A kind of preparation method of enzymatically hydrolyzed black rice flour

Abstract

The invention discloses a method for preparing enzymatically hydrolyzed black rice powder. The method extracts anthocyanins from black rice to prepare dry powder, then enzymatically hydrolyzes the black rice to reduce the content of macromolecules, improve solubility and taste, and then mixes the black rice anthocyanins and the enzymatically hydrolyzed black rice powder and coats them with an antioxidant coating layer that can be rapidly disintegrated in water, so that the nutrients and flavor are retained for a longer period of time without affecting the solubility. The enzymatically hydrolyzed black rice powder prepared by the invention is a new type of cereal beverage powder that is easy to brew, has a good taste, and is rich in nutrition.

Description

Technical Field

[0001] The invention relates to the field of food, in particular to a method for preparing enzymatically hydrolyzed black rice flour. Background Art

[0002] Black rice has a long history of cultivation. It is an ancient and precious rice variety in China. It has always been known as the "black pearl". With its low price and wide access to the advantages, it plays an irreplaceable role in rice crops. As a functional rice and whole grain resource, it contains a large number of bioactive ingredients in its pericarp, seed coat and germ, including phenolic compounds, oryzanol, amino acids, multiple vitamins, flavonoids, dietary fiber, anthocyanins, unsaturated fatty acids and trace elements. Studies have shown that black rice anthocyanins, as a natural active substance, have anti-inflammatory, antioxidant, anti-cancer, cardiovascular disease prevention, and fat metabolism regulation effects.

[0003] As a healthy beverage, cereal beverages have become a research hotspot. Black rice is often used to develop whole-grain beverage products because it is rich in nutrients such as carbohydrates and proteins. However, due to the easy aging of starch and the rough texture of dietary fiber particles, the stability of black rice beverage products is often improved by enzymatic hydrolysis. However, the degradation of its macromolecules has a great impact on the stability and activity of its anthocyanins. Finding a method that can improve the taste of the beverage without losing the anthocyanin content of black rice is a problem that needs to be solved now. Summary of the invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing enzymatically hydrolyzed black rice flour. The method for preparing enzymatically hydrolyzed black rice flour provided by the present invention can retain the content of black rice anthocyanins to a great extent and further improve the solubility and antioxidant properties of black rice flour.

[0005] The present invention provides a method for preparing enzymatically hydrolyzed black rice flour, comprising the following steps:

[0006] (1) Crushing:

[0007] Wash the black rice with distilled water for 2-3 times, dry it at 80°C to constant weight, and grind it through an 80-mesh sieve to obtain black rice fine powder;

[0008] (2) Enzymatic hydrolysis:

[0009] The black rice powder and distilled water are mixed in a mass volume ratio of 1:4, heated to 95-105° C. for gelatinization for 40-50 min, 2% citric acid is used to adjust the pH to 6.0, and then 0.05-0.1% of the mass of the black rice powder is added with a thermostable α-amylase, and the temperature is kept for enzymolysis for 30-40 min; then the system is cooled to 55-65° C., and then 0.1-0.2% of the mass of the black rice powder is added with a pullulanase, and the temperature is kept for enzymolysis for 40-60 min;

[0010] (3) Grinding and dispersion:

[0011] Add corn oil (1-2% by weight of black rice powder) and maltodextrin (5-7% by weight of black rice powder) to the above system, stir evenly and pass through a colloid mill with a gap of 0.1-0.2 mm to obtain an enzymatically hydrolyzed black rice slurry;

[0012] (4) Spray drying:

[0013] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 180-200°C, the peristaltic pump speed to 20-30RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain the primary material;

[0014] (5) Antioxidant coating:

[0015] The primary material is placed in a fluidized bed and coated with an antioxidant to obtain enzymatically hydrolyzed black rice flour.

