Method for processing rice noodles by adopting ultrasonic and damp-heat combined treatment technology

Abstract

The invention relates to a method for processing rice noodles by adopting an ultrasonic and damp-heat combined treatment technology, which comprises the following steps: carrying out combined synergy on two technologies of ultrasonic treatment and damp-heat treatment to prepare treated rice flour; pouring the untreated rice flour, the treated rice flour, corn starch, flour and whey protein into a stirring machine according to a preset weight part ratio, and uniformly mixing; the mixed material is subjected to twin-screw extrusion forming, aging, secondary cooking, noodle scattering and drying, and the rice noodles are obtained. According to the invention, the rice flour is treated by adopting a synergistic physical modification process of first ultrasonic treatment and then damp-heat treatment, the hardness and chewiness of the rice noodles subjected to the synergistic treatment of ultrasonic treatment and damp-heat treatment have a significant rising trend, and meanwhile, the eGI value of the rice noodles is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of rice noodle processing, in particular to a method for processing rice noodles by adopting an ultrasonic and wet heat combined treatment technology. Background Art

[0002] Rice noodles, a rice noodle product made primarily from rice through a series of processes including soaking, crushing, extrusion, aging, cooking, sterilization, and packaging, have a long history of consumption in China. Rice noodles are rich in carbohydrates, with starch accounting for approximately 70-80% of the total, providing an effective source of energy for the human body. The starch content in rice noodles is also a key factor in determining their quality. Rice starch is primarily composed of amylose and amylopectin, and their ratio and molecular structure profoundly influence the final quality of the rice noodles. During processing, extrusion and cooking allow starch granules to absorb water, swell, and gelatinize. Amylose molecules dissolve and, together with some amylopectin, form a three-dimensional gel network that supports the rice noodles' stringy shape, giving them their characteristic elasticity and chewy texture. However, the aging process is crucial. The gelatinized starch molecules, particularly amylose, rearrange and recrystallize during cooling and storage. This process directly determines the rice noodles' hardness, toughness, smoothness, and resistance to boiling and rehydration during cooking. The degree and rate of starch retrogradation not only affect the smoothness and chewiness of rice noodles in the short term, ensuring they retain their texture even after prolonged cooking, but also profoundly impact the product's texture stability throughout its shelf life. Improper retrogradation can lead to excessive hardening, breakage, or a sticky texture. Therefore, precisely controlling the physical and chemical changes in starch at each stage of processing is crucial for optimizing rice noodle texture, enhancing its taste, and extending its shelf life.

[0003] Retrogradation of rice starch is a key factor affecting the texture and properties of rice noodles. Currently, the development of functional foods has become a hot topic. While the addition of exogenous substances such as protein can improve the nutritional value of rice products, these additions often lead to a deterioration in the texture of rice noodles, manifested by a decrease in key indicators such as hardness, elasticity, and chewiness. Summary of the Invention

[0004] In order to solve the technical problems existing in the above-mentioned technology, in view of this, it is necessary to provide a method for processing rice noodles using a combined ultrasonic and wet heat treatment technology.

[0005] A method for processing rice noodles using ultrasonic and wet heat combined treatment technology comprises the following steps:

[0006] Step S1: using ultrasonic treatment and moist heat treatment to prepare processed rice flour;

[0007] Step S2: pouring the untreated rice flour, the treated rice flour, corn starch, flour, and whey protein into a mixer according to a preset weight ratio and mixing them evenly;

[0008] Step S3: The mixed material is subjected to twin-screw extrusion molding, aging, secondary steaming, filamenting, and drying to obtain rice noodles.

[0009] Preferably, in step S1, the processed rice flour is obtained by the following method:

[0010] S11: First, rice flour is mixed with water to prepare a 20-30% rice flour suspension;

[0011] S12: ultrasonic treatment for a certain time at a preset ultrasonic power;

[0012] S13: centrifuging the ultrasonically treated suspension to obtain a precipitate, and adjusting the water content to 20-30%;

[0013] S14: wet heat treatment for a certain period of time under preset temperature conditions;

[0014] S15: Dry the material after the wet heat treatment at 45°C for 24 hours.

