Preparation method of brewing type instant rice noodles with high softness and elasticity and instant rice noodles prepared by preparation method

Abstract

The invention discloses brewing type instant rice noodles with high softness and elasticity and a preparation method thereof. Rice is used as a raw material, pullulanase and protease are adopted to conduct enzymolysis on the rice in sequence, the looseness degree of a gel network is improved through degradation of starch and protein molecules, and the flexibility of the rice noodles is improved; the interaction of catalytic product debranched starch-peptide chains is utilized to improve the strength of intermolecular acting force, so that the rice noodles have higher elongation. Therefore, compared with other methods for shortening the rehydration time, the prepared rice noodles have the advantages of being edible after being brewed, high in flexibility and elasticity and low in breaking rate, the production process is simple and convenient, the cost is low, complex equipment is not needed, no chemical additive is used, and the requirements of cleaning labels are met. The invention further discloses the high-softness elastic brewing type instant rice noodles.

Description

Technical Field

[0001] The present invention relates to the technical field of deep processing of rice noodles, specifically to a preparation method of high-soft-elasticity instant rice noodles by soaking, and the present invention also relates to high-soft-elasticity instant rice noodles prepared by the preparation method of high-soft-elasticity instant rice noodles by soaking. Background Art

[0002] Rice noodles are a common staple food in China and Southeast Asian regions, and are mainly consumed fresh traditionally. In recent years, against the background of the rapid economic development in China and the accelerating pace of people's lives, the demand of consumers for prepackaged rice noodles has increased sharply, which has promoted the rapid development of the rice noodle industry. Currently, the prepackaged rice noodles sold on the market are mainly dry rice noodles, which have the characteristics of requiring open-fire cooking, long cooking time, and poor eating convenience. To improve the convenience of dry rice noodles, most of the commercially available products reduce the diameter of the rice noodles to shorten the rehydration time. However, while the diameter of the rice noodles decreases, their texture quality also drops sharply. Therefore, the currently commercially available dry rice noodles cannot combine convenience and chewiness, and cannot meet the requirements of consumers for the convenience and taste of prefabricated staple foods at the same time, which restricts the further development of the rice noodle industry.

[0003] The currently publicly disclosed Chinese patent CN202410574239.3 uses pectin to improve the toughness and rehydration convenience of rice noodles; CN202310777320.7 uses protease to shorten the cooking time of rice noodles; CN202210640367.4 combines secondary extrusion cooking, protein and citrus powder to shorten the cooking time; CN202310157494.3 shortens the cooking time and improves the chewiness and extensibility of rice noodles by adding sugar alcohols. However, the dry rice noodles prepared by these patented technologies still need to be cooked, which limits the eating scenarios of prepackaged rice noodles. The patent with the publication number CN115039851A uses freeze-drying technology to prepare soakable rice noodles. This technology requires using freeze-drying equipment to freeze-dry for 9 - 12 hours, and this freeze-drying equipment is expensive and currently cannot be applied to industrial rice noodle production at all. In addition, it should be noted that the existing related patents mainly focus on improving the toughness of rice noodles. However, rice noodles with strong rigidity and high toughness do not have good palatability. What consumers are most concerned about the quality of rice noodles is the chewiness, and this chewy texture requires that the rice noodles have high soft elasticity (i.e., high flexibility and high elongation rate).

[0004] Therefore, it is necessary to develop a preparation method of high-soft-elasticity instant rice noodles with low cost and simple process. Summary of the Invention

[0005] The first object of the present invention is to provide a preparation method of highly flexible instant rice noodles by brewing. Pullulanase and protease are combined to prepare instant rice noodles. The prepared instant rice noodles only need to be soaked in boiling water without cooking. After rehydration, the rice noodles have a thick diameter, high flexibility and chewiness. The production process has the advantages of high efficiency, low cost, simple operation without pollution, and clean label.

[0006] The second object of the present invention is to provide a highly flexible instant rice noodles by brewing, which has a short rehydration time and does not need to be cooked. It can be eaten by soaking in water at about 100 °C for 250-300 s. The diameter of the highly flexible instant rice noodles after rehydration is 2.2-3.5 mm, the tensile strength is 15-20 g, the elongation at break is 120-250%, and the chewiness is strong.

[0007] In order to achieve the first object of the present invention, the technical solution of the present invention is: a preparation method of highly flexible instant rice noodles by brewing, including the following steps:

[0008] Step (1): Using rice as the raw material, pullulanase is used to enzymatically hydrolyze the rice.

[0009] Step (2): The rice after enzymatic hydrolysis in step (1) is further enzymatically hydrolyzed with protease to produce short peptides.

[0010] Step (3): The rice after enzymatic hydrolysis in step (2) is made into slurry, cooked, aged, and packaged to obtain highly flexible instant rice noodles by brewing.

[0011] In the above technical solution, the specific method for pullulanase to enzymatically hydrolyze rice in step (1) is: soaking the rice in pullulanase enzyme solution, pouring out the enzyme solution after soaking and enzymatically hydrolyzing for a period of time, and washing with clear water to remove the residual enzyme solution.