[0016] Among them, the specific steps of antioxidant coating are:

[0017] a. Add the primary material into the fluidized bed, set the flow rate in the fluidized bed to 3-5m / s and the temperature to 70-80℃;

[0018] b. Turn on the heater, add the antioxidant coating agent in a mass volume ratio of 1:1 to the primary material and preheat to 70-80°C. After the temperature of the antioxidant coating agent reaches the set value, turn on the blower and adjust the nozzle pressure to 1-1.2Mpa, and start the annular gap nozzle for spray coating;

[0019] c. After spraying for 2-3 minutes, close the annular gap nozzle, add 0.5-0.7% of the primary material mass of low-substituted hydroxypropyl cellulose powder at the feed inlet, and continue to start the annular gap nozzle for spray coating for 2-3 minutes after blast drying for 2-3 minutes. Repeat this cycle until the primary material particle size is 0.4-0.5mm and then stop spray coating;

[0020] d. After spraying is completed, continue to maintain the temperature and fluidization of particles in the fluidized bed, and blow dry for 1-1.5 hours;

[0021] e. After the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened to discharge the material to obtain an enzymatically hydrolyzed black rice flour.

[0022] Wherein, the preparation method of the antioxidant coating agent is:

[0023] i. The reaction chamber is vented with nitrogen for 10-15min, 10 parts of distilled water are heated to 40-45 ℃, 10-15 parts of sodium citrate and 1-3 parts of sodium D-isoascorbate are added and stirred to obtain a mixture a;

[0024] ii. Add 1-3 parts of xanthan gum powder to 5 parts of distilled water and stir evenly to obtain a xanthan gum solution;

[0025] iii. While stirring the mixed solution a at a stirring rate of 300 r / min, add the xanthan gum solution, and then ultrasonically disperse for 5-7 minutes to obtain the antioxidant coating agent.

[0026] The present invention provides a method for preparing enzymatically hydrolyzed black rice flour, comprising the following steps:

[0027] 1) Extraction:

[0028] The black rice is subjected to an ultrasonic extraction process to collect a black rice anthocyanin extract and a precipitate;

[0029] 2) Crushing:

[0030] The precipitate was washed 2-3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0031] 3) Enzymatic hydrolysis:

[0032] The black rice powder and distilled water are mixed in a mass volume ratio of 1:4, heated to 95-105° C. for gelatinization for 40-50 min, 2% citric acid is used to adjust the pH to 6.0, and then 0.05-0.1% of the mass of the black rice powder is added with a thermostable α-amylase, and the temperature is kept for enzymolysis for 30-40 min; then the system is cooled to 55-65° C., and then 0.1-0.2% of the mass of the black rice powder is added with a pullulanase, and the temperature is kept for enzymolysis for 40-60 min;

[0033] 4) Grinding and dispersion:

[0034] Add corn oil (1-2% by weight of black rice powder) and maltodextrin (5-7% by weight of black rice powder) to the above system, stir evenly and pass through a colloid mill with a gap of 0.1-0.2 mm to obtain an enzymatically hydrolyzed black rice slurry;

[0035] 5) Spray drying:

[0036] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 180-200°C, the peristaltic pump speed to 20-30RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain the primary material;

[0037] 6) Antioxidant coating:

[0038] The primary material and the black rice anthocyanin extract are uniformly mixed in a mass ratio of 200:1, and then placed in a fluidized bed to be coated with an antioxidant to obtain enzymatically hydrolyzed black rice powder.

[0039] Among them, the ultrasonic extraction process is:

[0040] A. Wash the black rice with distilled water for 2-3 times, dry it at 80℃ to constant weight, and grind it through a 60-mesh sieve to obtain black rice flour;

[0041] B. Add 4-6% citric acid solution to black rice flour at a solid-liquid ratio of 1:5, mix thoroughly, and then perform ultrasonic extraction at 25-30°C for 25-30 minutes;

[0042] C. After the ultrasonic extraction is completed, the supernatant is collected by centrifugation, and the supernatant is distilled at 40°C until no solvent is evaporated to obtain the black rice anthocyanin concentrate;

[0043] D. Freeze-dry the above black rice anthocyanin concentrate in a freeze dryer to obtain a black rice anthocyanin extract.

