Preparation method of vacuum low-temperature continuous drying Chinese wolfberry fruit powder

Abstract

The invention discloses a preparation method of vacuum low-temperature continuous drying Chinese wolfberry fruit powder, relates to the technical field of Chinese wolfberry fruit product processing, and aims to solve the problems of high energy consumption, long time consumption and high drying cost of a traditional drying method. According to the technical scheme, the preparation method is characterized by comprising the steps of raw material preparation, feeding, material distribution, vacuumizing, heating, drying, low-temperature cooling, discharging, smashing, screening, packaging, inspecting and warehousing, the Chinese wolfberry primary pulp is directly adopted for low-temperature drying, loss of characteristic nutritional ingredients such as Chinese wolfberry polysaccharide, total phenols and vitamins in the material can be reduced to the maximum extent in the drying process, and the quality of the Chinese wolfberry is improved. The method has the drying quality of short time consumption, continuous drying, uniform heating and the like, and solves the problems that products in batches have certain differences, the loss of characteristic components is large, the energy consumption is high, the time consumption is long, the drying cost is high and the like when vacuum freeze drying is carried out in batches at present. The problem that nutritional ingredients, color and luster cannot be guaranteed due to high drying temperature of spray drying is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of wolfberry product processing, in particular to a method for preparing wolfberry powder continuously dried at a low temperature and in a vacuum. Background Art

[0002] As a Ningxia specialty medicinal material and tonic that is both edible and medicinal, wolfberry has the effects of nourishing the liver and kidneys, nourishing the liver and improving eyesight, and strengthening the body. Modern pharmacology shows that wolfberry contains wolfberry polysaccharides, betaine, flavonoids, carotenoids, amino acids, vitamins and trace elements, and has the effects of enhancing immunity, anti-tumor, anti-aging, lowering blood sugar and lowering blood lipids.

[0003] As an emerging product obtained directly from freshly squeezed wolfberries, wolfberry puree fully retains the nutritional components of fresh wolfberry fruits, is easier to be absorbed and utilized by the human body, and is widely favored by consumers. However, wolfberry puree also has the problems of being inconvenient to transport and carry, and having a short shelf life. In order to apply wolfberry to the fields of food, medical treatment, and beauty products, there is an increasingly urgent need for wolfberry powder as a formula ingredient that can fully retain the nutritional components of wolfberry, is easy to carry, has a long shelf life, and can be fully absorbed by the human body. Therefore, based on the existing reality, the present invention selects wolfberry puree that has been mass-produced and stored in Ningxia as a raw material, and performs vacuum low-temperature continuous belt drying, which can realize continuous drying of wolfberry powder and ensure its drying quality, and can ensure a stable and economical supply of wolfberry powder while saving costs and resources.

[0004] After searching, the Chinese patent with the existing application publication number CN102132879A discloses a "processing technology of vacuum freeze-dried wolfberry powder", which uses vacuum freeze-drying technology to dry fresh wolfberry fruit, thereby retaining the nutritional components, appearance color and flavor of the fresh wolfberry fruit to the greatest extent.

[0005] However, fresh wolfberry fruits are not suitable for storage and long-distance transportation after picking, and fresh fruits are only available for picking from July to October each year, which is not conducive to the long-term stable production and supply of wolfberry powder. In addition, the drying method is batch drying, and there will be certain differences between batches of products. In addition, it has high energy consumption, long time consumption and high drying cost.

[0006] In summary, the present invention provides a method for preparing wolfberry powder by vacuum low-temperature continuous drying to solve the above problems. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing wolfberry powder by vacuum low-temperature belt continuous drying, which has the advantages of less loss of characteristic nutritional components, maintaining the bright color of wolfberry powder, and good appearance quality and taste. The method has the advantages of ensuring the quality of wolfberry powder while solving the market problem of stable and economical supply of wolfberry powder. Compared with other drying methods such as vacuum freeze drying and spray drying, the method has the characteristics of less loss of characteristic components, less loss of heat-labile components and aroma, short drying time, low material loss, low energy consumption, etc.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing wolfberry powder by vacuum low-temperature continuous drying, comprising:

