阅读说明：本技术 一种紫米方便米饭及其制备方法 (Purple rice instant rice and preparation method thereof ) 是由 陈佩 黄燕霞 黄苇 郑经绍 于 2021-08-13 设计创作，主要内容包括：本发明提供了一种紫米方便米饭及其制备方法。本发明针对紫米原料的特殊性,通过采用特定的蒸煮液蒸煮紫米,再进行滚筒干燥结合热风干燥的技术进行干燥,解决了紫米方便米饭普遍存在的口感不好、复水性差,米粒发硬、夹生等问题,可有效降低紫米淀粉的老化程度,避免紫米饭脱水时的结块,米饭颗粒饱满,较好的复原米饭的颗粒形态,改善紫米粒的外观品质,有效地保留了紫米中的花青素以及风味香气,提高复水后紫米饭的口感和营养价值。(The invention provides instant purple rice and a preparation method thereof. According to the invention, aiming at the particularity of the raw material of the purple rice, the purple rice is cooked by adopting specific cooking liquor, and then the drying is carried out by combining the roller drying and hot air drying technologies, so that the problems of poor taste, poor rehydration property, hard rice grains, half-cooked rice and the like of the instant rice with the purple rice are solved, the aging degree of the starch of the purple rice can be effectively reduced, the agglomeration of the rice during dehydration is avoided, the rice grains are full, the grain shape of the rice is well restored, the appearance quality of the purple rice grains is improved, the anthocyanin and the flavor and aroma in the purple rice are effectively reserved, and the taste and the nutritional value of the rehydrated purple rice are improved.)

1. The preparation method of the purple rice instant rice is characterized by comprising the following steps:

s1, soaking purple rice in warm water for 45-60 min;

s2, preparing a cooking solution containing 0.1-1% of sucrose fatty acid ester, 0.1-1% of isolated soy protein, 0.3-1% of locust bean gum and 0.05-0.5% of beta-cyclodextrin;

s3, adding the cooking liquor obtained in the step S2 into the purple rice soaked in the step S1, and cooking for 15-20 min, wherein the mass ratio of the purple rice to the cooking liquor is 1: 1;

s4, scattering the cooked purple rice, and showering with warm water;

s5, drying the showered purple rice in a roller for 40-50 min at 100-110 ℃, and then, drying in a blast manner for 20-30 min at 60-70 ℃;

and S6, cooling and packaging the dried purple rice to obtain the instant purple rice.

2. The method as claimed in claim 1, wherein the soaking in step S1 is carried out until the water content of purple rice is 30-35%.

3. The method of claim 1, wherein the purple rice is washed with cold water before step S1.

4. The method as claimed in claim 1, wherein the cooking solution of step S2 is prepared by: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 5-15 min at the rotating speed of 10000-12000/min in an ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and uniformly mixing to obtain the cooking liquor.

5. The method as claimed in claim 1, wherein the soaked purple rice of step S3 is drained purple rice after soaking.

6. The method of claim 1, wherein step S5 is followed by the step of using a scattering machine to scatter the stuck rice kernels and using a vibrating screen to separate the crumbs from the rice kernels.

7. The method as claimed in claim 1, wherein the water content of the dried purple rice of step S5 is less than 10%.

8. The method of claim 1, wherein the breaking up in step S4 is performed by a deblocking machine.

9. The method of claim 1, wherein the cooking of step S3 is steam cooking.

10. The instant rice of purple rice prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the field of food processing. More particularly, relates to purple rice instant rice and a preparation method thereof.

Background

With the rapid development of social economy, the pace of life of people is continuously accelerated, and the market demand for instant food is continuously increased. In the instant food, the instant rice has the characteristic of convenience, can meet the nutritional requirements and dietary habits of people, is popular among people, and has very wide market prospect. In the period of 'two war', the European and American countries developed instant rice as military food, and the research on the instant rice is not carried out until 90 years in China, and the instant rice includes products such as aseptic packaged rice, frozen rice and self-heating rice. However, most of the conventional self-heating rice is made of rice as main raw material, such as the patents CN201110230991.9, CN201310386884.4, and CN201410053700.7, but the nutrition of self-heating rice is single.

