Instant red beans and its preparation method

Abstract

The present invention relates to instant red beans and a method for preparing the same. The present invention discloses a method for preparing instant red beans, which comprises the following steps: subjecting red beans to pre-drying treatment, which includes at least one of the following: freeze-drying treatment and superheated steam drying treatment; subjecting the pre-dried red beans to ripening treatment; and subjecting the ripened red beans to vacuum drying treatment and hot air puffing treatment in sequence, whereby the instant red beans are obtained.

Description

Technical Field

[0001] The present invention relates to an instant adzuki bean with high integrity and excellent rehydration ability and a method for preparing the same. The present invention also relates to a food product containing the instant adzuki bean. Background Art

[0002] Adzuki bean is a highly nutritious cereal with high protein and low fat, and is often added to soups and porridges or used as a staple food. However, due to the structural composition of adzuki bean, it takes a long time to cook adzuki bean until it is cooked. With the changes in modern eating habits and lifestyles, speed and convenience have become one of the important considerations for consumers today. Therefore, researchers in the food-related field have tried to develop instant adzuki bean. Instant adzuki bean is mainly prepared by first cooking adzuki bean until it is cooked and then drying it. When consumers want to eat it, they only need to soak it in hot water and can eat it after it is rehydrated. However, commercially available instant adzuki beans all have the disadvantages of incomplete and broken adzuki bean particles and poor taste, and these disadvantages are mainly caused by the manufacturing process of instant adzuki bean. Therefore, how to prepare instant adzuki bean with complete particles and better taste is the research direction of this technical field.

[0003] Some prior arts have tried to use chemicals such as carbonates and bicarbonates for modification (for example, CN 1265283 A, CN 104822275 A). However, the use of such chemical treatments in the manufacturing process raises health concerns. On the other hand, some prior arts introduce an additional pressurization method (for example, CN 109527408A, CN 1068187C). However, additional pressurization in the manufacturing process has the problem of high energy consumption.

[0004] Therefore, there is still a need in this technology to develop a method for preparing instant adzuki bean with complete particles, better taste and no health concerns without pressurization to meet the needs of the industry. Summary of the Invention

[0005] Thus, in a first aspect, the present invention provides a method for preparing instant adzuki bean, which comprises the following steps:

[0006] Subjecting an adzuki bean to a pre-drying treatment, which comprises at least one of the following: freeze-drying treatment and superheated steam drying treatment;

[0007] Subjecting the adzuki bean subjected to the pre-drying treatment to a cooking treatment; and

[0008] Subjecting the adzuki bean subjected to the cooking treatment to a vacuum drying treatment and a hot air puffing treatment in sequence, thereby obtaining the instant adzuki bean.

[0009] In the method of the present invention, the pre-drying treatment is carried out so that the water content is reduced by 10 to 30%.

[0010] In the method of the present invention, the freeze-drying treatment includes a freezing treatment and a vacuum drying treatment carried out in sequence.

[0011] In the method of the present invention, the ripening treatment is carried out by at least one of the following: boiling, steaming, and baking.

[0012] In the method of the present invention, the vacuum drying treatment is carried out so that the water content is lower than 30 to 15%.

[0013] In the method of the present invention, the hot air puffing treatment is carried out until the bulk density is 0.60 to 0.96 g / mL.

[0014] In the method of the present invention, the hot air puffing treatment is carried out at a temperature of 200 to 550 °C and a wind speed of 30 to 90 m / s.

[0015] In a second aspect, the present invention provides an instant red bean which is prepared by the method as described above.

[0016] The instant red bean of the present invention has a integrity rate of 0.9 to 1.0 and a rehydration rate of 1.6 to 2.2.

[0017] The instant red bean of the present invention has a porosity of 0.3 to 0.5.

[0018] In a third aspect, the present invention provides a food product which contains the instant red bean as described above. Description of the Drawings

[0019] The above and other objects, features, and advantages of the present invention will become apparent after referring to the following detailed description, preferred embodiments, and the accompanying drawings, in which:

[0020] Figure 1 Showing the surface and internal structure of the red beans in the control group observed by scanning electron microscopy; and

[0021] Figure 2 Showing the surface and internal structure of the instant red beans in Experimental Group 1 observed by scanning electron microscopy. Detailed Description of the Invention

[0022] Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by those of ordinary skill in the art. Those of ordinary skill in the art will recognize many methods and materials similar or equivalent to those described herein, which can be used to implement the present invention. Of course, the present invention is in no way limited to the methods and materials described.