[0015] Preferably, in step S12, the power of the ultrasonic treatment is 300 W, and the treatment time is 20 min.

[0016] Preferably, the ultrasonic treatment is carried out in an ice water bath, and a 2-second run and 2-second stop method is used to prevent local overheating.

[0017] Preferably, in step S13, centrifugation is performed at 6000 rpm for 15 minutes to obtain a precipitate.

[0018] Preferably, in step S14, the precipitate is subjected to a wet heat treatment in an environment at 105° C. for 2 hours.

[0019] Preferably, the specific processing method of step S2 is as follows:

[0020] S21: Grind the untreated rice flour, the treated rice flour, the corn starch, and the flour, and pass through an 80-mesh sieve;

[0021] S22: mixing the untreated rice flour and the treated rice flour in a mass ratio of 7:3 to obtain mixed rice flour;

[0022] S23: Pour the mixed rice flour, corn starch and flour into a mixer in a mass ratio of 7:1.5:1.5 and mix well. Then, add the mixed rice flour, corn starch and whey protein in an amount of 5% by mass of the total dry weight of flour and mix well.

[0023] Preferably, the specific method of step S3 is as follows:

[0024] S31: screening and mixing the prepared raw materials, and extruding them using a twin-screw extruder to obtain preliminarily formed rice noodles;

[0025] S32: aging the initially formed rice noodles at 20° C. for 10-14 hours, and then performing a secondary aging at 100° C. for 5 minutes;

[0026] S33: The cooked rice noodles are sprayed to form thin strips, and then dried with gradient hot air and cut to obtain finished rice noodles.

[0027] Preferably, in step S31, the temperature of the twin-screw extruder is set to 60-120°C, the feed rate is 10.7 kg / h, and the moisture content is 50%.

[0028] Preferably, in step S33, the conditions for gradient hot air drying are: the temperature of the first stage is 50°C, and the time is 60 minutes; the temperature of the second stage is 47°C, and the time is 120 minutes; the temperature of the third stage is 45°C, and the time is 120 minutes; the temperature of the fourth stage is 30°C, and the time is 60 minutes.

[0029] Compared with the prior art, the present invention provides a method for processing rice noodles using a combined ultrasound and wet heat treatment technology. The treated rice flour replaces part of the untreated rice flour and is blended with corn starch and flour. 5% whey protein is added to the rice flour and the rice noodles are prepared by twin-screw extrusion. The results show that ultrasound and wet heat treatment are beneficial to improving the gel properties of the rice flour, and in particular, the ultrasound-wet heat combined treatment has the best effect. The cavitation effect of ultrasound can promote the breakage of starch chains and the dissolution of amylose, which promotes the rearrangement of starch during the retrogradation process, thereby facilitating the restoration of the quality deterioration of the rice noodles caused by exogenous proteins. At the same time, wet heat further promotes the rearrangement of starch molecular chains, resulting in stronger interaction between the molecular chains, thereby enhancing the texture of the rice noodle gel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 Schematic diagram of the preparation process of rice noodles of the present invention.

[0032] Figure 2 Graph showing the shear properties of rice noodles in comparative examples and embodiments.

[0033] Figure 3 Graph showing the cooking characteristics of rice noodles in comparative example and embodiment.

[0034] Figure 4 Graph showing the digestibility and estimated glycemic index of rice noodles in comparative examples and embodiments.