The purple rice is also called purple pearl, the rice grains are thin and purple black, compared with common white rice, the purple rice is rich in mineral substances and vitamins, the skin of the purple rice is also rich in anthocyanin, and the purple rice can emit unique faint scent after being steamed and boiled, so that the purple rice is more and more favored by consumers. However, related products and researches of the purple rice instant rice are not available at present, due to the particularity of the raw materials of the purple rice, the difficulty needed to overcome when the purple rice is prepared is more, and the preparation method of the common white rice instant rice is not suitable for preparing the purple rice instant rice and mainly comprises the following reasons: (1) the purple rice is rich in a large amount of anthocyanin, so that the anthocyanin is easily lost to a large extent in the processes of cooking and drying, and the flavor of the purple rice is lost and changed after the purple rice is rehydrated; (2) purple rice belongs to brown rice, and has poor rehydration after being prepared into convenient rice, hard and half-cooked rice grains after rehydration, and seriously reduced taste and quality.

Therefore, there is a need for the development of instant purple rice which can effectively maintain the flavor components of purple rice and improve the rehydration and mouthfeel.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, fills the blank of preparing the instant rice by using the purple rice and aims to provide the instant rice with the purple rice and the preparation method thereof. According to the instant purple rice, through a specific steaming and drying dehydration scheme, the aging degree of the starch of the purple rice can be effectively reduced, the agglomeration of the purple rice during dehydration is avoided, the appearance quality of the purple rice is improved, anthocyanin and flavor fragrance in the purple rice are retained to a greater extent, and the sensory and nutritional values of the rehydrated purple rice are improved.

The invention aims to provide a preparation method of purple rice instant rice.

The invention also aims to provide the instant purple rice prepared by the method.

The above purpose of the invention is realized by the following technical scheme:

the invention provides a preparation method of purple rice instant rice, which comprises the following steps:

s1, soaking purple rice in warm water for 45-60 min;

s2, preparing a cooking solution containing 0.1-1% of sucrose fatty acid ester, 0.1-1% of isolated soy protein, 0.3-1% of locust bean gum and 0.05-0.5% of beta-cyclodextrin;

s3, adding the cooking liquor obtained in the step S2 into the purple rice soaked in the step S1, and cooking for 15-20 min, wherein the mass ratio of the purple rice to the cooking liquor is 1: 1;

s4, scattering the cooked purple rice, and showering with warm water;

s5, drying the showered purple rice in a roller for 40-50 min at 100-110 ℃, and then, drying in a blast manner for 20-30 min at 60-70 ℃;

and S6, cooling and packaging the dried purple rice to obtain the instant purple rice.

Due to the particularity of the raw materials of the purple rice, the flavor and the taste quality of the purple rice instant rice can not be improved only according to the related technical inspiration summarized in the technical field and suitable for the preparation of other types of instant rice. Through targeted research and a large number of experimental summaries, the invention adopts cooking liquor prepared from sucrose fatty acid ester, soybean protein isolate, locust bean gum and beta-cyclodextrin to cook purple rice together, and then adopts roller drying and hot air drying technology, so that the flavor quality of purple rice can be better kept, the aging degree of purple rice starch is reduced, the agglomeration of rice during dehydration is effectively avoided, the appearance form of rice grains is improved, and the rehydration performance of purple rice and the sensory quality of rehydrated rice are improved.

The sucrose fatty acid ester and the soybean protein isolate added into the cooking liquid are beneficial to delaying the aging of starch during the storage period of the purple rice and improving the taste of the rice after rehydration; locust bean gum and beta-cyclodextrin are added into the cooking liquor, so that the synergistic effect of keeping the fragrance of the purple rice can be achieved; besides, the locust bean gum is a hydrophilic colloid, and can influence the gelatinization of the purple rice starch and delay the aging of the purple rice starch through free water in a starch competition system in the gelatinization process of the starch, so that the mouthfeel of the rehydrated purple rice is improved.

The invention adopts the technology of combining roller drying and hot air drying, better shortens the dehydration time of the rice, reduces the water content of the rice as soon as possible, delays the aging degree of the purple rice, reduces the hardness of the rice after rehydration, and improves the taste. The rice is dehydrated in the early stage of drying by adopting a roller drying mode, the rice is expanded again in a high-temperature environment, and more holes can be generated after the rice grains are dehydrated, so that the rehydration rate of the rice is improved, and the rehydration time is shortened; the rice is dried by rolling, so that the rice grains can be effectively separated, the problem of adhesion among the rice grains is solved, and the particle shape of the rice is well restored; and the high-temperature drying can quickly fix the alpha state of the starch of the cooked purple rice and prevent the starch from retrogradation.