[0023] As used herein, the term "instant adzuki bean" means adzuki beans that can be rehydrated or reconstituted into an edible state by mixing with an aqueous liquid (e.g., water, milk, etc.) and optionally heating.

[0024] In order to prepare instant adzuki beans with complete granules and better taste, the applicant tried various pre-treatments before the ripening treatment of adzuki beans and various drying treatments after ripening, and found that: performing a pre-drying treatment before the ripening treatment and sequentially performing a vacuum drying treatment and a hot air puffing treatment after the ripening treatment can obtain instant adzuki beans with complete granules, better taste and aroma.

[0025] Thus, the present invention provides a method for preparing instant adzuki beans, which comprises the following steps:

[0026] Subjecting adzuki beans to a pre-drying treatment, which includes at least one of the following: freeze-drying treatment and superheated steam drying treatment;

[0027] Subjecting the pre-dried adzuki beans to a ripening treatment; and

[0028] Subjecting the ripened adzuki beans to a vacuum drying treatment and a hot air puffing treatment in sequence, thereby obtaining the instant adzuki beans.

[0029] The method according to the present invention is carried out using whole adzuki bean granules.

[0030] According to the present invention, the adzuki beans can be from various cultivars. Preferably, the cultivars of the adzuki beans can be selected from the group consisting of Kaohsiung No. 8, Kaohsiung No. 9, Kaohsiung No. 10, and combinations thereof. In a preferred embodiment of the present invention, the cultivar of the adzuki beans is Kaohsiung No. 9.

[0031] According to the present invention, before the pre-drying treatment, the adzuki beans can be blanched at 80 to 105 °C for 1 to 10 minutes to inactivate most of the enzymes in the adzuki beans.

[0032] According to the present invention, before the pre-drying treatment, the water content of red beans can be adjusted to a desired level, preferably 44 to 65%, more preferably 55 to 60%.

[0033] Preferably, the pre-drying treatment is carried out such that the water content is reduced by 10 to 30%, more preferably 10 to 15%, thereby generating cracks on the surface of the red beans.

[0034] In a preferred embodiment of the present invention, the pre-drying treatment is a freeze-drying treatment.

[0035] According to the present invention, the freeze-drying treatment includes a freezing treatment and a vacuum drying treatment carried out in sequence. According to the present invention, the freezing treatment and the vacuum drying treatment can be carried out using techniques well-known and commonly used by those skilled in the art. It can be understood that the operating conditions for the freezing treatment and the vacuum drying treatment will be further varied according to factors such as the quantity of red beans used and the water content, etc., in order to achieve the best freezing and drying effects. And the selection of these operating conditions can be routinely determined by those skilled in the art.

[0036] Preferably, the freezing treatment is carried out at -12 to -30°C for 1 to 12 hours.

[0037] Preferably, the vacuum drying treatment is carried out at 30 to 70°C and 0.1 to 100 Torr.

[0038] In another preferred embodiment of the present invention, the pre-drying treatment is a superheated steam drying treatment.

[0039] According to the present invention, the superheated steam drying treatment can be carried out using techniques well-known and commonly used by those skilled in the art. In this regard, reference can be made to, for example, Patent Publication No. TW M536331U. In a preferred embodiment of the present invention, the superheated steam drying treatment is carried out by using the superheated steam equipment disclosed in Patent Publication No. TW M536331U.

[0040] It can be understood that the operating conditions for the superheated steam drying treatment will be further varied according to factors such as the quantity of red beans used and the water content, etc., in order to achieve the best drying effect. And the selection of these operating conditions can be routinely determined by those skilled in the art.

[0041] Preferably, the superheated steam drying treatment is carried out using superheated steam at 120 to 180°C for 1 to 10 minutes.

[0042] According to the present invention, the ripening treatment can be carried out by techniques well-known and commonly used by those skilled in the art. Preferably, the ripening treatment is carried out by at least one of the following: boiling, steaming, and baking. In a preferred specific example of the present invention, the ripening treatment is steaming.

