Method for preparing high astragalus-containing dried apples by a circulation steaming and drying method

Abstract

This invention discloses a method for preparing high-astragalus-content dried apples using a cyclic steaming and drying process, belonging to the field of food processing technology. Through a three-stage cyclic steaming and drying process involving three steaming cycles and three low-temperature drying cycles, combined with the steam explosion effect, pores are formed within the apple tissue. This allows the water-soluble component of astragalus, astragalus polysaccharide, and some fat-soluble component astragaloside A in astragalus to be continuously released under the action of warm steam. This promotes the rapid absorption of the water-soluble components of astragalus polysaccharide and some fat-soluble components of astragaloside A by the dried apples, which diffuse with the moisture, thus simultaneously increasing the content of astragalus polysaccharide and astragaloside A in the dried apples. Furthermore, by pre-soaking apple slices in a color-protecting solution and a preservative coating solution, and then combining this with the three-stage cyclic steaming and drying process, the polyphenol oxidase in the apples is deactivated by the hot steam, effectively preventing browning.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically a method for preparing dried apples with high astragalus content using a circulating steaming and drying method. Background Technology

[0002] Under the concept of "medicine and food sharing the same origin," the combination of astragalus and apple has become a popular choice for dietary supplements due to its dual advantages of replenishing qi, regulating immunity, and supplementing dietary fiber. Astragaloside A and astragalus polysaccharides in astragalus are the core active ingredients, while apples are rich in pectin, vitamins, and natural fructose. The combination of the two can meet the consumer demand for "nutrition through food." Currently, most astragalus and apple dietary supplements on the market use simple mixing and drying or direct extraction followed by drying processes. Moreover, the proportion of astragalus in the raw materials is generally less than 5%, serving only as an auxiliary flavoring ingredient, which is far from meeting the requirements of functional dietary supplements. In addition, products prepared by traditional processes are prone to flavor imbalance, as the bitterness of astragalus and the tartness of apple cannot be effectively balanced, resulting in low consumer acceptance.

[0003] Chinese patent application CN109259138A discloses a process for preparing dried apples using a combination of microwave and hot air drying. This invention uses microwave and hot air drying methods, adjusting the temperature based on the relationship between the water loss rate of the dried apples at different stages and the microwave power or hot air temperature, to rapidly heat the dried apples and keep them at a constant temperature for a longer period. However, at this temperature, heat-sensitive active ingredients such as astragaloside A and vitamin C are easily destroyed, leading to loss of efficacy. Furthermore, traditional processes combine astragalus and dried apples through single extraction or mixed treatment, but this method is difficult to achieve efficient penetration of the water-soluble and fat-soluble active ingredients of astragalus into the apple matrix, resulting in low component transfer efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing apple chips with high astragalus content using a cyclic steaming and drying method. This method involves a three-stage cyclic steaming and drying process, followed by three stages of low-temperature drying. The steam explosion effect creates pores within the apple tissue, allowing the water-soluble component astragalus polysaccharide and some fat-soluble component astragaloside A in astragalus to be continuously released under the action of warm steam. This promotes the rapid absorption of the water-soluble components of astragalus polysaccharide and some fat-soluble components of astragaloside A by the apple chips, which diffuse with the moisture, thus achieving a simultaneous increase in the content of astragalus polysaccharide and astragaloside A in the apple chips.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing dried apples with high astragalus content using a circulating steam-drying process includes the following steps: Step 1: Soak apple slices in color-protecting solution and then transfer them to a preservative coating solution for further soaking to obtain pre-treated apple slices.

[0006] Step 2: The pre-treated apple slices are subjected to steam explosion treatment to obtain pre-dried apples.

[0007] Step 3: Place the pre-made dried apples in a porcelain evaporating dish, and then perform three steaming and drying processes. Add astragalus and purified water before each steaming and drying process to obtain dried apples with high astragalus content, thus completing the method of preparing dried apples with high astragalus content by cyclic steaming and drying.

[0008] Furthermore, the steaming and drying process includes steaming and drying, with the steaming temperature being 100-105℃ and the drying temperature being 50-60℃.