[0012] In the above technical solution, the pullulanase is derived from Bacillus licheniformis, and the addition amount of pullulanase relative to rice is 70-150 U / g.

[0013] In the above technical solution, the enzymatic hydrolysis time of pullulanase on rice in step (1) is 3-6 h.

[0014] In the above technical solution, the content of amylose in the hydrolysis product of pullulanase in step (1) is 25%-30%.

[0015] In the above technical solution, the specific method for enzymatic hydrolysis with protease in step (2) is: soaking the rice soaked and washed after enzymatic hydrolysis with pullulanase in protease enzyme solution, pouring out the enzyme solution after soaking and enzymatically hydrolyzing for a period of time, and washing with clear water to remove the residual enzyme solution.

[0016] In the above technical solution, the protease is a weakly alkaline protease; the addition amount of the protease relative to the rice raw material is 150 - 250 U / g;

[0017] The enzymolysis time of the protease on rice is 10 - 30 h.

[0018] In the above technical solution, the protease is one or more of bromelain, trypsin, trypsin, papain, and fibrinolytic protease.

[0019] In the above technical solution, the molecular weight of the short peptides produced by enzymolysis of the hydrolyzed protein in step (2) is 3 - 10 KDa.

[0020] In the above technical solution, the addition amount of pullulanase relative to rice in step (1) is 100 U / g, and the enzymolysis time of pullulanase on rice is 5 h;

[0021] In step (2), the addition amount of the protease relative to the rice raw material is 200 U / g; the enzymolysis time of the protease relative to rice is 24 h.

[0022] In order to achieve the second object of the present invention, the technical solution of the present invention is: a high - soft - elastic instant rice noodle for brewing, characterized in that: it is prepared by the preparation method of the high - soft - elastic instant rice noodle for brewing. The high - soft - elastic instant rice noodle for brewing prepared by the preparation method of the high - soft - elastic instant rice noodle for brewing of the present invention does not need to be cooked, and only needs to be soaked in water at about 100 °C for 250 - 300 s to be edible, and has the characteristics of high flexibility, low rigidity, and strong chewy feeling after rehydration. The diameter of the high - soft - elastic instant rice noodle for brewing after rehydration is 2.2 - 3.5 mm, the tensile strength is 15 - 20 g, and the elongation rate is 120 - 250%.

[0023] The beneficial effects of the present invention:

[0024] (1) The dry rice noodles only need to be soaked without cooking:

[0025] The present invention improves the free volume of starch molecules in the following three aspects, enabling them to have sufficient space to interact with the water entering during the rehydration process, thus significantly enhancing the rehydration ability of dry rice noodles: First, pullulanase is used to hydrolyze the α,1-6 glycosidic bonds of rice starch, degrade the starch molecular size, reduce the ability of starch retrogradation and rearrangement into a dense structure, and thereby improve the looseness of the rice noodle gel; Second, protease is used to hydrolyze proteins into peptide chains and amino acids with molecular weights much lower than those of proteins, avoiding the negative impact on starch gelation caused by the ability of proteins to interact with starch; Third, the interaction of enzymatic hydrolysis products: starch and peptide chains can interact through hydrophobic interaction, electrostatic interaction, and hydrogen bond; among them, hydrophobic interaction and electrostatic interaction require a relatively long distance between molecules to maintain effective interaction, so they have a much larger free volume than hydrogen bond interaction; and the hydrogen bond between polypeptide and starch molecule is C=O…H-O or -NH…H-O hydrogen bond, and its bond length is longer than that of glycosidic bond (-O-); Therefore, the starch-peptide chain interaction can significantly increase the free volume of starch molecules, enabling them to have sufficient space to interact with the water entering during the rehydration process, thus significantly improving the rehydration efficiency. Dry rice noodles can be rehydrated by simply soaking instead of boiling, improving the eating convenience of dry rice noodles and increasing the eating scenarios of pre-packaged rice noodles;

[0026] (2) The rehydrated rice noodles have high flexibility and elasticity:

[0027] The present invention improves the flexibility and elasticity highly related to the chewiness of rice noodles in the following two aspects: One is to reduce the rigidity of the rice noodle gel and improve the flexibility of the gel through the hydrolysis of starch and protein by pullulanase and protease respectively; The other is to improve the strength of the intermolecular force in the rice noodle gel network through the strong interaction between debranched starch and peptide chains by enzymatic hydrolysis. This force enables the rice noodles to remain unbroken under continuous tensile force, thereby giving the rice noodles a high elongation rate. The rehydrated rice noodles thus obtain high flexibility and elasticity, that is, the chewiness is significantly enhanced; It can be seen that the present invention can meet the dual needs of consumers for the eating convenience and chewy taste of instant rice noodles;

[0028] (3) The rehydrated rice noodles have a thick diameter:

[0029] After the present invention combines pullulanase with protease to enzymatically hydrolyze rice, the rice flour extruded by a mold with an aperture of about 1.8 mm can, after processes such as aging and drying, be made into a bubble-type rice flour that can restore its diameter to 2.2 - 3.5 mm during rehydration. Moreover, the rehydrated rice flour has high soft elasticity and a strong chewy texture (the tensile strength of the rehydrated rice flour is 15 - 20 g, and the elongation rate is 120 - 250%). The rehydration time is short (it can be eaten after soaking in water at about 100 °C for 250 - 300 s), the breakage rate is low, it is not easy to make the soup turbid, and the edible taste of the pre-packaged rice flour is improved. It solves the problem that currently commercially available instant rice flour uses a mold with an aperture less than 1.2 mm to prepare very fine rice flour to shorten the rehydration time of dried rice flour. However, the rice flour with a relatively thin diameter lacks a chewy texture, and it is easy to break and merge during rehydration, and the soup becomes very turbid, significantly reducing the edible taste of the pre-packaged rice flour.

[0030] (4) Simple process, low cost, and zero addition:

[0031] The present invention does not require additional purchase of equipment, is easy to operate, and the enzyme solution soaking utilizes the production links that already exist in the industrialized production of rice flour, without adding additional cumbersome processes, which is conducive to large-scale production in factories. Specifically, the cost of the present invention is reduced by about 52% compared with the traditional process (4 - 5 stages of aging + 4 stages of drying): The present invention uses enzyme treatment without vacuum freezing equipment, saving equipment investment (the cost of vacuum freezing equipment is greater than or equal to 800,000 yuan per unit), saving drying time cost and energy consumption (the duration of the aging and drying processes with high energy consumption is shortened from 18 - 24 h to 8 - 10 h (the energy consumption reduction is about 50%)), and eliminating the process and cost of anti-retrogradation additives (such as monoglyceride, with a cost of about 200 yuan per ton). The enzyme solution in the present invention can be recycled 3 - 5 times, and the processing cost of the dried rice flour is only about 38 yuan per ton, which has a significant advantage in saving processing costs compared with hot air drying (the processing cost of dried rice flour is about 152 yuan per ton) and vacuum freezing (the processing cost of dried rice flour is about 890 yuan per ton). At the same time, after the rice flour in the present invention is soaked in the enzyme preparation, the enzyme solution is discarded and the rice is washed, so the prepared instant rice flour product has no residue, meeting the current consumers' demand for zero-additive foods. It solves the problems of the prior art mainly using the method of optimizing the drying process to shorten the rehydration time of dried rice flour, but the optimization of the drying process often depends on expensive equipment (such as vacuum freeze-drying equipment, etc.), or the hot air drying with a complex and cumbersome process, complex operation, long production time and causing process pollution, or adding certain additives to improve the rehydration time of dried rice flour, resulting in increased costs and additive residues. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the preparation principle of the high-soft-elasticity bubble-type instant rice flour of the present invention. Detailed Embodiments

[0033] The implementation of the present invention will be described in detail below in conjunction with the accompanying drawings. However, they do not constitute a limitation to the present invention and are only for illustration purposes. At the same time, the advantages of the present invention are made clearer and easier to understand through the description.

[0034] The present invention uses pullulanase to debranch starch to produce a specific content of amylose (the content of amylose is 25-30%); uses protease to hydrolyze rice protein into peptide chains with a specific degree of polymerization (3-10 kDa); through the dual hydrolysis of pullulanase and protease, the retrogradation behavior of starch is significantly inhibited, and then the looseness of the rice noodle gel network is significantly improved, so that the rice noodles have the ability of rapid rehydration and higher flexibility. At the same time, through the interaction of the hydrolysis products (amylose and peptide chains) of the two enzymes, on the one hand, the retrogradation between starch molecules is interfered to improve the flexibility of starch molecular chains, and then the elongation ability during the stretching of rice noodles is improved; on the other hand, the interaction between linear chains and peptide chains with a specific degree of polymerization can significantly promote the intermolecular force strength in the rice noodle gel network, and this force enables the rice noodles to remain unbroken under continuous stretching force, thus endowing the rice noodles with a higher elongation rate, thereby improving the chewiness of the rice noodles. Therefore, through the hydrolysis of pullulanase and protease under specific conditions in the present invention, the ability of starch molecules to retrograde and rearrange into a dense gel is significantly reduced, and the looseness of the rice noodles is significantly improved, enabling water to quickly enter the center of the rice noodles; while the flexibility and plasticity of starch molecules are significantly improved, enabling the rice noodles to recover to a larger elongation rate under less water and shorter time conditions, thus having a good flexible and chewy taste.

[0035] At the same time, in the present invention, pullulanase and protease are used to enzymatically hydrolyze rice successively to modify the structures of rice starch and protein, so that the dried rice noodles can recover to a larger elongation rate under less water and shorter time conditions, fundamentally solving the problem that it is difficult for dried rice noodles to balance rapid rehydration and good flexibility. There is no need to rely on long-term aging and drying. Therefore, the aging and drying time in the preparation process of the dried rice noodles of the present invention is short, the energy consumption cost is low, the drying time cost and energy consumption are saved, and the process and cost of anti-retrogradation additives are eliminated; it solves the problems of long energy consumption time and high cost caused by the methods of using long-term aging and drying and adding anti-retrogradation additives in the preparation of dried rice noodles in the prior art to improve the toughness and rehydration of rice noodles.

