A middle-gi extruded rice cake and a preparation method and application thereof

Abstract

The application discloses a middle GI extruded rice cake and a preparation method and application thereof, and belongs to the technical field of the extruded rice cake processing. The middle GI extruded rice cake comprises the following raw materials in parts by weight: 94-96 parts of rice powder, 4-6 parts of soybean protein isolate and 6-18 parts of short-chain inulin. The application utilizes the synergistic complementation of the plasticizing and lubricating effect of the short-chain inulin and the network structure supporting effect of the soybean protein isolate, reduces the material melting viscosity, promotes the uniform nucleation and sufficient expansion of the gas core, delays starch digestion through the double mechanisms of moisture competition and physical barrier, and through a specific double-screw extrusion and expansion process, a suitable old rice cake with excellent crispness, instant melting, moderate blood glucose generation index, and significant hypoglycemic effect, improved lipid metabolism and liver protection effect verified by experiments is prepared, and the technical bottleneck that the crisp quality and health attributes are difficult to be considered in the prior art is effectively solved, and a new technical path is provided for the development of the suitable old health leisure food.

Description

Technical Field

[0001] This invention belongs to the field of puffed rice cake processing technology, and particularly relates to a medium-GI extruded puffed rice cake, its preparation method and application. Background Technology

[0002] As my country's aging population continues to grow, the elderly population faces the dual health challenges of declining chewing function and reduced blood sugar regulation. On the one hand, declining chewing function leads to specific needs for food texture in the elderly; crumbly, melt-in-your-mouth snacks are more suitable for their physiological characteristics. On the other hand, with age, the elderly experience a weakening of glucose metabolism, significantly increasing the risk of abnormal postprandial blood sugar fluctuations. Long-term consumption of high-glycemic index foods can exacerbate metabolic disorders and increase the risk of complications such as cardiovascular disease. However, most commercially available elderly foods are currently in paste, soup, or liquid / soft form. While this reduces the risk of food poisoning, the limited texture and insufficient sensory experience fail to meet the diverse consumption needs of the elderly. Rice cakes, as a classic puffed snack, with their crumbly texture and rich rice aroma, are highly suitable for the elderly in terms of palatability and safety, possessing the potential to be developed into an age-appropriate snack. However, traditional rice cakes are made primarily from refined rice, which is low in protein and dietary fiber, resulting in an unbalanced nutritional structure. Furthermore, the starch is digested quickly and has a high glycemic index, which can easily cause drastic fluctuations in postprandial blood sugar after consumption. This makes them unsuitable for the elderly, whose risk of postprandial blood sugar fluctuations increases with age, severely limiting their application in the field of age-appropriate foods.

[0003] Currently, some studies have attempted to add protein or dietary fiber to rice cakes to improve their nutritional and quality characteristics. However, most studies involve adding only protein or dietary fiber, and a mature development system for synergistic combinations of these two components has not yet been established. When these two components are added in combination, interactions can easily occur between them, altering the rheological properties of the material during extrusion puffing. This results in reduced puffing degree and a harder texture, failing to simultaneously meet the functional requirements of a crisp, easily disintegrating texture and stable postprandial blood glucose levels required for foods suitable for the elderly. Furthermore, current research on puffed rice cakes focuses primarily on sensory flavor improvement, with little in vivo efficacy verification considering the specific physiological and metabolic characteristics of the elderly population. This makes it difficult to simultaneously achieve excellent chewability, moderate glycemic levels, and the multiple benefits of regulating glucose and lipid metabolism.

[0004] To address the shortcomings of the existing technologies, developing an extruded puffed rice cake suitable for the elderly that combines excellent crispness, a moderate glycemic index, and blood sugar and lipid-lowering effects has become an urgent technical problem to be solved in the field of elderly-friendly snack foods. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a medium-GI extruded puffed rice cake with excellent crispness, melts in the mouth, and has a moderate glycemic index. It is a rice cake suitable for the elderly with significant effects of lowering blood sugar, improving lipid metabolism, and protecting the liver.

[0006] Another object of the present invention is to provide a method for preparing the medium-GI extruded puffed rice cake.

[0007] Another object of the present invention is to provide the application of the medium-GI extruded puffed rice cake in the preparation of products with hypoglycemic, lipid-lowering and / or liver-protective effects.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a medium-GI extruded puffed rice cake, comprising the following raw materials in parts by weight: 94-96 parts rice flour, 4-6 parts soy protein isolate, and 6-18 parts short-chain inulin.

[0009] Preferably, the mass ratio of the short-chain inulin to the mixture of rice flour and soy protein isolate is (6:94) to (15:85).

[0010] Preferably, the rice flour is obtained by crushing and sieving rice; the mesh size of the sieve is 100-140 mesh.

[0011] Preferably, the method for preparing soy protein isolate includes: defatting soy flour; dissolving defatted soy flour in water, adjusting the pH to alkaline, centrifuging, and collecting the supernatant; adjusting the pH to acidic, centrifuging, and collecting the precipitate; dispersing the precipitate in water, adjusting the pH to neutral, and drying to obtain soy protein isolate.

[0012] The present invention also provides a method for preparing the medium-GI extruded puffed rice cake, comprising: mixing rice flour, soy protein isolate and short-chain inulin to obtain a mixed powder; adding water to the mixed powder and extruding it by twin-screw extrusion; and cutting and drying the extrudate to obtain a medium-GI extruded puffed rice cake.

[0013] Preferably, after adding water to the mixed powder, the moisture content of the material is adjusted to 12%~16%.