[0009] Furthermore, the specific preparation steps for apple slices with high astragalus content are as follows: After rinsing the astragalus root 2-4 times with clean water, place it together with the pre-made dried apples in a porcelain evaporating dish. Then add purified water and steam at 100-105℃ for 20-22 minutes to initially release the water-soluble components of the astragalus root and allow them to be absorbed by the pre-made dried apples. After steaming, separate the astragalus root residue. Dry the pre-made dried apples at 50-60℃ at a low temperature until the surface is slightly dry. Then add the astragalus root and purified water and steam at 100-105℃ for 14-16 minutes to promote deep penetration. Separate the astragalus root residue and dry at 50-60℃ at a low temperature for a second time. Add the astragalus root and purified water again and steam at 100-105℃ for a third time for 10-12 minutes to stimulate aroma and complete component integration. Separate the astragalus root residue and dry at 50-60℃ at a low temperature for a third time to obtain dried apples with high astragalus root content.

[0010] Furthermore, the mass ratio of Astragalus membranaceus, pre-processed dried apples, and purified water is 48-54:130-140:720-850.

[0011] Furthermore, the specific preparation steps for pre-made dried apples are as follows: The pre-treated apple slices are transferred to a steam explosion device. After the pressure reaches 0.8-1.0 MPa and the temperature is 170-178℃, the slices are processed for 120-140 seconds. Then, they are placed in an oven and dried at 50-60℃ until the moisture content is ≤20%, thus obtaining pre-dried apples.

[0012] Furthermore, the specific preparation steps for pre-treated apple slices are as follows: Core ripe apples with a firm texture and fructose content ≥12% and cut them into slices 2-4 cm thick. Soak the apple slices in a color-protecting solution containing 0.4-0.6% citric acid and 0.4-0.6% calcium chloride for 3-4 hours, then transfer them to a preservative coating solution and soak for 20-30 minutes. After soaking, refrigerate at 4-5℃ for 1-2 hours and dry at 50-60℃ until the moisture content is 25-30% to obtain pretreated apple slices.

[0013] Furthermore, the preservative coating solution comprises 3-4% agar powder, 6-8% hydroxypropyl distarch phosphate and 6-8% xylitol, with the remainder being purified water at 70-80℃.

[0014] The preferred apple variety is any one of Fuji, Honeycrisp, or Gala.

[0015] The beneficial effects of this invention are: 1. The method for preparing high-Astragalus-content dried apples using the cyclic steaming and drying method provided by this invention involves three cycles of steaming and low-temperature drying. Combined with the steam explosion effect, pores are formed inside the apple tissue, allowing the water-soluble component Astragalus polysaccharide and some fat-soluble component Astragaloside A in Astragalus to be continuously released under the action of warm steam. This promotes the rapid absorption of the water-soluble component Astragalus polysaccharide and some fat-soluble component Astragaloside A by the dried apples, which diffuse with the water, thus achieving a simultaneous increase in the content of Astragalus polysaccharide and Astragaloside A in the dried apples.

[0016] 2. Traditional single-stage drying can easily lead to residual bitterness of astragalus or a prominent sour and astringent taste of apple. However, the three-cycle steam drying process of this invention softens the apple tissue with steam, releases fructose, and promotes the gradual penetration of the sweet substances of astragalus, ultimately forming a unique flavor that is "sweet but not greasy, with a slight medicinal aroma but not bitter." This gives the product both the pleasant taste of natural dried fruit and clear health benefits such as replenishing qi, strengthening the body's defenses, and enhancing immunity, truly achieving "nourishing through food." This meets consumers' needs for daily and snack-like health interventions, greatly improving consumer acceptance, and is especially suitable for long-term dietary health scenarios.