[0010] Step 1: Material preparation: prepare high-quality wolfberry raw materials and process them;

[0011] Step 2: Vacuuming: Set the vacuum degree to 1.0-2.5 kPa and start vacuuming to facilitate the subsequent heating to reach the boiling point of the material faster;

[0012] Step 3: Heating: In a vacuum environment, gradually heat to promote the evaporation of water;

[0013] Step 4, drying: keep the vacuum degree at 1.0-2.5kpa, when the temperature of the heating pipe rises to 85-95℃, the temperature of the wolfberry puree is about 40-55℃, at which time the wolfberry puree is in a boiling state, continue drying for 45-60 minutes to evaporate all the water;

[0014] Step 5: Low temperature cooling: After drying, set the pipeline temperature to 15-20°C for low temperature cooling. When the material temperature reaches 20-25°C, it is ready to be discharged.

[0015] Step 6: Discharging: temporarily store the cooled semi-finished wolfberry powder in a storage tank. After all the products in the same batch are finished, open the vacuum valve, switch the material valve, and send the dry powder to the receiving barrel for subsequent crushing;

[0016] Step 7: Grinding: Grinding the dried wolfberries to achieve the required powder fineness;

[0017] Step 8. Processing and collection: The crushed products are screened and packaged for storage.

[0018] By adopting the above technical scheme, the vacuum degree, drying temperature and drying time in the drying process are studied. The drying temperature is controlled at 40-55°C, the vacuum degree is 1.0-2.5KPa, and the drying time is 45-60 minutes. The loss of characteristic components in the wolfberry powder drying process can be relatively reduced.

[0019] The present invention is further configured as follows: the material preparation in step 1 specifically comprises the following steps:

[0020] Step S1, raw material preparation: receiving qualified wolfberry puree, and checking whether the production date, certificate of conformity, physical and chemical indicators and other information meet the processing requirements;

[0021] Step S2, feeding: Turn on the feeding screw pump switch, and pump the prepared wolfberry puree into the puree storage tank through the pump. The storage tank must be kept clean and not contaminated;

[0022] Step S3, cloth: Spread the wolfberries evenly to ensure even heat distribution during the drying process.

[0023] By adopting the above technical solution, the quality of wolfberry is guaranteed and work preparation is carried out.

[0024] The present invention is further configured as follows: the spreading of step S3 specifically includes: adjusting the frequency of the spreading motor to 35HZ, turning on the motor, turning on the conveyor belt of the drying bed, and evenly spreading the wolfberry puree in the storage tank on the drying bed of the vacuum low-temperature continuous belt drying equipment through the spreading device. The thickness of the cloth is observed at any time during the spreading process, and the material thickness should be maintained at about 1 cm.

[0025] By adopting the above technical solution, the drying quality can be improved conveniently.

[0026] The present invention is further configured as follows: the heating in step three specifically includes: setting the temperature of the temperature pipe to 85-95°C, starting steam heating, so that the wolfberry puree is continuously heated by steam heating of the heating pipe in a vacuum environment, and at the same time observing whether the cooling equipment operates smoothly and whether there are any abnormalities, and visually inspecting whether the cooling water is short of water during vacuum. If it is lower than or close to the standard line, water is replenished in time.

[0027] By adopting the above technical solution, the risk of equipment abnormality and product quality caused by excessive temperature can be avoided.

[0028] The present invention is further configured as follows: the crushing in step seven specifically includes: under a low temperature state (less than 20° C.), the speed of the crusher is controlled at 3500-4000 r / min, and the dried semi-finished wolfberry powder is crushed by the crusher, and the speed shall not be higher than 4000 r / min.

[0029] By adopting the above technical solution, the loss of nutrients in wolfberry powder or the phenomenon of machine sticking due to excessively high rotation speed can be avoided.

[0030] The present invention is further configured as follows: the processing and collection of step eight specifically includes the following steps:

[0031] Step K1, sieving: passing the crushed product through sieves of different mesh sizes to obtain wolfberry powder of different mesh sizes ranging from 80 to 200 meshes;

[0032] Step K2, packaging: packaging the qualified wolfberry powder for storage and transportation;

[0033] Step K3, inspection: Inspect according to Q / QZTS 0004S-2023, and issue a certificate of conformity after passing;

[0034] Step K4, storage: After the inspection, the products are stored in a dedicated area away from walls and the ground. The humidity in the warehouse should be below 60%.