[0036] Referring to the accompanying drawings, a preparation method of a highly flexible and soakable instant rice noodle includes the following steps:

[0037] (1) Using rice as the raw material, subjecting the rice to enzymatic hydrolysis treatment with pullulanase to hydrolyze and debranch the starch to generate a specific content of amylose;

[0038] (2) Subjecting the rice after the enzymatic hydrolysis treatment in step (1) to enzymatic hydrolysis treatment with protease to hydrolyze the rice protein into peptide chains with a specific degree of polymerization;

[0039] (3) Subject the rice enzymatically hydrolyzed in step (2) to slurry making, gelatinization, aging, and encapsulation to obtain the high-flexibility and elasticity instant rice noodles for soaking. In the present invention, pullulanase and protease are successively used to enzymatically hydrolyze rice, and the looseness of the gel network is improved by the degradation of starch and protein molecules, and the flexibility of the rice noodles is increased; the interaction between debranched starch and peptide chains of the catalytic product is utilized to increase the strength of intermolecular forces, so that the rice noodles have a high elongation rate, greatly shortening the rehydration time of the instant rice noodles, realizing the soakability of the instant rice noodles, improving the flexibility and elasticity of the instant rice noodles, reducing the breaking rate of the instant rice noodles, and the preparation process of the present invention is simple, requires a short production time, has low cost, does not require complex equipment, can realize industrial large-scale production, and does not contain any chemical additives, meeting the requirements of clean label; solving the problems of the prior art that a certain amount of food additives need to be added, and the cooking or rehydration time is long, the production process is complex, the breaking rate is high, and the chewy feeling is poor; at the same time, solving the problems that the existing instant rice noodles for soaking use freeze-drying equipment to freeze-dry to shorten the rehydration time of the instant rice noodles, the equipment cost is high, the production time is long, and it cannot be applied to industrial rice noodle production, and the instant rice noodles prepared by using freeze-drying equipment have strong rigidity, high toughness, poor chewy feeling, poor palatability, and high breaking rate.

[0040] In one embodiment, the pullulanase in step (1) is an enzyme preparation with an EC number of 3.2.1.3, derived from Bacillus licheniformis; the rice is enzymatically hydrolyzed to hydrolyze and debranch the starch in the rice.

[0041] In one embodiment, the addition amount of the pullulanase in step (1) relative to the rice is 70 - 150 U / g.

[0042] In one embodiment, the temperature for enzymatically hydrolyzing the rice with the pullulanase in step (1) is 35 - 55 °C, and the time is 3 - 6 h.

[0043] In one embodiment, the content of amylose in the hydrolysis product of the pullulanase in step (1) is 25% - 30%.

[0044] In one embodiment, the specific operation of enzymatically hydrolyzing the rice with the pullulanase in step (1) is to soak the cleaned rice in the pullulanase enzyme solution, pour out the enzyme solution after soaking for a period of time, and wash it with clear water multiple times to remove the residual enzyme solution.

[0045] In one embodiment, the protease in step (2) is one or more composite weak alkaline proteases.

[0046] In one embodiment, the protease in step (2) is one or more of bromelain, trypsin, papain, and fibrinolytic protease.

[0047] In one embodiment, the enzymatic hydrolysis treatment in step (2) using protease is specifically as follows: The rice soaked and washed with pullulanase is soaked in the protease enzyme solution. After soaking for a period of time, the enzyme solution is poured out completely, and then washed with clear water multiple times to remove the residual enzyme solution.

[0048] In one embodiment, the addition amount of the protease relative to the rice raw material is 150 - 250 U / g.

[0049] In one embodiment, the temperature for protease soaking and enzymatic hydrolysis is 25 - 50 °C, and the time is 10 - 24 h.

[0050] In one embodiment, the cooking in step (3) is carried out at 100 - 105 °C for 2 - 5 min.

[0051] In one embodiment, the aging in step (3) is carried out in a constant temperature and humidity device at a temperature of 15 - 40 °C and a humidity of 70 - 90% for 2 - 5 h.

[0052] In one embodiment, the drying temperature is 40 - 50 °C, the humidity is 70 - 80%, the drying time is 1 - 2 h, and the moisture content of the product after drying is 10% - 15%.

[0053] In one embodiment, after the encapsulation in step (3), it needs to be sterilized at 95 - 105 °C for 15 - 30 min.

[0054] Another object of the present invention is to provide a highly flexible and foamed instant rice noodles prepared by the above-mentioned method.

[0055] To make the objects, features and technical solutions of the present invention more obvious and understandable, especially to highlight the beneficial effects brought by the synergistic effects of each process of the present invention, the present invention will be described in more detail through specific embodiments below.