[0017] 3. This invention pre-soaks apple slices in a color-protecting liquid and a preservative coating liquid. The preservative coating liquid provides structural support and oxygen barrier to protect the apple slices from cracking, browning, and moisture loss during the steam explosion process. The steam explosion process creates internal puffing and pores in the dried apples, which can compensate for the tough texture and insufficient puffing caused by the preservative coating liquid. The combined use of the two results in dried apples with the advantages of intact shape, bright color, light and crisp texture, stable moisture content, and well-developed pores. Combined with a three-cycle steam drying process, the polyphenol oxidase in the apples is deactivated by the hot steam, effectively preventing browning. At the same time, the flavonoids in Astragalus membranaceus react with apple polysaccharides under mild and humid conditions to form a stable amber appearance, resulting in a finished product with uniform color and a glossy sheen, which is significantly better than the dull and blackened phenomenon of ordinary mixed drying products. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing apple slices with high astragalus content using a circulating steaming and drying method, comprising the following steps: S1: Core and slice 2cm thick ripe Shandong Red Fuji apples with a fructose content ≥12% after removing the cores. Soak the apple slices in a color-protecting solution containing 0.4% citric acid and 0.4% calcium chloride for 3 hours, then transfer them to a preservative coating solution for 20 minutes. After soaking, refrigerate at 4℃ for 1 hour and dry at 50℃ until the moisture content is 25% to obtain pretreated apple slices. The preservative coating solution includes 3% agar powder, 6% hydroxypropyl distarch phosphate and 6% xylitol, with the remainder being 70℃ purified water.

[0020] S2: Transfer 500g of pre-treated apple slices to a steam explosion device. After the pressure reaches 0.8MPa and the temperature is 170℃, process for 120s. Then place in an oven and dry at 50℃ until the moisture content is ≤20% to obtain pre-made dried apples.

[0021] S3: After rinsing 28g of Astragalus membranaceus twice with clean water, place it together with 130g of pre-made dried apples in a porcelain evaporating dish. Then add 500g of purified water and steam at 100℃ for 20 minutes to allow the water-soluble components of Astragalus membranaceus to be initially released and adsorbed by the pre-made dried apples. After steaming, separate the Astragalus membranaceus residue. Dry the pre-made dried apples at 50℃ for the first time until the surface is slightly dry. Then add 12g of Astragalus membranaceus and 120g of purified water and steam at 100℃ for 14 minutes to promote deep penetration. Separate the Astragalus membranaceus residue and dry at 50℃ for the second time. Then add 8g of Astragalus membranaceus and 100g of purified water and steam at 100℃ for the third time for 10 minutes to stimulate aroma and complete component integration. Separate the Astragalus membranaceus residue and dry at 50℃ for the third time to obtain a high Astragalus membranaceus content dried apple with a moisture content ≤12% and an astragaloside A content ≥0.290%. This completes the method of preparing high Astragalus membranaceus content dried apples using the cyclic steaming and drying method.

[0022] Example 2: A method for preparing dried apples with high astragalus content using a circulating steaming and drying method, comprising the following steps: S1: Core and slice 3cm thick ripe Shandong Red Fuji apples with a fructose content ≥12% after removing the cores. Soak the apple slices in a color-protecting solution containing 0.5% citric acid and 0.5% calcium chloride for 3.5h, then transfer them to a preservative coating solution for 25min. After soaking, refrigerate at 4.5℃ for 1.5h and dry at 55℃ until the moisture content is 28% to obtain pretreated apple slices. The preservative coating solution includes 3.5% agar powder, 7% hydroxypropyl distarch phosphate, and 7% xylitol, with the remainder being 75℃ purified water.

[0023] S2: Transfer 550g of pre-treated apple slices to a steam explosion device. After the pressure reaches 0.9MPa and the temperature is 174℃, process for 130s. Then place in an oven and dry at 55℃ until the moisture content is ≤20% to obtain pre-made dried apples.

[0024] S3: After rinsing 29g of Astragalus membranaceus three times with clean water, place it together with 135g of pre-prepared dried apples in a porcelain evaporating dish. Then add 550g of purified water and steam at 102.5℃ for 21 minutes to allow the water-soluble components of Astragalus membranaceus to be initially released and adsorbed by the pre-prepared dried apples. After steaming, separate the Astragalus membranaceus residue. Dry the pre-prepared dried apples at 55℃ for the first time until the surface is slightly dry. Then add 13g of Astragalus membranaceus and 130g of purified water and steam at 102.5℃ for 15 minutes to promote deep penetration. Separate the Astragalus membranaceus residue and dry at 55℃ for the second time. Then add 9g of Astragalus membranaceus and 105g of purified water and steam at 102.5℃ for the third time for 11 minutes to stimulate aroma and complete component integration. Separate the Astragalus membranaceus residue and dry at 55℃ for the third time to obtain a high Astragalus membranaceus content dried apple with a moisture content ≤12% and an astragaloside A content ≥0.290%. This completes the method for preparing high Astragalus membranaceus content dried apples using the cyclic steaming and drying method.