[0035] By adopting the technical solution, the wolfberry powder after the crushing process is screened to improve the quality of the wolfberry powder.

[0036] The present invention is further configured as follows: the packaging in step eleven specifically includes: after the sieved dry powder meets the standard requirements, vacuum packaging of different specifications is performed in a purification workshop according to customer needs, and it should be noted that the humidity should not exceed 45% during packaging.

[0037] By adopting the above technical solution, the dry powder can be prevented from agglomerating due to moisture and causing quality changes.

[0038] In summary, the beneficial technical effects of the present invention are:

[0039] 1. A method for preparing wolfberry powder by vacuum low-temperature continuous drying of the present invention directly uses wolfberry pulp for low-temperature drying. During the drying process, the loss of characteristic nutrients in the material, such as wolfberry polysaccharides, total phenols, and vitamins, can be reduced to the greatest extent, and the loss of heat-volatile components and aroma can be reduced. In addition, the method has the advantages of short drying time, continuous drying, uniform heating, and the like. The method solves the problems of batch drying in vacuum freeze drying, certain differences between batches of products, large loss of characteristic components, high energy consumption, long drying time, and high drying cost, and solves the problems of spray drying that cannot guarantee nutrients and color due to high drying temperature.

[0040] 2. The present invention studies the vacuum degree, drying temperature and drying time during the drying process, and controls the drying temperature at 40-55°C, the vacuum degree at 1.0-2.5KPa and the drying time at 45-60 minutes, thereby relatively reducing the loss of characteristic components of wolfberry powder during the drying process. At the same time, the characteristic nutrient content of wolfberry powder obtained by different drying methods is analyzed and compared, and the results show that vacuum low-temperature drying can minimize the loss of characteristic nutrient components such as wolfberry polysaccharides, total phenols and vitamins during the drying process of wolfberry powder compared with spray drying and vacuum freeze drying.

[0041] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described below are only some embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0043] In the figure:

[0044] Figure 1 It is a schematic diagram of the process of the present invention;

[0045] Figure 2 It is a schematic diagram of the glucose standard curve in the present invention;

[0046] Figure 3 Schematic diagram of the polysaccharide content of wolfberry powder in different drying methods in the present invention;

[0047] Figure 4 Schematic diagram of gallic acid standard curve in the present invention;

[0048] Figure 5 Schematic diagram showing the comparison of the total phenolic content of wolfberry powder in different drying methods in the present invention;

[0049] Figure 6 This is a schematic diagram of the standard curve of vitamin B1 in the present invention;

[0050] Figure 7 It is a schematic diagram of the standard curve of vitamin B2 in the present invention. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0052] Vacuum low-temperature continuous belt drying can continuously feed and discharge materials. Its principle is to use the boiling point of water under low pressure to lower, and cooperate with vacuum dryer to dehydrate raw materials with a certain amount of free water. The dried material is placed in a closed drying chamber and evacuated with a vacuum pump; at the same time, the dried material is continuously heated to make the water in the material boil and evaporate at a lower temperature (below 60°C). Compared with the usual drying methods, such as spray drying and vacuum freeze drying, vacuum low-temperature continuous belt drying technology dries at low temperature with very little oxygen, and can dry materials that are easy to oxidize and change color. Especially in the drying process, compared with vacuum freezing and spray drying, it can significantly reduce the loss of characteristic nutrients in the material, such as wolfberry polysaccharides, total phenols, and vitamins, and reduce the loss of heat-sensitive components and aroma. At the same time, in the vacuum low-temperature drying process, the material can be continuously discharged, the heating area is uniform, and the original color, aroma, taste, and shape of the material can be best maintained to ensure the drying quality.

