Method for improving procyanidine content of germinated red rice by utilizing composite stress treatment

Abstract

The invention discloses a composite stress germination treatment method for increasing the content of procyanidine in red rice, which comprises the processes of salt stress germination treatment and ambient temperature stress germination treatment, and the total time of the stress germination treatment is 12-36 hours; the salt stress germination treatment process comprises the following steps: spraying a NaCl solution with the concentration of 30-120mmol / L, and then carrying out stress treatment for 6-24 hours; the process of the environment temperature stress germination treatment is that treatment is performed in a low-temperature environment at the temperature of 8-18 DEG C for 6-12 hours. The treatment conditions can effectively control the germination state of the red rice grains, the hardness of the red rice grains can be effectively reduced, the eating taste can be improved, and the high active ingredient content can be kept; the problem of poor eating quality of the red rice at present can be solved, and enrichment and improvement of the content of the characteristic active ingredient procyanidine in the red rice are realized.

Description

Technical Field

[0001] The invention relates to the technical field of grain processing, in particular to a method for increasing the proanthocyanidin content of germinated red rice by utilizing composite stress. Background Art

[0002] Red rice is a plant of the genus Oryza in the Poaceae family. Its husk is yellow or brown. After removing the husk, the seed coat is red and the shape is long-grain brown rice. The varieties are mainly indica sticky rice, so it is also called red rice. The protein content in red rice is 1.57 times that of ordinary rice, and the total amount of essential amino acids is 58.31% higher than that of ordinary rice. Red rice contains a variety of mineral elements needed by the human body. In addition, red rice also contains a large amount of biologically active substances, such as phenolic acid, flavonoids, γ-aminobutyric acid and oryzanol, especially active pigment components such as proanthocyanidins, which give red rice a red seed coat.

[0003] Proanthocyanidins, also known as condensed tannins, are compounds polymerized from flavan-3-ol monomers. Proanthocyanidins are widely distributed in the plant kingdom and are commonly found in fruits, vegetables, and colored grains. A large number of studies have shown that proanthocyanidins are a natural antioxidant that participates in a variety of metabolic activities and has good physiological functions. It can not only reduce the damage of excessive free radicals to cells, inhibit the spread and proliferation of cancer cells, but also has a good anti-inflammatory effect, can effectively reduce the risk of cardiovascular diseases, and help prevent and treat diabetes.

[0004] Since the content of proanthocyanidins in natural plant tissues cannot meet the needs of the human body. To solve this problem, red rice can be germinated to enrich proanthocyanidins. This is because the germination process of grains will produce a variety of physiological changes, which can soften the grain structure, improve the grain texture quality, and improve the nutritional quality of grains. Most of the traditional preparations of germinated grains use water soaking methods to allow the grains to absorb water and germinate in a high-moisture environment. However, the above preparation technologies generally have problems such as long germination cycles, unsatisfactory effects on improving edible quality and enriching active substances. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a method for increasing the content of proanthocyanidins in germinated red rice by using compound stress treatment. The treatment conditions of the present invention can effectively control the germination state of red rice grains, effectively reduce the hardness of red rice grains, improve the edible taste, and maintain a high content of active ingredients; it can solve the current problem of poor edible quality of red rice, and achieve the enrichment and improvement of the content of proanthocyanidins, a characteristic active ingredient in red rice.

[0006] The technical solution of the present invention is as follows:

[0007] The object of the present invention is to provide a composite stress germination treatment method for increasing the proanthocyanidin content of red rice, comprising the processes of salt stress germination treatment and ambient temperature stress germination treatment, wherein the total duration of the stress germination treatment is 12-36 hours;

[0008] The process of salt stress germination treatment is to spray with 30-120mmol / L NaCl solution and then treat for 6-24h;

[0009] The process of environmental temperature stress germination treatment is to treat the seeds in a low temperature environment of 8-18°C for 6-12 hours.

