Low-calorie red date and walnut meal replacement powder and preparation method thereof

Abstract

The invention provides low-calorie red date and walnut meal replacement powder and a preparation method thereof, and belongs to the field of food. The low-calorie red date and walnut meal replacement powder provided by the invention is prepared from the following raw materials: 30-40 parts of red date powder, 60-120 parts of walnut powder, 10-20 parts of cereal powder, 0-0.1 part of sucralose and 0-0.02 part of tert-butylhydroquinone. The cereal powder is composed of black rice powder and red bean powder. The invention further provides a preparation method of the low-calorie red date and walnut meal replacement powder. The red dates and the walnuts are crushed through a superfine crushing technology, nutrient substances of the red dates and the walnuts in the prepared meal replacement powder can be dissolved out to the maximum extent, the red dates and the walnuts are utilized in a high-value mode, and the prepared meal replacement powder is good in powder dispersity, good in rehydration performance and excellent in flavor and has the obvious and specific taste and smell of the red dates and the walnuts.

Description

Technical Field

[0001] The invention belongs to the field of food, and particularly relates to a low-calorie red date and walnut meal replacement powder and a preparation method thereof. Background Art

[0002] Red dates are usually eaten fresh or processed into candied fruit, date paste, etc. They are rich in vitamin C, vitamin P, various trace elements and sugars, and have high nutritional value. They can replenish blood, lower blood pressure, enhance human immunity, and have certain effects on protecting the liver, calming the nerves and soothing the mind. Walnuts are rich in protein, fat, vitamin B1, vitamin B2, vitamin E, phosphorus, calcium, α-linolenic acid and brown flower acid. The protein contains 18 kinds of amino acids, including 8 essential amino acids for the human body. It has the effects of preventing and relieving type II diabetes, lowering cholesterol, and inhibiting the growth of cancer cells. Therefore, the preparation of related meal replacement powders using red dates and walnuts as raw materials provides a simple way to eat red dates and walnuts, which can effectively obtain the nutrients of red dates and walnuts.

[0003] However, at present, conventional red date powder and walnut powder are processed by ordinary crushing means. The temperature of the material rises during crushing, which will cause the effective ingredients in the material to evaporate, deteriorate, and lose, and the quality will decrease. In addition, the sugar content in red dates is high, and the oil content in walnuts is high. The powder making effect of ordinary crushing means is not ideal. In addition, when preparing conventional meal replacement powders, red dates and walnuts are usually crushed directly or mixed with white sugar, other raw materials, etc. and crushed together. This crushing method adds unnecessary sugar and other mixtures. The prepared meal replacement powder has a poor flavor and high calories, which is inconsistent with the current dietary concept of most people. Therefore, it is urgent to develop a low-calorie meal replacement powder using red dates and walnuts as raw materials. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a low-calorie red dates and walnut meal replacement powder and a preparation method thereof. The prepared meal replacement powder can effectively retain the nutrients of red dates and walnuts, and has good powder dispersibility and good flavor.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The invention provides a low-calorie red date and walnut meal replacement powder, which is prepared from the following raw materials by weight: 30-40 parts of red date powder, 60-120 parts of walnut powder, 10-20 parts of cereal powder, 0-0.1 parts of sucralose and 0-0.02 parts of tert-butylhydroquinone; the cereal powder consists of black rice powder and red bean powder.

[0007] Preferably, the mass ratio of the black rice flour to the red bean flour is 2-4:1-3.

[0008] Preferably, the red date powder is 100-120 meshes, the walnut powder is 40-60 meshes, the black rice powder is 60-80 meshes, and the red bean powder is 60-80 meshes.

[0009] Preferably, the preparation method of the red date powder comprises the following steps: mixing red dates with 80% ethanol solution in a mass ratio of 1:3-5, soaking for 35-37 hours and then freeze-drying, and ultrafine grinding the dried red dates to obtain red date powder.

[0010] Preferably, the freeze-drying conditions are: cold hydrazine temperature -40°C, vacuum degree 0.012MPa, and drying for 24h.

[0011] Preferably, the water content of the dried red dates is 6%, the ultrafine grinding time is 6 minutes, and the filling amount of the ultrafine grinding is 300g / L.

[0012] Preferably, the preparation method of walnut powder comprises the following steps: drying, crushing and cold pressing walnut kernels to obtain walnut meal; mixing, soaking, pulping and grinding the walnut meal with water to obtain a walnut meal sample liquid; freeze-drying the walnut meal sample liquid and then ultrafine grinding it to obtain walnut powder.