[0014] Preferably, the conditions for the twin-screw extrusion puffing include: extrusion temperature of 110~150℃ and screw speed of 12~24Hz.

[0015] The present invention also provides an application of the medium-GI extruded puffed rice cake in the preparation of products with hypoglycemic, lipid-lowering and / or liver-protective effects.

[0016] Preferably, the medium-GI extruded puffed rice cake exerts its hypoglycemic effect by reducing fasting blood glucose, serum insulin levels, area under the oral glucose tolerance test curve, and increasing liver glycogen levels.

[0017] Preferably, the medium-GI extruded puffed rice cake exerts a lipid-lowering effect by reducing serum triglycerides, total cholesterol, and low-density lipoprotein cholesterol, while increasing high-density lipoprotein cholesterol.

[0018] Preferably, the medium-GI extruded puffed rice cake exerts a liver-protective effect by reducing serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities.

[0019] The beneficial effects of this invention are: This invention uses rice flour as the starch matrix and, with the addition of soy protein isolate, introduces a specific proportion of short-chain inulin. Utilizing the synergistic and complementary effects of the plasticizing and lubricating effects of short-chain inulin and the network structure support of soy protein isolate, it reduces the melt viscosity of the material, promotes uniform nucleation and full puffing, while simultaneously delaying starch digestion through a dual mechanism of water competition and physical barriers. A specific twin-screw extrusion puffing process is then used to prepare a crispy, melt-in-your-mouth rice cake with a moderate glycemic index. Animal experiments have confirmed its significant effects in lowering blood sugar, improving lipid metabolism, and protecting the liver. This invention effectively solves the technical bottleneck of existing technologies where crispness and health attributes are difficult to balance, providing a new technical path for the development of healthy and leisure foods suitable for the elderly. Attached Figure Description

[0020] Figure 1 The results show the determination of crispness and hardness of rice cakes in each group.

[0021] Figure 2 The results of the puffing degree and bulk density measurements of rice cakes in each group are shown.

[0022] Figure 3 The results show the water absorption rate of each group of rice cakes.

[0023] Figure 4 The results show the digestibility of each group of rice cakes.

[0024] Figure 5 Results of the blood sugar lowering efficacy test of rice cakes in each group.

[0025] Figure 6 Results of the determination of the lipid metabolism improvement effect of rice cakes in each group. Detailed Implementation

[0026] This invention provides a medium-GI extruded puffed rice cake, comprising the following raw materials in parts by weight: 94-96 parts rice flour, 4-6 parts soy protein isolate, and 6-18 parts short-chain inulin.

[0027] In this invention, the rice flour is preferably obtained by crushing and sieving rice. The crushing method is not particularly limited, but in some embodiments, it preferably includes crushing the rice raw material in a high-speed crusher. The rotational speed of the high-speed crusher is preferably 22,000~26,000 r / min, for example 23,000, 24,000 or 25,000 r / min, and the operating mode is preferably intermittent, with each run lasting 25~35 seconds, for example 30 seconds, with an interval of 1.5~2.5 minutes, for example 2 minutes, for a total of 1~3 runs, for example 2 runs. The sieve mesh size is preferably 100~140 mesh, for example 120 mesh.

[0028] In this invention, the preferred method for preparing soy protein isolate includes: defatting soy flour; dissolving defatted soy flour in water, adjusting the pH to alkaline, centrifuging, and collecting the supernatant; adjusting the pH to acidic, centrifuging, and collecting the precipitate; dispersing the precipitate in water, adjusting the pH to neutral, and drying to obtain soy protein isolate.

[0029] The defatting process preferably involves defatting with hexane, and the preferred ratio of soybean flour to hexane is 1g:2-5mL, for example, 1g:3mL or 1g:4mL. After defatting, the defatted soybean flour is dissolved in water; the preferred mass ratio of defatted soybean flour to water is 1:(8-12), for example, 1:9, 1:10 or 1:11. After dissolution, the pH is adjusted to alkaline, preferably to 7.5-8.5, for example, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3 or 8.4. In some embodiments, NaOH is preferred for adjustment. After adjusting to alkaline, the mixture is centrifuged, and the supernatant is collected. The centrifugation conditions preferably include centrifugation at 4000-6000g for 10-20min, for example, centrifugation at 5000g for 15min. The pH of the supernatant is adjusted to acidic, preferably to 4-5, such as 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, or 4.9. In some embodiments, HCl is preferred for adjustment. After adjustment to acidic, the mixture is centrifuged to collect the precipitate. The centrifugation conditions preferably include centrifugation at 4000-6000g for 10-20 min, for example, centrifugation at 5000g for 15 min. The precipitate is dispersed in water, and the pH is adjusted to neutral, preferably using NaOH. After adjustment to neutral, the mixture is dried to obtain soy protein isolate; the drying method preferably includes freeze-drying.

[0030] In some specific embodiments, the protein content of the soy protein isolate is preferably 90% to 95%, such as 91%, 92%, 93% or 94%, as determined by the Kjeldahl method.

[0031] In this invention, the short-chain inulin has a DP ≤ 10. In some specific embodiments, the short-chain inulin is purchased from Beneo Ltd. in Belgium, CAS No. 9005-80-5, and the product name is Orafti HSI Highly Soluble Short-Chain Inulin.