[0044] The characteristics of the present invention are:

[0045] 1) High-temperature amylase can quickly hydrolyze starch molecules at a higher temperature, and reducing the enzymatic hydrolysis time can prevent black rice flour from being exposed to oxidation for a long time. However, the addition of α-amylase alone for enzymatic hydrolysis will make the food sticky and affect the taste. Therefore, the present invention increases the proportion of straight-chain starch through the enzymatic hydrolysis of high-temperature resistant α-amylase and pullulanase under high and medium temperature conditions, making black rice flour easier to dissolve and absorb. The present invention also enhances the instant solubility of black rice flour by adding a certain proportion of corn oil and maltodextrin after enzymatic hydrolysis, and can also add a sweet taste to the black rice flour.

[0046] 2) After being treated with two enzyme preparations, although the solubility is enhanced, the antioxidant property is reduced, and the increase of amylose will cause the food made from the enzymatic black rice flour to undergo starch aging, affecting the taste and quality of the food. Therefore, the present invention performs antioxidant coating on the enzymatic black rice flour, so that the product can be stored for a long time without losing its flavor, and hinders the polymerization of amylose, thereby inhibiting the aging phenomenon.

[0047] 3) Enzymatic black rice powder will bring extra sweetness and cover up the rice aroma. Sodium citrate can correct the extra sweetness of black rice caused by enzymatic hydrolysis, making the enzymatic black rice powder beverage sweet but not greasy; the color of enzymatic black rice powder will be oxidized and faded after long-term storage. Sodium D-isoascorbate can maintain the color and natural flavor of food, extend the shelf life, and has no toxic side effects; the present invention uses the above two substances to compound antioxidants to solve the problems of excess sweetness and easy color oxidation. Food-grade low-substituted hydroxypropyl cellulose has good disintegration performance. Low-substituted hydroxypropyl cellulose is added midway during the coating of antioxidants to disperse it in the middle of the antioxidant coating layer. When the enzymatic black rice powder is dissolved in water, the low-substituted hydroxypropyl cellulose quickly disintegrates and destroys the antioxidant coating layer after contacting water, which not only plays an antioxidant role, but also does not affect the solubility of the enzymatic black rice powder.

[0048] 4) Black rice contains rich nutrients, among which black rice anthocyanins are the most prominent. Black rice anthocyanins have physiological functions such as anti-oxidation, lowering blood lipids, inhibiting cancer and anti-cancer, and inhibiting bacteria, inflammation and anti-allergy. In order to make the taste of black rice beverage better and the preparation method more concise, enzymatic hydrolysis of black rice will destroy more than 90% of the anthocyanins in black rice. The present invention extracts anthocyanins from black rice, and it is found that the enzymatic hydrolysis effect of black rice powder from which anthocyanins have been extracted is better. After the process of the present invention, the anthocyanins in black rice can be retained to a great extent, and the enzymatic hydrolysis of black rice can improve its solubility and taste. Among them, xanthan gum can also well protect anthocyanins from being oxidized and degraded, and can also maintain the color stability of black rice beverage. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below in conjunction with the embodiments.

[0050] Unless otherwise specified, the raw materials or food additives used in the embodiments of the present invention are obtained through conventional commercial channels.

[0051] Example 1

[0052] This embodiment includes the following steps:

[0053] 1) Crushing:

[0054] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0055] 2) Enzymatic hydrolysis:

[0056] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then add 8g of thermostable α-amylase, and keep warm for enzymolysis for 35min; then cool the system to 60℃, then add 15g of pullulanase, and keep warm for enzymolysis for 35min;

[0057] 3) Grinding and dispersion:

[0058] Add 150g corn oil and 600g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0059] 4) Spray drying:

[0060] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.4 kg of primary material;

[0061] 5) Preparation of antioxidant coating agent:

[0062] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0063] 6) Antioxidant coating:

[0064] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 4 m / s and 75° C.; the heater is turned on, 9.4 L of an antioxidant coating agent is added and preheated to 75° C., and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, 56.4 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2.5 minutes, the annular gap nozzle is continuously started for spray coating for 2.5 minutes, and the spray coating can be stopped after the cycle is repeated until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0065] Example 2

[0066] This embodiment includes the following steps:

[0067] 1) Crushing:

[0068] 10 kg of black rice was washed twice with distilled water, dried at 80° C. to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0069] 2) Enzymatic hydrolysis:

[0070] Add black rice powder to 40L distilled water, stir and mix, heat to 95℃ for gelatinization for 40min, adjust pH to 6.0 with 2% citric acid, then add 5g of thermostable α-amylase, and keep warm for 30min; then cool the system to 60℃, add 10g of pullulanase, and keep warm for 40min;

[0071] 3) Grinding and dispersion:

[0072] Add 100g corn oil and 500g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.1mm to obtain an enzymatically hydrolyzed black rice slurry;

[0073] 4) Spray drying:

[0074] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 180°C, the peristaltic pump speed to 20RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.2 kg of primary material;

[0075] 5) Preparation of antioxidant coating agent:

[0076] The reaction chamber was ventilated with nitrogen for 10 minutes, 10L of distilled water was heated to 40°C, 10g of sodium citrate and 1g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 25g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 5 minutes to obtain an antioxidant coating agent;

[0077] 6) Antioxidant coating:

[0078] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 3 m / s and 70°C; the heater is turned on, 9.2 L of an antioxidant coating agent is added and preheated to 70°C, and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2 minutes, the annular gap nozzle is closed, 46 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2 minutes, the annular gap nozzle is continuously started for spray coating for 2 minutes, and the spray coating can be stopped after the cycle is repeated until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1 hour; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0079] Example 3

[0080] This embodiment includes the following steps:

[0081] 1) Crushing:

[0082] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0083] 2) Enzymatic hydrolysis:

[0084] Add black rice powder to 40L distilled water, stir and mix, heat to 105℃ for gelatinization for 50min, adjust pH to 6.0 with 2% citric acid, then add 10g of thermostable α-amylase, and keep warm for 40min; then cool the system to 60℃, add 20g of pullulanase, and keep warm for 60min;

[0085] 3) Grinding and dispersion:

[0086] Add 200g corn oil and 700g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.2mm to obtain an enzymatically hydrolyzed black rice slurry;

[0087] 4) Spray drying:

[0088] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 200°C, the peristaltic pump speed to 30RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 10.2 kg of primary material;

[0089] 5) Preparation of antioxidant coating agent:

[0090] The reaction chamber was ventilated with nitrogen for 15 minutes, 10L of distilled water was heated to 45°C, 15g of sodium citrate and 3g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 75g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 7 minutes to obtain an antioxidant coating agent;

[0091] 6) Antioxidant coating:

[0092] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 5 m / s and 80° C.; the heater is turned on, 10.2 L of an antioxidant coating agent is added and preheated to 80° C., and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.2 MPa, and the annular gap nozzle is started for spray coating; after spraying for 3 minutes, the annular gap nozzle is closed, 71.4 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 3 minutes, the annular gap nozzle is continuously started for spray coating for 3 minutes, and the spray coating can be stopped after the cycle is repeated until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.5 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0093] Example 4

[0094] This embodiment includes the following steps:

[0095] 1) Extraction:

[0096] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through a 60-mesh sieve to obtain black rice powder; 50 L of 5% citric acid solution was added to the black rice powder, mixed thoroughly, and then ultrasonically extracted at 30°C for 30 min; after the ultrasonic extraction was completed, the supernatant was collected by centrifugation, and the precipitate was set aside, and the supernatant was distilled at 40°C until no solvent was evaporated to obtain a black rice anthocyanin concentrate; the above black rice anthocyanin concentrate was freeze-dried in a freeze dryer to obtain a black rice anthocyanin extract;

[0097] 2) Crushing:

[0098] The precipitate was washed three times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0099] 2) Enzymatic hydrolysis:

[0100] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then add 8g of thermostable α-amylase, and keep warm for enzymolysis for 35min; then cool the system to 60℃, then add 15g of pullulanase, and keep warm for enzymolysis for 35min;

[0101] 3) Grinding and dispersion:

[0102] Add 150g corn oil and 600g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0103] 4) Spray drying:

[0104] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 8.8 kg of primary material;

[0105] 5) Preparation of antioxidant coating agent:

[0106] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0107] 6) Antioxidant coating:

[0108] 44 g of black rice anthocyanin extract is added to the primary material, mixed evenly, and then added to the fluidized bed, and the flow velocity in the fluidized bed is set to 4 m / s and the temperature is set to 75° C.; the heater is turned on, 8.8 L of an antioxidant coating agent is added and preheated to 75° C., after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, 52.8 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2.5 minutes, the annular gap nozzle is continuously started for spray coating for 2.5 minutes, and the spray coating can be stopped when the particle size of the primary material is 0.4-0.5 mm; after spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continuously maintained, and blast drying is performed for 1.3 hours; after blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatic hydrolyzed black rice powder is discharged.

[0109] Comparative Example 1

[0110] This comparative example comprises the following steps:

[0111] 1) Crushing:

[0112] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0113] 2) Enzymatic hydrolysis:

[0114] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for 45min, adjust pH to 6.0 with 2% citric acid, then add 23g of thermostable α-amylase, and keep warm for 70min;

[0115] 3) Grinding and dispersion:

[0116] Add 150g corn oil and 600g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0117] 4) Spray drying:

[0118] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.4 kg of primary material;

[0119] 5) Preparation of antioxidant coating agent:

[0120] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0121] 6) Antioxidant coating:

[0122] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 4 m / s and 75° C.; the heater is turned on, 9.4 L of an antioxidant coating agent is added and preheated to 75° C., and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, 56.4 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2.5 minutes, the annular gap nozzle is continuously started for spray coating for 2.5 minutes, and the spray coating can be stopped after the cycle is repeated until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0123] Comparative Example 2

[0124] This comparative example comprises the following steps:

[0125] 1) Crushing:

[0126] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0127] 2) Enzymatic hydrolysis:

[0128] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then cool the system to 60℃, add 23g of pullulanase, and keep warm for enzymolysis for 70min;

[0129] 3) Grinding and dispersion:

[0130] Add 150g corn oil and 600g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0131] 4) Spray drying:

[0132] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.4 kg of primary material;

[0133] 5) Preparation of antioxidant coating agent:

[0134] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0135] 6) Antioxidant coating:

[0136] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 4 m / s and 75° C.; the heater is turned on, 9.4 L of an antioxidant coating agent is added and preheated to 75° C., and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, 56.4 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2.5 minutes, the annular gap nozzle is continuously started for spray coating for 2.5 minutes, and the spray coating can be stopped after the cycle is repeated until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0137] Comparative Example 3

[0138] This comparative example comprises the following steps:

[0139] 1) Crushing:

[0140] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0141] 2) Enzymatic hydrolysis:

[0142] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then add 8g of thermostable α-amylase, and keep warm for enzymolysis for 35min; then cool the system to 60℃, then add 15g of pullulanase, and keep warm for enzymolysis for 35min;

[0143] 3) Grinding and dispersion:

[0144] Add 150g corn oil to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0145] 4) Spray drying:

[0146] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 8.9 kg of primary material;

[0147] 5) Preparation of antioxidant coating agent:

[0148] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0149] 6) Antioxidant coating:

[0150] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 4 m / s and 75° C.; the heater is turned on, 8.9 L of an antioxidant coating agent is added and preheated to 75° C., and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, 53.4 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2.5 minutes, the annular gap nozzle is continuously started for spray coating for 2.5 minutes, and the spray coating can be stopped after the cycle until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0151] Comparative Example 4

[0152] This comparative example comprises the following steps:

[0153] 1) Crushing:

[0154] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0155] 2) Enzymatic hydrolysis:

[0156] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then add 8g of thermostable α-amylase, and keep warm for enzymolysis for 35min; then cool the system to 60℃, then add 15g of pullulanase, and keep warm for enzymolysis for 35min;

[0157] 3) Grinding and dispersion:

[0158] Add 600 g of maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15 mm to obtain an enzymatically hydrolyzed black rice slurry;

[0159] 4) Spray drying:

[0160] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.3 kg of primary material;

[0161] 5) Preparation of antioxidant coating agent:

[0162] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0163] 6) Antioxidant coating:

[0164] The primary material is added into a fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 4 m / s and 75° C.; the heater is turned on, 9.3 L of an antioxidant coating agent is added and preheated to 75° C., and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, 55.8 g of low-substituted hydroxypropyl cellulose powder is added to the feed port, and after blast drying for 2.5 minutes, the annular gap nozzle is continuously started for spray coating for 2.5 minutes, and the spray coating can be stopped after the cycle is repeated until the particle size of the primary material is 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0165] Comparative Example 5

[0166] This comparative example comprises the following steps:

[0167] 1) Crushing:

[0168] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0169] 2) Enzymatic hydrolysis:

[0170] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then add 8g of thermostable α-amylase, and keep warm for enzymolysis for 35min; then cool the system to 60℃, then add 15g of pullulanase, and keep warm for enzymolysis for 35min;

[0171] 3) Grinding and dispersion:

[0172] Add 150g corn oil and 600g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0173] 4) Spray drying:

[0174] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.4 kg of primary material;

[0175] 5) Preparation of antioxidant coating agent:

[0176] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0177] 6) Antioxidant coating:

[0178] The primary material is added into a fluidized bed, and the flow velocity in the fluidized bed is set to 4 m / s and the temperature is set to 75°C; the heater is turned on, 9.4 L of an antioxidant coating agent is added and preheated to 75°C, and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating; after spraying for 2.5 minutes, the annular gap nozzle is closed, and low-substituted hydroxypropyl cellulose powder is added to the feed port for coating, so that the particle size of the primary material reaches 03-0.4 mm, and then the annular gap nozzle is continued to be started for spray coating so that the particle size of the primary material reaches 0.4-0.5 mm; after the spraying is completed, the temperature in the fluidized bed and the fluidization of the particles are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging.

[0179] Comparative Example 6

[0180] This comparative example comprises the following steps:

[0181] 1) Crushing:

[0182] 10 kg of black rice was washed with distilled water for 3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice fine powder;

[0183] 2) Enzymatic hydrolysis:

[0184] Add black rice powder to 40L distilled water, stir and mix, heat to 100℃ for gelatinization for 45min, adjust pH to 6.0 with 2% citric acid, then add 8g of thermostable α-amylase, and keep warm for enzymolysis for 35min; then cool the system to 60℃, then add 15g of pullulanase, and keep warm for enzymolysis for 35min;

[0185] 3) Grinding and dispersion:

[0186] Add 150g corn oil and 600g maltodextrin to the above system, stir evenly and pass through a colloid mill with a gap of 0.15mm to obtain an enzymatically hydrolyzed black rice slurry;

[0187] 4) Spray drying:

[0188] Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 190°C, the peristaltic pump speed to 25RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain 9.4 kg of primary material;

[0189] 5) Preparation of antioxidant coating agent:

[0190] The reaction chamber was ventilated with nitrogen for 13 minutes, 10L of distilled water was heated to 43°C, 13g of sodium citrate and 2g of sodium D-isoascorbate were added and stirred evenly to obtain a mixed solution a; 50g of xanthan gum powder was added to 5L of distilled water and stirred evenly to obtain a xanthan gum solution; while stirring the mixed solution a at a stirring rate of 300r / min, the xanthan gum solution was added, and then ultrasonic dispersion was performed for 6 minutes to obtain an antioxidant coating agent;

[0191] 6) Antioxidant coating:

[0192] The primary material is added into the fluidized bed, and the flow velocity and temperature in the fluidized bed are set to 4 m / s and 75°C; the heater is turned on, 9.4 L of antioxidant coating agent is added and preheated to 75°C, and after the temperature of the antioxidant coating agent reaches the set value, the blower is turned on and the nozzle pressure is adjusted to 1.1 MPa, and the annular gap nozzle is started for spray coating, and the particle size of the primary material reaches 0.3-0.4 mm, and then the annular gap nozzle is closed; low-substituted hydroxypropyl cellulose powder is added to the feed port, and the particle size of the primary material reaches 0.4-0.5 mm; after the spraying is completed, the temperature and fluidization of the particles in the fluidized bed are continued to be maintained, and the blast drying is performed for 1.3 hours; after the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened, and the enzymatically hydrolyzed black rice powder is obtained by discharging the material.