[0013] Preferably, the solid-liquid ratio of the walnut meal to water is 1 g:10 mL, the soaking time is 60 min, the beating time is 5 to 10 min, and the grinding is performed by a colloid mill.

[0014] Preferably, the freeze-drying conditions are: cold hydrazine temperature -45°C, vacuum degree 0.07MPa, and drying for 24h; the ultrafine grinding is carried out using a ball mill, the ball-to-material mass ratio is 4, and the agitator speed is 600r / min.

[0015] The present invention also provides a preparation method of the low-calorie red date and walnut meal replacement powder, comprising the following steps: red date powder, walnut powder, black rice powder, red bean powder, sucralose and tertiary butylhydroquinone are uniformly mixed according to a mass ratio to obtain the low-calorie red date and walnut meal replacement powder.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] The present invention adopts the technology of nutrition preparation and flavor matching, reasonably proportions the raw and auxiliary materials, replaces sucrose with zero-calorie sugar, and adds functional auxiliary materials to obtain a low-calorie functional meal replacement powder with good rehydration performance, excellent flavor, and distinct unique taste and smell of red dates and walnuts. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : Effect of different solid-liquid ratios on particle size of red date powder.

[0019] Figure 2: Effects of different processing times on particle size of red date powder.

[0020] Figure 3 : Effect of different ethanol concentrations on particle size of red date ultrafine powder.

[0021] Figure 4 : Effect of crushing time on particle size of red date powder.

[0022] Figure 5 : Effect of filling amount on particle size of red date powder.

[0023] Figure 6 : Effect of water content on particle size of red date powder.

[0024] Figure 7 : Effect of drying technology on the collection rate of walnut powder. DETAILED DESCRIPTION

[0025] The present invention provides a low-calorie red date and walnut meal replacement powder, which is made of the following raw materials by mass: 30-40 parts of red date powder, 60-120 parts of walnut powder, 10-20 parts of cereal powder, 0-0.1 parts of sucralose and 0-0.02 parts of tert-butylhydroquinone; the cereal powder is composed of black rice powder and red bean powder. Preferably, the raw material composition of the low-calorie red date and walnut meal replacement powder of the present invention is: 35 parts of red date powder, 70-105 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tert-butylhydroquinone. The mass ratio of black rice powder and red bean powder of the present invention is 2-4:1-3, preferably 3:2.

[0026] The red date powder of the present invention is 100-120 meshes, preferably 110 meshes; the walnut powder is 40-60 meshes, preferably 50 meshes; the black rice powder is 60-80 meshes, preferably 70 meshes; the red bean powder is 60-80 meshes, preferably 70 meshes.

[0027] The preparation method of the red date powder of the present invention comprises the following steps: mixing the red dates with 80% ethanol solution in a mass ratio of 1:3-5, soaking for 35-37 hours and then freeze-drying, and ultrafine grinding the dried red dates to obtain the red date powder. The red dates of the present invention are pretreated before mixing with the 80% ethanol solution, and the pretreatment method is to remove the core and slice the red dates after washing. The soaking time of the red dates in the 80% ethanol solution of the present invention is preferably 36 hours, and the mass ratio of the red dates to the 80% ethanol solution is preferably 1:4; the preparation method of the 80% ethanol solution of the present invention can be selected as taking 80 ml of anhydrous ethanol into a measuring cylinder, and then adding distilled water to 100 ml. The red dates of the present invention are freeze-dried after soaking, and the freeze-drying conditions are: cold hydrazine temperature -40°C, vacuum degree 0.012MPa, and drying for 24 hours. The water content of the dried red dates of the present invention is 6%. The dried red dates of the present invention are ultrafinely ground, and the ultrafine grinding is carried out by a conventional ultrafine grinder in the art. The ultrafine grinding time is 6 minutes, the filling amount of the ultrafine grinding is 300g / L, and the red date powder obtained by grinding is 100-120 meshes.

[0028] The preparation method of walnut powder of the invention comprises the following steps: drying, crushing and cold pressing walnut kernels to obtain walnut meal; mixing, soaking, beating and grinding the walnut meal with water to obtain walnut meal sample liquid; freeze-drying the walnut meal sample liquid and then ultrafine crushing it to obtain walnut powder.