[0056] The present invention is described as follows:

[0057] (1) The enzymes mentioned in the following examples are: Pullulanase PL, which refers to an enzyme preparation with an EC number of 3.2.1.41, derived from Bacillus licheniformis, and purchased from Yuanye Bio;

[0058] (2) The proteases mentioned in the following examples are one or more of bromelain, trypsin, papain, and fibrinolytic protease, and are purchased from Aladdin Reagents;

[0059] (3) Determination of amylose content: The amylose content is determined using a Megazyme amylose / amylopectin detection kit.

[0060] (4) Determination of the molecular weight distribution of the peptide chain: Use a NaNO3 solution (0.1 M, containing 0.05% NaN3) as the mobile phase, with a flow rate of 0.6 mL / min and a temperature of 35 °C. Dissolve the sample in distilled water (10 mg / mL) and filter it through a 0.45 μm membrane. Inject the filtrate (20 μL) into the HPLC system and detect it with a RID-20 differential refractive index detector. Use narrow-distribution polyethylene glycol as the standard and perform further calibration using the universal calibration method.

[0061] (5) Determination of the rehydration time of the rice noodles: The high-soft-elasticity instant rice noodles after drying are uniformly determined after being stored for 3 days. Put 100 g of dried rice noodles into 500 mL of boiling water at 95 - 100 °C and soak them. Take out several rice noodles from the boiling water every 30 s (take them out every 5 s near the end to accurately time), place them between two transparent glass plates, and gently press to check if there is still a white core in the middle of the rice noodles. The time required for the white core to disappear is the rehydration time of the dried rice noodles.

[0062] (6) Texture analysis of the rice noodles: The texture properties of the rehydrated rice noodles were analyzed using a texture analyzer (TA.XTplus, 99STRATE Micro Systems Ltd, Godalming, UK). Place the noodles parallel on the metal plate and compress the noodles 2 times to 40% of the original height at a speed of 1.00 mm / s with a P / 50 probe, and set the trigger force to 5.0 g. The average values of texture parameters such as hardness, elasticity, and chewiness for each sample are 10 times.

[0063] (7) Determination of the breakage rate of the rice noodles:

[0064] Determination of the tensile properties of the rice noodles: After taking an appropriate amount of rice noodles and boiling them in boiling water until the white core disappears, select 10 rice noodles with a smooth surface and no cracks, uniformly cut their lengths to 15 cm, accurately measure and record the diameter of each rice noodle with a vernier caliper (accurate to 0.01 mm), and cover them with a warm and wet towel to prevent the rice noodles from losing water and becoming hard. Before stretching, fix the distance between the two friction rollers of the texture analyzer to 10 cm, take a rice noodle and wind it around the upper and lower two friction rollers 2 - 3 times and tie a knot to prevent any sliding during the stretching process. Stretch the rice noodle at a constant rate of 60 mm / min until the sample breaks, and record the stretching curve. The calculation formulas for the tensile stress, maximum breaking stress, tensile strain, and Young's modulus of the rice noodles are as follows:

[0065] (7.1) Tensile stress and maximum breaking stress

[0066]

[0067] In the formula: σ is the tensile stress, in Pa, and its maximum value is the maximum stress that the rice noodles bear at the time of fracture, that is, the maximum breaking stress, which is often used to indicate the gel strength of the rice noodles.

[98] ; F is the tensile strength measured by the texture analyzer, in g; A 0 is the cross-sectional area of the rice noodles before stretching, in m 2 .

[0068] (7.2) Tensile strain

[0069]

[0070] In the formula: ε is the tensile strain, in %, indicating the degree of deformation of the rice noodles during stretching; Δl is the length by which the rice noodles elongate when stretching the rice noodles, in mm; l 0 is the initial length of the rice noodles, in mm.

[0071] (7.3) Young's modulus

[0072]

[0073] In the formula: E is Young's modulus, in Pa, indicating the ability of the rice noodle gel to resist elastic deformation, representing the rigidity of the gel, that is, the larger this value, the smaller the ability of the rice noodles to undergo elastic deformation under the action of the same stress.

[0074] (8) Sensory quality evaluation of rice noodles: Sensory evaluation uses blind evaluation of samples, and the specific reference standards are shown in Table 1. Twenty sensory evaluators were screened and trained, and the appearance, smell, and taste of the rice noodle products were evaluated and scored, and the average score was taken.

[0075] Table 1 Sensory scoring standards for rice noodles / rice noodles / noodles

[0076]

[0077] The rice used in the examples is Pearl No. 3 early indica rice, which is stored for 12 months after harvesting.