[0053] Embodiment 1

[0054] Raw material preparation: Get qualified wolfberry puree and check whether the production date, certificate of conformity, physical and chemical indicators and other information meet the processing requirements;

[0055] Feeding: Turn on the feeding screw pump switch and pump the prepared wolfberry puree into the puree storage tank through the pump. The storage tank must be kept clean and free of contamination;

[0056] Fabric distribution: adjust the frequency of the fabric distribution motor to 35HZ, turn on the motor, turn on the conveyor belt of the drying bed, and evenly spread the wolfberry puree in the storage tank on the drying bed of the vacuum low-temperature continuous belt drying equipment through the fabric distribution device. Observe the fabric thickness at any time during the fabric distribution process. The material thickness should be kept at about 1cm;

[0057] Vacuuming: Set the vacuum degree to 1.0-1.5 kPa and start vacuuming to facilitate subsequent heating to reach the boiling point of the material faster;

[0058] Heating: Set the temperature of the temperature pipe to 85-95℃, start steam heating, and make the wolfberry puree continue to heat up through the steam heating of the heating pipe in a vacuum environment. At the same time, observe whether the cooling equipment operates smoothly and whether there is any abnormality. Visually check whether the cooling water is short of water during vacuum. If it is lower than or close to the standard line, replenish water in time to avoid abnormal equipment and product quality risks caused by excessive temperature;

[0059] Drying: Keep the vacuum degree at 1.0-1.5kpa. When the temperature of the heating pipe rises to 85-95℃, the temperature of the wolfberry puree is about 50-55℃. At this time, the wolfberry puree is in a boiling state. Continue drying for 55-60 minutes to evaporate all the water.

[0060] Low temperature cooling: After drying, set the pipeline temperature to 15-20℃ for low temperature cooling. When the material temperature reaches 20-25℃, it is ready to be discharged.

[0061] Discharging: temporarily store the cooled semi-finished wolfberry powder in the storage tank. When all the products in the same batch are finished, open the vacuum valve, switch the material valve, and send the dry powder to the receiving barrel for subsequent crushing;

[0062] Crushing: Under low temperature (less than 20℃), the speed of the crusher is controlled at 3500-4000r / min, and the dried semi-finished wolfberry powder is crushed by the crusher. The speed should not be higher than 4000r / min to avoid the loss of nutrients in the wolfberry powder or sticking to the machine due to excessive speed;

[0063] Sieving: The crushed product is passed through sieves of different mesh sizes to obtain wolfberry powder of different mesh sizes ranging from 80 to 200;

[0064] Packaging: After the sieved dry powder meets the standard requirements, it will be vacuum packed in different specifications according to customer needs in the clean room. When packaging, it should be noted that the humidity should not exceed 45% to prevent the dry powder from getting damp and agglomerating, resulting in quality changes.

[0065] Embodiment 2

[0066] Raw material preparation: Get qualified wolfberry puree and check whether the production date, certificate of conformity, physical and chemical indicators and other information meet the processing requirements;

[0067] Feeding: Turn on the feeding screw pump switch and pump the prepared wolfberry puree into the puree storage tank through the pump. The storage tank must be kept clean and free of contamination;

[0068] Fabric distribution: adjust the frequency of the fabric distribution motor to 35HZ, turn on the motor, turn on the conveyor belt of the drying bed, and evenly spread the wolfberry puree in the storage tank on the drying bed of the vacuum low-temperature continuous belt drying equipment through the fabric distribution device. Observe the fabric thickness at any time during the fabric distribution process. The material thickness should be kept at about 1cm;

[0069] Vacuuming: Set the vacuum degree to 1.5-2.0 kPa and start vacuuming to facilitate subsequent heating to reach the boiling point of the material faster;

[0070] Heating: Set the temperature of the temperature pipe to 85-95℃, start steam heating, and make the wolfberry puree continue to heat up through the steam heating of the heating pipe in a vacuum environment. At the same time, observe whether the cooling equipment operates smoothly and whether there is any abnormality. Visually check whether the cooling water is short of water during vacuum. If it is lower than or close to the standard line, replenish water in time to avoid abnormal equipment and product quality risks caused by excessive temperature;

[0071] Drying: Keep the vacuum degree at 1.5-2.0kpa. When the temperature of the heating pipe rises to 85-95℃, the temperature of the wolfberry puree is about 45-50℃. At this time, the wolfberry puree is in a boiling state. Continue drying for 50-55 minutes to evaporate all the water.