[0029] The present invention preferably washes, shells and peels to obtain peeled walnut kernels. The drying treatment of the walnut kernels of the present invention is preferably: after the walnuts are shelled and peeled, they are soaked in a mixed solution, and the soaked peeled walnut kernels are dried in an oven; the mixed solution is a mixed aqueous solution containing 3% sodium carbonate by mass and 7% calcium hydroxide by mass; the soaking temperature is 45-55°C, preferably 50°C; the soaking time is 2-4min, preferably 3min; the drying temperature is 55-65°C, preferably 60°C; the drying time is 11-13h, preferably 12h. The dried walnut kernels of the present invention are crushed and cold pressed, and the cold pressing treatment is preferably at a pressure of 42-46MPa and a temperature of ≤40°C, and the cold pressing is repeated 3 times to obtain walnut meal.

[0030] The present invention mixes, soaks, pulps and grinds walnut meal with water, wherein the solid-liquid ratio of the walnut meal to water is 1g:10mL, the soaking time is 60min, the pulping time is 5-10min, and the grinding is performed by a colloid mill, preferably the number of times of the colloid mill is 2-4 times.

[0031] The freeze-drying conditions of the walnut meal sample liquid of the present invention are: cold hydrazine temperature -45°C, vacuum degree 0.07MPa, and drying for 24h; the ultrafine grinding is carried out using a conventional ball mill in the art, the ball-to-material mass ratio is 4, the stirrer speed is 600r / min, and the walnut powder obtained by grinding is 40-60 mesh.

[0032] The invention grinds red dates and walnuts through ultrafine grinding technology, improves the physical and chemical properties (including solubility and water absorption) of red date powder and walnut powder on the basis of effectively maintaining stability, promotes the dissolution of bioactive substances in the red date powder and walnut powder, can retain the nutritional components of red dates and walnuts to the greatest extent, makes high-value use of red dates and walnuts, and makes the prepared meal replacement powder have good powder dispersibility, good rehydration performance, excellent flavor, and has obvious unique taste and smell of red dates and walnuts.

[0033] The present invention also provides a method for preparing the low-calorie red date and walnut meal replacement powder, comprising the following steps: according to the mass ratio, red date powder, walnut powder, black rice powder, red bean powder, sucralose and tertiary butyl hydroquinone are uniformly mixed to obtain the low-calorie red date and walnut meal replacement powder. The present invention adopts the nutrient blending and flavor matching technology, reasonably proportions the raw and auxiliary materials, replaces sucrose with zero-calorie sugar, and adds functional auxiliary materials to process and obtain a low-calorie functional meal replacement powder with good rehydration performance, excellent flavor, and a distinct and unique taste and smell of red dates and walnuts.

[0034] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the following embodiments, unless otherwise specified, all of them are conventional methods.

[0036] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0037] Example 1

[0038] Research on the crushing conditions of red dates:

[0039] 1. Methods for pretreatment of red dates

[0040] After washing, the red dates were pitted, cut into slices, and accurately weighed. Ethanol was used as the solvent to study the effects of solid-liquid ratio, pretreatment time, and ethanol concentration on the particle size of red date ultrafine powder.

[0041] Material-liquid ratio: Mix red dates with 80% (v / v) ethanol solution in mass ratios of 1:2, 1:3, 1:4, 1:5, and 1:6 (g / g), respectively, and soak at room temperature for 36 hours.

[0042] Pretreatment time: Red dates were mixed with 80% (v / v) ethanol solution in a mass ratio of 1:3 (g / g), and soaked at room temperature for 36, 48, 60, 72, and 84 h, respectively.

[0043] Ethanol concentration: Mix red dates with 50%, 60%, 70%, 80%, and 90% (v / v) ethanol solutions at a mass ratio of 1:3 (g / g), and soak at room temperature for 36 hours.

[0044] After the soaking treatment of each group of red dates was completed, excess water and ethanol were removed for drying, and the red dates were dried in an electric blast oven at a temperature of 60°C for 54 hours. The dried red date slices were placed in a universal grinder for 5 minutes to obtain red date coarse powder. The coarse powder was placed in a vibrating superfine grinder and crushed up and down for 5 minutes each, for a total of 10 minutes.

[0045] Particle size was measured by laser particle size analyzer: the powder was weighed and dissolved in 100 mL of pure water, stirred with a magnetic stirrer for 100 s, and then dripped into the instrument. The particle size (D 50 ). The result is Figure 1 to Figure 3 shown.