[0193] experiment:

[0194] The enzymatically hydrolyzed black rice flour prepared in the above examples and comparative examples was tested for various indicators, and the experimental results are shown in Table 1. Dissolution time test: 30 g of each group of black rice flour was taken and added to 150 ml of warm water at 45°C, and the time of complete dissolution was recorded; Antioxidant test: 100 g of each group of black rice flour was spread in a thickness of 5 mm under constant temperature and light conditions of 30°C, and the time of discoloration, agglomeration and other phenomena was observed, within 3 days was poor, 3-5 days was good, and more than 5 days was excellent; Anthocyanin content determination: The total anthocyanin content of the black rice beverage was determined by the pH differential method.

[0195] Table 1

[0196] project Dissolution time Antioxidant Anthocyanin content mg / 100g Example 1 7.5 excellent 231 Example 2 7.6 excellent 235 Example 3 7.8 excellent 243 Example 4 7.4 excellent 496 Comparative Example 1 15.4 excellent / Comparative Example 2 15.8 excellent / Comparative Example 3 11.3 excellent / Comparative Example 4 10.7 excellent / Comparative Example 5 16.5 excellent / Comparative Example 6 16.7 excellent /

Claims

1. A method for preparing enzymatically hydrolyzed black rice flour, comprising pulverizing, enzymolysis, grinding and dispersing, spray drying, and antioxidant coating, characterized in that: (1) Crushing: Wash the black rice with distilled water for 2-3 times, dry it at 80°C to constant weight, and grind it through an 80-mesh sieve to obtain black rice fine powder; (2) Enzymatic hydrolysis: The black rice powder and distilled water were mixed in a mass volume ratio of 1:4, heated to 95-105 ° C for gelatinization for 40-50 minutes, adjusted to pH 6.0 with 2% citric acid, and then 0.05-0.1% of the mass of the black rice powder was added. The heat-resistant α-amylase was kept warm for 30-40 minutes; then the system was cooled to 55-65 ° C, and then 0.1-0.2% of the mass of the black rice powder was added. Pullulanase was kept warm for 40-60 minutes; (3) Grinding and dispersion: Add corn oil (1-2% by weight of black rice powder) and maltodextrin (5-7% by weight of black rice powder) to the above system, stir evenly and pass through a colloid mill with a gap of 0.1-0.2 mm to obtain an enzymatically hydrolyzed black rice slurry; (4) Spray drying: Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 180-200°C, the peristaltic pump speed to 20-30RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain the primary material; (5) Antioxidant coating: The primary material is placed in a fluidized bed and coated with an antioxidant to obtain an enzymatically hydrolyzed black rice powder; The specific steps of the antioxidant coating are: a. Add the primary material into the fluidized bed, set the flow rate in the fluidized bed to 3-5m / s and the temperature to 70-80℃; b. Turn on the heater, add the antioxidant coating agent in a mass volume ratio of 1:1 to the primary material and preheat to 70-80°C. After the temperature of the antioxidant coating agent reaches the set value, turn on the blower and adjust the nozzle pressure to 1-1.2Mpa, and start the annular gap nozzle for spray coating; c. After spraying for 2-3 minutes, close the annular gap nozzle, add 0.5-0.7% of the primary material mass of low-substituted hydroxypropyl cellulose powder at the feed inlet, and continue to start the annular gap nozzle for spray coating for 2-3 minutes after blast drying for 2-3 minutes. Repeat this cycle until the primary material particle size is 0.4-0.5mm and then stop spray coating; d. After spraying is completed, continue to maintain the temperature and fluidization of particles in the fluidized bed, and blow dry for 1-1.5 hours; e. After the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened to discharge the material to obtain an enzymatically hydrolyzed black rice powder.