[0010] In one embodiment of the present invention, the combined stress germination treatment method specifically comprises the following steps:

[0011] (1) Raw material selection: Select whole red rice grains with full grains, uniform size, and no damage or insect infestation as raw materials;

[0012] (2) Cleaning and sterilizing: removing impurities from the red rice grains, rinsing with distilled water 1-2 times, and sterilizing the red rice grains;

[0013] (3) Soaking treatment: Rinse the sterilized red rice grains with distilled water for 5-8 times until the pH of the red rice grains is neutral, and soak them in distilled water;

[0014] (4) Pre-germination: drain the water and evenly place the soaked red rice grains in an open container for pre-germination;

[0015] (5) Stress treatment: The pre-germinated red rice grains were evenly placed in an open container, and then sprayed with a 30-120 mmol / L NaCl solution for 6-24 h in a constant temperature and humidity environment. After that, the grains were washed and placed in a low temperature environment of 8-18 °C for 6-12 h.

[0016] In one embodiment of the present invention, in step (2), the sterilization method is: soaking the red rice grains in 0.1% (g / L) sodium hypochlorite solution for 10-15 minutes.

[0017] In one embodiment of the present invention, the mass ratio of red rice grains to sodium hypochlorite solution is 10:8-13.

[0018] In one embodiment of the present invention, in step (3), the soaking conditions are: soaking at room temperature for 8-14 hours.

[0019] In one embodiment of the present invention, in step (4), the pre-germination time is 8-16 hours, the temperature is 20-30° C., and the humidity is 60-80%.

[0020] In one embodiment of the present invention, in step (4), the pre-germination is sprayed with distilled water.

[0021] In one embodiment of the present invention, in step (4), the open container is a culture dish lined with clean gauze, so that the seeds can be evenly distributed and the growth of the buds can be prevented from being affected by overlapping seeds.

[0022] In one embodiment of the present invention, in step (5), the stress treatment is to culture the red rice grains in an incubator with lighting and temperature control functions.

[0023] In one embodiment of the present invention, the temperature of the constant temperature and humidity environment is 20-30° C., and the humidity is 75-85%.

[0024] In one embodiment of the present invention, in step (5), the mass of the sprayed NaCl solution is 0.9-1 times the mass of the red rice grains.

[0025] In one embodiment of the present invention, red rice can be replaced by black rice or purple rice.

[0026] Under the stress treatment conditions of the present invention, the sprout length of red rice can be controlled not to exceed the grain length, which can effectively reduce the hardness of the red rice grains, improve the edible taste, and maintain a high content of active ingredients.

[0027] The beneficial technical effects of the present invention are:

[0028] The present invention promotes the germination of red rice by combining the continuous stress effects of salt stress and low temperature stress, thereby promoting the increase of the proanthocyanidin content of the red rice, thereby increasing the proanthocyanidin content in the red rice from 1.46±0.06 mg / g to 3.08±0.05 mg / g, and improving the texture characteristics of the red rice, wherein the hardness decreases by 34.29-45.84%.

[0029] The red rice germination method of the invention is simple, easy, safe and reliable. The harvested germinated red rice grains can be directly cooked and eaten, and the edible quality is better than that of ungerminated red brown rice. The red rice grains can also be used to make germinated red rice flour and other functional food ingredients, and have good effects on consumers' diet therapy and health care. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a physical picture of red rice before and after stress treatment in Example 1. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0032] In the embodiment of the present invention, whole red rice grains with full grains, uniform size, and no damage or worm-eaten grains are selected as raw materials; impurities mixed in the red rice grains are removed, and the red rice grains are rinsed with distilled water for 1-2 times for standby use.

[0033] Test Method

[0034] 1. Determination of proanthocyanidin content: Mix 2.0 g sample powder with 20 mL 80% acidified methanol, extract the mixture in an oscillator (300 r / min) at room temperature for 6 h, and then centrifuge to obtain the supernatant. Mix 0.4 mL of the extract with 1 mL 1% vanillin methanol solution (w / v) and 1 mL 8% sulfuric acid / methanol solution (v / v), and use anhydrous methanol as a control to eliminate the interference caused by active anthocyanins or vanillin compounds. Incubate the mixture at 30°C for 15 min, and then measure the absorbance of the sample and control mixture at 510 nm. The total proanthocyanidin content is expressed as mg catechin equivalent per g sample dry weight (mg CE / g DW).

