A sodium bicarbonate-assisted open-pore type of high rehydration quick-cooking rice, its preparation method and application

Abstract

This invention relates to the field of food deep processing technology, and particularly to a sodium bicarbonate-assisted open-pore type of high-rehydration instant rice, its preparation method, and its application. The compound dry powder of this invention comprises the following components in parts by weight: 450-550 parts pregelatinized corn starch, 100-200 parts wheat starch, 4-8 parts monoglyceride, 1-3 parts sodium bicarbonate, and 4239-4445 parts indica rice flour. The compound dry powder is used to prepare instant rice, which, under 6-minute rehydration conditions, exhibits a higher rehydration ratio, a higher percentage of intact grains, and a lower dry sample breakage rate. Simultaneously, the finished product moisture content is controlled within the low moisture drying endpoint range of below 8%, providing a basis for the preparation of high-rehydration instant rice.

Description

Technical Field

[0001] This invention relates to the field of food deep processing technology, and in particular to a sodium bicarbonate-assisted open-pore type high rehydration fast-cooking rice, its preparation method, and its application. Background Technology

[0002] Instant rice, convenient rice, and instant rice products have high application value in the convenient staple food sector due to their ease of consumption, stable storage and transportation, and suitability for large-scale production. Existing instant rice products typically need to simultaneously consider rehydration speed, water absorption capacity, grain integrity, textural stability after rehydration, and clarity of the rehydrated solution. Simply increasing puffing strength or porosity to shorten rehydration time can easily lead to excessively loose grains, resulting in problems such as scattered grains, excessive gelatinization, increased adhesion, and turbidity in the rehydrated solution. Conversely, emphasizing only the integrity of the shape may result in insufficient internal rehydration channels, limiting rehydration efficiency and water absorption.

[0003] Therefore, there is an urgent need to establish a method for preparing instant rice that can form open rehydration channels inside the grains while maintaining structural stability after rehydration. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium bicarbonate-assisted open-pore type of high-rehydration instant rice, its preparation method and application, so as to solve the problem that it is difficult to balance the construction of rehydration channels, water absorption capacity and structural stability after rehydration in existing instant rice.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a compound dry powder comprising the following components in parts by weight: 450-550 parts pregelatinized corn starch, 100-200 parts wheat starch, 4-8 parts monoglyceride, 1-3 parts sodium bicarbonate, and 4239-4445 parts rice flour.

[0006] Preferably, the components include the following parts by mass: 470-530 parts pregelatinized corn starch, 120-180 parts wheat starch, 5-7 parts monoglyceride, 1.5-2.5 parts sodium bicarbonate, and 4280.5-4403.5 parts rice flour.

[0007] Preferably, the components include the following parts by mass: 500 parts pregelatinized corn starch, 150 parts wheat starch, 6 parts monoglyceride, 2 parts sodium bicarbonate, and 4342 parts indica rice flour.

[0008] The present invention also provides the application of the compound dry powder in the preparation of highly rehydrated quick-cooking rice.

[0009] This invention also provides a method for preparing highly rehydrated quick-cooking rice, comprising the following steps: (1) Weigh each component according to the mass fractions of the compound dry powder described above; (2) Mix rice flour, monoglyceride and sodium bicarbonate for 4-6 minutes to obtain a mixture; (3) Mix the mixture with pregelatinized corn starch and wheat starch for 4-6 minutes to obtain compound dry powder; (4) Mix the compound dry powder with water to obtain a wet material; (5) Let the wet material stand for 20-30 minutes, then extrude and puff it, and cut it into pellets to obtain a semi-finished product; (6) The semi-finished product is shaped and dried to obtain high-moisture quick-cooking rice.

[0010] Preferably, the mass ratio of the compound dry powder to water is 5:0.95~1; When mixing the compound dry powder with water, add the water in 6 to 8 portions, mixing for 1 to 2 minutes after each addition, and mixing for 4 to 6 minutes after the last addition.

[0011] Preferably, the extrusion puffing temperature is 85~150℃, and the extrusion puffing speed is 230~250 rpm; The length of the diced pellets is 4-5 mm.

[0012] Preferably, the setting temperature is 100~110℃, and the setting time is 1.5~2.5min; The drying method involves first drying at 78-82℃ for 18-22 minutes, and then drying at 73-77℃ until the moisture content is ≤8%.

[0013] The present invention also provides high rehydration quick-cooking rice prepared according to the preparation method described herein, wherein the intact grain rate after rehydration in water at a temperature of 90°C or higher is ≥80%.

