Prunus domestica powder product and method for processing prunus domestica powder

Abstract

The present application relates to a kind of prunus domestica powder product and the processing method of prunus domestica powder, wherein the processing method of prunus domestica powder, comprising the following steps: S1, prunus domestica pretreatment: prunus domestica fresh fruit is cored and sliced, and prunus domestica slice is prepared;S2, freeze-drying: prunus domestica slice is vacuum freeze-dried;S3, microwave drying: prunus domestica slice after freeze-drying is vacuum microwave dried, and dried to moisture content 10%~12%;S4, grinding: prunus domestica slice after microwave drying is ground and sieved, and prunus domestica powder is obtained.Its beneficial effect is that prunus domestica can still be rich in nutrition in dry form, the solubility of powder after treatment is better, the powder quality is better, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, and particularly relates to a prune powder product and a processing method of prune powder. BACKGROUND

[0002] Prunes contain rich nutritional ingredients, including vitamin A and cellulose, and also contain minerals such as iron and potassium, but do not contain fat and cholesterol. Prunes can help the human body supplement iron, zinc and potassium, and have the effect of strengthening the body and bones; the antioxidant substances contained therein can also delay the aging of the body and brain. In addition, the bitter acid of prunes can strengthen liver function and eliminate fatigue.

[0003] The prune industry has problems such as a short fruit picking period, high water content, and difficulty in transportation and preservation. Therefore, processing prunes into prune powder not only facilitates storage and carrying, but also prolongs the shelf life. However, in the process of processing prunes into powder, some nutritional ingredients are lost, especially the antioxidant substances, which are greatly destroyed in the processing process, resulting in a decrease in the nutritional value of prune powder compared to fresh prunes. In addition, the prepared prune powder has low solubility, which affects its use in the food field and is not conducive to the exertion of its nutritional substances.

[0004] Therefore, a new processing method of prune powder is needed to solve the above technical problems. SUMMARY

[0005] (I) Technical problems to be solved

[0006] In view of the above shortcomings and deficiencies of the prior art, the present application provides a prune powder product and a processing method of prune powder, which solves the technical problems of excessive loss of nutritional ingredients in the process of processing prunes into powder and poor solubility of the produced prune powder.

[0007] (II) Technical solutions

[0008] In order to achieve the above purpose, the main technical solutions adopted by the present application include:

[0009] In a first aspect, the present application provides a processing method of prune powder, comprising the following steps:

[0010] S1, prune pretreatment: removing the core and slicing the prune fresh fruit to obtain prune slices;

[0011] S2, freeze-drying: vacuum freeze-drying the prune slices;

[0012] S3, microwave drying: vacuum microwave drying the freeze-dried prune slices until the moisture content is 10% to 12%;

[0013] S4, crushing: crushing and sieving the microwave-dried prune slices to obtain prune powder.

[0014] Optionally, in the step S2, the vacuum freeze-drying, the pre-freezing is first performed at -80±1℃ for 20-24h, then the gradient cooling is performed by freezing at -45℃ to -40℃ for 2-3h, at -35℃ to -30℃ for 2-3h, and at -25℃ to -20℃ for 1-1.5h, and finally the temperature is raised to 25℃ to 30℃ for 3-5h.

[0015] Optionally, in the step S2, the gradient cooling, each time the temperature is raised for 10-15min.

[0016] Optionally, in the step S2, after the pre-freezing, the prunes are sequentially frozen at -45℃ for 2h, at -35℃ for 2h, and at -25℃ for 1h.

[0017] Optionally, in the step S2, before the temperature maintaining, the temperature is sequentially raised at -10℃, 0℃, 10℃, and 20℃ for 10-15min.

[0018] Optionally, in the step S3, the vacuum microwave drying is performed at 80-85℃ for 0.5-1h.

[0019] Optionally, before the step S1, the fresh prunes are pre-cooled at -2±1℃ for 20-24h.

[0020] Optionally, in the step S1, the thickness of the prune slices is 10mm±5mm, which is convenient for the subsequent drying.

[0021] Optionally, in the step S4, the prune powder is obtained by passing through a 80-100 mesh sieve.

[0022] In the second aspect, the embodiment of the present application provides a prune powder product prepared by the prune powder processing method of the first aspect.