[0035] 2. Edible texture quality determination method: Weigh 5g (accurate to 0.01g) sample, put it into a clean aluminum crucible with a volume of 10mL, add pure water at a material-water ratio of 1:1.6 (w / v) and seal it with a lid. Add an appropriate amount of pure water to the electric steamer, adjust the mode to the cooking gear, and after the water boils, place the aluminum crucible on the steaming grid of the electric steamer. After waiting for the steaming time to be reached, take out the aluminum crucible, and cool the cooked rice at room temperature for 20min for standby. The texture quality of red rice was analyzed by a physical property analyzer (TPA). The texture analyzer test probe was P36R, and the secondary compression mode was performed. The specific parameters are as follows: the pre-measurement speed is 1mm / s, the test speed is 0.5mm / s, and the post-measurement speed is 1mm / s; the trigger force is 5.0g, and the two-time compression ratio is 70%. The 3-grain rice method is used, and each sample is measured 10 times in parallel, and the maximum and minimum measurement values ​​are discarded.

[0036] Example 1

[0037] A composite stress germination treatment method for increasing the proanthocyanidin content of red rice comprises the following steps:

[0038] (1) Red rice grains were soaked in 0.1% (g / L) sodium hypochlorite solution for 10 min, washed with distilled water until the pH of the red rice grains was neutral, and then soaked in 30°C distilled water for 12 h to allow the grains to fully absorb water.

[0039] (2) Afterwards, the water was drained and the soaked red rice grains were evenly spread on a culture dish lined with clean gauze, placed in an automatic germination machine with an automatic water spraying function, and placed in a dark environment at 25° C. and sprayed with distilled water for 12 h for pre-germination.

[0040] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After drainage, the germinated red rice samples were spread on a culture dish lined with four layers of gauze, and first sprayed with a 60 mmol / L NaCl solution prepared with distilled water (the mass of the sprayed NaCl solution was equal to the wet weight of the red rice grains). The culture dish was placed in a dark environment at 25°C for salt stress for 24 hours; the samples were washed and drained, spread on a culture dish lined with four layers of gauze, placed in a dark environment at 13°C for 12 hours, and sprayed with distilled water for low temperature stress. After the low temperature stress treatment, the germinated red rice samples were dried and the proanthocyanidin content therein was determined.

[0041] The results showed that after germination under the above conditions, the proanthocyanidins content of red rice reached 3.08±0.05 mg / g.

[0042] Example 2

[0043] A composite stress germination treatment method for increasing the proanthocyanidin content of red rice comprises the following steps:

[0044] (1)-(2) Same as Example 1;

[0045] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After drainage, the germinated red rice samples were spread flat in a culture dish lined with four layers of gauze, first sprayed with a 60 mmol / L NaCl solution prepared with distilled water (the mass of the sprayed NaCl solution was equal to the wet weight of the red rice grains), and the culture dish was placed in a dark environment at 25°C for salt stress for 24 hours; the samples were washed and drained, spread flat in a culture dish lined with four layers of gauze, placed in a dark environment at 13°C for 8 hours, and sprayed with distilled water for low temperature stress. After the low temperature stress treatment, the germinated red rice samples were dried and the proanthocyanidin content therein was determined.

[0046] The results showed that after germination under the above conditions, the proanthocyanidin content of red rice reached 2.86±0.05 mg / g.

[0047] Example 3

[0048] A composite stress germination treatment method for increasing the proanthocyanidin content of red rice comprises the following steps:

[0049] (1)-(2) Same as Example 1;

[0050] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After drainage, the germinated red rice samples were spread flat in a culture dish lined with four layers of gauze, first sprayed with a 60 mmol / L NaCl solution prepared with distilled water (the mass of the sprayed NaCl solution was equal to the wet weight of the red rice grains), and the culture dish was placed in a dark environment at 25°C for salt stress for 24 hours; the samples were washed and drained, spread flat in a culture dish lined with four layers of gauze, placed in a dark environment at 10°C for 12 hours, and sprayed with distilled water for low temperature stress. After the low temperature stress treatment, the germinated red rice samples were dried and the proanthocyanidin content therein was determined.