[0035] Figure 5 It is the microstructure diagram of rice noodles in comparative example and embodiment. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Comparative Example 1

[0038] Rice flour is not processed in any way. It is compounded with corn starch and flour and then extruded into rice noodles through twin screw extrusion. Figure 1 , the preparation method of rice noodles is as follows:

[0039] (1) The raw materials are passed through an 80-mesh sieve to ensure the quality of the raw materials, and then the ingredients are accurately weighed according to the pre-set weight ratio;

[0040] The powder mixture is poured into a mixer to mix the materials thoroughly and evenly, and then transferred to a twin-screw extruder to extrude the noodles at a high temperature of up to 140°C to obtain preliminarily formed rice noodles.

[0041] (2) Transfer the initially formed rice noodles to a constant temperature and humidity incubator and allow the rice noodles to age at 20°C for 12-14 hours;

[0042] After the aging of the rice noodles is completed, the rice noodles are further aged at 100° C. for 5 minutes to obtain aged rice noodles.

[0043] (3) Quickly put the cooked rice noodles into cold water and spread them out to loosen them;

[0044] The loosened rice noodles are put into an oven and gradually removed with gradient hot air drying technology to achieve a suitable degree of dryness; the dried rice noodles are cut and bagged to obtain the rice noodles;

[0045] The conditions of gradient hot air drying are as follows: the temperature of the first stage is 50°C and the time is 60 minutes; the temperature of the second stage is 47°C and the time is 120 minutes; the temperature of the third stage is 45°C and the time is 120 minutes; the temperature of the fourth stage is 30°C and the time is 60 minutes, and the total time is 6 hours.

[0046] Comparative Example 2

[0047] Compared to Comparative Example 1, whey protein was added to this comparative example. Rice flour, untreated, was compounded with corn starch, flour, and whey protein, and then rice noodles were prepared by twin-screw extrusion. The preparation method of the rice noodles in this comparative example was similar to that of Comparative Example 1.

[0048] Comparative Example 3

[0049] Compared with Comparative Example 2, this comparative example is configured with a 20% rice flour solution. The ultrasonic treatment conditions are a power of 300W, a time of 20min, and an ice-water bath. The solution is run for 2s and stopped for 2s to prevent local overheating. After ultrasonic treatment, the solution is centrifuged at 6000rpm for 15min, the precipitate is taken, and the treated rice flour is dried at 45°C for 24h to reduce the moisture content to less than 5%. Untreated rice flour and ultrasonically treated rice flour are mixed in a mass ratio of 7:3 to obtain mixed rice flour; the mixed rice flour is poured into a mixer with corn starch and flour in a mass ratio of 7:1.5:1.5 to mix, and then the mixed rice flour, corn starch, and whey protein (5% of the total mass of the flour dry basis) are added and mixed, and then rice noodles are prepared by twin-screw extrusion.

[0050] The preparation method of the rice noodles described in this comparative example refers to the preparation method of comparative example 1.

[0051] Comparative Example 4

[0052] Compared with Comparative Example 2, in this comparative example, the moisture content of the rice flour was adjusted to 20%, and the rice flour was placed in a 105°C environment and subjected to a heat treatment for 2 hours. The treated rice flour was then dried at 45°C for 24 hours to reduce the moisture content to less than 5%. Untreated rice flour and heat-treated rice flour were mixed in a mass ratio of 7:3 to obtain mixed rice flour. The mixed rice flour was then mixed with corn starch and flour in a mass ratio of 7:1.5:1.5 in a mixer. The mixed rice flour, corn starch, and whey protein (5% by weight of the total weight of the flour on a dry basis) were then added and mixed. Rice noodles were then prepared by twin-screw extrusion.

[0053] The preparation method of the rice noodles described in this comparative example refers to the preparation method of comparative example 1.