[0023] (III) Beneficial Effects

[0024] The present application has the beneficial effects that: the prunus domestica powder product and the processing method of the prunus domestica powder have the following beneficial effects: the prunus domestica fresh fruit is dried by combining vacuum freeze drying and microwave drying, so that the nutrients in the prunus domestica fresh fruit are effectively retained, especially the active substances related to oxidation, the total phenol retention rate is as high as 77%, and the total flavone retention rate is as high as 70%; at the same time, the solubility of the prunus domestica powder prepared by the method is as high as 94%; the combination of vacuum freeze drying and vacuum microwave drying significantly improves the overall drying efficiency and reduces the preparation time. Compared with the prior art, the prunus domestica is still rich in nutrients in the dried form, the solubility of the treated powder is better, the powder quality is better, and the production efficiency is improved.

[0025] In the vacuum freeze drying process of the prunus domestica fresh fruit, pre-freezing is first performed, the temperature of the prunus domestica is rapidly reduced, the water in the prunus domestica is frozen, so that the organization structure of the prunus domestica is fixed, and the respiration and enzyme activity of the prunus domestica are significantly inhibited, thereby reducing the loss of nutrients, which helps to retain more nutrients and active ingredients in the drying process.

[0026] In the vacuum freeze drying process, the temperature is gradually increased, and finally increased to above the freezing point for maintenance, so that the solid water at low temperature is removed from the prunus domestica by sublimation, and the overall low-temperature environment is beneficial to the nutrients in the prunus domestica, so that the nutrients in the prunus domestica are retained to the greatest extent.

[0027] In the gradient cooling stage, the temperature is controlled to be increased for 10-15 min each time, and the rapid temperature increase is beneficial to the sublimation efficiency and the retention of nutrients.

[0028] Before the temperature maintenance stage, the temperature is gradually increased to-10℃, 0℃, 10℃ and 20℃ for 10-15 min each time, so as to ensure that the subsequent temperature maintenance stage has sufficient time (i.e. maintaining at 25℃-30℃ for a long enough time), which is beneficial to the sublimation of water in the prunus domestica. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The prunus domestica slices after drying in Example 1 of the prunus domestica powder product and the processing method of the prunus domestica powder of the present application;

[0030] Figure 2 The prunus domestica powder crushed from the prunus domestica slices in Figure 1 DETAILED DESCRIPTION

[0031] In order to better explain the present application, the present application will be described in detail in combination with the drawings and specific embodiments.

[0032] ​The present application provides a dried prune powder and a method for preparing the dried prune powder. The method for preparing the dried prune powder comprises the following steps: picking ripe prunes, precooling the prunes, removing the pits of the prunes, drying the prunes, and grinding the dried prunes into powder. The method for preparing the dried prune powder can effectively retain the nutrients in the prunes, especially the antioxidants, and the total phenol retention rate is up to 77%, and the total flavonoid retention rate is up to 70%. The solubility of the dried prune powder prepared by the method is up to 94%. Compared with the prior art, the dried prune powder prepared by the method is rich in nutrients, has better solubility, and has better quality.

[0033] In order to better understand the above technical solutions, the exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the present application can be more clearly, thoroughly understood, and the scope of the present application can be completely conveyed to those skilled in the art.

[0034] Embodiment 1

[0035] (1) Pick ripe (hardness: 3.50N, soluble solids: 24.96%) prunes in the local orchard of Qapqal County, Kashgar, Xinjiang (35°25'N, 72°26'E), and immediately transport them to the Fruit and Vegetable Storage and Preservation Laboratory of the Food College of Shihezi University. Select fruits that are uniform in size and color, have no mechanical damage and no pests and diseases, and then place the selected fruits in a cold storage at -2±1℃ for 20h to remove field heat;

[0036] (2) Vacuum freeze-drying: first, pre-cooled prunes are pitted and cut into 1cm thick prune slices, which are placed in the tray of a vacuum freeze-drying machine and pre-frozen at -80℃ for 24h; second, the pre-frozen prune slices are sequentially frozen at -45℃ for 2h, at -35℃ for 2h, and at -25℃ for 1h; then, the prune slices are sequentially transitioned at -10℃, 0℃, 10℃, and 20℃ for 10min each; finally, the prune slices are kept at 30℃ for 4h;

[0037] (3) Vacuum microwave drying: the prune slices after vacuum freeze-drying are placed in the tray of a vacuum microwave drying machine at a temperature of 80℃, and microwave drying is performed until the moisture content is 11%;

[0038] (4) The prune slices after vacuum microwave drying are ground by a flour mill and then sieved through an 80-mesh sieve to obtain the dried prune powder.