[0046] Depend on Figure 1 It can be seen that the increase in the material-liquid ratio leads to an increase in the dissolution rate of the substances in the red dates, which in turn causes the particle size of the red dates ultrafine powder to decrease. When the material-liquid ratio is 1:2, the powder particle size is relatively high, which is 61.09μm. The particle size of the red dates ultrafine powder is smaller between the material-liquid ratio of 1:3 and 1:5, and the particle size is 51.32μm when the material-liquid ratio is 1:3. As the material-liquid ratio increases, the powder adhesion phenomenon disappears during the powder making process. There is no wall adhesion phenomenon during the powder making process between the material-liquid ratio of 1:2 and 1:6, but the red dates ultrafine powder prepared with a material-liquid ratio of 1:2 absorbs moisture and hardens after being placed for 1h. Therefore, the material-liquid ratio of 1g:3g is the best condition.

[0047] Depend on Figure 2 It can be seen that the particle size of the powder shows a trend of first rising, then falling, and then rising again as the pretreatment time increases. When the pretreatment time is 36h (the starting point of the line graph in the figure), the particle size is 35.32μm. At 84h (the end point of the line graph in the figure), the powder particle size is 35.07μm. As the pretreatment time increases, the particle size increases. It may be that the increase in dissolved substances causes the heat generated by friction during the ultrafine grinding process to increase the particle size. Therefore, soaking for 36h is the best condition.

[0048] Depend on Figure 3It can be seen that when the ethanol concentration is between 50% and 80%, the particle size of the powder increases with the ethanol concentration, and the particle size decreases when the ethanol concentration is 90%. The ultrafine red date powder prepared when the ethanol concentration is between 50% and 80% does not show obvious moisture absorption and hardening during the storage process. When the ethanol concentration is 90%, the powder shows serious hardening and moisture absorption after being placed for 1 hour. This may be due to the increase in ethanol concentration, the dissolution rate of the substances in the red date gradually decreases, resulting in aggravated moisture absorption. Therefore, 80% ethanol solution is selected as the optimal condition.

[0049] 2. Research on ultrafine grinding technology of red dates

[0050] After washing, the red dates were pitted, cut into slices, and accurately weighed. The red dates were mixed with 80% (v / v) ethanol solution at a mass ratio of 1:3 (g / g) and soaked at room temperature for 36 hours. The effects of ultrafine grinding time, filling amount and moisture content of red dates on the particle size of ultrafine red date powder were studied.

[0051] Ultrafine grinding time of red dates: After the soaking treatment of red dates, remove excess water and ethanol to facilitate drying, and use freeze drying: cold hydrazine temperature -40℃, vacuum degree 0.012MPa, drying for 24h. The red dates are dried to a moisture content of 10%. The material filling amount is 400g / L, and the grinding times are 0, 2, 4, 6, 8, and 10min respectively.

[0052] Ultrafine grinding filling amount of red dates: After the red dates are soaked, remove excess water and ethanol to facilitate drying, and use freeze drying: cold hydrazine temperature -40℃, vacuum degree 0.012MPa, drying for 24h. The red dates are dried to a moisture content of 10%. The material filling amounts are 100, 200, 300, 400, 500, and 600g / L respectively, and crushed for 6min.

[0053] Moisture content of red dates: After the red dates are soaked, excess water and ethanol are removed to facilitate drying. Freeze drying is used: cold hydrazine temperature -40℃, vacuum degree 0.012MPa, drying for 24h. The red dates are dried to moisture contents of 2%, 4%, 6%, 8%, 10%, and 12%, respectively. The material filling amount is 400g / L, respectively, and crushed for 6min.

[0054] Particle size was measured by laser particle size analyzer: the powder was weighed and dissolved in 100 mL of pure water, stirred with a magnetic stirrer for 100 s, and then dripped into the instrument. The particle size (D 50 ). The result is Figures 4 to 6 shown.

[0055] Depend on Figure 4It can be seen that with the extension of the crushing time from 0 to 6 minutes, the crushed particle size decreases and reaches 23.88μm; when the crushing time exceeds 6 minutes, the crushed particle size does not change significantly. Therefore, the crushing time of 6 minutes is the best condition.

[0056] Depend on Figure 5 It can be seen that when the filling amount is 100-300g / L, the particle size gradually decreases with the increase of the filling amount. When the filling amount is greater than 300g / L, the particle size does not change significantly. This is because the material filling amount is too small, and it is difficult for the materials to collide effectively. Therefore, a filling amount of 300g / L is the best condition.