[0054] Comparative Example 5

[0055] Compared with Comparative Example 2, this comparative example adjusts the moisture content of rice flour to 20%, places it in a 105°C environment, and performs a heat treatment for 2 hours. The heat-treated rice flour is configured with a 20% concentration suspension. The ultrasonic condition is fixed at a power of 300W for 20 minutes and is carried out in an ice-water bath. The method of running for 2 seconds and stopping for 2 seconds is used to prevent local overheating. After ultrasonic treatment, centrifugation is carried out at a speed of 6000rpm for 15 minutes, and the precipitate is taken and dried at 45°C for 24 hours to reduce the moisture content to less than 5%. Untreated rice flour and heat-ultrasound-treated rice flour are mixed in a mass ratio of 7:3 to obtain mixed rice flour; the mixed rice flour is poured into a mixer with corn starch and flour in a mass ratio of 7:1.5:1.5, and then mixed with mixed rice flour, corn starch, and whey protein at 5% of the total mass of the flour dry basis is added thereto and mixed. Rice noodles are prepared by twin-screw extrusion.

[0056] The preparation method of the rice noodles described in this comparative example refers to the preparation method of comparative example 1.

[0057] Example 1

[0058] A method for processing rice noodles using ultrasound and wet heat combined treatment technology adopts the following method:

[0059] Rice flour is mixed with water to form a 20-30% rice flour suspension. Ultrasonic treatment is performed at 300W for 20 minutes in an ice-water bath, with a 2-second on / off cycle to prevent local overheating. After ultrasonic treatment, the suspension is centrifuged at 6000rpm for 15 minutes, the precipitate is collected, and the moisture content is adjusted to 20%. The suspension is then placed in a 105°C environment for a heat treatment for 2 hours. The treated rice flour is then dried at 45°C for 24 hours to reduce the moisture content to less than 5%. Untreated rice flour and the ultrasonic-heat treated rice flour are mixed in a mass ratio of 7:3 to obtain mixed rice flour. The mixed rice flour is then mixed with corn starch and flour in a mass ratio of 7:1.5:1.5 in a mixer. The mixed rice flour, corn starch, and whey protein (5% of the total weight of the flour on a dry basis) are then added and mixed. Rice noodles are then prepared by twin-screw extrusion.

[0060] The preparation method of the rice noodles in this embodiment refers to the preparation method of Comparative Example 1.

[0061] Example 2

[0062] Rice flour is mixed with water to form a 20-30% rice flour suspension. Ultrasonication is performed in an ice-water bath at a fixed power of 300W for 20 minutes, with a 2-second on / off cycle to prevent local overheating. After ultrasonic treatment, the suspension is centrifuged at 6000 rpm for 15 minutes. The precipitate is collected and the moisture content is adjusted to 30%. The suspension is then placed in a 105°C environment for a wet heat treatment for 2 hours. The treated rice flour is then dried at 45°C for 24 hours to reduce the moisture content to less than 5%. Untreated rice flour and the ultrasonic-wet heat treated rice flour are mixed in a mass ratio of 7:3 to obtain mixed rice flour. The mixed rice flour is then mixed with corn starch and flour in a mass ratio of 7:1.5:1.5 in a mixer. The mixed rice flour, corn starch, and whey protein (5% of the total weight of the flour on a dry basis) are then added and mixed. Rice noodles are then prepared by twin-screw extrusion.

[0063] The preparation method of the rice noodles in this embodiment refers to the preparation method of Comparative Example 1.

[0064] Example 3

[0065] Rice flour is mixed with water to form a 20-30% rice flour suspension. Ultrasonication is performed in an ice-water bath at a fixed power of 300W for 20 minutes, with a 2-second on / off cycle to prevent local overheating. After ultrasonic treatment, the suspension is centrifuged at 6000 rpm for 15 minutes, the precipitate is collected, and the moisture content is adjusted to 20%. The suspension is then placed in a 105°C environment for a wet heat treatment for 1 hour. The treated rice flour is then dried at 45°C for 24 hours to reduce the moisture content to less than 5%. Untreated rice flour and the ultrasonic-wet heat treated rice flour are mixed in a mass ratio of 7:3 to obtain mixed rice flour. The mixed rice flour is then mixed with corn starch and flour in a mass ratio of 7:1.5:1.5 in a mixer. The mixed rice flour, corn starch, and whey protein (5% of the total weight of the flour on a dry basis) are then added and mixed. Rice noodles are then prepared by twin-screw extrusion.