2. A method for preparing enzymatically hydrolyzed black rice flour, comprising extraction, crushing, enzymolysis, grinding and dispersing, spray drying, and antioxidant coating, characterized in that: 1) Extraction: The black rice is subjected to an ultrasonic extraction process to collect a black rice anthocyanin extract and a precipitate; 2) Crushing: The precipitate was washed 2-3 times, dried at 80°C to constant weight, and crushed through an 80-mesh sieve to obtain black rice powder; 3) Enzymatic hydrolysis: The black rice powder and distilled water are mixed in a mass volume ratio of 1:4, heated to 95-105°C for gelatinization for 40-50 minutes, the pH is adjusted to 6.0 with 2% citric acid, and then 0.05-0.1% of the mass of the black rice powder is added with a thermostable α-amylase, and the temperature is kept for enzymolysis for 30-40 minutes; then the system is cooled to 55-65°C, and then 0.1-0.2% of the mass of the black rice powder is added with pullulanase, and the temperature is kept for enzymolysis for 40-60 minutes; 4) Grinding and dispersion: Add corn oil (1-2% by weight of black rice powder) and maltodextrin (5-7% by weight of black rice powder) to the above system, stir evenly and pass through a colloid mill with a gap of 0.1-0.2 mm to obtain an enzymatically hydrolyzed black rice slurry; 5) Spray drying: Add the enzymatically hydrolyzed black rice slurry into the spray dryer, set the inlet temperature to 180-200°C, the peristaltic pump speed to 20-30RPM, start the spray drying, collect the dried material at the discharge port, and then crush it through an 80-mesh sieve to obtain the primary material; 6) Antioxidant coating: The primary material and the black rice anthocyanin extract are mixed evenly in a mass ratio of 200:1, and then placed in a fluidized bed to coat the antioxidant, thereby obtaining an enzymatically hydrolyzed black rice powder; The specific steps of the antioxidant coating are: a. Add the primary material into the fluidized bed, set the flow rate in the fluidized bed to 3-5m / s and the temperature to 70-80℃; b. Turn on the heater, add the antioxidant coating agent in a mass volume ratio of 1:1 to the primary material and preheat to 70-80°C. After the temperature of the antioxidant coating agent reaches the set value, turn on the blower and adjust the nozzle pressure to 1-1.2Mpa, and start the annular gap nozzle for spray coating; c. After spraying for 2-3 minutes, close the annular gap nozzle, add 0.5-0.7% of the primary material mass of low-substituted hydroxypropyl cellulose powder at the feed inlet, and continue to start the annular gap nozzle for spray coating for 2-3 minutes after blast drying for 2-3 minutes. Repeat this cycle until the primary material particle size is 0.4-0.5mm and then stop spray coating; d. After spraying is completed, continue to maintain the temperature and fluidization of particles in the fluidized bed, and blow dry for 1-1.5 hours; e. After the blast drying is completed, the heater and the blower are turned off, and the valve in the discharge pipe at the lower part of the fluidized bed is opened to discharge the material to obtain an enzymatically hydrolyzed black rice powder.

3. The method according to claim 1 or 2, characterized in that: The preparation method of the antioxidant coating agent is: i. Pass ammonia gas through the reaction chamber for 10-15min, heat 10 parts of distilled water to 40-45°C, add 10-15 parts of sodium citrate and 1-3 parts of sodium D-isoascorbate and stir to obtain a mixture a; ii. Add 1-3 parts of xanthan gum powder to 5 parts of distilled water and stir evenly to obtain a xanthan gum solution; iii. The xanthan gum solution was added while stirring the mixed solution a at a stirring rate of 300 r / min, and then ultrasonically dispersed for 57 minutes to obtain the antioxidant coating agent.

4. The method according to claim 2, characterized in that: The ultrasonic extraction process is: A. Wash the black rice with distilled water 2-3 times, dry it at 80°C to constant weight, and grind it through a 60-mesh sieve to obtain black rice powder; B. adding 4-6% citric acid solution to black rice flour at a solid-liquid ratio of 1:5, mixing well and then performing ultrasonic extraction at 25-30° C. for 25-30 min; C. After the ultrasonic extraction is completed, the supernatant is collected by centrifugation, and the supernatant is distilled at 40° C. until no solvent is evaporated to obtain a black rice anthocyanin concentrate; D. Freeze-dry the above black rice anthocyanin concentrate in a freeze dryer to obtain a black rice anthocyanin extract.