[0043] It can be understood that the operating conditions of the ripening treatment will be further varied according to factors such as the quantity of red beans used and the water content, etc., in order to achieve the best ripening effect. And the selection of these operating conditions can be routinely determined by those skilled in the art.

[0044] According to the present invention, the ripening treatment is carried out until it is fully cooked, or the birefringence of the starch granules completely disappears, that is, it is fully gelatinized.

[0045] According to the present invention, the vacuum drying treatment carried out on the ripened red beans can be carried out in the same or different ways as described above.

[0046] Preferably, the vacuum drying treatment is carried out at 30 to 70 °C and 0.1 to 100 Torr until the water content is lower than 30 to 15%, more preferably, lower than 20%.

[0047] According to the present invention, the term "hot-air puffing" can be used interchangeably with "thermal expansion".

[0048] According to the present invention, the hot-air puffing treatment can be carried out by techniques well-known and commonly used by those skilled in the art. In this regard, reference can be made to, for example, Patent Publication No. TW I626895 and TW M548447U. In a preferred specific example of the present invention, the hot-air puffing treatment is carried out by using the puffing heater disclosed in Patent Publication No. TW M548447U.

[0049] It can be understood that the operating conditions of the hot-air puffing treatment will be further varied according to factors such as the quantity of red beans used and the water content, etc., in order to achieve the best puffing and drying effect. And the selection of these operating conditions can be routinely determined by those skilled in the art.

[0050] Preferably, the hot-air puffing treatment is carried out at a temperature of 200 to 550 °C and a wind speed of 30 to 90 m / s.

[0051] More preferably, the hot-air puffing treatment is carried out until the bulk density is 0.60 to 0.96 g / mL.

[0052] The present invention provides an instant adzuki bean, which is prepared by the method as described above. Preferably, the instant adzuki bean has a solidity of 0.9 to 1.0 and a rehydration ratio of 1.6 to 2.2.

[0053] The present invention also provides an instant adzuki bean having a solidity of 0.9 to 1.0 and a rehydration ratio of 1.6 to 2.2.

[0054] Preferably, the instant adzuki bean has a porosity of 0.3 to 0.5.

[0055] According to the present invention, the instant adzuki bean can be rehydrated by existing means such as hot water and microwave-assisted heating for immediate consumption, or further formulated into a food product together with any edible material.

[0056] Therefore, the present invention provides a food product comprising the instant adzuki bean as described above.

[0057] According to the present invention, the food product may further comprise instant foods, including but not limited to: soluble drink powder, instant soup, instant noodle, instant cereal (such as instant rice), other instant beans, and prepared food.

[0058] <Example>

[0059] Example 1. Preparation of the instant adzuki bean of the present invention

[0060] General experimental materials:

[0061] 1. The adzuki bean (Vigna angularis) variety used in the following experiments is Kaohsiung No. 9, purchased from Wandan Township, Pingtung, Taiwan, China.

[0062] Experimental method:

[0063] First, wash the red beans and place them in water at 95 - 100 °C for 3 minutes for blanching, then transfer them to water at 25 °C for soaking until the water content reaches 55 - 60% [measured using a halogen lamp moisture rapid detector (MA100, Sartorius AG)]. Then divide them into 2 experimental groups (i.e., experimental group 1 and 2) and 7 comparative experimental groups (i.e., comparative experimental groups 1 to 7), with each group weighing 1 kg. After that, process the red beans in each group as shown in Table 1 below to prepare instant red beans.

[0064] Specifically, the processing of comparative experimental group 1 is carried out according to the steps shown below: First, place the red beans in boiling water at 100 °C for cooking until the red beans are completely cooked [judged by the complete disappearance of the birefringence of the starch granules]. After that, take out the cooked red beans (with a water content of about 55 - 60%) and spread them evenly on a stainless steel plate, and then dry them with hot air at 30 °C in a hot-air dryer (manufactured by Shengyang Industrial Factory) until the water content of the cooked red beans is less than 10%.

[0065] The processing of comparative experimental group 2 is generally carried out with reference to the steps of comparative experimental group 1 above, with the difference being that the cooking process is carried out by steaming in a steamer (brand Marupin) with the temperature set at 95 °C, and the drying process is carried out with hot air at 85 °C.