[0032] In this invention, the rice flour is preferably 94-96 parts by weight, for example, 95 parts; the soy protein isolate is preferably 4-6 parts by weight, for example, 5 parts; and the short-chain inulin is preferably 6-18 parts by weight, for example, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 parts. In some embodiments, the rice flour and soy protein isolate are mixed to obtain SPI-rice flour mixed powder; the mass ratio of the short-chain inulin to the SPI-rice flour mixed powder is preferably (6:94) to (15:85), for example, 7:93, 8:92, 9:91, 10:90, 11:89, 12:88, 13:87, or 14:86. Insufficient soy protein isolate significantly delays starch digestion and doesn't effectively improve texture, while excessive amounts lead to high melt viscosity, hindered puffing, increased product hardness, and decreased crispness, failing to meet the dual requirements of sugar reduction and crispness. Similarly, insufficient short-chain inulin fails to effectively regulate rheological properties and improve puffing, while excessive amounts disrupt the internal protein network structure, reducing bubble wall stability and causing structural collapse and poor texture after puffing. This invention adjusts the specific ratio of short-chain inulin and soy protein isolate to form a synergistic system with complementary functions. Short-chain inulin's plasticizing, lubricating, and viscosity-reducing puffing effects, combined with the network structure support and bubble-stabilizing effects of soy protein isolate, simultaneously achieve multiple benefits: lowering the glycemic index, improving crispness, and improving lipid metabolism. Furthermore, a systematic formulation design is implemented to address the physiological characteristics and nutritional needs of the elderly, ensuring stable and controllable product quality and health benefits.

[0033] Soy protein isolate, a widely available, safe, and non-toxic high-quality plant protein, contains a complete range of amino acids. During extrusion puffing, soy protein isolate can compete with starch for free water in the system and, after thermal denaturation, form a network structure within the continuous starch phase, acting as a physical barrier. This effectively slows down starch digestion, lowers the glycemic index, and simultaneously improves melt mechanical strength and enhances bubble wall stability, providing a material basis for improving the texture and nutritional properties of rice cakes. Inulin, a natural soluble dietary fiber, boasts advantages such as good water solubility and excellent processing performance. Its molecular structure is rich in hydroxyl groups, which can competitively bind with weakly bound water in the starch system through hydrogen bonds, forming a coating layer on the starch granule surface. This inhibits starch water absorption, swelling, and gelatinization, reduces material viscosity, improves processing fluidity, and simultaneously slows down the enzymatic hydrolysis rate of starch, stabilizing postprandial blood glucose levels. Short-chain inulin, due to its lower degree of polymerization and shorter molecular chains, mainly plays a plasticizing and lubricating role in the system. It can more efficiently reduce melt viscosity, promote uniform nucleation and full expansion of gas nuclei, and is more conducive to forming a delicate, uniform, crisp, and porous structure. It has greater advantages in improving the texture and regulating the digestibility of rice cakes. The core components of the GI extruded puffed rice cake in this invention are rice flour, soy protein isolate, and short-chain inulin. Rice flour serves as the starch matrix, while soy protein isolate improves texture and delays starch digestion by competitively binding water and forming a network structure after thermal denaturation. Short-chain inulin, through its hydroxyl groups in its molecular structure, competitively binds to the weakly bound water in the starch system, forming a coating layer on the surface of starch particles. This plasticizing and lubricating effect inhibits starch water absorption and swelling, gelatinization, reduces material viscosity, improves fluidity, and delays starch enzymatic hydrolysis.

[0034] The present invention also provides a method for preparing the medium-GI extruded puffed rice cake, comprising: mixing rice flour, soy protein isolate and short-chain inulin to obtain a mixed powder; adding water to the mixed powder and extruding it by twin-screw extrusion; and cutting and drying the extrudate to obtain a medium-GI extruded puffed rice cake.

[0035] In this invention, the mixing method is not particularly limited. In some embodiments, rice flour and soy protein isolate are first thoroughly mixed to obtain SPI-rice flour mixed powder; then short-chain inulin is thoroughly mixed with SPI-rice flour mixed powder to obtain mixed powder.

[0036] In this invention, after adding water to the mixed powder, the moisture content of the material is adjusted to 12%~16%, for example, 13%, 14% or 15%. This moisture range ensures that the material obtains the best degree of puffing and crispy texture during extrusion puffing, while avoiding scorching and clogging due to too low moisture (<12%), or insufficient puffing power and sticky and soft product texture due to too high moisture (>16%).

[0037] In this invention, the preferred conditions for the twin-screw extrusion puffing include: an extrusion temperature of 110~150℃, for example, 115, 120, 125, 130, 135, 140 or 145℃; and a screw speed of 12~24Hz, for example, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 or 23Hz. The die specifications for the twin-screw extrusion puffing are not particularly limited. In some embodiments, the width of the die is preferably 15~25mm, for example, 20mm, and the height is preferably 0.5~1.5mm, for example, 1mm.

[0038] The medium-GI extruded puffed rice cake prepared by the method of this invention has a loose and porous honeycomb structure with uniform pore distribution and thin, continuous and intact pore walls. This structure is the result of the material being extruded in the extruder, where short-chain inulin competitively binds weakly bound water through hydrogen bonding, inhibiting excessive starch gelatinization and forming a low-viscosity melt. When the pressure drops sharply at the die, the gas nuclei are uniformly formed and fully puffed. The rice cake is uniformly off-white or light yellow in color, with a smooth surface, uniform pores, and no obvious scorching, hard lumps, or breakage. Under the test conditions of probe TA / 0.25S, trigger force 5g, pre-test speed 1mm / s, mid-test speed 1mm / s, and compression degree 50%, the brittleness is 132.11~136.19g, the hardness is 175.52~179.03g, and the bulk density is 0.14~0.16g / mL. Based on the ratio of the average thickness of the rice cake after extrusion to the die height of 1mm, the degree of expansion is 9.51~9.57. Based on the weight gain of the same mass of rice cake after soaking in water for 30s, the water absorption rate is 2.62~2.65g / 30s. The medium-GI extruded puffed rice cake prepared by this invention has a predicted glycemic index of 62.22~63.25, which is considered a medium-GI level. The medium-GI extruded puffed rice cake prepared by this invention can be quickly disintegrated by saliva after entering the mouth, without the need for strong chewing, and is safe to swallow. It is suitable for elderly people with weak chewing ability and is an age-appropriate medium-GI extruded puffed rice cake.