Preferably, the soaking in the step S1 is to soak the purple rice until the moisture content of the purple rice is 30% -35%.

Preferably, the purple rice is washed with cold water before step S1. Because the skin of the purple rice is rich in water-soluble anthocyanin, kneading is not needed during washing.

Preferably, the preparation method of the cooking liquor in the step S2 is as follows: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 5-15 min at the rotating speed of 10000-12000/min in an ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and uniformly mixing to obtain the cooking liquor.

Preferably, the soaked purple rice of the step S3 is drained purple rice after soaking.

Preferably, the adhered rice grains are scattered by a scattering machine after the step S5, and the scraps are separated from the rice grains by a vibrating screen.

Preferably, the warm water is water with the temperature of 20-25 ℃. The purple rice that is showered with warm water in step S5 is to wash off the gelatinized starch on the surface of the rice.

Preferably, the water content of the purple rice dried in the step S5 is less than 10%. Is favorable for prolonging the storage property of the purple rice product.

Preferably, the breaking up in step S4 is performed by using a deblocking machine.

Preferably, the cooking in step S3 is steam cooking.

In addition, the instant purple rice prepared by the process method is also within the protection scope of the invention.

The invention relates to an edible method of purple rice instant rice, which comprises the following steps: taking purple rice instant rice, placing the purple rice instant rice in a rice box, and mixing the materials according to the weight ratio of 1: distilled water is injected into the rice water ratio of 1 (v: v), the heating bag is put into the heating box and then is quickly added to a certain water amount, the cover is quickly covered, and the user can eat the rice without gas emission after waiting for about 8 minutes.

Compared with the prior art, the invention has the beneficial effects that:

according to the preparation method of the purple rice, the purple rice is cooked by adopting specific cooking liquor, and then the purple rice is dried by combining roller drying and hot air drying, so that the problems of poor taste, poor rehydration property, hard rice grains, half-cooked rice and the like commonly existing in the purple rice are solved, the aging of the purple rice starch can be effectively reduced, the agglomeration of the purple rice during dehydration is avoided, the rice grains are full, the grain shape of the rice is well restored, the appearance quality of the purple rice grains is improved, the anthocyanin and the flavor in the purple rice are effectively retained, and the sensory and nutritional values of the purple rice after rehydration are improved.

Drawings

FIG. 1 shows the anthocyanin content of the purple rice instant rice;

FIG. 2 shows the hardness of the instant rice rehydrated with purple rice stored for different days;

FIG. 3 is a schematic view of four major components of a disposable self-heating lunchbox;

in the figures, experimental examples 1, 2, 3, 4, 5, and 6 refer to examples 1, 2, 3, 4, 1, and 6, respectively.

Detailed Description

The invention will be further described with reference to the drawings and the detailed description, which are not intended to limit the invention in any way. The starting reagents employed in the examples of the present invention are, unless otherwise specified, those that are conventionally purchased.

Example 1 preparation of purple rice instant rice

(1) Washing purple rice with clear water for 1 time to remove impurities and dust, without kneading;

(2) soaking purple rice in 25 deg.C warm water at a certain ratio (1: 3) for 45min to make purple rice absorb appropriate amount of water, and measuring water content of purple rice to be 31.4%;

(3) draining the soaked purple rice, and mixing the purple rice: cooking liquor (1: 1/w: w) is added with cooking liquor (containing 0.2% sucrose fatty acid ester, 0.1% isolated soy protein, 0.4% locust bean gum and 0.08% beta-cyclodextrin), and then cooked with steam for 15min to obtain half-cooked rice.

(4) Conveying the cooked rice to a deblocking conveyor belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing starch gelatinized on the surface of the cooked rice with warm water at 25 ℃, conveying the cooked rice scraped by a scraper knife at the end of the conveyor belt into a roasting machine at 100 ℃ to carry out roller drying for 50min, then loading the cooked rice into a sieve, transferring the sieve into a forced air drying oven at 65 ℃, and drying for 20min to obtain dried purple rice with the moisture content of 9.7%;

(5) and (3) rubbing the dried rice by using a rubbing machine to remove the adhered rice grains, separating the scraps from the rice grains by using a vibrating screen, cooling to room temperature, and performing warm finishing and packaging to obtain the purple rice instant rice.