[0072] Low temperature cooling: After drying, set the pipeline temperature to 15-20℃ for low temperature cooling. When the material temperature reaches 20-25℃, it is ready to be discharged.

[0073] Discharging: temporarily store the cooled semi-finished wolfberry powder in the storage tank. When all the products in the same batch are finished, open the vacuum valve, switch the material valve, and send the dry powder to the receiving barrel for subsequent crushing;

[0074] Crushing: Under low temperature (less than 20℃), the speed of the crusher is controlled at 3500-4000r / min, and the dried semi-finished wolfberry powder is crushed by the crusher. The speed should not be higher than 4000r / min to avoid the loss of nutrients in the wolfberry powder or sticking to the machine due to excessive speed;

[0075] Sieving: The crushed product is passed through sieves of different mesh sizes to obtain wolfberry powder of different mesh sizes ranging from 80 to 200;

[0076] Packaging: After the sieved dry powder meets the standard requirements, it will be vacuum packed in different specifications according to customer needs in the clean room. When packaging, it should be noted that the humidity should not exceed 45% to prevent the dry powder from getting damp and agglomerating, resulting in quality changes.

[0077] Embodiment 3

[0078] Raw material preparation: Get qualified wolfberry puree and check whether the production date, certificate of conformity, physical and chemical indicators and other information meet the processing requirements;

[0079] Feeding: Turn on the feeding screw pump switch and pump the prepared wolfberry puree into the puree storage tank through the pump. The storage tank must be kept clean and free of contamination;

[0080] Fabric distribution: adjust the frequency of the fabric distribution motor to 35HZ, turn on the motor, turn on the conveyor belt of the drying bed, and evenly spread the wolfberry puree in the storage tank on the drying bed of the vacuum low-temperature continuous belt drying equipment through the fabric distribution device. Observe the fabric thickness at any time during the fabric distribution process. The material thickness should be kept at about 1cm;

[0081] Vacuuming: Set the vacuum degree to 2.0-2.5 kPa and start vacuuming to facilitate subsequent heating to reach the boiling point of the material faster;

[0082] Heating: Set the temperature of the temperature pipe to 85-95℃, start steam heating, and make the wolfberry puree continue to heat up through the steam heating of the heating pipe in a vacuum environment. At the same time, observe whether the cooling equipment operates smoothly and whether there is any abnormality. Visually check whether the cooling water is short of water during vacuum. If it is lower than or close to the standard line, replenish water in time to avoid abnormal equipment and product quality risks caused by excessive temperature;

[0083] Drying: Keep the vacuum degree at 2.0-2.5kpa. When the temperature of the heating pipe rises to 85-95℃, the temperature of the wolfberry puree is about 40-45℃. At this time, the wolfberry puree is in a boiling state. Continue drying for 45-50 minutes to evaporate all the water.

[0084] Low temperature cooling: After drying, set the pipeline temperature to 15-20℃ for low temperature cooling. When the material temperature reaches 20-25℃, it is ready to be discharged.

[0085] Discharging: temporarily store the cooled semi-finished wolfberry powder in the storage tank. When all the products in the same batch are finished, open the vacuum valve, switch the material valve, and send the dry powder to the receiving barrel for subsequent crushing;

[0086] Crushing: Under low temperature (less than 20℃), the speed of the crusher is controlled at 3500-4000r / min, and the dried semi-finished wolfberry powder is crushed by the crusher. The speed should not be higher than 4000r / min to avoid the loss of nutrients in the wolfberry powder or sticking to the machine due to excessive speed;

[0087] Sieving: The crushed product is passed through sieves of different mesh sizes to obtain wolfberry powder of different mesh sizes ranging from 80 to 200;

[0088] Packaging: After the sieved dry powder meets the standard requirements, it will be vacuum packed in different specifications according to customer needs in the clean room. When packaging, it should be noted that the humidity should not exceed 45% to prevent the dry powder from getting damp and agglomerating, resulting in quality changes.