[0066] The preparation method of the rice noodles in this embodiment refers to the preparation method of Comparative Example 1.

[0067] 1. To explore the texture characteristics of the rice noodles provided by the present invention, the following tests were performed on the rice noodles of the comparative example and the embodiment:

[0068] 1. TPA test:

[0069] Rice noodles cooked to the optimal cooking time were immediately placed on the texture analyzer sample plate for testing. A P36 / R probe was used, with a pre-test speed of 5 mm / s, a test speed of 1 mm / s, and a post-test speed of 5 mm / s. A compression ratio of 50% was used, a trigger force of 5 g, and a 5-second interval between compressions. Each sample was tested three times. The textural properties of the rice noodles in the comparative examples and examples are shown in Table 1. Values ​​with different letters in the same column indicate significant differences (p < 0.05).

[0070] 2. Shear test: The rice noodles with the optimal cooking time were placed in a texture analyzer with an HDP / LKBF probe for testing. The shear characteristic parameters were set to 2 mm / s before the test, 0.10 mm / s after the test, 2 mm / s after the test, a trigger force of 15 g, and a deformation measurement of 80%. The shear characteristic results of the rice noodles in the comparative example and the embodiment are shown in FIG. Figure 2 , Different letters in the same column indicate significant differences between values ​​(p < 0.05).

[0071] Table 1 Texture characteristics of rice noodles in comparative examples and examples

[0072]

[0073]

[0074] From Table 1 we can see that:

[0075] The rice noodles without whey protein have the highest hardness and chewiness, which are 1113.75g and 860.52g respectively. After adding whey protein, the hardness of the rice noodles significantly decreases, only 686.32g, which means that the addition of exogenous substances makes the rice noodles quality deteriorate, which may be due to the addition of exogenous substances suppressing the retrogradation of rice starch to a certain extent, thereby showing a reduction in hardness. After the rice flour is treated with ultrasound or moist heat, the hardness and chewiness of the prepared rice noodles show an upward trend. When ultrasound and moist heat are combined, the gel texture characteristics of the rice noodles are restored more obviously, and the hardness of the rice noodles of Example 1 is restored to 1057.66g, which is relatively close to the hardness of the original rice noodles.

[0076] On the one hand, the cavitation effect generated by ultrasound disrupts the surface structure of starch, the main component of rice flour, while promoting the exudation of more amylose, thereby providing more opportunities for amylose rearrangement during aging. Furthermore, ultrasound treatment may cause the scission of short branched side chains in amylopectin, resulting in shorter amylose and branched fragments, which favor the formation of a denser gel structure. On the other hand, wet-heat treatment, at low moisture content and high temperature, promotes a certain degree of rearrangement of starch molecular chains. The mobility of the amorphous regions is enhanced, and some double helical structures may unwind or rearrange. Existing intra- and intermolecular hydrogen bonds are partially broken, and new, more stable hydrogen bond networks are formed at new locations. Ultrasound and wet-heat treatment also have a certain impact on the proteins already present in rice flour. The denatured proteins may be more likely to interact with starch molecules or form gel networks themselves, contributing to the enhanced gel strength of rice noodles.

[0077] The shear properties results were similar to those of TPA. Ultrasound or moist heat treatment and ultrasound-moist heat combined treatment enhanced the shear force of rice noodles, indicating that ultrasound and moist heat both had a certain promoting effect on the recovery of rice noodle gel strength.

[0078] Second, in order to explore the cooking quality of the rice noodles provided by the present invention, the following tests were conducted on the rice noodles of the embodiment and the comparative example:

[0079] 1. Determination of broken strip rate:

[0080] Use a beaker to measure approximately 1000 mL of boiling water and heat on a hot plate, keeping the water at a slight boil. Randomly select 20 whole rice noodles and place them in the boiling water. Start a timer. When the optimal steaming time is reached, gently pick out the noodles with chopsticks and count the number of broken noodles.