[0066] The processing of comparative experimental group 3 is generally carried out with reference to the steps of comparative experimental group 2 above, with the difference being that before the cooking process, the red beans are first subjected to the following freeze-drying treatment: freeze them at -18 °C for 4 hours to obtain frozen red beans. Then, use a rotary vacuum concentrator (R-2000V, Panqun Technology Co., Ltd.) to carry out reduced pressure drying at 60 °C and 60 Torr until the water content is reduced by about 15%.

[0067] The processing of comparative experimental group 4 is generally carried out with reference to the steps of comparative experimental group 3 above, with the difference being that the drying process after cooking is carried out with hot air at 85 °C and a radio frequency of 40.68 MHz with a hot air-assisted power of 5 kW in a hot air-assisted radiofrequency dryer (EDB-5D, Yida Biotechnology Co., Ltd.).

[0068] The processing of Comparative Experimental Group 5 was generally carried out with reference to the steps of Comparative Experimental Group 3 above. The difference lies in that the drying treatment after ripening was carried out with microwaves at a power of 600 W and a frequency of 2450 MHz in a microwave dryer (NN-ST651, Panasonic).

[0069] The processing of Comparative Experimental Group 6 was generally carried out with reference to the steps of Comparative Experimental Group 3 above. The difference lies in that the drying treatment after ripening was carried out with superheated vapor at 160 °C in a superheated vapor device (Patent Publication No. TW M536331U, Food Industry Research and Development Institute, a foundation).

[0070] The processing of Comparative Experimental Group 7 was generally carried out with reference to the steps of Comparative Experimental Group 3 above. The difference lies in that the drying treatment after ripening was carried out with reduced-pressure drying at 60 °C and 60 Torr in a rotary vacuum concentrator.

[0071] The processing of Experimental Group 1 was generally carried out with reference to the steps of Comparative Experimental Group 3 above. The difference lies in that the drying treatment after ripening was carried out as follows: First, reduced-pressure drying at 60 °C and 60 Torr in a rotary vacuum concentrator was carried out to make the water content about 20%. Then, hot-air puffing (also known as thermal puffing) at a temperature of 220 °C and a wind speed of 48 m / s was carried out in a pneumatic micro-expansion device (Patent Publication No. TW M548447U, Food Industry Research and Development Institute, a foundation) for 10 to 90 seconds (this method can shorten the traditional drying time by 30 - 60%).

[0072] The processing of Experimental Group 2 was generally carried out with reference to the steps of Experimental Group 1 above. The difference lies in that the pre-drying treatment was carried out with superheated vapor at 140 °C in a superheated vapor device until the water content was reduced by about 15%.

[0073] Table 1. Processing methods used in each group

[0074]

[0075] Example 2. Texture analysis of the instant red beans of the present invention

[0076] In this embodiment, the instant adzuki beans prepared in the above Embodiment 1 are subjected to the determination of bulk density, expansion ratio, complete grain ratio, and solidity to analyze the influence of processing on the expansion degree and integrity of instant adzuki beans. Then, the rehydration ratio of the rehydrated instant adzuki beans is determined and sensory evaluation is carried out to analyze the rehydration ability and rehydration status of instant adzuki beans. Finally, the structure of instant adzuki beans is analyzed by electron microscope observation and porosity determination.

[0077] In addition, for comparison, the unprocessed adzuki beans are used as the control group, and the commercially available instant adzuki beans (adzuki bean rice sold by Oniishi Foods) are used as the commercial group, and the same experiments are carried out together.

[0078] A. Determination of bulk density, expansion ratio, complete grain ratio, and solidity:

[0079] The determination of bulk density generally refers to the method described in the master's thesis written by Zhan Yiping of the Department of Food and Applied Biotechnology, National Chung Hsing University, Taiwan, China (2011) (Title: Using a processing model system - exploring the physicochemical properties and quality modification effects of instant rice and cereal powders) and is slightly modified. Briefly, each group of adzuki beans (10 g) is placed in a 500 mL graduated cylinder, and then 100 mL of table salt is added, and then the graduated cylinder is gently tapped until the height of the table salt in the graduated cylinder no longer changes, so as to calculate the bulk volume of each group of adzuki beans. The bulk density is calculated by substituting the total weight and total volume of each group into the following formula (I):

[0080] Formula (I): A = B / C

[0081] Where: A = bulk density (g / mL)

[0082] B = total weight of each group (g)

[0083] C = total volume of each group (mL)