[0078] Example 1:

[0079] A preparation method for highly flexible pickled instant rice noodles, specifically using the following steps:

[0080] Washing rice: Wash the rice twice with tap water, wash away the surface impurities, discard the rice washing water, and add water twice the mass of the rice;

[0081] (1) Immersion with pullulanase enzyme solution: Add 100 U / g pullulanase (derived from Bacillus licheniformis) to the mixture of rice and water obtained in step (1), adjust the pH to 5.0, and soak at 50 °C for 5 h; after the soaking is completed, wash the rice many times with clear water and completely wash away and discard the enzyme solution;

[0082] (2) Soaking with protease enzyme solution: Add water twice the amount of the rice obtained in step (2) to the washed rice, and at the same time add trypsin at 200 U / g for generating peptide segments with hydrophobic residues at the C-terminus, adjust the pH to 8.0, and soak at 50 °C for 24 h;

[0083] (3) Pulping: Drain the rice soaked with the enzyme solution obtained in step (2) after washing, put it into a pulper according to the mass ratio of water to rice of 3:5, and add water to carry out pulping to obtain a slurry;

[0084] Extruding powder: Pour the slurry into a rice noodle machine, and cook at 103 °C for 3.5 min to obtain rice noodles;

[0085] Aging: Place the obtained rice noodles in a constant temperature and humidity device at a temperature of 25 °C and a humidity of 70% for aging for 5 h to obtain aged rice noodles;

[0086] Drying: Place the aged rice noodles in a convective hot air drying device at a temperature of 45 °C for drying for 2 h to obtain dry rice noodles;

[0087] Measure the moisture content of the dried rice noodles, and bag the dry rice noodles with a moisture content of 10%-15% to obtain high-soft-elastic pickled instant rice noodles.

[0088] The design of the control group is shown in Table 1.

[0089] Table 1 Enzymatic hydrolysis methods and addition amounts of examples and control examples

[0090]

[0091]

[0092] Example 2

[0093] Refer to the method of Example 1, the difference is only that: in step (1), the concentration of pullulanase is 100 U / g, the temperature is 50 °C, and the treatment time is 5 h; in step (2), the concentration of protease is 150 U / g, the temperature is 50 °C, and the treatment time is 24 h; others are the same as in Example 1; the obtained rice noodle product is denoted as Example 2 (DZM).

[0094] Example 3

[0095] Refer to the method of Example 1, the difference is only that: in step (1), the concentration of pullulanase is 70 U / g, the temperature is 50 °C, and the treatment time is 5 h; in step (2), the concentration of protease is 180 U / g, the temperature is 50 °C, and the treatment time is 18 h; others are the same as in Example 1; the obtained rice noodle product is denoted as Example 3 (PSM).

[0096] Example 4

[0097] Refer to the method of Example 1, with the only difference being that: in step (1), the concentration of pullulanase is 100 U / g, the temperature is 50 °C, and the treatment time is 5 h; in step (2), the concentration of protease is 180 U / g, the temperature is 50 °C, and the treatment time is 24 h; other conditions are the same as in Example 1; the produced rice flour product is denoted as Example 4 (DZH).

[0098] Control Example 1

[0099] Refer to the method of Example 1, with the only difference being that steps (1) and (2) are respectively replaced by soaking the fresh rice with water, and other conditions are the same as in Example 1; the produced rice flour product is denoted as Control Example 1-1 (KN).

[0100] Control Example 2

[0101] Refer to the method of Example 1, with the only difference being that step (2) treatment is omitted, and only pullulanase soaking treatment is used, and other conditions are the same as in Example 1; the produced rice flour product is denoted as Control Example 1-2 (PN).

[0102] Control Example 3

[0103] Refer to the method of Example 1, with the only difference being that step (1) is omitted, and only protease soaking is used, and other conditions are the same as in Example 1; the produced rice flour product is denoted as Control Example 1-4 (DN).

[0104] Control Example 4

[0105] Refer to the method of Example 1, with the differences being that in step (1), the concentration of pullulanase is 150 U / g, the temperature is 55 °C, and the treatment time is 6 h; in step (2), the concentration of protease is 250 U / g, the temperature is 50 °C, and the treatment time is 24 h; other conditions are the same as in Example 1; the produced rice flour product is denoted as Control Example 1-4 (GN).

[0106] Control Example 5

[0107] Refer to the method of Example 1, with the only difference being that: in step (1), the concentration of pullulanase is 40 U / g, the temperature is 40 °C, and the treatment time is 3 h; in step (2), the concentration of protease is 100 U / g, the temperature is 45 °C, and the treatment time is 12 h; other conditions are the same as in Example 1; the produced rice flour product is denoted as Control Example 1-5 (QN).

[0108] Control Example 6

[0109] Referring to the method of Example 1, the difference is only that: in step (1), the concentration of pullulanase is 100 U / g, the temperature is 50 °C, and the treatment time is 5 h; in step (2), the concentration of protease is 250 U / g, the temperature is 50 °C, and the treatment time is 24 h; other conditions are the same as those in Example 1; the produced rice noodle product is denoted as Control Example 1-6 (DGN).

[0110] Control Example 7

[0111] Referring to the method of Example 1, the difference is only that: in step (1), the concentration of pullulanase is 100 U / g, the temperature is 50 °C, and the treatment time is 5 h; in step (2), the concentration of protease is 100 U / g, the temperature is 50 °C, and the treatment time is 24 h; other conditions are the same as those in Example 1; the produced rice noodle product is denoted as Control Example 1-7 (DQL).