[0014] The present invention also provides the application of the high rehydration quick-cooking rice or the high rehydration quick-cooking rice prepared by the above preparation method in the preparation of quick-cooking rice or meal replacement foods.

[0015] Beneficial effects

[0016] First, trace amounts of sodium bicarbonate generate a small amount of gas during the extrusion hot processing, which, under the experimental conditions, suggests that it helps to form open channels and improve the water absorption capacity of particles. Secondly, pregelatinized corn starch helps improve the water absorption, swelling, and molding stability of the powder system, while wheat starch helps adjust the structural strength. Third, two-step mixing and multiple water additions for mixing and conditioning can reduce the risk of local agglomeration and white hard core agglomerates, and improve the stability of extruded material; Fourth, the segmented hot air route of short-time shaping, 80℃ pore-preserving drying, and 75℃ final dehydration is beneficial for fixing the shape of the grains, resulting in high whole grain rate and low adhesion of instant rice under the experimental conditions. Attached Figure Description

[0017] Figure 1 Flowcharts for the preparation of highly rehydrated instant rice in Examples 1 and Comparative Examples 1-2; Figure 2 Comparison of the basic mass and rehydration performance of instant rice prepared by different methods; Figure 3 The open pore structure and textural properties of instant rice prepared by different methods; Figure 4 RVA gelatinization characteristics of instant rice prepared by different methods; Figure 5 Photographs showing the turbid state of rehydrated instant rice prepared by different methods. Detailed Implementation

[0018] 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.

[0019] The formulations and post-processing methods of the high-rehydration quick-cooking rice of Examples 1, 2, and Comparative Examples 1-2 of this invention are shown in Table 1, and the process flow is as follows: Figure 1 As shown.

[0020] Table 1. Formulations of Examples 1-2 and Comparative Examples 1-2

[0021] Each compound dry powder was prepared in batches of 5 kg. P2-C2′ was not prepared separately, but was obtained by diverting the semi-finished products from the same batch of P2-E1′ and using a 95℃ constant temperature hot air route; P2-V1′ was a reserved verification batch and was not included in the complete test results of this round.

[0022] The specific preparation methods for each group are as follows: Example 1

[0023] Preparation of high-rehydration instant rice P2-E1′

[0024] Weigh out 4342g of indica rice flour, 500g of pregelatinized corn starch, 150g of wheat starch, 6g of monoglyceride, and 2g of sodium bicarbonate according to Table 1. Pass the indica rice flour, pregelatinized corn starch, and wheat starch through a 60-mesh sieve. Since the amounts of monoglyceride and sodium bicarbonate are relatively low, first take 0.5 kg of indica rice flour and premix it with monoglyceride and sodium bicarbonate in a small packet for 5 minutes to obtain a mixture. Then mix the mixture with the remaining materials for 5 minutes to obtain a compound dry powder. Subsequently, add 1000g of purified water to 5.00 kg of the compound dry powder using a fine mist spraying method, adding it in 8 portions, mixing for 2 minutes after each addition, and continuing to mix for 5 minutes after all the water has been added to obtain a wet material. Seal the wet material and let it stand for 25 minutes, then stir it again after standing.

[0025] The conditioned wet material is added to a twin-screw extruder, with the temperature zones set sequentially to 85℃, 105℃, 125℃, 145℃, and 150℃, and the screw speed at 240 rpm. A rice-grain-shaped die is used, and the pellet length is controlled to be 4-5 mm. After stable discharge, the semi-finished product is collected, spread in a single layer, and first shaped with hot air at 105℃ for 2 minutes, then dried with hot air at 80℃ for 20 minutes, and finally dried at 75℃ until the moisture content of the finished product is no higher than 8%. After natural cooling for 30 minutes, it is packaged.

[0026] Example 2

[0027] P2-V1′ uses the exact same formulation and process as P2-E1′ and is reserved as a reserve batch for subsequent repeated batch observation and supplementary validation. Since the current complete test data mainly comes from P2-E1′, P2-C1′, and P2-C2′, this specification does not use P2-V1′ as evidence of process repeatability or stability.

[0028] Comparative Example 1

[0029] Preparation of sodium bicarbonate-free sample P2-C1′

[0030] Except for the absence of sodium bicarbonate and the adjustment of the rice flour to 4344g, the other raw materials, water addition, extrusion conditions, and segmented hot air route were the same as in Example 1. This Comparative Example 1 is used to illustrate the contribution of sodium bicarbonate to the formation of open channels, rehydration ratio, and particle shape retention.