[0084] The expansion ratio refers to Hoke K. et al. (2006), Journal of Food engineering, 80: 1016 - 1022, and is calculated by substituting the bulk density measured for each group into the following formula (II):

[0085] Formula (II): D = E / F

[0086] Where: D = expansion ratio

[0087] E = bulk density of the control group (g / mL)

[0088] F = bulk density of each group (g / mL)

[0089] The whole grain rate refers to the definition of "whole grain" in the "Verification Specification for Rice" and "National Standard of the People's Republic of China - Soybeans" of the Certified Agricultural Standards (CAS) in Taiwan, China. The cotyledons of adzuki beans in each group with a fragmentation degree less than 1 / 4 of the grain volume were selected as whole grains and weighed, and then substituted into the following formula (III) to be calculated:

[0090] Formula (III): G = H / I × 100 (%)

[0091] Where: G = whole grain rate (%)

[0092] H = total weight of whole grains in each group (g)

[0093] I = total weight of each group (g)

[0094] The bulk density, swelling ratio, and whole grain rate of each group are shown in Table 2 below.

[0095] Table 2. Bulk density, swelling ratio, and whole grain rate of each group

[0096] Group Bulk density (g / mL) Swelling ratio Intact grain rate (%) Control group 1.44±0.06 - - Comparison experimental group 1 0.83±0.08 1.73 87.3±1.9 Comparison experimental group 2 0.76±0.07 1.90 39.5±1.1 Comparison experimental group 3 1.01±0.00 1.43 95.2±1.4 Comparison experimental group 4 1.07±0.06 1.35 96.1±0.7 Comparison experimental group 5 0.99±0.03 1.45 97.8±0.3 Comparison experimental group 6 0.98±0.06 1.47 93.0±0.3 Comparison experimental group 7 1.03±0.02 1.40 97.4±0.4 Experimental group 1 0.90±0.06 1.60 94.0±1.5 Experimental group 2 0.88±0.06 1.64 93.8±1.3 Commercially available group 0.89±0.08 1.62 9.4±1.2

[0097] As can be seen from Table 2, the swelling ratios of Comparative Experimental Groups 1 to 7 and Experimental Groups 1 to 2 are all approximately equal to or higher than that of the commercial group, which means that: the swelling degree of adzuki beans after the above various different processing treatments can all reach approximately equal to or higher than that of commercial products. Among them, compared with Comparative Experimental Group 1, Comparative Experimental Group 2 has a slightly lower bulk density and a slightly higher swelling ratio, but a significantly lower whole grain rate (although still significantly higher than that of the commercial group), which means that: although steaming is easier than boiling to increase the swelling degree of adzuki beans, this cooking treatment seriously damages the integrity of adzuki beans instead. However, the whole grain rates of Comparative Experimental Groups 3 to 7 and Experimental Groups 1 to 2 are significantly higher than those of Comparative Experimental Group 2 and the commercial group. In addition, it can be observed that the cooking loss is reduced by 70 - 90%. This means that: the pre-drying treatment before the cooking treatment can effectively protect adzuki beans from the damage to integrity caused by the cooking treatment, and is significantly better than commercial products. In particular, only Experimental Groups 1 and 2 simultaneously have a high swelling ratio and a high whole grain rate, which means that: the pre-drying treatment combined with a specific post-cooking drying treatment can obtain more excellent effects.

[0098] In addition, to further verify the above results, the applicant referred to the method described in Matsumoto et al. (2015), Journal of Medical Ultrasonics, 42:505-512 to measure the integrity rate of the instant red beans in experimental group 1 and the commercial group. Briefly, a CCD auto-focus camera (USB3 XC, Imaging Development Systems, Germany) was used in combination with ImageJ imaging software (ImageJ Imaging Software, version 1.52) to measure the area and convex area of the instant red beans in experimental group 1 and the commercial group. The integrity rate was calculated by substituting the measured area and convex area of each group into the following formula (IV):

[0099] Formula (IV): J = K / L

[0100] Where: J = integrity rate

[0101] K = area of each group (mm 2 )

[0102] L = convex area of each group (mm 2 )

[0103] The results showed that the integrity rates of experimental group 1 and the commercial group were 0.97±0.03 and 0.66±0.11, respectively. Thus, it can be seen that the method according to the present invention can indeed enable instant red beans to still have significantly excellent integrity under a relatively high degree of swelling.