[0112] Control Example 8

[0113] Commercially available pickled rice noodles.

[0114] Control Example 9

[0115] Referring to the method of Example 1, the difference is only that: in step (1), pullulanase derived from Bacillus acidopullulyticus is used, and other conditions are the same as those in Example 1; the produced rice noodle product is denoted as Control Example 9.

[0116] The rice noodle products prepared in the above examples and control examples were tested and analyzed, and the results are as follows:

[0117] (1) The results of the chewiness (tensile strength, elongation at break, and breaking rate), soaking time, and sensory score of the rice noodles are shown in Table 2.

[0118] Table 2 Mechanical indexes related to the rehydration duration and chewiness of rice noodles

[0119]

[0120] (2) The measured results of the amylose content and the molecular weight of protease hydrolysis products of the examples and control examples are shown in Table 3:

[0121] Table 3 Amylose content and molecular weight of protease hydrolysis products of the examples and control examples

[0122]

[0123] As can be seen from Table 2, combining pullulanase and protease can simultaneously improve the rehydration rate of dry rice noodles and the chewiness of rehydrated rice noodles. The specific analysis is as follows:

[0124] Control 1 was a blank sample, which was difficult to ripen under soaking conditions. The rice noodles showed high rigidity (tensile strength 35.2 g), lack of elasticity (elongation rate 80%), and a state that was inedible (sensory score 50.6). When pullulanase was used alone (Control Example 2), compared with Control 1, its rehydration time was slightly reduced, but the chewiness and taste of the rice noodles were still poor; when protease was used alone (Control Example 3), the rehydration time of the rice noodles was significantly reduced, and the rehydrated rice noodles showed a soft but elastic state. However, compared with Example 1, this elasticity still had a large gap, that is, the taste was not ideal. It can be seen that pullulanase can only significantly reduce the rigidity of rice noodles and increase the flexibility, but has a weak ability to increase the elasticity of rice noodles; Control Example 3 shows that using protease alone can improve the flexibility and elasticity of rice noodles at the same time and reduce the rehydration time, but the rehydration time far from reaches the convenient state (requires <360 s), and the texture quality cannot reach the chewy taste. In Example 1, the two enzymes were combined and catalyzed under high enzyme activity conditions, and the prepared rice noodles had the best sensory score of 91.3, the shortest rehydration time of 250 s and the thickest diameter of 2.5 mm. This effect was far better than using pullulanase alone (Control Example 2) or protease alone (Control Example 3).

[0125] Pullulanase and protease can only effectively improve the flexibility, elasticity and chewiness of dried rice noodles when they act synergistically under suitable catalytic conditions. The specific analysis is as follows:

[0126] (1) As can be seen from Table 2, when the hydrolysis degree of pullulanase was too high (such as Control Example 4, 200 U / g), although a large number of linear segments (amylose content 36.5%) were produced by pullulanase debranching at this time, due to the high hydrolysis of amylopectin, the starch gelation ability was significantly reduced, resulting in the prepared rice noodles lacking appropriate toughness (tensile strength 9.1 g) and elasticity (elongation rate 118%), and the sensory score was low (57 points). Therefore, although the rehydration time of Control Example 4 was significantly shorter than that of Control 1, the texture quality was poor. When the hydrolysis degree of pullulanase was too low (such as Control Group 5, only treated with 40 U / g), the starch was only slightly degraded, and the rehydration rate and texture quality of the rice noodles were not significantly different from those of Control Example 1. It shows that too high or too low pullulanase cannot significantly improve the quality of dried rice noodles.

[0127] (2) It can be seen from Table 3 that when the protease is over-hydrolyzed (Control Example 6), the average molecular weight of the product is less than 1000, indicating that the protein is broken down into more amino acids. Since the strength of the amino acid-starch synergistic interaction is lower than the peptide chain-starch synergistic interaction, the elasticity of the rice noodles (elongation 120%) is significantly reduced. When the degree of protease hydrolysis is low (such as Control Example 7), the protein is not sufficiently degraded, the product molecular weight is in the range of >10,000Da, the protein does not form enough short peptide chains, and the inhibitory effect of the larger molecular weight on the starch regeneration is weak, resulting in the rice noodles being still relatively tough after rehydration, the rice noodles having a hard taste (tensile strength 11.2g), and insufficient elasticity (elongation 165%). When the protease is degraded to a higher degree, it is most helpful to cooperate with pullulanase to prepare dry rice noodles with better quality (Examples 1 and 3, 4). As shown in Table 3, in Example 1 and Example 3 and Example 4, the molecular weight range of the protease hydrolyzate is 3000-10,000Da, indicating that moderate protein degradation forms a certain amount of small peptides, so that the rice noodles have both a chewy feel (>150%) and moderate hardness (tensile strength 15-20g), and the mouthfeel of the rice noodles is close to the best, with a high score (>80 points, and both are higher than the commercially available product control example 8), but the soaking time of the dried rice noodles prepared in Examples 3 and 4 still does not reach the optimal level.