[0031] Comparative Example 2

[0032] Preparation of homologous isothermal hot air control P2-C2′

[0033] P2-C2′ was not prepared separately, but was obtained by splitting the same batch of semi-finished products as P2-E1′. In the post-processing stage, this sample did not employ the segmented route of short-time setting at 105℃, pore-preserving drying at 80℃, and final dehydration at 75℃. Instead, it was directly dried with constant-temperature hot air at 95℃ until the finished product moisture content did not exceed 8%. This control is used to illustrate the differences in rehydration and texture performance under different post-processing routes. Because there is a difference in the final moisture content between P2-E1′ and P2-C2′, not all differences are attributed to the drying route; it is only used as a homologous post-processing control under the conditions of this experiment.

[0034] Experimental Example 1

[0035] The basic validation indicators include finished product moisture content, dry sample breakage rate, rehydration completion time, rehydration ratio, intact particle rate, and turbidity of the rehydrated solution. The finished product moisture content was determined using the 105℃ drying to constant weight method; the moisture values ​​in the table are from a single measurement. The dry sample breakage rate was calculated as the percentage of broken particles in the dry sample. The rehydration completion time was defined as rehydration at 95℃ hot water until no obvious white core was observed upon cutting. The rehydration ratio was calculated as the ratio of the mass of the drained sample after rehydration to the mass of the dry sample. The intact particle rate was calculated by randomly selecting 30 particles after the rehydration endpoint and counting them, then calculating the percentage as (number of intact particles / 30) × 100%. The turbidity of the rehydrated solution was assessed using photographs taken under the same background. The results are shown in Table 2 and... Figure 1 As shown.

[0036] Table 2 Results of Basic Mass and Rehydration Performance of the Invention

[0037] Note: The moisture content of the finished product was determined by drying at 105℃ to constant weight. The moisture values ​​in the table are the results of a single measurement. The dry sample breakage rate, rehydration time, rehydration ratio, and intact particle rate were all statistically analyzed in triplicate, and the results are expressed as mean ± standard deviation. The moisture content of all samples was below 8%, meeting the low moisture drying endpoint control requirements set by this process.

[0038] Table 2 and Figure 2The results show that the rehydration completion time for P2-E1′, P2-C1′, and P2-C2′ is 6 minutes, therefore the current data should not be interpreted as significantly shortening the white core-free endpoint time. However, the rehydration ratio of P2-E1′ is 2.77±0.04, which is higher than that of the sodium bicarbonate-free control P2-C1′ (1.95±0.35); its intact particle rate is 90.00±3.33%, which is higher than that of P2-C1′ (77.78±3.85%) and the homologous constant-temperature hot air control P2-C2′ (74.44±8.39%). Meanwhile, the dry sample breakage rate of P2-E1′ is 2.16±0.42%, lower than that of P2-C1′ and P2-C2′. This indicates that the main advantage of this invention is not simply shortening the white core-free endpoint time, but rather improving water absorption capacity, reducing dry sample breakage rate, and maintaining good particle shape integrity at similar rehydration times.

[0039] Experimental Example 2

[0040] The open porosity, hardness, adhesiveness, cohesiveness, and structure and texture of instant rice samples P2-C1′, P2-E1′, and P2-C2′ were analyzed. The results are shown in Table 3. Figure 3 As shown.

[0041] Open porosity was determined using the ethanol displacement method. Whole instant rice samples were taken and equilibrated for 24 h at 25℃ and 60% relative humidity before testing. 20.0 mL of anhydrous ethanol was added to a graduated cylinder, and the initial volume V1 was recorded. 3.00 g of sample was weighed and slowly added to the graduated cylinder, gently agitated to remove any adhering air bubbles, and the total volume after adding the sample was recorded as V2. The sample was allowed to stand at room temperature for 30 min, gently agitated every 5 min to ensure sufficient ethanol penetration into the sample's pores, and the remaining ethanol volume V3 was recorded. Porosity was calculated using the formula Porosity = (V1 - V3) / (V2 - V3) × 100%. Each sample was measured three times, and the results are expressed as mean ± standard deviation.

[0042] Texture properties were determined using the TPA double compression method with a texture analyzer. After rehydration to the rehydration endpoint, the samples were cooled at 25°C for 30 min to stabilize the temperature. The samples were then arranged into 2.0 cm × 2.0 cm × 2.0 cm molding test units, and tested using a 25 mm cylindrical probe and a 50 N force sensor. The test parameters were: pre-test velocity 2.0 mm / s, test velocity 1.0 mm / s, post-test velocity 1.0 mm / s, compression deformation rate 50%, trigger force 0.05 N, and interval between two compressions 5 s. Six molding test units were tested for each parallel sample, and hardness, adhesion, cohesion, and other indicators were recorded. The average values ​​were used for statistical analysis.