[0025] Example 3: A method for preparing apple slices with high astragalus content using a circulating steaming and drying method, comprising the following steps: S1: Core and slice 4cm thick ripe Shandong Red Fuji apples with a fructose content ≥12% after removing the cores. Soak the apple slices in a color-protecting solution containing 0.6% citric acid and 0.6% calcium chloride for 4 hours, then transfer them to a preservative coating solution and soak for 30 minutes. After soaking, refrigerate at 5℃ for 2 hours and dry at 60℃ until the moisture content is 30% to obtain pretreated apple slices. The preservative coating solution includes 4% agar powder, 8% hydroxypropyl distarch phosphate and 8% xylitol, with the remainder being 80℃ purified water.

[0026] S2: Transfer 600g of pre-treated apple slices to a steam explosion device. After the pressure reaches 1.0MPa and the temperature is 178℃, process for 140s. Then place in an oven and dry at 60℃ until the moisture content is ≤20% to obtain pre-dried apples.

[0027] S3: After rinsing 30g of Astragalus membranaceus four times with clean water, place it together with 140g of pre-made dried apples in a porcelain evaporating dish. Then add 600g of purified water and steam at 105℃ for 22 minutes to allow the water-soluble components of Astragalus membranaceus to be initially released and adsorbed by the pre-made dried apples. After steaming, separate the Astragalus membranaceus residue. Dry the pre-made dried apples at 60℃ for the first time until the surface is slightly dry. Then add 14g of Astragalus membranaceus and 140g of purified water and steam at 105℃ for the second time for 16 minutes to promote deep penetration. Separate the Astragalus membranaceus residue and dry at 60℃ for the second time. Then add 10g of Astragalus membranaceus and 110g of purified water and steam at 105℃ for the third time for 12 minutes to stimulate aroma and complete component integration. Separate the Astragalus membranaceus residue and dry at 60℃ for the third time to obtain a high Astragalus membranaceus content dried apple with a moisture content ≤12% and an astragaloside A content ≥0.290%. This completes the method for preparing high Astragalus membranaceus content dried apples using the cyclic steaming and drying method.

[0028] The steam explosion equipment used in this embodiment is model QBS-200B, manufactured by Hebi Zhengdao Bioenergy Co., Ltd.

[0029] Comparative Example 1: Based on Example 3, the pre-treated apple slices in step S2 were replaced with the apple slices in step S1, while the other steps remained unchanged, to prepare apple chips with high astragalus content, thus completing the method for preparing apple chips with high astragalus content by cyclic steam drying.

[0030] Comparative Example 2: Based on Example 3, in step S3, the pre-made dried apples were replaced with the pre-treated apple slices prepared in step S1, while the other steps remained unchanged, to prepare dried apples with high astragalus content, thus completing the method of preparing dried apples with high astragalus content by cyclic steam drying.

[0031] Performance tests were conducted on Examples 1-3 and Comparative Examples 1-2 using high-performance liquid chromatography (HPLC). 10g of dried apples with high astragalus content were evaporated to dryness in a 60℃ water bath, placed in a Soxhlet extractor, and 40mL of methanol was added. The extract was then cold-soaked overnight. An appropriate amount of methanol was added, and the mixture was refluxed in an 80℃ water bath for 4 hours. The extract was concentrated to dryness. 10mL of water was added to the residue, and the residue was dissolved by gentle heating. The extract was then shaken four times with 40mL of water-saturated n-butanol. The n-butanol extracts were combined and washed twice thoroughly with 40mL of 10% dilute ammonia solution. The ammonia solution was discarded, and the n-butanol layer was evaporated to dryness and then diluted to 5mL with methanol for testing. Astragaloside A was prepared at a concentration of 0.5mg / mL as a control sample. Chromatographic conditions and system suitability: After preliminary testing, a C18 column (150 mm x 4.6 mm, 5 μm) was selected. The mobile phase was acetonitrile:water = 32:68 with isocratic elution. The detection wavelength was 202 nm, the flow rate was 0.8 mL / min, the column temperature was 30 °C, and the injection volume was 10 μL. External standard method was used for quantification. The results are shown in Table 1. Table 1. Astragaloside A Content Detection Table As can be seen from Table 1, the lack of soaking in color-protecting liquid and preservation coating liquid in Comparative Example 1 resulted in incomplete inactivation of apple polyphenol oxidase, and the non-enzymatic color reaction between astragalus flavonoids and apple polysaccharides was weak. The finished product showed moderate browning, dull color, and poor appearance quality.