[0104] B. Determination of rehydration rate and sensory evaluation:

[0105] The determination of the rehydration rate was carried out with reference to the method described in Doymaz I. et al. (2015), Czech J. Food Sci., 33:367-376. Briefly, the instant red beans in the commercial group, comparative experimental groups 1 to 7, and experimental groups 1 to 2 were rehydrated with 95°C hot water for 20 minutes, and the weights before and after rehydration (i.e., dry weight and wet weight) were measured. The rehydration rate was calculated by substituting the measured dry weight and wet weight of each group into the following formula (V):

[0106] Formula (V): M = (O - N) / O

[0107] Where: M = rehydration rate

[0108] N = dry weight of each group (g)

[0109] O = wet weight of each group (g)

[0110] Sensory evaluation was carried out by panelists on the appearance, texture, and flavor of each group of instant red beans after rehydration.

[0111] The rehydration rates and sensory evaluation results of each group are shown in Table 3 below.

[0112] Table 3. Rehydration rates and sensory evaluation results of each group

[0113] Group Rehydration rate Sensory evaluation result Comparison experimental group 1 1.74±0.02 Particles broken, with soybean fragrance, and the taste is dense Comparison experimental group 2 2.23±0.01 Particles broken, without soybean fragrance, and the taste is dense Comparison experimental group 3 1.31±0.03 Particles intact, without soybean fragrance, and the taste is relatively hard Comparison experimental group 4 1.10±0.01 Particles intact, without soybean fragrance, and the taste is hard Comparison experimental group 5 1.26±0.04 Particles intact, without soybean fragrance, and the taste is hard Comparison experimental group 6 1.05±0.02 Particles intact, without soybean fragrance, and the taste is hard Comparison experimental group 7 1.35±0.02 Particles intact, with soybean fragrance, and the taste is relatively hard Experimental group 1 1.86±0.02 Particles intact, with soybean fragrance, and the taste is dense Experimental group 2 1.73±0.03 Particles intact, with soybean fragrance, and the taste is dense Commercially available group 2.16±0.04 Particles broken, without soybean fragrance, and the taste is mushy

[0114] As can be seen from Table 3, although the comparison experimental groups 1 and 2 without pre-drying treatment and the commercial group all had relatively high rehydration rates and were accompanied by a softer texture, they all had particle breakage after rehydration and had a poor appearance. In contrast, the comparison experimental groups 3 to 7 and experimental groups 1 to 2 with pre-drying treatment did not have such breakage, indicating that the pre-drying treatment before the ripening treatment can effectively avoid the breakage of rehydrated instant red beans. Furthermore, among the comparison experimental groups 3 to 7 and experimental groups 1 to 2, only experimental groups 1 to 2 had a rehydration rate similar to that of the commercial group, a softer texture, and at the same time retained the aroma of red beans. This indicates that the pre-drying treatment combined with a specific post-ripening drying treatment can achieve more excellent effects.

[0115] In addition, in order to further verify the above results, the applicant generally carried out rehydration rate determination and sensory evaluation on the instant red beans of experimental group 1 according to the above method, with the difference that the rehydration method was changed to placing the instant red beans in water at 95 °C and then performing microwave heating at a power of 600 W for 5 minutes. The results showed that the measured rehydration rate was 2.12 ± 0.02, and the result of the sensory evaluation was that the particles were intact, had a bean fragrance, and had a dense texture. Thus, it can be seen that the method according to the present invention can indeed make the instant red beans have excellent rehydration ability and have good appearance, texture, and flavor after rehydration, and it will not be affected even when different rehydration methods are used.

[0116] C. Electron microscope analysis and determination of porosity:

[0117] The red bean structures of experimental group 1 and the control group were observed by a scanning electron microscope (Hitachi 4700) at a magnification of 20 times.

[0118] Figure 1 and Figure 2 respectively show the outer surface and internal structure of the red beans in the control group and experimental group 1. From Figure 1 and Figure 2It can be seen that the outer surface of the red beans in the control group is relatively smooth, while the internal structure is relatively compact and complete. In contrast, the outer surface of the instant red beans in Experimental Group 1 has many fine cracks, and the internal structure shows a porous shape, and there are gaps between the cotyledons and the seed coat. Based on this, the applicant believes that: due to the cracks on the surface and the porous internal structure of the instant red beans of the present invention, it is beneficial for liquid to enter the red bean particles during rehydration, thereby improving the rehydration efficiency and resulting in a relatively dense texture.