[0057] Depend on Figure 6 It can be seen that the greater the moisture content of the material, the larger the particle size, because the greater the moisture content, the less brittle the material is, and it is not easy to break under the action of mechanical force. However, when the moisture content is lower than 6%, the difference in particle size is not significant. Considering that it is difficult to continue to reduce the moisture content after drying to a certain extent, it is more appropriate to choose a moisture content of 6%.

[0058] The process parameters were optimized by orthogonal experiment with three factors and three levels. The factor level design table is shown in Table 1, the analysis scheme and results are shown in Table 2, and the experimental variance analysis results are shown in Table 3.

[0059] Table 1 Orthogonal experimental factors and level design of ultrafine grinding of red dates

[0060] level A Crushing time / min B filling amount / (g / L) C moisture content / % -1 4 200 5 0 6 300 6 1 8 400 7

[0061] Table 2 Results and analysis of orthogonal test of ultrafine grinding of red dates

[0062]

[0063] Table 3 Analysis of variance of orthogonal test for ultrafine grinding of red dates

[0064] Sources of variance sum of squares Degrees of Freedom Mean Square F-number Significance Model 159.08 9 17.68 36.99 Very significant A 3.42 1 3.42 7.15 Significant B 1.35 1 1.35 2.83 C 3.20 1 3.20 6.69 AB 16.73 1 16.73 35.01 Very significant AC 4.47 1 4.47 9.36 Significant BC 3.86 1 3.86 8.08 Significant A2 34.51 1 34.51 72.22 Very significant B2 40.93 1 40.93 85.56 Very significant C2 40.22 1 40.22 84.16 Very significant Residual 3.35 7 0.48 Lack of Fit 2.45 3 0.82 3.64 Not significant Net Error 0.90 4 0.22 Total error 142.43 16

[0065] From Tables 1 to 3, we can see that according to the orthogonal significance test results, the best crushing process is crushing time 6min, filling amount 300g / L, moisture content 6%, at which time the crushed particle size D 50 It is 16.07μm.

[0066] Example 2

[0067] Research on the selection of walnut drying technology:

[0068] The walnuts were washed, shelled and peeled, and soaked in a mixed aqueous solution containing 3% sodium carbonate and 7% calcium hydroxide at a temperature of 50°C for 3 minutes to obtain peeled walnut kernels. The peeled walnut kernels were placed in an oven at 60°C and dried for 12 hours. After crushing, the oil was extracted by cold pressing at a pressure of 45MPa and a temperature of 35°C. The cold pressing was repeated 3 times to obtain walnut meal. The walnut meal was weighed, and distilled water was added at a solid-liquid ratio of 1g:10mL to soak for 60 minutes. The pulping was performed for 6 minutes until the pulp was fine, and the material sample liquid was obtained by colloid grinding twice. The effects of various drying techniques on the protein powder content (powder collection rate) in walnut powder were studied.

[0069] The determined process conditions are as follows:

[0070] Hot air drying: Place the sample liquid in a stainless steel plate with a thickness of about 0.5 cm and dry it in an electric hot air drying oven at 45°C for 36 hours;

[0071] Heat pump drying: Place the sample liquid in a stainless steel plate with a thickness of about 0.5 cm and dry it in a solar heat pump drying room at 45°C for 30 hours;

[0072] Freeze drying: Place the sample liquid in a stainless steel plate with a thickness of about 0.5 cm, pre-freeze at -80°C for 24 hours, and dry it at a cold hydrazine temperature of -45°C and a vacuum degree of 0.07 MPa for 24 hours;

[0073] Spray drying: the material sample liquid is sprayed at an inlet temperature of 140°C and a fan air volume of 2.5m 3 / min and spray drying was carried out under the conditions of injection rate of 12mL / min.

[0074] The powder collection rate is calculated as the ratio of the mass of the prepared walnut protein powder to the mass of the walnut meal raw material. The formula is: powder collection rate / % = m2 / m1×100, where: m1 is the mass of walnut meal / g; m2 is the mass of the collected walnut powder / g. Each treatment was repeated 3 times and the average value was calculated. The experimental results are shown in Figure 7 .

[0075] Depend on Figure 7 It can be seen that the effects of different drying technologies on powder collection rates are significantly different. The powder collection rates of the drying methods from high to low are: freeze drying > hot air drying > heat pump drying > spray drying. During the freeze drying process, the material is in a static state, and the loss of protein powder after drying is small, so the powder collection rate is the highest, which is 31.05%; the materials in hot air drying and heat pump drying are affected by the wind speed, and there is a certain loss of the product; and in the spray drying process, some materials have a wall-adhering phenomenon and are wasted, so the powder collection rate is the lowest, which is only 25.27%.