[0089] Embodiment 4

[0090] Raw material preparation: Get qualified wolfberry puree and check whether the production date, certificate of conformity, physical and chemical indicators and other information meet the processing requirements;

[0091] Feeding: Turn on the feeding screw pump switch and pump the prepared wolfberry puree into the puree storage tank through the pump. The storage tank must be kept clean and free of contamination;

[0092] Fabric distribution: adjust the frequency of the fabric distribution motor to 35HZ, turn on the motor, turn on the conveyor belt of the drying bed, and evenly spread the wolfberry puree in the storage tank on the drying bed of the vacuum low-temperature continuous belt drying equipment through the fabric distribution device. Observe the fabric thickness at any time during the fabric distribution process. The material thickness should be kept at about 1cm;

[0093] Vacuuming: Set the vacuum degree to 1.0-2.5 kPa and start vacuuming to facilitate subsequent heating to reach the boiling point of the material faster;

[0094] Heating: Set the temperature of the temperature pipe to 85-95℃, start steam heating, and make the wolfberry puree continue to heat up through the steam heating of the heating pipe in a vacuum environment. At the same time, observe whether the cooling equipment operates smoothly and whether there is any abnormality. Visually check whether the cooling water is short of water during vacuum. If it is lower than or close to the standard line, replenish water in time to avoid abnormal equipment and product quality risks caused by excessive temperature;

[0095] Drying: Keep the vacuum degree at 1.0-2.5kpa. When the temperature of the heating pipe rises to 85-95℃, the temperature of the wolfberry puree is about 40-55℃. At this time, the wolfberry puree is in a boiling state. Continue drying for 45-60 minutes to evaporate all the water.

[0096] Low temperature cooling: After drying, set the pipeline temperature to 15-20℃ for low temperature cooling. When the material temperature reaches 20-25℃, it is ready to be discharged.

[0097] Discharging: temporarily store the cooled semi-finished wolfberry powder in the storage tank. When all the products in the same batch are finished, open the vacuum valve, switch the material valve, and send the dry powder to the receiving barrel for subsequent crushing;

[0098] Crushing: Under low temperature (less than 20℃), the speed of the crusher is controlled at 3500-4000r / min, and the dried semi-finished wolfberry powder is crushed by the crusher. The speed should not be higher than 4000r / min to avoid the loss of nutrients in the wolfberry powder or sticking to the machine due to excessive speed;

[0099] Sieving: The crushed product is passed through sieves of different mesh sizes to obtain wolfberry powder of different mesh sizes ranging from 80 to 200;

[0100] Packaging: After the sieved dry powder meets the standard requirements, it will be vacuum packed in different specifications according to customer needs in the clean room. When packaging, it should be noted that the humidity should not exceed 45% to prevent the dry powder from getting damp and agglomerating, resulting in quality changes.

[0101] The wolfberry powder sample obtained in the fourth embodiment was taken for comparative analysis of characteristic nutritional components with the vacuum freeze-dried wolfberry powder and the spray-dried wolfberry powder:

[0102] (1) Comparison of Lycium barbarum polysaccharide content determination: Using glucose as the standard, the polysaccharide content of three kinds of Lycium barbarum powder was determined by phenol-sulfuric acid method;

[0103] (1.1) Drawing of glucose standard curve:

[0104] Table 1 Absorbance values ​​of glucose standard curve

[0105]

[0106] With glucose concentration as the horizontal axis and absorbance value as the vertical axis, a standard curve is drawn and a univariate regression equation of the standard curve is obtained, such as Figure 2 As shown;

[0107] (1.2) Determination of Lycium barbarum polysaccharides

[0108] Table 2 Lycium barbarum polysaccharide content

[0109]

[0110] from Figure 3It can be seen that the polysaccharide contents of wolfberry powders dried by three different methods are in the following order from high to low: vacuum low-temperature drying > spray drying > vacuum freeze drying. The polysaccharide content of vacuum freeze-dried wolfberry powder is lower. The reason may be that the ethanol concentration required for the precipitation of polysaccharides with different properties or different relative molecular weights is different. The solubility of vacuum freeze-dried wolfberry powder is higher, some monosaccharides are soluble in ethanol, and some water-soluble polysaccharides are dissolved. According to the statistical analysis, different lowercase letters in the figure indicate that the polysaccharide content between different drying methods is significantly different (P < 0.05).