[0081] The broken strip rate is calculated according to the following formula:

[0082]

[0083] Where N is the number of broken rice noodles;

[0084] 2. Determination of cooking loss:

[0085] Take 5 rice noodles in 250 mL of water, cook until the optimal cooking time, remove them, drain for 3 minutes, and weigh them. Dry the remaining soup to a constant weight and calculate the cooking loss rate according to the following formula:

[0086] 3. Determination of rehydration rate:

[0087] The rice noodles cooked to the optimal cooking time were drained for 3 minutes and then weighed. The rehydration rate was the ratio of the mass of the cooked rice noodles to the original mass.

[0088] The cooking quality test results of rice noodles in the comparative examples and embodiments are shown in Figure 3 , Different letters in the same column indicate significant differences between values ​​(p < 0.05).

[0089] Depend on Figure 3 It can be seen that:

[0090] Comparative Example 2, which contains rice noodles with added whey protein, shows a significant increase in both cooking loss and breakage, reaching 17.18% and 45.18%, respectively, compared to Comparative Example 1. This is because the addition of exogenous protein weakens the gel texture of the rice noodles, causing more starch to ooze out during cooking and resulting in looser binding of starch molecules, increasing the breakage rate. Ultrasound and moist heat treatment significantly improve this phenomenon, as they promote the formation and molecular rearrangement of short starch chains, enhancing intermolecular hydrogen bonding, resulting in a denser gel structure and reducing the cooking loss and breakage rate of the rice noodles.

[0091] 3. In order to explore the digestibility and GI value of the rice noodles provided by the present invention, the following tests were performed on the rice noodles of the comparative example and the embodiment:

[0092] 1. Digestion characteristics: Refer to the Englyst method with slight modifications. Take 0.5g of cooked rice noodles and place them in a 250ml conical flask and add 5 glass beads, 15mL of 0.5mol / L pH=5.2 acetic acid buffer solution and 10mL of a mixed enzyme solution containing saccharifying enzyme and α-amylase. Place the conical flask in a water bath at 37℃ and shake at 170rpm to perform the enzymatic hydrolysis reaction and start the timer. Accurately draw 1mL of the enzymatic hydrolyzate at 0, 20min, and 120min, place it in a centrifuge tube, add 4mL of anhydrous ethanol to inactivate it, centrifuge at 4000rpm for 10min, use the glucose oxidase method, and use a microplate reader to measure the absorbance of the supernatant at 505nm. Calculate the content of rapidly digestible starch, slowly digestible starch, and resistant starch according to the following formula.

[0093]

[0094] Among them: G 20 : Glucose content in digestive fluid at 20 min (mg);

[0095] F G : free glucose content in digestive juice (mg);

[0096] G 120 : Glucose content in digestive fluid at 120 min (mg);

[0097] TS: total starch content (mg).

[0098] 2. Estimated GI value:

[0099] ① Sample preparation: soak rice noodle samples in 80℃ water for 20 minutes, then boil them in boiling water until the optimal cooking time is reached and remove them for later use;

[0100] ② Oral chewing simulation: Follow the method of Gawlik-Dziki et al. with appropriate adjustments. Place 1 g of treated rice noodle sample in a conical flask, add 10 mL of pH 6.5 phosphate buffer solution containing salivary amylase, and gently tap with a mortar for 15 seconds. Add 5 glass beads and shake in a 37°C water bath for 10 minutes.

[0101] ③ Gastric digestion simulation: adjust the pH to 1.2 with 5 M HCL, then add 10 mL of 0.03 M NaCl solution (pH = 1.2) containing pepsin, and shake in a 37°C water bath for 30 min.