[0039] The present invention also provides an application of the medium-GI extruded puffed rice cake in the preparation of products with hypoglycemic, lipid-lowering and / or liver-protective effects.

[0040] In this invention, after intervening with the diet of hyperglycemic model mice using the aforementioned medium-GI extruded puffed rice cake for 6 weeks, fasting blood glucose decreased by 27.59%–28.15%, serum insulin levels decreased by 37.12%–37.92%, the area under the oral glucose tolerance test (AUTP) decreased by 22.05%–22.78%, and liver glycogen levels increased by 52.15%–52.66%. The GI extruded puffed rice cake in this invention can exert a hypoglycemic effect by reducing fasting blood glucose, serum insulin levels, the AUTP area, and increasing liver glycogen levels.

[0041] In this invention, after intervening with the diet of hyperglycemic model mice using the aforementioned medium-GI extruded rice cake for 6 weeks, serum triglycerides decreased by 29.48%~29.62%, total cholesterol decreased by 26.97%~27.02%, low-density lipoprotein cholesterol decreased by 43.87%~43.92%, and high-density lipoprotein cholesterol increased by 75.12%~75.89%; serum alanine aminotransferase (ALT) activity decreased by 30.14%~30.85%, and aspartate aminotransferase (AST) activity decreased by 27.01%~27.56%. The GI extruded rice cake in this invention can exert a lipid-lowering effect by reducing serum triglycerides, total cholesterol, and low-density lipoprotein cholesterol, and increasing high-density lipoprotein cholesterol; the GI extruded rice cake in this invention can exert a liver-protective effect by reducing serum ALT and AST activities.

[0042] In this invention, the type of product is not specifically limited, but preferably includes health foods or pharmaceuticals. The product may also include excipients conventionally acceptable in the food or pharmaceutical fields; these excipients are not specifically limited and can be conventionally selected according to actual needs.

[0043] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Unless otherwise specified, the following embodiments are all conventional methods.

[0045] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0046] In the following examples, the rice was purchased from Wuchang Jinhe Rice Industry Co., Ltd.; the short-chain inulin with a DP≤10 was purchased from Beneo Ltd. in Belgium, CAS: 9005-80-5, product name: Orafti HSI Highly Soluble Short-Chain Inulin.

[0047] In the following examples, the preparation method of soy protein isolate was as follows: soybeans were ground into powder and then defatted with hexane at a ratio of 1:3 (w / v, g / mL). The defatted soybean powder was dissolved in 10 times its volume of distilled water and adjusted to an alkaline suspension of pH 8.0 with 2 mol / L NaOH. The suspension was centrifuged at 5000g for 15 min. The supernatant was collected, and the pH was adjusted to 4.5 with 2 mol / L HCl and centrifuged at 5000g for 15 min. The precipitate was dispersed in distilled water, and the pH was adjusted to neutral with 2 mol / L NaOH before freeze-drying to obtain the soy protein isolate sample. The protein content of the finally dried soy protein isolate powder was determined to be 92% by the Kjeldahl method.

[0048] Example 1 A medium-GI extruded puffed rice cake is prepared by the following method: Rice raw material was placed in a high-speed grinder (Tianjin Tester Instrument Co., Ltd., FW-135) and ground intermittently at a speed of 24000 r / min (30s each time, 2 times in total, with a 2min interval), for a total of 60s to obtain rice flour; the rice flour was then sieved using a 120-mesh sieve to obtain sieved rice flour. Take 94g of sieved rice flour and 6g of soy protein isolate and mix them thoroughly to obtain a 6% SPI-rice flour mixture. Mix short-chain inulin with the SPI-rice flour mixture at a ratio of 12:88 (w / w) to obtain a 12% short-chain inulin-SPI-rice flour mixture. Add water to the short-chain inulin-SPI-rice flour mixture to adjust the moisture content of the material to 15%, and then extrude it using a twin-screw extruder. The process conditions are: extrusion temperature 140℃, screw speed 21Hz, die width 20mm, and die height 1mm. The extrudate is then cut, shaped, and dried to obtain extruded rice cakes.

[0049] Example 2 A medium-GI extruded puffed rice cake is prepared by the following method: After the rice raw material is pulverized by a high-speed pulverizer, the rice flour is sieved using a 120-mesh sieve, and the pulverization method is the same as in Example 1. Take 96g of rice flour and 4g of soy protein isolate and mix them thoroughly to obtain a 4% SPI-rice flour mixture. Mix short-chain inulin with the SPI-rice flour mixture at a ratio of 6:94 (w / w) to obtain a 6% short-chain inulin-SPI-rice flour mixture. Add water to the short-chain inulin-SPI-rice flour mixture to adjust the moisture content of the material to 12%, and then extrude it using a twin-screw extruder. The process conditions are: extrusion temperature 120℃, screw speed 18Hz, die width 20mm, and height 1mm. The extrudate is cut, shaped, and dried to obtain extruded rice cakes.