The preparation method of the cooking liquor comprises the following steps: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 5-15 min at the rotating speed of 10000-12000 r/min in an ice bath, and then adding locust bean gum and beta-cyclodextrin into the dispersion liquid to be mixed uniformly to obtain the product.

Example 2 preparation of purple Rice instant Rice

(1) Washing purple rice with clear water for 1 time to remove impurities and dust, without kneading;

(2) soaking purple rice in 25 deg.C warm water at a certain ratio (1: 3) for 45min to make purple rice absorb appropriate amount of water, and measuring water content of purple rice to be 32.1%;

(3) draining the soaked purple rice, and mixing the purple rice: cooking liquor (1: 1/w: w) is added with cooking liquor (containing 0.2% sucrose fatty acid ester, 0.1% isolated soy protein, 0.5% locust bean gum and 0.06% beta-cyclodextrin), and then cooked with steam for 15min to obtain half-cooked rice.

(4) Conveying the cooked rice to a deblocking conveyor belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing starch gelatinized on the surface of the cooked rice with warm water at 25 ℃, conveying the cooked rice scraped by a scraper knife at the end of the conveyor belt into a roasting machine at 110 ℃ to carry out roller drying for 50min, then loading the cooked rice into a sieve, transferring the sieve into a forced air drying oven at 65 ℃, and drying for 30min to obtain dried purple rice with the moisture content of 9.7%;

(5) and (3) rubbing the dried rice by using a rubbing machine to remove the adhered rice grains, separating the scraps from the rice grains by using a vibrating screen, cooling to room temperature, and performing warm finishing and packaging to obtain the purple rice instant rice.

The preparation method of the cooking liquor comprises the following steps: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 15min at rotation speed of 10000r/min under ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and mixing.

Example 3 preparation of purple Rice instant Rice

(1) Washing purple rice with clear water for 1 time to remove impurities and dust, without kneading;

(2) soaking purple rice in 25 deg.C warm water at a certain ratio (1: 3) for 45min to make purple rice absorb appropriate amount of water, and measuring water content of purple rice to be 32.6%;

(3) draining the soaked purple rice, and mixing the purple rice: cooking liquor (1: 1/w: w) is added with cooking liquor (containing 0.3% sucrose fatty acid ester, 0.3% isolated soy protein, 0.5% locust bean gum and 0.08% beta-cyclodextrin), and then cooked with steam for 15min to obtain half-cooked rice.

(4) Conveying the cooked rice to a deblocking conveyor belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing starch gelatinized on the surface of the cooked rice with warm water at 25 ℃, conveying the cooked rice scraped by a scraper knife at the end of the conveyor belt into a roasting machine at 100 ℃ to carry out roller drying for 40min, then loading the cooked rice into a sieve, transferring the sieve into a forced air drying oven at 65 ℃, and drying for 30min to obtain dried purple rice with the moisture content of 9.4%;

(5) and (3) rubbing the dried rice by using a rubbing machine to remove the adhered rice grains, separating the scraps from the rice grains by using a vibrating screen, cooling to room temperature, and performing warm finishing and packaging to obtain the purple rice instant rice.

The preparation method of the cooking liquor comprises the following steps: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 15min at rotation speed of 10000r/min under ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and mixing.

Example 4 preparation of purple Rice instant Rice

(1) Washing purple rice with clear water for 1 time to remove impurities and dust, without kneading;

(2) soaking purple rice in 25 deg.C warm water at a certain ratio (1: 3) for 45min to make purple rice absorb appropriate amount of water, and measuring water content of purple rice to be 34.1%;

(3) draining the soaked purple rice, and mixing the purple rice: cooking liquor (1: 1/w: w) is added with cooking liquor (containing 0.1% sucrose fatty acid ester, 0.1% isolated soy protein, 0.3% locust bean gum and 0.05% beta-cyclodextrin), and then cooked with steam for 20min to obtain half-cooked rice.

(4) Conveying the cooked rice to a deblocking conveyer belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing starch gelatinized on the surface of the cooked rice with warm water at 25 ℃, conveying the cooked rice scraped by a scraper knife at the end of the conveyer belt into a roasting machine at 110 ℃ to carry out roller drying for 40min, then loading the cooked rice into a sieve, transferring the sieve into a forced air drying oven at 65 ℃, and drying for 20min to obtain dried purple rice with the moisture content of 9.5%;

(5) and (3) rubbing the dried rice by using a rubbing machine to remove the adhered rice grains, separating the scraps from the rice grains by using a vibrating screen, cooling to room temperature, and performing warm finishing and packaging to obtain the purple rice instant rice.