[0043] Table 3. Open pore structure and textural properties of different fast-cooking rice varieties after rehydration

[0044] Note: Open porosity was measured using the ethanol displacement method, with each sample group measured three times; TPA texture testing was performed on six molding test units for each parallel sample, and the results are expressed as mean ± standard deviation.

[0045] Table 3 and Figure 3 The results show that the open porosity of P2-E1′ is 51.59±23.85%, which is higher than that of the sodium bicarbonate-free control P2-C1′ (24.61±23.31%), suggesting that trace amounts of sodium bicarbonate-assisted extrusion puffing may help form more open rehydration channels. The open porosity of P2-C2′ reaches 65.67±14.38%, but its adhesiveness increases to 13.86±2.86 mJ, and its intact particle rate is lower than that of P2-E1′, indicating that simply increasing the degree of open porosity does not necessarily lead to better rehydration quality. It should be noted that the final moisture content of P2-E1′ and P2-C2′ differs, and the related differences should be attributed cautiously. Under the experimental conditions, the segmented hot air shaping and porosity-preserving route corresponds to better overall performance. The hardness of P2-E1′ is 4.72±1.22 N, the adhesion is 6.55±2.92 mJ, and the cohesion is 0.84±0.13, indicating that it can still maintain a good structural state after rehydration under high rehydration ratio conditions.

[0046] Experimental Example 3

[0047] The gelatinization characteristics of instant rice samples P2-C1′, P2-E1′, and P2-C2′ were tested. The results are shown in Table 4. Figure 4 As shown.

[0048] The RVA gelatinization characteristics were determined according to GB / T 22427.7-2023 "Determination of Starch Viscosity Part 7: RVA Method" and NY / T 1753-2009 "Determination of Gelatinization Characteristics of Rice Flour - Rapid Viscosity Analyzer Method". First, the moisture content of the sample was determined according to GB 5009.3-2016. The instant rice sample was pulverized and passed through a 0.42 mm standard sieve. The sample powder was weighed at a dry basis of 3.00 g, and 25.0 ± 0.1 mL of distilled water was added. The mixture was placed in a dedicated RVA sample container and stirred thoroughly, avoiding the generation of excessive air bubbles. The test procedure was as follows: initial temperature of 50℃ for 1 min, then increased to 95℃ at a rate of 12℃ / min, maintained at 95℃ for 2.5 min, then decreased to 50℃ at a rate of 12℃ / min, and maintained at 50℃ for 2 min; the stirring speed was 960 rpm for the first 10 s, and then 160 rpm throughout. Record the peak viscosity (PV), final viscosity (FV), disintegration value (BD), and regeneration value (SB) and other indicators, and statistically analyze the results based on valid parallel samples.

[0049] Table 4. RVA gelatinization characteristics of different fast-cooking rice varieties.

[0050] Note: PV is peak viscosity, FV is final viscosity, BD is disintegration value, and SB is regeneration value.

[0051] RVA results showed that the peak viscosity and final viscosity of P2-E1′ were both higher than those of P2-C1′, indicating that the compound extrusion system involving sodium bicarbonate did not weaken the water absorption and swelling potential of the base material. The PV and FV of P2-C2′ were similar to those of P2-E1′, but its intact particle ratio was lower and its adhesion was higher. Therefore, the RVA results cannot explain the final rehydration quality alone, and it is still necessary to make a comprehensive judgment based on the rehydration ratio, intact particle ratio, open porosity, and TPA index.

[0052] Experiment Example 4

[0053] The rehydrated state of instant rice containing P2-C1′, P2-E1′, and P2-C2′ was determined. The results are shown in Table 5. Figure 5 As shown.

[0054] The rehydration state of the system was observed under uniform rehydration conditions. 10.00 g of dry sample was accurately weighed and placed in a 250 mL covered beaker. 80 mL of 95℃ hot water was added, the beaker was immediately capped, and timing began. Rehydration was completed according to the endpoints corresponding to the rehydration times for each sample in Table 2. After gently shaking, the rehydrated solution was transferred to a transparent glass beaker and photographed under the same light source, shooting distance, and background conditions. This observation is only used to describe the appearance of the rehydrated system; since a turbidimeter was not used to measure the NTU value, and a uniform turbidity rating was not established, this experimental example is not intended as a quantitative turbidity conclusion or a basis for limiting the claims.

[0055] Table 5. System state after rehydration of different fast-cooking rice varieties.