[0111] (2) Comparison of total phenol content determination: The total phenol content of wolfberry powder was determined by the Folin-Ciocalteus method;

[0112] The gallic acid standard curve was drawn based on the absorbance value of gallic acid standards with different concentrations as the ordinate and the gallic acid concentration as the abscissa.

[0113] The standard curve equation is y = 0.1472x-0.0058 (R2 = 0.9993), such as Figure 4 As shown;

[0114] The total phenol content of three kinds of wolfberry powder with different drying methods was calculated according to the standard curve. The results are as follows: Figure 5 As shown, the results show that

[0115] The total phenol content in the wolfberry powder dried at low temperature by vacuum was the highest, which was 360.87±21.92μg / g;

[0116] The second is vacuum freeze-dried wolfberry powder, whose total phenol content is 238.12±7.93μg / g.

[0117] The total phenol content of spray-dried wolfberry powder was the lowest, which was 25.05±2.15μg / g.

[0118] According to the statistical analysis, the total phenol content of wolfberry powder treated with different drying methods was significantly different (P<0.01).

[0119] (3) Comparison of vitamin B1 and B2 content

[0120] (3.1) Determination of vitamin B1 content

[0121] The first method of GB 5009.84-2016 "National Food Safety Standard - Determination of Vitamin B1 in Food" - HPLC was used to determine the content of vitamin B1 in wolfberry powder. The HPLC chromatograms of vitamin B1 standard and vitamin B1 extracts of three wolfberry powder samples were obtained.

[0122] According to the HPLC chromatogram of the vitamin B1 standard, the standard curve was drawn with the concentration (μg / mL) as the ordinate and the peak area as the abscissa.

[0123] The standard curve regression equation is y = 36360445.0269x-590288.9583 (R2 = 0.9994), such as Figure 6 As shown, the vitamin B1 content of wolfberry powder with three different drying methods was calculated according to the standard curve shown, and the results are shown in Table 3.

[0124] Table 3 Vitamin B1 content of wolfberry powder

[0125]

[0126] The results showed that the content of vitamin B1 was: vacuum low-temperature drying > vacuum freeze drying > spray drying. The statistical results showed that the content of vitamin B1 in wolfberry powder with different drying methods was significantly different, all P < 0.05.

[0127] (3.2) Determination of vitamin B2 content

[0128] The first method of GB 5009.85-2016 "National Food Safety Standard - Determination of Vitamin B2 in Food" - High Performance Liquid Chromatography was used to determine the content of vitamin B2 in wolfberry powder. The high performance liquid chromatograms of vitamin B2 standard and vitamin B2 extracts of three wolfberry powder samples were obtained.

[0129] According to the HPLC chromatogram of the vitamin B2 standard, a standard curve was drawn with the concentration (μg / mL) as the ordinate and the peak area as the abscissa.

[0130] The standard curve regression equation is y=3882690.9871x-38507.4652 (R2=0.9992), such as Figure 7 As shown, the vitamin B2 content of wolfberry powder with three different drying methods was calculated according to the standard curve, and the results are shown in Table 4.

[0131] Table 4 Vitamin B2 content of wolfberry powder

[0132]

[0133] The results showed that the content of vitamin B2 was: vacuum low-temperature drying > vacuum freeze drying > spray drying. The statistical results showed that the content of vitamin B2 in wolfberry powder with different drying methods was significantly different, all P < 0.01.

[0134] According to the above analysis and comparison of the characteristic nutrient content of wolfberry powder with different drying methods, it can be concluded that vacuum low-temperature drying can minimize the loss of characteristic nutrients such as wolfberry polysaccharides, total phenols and vitamins in wolfberry powder during the drying process compared with spray drying and vacuum freeze drying.

