio of enzyme to starch, the source of enzyme and hydrolysis conditions, so an optimization standard is needed. At present, most scholars classify resistant starch into four categories according to its source and anti-enzymolysis ability: RS 1, RS2, RS3 and RS4. RS 1 refers to the physically embedded starch, which is the part where starch particles are physically forbidden by mechanical processing and locked on the plant cell wall so that they cannot be acted by amylase. Common in lightly ground cereals, beans and other foods. RS2 refers to resistant starch granules, which are starch with certain granularity, such as raw potato and banana starch. Physical and chemical analysis showed that RS2 had strong resistance to enzyme. RS 1 and RS2 can still be digested and absorbed by amylase after proper treatment. RS3 refers to aged starch, which is a solidified starch polymer formed by cooling gelatinized starch. This resistant starch is divided into two parts: RS3a and RS3b, in which RS3a is solidified amylopectin and RS3b is solidified amylose. RS3b has the strongest resistance to enzymatic hydrolysis, while RS3a can be degraded by amylase after reheating. At present, there are two different explanations for the anti-enzymatic mechanism of RS3. Firstly, the formation of amylose crystals prevents amylase from approaching the glycosidic bond in the crystallization zone, and prevents the binding sites in the active groups of amylase from combining with starch molecules, thus making RS3 have anti-enzymatic properties; Another view is that RS3 can resist enzymatic hydrolysis because the double helix forms strong hydrogen bonds and van der Waals forces between amylose crystals, which makes the molecular structure of RS3 very firm and has strong thermal stability, so it cannot be digested and absorbed in human gastrointestinal tract. RS3 is the most resistant starch, and there are many studies on this kind of starch at home and abroad. RS4 refers to chemically modified starch, which changes the molecular structure of starch through genetic modification or chemical methods and the introduction of some chemical functional groups, such as acetyl starch, hydroxypropyl starch, thermally modified starch and phosphorylated starch. Preparation method In recent 10 years, the research on the preparation of resistant starch at home and abroad has been quite extensive, and there are mainly five preparation methods. Hydrothermal treatment method According to the different heat treatment temperature and moisture content of starch milk, the hydrothermal treatment of starch can be divided into the following five categories: Hydrothermal treatment refers to the process of heat treatment of starch under low moisture condition, with moisture content less than 35% and high temperature, generally 80 ~ 160℃. Toughening treatment, also known as annealing treatment, refers to the heat treatment process in which the water content of starch is more than 40% and the temperature is set below the gelatinization temperature of starch. Autoclave treatment refers to the process that the water content of starch is more than 40% and the solution is treated at a certain temperature and pressure. Vacuum treatment method can be used for large-scale treatment in a short time, without gelatinized starch particles, with high thermal stability and great potential for industrial production. Ultra-high pressure treatment means that under the action of pressure, the double helix structure of type A crystal re-aggregates and partially transforms into type B crystal, but this treatment will not lead to the degradation of molecular weight. The treated starch particles were gelatinized, but their particle structure was maintained and no dissolution occurred. There are two common debranching methods in the preparation of resistant starch by debranching degradation: one is enzymatic debranching, the other is chemical debranching. It is reported that starch is treated with acids (hydrochloric acid, sulfuric acid, nitric acid, etc.). ) has a certain debranching effect, but its debranching effect is not as good as enzymatic debranching. The enzyme used in enzymatic debranching is mainly debranching enzyme, and the most commonly used enzyme is pullulanase, which is a kind of isoamylase. It can hydrolyze α- 1, 6 glycosidic bonds in linear and amylopectin molecules, and the cut α- 1, 6 glycosidic bonds contain at least two α- 1, 4 glycosidic bonds at both ends, so that the hydrolysate of starch contains more free linear molecules, and in the process of starch aging. Ultrasonic method Ultrasonic wave will lead to polymer degradation. On the one hand, ultrasound accelerates the friction between solvent molecules and polymer molecules, leading to the rupture of C-C bonds. On the other hand, the high temperature and high pressure environment caused by the cavitation effect of ultrasonic waves leads to chain fracture. Compared with other degradation methods, the molecular weight distribution of degradation products obtained by ultrasonic degradation is narrow and the purity is high. Microwave radiation It takes less time to treat starch by microwave at a relatively low temperature than by moist heat treatment. Microwave treatment is affected by heating temperature and water content of starch, especially water content is significantly related to heating rate. When the water content is low, the heating rate is very fast; When the moisture content is high, the temperature rise is not significant. Microwave radiation method is a new technology and has a good development prospect. Juscelino treated black beans, red beans and Lima beans with hot steam and high-pressure hot steam respectively. The yield of RS is 19% ~ 3 1%, and its content is 3 ~ 5 times higher than that of original starch, which proves that steam heating is also an effective method to prepare RS. The application of resistant starch has the processing characteristics such as low water holding capacity, which can be used to improve the processing technology of food, increase the brittleness and expansibility of food and improve the texture of the final product. Therefore, it can be used as a functional component of food dietary fiber, and can be added to food to make flavor food and functional food with different characteristics. At present, resistant starch has been applied to flour food, such as bread, steamed bread, steamed buns, macaroni and biscuits. Used as food raw material or dietary fiber fortifier abroad. Among them, the most striking is the application of resistant starch in bread. The bread with resistant starch not only strengthens the dietary fiber composition, but also has better sensory qualities such as pore structure, uniformity, volume and color than the bread with other traditional dietary fibers. Adding resistant starch to macaroni and noodles can improve their cooking resistance, help maintain tough structure and avoid sticking after cooking. Baked food resistant starch has been applied to many gluten foods, such as cakes and biscuits. Resistant starch can not only be used as a dietary fiber fortifier, but also a good structural modifier, giving food a lovely soft feeling. After baking, the cake containing RS has similar water loss, volume and density as the cake containing dietary fiber and oat fiber. Cookie food processing requires low gluten quality, and resistant starch can be added in a large proportion. This diluted flour gluten can reduce the browning opportunity during baking, and make the biscuits containing resistant starch soft, loose and bright, which is beneficial to making health biscuits with the function of resistant starch as the main function. As an improver of puffed brittle food, puffed food resistant starch can not only improve the structural characteristics of food, but also improve the puffing coefficient of puffed cereal food and snack food, making it have unique texture. When the puffed food containing resistant starch is soaked in milk and other beverages, the texture becomes soft, but it will not collapse due to water absorption, so that the grain remains crisp during soaking. Resistant starch can also improve the brittleness of food, especially the food that needs to be reheated after freezing, and its surface brittleness is a crucial quality. The food added with resistant starch has uniform pores, soft central tissue, good sensory quality such as volume and color, and the best brittleness. Beverage resistant starch has good viscosity stability, good rheological properties and low water holding capacity, and can be used as food thickener. Resistant starch is a water-insoluble substance. Resistant starch can be used in viscous and opaque drinks, which can increase the opacity and suspension of drinks, and will not produce sand feeling or cover up the flavor of drinks. Resistant starch is not only a good substrate for the reproduction of probiotics such as Bifidobacterium and Lactobacillus, but also can be used as a bacterial preservative. The number of lactic acid bacteria in yogurt with RS was significantly higher than that in the control group, and the survival rate of bacteria was greatly improved after drinking. In addition, resistant starch can also be used to make soup.