[0032] In Comparative Example 2, which did not undergo steam explosion, the apple slices were dense native tissue without micron-level interconnected pores. Astragaloside A could only adhere to the surface and could not penetrate deeply. The apple tissue was not softened by steam explosion, resulting in insufficient release of natural fructose, which could not fully blend with the sweetness of astragalus. The bitterness of astragalus remained strong, and the apple had a noticeable sour and astringent taste, making it extremely unacceptable to consumers. Without steam explosion and without pretreatment to build pores, the hot steam could not uniformly deactivate polyphenol oxidase, resulting in a violent browning reaction. The finished product was dark and dull, lacking a uniform and oily amber appearance. The apple tissue fibers were firm, and the texture was hard and crisp, lacking the loose texture of pre-made dried apples.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing apple slices with high astragalus content using a circulating steaming and drying process, characterized in that, Includes the following steps: Step 1: Soak apple slices in color-protecting solution and then transfer them to preservative coating solution for further soaking to obtain pre-treated apple slices; Step 2: The pre-treated apple slices are subjected to steam explosion treatment to obtain pre-made dried apples; Step 3: Place the pre-made dried apples in a porcelain evaporating dish, and then perform three steaming and drying processes. Add astragalus and purified water before each steaming and drying process to obtain dried apples with high astragalus content, thus completing the method of preparing dried apples with high astragalus content by cyclic steaming and drying. The steaming and drying process includes steaming and drying, with the steaming temperature being 100-105℃ and the drying temperature being 50-60℃.

2. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 1, characterized in that, The finished product of the high-astragalus-content dried apple has a moisture content of ≤12% and an astragaloside A content of ≥0.290%.

3. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 1, characterized in that, The specific preparation steps for the pretreated apple slices are as follows: Core ripe apples with a firm texture and fructose content ≥12% and cut them into slices 2-4 cm thick. Soak the apple slices in a color-protecting solution containing 0.4-0.6% citric acid and 0.4-0.6% calcium chloride for 3-4 hours, then transfer them to a preservative coating solution and soak for 20-30 minutes. After soaking, refrigerate at 4-5℃ for 1-2 hours and dry at 50-60℃ until the moisture content is 25-30% to obtain pretreated apple slices.

4. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 3, characterized in that, The preservative coating liquid consists of 3-4% agar powder, 6-8% hydroxypropyl distarch phosphate and 6-8% xylitol, with the remainder being purified water at 70-80℃.

5. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 1, characterized in that, The specific preparation steps for the pre-made dried apples are as follows: The pre-treated apple slices are transferred to a steam explosion device and steam-exploded for 120-140 seconds. Then they are placed in an oven and dried at 50-60℃ until the moisture content is ≤20%, thus obtaining pre-dried apples.

6. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 5, characterized in that, The steam explosion treatment has a pressure of 0.8-1.0 MPa and a temperature of 170-178℃.

7. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 1, characterized in that, The specific preparation steps for the high-astragalus-content dried apples are as follows: After rinsing the astragalus root 2-4 times with clean water, place it together with the pre-made dried apples in a porcelain evaporating dish. Then add purified water and steam at 100-105℃ for 20-22 minutes to initially release the water-soluble components of the astragalus root and allow them to be absorbed by the pre-made dried apples. After steaming, separate the astragalus root residue. Dry the pre-made dried apples at 50-60℃ at a low temperature until the surface is slightly dry. Then add the astragalus root and purified water and steam at 100-105℃ for 14-16 minutes to promote deep penetration. Separate the astragalus root residue and dry at 50-60℃ at a low temperature for a second time. Add the astragalus root and purified water again and steam at 100-105℃ for a third time for 10-12 minutes to stimulate aroma and complete component integration. Separate the astragalus root residue and dry at 50-60℃ at a low temperature for a third time to obtain dried apples with high astragalus root content.

8. The method for preparing high-astragalus-content dried apples using a circulating steaming and drying method according to claim 7, characterized in that, The mass ratio of Astragalus membranaceus, pre-processed dried apple, and purified water is 48-54:130-140:720-850.

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