The preparation method of the cooking liquor comprises the following steps: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 5min at 12000r/min under ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and mixing.

EXAMPLE 5 preparation of purple Rice instant Rice

(1) Washing purple rice with clear water for 1 time to remove impurities and dust, without kneading;

(2) soaking purple rice in 25 deg.C warm water at a certain ratio (1: 3) for 60min to make purple rice absorb appropriate amount of water, and measuring water content of purple rice to be 34.9%;

(3) draining the soaked purple rice, and mixing the purple rice: cooking liquor (1: 1/w: w) containing 1% sucrose fatty acid ester, 1% isolated soy protein, 0.4% locust bean gum and 0.08% beta-cyclodextrin is added, and then cooked with steam for 15min to obtain half-cooked rice.

(4) Conveying the cooked rice to a deblocking conveyer belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing starch gelatinized on the surface of the cooked rice with warm water at 25 ℃, conveying the cooked rice scraped by a scraper knife at the end of the conveyer belt into a roasting machine at 100 ℃ to carry out roller drying for 50min, then loading the cooked rice into a sieve, transferring the sieve into a blast drying oven at 70 ℃, and drying for 20min to obtain dried purple rice with the moisture content of 9.8%;

(5) and (3) rubbing the dried rice by using a rubbing machine to remove the adhered rice grains, separating the scraps from the rice grains by using a vibrating screen, cooling to room temperature, and performing warm finishing and packaging to obtain the purple rice instant rice.

The preparation method of the cooking liquor comprises the following steps: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 10min at rotation speed of 10000r/min under ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and mixing.

Example 6 preparation of purple Rice instant Rice

(1) Washing purple rice with clear water for 1 time to remove impurities and dust, without kneading;

(2) soaking purple rice in 25 deg.C warm water at a certain ratio (1: 3) for 50min to make purple rice absorb appropriate amount of water, and measuring water content of purple rice to be 34.5%;

(3) draining the soaked purple rice, and mixing the purple rice: cooking liquor (1: 1/w: w) is added with cooking liquor (containing 0.2% sucrose fatty acid ester, 0.1% isolated soy protein, 1% locust bean gum and 0.5% beta-cyclodextrin), and then cooked with steam for 15min to obtain half-cooked purple rice.

(4) Conveying the cooked rice to a deblocking conveyer belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing starch gelatinized on the surface of the cooked rice with warm water at 25 ℃, conveying the cooked rice scraped by a scraper knife at the end of the conveyer belt into a roasting machine at 100 ℃ to carry out roller drying for 50min, then loading the cooked rice into a sieve, transferring the sieve into a blast drying oven at 60 ℃, and drying for 30min to obtain dried purple rice with the moisture content of 9.7%;

(5) and (3) rubbing the dried rice by using a rubbing machine to remove the adhered rice grains, separating the scraps from the rice grains by using a vibrating screen, cooling to room temperature, and performing warm finishing and packaging to obtain the purple rice instant rice.

The preparation method of the cooking liquor comprises the following steps: adding sucrose fatty acid ester and soybean protein isolate into water, dispersing for 10min at 12000r/min under ice bath, adding locust bean gum and beta-cyclodextrin into the dispersion, and mixing.

Comparative example 1

The preparation method was the same as example 1 except that the cooking liquor contained 0.01% sucrose fatty acid ester, 0.01% soy protein isolate, 0.05% locust bean gum and 0.01% beta-cyclodextrin.

Comparative example 2

The preparation method is the same as example 1, except that no locust bean gum is contained in the cooking liquor.

Comparative example 3

The preparation is as in example 1, except that the cooking liquor does not contain beta-cyclodextrin.

Comparative example 4

The preparation method was the same as in example 1 except that the cooking liquor contained no sucrose fatty acid ester.

Comparative example 5

The preparation method was the same as example 1 except that locust bean gum in the cooking solution was replaced with carrageenan.

Comparative example 6

The preparation method is the same as that of example 1, except that the drying in step (4) is not performed by drum drying, but performed only by using a 65 ℃ forced air drying oven until the moisture content of the purple rice is less than 10%.