[0135] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing wolfberry powder by vacuum low-temperature continuous drying, characterized in that: include, Step 1: Material preparation: prepare high-quality wolfberry raw materials and process them; Step 2: Vacuuming: Set the vacuum degree to 1.0-2.5 kPa and start vacuuming to facilitate the subsequent heating to reach the boiling point of the material faster; Step 3: Heating: In a vacuum environment, gradually heat to promote the evaporation of water; Step 4, drying: keep the vacuum degree at 1.0-2.5kpa, when the temperature of the heating pipe rises to 85-95℃, the temperature of the wolfberry puree is about 40-55℃, at which time the wolfberry puree is in a boiling state, continue drying for 45-60 minutes to evaporate all the water; Step 5: Low temperature cooling: After drying, set the pipeline temperature to 15-20°C for low temperature cooling. When the material temperature reaches 20-25°C, it is ready to be discharged. Step 6: Discharging: temporarily store the cooled semi-finished wolfberry powder in a storage tank. After all the products in the same batch are finished, open the vacuum valve, switch the material valve, and send the dry powder to the receiving barrel for subsequent crushing; Step 7: Grinding: Grinding the dried wolfberries to achieve the required powder fineness; Step 8. Processing and collection: The crushed products are screened and packaged for storage.

2. The method for preparing wolfberry powder by vacuum low-temperature continuous drying according to claim 1, characterized in that: The material preparation of step 1 specifically includes the following steps: Step S1, raw material preparation: receiving qualified wolfberry puree, and checking whether the production date, certificate of conformity, physical and chemical indicators and other information meet the processing requirements; Step S2, feeding: Turn on the feeding screw pump switch, and pump the prepared wolfberry puree into the puree storage tank through the pump. The storage tank must be kept clean and not contaminated; Step S3, cloth: Spread the wolfberries evenly to ensure even heat distribution during the drying process.

3. The method for preparing wolfberry powder by vacuum low-temperature continuous drying according to claim 2, characterized in that: The spreading of step S3 specifically includes: adjusting the frequency of the spreading motor to 35HZ, turning on the motor, turning on the conveyor belt of the drying bed, and evenly spreading the wolfberry puree in the storage tank on the drying bed of the vacuum low-temperature continuous belt drying equipment through the spreading device. The thickness of the cloth is observed at any time during the spreading process, and the material thickness should be kept at about 1cm.

4. The method for preparing wolfberry powder by vacuum low-temperature continuous drying according to claim 1, characterized in that: The heating in step three specifically includes: setting the temperature of the temperature pipe to 85-95°C, starting steam heating, so that the wolfberry puree is continuously heated by steam heating of the heating pipe in a vacuum environment, and at the same time observing whether the cooling equipment operates smoothly and whether there are any abnormalities, and visually inspecting whether the cooling water is short of water during vacuum. If it is lower than or close to the standard line, replenish water in time.

5. The method for preparing wolfberry powder by vacuum low-temperature continuous drying according to claim 1, characterized in that: The crushing in step seven specifically includes: under low temperature (less than 20° C.), the speed of the crusher is controlled at 3500-4000 r / min, and the dried semi-finished wolfberry powder is crushed by the crusher, and the speed shall not be higher than 4000 r / min.

6. The method for preparing wolfberry powder by vacuum low-temperature continuous drying according to claim 1, characterized in that: The processing and collection of step eight specifically includes the following steps: Step K1, sieving: passing the crushed product through sieves of different mesh sizes to obtain wolfberry powder of different mesh sizes ranging from 80 to 200 meshes; Step K2, packaging: packaging the qualified wolfberry powder for storage and transportation; Step K3, inspection: Inspect according to Q / QZTS 0004S-2023, and issue a certificate of conformity after passing; Step K4, storage: After the inspection, the products are stored in a dedicated area away from walls and the ground. The humidity in the warehouse should be below 60%.

7. The method for preparing wolfberry powder by vacuum low-temperature continuous drying according to claim 6, characterized in that: The packaging of step K2 specifically includes: after the sieved dry powder meets the standard requirements, vacuum packaging of different specifications is carried out in a clean room according to customer needs, and it should be noted that the humidity should not exceed 45% during packaging.

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