Instant three-steaming and three-air-drying jujubes and processing technology thereof

Abstract

The application discloses instant three-steaming and three-airing Chinese dates and a processing technology thereof, and belongs to the technical field of food processing. The technology comprises the following steps: gradient variable-temperature segmented steaming of pretreated red dates, low-temperature preheating, medium-temperature penetration and high-temperature curing in sequence; then, moisture control and slow recovery are carried out to make the moisture homogenized; then, microwave-hot air coupling drying is carried out; and the above steps are repeated at least once, so that the instant three-steaming and three-airing Chinese dates are obtained. The application avoids excessive damage to nutrients through gradient variable-temperature steaming, and combines moisture control, slow recovery and microwave-hot air coupling drying, so that the processing period is greatly shortened to 8-12 hours, the retention rate of vitamin C reaches 65%-75%, the date peel is fully softened and easy to digest, the product quality is stable, and the whole-year continuous industrialized production can be realized. The instant three-steaming and three-airing Chinese dates prepared by the application are rich in nutrients, soft and glutinous in taste, convenient to eat, and have excellent industrialization prospect.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a ready-to-eat three-steamed and three-dried jujube and its processing technology. Background Technology

[0002] Jujubes, a traditional Chinese food and medicine, are popular among consumers for their health benefits, including tonifying the spleen and stomach, nourishing blood, and calming the mind. However, traditional methods of consuming jujubes have many limitations. Fresh jujubes are extremely prone to spoilage after harvesting, with a very short shelf life. While dried jujubes have a longer shelf life, they have a rough texture, hard skin that is difficult to digest, and direct consumption can easily cause discomfort such as internal heat.

[0003] To improve the taste and digestibility of dried dates, a "three-steaming, three-drying" processing method emerged in the traditional processing industry. According to existing literature and publicly available information, this traditional process typically involves: washing the dried dates and then steaming them for a first time, ranging from 20-30 minutes to several hours (for example, some records mention "steaming for 3 hours at a time" or "steaming over high heat for 25 minutes"). Then, they are naturally sun-dried for a period ranging from one hour to several days. This steaming-drying process is repeated three times, ultimately resulting in soft, sweet, and fragrant steamed dates. In industrial production, some companies have introduced temperature and humidity control rooms to achieve precise control of temperature and humidity during the drying process. However, this essentially still follows the basic "steaming-drying" framework and fails to fundamentally overcome the technical limitations of the traditional method.

[0004] Analysis reveals the following significant shortcomings in the existing three-steaming and three-drying jujube processing technology: (a) Poor nutrient retention In traditional processing methods, prolonged high-temperature steaming (often exceeding 30 minutes, even up to 3 hours) causes significant damage to heat-sensitive nutrients in jujubes, such as vitamin C and cyclic adenosine monophosphate. Food science research shows that vitamin C can be lost by more than 50% after heating at 80℃ for 30 minutes. Furthermore, during natural sun-drying, jujubes are exposed to air for extended periods, making them susceptible to dust and microbial contamination, and also leading to oxidation reactions that result in a significant loss of antioxidant active ingredients (such as flavonoids and polyphenols). Therefore, steamed jujubes produced using traditional methods have a significantly lower nutritional value than fresh or dried jujubes.

[0005] (ii) Long production cycle and low efficiency Traditional methods rely on natural sun-drying, which takes anywhere from 4 hours to 5 days per drying cycle, with the entire process involving three steaming and three drying cycles lasting 15-30 days. This process is entirely dependent on weather conditions; drying cannot be carried out on rainy days, and it easily leads to mold and spoilage of the dates, resulting in unstable quality. Even though some companies use temperature and humidity control chambers, the production cycle remains long due to a lack of systematic optimization of the steaming and drying (or tempering) parameters. This limits equipment utilization and capacity, making it difficult to achieve efficient and continuous industrial production.