Comparative example 7

The preparation method is the same as that of example 1, except that the step (4) is as follows: conveying the cooked rice to a deblocking conveyer belt, dropping the cooked rice into a deblocking machine to be beaten and dispersed, flushing the gelatinized starch on the surface of the cooked rice with warm water, conveying the cooked rice scraped by a scraper knife at the end of the conveyer belt into a roasting machine at 80 ℃ to carry out roller drying for 50min, then loading the cooked rice into a sieve, and transferring the sieve into a forced air drying oven at 65 ℃ until the moisture content of the purple rice is lower than 10%.

Experiment 1 testing of rehydration characteristics of instant rice

The red rice instant rice prepared in examples 1 to 6 and comparative examples 1 to 7 was subjected to the rehydration test.

1. Experimental methods

1) And (3) measuring the rehydration rate: accurately weighing A g finished product of instant rice, placing in a beaker, adding 5 times of boiling water, immediately covering, draining water immediately after rehydrating in a 90 ℃ water bath kettle for 15min, sucking water on the surface of the rice by using filter paper and a suction pipe, and weighing B g, wherein the rehydration rate is represented by B/A. Each kind of purple rice was divided into 3 groups, and the results were averaged.

2) Determination of rehydration time: weighing about 10g of purple rice finished instant rice product, placing the product in a beaker, adding 5 times of boiling water, immediately covering the beaker, placing the beaker in a water bath kettle at 90 ℃ for rehydration, sealing the beaker for 5min, taking 1 grain of rice out of the beaker, placing the rice on a glass plate, covering another glass plate, applying pressure on the glass plate, observing whether the grain of rice on the glass plate has a white core or not, if the grain of rice has the white core, measuring the grain of rice at intervals of 0.5min for 1 time until the grain of rice has no white core, and recording the time, namely the rehydration time of the instant rice. Each kind of purple rice was divided into 3 groups, and the results were averaged.

2. Results of the experiment

TABLE 1 rehydration Properties of instant purple Rice

As can be seen from the results in Table 1, the instant purple rice prepared by the embodiment of the invention has good rehydration property, the rehydration time is 5.75-6.75 min, and the rehydration rate is 2.22% -2.38%. In addition, the rehydrating time of the instant purple rice of the comparative examples 6 to 7 is longer, 9.5 to 10.5min is achieved, and the rehydrating rate is lower and is 1.89 to 1.91 percent. The invention shows that the rehydration characteristic of the purple rice instant rice can be effectively improved by controlling the specific drying mode.

Experiment 2 test of anthocyanin content in instant rice with purple rice

The anthocyanin content of the instant rice prepared in examples 1 to 6 and comparative examples 1 to 7 was tested.

1. Experimental methods

1) Preparation of samples: crushing the purple rice instant rice to obtain purple rice powder, weighing 0.1g of the purple rice powder which is sieved by a 100-mesh sieve, adding 10mL of the purple rice powder according to the weight ratio of 85: 15 volume ratio of the mixture of 95% ethanol and 1.5mol/L HCl, extracting in water bath at 60 ℃ for 5h, re-metering to 10mL, shaking up, standing, and obtaining the extract which is the anthocyanin original solution.

2) The method for measuring the purple rice anthocyanin comprises the following steps: the absorbance of the sample solution was measured at a wavelength of 540 nm. The average was taken over 5 replicates.

2. Results of the experiment

The result of the anthocyanin content test in the instant rice prepared in the examples 1 to 6 and the comparative examples 1 to 7 is shown in fig. 1, and it can be seen from fig. 1 that the anthocyanin content in the instant rice prepared in the invention, namely the instant rice prepared in the examples 1 to 6, is higher than 0.06g/100g, while the anthocyanin content in the instant rice prepared in the comparative examples except the method of the comparative example 4 is only 0.035 to 0.055g/100g, which shows that the anthocyanin in the instant rice prepared by the invention can be effectively retained by controlling the specific preparation method, and the nutritional value of the instant rice prepared by the invention is improved.

Experiment 3 test of starch aging degree in instant rice with purple rice

The starch retrogradation degree of the instant rice of purple rice prepared in examples 1 to 6 and comparative examples 1 to 7 was measured.