[0076] The physical and chemical indexes of the dried walnut powder in each group were tested according to the national standard, and the results are shown in Table 4.

[0077] Table 4 Effect of drying process on main nutritional indexes of walnut powder

[0078] index Hot air drying Heat pump drying Freeze drying Spray drying Moisture / % 4.15±0.15 3.84±0.29 3.29±0.15 4.33±0.21 Ash / % 2.13±0.13 2.06±0.17 1.63±0.16 1.87±0.30 Fat / % 8.92±0.18 8.54±0.26 7.85±0.38 8.06±0.26 protein / % 73.8±0.52 83.25±0.11 86.9±0.10 85.7±0.08

[0079] It can be seen from the above table that the moisture mass fraction of walnut powder prepared by the four drying technologies is between 3.29% and 4.33%, all lower than 5%, indicating that the four drying methods can achieve good results. The moisture mass fraction of the products is ranked from low to high as follows: freeze drying < heat pump drying < hot air drying < spray drying. The moisture mass fraction of walnut powder prepared by freeze drying is the lowest, which is 3.29%, significantly lower than the other three drying technologies, while the moisture mass fraction of walnut powder prepared by spray drying is the highest, which is 4.33%, which is not conducive to product storage. The effects of different drying technologies on the protein quality fraction of walnut powder are significantly different. The protein quality fraction of the products is ranked from high to low as follows: freeze drying > spray drying > heat pump drying > hot air drying. The protein quality fraction of walnut powder prepared by freeze drying is as high as 86.90%, followed by 85.70% of spray drying. Freeze drying is carried out under low temperature and vacuum conditions, and the protein structure is relatively stable, so that the protein is better retained; the instantaneous high temperature of spray drying causes a small amount of heat-sensitive protein to denature, resulting in a decrease in its mass fraction; and long-term heating by heat pump and hot air drying will cause more protein denaturation; the fat and ash mass fractions of walnut powder prepared by different drying technologies are ranked consistently, from low to high in the order of freeze drying < spray drying < heat pump drying < hot air drying, among which the fat and ash mass fractions of walnut powder obtained by freeze drying are the lowest, which are 7.85% and 1.63%, respectively.

[0080] Water absorption refers to the ability of dry products to absorb moisture from the surrounding environment during storage. Products with high water absorption are prone to powder deliquescence and agglomeration, which reduces the physical, chemical and biological stability of the product, thereby affecting product quality and shelf life. Wettability is a key indicator for evaluating the dissolution performance of walnut powder. The shorter the wetting and sinking time of the powder in distilled water, the faster the product can diffuse in water and has good dissolution. The water absorption and wettability of each group of dried walnut powder were tested according to the national standard. The results are shown in Table 5.

[0081] Table 5 Effect of drying process on water absorption of walnut powder

[0082] index Hot air drying Heat pump drying Freeze drying Spray drying Water absorption / % 1.27±0.09 1.51±0.16 1.93±0.12 2.34±0.18 Wettability / s 238.96±11.34 216.87±6.32 163.52±4.16 146.42±10.32

[0083] As can be seen from the table above, the water absorption rate of walnut powder obtained by different drying technologies is spray drying>freeze drying>heat pump drying>hot air drying. Among them, the walnut powder obtained by spray drying has the highest water absorption capacity, reaching 2.34%, which is significantly higher than the other three drying technologies, followed by freeze drying, and heat pump drying and hot air drying are smaller, and the difference between the two is not significant. Spray-dried walnut powder has a small particle size, a large specific surface area, and strong water absorption, so the packaging of the product should choose appropriate methods and materials; the walnut powder prepared by freeze drying may form a pore structure, the particles are loose, and it is easy to absorb water, which may also be related to the type and content of sugar in the product; the walnut powder is affected by hot air for a long time during the hot air and heat pump drying process, the surface shrinks sharply, the pore passage is blocked, and the water absorption rate is low. The wettability of spray-dried walnut powder is the smallest (146.42s), which is not significantly different from the freeze-dried group (163.52s). This may be because the walnut powder prepared by spray drying has a smaller particle size and uniform size, which is conducive to water adsorption and flow, while the freeze-dried powder has a loose structure and thus low wettability. The wettability of walnut powder dried by heat pump and hot air is significantly higher than that of the spray and freeze-dried groups, which may be related to their larger particle size, uneven size, and blocked surface pore passages.