[0056] Table 5 and Figure 5 This is only for demonstrating the appearance of different rehydrated samples. Since this set of materials is a photographic record rather than instrument turbidity values, this specification does not use it as a quantitative conclusion, nor as a basis for limiting the claims; if the turbidity of the rehydrate is to be used as a formal technical effect in the future, NTU turbidity values ​​or standardized turbidity rating results should be added.

[0057] In summary, under 6 min rehydration conditions, P2-E1′ exhibits a higher rehydration ratio, higher intact particle rate, and lower dry sample breakage rate compared to the sodium bicarbonate-free control; compared to the isothermal hot air control, it demonstrates a more balanced intact particle rate and post-rehydration textural stability. The conclusion has been revised to emphasize "balancing water absorption capacity, particle formation stability, and post-rehydration textural stability at similar rehydration times," avoiding the statement that it simply involves shortening the rehydration time.

[0058] As can be seen from the above embodiments, the present invention, through the compounding of pregelatinized corn starch, wheat starch, monoglycerides, and trace amounts of sodium bicarbonate, combined with multiple water additions for conditioning, extrusion puffing, and segmented hot air drying, can form certain open channels inside the instant rice particles while maintaining the particle structure after rehydration. Under rehydration conditions of approximately 6 minutes, the core embodiment P2-E1′ exhibits a higher rehydration ratio, a higher intact particle rate, and a lower dry sample breakage rate compared to the sodium bicarbonate-free control P2-C1′; compared to the same source constant temperature hot air control P2-C2′, its intact particle rate and post-rehydration textural stability are more balanced. The above results indicate that the technical effect of the present invention is mainly reflected in balancing water absorption capacity, particle integrity, dry sample granulation stability, and post-rehydration textural stability at a similar rehydration completion time, rather than simply shortening the rehydration completion time.

[0059] 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 compound dry powder, characterized in that, The components include the following parts by mass: 450-550 parts pregelatinized corn starch, 100-200 parts wheat starch, 4-8 parts monoglyceride, 1-3 parts sodium bicarbonate, and 4239-4445 parts rice flour.

2. The compound dry powder according to claim 1, characterized in that, The components include the following parts by mass: 470-530 parts pregelatinized corn starch, 120-180 parts wheat starch, 5-7 parts monoglyceride, 1.5-2.5 parts sodium bicarbonate, and 4280.5-4403.5 parts rice flour.

3. The compound dry powder according to claim 1, characterized in that, The components include the following parts by mass: 500 parts pregelatinized corn starch, 150 parts wheat starch, 6 parts monoglyceride, 2 parts sodium bicarbonate, and 4342 parts indica rice flour.

4. The application of the compound dry powder according to any one of claims 1 to 3 in the preparation of highly rehydrated instant rice.

5. A method for preparing high-rehydration quick-cooking rice, characterized in that, Includes the following steps: (1) Weigh each component according to the mass fraction of the compound dry powder according to any one of claims 1 to 3; (2) Mix rice flour, monoglyceride and sodium bicarbonate for 4-6 minutes to obtain a mixture; (3) Mix the mixture with pregelatinized corn starch and wheat starch for 4-6 minutes to obtain compound dry powder; (4) Mix the compound dry powder with water to obtain a wet material; (5) Let the wet material stand for 20-30 minutes, then extrude and puff it, and cut it into pellets to obtain a semi-finished product; (6) The semi-finished product is shaped and dried to obtain high-moisture quick-cooking rice.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the compound dry powder to water is 5:0.95~1; When mixing the compound dry powder with water, add the water in 6 to 8 portions, mixing for 1 to 2 minutes after each addition, and mixing for 4 to 6 minutes after the last addition.

7. The preparation method according to claim 5, characterized in that, The extrusion puffing temperature is 85~150℃, and the extrusion puffing speed is 230~250 rpm; The length of the diced pellets is 4-5 mm.

8. The preparation method according to claim 5, characterized in that, The setting temperature is 100~110℃, and the setting time is 1.5~2.5min; The drying method involves first drying at 78-82℃ for 18-22 minutes, and then drying at 73-77℃ until the moisture content is ≤8%.

9. The high-rehydration quick-cooking rice obtained by the preparation method according to any one of claims 5 to 8, characterized in that, The intact particle rate after rehydration in water at a temperature above 90℃ is ≥80%.

10. The use of the high-rehydration instant rice according to claim 9 or the high-rehydration instant rice prepared by the preparation method according to any one of claims 5 to 8 in the preparation of instant rice or meal replacement foods.

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