1. Experimental methods

Research shows that the aging degree of the starch can be well reflected by the hardness, and the larger the hardness is, the larger the aging degree is. Weighing 10g of finished instant purple rice, placing in a beaker, adding 5 times of boiling water, immediately covering, rehydrating in a water bath kettle at 90 ℃ for 15min, immediately removing excess water by using a suction pipe, cooling to room temperature, sealing the rehydrated purple rice, placing in a refrigerator at 4 ℃, storing for 0, 3 and 7 days, and measuring the hardness by using a texture analyzer (Shimadzu corporation, Japan). Measuring the texture parameters of the purple rice: the speed before measurement is 1mm/s, the speed after measurement is 1mm/s, and the speed after measurement is 2 mm/s; the trigger force value is 5g, and the compression ratio is 50%. The object stage and the probe are cleaned for measuring the gap. For each sample, 5 replicates were run and the average was taken.

2. Results of the experiment

Fig. 2 shows the hardness test results of the instant purple rice after being rehydrated and stored in a refrigerator at 4 ℃ for different days, and it can be seen from fig. 2 that the instant purple rice prepared by the methods of examples 1 to 6 of the present invention has lower hardness than comparative examples 1 to 7 after being rehydrated, and the hardness of examples 1 to 6 is still lower than comparative examples 1 to 7 after being revived for a certain number of days, which shows that the instant purple rice obtained by controlling the specific preparation method of the present invention can reduce the hardness of rice to a certain extent and delay the reviving of rice.

Experiment 4 hardness, chewiness and sensory evaluation experiment of purple rice instant rice

1. Experimental methods

(1) The purple rice instant rice prepared in examples 1 to 6 and comparative examples 1 to 7 was rehydrated and then tested for hardness and chewiness:

weighing 10g of the finished product of the purple rice instant rice, placing in a beaker, adding 5 times of boiling water, immediately covering, rehydrating in a water bath kettle at 90 ℃ for 15min, immediately removing excess water by using a suction pipe, and measuring the hardness and the chewiness by adopting a texture analyzer (Shimadzu corporation, Japan) after the purple rice is cooled to room temperature. Measuring the texture parameters of the purple rice: the speed before measurement is 1mm/s, the speed after measurement is 1mm/s, and the speed after measurement is 2 mm/s; the trigger force value is 5g, the compression ratio is 50%, and the time interval between two times of compression is 5 s. The object stage and the probe are cleaned for measuring the gap. For each sample, 5 replicates were run and the average was taken.

(2) Sensory evaluation after rehydration was performed on the purple rice instant rice prepared in examples 1 to 6 and comparative examples 1 to 7:

taking 40-50 g of purple rice instant rice, placing the purple rice instant rice in a rice box (II in figure 3), and mixing the materials according to the proportion of 1: distilled water is injected into the rice water ratio of 1 (v: v), the heating bag (shown in the third step in the figure 3) is placed into the heating box (shown in the fourth step in the figure 3), then a certain amount of water is quickly added, then the box is quickly covered with a cover (shown in the fourth step in the figure 3), and the sensory evaluation can be carried out after the box is kept for about 8 minutes until no gas is emitted.

Referring to a sensory evaluation method for inspecting the cooking quality of rice and rice by GB _ T15682-. The detailed scoring criteria are shown in table 2.

TABLE 2 sensory evaluation table for purple rice

2. Results of the experiment

TABLE 3 texture characteristics and sensory evaluation scores of purple rice instant rice

As can be seen from the results of Table 3, the instant rice prepared according to the methods of examples 1 to 6 of the present invention was lower in hardness and chewiness than those of comparative examples 1 to 7 after rehydration and superior in sensory evaluation results to those of comparative examples 1 to 7, and although the instant rice prepared according to comparative examples 1 and 2 was similar in sensory evaluation to those of examples 1 to 6, the instant rice of comparative examples 1 and 2 was not suitable for long-term storage and had a serious anthocyanin loss as seen from the experimental results of anthocyanin content and starch retrogradation in the instant rice.

According to the processing technology of the instant purple rice, the specific cooking liquor is adopted to cook the purple rice, and then the roller drying and hot air drying technologies are combined to perform drying, so that the problems of poor taste, poor rehydration property, hard rice grains, half-cooked rice and the like of the instant purple rice are solved, the aging of the starch of the purple rice can be effectively reduced, the agglomeration of the purple rice during dehydration is avoided, the rice grains are full, the grain shape of the rice is well restored, the sensory quality of the purple rice grains is improved, the anthocyanin and the flavor fragrance of the purple rice are effectively reserved, and the taste and the nutritional value of the rehydrated purple rice are improved.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.