[0084] Taking all factors into consideration, freeze drying is the best method to obtain walnut powder.

[0085] Example 3

[0086] A low-calorie red date and walnut meal replacement powder is prepared from the following raw materials by weight: 40 parts of red date powder, 80 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tertiary butyl hydroquinone. The cereal powder is composed of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2.

[0087] Preparation method of red date powder: After washing the red dates, remove the core, cut into slices, weigh the red dates, use 80% ethanol solution as solvent, mix the red dates with 80% ethanol solution in a mass ratio of 1:3, and soak at room temperature for 36 hours. After soaking, remove excess water and ethanol, cool at -40°C, vacuum 0.012MPa, and dry for 24 hours. Then, place in an ultrafine grinder with a filling amount of 300g / L and grind for 6 minutes, and the red date powder obtained by grinding is 110 mesh.

[0088] Preparation method of walnut powder: walnuts are washed, shelled and peeled, and soaked in a mixed aqueous solution containing 3% sodium carbonate and 7% calcium hydroxide by mass fraction at a temperature of 50°C for 3 minutes to obtain peeled walnut kernels. The peeled walnut kernels are placed in an oven at 60°C and dried for 12 hours. After crushing, cold pressing is performed to extract oil, with a cold pressing pressure of 45MPa and a cold pressing temperature of 35°C, and cold pressing is performed 3 times to obtain walnut meal. Weigh the walnut meal, add distilled water according to a material-liquid ratio of 1g:10mL, soak for 60 minutes, beat for 6 minutes until the slurry is fine, and grind twice through a colloid mill to obtain a material sample liquid. The material sample liquid is placed in a stainless steel plate with a thickness of about 0.5cm, pre-frozen at -80°C for 24 hours, and dried for 24 hours under the conditions of a cold hydrazine temperature of -45°C and a vacuum degree of 0.07MPa. Then a ball mill is used for crushing, the ball-to-material mass ratio is 4, the stirrer speed is 600r / min, and the walnut powder obtained by crushing is 50 mesh.

[0089] Preparation of low-calorie red date and walnut meal replacement powder: black rice and red bean are crushed to 70 meshes respectively. Red date powder, walnut powder, black rice powder, red bean powder, sucralose and tertiary butyl hydroquinone are mixed evenly according to the mass ratio to obtain low-calorie red date and walnut meal replacement powder.

[0090] Example 4

[0091] A low-calorie red date and walnut meal replacement powder is prepared from the following raw materials by weight: 30 parts of red date powder, 90 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tertiary butyl hydroquinone. The cereal powder is composed of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 1:1.

[0092] Preparation method of red date powder: same as Example 3.

[0093] Preparation method of walnut powder: same as Example 3.

[0094] Preparation of low-calorie red date and walnut meal replacement powder: black rice is crushed to 60 mesh; red bean is crushed to 80 mesh. Red date powder, walnut powder, black rice powder, red bean powder, sucralose and tertiary butyl hydroquinone are mixed evenly according to the mass ratio to obtain low-calorie red date and walnut meal replacement powder.

[0095] Example 5

[0096] A low-calorie red date and walnut meal replacement powder is prepared from the following raw materials by weight: 35 parts of red date powder, 90 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tertiary butyl hydroquinone. The cereal powder is composed of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2.

[0097] Preparation method of red date powder: same as Example 3.

[0098] Preparation method of walnut powder: same as Example 3.

[0099] Preparation of low-calorie red date and walnut meal replacement powder: black rice is crushed to 80 mesh; red bean is crushed to 60 mesh. Red date powder, walnut powder, black rice powder, red bean powder, sucralose and tertiary butyl hydroquinone are mixed evenly according to the mass ratio to obtain low-calorie red date and walnut meal replacement powder.

[0100] Example 6

[0101] Effect of the addition amount of red date powder and walnut powder on sensory scores:

[0102] Experimental group 1 (red date powder: walnut powder = 1:5): 30 parts of red date powder, 150 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tert-butylhydroquinone. The cereal powder consists of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2. The preparation method is the same as that of Example 3.

[0103] Experimental group 2 (red date powder: walnut powder = 1:3): 30 parts of red date powder, 90 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tert-butylhydroquinone. The cereal powder consists of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2. The preparation method is the same as that of Example 3.

[0104] Experimental group 3 (red date powder: walnut powder = 2:5): 30 parts of red date powder, 75 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tert-butylhydroquinone. The cereal powder consists of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2. The preparation method is the same as that of Example 3.