[0039] (5) The total phenol content, total flavonoid content, and solubility of the dried prune powder are detected, and the specific detection results are shown in Table 1.

[0040] The detection results of this embodiment as the best embodiment are shown in Table 1. The total phenol content of the prepared prune powder is close to 77% of the total phenol content of fresh fruit, and the total flavonoid content of the prune powder is close to 70% of the total flavonoid content of fresh fruit, thus the antioxidant-related nutrients in fresh fruit are retained to the greatest extent. At the same time, the solubility of the prune powder is as high as 94±0.3%, which is beneficial to the exertion of the nutrients of the prune powder.

[0041] In addition, referring to the drawings Figure 1 and the drawings Figure 2 , the color of the prune slices and the prune powder prepared by drying using the above method is golden yellow, close to the color of the flesh of fresh prune fruit, and the quality is excellent.

[0042] Example 2

[0043] This embodiment provides a processing method of prune powder, and the specific steps are as follows:

[0044] (1) French prunes at 80% maturity (hardness: 3.60N, soluble solids: 23.87%) were picked in local orchards in Tekes County, Yili Kazakh Autonomous Prefecture, Xinjiang (42°22'N, 81°19'E), and immediately transported to the Fruit and Vegetable Storage and Preservation Laboratory of the Food College of Shihezi University after harvesting. The fruits with uniform size and color, without mechanical damage and pests and diseases were selected, and then placed in a cold storage at -2±1℃ for 24h to remove field heat;

[0045] (2) Vacuum freeze-drying: first, the pre-cooled prunes were pitted and cut into 0.5cm thick prune slices, which were placed in the tray of a vacuum freeze-drying machine and pre-frozen at -80℃ for 24h; second, the pre-frozen prune slices were sequentially frozen at -40℃ for 3h, at -30℃ for 3h, and at -20℃ for 1.5h; then, sequentially transitioned at -10℃, 0℃, 10℃, and 20℃ for 15min; finally, maintained at 25℃ for 5h;

[0046] (3) Vacuum microwave drying: the prune slices after vacuum freeze-drying were placed in the tray of a vacuum microwave drying machine, and the temperature was set at 85℃, and the microwave drying was performed until the moisture content was 12%;

[0047] (4) The prune slices after vacuum microwave drying were ground by a super micro grinder and sieved through an 80-mesh sieve to obtain prune powder.

[0048] (5) The total phenol content, total flavonoid content, and solubility of the prune powder were detected, and the specific detection results are shown in Table 1.

[0049] The detection results are shown in Table 1. The total phenol content of the prepared prune powder is close to 75% of the total phenol content of the fresh fruit, and the total flavonoid content of the prune powder is close to 70% of the total flavonoid content of the fresh fruit, thereby retaining the antioxidant-related nutrients in the fresh fruit to the greatest extent. Meanwhile, the solubility of the prune powder is as high as 93±1.2%, which is conducive to the exertion of the nutritional substances of the prune powder.

[0050] Example 3

[0051] The processing method of the prune powder provided in this example is different from that of Example 2 in that step (2) is changed to: first, the pre-cooled prunes are cored and cut into 0.5 cm thick prune slices, which are laid in the tray of the vacuum freeze dryer and pre-frozen at -80℃ for 24 h; second, the pre-frozen prune slices are sequentially frozen at -40℃ for 3 h, at -35℃ for 2 h, and at -20℃ for 1.5 h; then, the temperature is sequentially transitioned at -10℃, 0℃, 10℃, and 20℃ for 15 min each; finally, the temperature is maintained at 30℃ for 4 h. The remaining steps are the same as those in Example 1.

[0052] In Example 3, the temperature difference of the gradient temperature increase process before the transition stage is 5℃ and 15℃, respectively. The detection results are shown in Table 1. It can be known from the comparison between Example 2 and Example 3 that the total phenol content and the total flavonoid content of the prune powder prepared in Example 3 decrease slightly.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that:

[0055] The first step of vacuum freeze drying in step (2), i.e., pre-freezing at -80℃ for 24 h in the tray of the vacuum freeze dryer, is omitted. The remaining steps are the same as those in Example 1.