[0050] Comparative Example 1 An extruded puffed rice cake, prepared by the following method: After the rice raw material is pulverized by a high-speed grinder, the rice flour is sieved using a 120-mesh sieve, and the pulverization method is the same as in Example 1. 92g of rice flour and 8g of soy protein isolate are thoroughly mixed to obtain an 8% SPI-rice flour mixture. Short-chain inulin and the SPI-rice flour mixture are then thoroughly mixed at a ratio of 6:94 (w / w) to obtain a 6% short-chain inulin-SPI-rice flour mixture. Water is added to the short-chain inulin-SPI-rice flour mixture to adjust the moisture content to 15%, and the mixture is then extruded and expanded using a twin-screw extruder. The process conditions are: extrusion temperature 120℃, screw speed 18Hz, die width 20mm, and die height 1mm. The extrudate is then cut, shaped, and dried to obtain extruded puffed rice cakes.

[0051] Comparative Example 2 An extruded puffed rice cake, prepared by the following method: After the rice raw material was pulverized by a high-speed grinder, the rice flour was sieved using a 120-mesh sieve, and the pulverization method was the same as in Example 1. 94g of rice flour and 6g of soy protein isolate were thoroughly mixed to obtain a 6% SPI-rice flour mixture. Short-chain inulin and the SPI-rice flour mixture were then thoroughly mixed at a ratio of 3:97 (w / w) to obtain a 3% short-chain inulin-SPI-rice flour mixture. Water was added to the short-chain inulin-SPI-rice flour mixture to adjust the moisture content to 15%, and the mixture was then extruded and expanded using a twin-screw extruder. The process conditions were: extrusion temperature 140℃, screw speed 21Hz, die width 20mm, and die height 1mm. The extrudate was cut, shaped, and dried to obtain extruded rice cakes.

[0052] Comparative Example 3 An extruded puffed rice cake, prepared by the following method: After the rice raw material is pulverized by a high-speed pulverizer, the rice flour is sieved using a 120-mesh sieve, and the pulverization method is the same as in Example 1. Take 96g of rice flour and 4g of soy protein isolate and mix them thoroughly to obtain a 4% SPI-rice flour mixture. Add water to the SPI-rice flour mixture to adjust the moisture content of the material to 12%, and then extrude it using a twin-screw extruder. The process conditions are: extrusion temperature 120℃, screw speed 18Hz, die width 20mm, and height 1mm. The extrudate is cut, shaped, and dried to obtain extruded puffed rice cakes.

[0053] Comparative Example 4 An extruded puffed rice cake, prepared by the following method: After the rice raw material is pulverized by a high-speed pulverizer, the rice flour is sieved using a 120-mesh sieve, and the pulverization method is the same as in Example 1. Short-chain inulin and rice flour are thoroughly mixed at a ratio of 6:94 (w / w) to obtain a 6% short-chain inulin-rice flour mixture. Water is added to the short-chain inulin-rice flour mixture to adjust the material moisture content to 15%, and the mixture is then extruded and puffed by a twin-screw extruder under the following conditions: extrusion temperature 120℃, screw speed 18Hz, die width 20mm, and die height 1mm. The extrudate is then cut, shaped, and dried to obtain extruded puffed rice cakes.

[0054] Experimental Example 1 The textural properties, degree of puffing, water absorption rate, digestive properties, hypoglycemic effect, and lipid metabolism improvement and liver protection effects of the extruded puffed rice cakes prepared in Examples 1-2 and Comparative Examples 1-4 were determined respectively.

[0055] 1. Detection Method (1) Determination of the crispness and hardness of extruded puffed rice cakes The crispness and hardness of rice cakes were determined using a texture analyzer. Appropriately sized rice cakes were placed on the testing platform, and a TA / 0.25S probe was used for testing. The testing parameters were: probe height 20 mm, trigger force 5 g, pre-test velocity 1 mm / s, mid-test velocity 1 mm / s, post-test velocity 1 mm / s, and compression degree 50%; the data acquisition frequency was 500 pp / s. Each group was measured three times, and the average value was taken.