[0102] ④ Intestinal digestion simulation: Use 1 M NaOH to adjust the pH to 7.0, add 10 mL of intestinal fluid (add 0.05 g of pancreatic enzyme, 0.3 g of porcine bile salt, and 0.3 g of saccharifying enzyme to 100 mL of phosphate buffer solution), 5 mL of 120 mM NaCl solution, and 5 mL of 120 mM KCl. Shake in a 37°C water bath for 180 min. At 10, 20, 30, 45, 60, 90, 120, 150, and 180 min, accurately draw 1 mL of sample into a centrifuge tube containing 4 mL of anhydrous ethanol, and centrifuge at 5000 rpm for 10 min.

[0103] ⑤ Glucose determination: Take the supernatant after centrifugation and use a glucose determination kit to measure the absorbance at 505nm to calculate the glucose content at different time periods.

[0104] ⑥Calculation method: Calculate the hydrolysis rate of starch based on the amount of glucose released, draw a curve of the change of starch hydrolysis rate over time, and calculate the digestion curve of all rice noodle samples according to the equation First-order kinetic fitting was performed.

[0105] The area under the digestion curve (AUC) was calculated by the following formula:

[0106]

[0107] Where Ct: starch hydrolysis rate at time t; C∞: final starch hydrolysis rate; t f : total digestion reaction time (180 min); t0: digestion start time (0 min); k: kinetic constant;

[0108] The hydrolysis index (HI) is calculated by the following formula:

[0109]

[0110] Using white bread as a reference, calculate the GI of rice noodles using the following formula:

[0111] GI=0.862HI+8.819

[0112] The in vitro digestibility and glycemic index estimation results of rice noodles in the comparative examples and examples are shown in Figure 4 , Different letters in the same column indicate significant differences between values ​​(p < 0.05).

[0113] Depend on Figure 4 It can be seen that:

[0114] RDS is a fast-digesting starch that can be digested and absorbed in the small intestine within 20 minutes; SDS is a slow-digesting starch that can be digested and absorbed in the small intestine within 20-120 minutes; RS is a resistant starch that cannot be digested and absorbed in the small intestine.

[0115] Comparative Example 1, rice noodles without whey protein, had an RDS of 78.37% and an eGI of 78.88. After adding whey protein, the RDS significantly decreased to 72.36%, while both SDS and RS increased, indicating that the addition of whey protein can improve the in vitro digestibility of rice noodles. Ultrasound or wet heat treatment of rice flour can reduce the eGI of the prepared rice noodles. This is because ultrasound can increase the linear structure of starch, enhance the interaction between starch chains, and make the gel network structure more dense, thereby hindering the decomposition of starch by amylase, reducing the RDS of the rice noodles and increasing the SDS and RS contents. Wet heat treatment can rearrange the starch chains, forming a more ordered structure, which has a positive effect on resisting the entry of amylase.

[0116] Fourth, in order to explore the microstructure of the rice noodles provided by the present invention, the following tests were performed on the rice noodles of the comparative example and the embodiment:

[0117] Rice noodles cooked for the optimal cooking time were drained of surface moisture, pre-frozen in a -80°C freezer for 24 hours, and then freeze-dried in a freeze dryer for 72 hours. The network structure of the rice noodles was observed using a scanning electron microscope. The test voltage was 8 kV and the current was 8 μA.

[0118] The microstructure of rice noodles in the comparative examples and embodiments is shown in FIG. Figure 5 .

[0119] Depend on Figure 5 It can be seen that:

[0120] The cross-sectional microstructure of all rice noodle samples was porous. The addition of whey protein reduced the porosity, reduced the cross-linking, and weakened the gel strength. Ultrasound, wet heat, and combined ultrasound-wet heat treatments improved the cross-sectional microstructure, increasing the number of pores and significantly strengthening their spacing, which contributed to improved rice noodle quality.

[0121] In summary, the present invention effectively improves the problem of rice noodle quality deterioration caused by the addition of exogenous protein by combining ultrasound and moist heat to treat rice flour and replacing a certain proportion of original rice flour, thereby effectively improving the hardness and chewiness of rice noodles and reducing the estimated glycemic index of rice noodles to a certain extent.