[0119] In addition, in order to further verify the above inference, the applicant referred to the method described in Koua et al. (2019), Journal of the Saudi Society of Agricultural Sciences, 18: 72-82 to measure the porosity of the instant red beans in Comparative Experimental Groups 3 to 7 and Experimental Groups 1 to 2. Briefly, 10 g of the control group red beans were placed in a 500 mL graduated cylinder, and then 100 mL of pure water was added to estimate the total volume of the control group red beans and calculate the true density accordingly. The porosity was calculated by substituting the true density of the control group red beans and the bulk density of the instant red beans in Comparative Experimental Groups 3 to 7 and Experimental Groups 1 to 2 measured in item A above into the following formula (VI):

[0120] Formula (VI): P = (R - Q) / R

[0121] Where: P = porosity

[0122] Q = bulk density of each group (g / mL)

[0123] R = true density of the control group (g / mL)

[0124] The porosity results of Comparative Experimental Groups 3 to 7 and Experimental Groups 1 to 2 are shown in Table 4 below.

[0125] Table 4. Porosity of each group

[0126] Group Porosity Comparison experimental group 3 0.29 Comparison experimental group 4 0.25 Comparison experimental group 5 0.30 Comparison experimental group 6 0.31 Comparison experimental group 7 0.28 Experimental group 1 0.37 Experimental group 2 0.38

[0127] As can be seen from Table 4, Experimental Groups 1 to 2 have significantly higher porosity compared to Comparative Experimental Groups 3 to 7. Thus, it can be seen that according to the method of the present invention, the instant red beans can indeed have more tiny pores and cracks without destroying the integrity of the structure.

[0128] Based on the above experimental results, the applicant believes that: according to the method of the present invention, the red beans can produce a special structure different from the prior art, with both high integrity and high porosity, and have excellent rehydration ability, thereby resulting in excellent sensory properties.

[0129] All patents and documents cited in this specification are incorporated herein by reference in their entirety. In case of any conflict, the detailed description of this application (including definitions) shall prevail.

[0130] Although the present invention has been described with reference to the above specific examples, it is obvious that many modifications and variations can be made without departing from the scope and spirit of the present invention. Therefore, it is intended that the present invention be limited only by what is shown in the appended claims.

Claims

1. A method for preparing instant red beans, characterized in that: The method comprises the following steps: Subjecting the red beans to pre-drying treatment, which includes at least one of the following: freeze-drying treatment and superheated steam drying treatment. The pre-drying treatment is carried out to reduce the water content by 10 to 30%. The freeze-drying treatment includes a freezing treatment and a vacuum drying treatment carried out in sequence. The freezing treatment is carried out at -12 to -30 °C for 1 to 12 hours, and the vacuum drying treatment is carried out at 30 to 70 °C and 0.1 to 100 Torr. The superheated steam drying treatment is carried out using superheated steam at 120 to 180 °C for 1 to 10 minutes; Subjecting the pre-dried red beans to a ripening treatment; and Subjecting the ripened red beans to a vacuum drying treatment and a hot air puffing treatment in sequence, thereby obtaining the instant red beans. The hot air puffing treatment is carried out at a temperature of 200 to 550 °C and a wind speed of 30 to 90 m / s until the bulk density is 0.60 to 0.96 g / mL.

2. The method according to claim 1, wherein: The ripening treatment is carried out by at least one of the following: boiling, steaming, and baking.

3. The method according to claim 1, wherein: The vacuum drying treatment after the ripening treatment is carried out to make the water content lower than 30 to 15%.

4. An instant red bean, characterized in that: The instant red beans are prepared by the method according to any one of claims 1 to 3.

5. The instant red beans according to claim 4, characterized in that: The instant red beans have a integrity rate of 0.9 to 1.0 and a rehydration rate of 1.6 to 2.

2.

6. The instant red beans according to claim 4, wherein: The instant red beans have a porosity of 0.3 to 0.

5.

7. A food product, characterized in that: The food product contains the instant red beans according to any one of claims 4 to 6.

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