[0056] (2) Determination of water absorption rate of extruded puffed rice cake Weigh out rice cakes of equal mass (denoted as M1) that are uniform in shape and size, and fix them in a strainer. Prepare a basin of distilled water, and completely immerse the strainer with the rice cakes in the water for 30 seconds. Quickly remove the rice cakes, wipe off excess water, and weigh them (denoted as M2). Calculate the water absorption rate using the formula. Each sample was measured three times, and the average value was calculated. The formula for calculating the water absorption rate is as follows: (3) Determination of the degree of puffing and bulk density of extruded rice cakes The average thickness (denoted as H1) of each rice cake was measured using a high-precision vernier caliper and a five-point method. Each sample was measured three times, and the average value was calculated. The height at the extruder die was taken as the initial thickness of the unexpanded rice cake before extrusion (denoted as H2 = 1.0 mm). The degree of expansion was determined by calculating the ratio of the average thickness of the rice cake after extrusion (H1) to the initial thickness of the rice cake before extrusion (H2). The calculation formula is as follows: The bulk density of rice cakes was determined using the rapeseed displacement method. First, a piece of rice cake was accurately weighed (denoted as M). It was then placed in a graduated cylinder containing a known volume (denoted as V1) of dried rapeseed, ensuring the rapeseed completely submerged the sample. The cylinder was shaken to ensure the rapeseed fully filled the voids, and the total volume V2 was recorded. The sample volume is V2 - V1. Each sample was measured in triplicate, and the average value was taken. The formula for calculating the bulk density is as follows: (4) Determination of the digestibility of extruded puffed rice cakes Add 500 mg of sample powder to 50 mL centrifuge tubes, then add 10 mL of sodium acetate buffer (0.2 mol / L, pH 5.2). Place the centrifuge tubes in a 37°C water bath and shake at 200 rpm for 10 min. Next, add 10 mL of pre-prepared pepsin solution (42 mg / mL) to each centrifuge tube and react for 30 min. After the reaction, thoroughly mix the reaction solution, then immediately and accurately pipette 0.5 mL into a 10 mL centrifuge tube and add 5 mL of anhydrous ethanol to inactivate the enzyme. Centrifuge the 10 mL tubes at 3000 rpm for 15 min, and retain the supernatant for analysis (the glucose content in the supernatant represents the free glucose content in the sample, i.e., the glucose content at 0 min of reaction). After the above enzyme inactivation operation, add 10 mL of 0.05 mol / L NaOH solution to each 50 mL centrifuge tube to neutralize the reaction solution. Then, 10 mL of a mixed enzyme solution containing trypsin and glucosidase was added to 50 mL centrifuge tubes. At 10, 20, 40, 60, 90, 120, 180, and 240 min, the reaction solution was thoroughly shaken, and 0.5 mL of the reaction solution was accurately pipetted, the enzyme was inactivated, and the solution was centrifuged to obtain the supernatant for measurement. Finally, the glucose content (Gt) was determined at 510 nm using a glucose detection kit (GOPOD). The specific method is as follows: 30 μL of the supernatant from each of the above time periods was placed in a 5 mL centrifuge tube, and 3 mL of glucose detection reagent was added to each tube. The centrifuge tubes were then placed in a 37°C water bath for 15 min. Finally, the absorbance was measured at 510 nm using a UV spectrophotometer, and the glucose content was calculated.

[0057] Note: The pepsin solution is prepared by adding 420 mg of pepsin (enzyme activity 30000 U / g) to 10 mL of 0.05 mol / L HCl, mixing thoroughly, and storing in a refrigerator at 4°C for later use.

[0058] Hydrolysis rate (%) = Gt × 0.9 / TS × 100% Where Gt is the amount of glucose released at time t (0~180min), and TS is the total starch content in the sample.

[0059] The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) are calculated according to the following formula: RDS(%) = (G20 - FG) × 0.9 / TS × 100% SDS(%)=(G120-G20)×0.9 / TS×100% RS(%)=[TS–(RDS+SDS)]×0.9 / TS×100% Wherein, G20 is the glucose content (mg) generated when the sample is hydrolyzed for 20 min, FG is the free glucose content (mg) in the sample, and G120 is the glucose content (mg) generated when the sample is hydrolyzed for 120 min.

[0060] The starch hydrolysis rate curve can be fitted with a first-order kinetic equation for analyzing the k and C∞ values ​​of the enzymatic hydrolysis reaction: Ct=C∞(1-e -kt ) Where Ct (%) is the digestibility of the sample at time t (min), C∞ is the estimated starch digestibility at the reaction endpoint, and k (min) -1 () is the digestion rate constant.

[0061] The C∞ and k values ​​for each sample are estimated based on data obtained from in vitro digestibility measurements.

[0062] The area under the hydrolysis curve and the x-axis (AUC) is calculated using the following formula: AUC=C∞(tf-t0)-(C∞ / k)[1-exp[-k(tf-t0)]] In the formula: tf is the final time of starch hydrolysis (180 min in this experiment), and t0 is the initial time (0 min).

[0063] Therefore, HI is defined as the ratio of the area under the hydrolysis curve of the sample to the corresponding area of ​​the reference food (white bread), and the eGI is calculated using the following equation: eGI = 39.71 + 0.549HI (5) Mouse feeding, modeling, grouping and intervention experiments Eighty male C57BL / 6J mice (specific pathogen-free, SPF grade, approximately 6 weeks old), along with standard diets, high-sugar, high-fat diets, and bedding, were purchased from Changchun Yisi Laboratory Animal Technology Co., Ltd. (Certificate No. SCXK(Ji)2023-0002). The mice were housed under controlled conditions: room temperature was maintained at 25±2℃, relative humidity at 60%–70%, a 12h / 12h light / dark cycle was used, and ample food and water were provided for one week for acclimatization. All experimental procedures were strictly conducted in accordance with the National Institutes of Health (NIH) Guidelines for the Care and Use of Laboratory Animals (8th edition, 2011, ISBN 10:0-309-15400-6) and approved by the Laboratory Animal Ethics Committee of Harbin University of Commerce.

[0064] Model establishment: After one week of acclimatization, 10 mice were randomly selected from 80 mice to serve as the normal control group (NC), fed a standard diet. The remaining 70 mice were fed a high-sugar, high-fat diet to establish a hyperglycemic mouse model. Sufficient food and water were provided during the modeling period, and the mice had free access to food. After 8 weeks of continuous feeding, the mice were fasted for 12 hours (with free access to water). Fasting blood glucose levels were then measured in the high-sugar, high-fat diet mice via tail vein sampling. A successful model was defined as a blood glucose level exceeding 8.5 mmol / L, significantly different from the NC group. Mice that did not successfully establish the model and those that died naturally were discarded. The mice were then grouped according to the number of mice that successfully established the model.