[0051] The results showed that after germination under the above conditions, the proanthocyanidin content of red rice reached 2.94±0.04 mg / g.

[0052] Example 4

[0053] A composite stress germination treatment method for increasing the proanthocyanidin content of red rice comprises the following steps:

[0054] (1)-(2) Same as Example 1;

[0055] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After drainage, the germinated red rice samples were spread on a culture dish lined with four layers of gauze, and first sprayed with a 60 mmol / L NaCl solution prepared with distilled water (the mass of the sprayed NaCl solution was equal to the wet weight of the red rice grains). The culture dish was placed in a dark environment at 25°C for salt stress for 24 hours; the samples were washed and drained, spread on a culture dish lined with four layers of gauze, placed in a dark environment at 15°C for 12 hours, and sprayed with distilled water for low temperature stress. After the low temperature stress treatment, the germinated red rice samples were dried and the proanthocyanidin content therein was determined.

[0056] The results showed that after germination under the above conditions, the proanthocyanidins content of red rice reached 2.84±0.08 mg / g.

[0057] Comparative Example 1

[0058] The red rice was sterilized with 0.1% (g / L) sodium hypochlorite solution for 10 minutes, the red rice grains were washed and dried, and the proanthocyanidin content in the ungerminated red rice grains was determined. The results showed that the proanthocyanidin content in the ungerminated red rice grains was 1.46±0.06 mg / g.

[0059] Comparative Example 2

[0060] (1)-(2) Same as Example 1;

[0061] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After drainage, the germinated red rice samples were spread flat on a culture dish lined with four layers of gauze and sprayed with distilled water. The culture dish was placed in a dark environment at 25°C for germination for 12 hours. After the treatment, the germinated red rice samples were dried and the proanthocyanidin content was determined.

[0062] The results showed that after germination for 24 hours under the above conditions, the proanthocyanidin content of red rice was 2.29±0.21 mg / g. After germination for more than 48 hours, the sprout length exceeded the grain length, and mold and fermentation odor were prone to occur.

[0063] Comparative Example 3

[0064] (1)-(2) Same as Example 1;

[0065] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After drainage, the germinated red rice samples were spread flat on a culture dish lined with four layers of gauze and sprayed with distilled water. The culture dish was placed in a dark environment at 25°C for germination for 24 hours. After the treatment, the germinated red rice samples were dried and the proanthocyanidin content was determined.

[0066] The results showed that the content of proanthocyanidins in red rice was 2.40±0.11 mg / g after germination for 36 hours under the above conditions. When the total germination time exceeded 48 hours, the sprout length exceeded the grain length, and it was easy to grow mold and fermentation odor.

[0067] Comparative Example 4

[0068] (1) Same as Example 1;

[0069] (2) Afterwards, drain the water, spread the soaked red rice grains evenly on a petri dish lined with clean gauze, put them into an automatic germination machine with an automatic water spraying function, place them in a dark environment at 30° C. and spray them with distilled water for 12 h for pre-germination;

[0070] (3) Subsequently, the pre-germinated red rice grains were washed with distilled water and drained. After draining, the germinated red rice samples were spread flat in a petri dish lined with four layers of gauze, sprayed with distilled water, and placed in a dark environment at 30°C for germination for 36 hours. The results showed that after a total germination time of 48 hours under the above conditions, the sprout length of the germinated red rice grains exceeded the grain length itself, and the grains cracked, became soft and rotten, and grew mold, accompanied by a fermented odor.

[0071] Comparative Example 5

[0072] (1) Same as Example 1;

[0073] (2) Afterwards, the water was drained, and the soaked red rice grains were evenly spread on a petri dish lined with clean gauze, placed in an automatic germination machine with an automatic water spraying function, and placed in a dark environment at 30°C and sprayed with 60 mmol / L NaCl solution for 48 h to directly carry out salt stress treatment;

[0074] (3) Subsequently, the germinated red rice grains were washed with distilled water and drained, and the germinated red rice samples were dried and the proanthocyanidin content was determined.