[0128] (3) Combining Table 2 and Table 3, it can be seen that the combination of pullulanase with a higher degree of hydrolysis (100U / g) and protease with a higher degree of hydrolysis (200U / g) has the best rice flour quality: Example 1 (SSN) uses pullulanase with a higher degree of hydrolysis and protease treatment to increase the straight chain starch content of rice flour to 26.5%, indicating that the starch molecules are fully degraded while maintaining suitable linear segments in the system; after protein hydrolysis, 3000-10,000Da peptide chains are mainly formed. The peptide chains have strong flexibility due to their slightly shorter length and can fully interact with starch. This interaction effectively promotes the increase in the plasticity of rice flour gel. Therefore, while the rice flour has suitable rigidity (tensile strength 19g), it has the greatest elasticity (elongation of 230%) and the highest sensory score (91.3). At the same time, due to the higher degree of hydrolysis (but not excessive hydrolysis), it is difficult for starch molecules to regenerate into dense gels, and the gel flexibility is significantly increased, so that the dry rice flour needs less water to restore the maximum tensile strain. Therefore, under this condition, Example 1 has the shortest rehydration time (250s). It can be seen that the present invention achieves the best rice noodle quality by scientifically optimizing the combination of pullulanase and protease (as shown in Example 1 (SSN)). The highly flexible and elastic instant rice noodles prepared by the method of the present invention have the best performance in terms of rehydration time, chewiness, rice noodle structure stability and consumer sensory evaluation, providing an ideal optimization solution for instant instant rice noodles.

[0129] (4) The pullulanase in the present invention has irreplaceability. For example, when using pullulanase derived from Bacillus acidopullulyticus to replace pullulanase derived from Bacillus licheniformis for soaking to prepare rice noodles (Control Example 9), it was found that under the same conditions, the texture quality (Table 1) and sensory score (Table 2) of the dried rice noodles prepared in Control Example 9 were improved compared to the blank, but far lower than those in Example 1 and the commercial product Example 3. This indicates that not any combination of debranching enzymes or hydrolytic enzymes and proteases can achieve the technical effects of the present invention.

[0130] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Anyone familiar with this technology can make various modifications and decorations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

[0131] Other parts not described are all prior art.

Claims

1. A method for preparing highly flexible and elastic instant rice noodles, characterized in that: The following steps are included: Step (1): using rice as raw material and enzymolyzing the rice with pullulanase; Step (2): using protease to hydrolyze the rice after the enzymatic hydrolysis treatment in step (1) to produce short peptides; Step (3): the rice after enzymatic hydrolysis in step (2) is subjected to slurrying, maturation, aging and packaging to obtain highly soft and elastic instant rice noodles.

2. The method for preparing the highly flexible and elastic instant rice noodles according to claim 1, wherein: The specific method of enzymolysis of rice by pullulanase in step (1) is: soaking the rice in pullulanase solution, pouring out the enzyme solution after soaking for a period of time, and washing with clean water to remove residual enzyme solution.

3. The method for preparing the highly flexible and elastic instant rice noodles according to claim 1 or 2, characterized in that: The pullulanase is derived from Bacillus licheniformis, and the added amount of the pullulanase to the rice is 70-150 U / g.

4. The method for preparing the highly flexible and elastic instant rice noodles according to claim 3, characterized in that: The pullulanase in step (1) performs enzymolysis on rice for 3 to 6 hours; The pullulan enzymatic hydrolysis product in step (1) has an amylose content of 25% to 30%.

5. The method for preparing the highly flexible and elastic instant rice noodles according to claim 4, characterized in that: The specific method of using protease for enzymatic hydrolysis in step (2) is: soak the rice that has been enzymatically hydrolyzed and soaked with pullulanase and then washed in a protease solution, pour out the enzyme solution after soaking for a period of time, and wash with clean water to remove the residual enzyme solution.

6. The method for preparing the highly flexible and elastic instant rice noodles according to claim 5, characterized in that: The protease is a weak alkaline protease; The amount of protease added to the rice raw material is 150-250 U / g; The enzymatic hydrolysis time of rice by protease is 10 to 30 hours.

7. The method for preparing the highly flexible and elastic instant rice noodles according to claim 6, characterized in that: The protease is one or more of bromelain, trypsin, pancreatic protease, papain, and fibrinolytic protease.

8. The method for preparing the highly flexible and elastic instant rice noodles according to claim 7, characterized in that: The molecular weight of the short peptides produced by enzymatic hydrolysis of the protein in step (2) is 3-10 kDa.

9. The method for preparing the highly flexible and elastic instant rice noodles according to claim 8, characterized in that: In step (1), the amount of pullulanase added to the rice is 100 U / g, and the pullulanase is used to enzymolyze the rice for 5 hours; In step (2), the amount of protease added to the rice raw material is 200 U / g; and the enzymolysis time of the protease to the rice is 24 h.

10. A highly flexible and elastic instant rice noodle, characterized in that: The method is prepared by any one of claims 1 to 9.

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