[0065] Grouping: The successfully modeled mice (56 mice) were randomly divided into 7 groups (n=8 per group), including: model group (high sugar and high fat diet), Example 1 group (20% high sugar and high fat diet + 80% Example 1 rice cake), Example 2 group (20% high sugar and high fat diet + 80% Example 2 rice cake), Comparative Example 1 group (20% high sugar and high fat diet + 80% Comparative Example 1 rice cake), Comparative Example 2 group (20% high sugar and high fat diet + 80% Comparative Example 2 rice cake), Comparative Example 3 group (20% high sugar and high fat diet + 80% Comparative Example 3 rice cake), and Comparative Example 4 group (20% high sugar and high fat diet + 80% Comparative Example 4 rice cake).

[0066] (6) Collection of mouse serum and tissue samples Serum sample collection: After the 15th week of feeding, all mice were fasted but allowed free access to water for 12 hours. Mice were anesthetized by intraperitoneal injection of 10% tribromoethanol (300 mg / kg), and blood was then rapidly collected from the orbital vein using a capillary tube. The blood samples were collected into centrifuge tubes containing a coagulant and incubated at 4°C for 30 min. Then, the tubes were centrifuged at 4°C at 6000 rpm for 20 min, and the supernatant serum sample was collected. The sample was then immediately frozen at -80°C for later use.

[0067] (7) Measurement of blood glucose changes in mice Modeling was completed and mice were grouped at week 9, followed by a 6-week intervention period. Postprandial blood glucose changes in mice were measured before intervention (week 0) and at the end of intervention (week 6). Mice were fasted for 12 hours but allowed free water before testing, and fasting blood glucose was measured using a blood glucose analyzer via tail vein sampling.

[0068] (8) Determination of serum biochemical indicators in mice The collected mouse serum was tested using various test kits. The main biochemical indicators to be measured were four serum lipid indicators: triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), as well as serum insulin level, alanine aminotransferase (ALT) level, and aspartate aminotransferase (AST) level.

[0069] (9) Oral glucose tolerance test in mice Modeling was completed and mice were grouped at week 9, followed by a 6-week intervention period. Oral glucose tolerance was measured at the end of the intervention (week 6). Mice were fasted for 12 hours but allowed free access to water before the test. They were then administered a 50% glucose standard solution by gavage at 2 g / kg body weight. Blood samples were collected from the tail vein at 0, 15, 30, 60, and 120 minutes after gavage, and blood glucose levels were measured using a blood glucose analyzer. Blood glucose curves were plotted, and the area under the curve (AUC) was calculated.

[0070] (10) Measurement of liver glycogen levels in mice Take 100 mg of liver tissue, add 1 mL of 5% trichloroacetic acid, homogenize thoroughly to extract glycogen and terminate the enzymatic reaction. Centrifuge the homogenate at 6000 r / min for 15 min and collect the supernatant. Take 0.5 mL of the supernatant, add 1.5 mL of anhydrous ethanol, mix thoroughly, and let stand at 4℃ for 30 min. Centrifuge at 6000 r / min for 15 min, remove the supernatant, and the resulting precipitate is liver glycogen. Then add 0.5 mL of distilled water to the liver glycogen precipitate, shake thoroughly, add 1.5 mL of anthrone reagent, heat in a boiling water bath (100℃) for 10 min, and immediately stop the colorimetric reaction by placing it in an ice bath. Then measure the absorbance at a wavelength of 620 nm, plot a standard curve with standard glucose solution, and calculate the liver glycogen content according to the standard curve. The result is expressed as mg / g liver tissue.

[0071] 2. Experimental Results (1) Brittleness and hardness The crispness and hardness of the extruded puffed rice cakes from Examples 1-2 and Comparative Examples 1-4 were characterized, and the results are as follows: Figure 1 As shown (each experiment was conducted three times, and the average value was taken; different lowercase letters indicate significant differences (P<0.05)). It can be seen that Examples 1 and 2 had lower hardness, at 179.03±4.17g and 175.52±2.09g respectively; Examples 1 and 2 also had the lowest crispness, at 132.11±5.06g and 136.19±10.06g respectively, showing significant differences from the other comparative examples (P<0.05), indicating that Examples 1 and 2 have the optimal crisp texture.

[0072] (2) Expansion degree and bulk density The degree of puffing and bulk density of the extruded puffed rice cakes of Examples 1-2 and Comparative Examples 1-4 were characterized, and the results are as follows: Figure 2 As shown (each experiment was conducted three times, and the average value was taken; different lowercase letters indicate significant differences (P<0.05)). It can be seen that Examples 1 and 2 had the highest degree of expansion, 9.51±0.23 and 9.57±0.35 respectively; Examples 1 and 2 had the lowest bulk density, 0.14±0.02 g / mL and 0.16±0.02 g / mL respectively, showing significant differences from the other comparative examples (P<0.05), indicating that Examples 1 and 2 had the best expansion effect.

[0073] (3) Water absorption rate The water absorption rate of the extruded puffed rice cakes of Examples 1-2 and Comparative Examples 1-4 was characterized, and the results are as follows: Figure 3 As shown (each experiment was conducted three times, and the average value was taken; different lowercase letters indicate significant differences (P<0.05)). It can be seen that Example 1 and Example 2 had the highest water absorption rates, 2.65±0.03g / 30s and 2.62±0.03g / 30s, respectively, which were significantly different from the other comparative examples (P<0.05), indicating that Example 1 and Example 2 were the most easily disintegrated in the oral cavity.

[0074] (4) Digestive characteristics The digestibility of the extruded puffed rice cakes from Examples 1-2 and Comparative Examples 1-4 was characterized, and the results are as follows: Figure 4 As shown (each experiment was conducted three times, and the average value was taken; different lowercase letters indicate significant differences (P<0.05)). It can be seen that the predicted glycemic indexes of Examples 1 and 2 were 62.22±0.95 and 63.25±0.35, respectively, which are at a medium GI level; the proportions of rapidly digestible starch were 50.36%±0.50% and 51.01%±0.70%, respectively; the proportions of slowly digestible starch were 22.06%±0.40% and 21.17%±0.26%, respectively; and the proportions of resistant starch were 28.17%±0.3% and 27.98%±0.31%, respectively.