[0122] The above disclosure is only a preferred embodiment of the present invention, and it is certainly not intended to limit the scope of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for processing rice noodles using a combined ultrasonic and wet heat treatment technology, characterized in that: The following steps are included: Step S1: using ultrasonic treatment and moist heat treatment to prepare processed rice flour; Step S2: pouring the untreated rice flour, the treated rice flour, corn starch, flour, and whey protein into a mixer according to a preset weight ratio and mixing them evenly; Step S3: The mixed material is subjected to twin-screw extrusion molding, aging, secondary steaming, filamenting, and drying to obtain rice noodles.

2. The method for processing rice noodles using ultrasound and moist heat combined treatment technology according to claim 1, wherein: In step S1, the processed rice flour is obtained by: S11: First, rice flour is mixed with water to prepare a 20-30% rice flour suspension; S12: ultrasonic treatment for a certain time at a preset ultrasonic power; S13: centrifuging the ultrasonically treated suspension to obtain a precipitate, and adjusting the water content to 20-30%; S14: wet heat treatment for a certain period of time under preset temperature conditions; S15: Dry the material after the wet heat treatment at 45°C for 24 hours.

3. The method for processing rice noodles using ultrasound and moist heat combined treatment technology according to claim 2, wherein: In step S12, the power of ultrasonic treatment is 300 W, and the treatment time is 20 min.

4. The method for processing rice noodles using ultrasound and wet heat combined treatment technology according to claim 3, wherein: During ultrasonic treatment, it must be carried out in an ice water bath, and a 2-second run and 2-second stop method should be used to prevent local overheating.

5. The method for processing rice noodles using ultrasound and wet heat combined treatment technology according to claim 3, wherein: In step S13, the mixture was centrifuged at 6000 rpm for 15 min to obtain a precipitate.

6. The method for processing rice noodles using ultrasound and wet heat combined treatment technology according to claim 5, wherein: In step S14, the precipitate is subjected to a wet heat treatment in an environment at 105° C. for 2 hours.

7. The method for processing rice noodles using ultrasound and wet heat combined treatment technology according to claim 1, wherein: The specific processing method of step S2 is as follows: S21: Grind the untreated rice flour, the treated rice flour, the corn starch, and the flour, and pass through an 80-mesh sieve; S22: mixing the untreated rice flour and the treated rice flour in a mass ratio of 7:3 to obtain mixed rice flour; S23: Pour the mixed rice flour, corn starch and flour into a mixer in a mass ratio of 7:1.5:1.5 and mix well. Then, add the mixed rice flour, corn starch and whey protein in an amount of 5% by mass of the total dry weight of flour and mix well.

8. The method for processing rice noodles using ultrasound and wet heat combined treatment technology according to claim 1, wherein: The specific method of step S3 is as follows: S31: screening and mixing the prepared raw materials, and extruding them using a twin-screw extruder to obtain preliminarily formed rice noodles; S32: aging the initially formed rice noodles at 20° C. for 10-14 hours, and then performing a secondary aging at 100° C. for 5 minutes; S33: The cooked rice noodles are sprayed to form thin strips, and then dried with gradient hot air and cut to obtain finished rice noodles.

9. The method for processing rice noodles using ultrasound and wet heat combined treatment technology according to claim 8, wherein: In step S31, the temperature of the twin-screw extruder is set to 60-120°C, the feed rate is 10.7 kg / h, and the moisture content is 50%.

10. The method for processing rice noodles using the ultrasonic and wet heat combined treatment technology according to claim 8, characterized in that: In step S33, the conditions for gradient hot air drying are: the temperature of the first stage is 50°C, and the time is 60 minutes; the temperature of the second stage is 47°C, and the time is 120 minutes; the temperature of the third stage is 45°C, and the time is 120 minutes; the temperature of the fourth stage is 30°C, and the time is 60 minutes.

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