[0105] Experimental group 4 (red date powder: walnut powder = 1:2): 30 parts of red date powder, 60 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tert-butylhydroquinone. The cereal powder consists of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2. The preparation method is the same as that of Example 3.

[0106] Experimental group 5 (red date powder: walnut powder = 3:5): 30 parts of red date powder, 50 parts of walnut powder, 15 parts of cereal powder, 0.005 parts of sucralose and 0.015 parts of tert-butylhydroquinone. The cereal powder consists of black rice powder and red bean powder, and the mass ratio of black rice powder to red bean powder is 3:2. The preparation method is the same as that of Example 3.

[0107] Twenty sensory evaluators were selected, half of them were male and half were female, aged 19 to 23 years old, and the red dates and walnut meal replacement powders prepared in the above groups were subjected to sensory evaluation based on five indicators: flavor (20 points), tissue morphology (15 points), color (15 points), mouthfeel (30 points) and reconstitution (20 points) according to the score ratio. The prepared meal replacement powders were reconstituted with 80℃ hot water at a ratio of 1:6 (g / mL). The evaluation criteria are shown in Table 6.

[0108] Table 6 Sensory scoring standards

[0109]

[0110] The score of experimental group 1 was 82 points, the score of experimental group 2 was 91 points, the score of experimental group 3 was 93 points, the score of experimental group 4 was 94 points, and the score of experimental group 5 was 76 points. The results showed that the red date powder: walnut powder was between 1:2 and 3, and the flavor was good. The sensory score of the low-calorie red date walnut meal replacement powder prepared by the scheme of the present invention was above 90 points.

[0111] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low-calorie red dates and walnut meal replacement powder, characterized in that: The invention is prepared from the following raw materials by weight: 30-40 parts of red date powder, 60-120 parts of walnut powder, 10-20 parts of cereal powder, 0-0.1 parts of sucralose and 0-0.02 parts of tert-butylhydroquinone; the cereal powder is composed of black rice powder and red bean powder.

2. The low-calorie red dates and walnut meal replacement powder according to claim 1, characterized in that: The mass ratio of the black rice flour to the red bean flour is 2-4:1-3.

3. The low-calorie red dates and walnut meal replacement powder according to claim 1, characterized in that: The red date powder is 100-120 meshes, the walnut powder is 40-60 meshes, the black rice powder is 60-80 meshes, and the red bean powder is 60-80 meshes.

4. The low-calorie red dates and walnut meal replacement powder according to claim 1, characterized in that: The preparation method of the red date powder comprises the following steps: mixing red dates with 80% ethanol solution at a mass ratio of 1:3-5, soaking for 35-37 hours and then freeze-drying, and ultrafine grinding the dried red dates to obtain the red date powder.

5. The low-calorie red dates and walnut meal replacement powder according to claim 4, characterized in that: The freeze-drying conditions are: cold hydrazine temperature -40°C, vacuum degree 0.012MPa, and drying for 24h.

6. The low-calorie red dates and walnut meal replacement powder according to claim 4, characterized in that: The water content of the dried red dates is 6%, the ultrafine grinding time is 6 minutes, and the filling amount of the ultrafine grinding is 300g / L.

7. The low-calorie red dates and walnut meal replacement powder according to claim 1, characterized in that: The preparation method of walnut powder comprises the following steps: drying, crushing and cold pressing walnut kernels to obtain walnut meal; mixing, soaking, beating and grinding the walnut meal with water to obtain walnut meal sample liquid; freeze-drying the walnut meal sample liquid and then ultrafine grinding it to obtain walnut powder.

8. The low-calorie red dates and walnut meal replacement powder according to claim 7, characterized in that: The solid-liquid ratio of the walnut meal to water is 1 g:10 mL, the soaking time is 60 min, the beating time is 5 to 10 min, and the grinding is performed by a colloid mill.

9. The low-calorie red dates and walnut meal replacement powder according to claim 7, characterized in that: The freeze-drying conditions are: cold hydrazine temperature -45°C, vacuum degree 0.07MPa, and drying for 24h; the ultrafine grinding is carried out by a ball mill, the ball-to-material mass ratio is 4, and the stirrer speed is 600r / min.

10. The method for preparing the low-calorie red date and walnut meal replacement powder according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: red date powder, walnut powder, black rice powder, red bean powder, sucralose and tertiary butylhydroquinone are uniformly mixed according to the mass ratio to obtain low-calorie red date and walnut meal replacement powder.

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