[0075] (5) Blood sugar lowering effect The hypoglycemic effects of the extruded rice cakes from Examples 1-2 and Comparative Examples 1-4 were characterized. A hyperglycemic model was established in male C57BL / 6J mice. The successfully modeled mice were randomly divided into groups (n=8). Each group was treated with rice cakes from the examples or comparative examples, replacing 80% of their diet for 6 weeks. Fasting blood glucose and various metabolic indicators were measured before and after the intervention. The percentage decrease or increase in indicators in each group compared to the model group was calculated. The results are as follows: Figure 5As shown (average values ​​are taken for each group of experiments, and different lowercase letters indicate significant differences (P<0.05)). It can be seen that after the interventions in Examples 1 and 2, fasting blood glucose decreased by 27.59%±0.56% and 28.15%±0.32%, respectively; serum insulin levels decreased by 37.92%±0.99% and 37.12%±0.84%, respectively; the area under the curve of the oral glucose tolerance test decreased by 22.78%±0.12% and 22.05%±0.32%, respectively; and liver glycogen levels increased by 52.66%±0.19% and 52.15%±0.37%, respectively, showing significant differences compared to other comparative examples (P<0.05).

[0076] (6) Improves lipid metabolism The lipid metabolism-improving effects of the extruded puffed rice cakes from Examples 1-2 and Comparative Examples 1-4 were characterized, and the percentage decrease or increase of each group's indicators compared to the model group was calculated. The results are as follows: Figure 6 As shown (average values ​​are taken for each group of experiments, and different lowercase letters indicate significant differences (P<0.05)). It can be seen that after intervention in Examples 1 and 2, triglycerides decreased by 29.62%±0.82% and 29.48%±1.57%, respectively; total cholesterol decreased by 26.97%±0.52% and 27.02%±1.42%, respectively; low-density lipoprotein cholesterol decreased by 43.87%±1.05% and 43.92%±1.57%, respectively; and high-density lipoprotein cholesterol increased by 75.89%±0.91% and 75.12%±1.02%, respectively. ALT activity decreased by 30.14%±1.05% and 30.85%±1.56%, respectively; and AST activity decreased by 27.01%±1.23% and 27.56%±0.95%, respectively. The overall improvement effect was the best.

[0077] In summary, the medium-GI extruded puffed rice cake prepared by this invention uses safe and non-toxic raw materials, is low in cost, and is easy to operate; the product has excellent crispness, melts in the mouth, has high puffing degree, and low bulk density; the predicted glycemic index is at a medium GI level, and the proportion of resistant starch is high; it has significant effects on stabilizing blood sugar and improving lipid metabolism, making it a healthy and leisure rice cake suitable for the elderly. Among them, Example 1 has the best overall quality.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A medium-GI extruded puffed rice cake, characterized in that, It includes the following ingredients by weight: 94-96 parts rice flour, 4-6 parts soy protein isolate, and 6-18 parts short-chain inulin.

2. The medium-GI extruded puffed rice cake according to claim 1, characterized in that, The mass ratio of the short-chain inulin to the mixture of rice flour and soy protein isolate is (6:94) to (15:85).

3. The medium-GI extruded puffed rice cake according to claim 1, characterized in that, The rice flour is obtained by crushing and sieving rice; the mesh size of the sieve is 100-140 mesh.

4. The medium-GI extruded puffed rice cake according to claim 1, characterized in that, The method for preparing soy protein isolate includes: defatting soy flour; dissolving defatted soy flour in water, adjusting the pH to alkaline, centrifuging, and collecting the supernatant; adjusting the pH to acidic, centrifuging, and collecting the precipitate; dispersing the precipitate in water, adjusting the pH to neutral, and drying to obtain soy protein isolate.

5. The method for preparing medium-GI extruded puffed rice cake according to any one of claims 1 to 4, characterized in that, include: Rice flour, soy protein isolate, and short-chain inulin are mixed to obtain a mixed powder; The mixed powder is added to water and then expanded by twin-screw extrusion. The extrudate is cut, shaped, and dried to obtain medium-GI extruded puffed rice cakes.

6. The preparation method according to claim 5, characterized in that, After adding water to the mixed powder, the moisture content of the material is adjusted to 12%~16%.

7. The preparation method according to claim 5, characterized in that, The conditions for the twin-screw extrusion puffing include: extrusion temperature of 110~150℃ and screw speed of 12~24Hz.

8. The use of the medium-GI extruded puffed rice cake according to any one of claims 1 to 4 in the preparation of products with hypoglycemic, lipid-lowering and / or liver-protective effects.

9. The application according to claim 8, characterized in that, The medium-GI extruded puffed rice cake exerts its hypoglycemic effect by reducing fasting blood glucose, serum insulin levels, area under the oral glucose tolerance test curve, and increasing liver glycogen levels.

10. The application according to claim 8, characterized in that, The medium-GI extruded puffed rice cake exerts its lipid-lowering effect by reducing serum triglycerides, total cholesterol, and low-density lipoprotein cholesterol, while increasing high-density lipoprotein cholesterol. And / or, the GI extruded puffed rice cakes mentioned above exert a liver-protective effect by reducing serum alanine aminotransferase (ALT) activity and aspartate aminotransferase (AST) activity.

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