[0075] The results showed that after 48 hours of salt stress treatment without pre-germination, the proanthocyanidins in the germinated red rice were 2.16±0.01 mg / g. The red rice grains did not grow mold or have any odor, but the metabolism rate of germinated red rice was faster under high temperature, and the content of proanthocyanidins was not high.

[0076] The edible texture quality of the composite stress red rice of Examples 1 to 4 and the untreated red rice was tested using a physical property analyzer. The edible texture quality test results of the red rice are shown in Table 1 below:

[0077] Table 1

[0078]

[0079] It can be seen from Table 1 that after germination stress treatment, the hardness, chewiness and adhesiveness of red rice decreased, and the changes in adhesion and elasticity were irregular and small; and compared with the single salt stress treatment, it was found that the composite stress treatment further improved the texture quality of red rice, especially the hardness index of red rice changed significantly.

[0080] The embodiments provided above are only preferred embodiments of the present invention and should not be regarded as limiting the scope and concept of the present invention, nor are they used to limit the execution order thereof. Those skilled in the art may make obvious improvements to the steps described in the present invention in combination with existing common knowledge, or make equivalent replacements and improvements to different colored rice varieties such as red rice, purple rice, and black rice, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A composite stress germination treatment method for increasing the proanthocyanidin content of red rice, characterized in that: It includes the process of salt stress germination treatment and ambient temperature stress germination treatment, and the total duration of stress germination treatment is 12-36h; The process of salt stress germination treatment is to spray with 30-120mmol / L NaCl solution and then treat for 6-24h; The process of environmental temperature stress germination treatment is to treat the seeds in a low temperature environment of 8-18°C for 6-12 hours.

2. The combined stress germination treatment method according to claim 1, characterized in that: The specific steps include: (1) Raw material selection: Select whole red rice grains with full grains, uniform size, and no damage or insect infestation as raw materials; (2) Cleaning and sterilizing: removing impurities from the red rice grains, rinsing with distilled water 1-2 times, and sterilizing the red rice grains; (3) Soaking treatment: Rinse the sterilized red rice grains with distilled water for 5-8 times until the pH of the red rice grains is neutral, and soak them in distilled water; (4) Pre-germination: drain the water and evenly place the soaked red rice grains in an open container for pre-germination; (5) Stress treatment: The pre-germinated red rice grains were evenly placed in an open container, and sprayed with a 30-120 mmol / L NaCl solution in a constant temperature and humidity environment, and then subjected to stress treatment for 6-24 h. After washing, the grains were placed in a low temperature environment of 8-18 °C for 6-12 h.

3. The combined stress germination treatment method according to claim 2, characterized in that: In step (2), the sterilization method is: soaking the red rice grains in 0.1% sodium hypochlorite solution for 10-15 minutes.

4. The combined stress germination treatment method according to claim 3, characterized in that: The mass ratio of red rice grains to sodium hypochlorite solution is 10:8-13.

5. The combined stress germination treatment method according to claim 2, characterized in that: In step (3), the soaking conditions are: soaking at room temperature for 8-14 hours.

6. The combined stress germination treatment method according to claim 2, characterized in that: In step (4), the pre-germination time is 8-16 hours, the temperature is 20-30° C., and the humidity is 60-80%.

7. The combined stress germination treatment method according to claim 2, characterized in that: In step (4), the open container is a culture dish lined with clean gauze.

8. The combined stress germination treatment method according to claim 2, characterized in that: In step (5), the stress treatment is to culture the red rice grains in an incubator with lighting and temperature control functions.

9. The combined stress germination treatment method according to claim 2, characterized in that: The temperature of the constant temperature and humidity environment is 20-30℃, and the humidity is 75-85%.

10. The combined stress germination treatment method according to claim 2, characterized in that: In step (5), the mass of the sprayed NaCl solution is 0.9-1 times the mass of the red rice grains.

Images