[0056] As shown in Table 1, compared with Example 1, the total phenol content of the prune powder in Comparative Example 1 decreases by about 35%, the total flavonoid content decreases by about 55%, and the solubility decreases by about 11%. The first step of pre-freezing in vacuum freeze drying rapidly reduces the temperature of the prunes, freezes the internal moisture of the prunes, thereby fixing the tissue structure of the prunes, and can significantly inhibit the respiration of the prunes and the activity of enzymes, thereby reducing the loss of nutrients, which helps to retain more nutrients and active ingredients during the drying process.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 1 is that:

[0059] In step (2), the 1 cm thick prune slices are directly subjected to the vacuum microwave drying of step (3) without any vacuum freeze drying. The remaining steps are the same as those in Example 1.

[0060] Comparative Example 3

[0061] The difference between the present comparative example and Example 1 is that step (2) is changed to: vacuum freeze-drying: first, the pre-cooled prune is cored and cut into 1 cm thick prune slices and placed in the tray of the vacuum freeze-drying machine after pre-cooling at -80℃ for 24 h; then, the temperature is quickly raised to -25℃ for freezing for 5 h, and then sequentially transitioned at -10℃ and 10℃ for 30 min, respectively; finally, the temperature is raised to 30℃ and maintained for 4 h. The remaining steps are the same as those of Example 1.

[0062] As shown in Table 1, compared with Example 1, the total phenol content and total flavonoid content of the prune powder in Comparative Example 2 are greatly reduced, and the solubility is reduced by about 14%. If the step of vacuum freeze-drying is omitted and direct vacuum microwave drying at 80℃ is performed, the nutritional substances of the prune powder are seriously lost. It can be seen that the use of only a single drying process such as microwave drying can cause serious degradation of phenolic and flavonoid contents. At the same time, the molecular structure of the internal nutrients of the prune subjected to microwave treatment will change, causing aggregation between molecules, thereby reducing the solubility.

[0063] As can be seen from the comparison between Comparative Example 2 and Example 1, the use of a combination of vacuum freeze-drying and microwave drying to dry the fresh prune fruit reduces the time of microwave drying, which helps to maintain the nutrients in the fresh prune fruit, especially the active substances related to antioxidant activity.

[0064] As can be seen from the comparison between Comparative Example 3 and Example 1, during the vacuum freeze-drying process, the rapid temperature rise and the reduction of the transition stage can also significantly destroy the phenolic and flavonoid nutrients in the prune, resulting in a decrease in their content.

[0065] Table 1

[0066]

[0067] The above only describes the preferred embodiments of the present application, and those of ordinary skill in the art can make several improvements without departing from the principles of the present application, and these improvements should also be considered within the scope of protection of the present application.

[0068] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for processing prune powder, characterized by, The method comprises the following steps: S1, pretreatment of fresh plum: fresh plum is cored and sliced to obtain plum slices; S2, freeze-drying: the plum slices are subjected to vacuum freeze-drying; S3, microwave drying: the freeze-dried plum slices are subjected to vacuum microwave drying until the moisture content is 10-12%; the temperature is 80-85℃ and the time is 0.5-1h; S4, crushing: the microwave-dried plum slices are crushed and sieved to obtain plum powder; In step S2, in the vacuum freeze-drying, first, pre-freezing: freezing at-80±1℃ for 20-24h; then, gradient cooling: freezing at-45℃ to-40℃ for 2-3h, at-35℃ to-30℃ for 2-3h, and at-25℃ to-20℃ for 1-1.5h; finally, temperature rising and maintaining: rising the temperature to 25-30℃ and maintaining for 3-5h; before the temperature rising and maintaining stage, transition at-10℃, 0℃, 10℃ and 20℃ for 10-15min.

2. The method according to claim 1, wherein in step S2, the temperature rising process in the gradient cooling stage is 10-15min.

3. The method according to claim 1, wherein in step S2, after the pre-freezing, the plum slices are sequentially frozen at-45℃ for 2h, at-35℃ for 2h, and at-25℃ for 1h.

4. The method according to claim 1, wherein before step S1, the fresh plum is pre-cooled at-2±1℃ for 20-24h.

5. The method according to claim 1, wherein in step S1, the thickness of the plum slices is 10mm±5mm.

6. The method according to claim 1, wherein in step S4, the plum powder is obtained by sieving through a 80-100 mesh sieve. The plum powder is prepared by the method according to any one of claims 1-6. ​ ​ ​ ​ 7. A powder product of Prunus domestica L., characterized in that, ​

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