[0006] (iii) Unstable product quality and low degree of standardization Traditional three-steaming and three-drying processes rely heavily on the operator's experience and judgment, lacking a scientific parameter control system. This results in significant variations in moisture content, firmness, and color between different batches of products (with a coefficient of variation often reaching 15%-20%). Problems such as over-steaming leading to sourness and bitterness, or uneven drying causing some dates to be too hard while others are too soft, are easily encountered. This quality instability severely hinders the product's branding and market promotion.

[0007] (iv) Poor eating experience, difficulty in digesting jujube skin Although the jujube skin softens after being steamed and sun-dried three times, the cellulose structure within the skin is not fully destroyed under traditional processing methods. For people with weak spleens and stomachs or poor digestion, consuming these jujubes may still cause bloating and indigestion. While removing the skin and pits can solve digestive issues, it results in the loss of nutrients such as iron and flavonoids found in the jujube skin, making it a counterproductive process.

[0008] In conclusion, developing a three-steaming and three-drying jujube processing technology that can efficiently retain the nutrients of jujubes, significantly shorten the production cycle, ensure stable product quality, and fully soften the jujube skin to improve digestibility has significant technical value and market application prospects. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a ready-to-eat three-steamed and three-dried jujube and its processing technology.

[0010] To achieve the aforementioned objective, the technical solution of the present invention is implemented as follows: a processing technology for ready-to-eat jujubes that are steamed and dried three times includes the following steps: raw material pretreatment, three-cycle "gradient temperature segmented steaming-humidity controlled tempering-microwave-hot air coupled drying" treatment, and cooling and packaging.

[0011] Specifically, the process includes the following steps: (1) Raw material pretreatment: Select red dates with uniform maturity and free from pests and diseases, and then wash, pit, and grade them for later use.

[0012] (2) First loop processing: (a) First gradient temperature segmented steaming: The pretreated jujubes are steamed in three stages with varying temperatures, namely, low temperature preheating stage, medium temperature penetration stage and high temperature ripening stage. (b) First humidity-controlled restorative process: The steamed jujubes are placed in a temperature- and humidity-controlled environment for moisture homogenization treatment; (c) First microwave-hot air coupled drying: The jujubes after thawing are dried by microwave and hot air in combination until the predetermined moisture content is reached.

[0013] (3) Second cycle processing: Repeat steps (a) to (c) in (2), and adjust the process parameters according to the moisture content.

[0014] (4) Third cycle processing: Repeat steps (a) to (c) in (2) and dry until the moisture content of the final product is 15%-22%.

[0015] (5) Cooling and packaging: Cool the dried red dates to room temperature and then vacuum or nitrogen-filled package them.

[0016] As a preferred technical solution, the parameters for the gradient temperature-segmented steaming process are as follows: low-temperature preheating section temperature 50-60℃, time 5-15 minutes; medium-temperature permeation section temperature 70-80℃, time 5-15 minutes; high-temperature cooking section temperature 90-95℃, time 5-15 minutes. The preferred heating rate is 1-3℃ / minute.

[0017] As a preferred technical solution, the parameters for the humidity control and tempering process are: temperature 20-30℃, relative humidity 60%-75%, air velocity 0.3-0.8m / s, and tempering time 30-90 minutes.

[0018] As a preferred technical solution, the parameters for microwave-hot air coupled drying are: microwave power density 1.5-3.5W / g, hot air temperature 40-60℃, air velocity 1.0-2.0m / s, and drying time 10-30 minutes. Intermittent microwave heating is preferred, such as pausing for 0.5-1 minute after every 1-3 minutes of heating.

[0019] As a preferred technical solution, the steaming temperature, tempering humidity, and drying power density decrease in the three-cycle treatment.

[0020] This invention also protects a ready-to-eat three-steamed and three-dried jujube prepared using any of the above-mentioned processes. The ready-to-eat three-steamed and three-dried jujube has a moisture content of 15%-22%, a vitamin C retention rate of ≥60%, and a skin softening degree of ≥80%.

[0021] The beneficial effects of this invention are reflected in: Firstly, regarding nutrient retention, this invention employs a gradient temperature-controlled segmented steaming technology, avoiding the continuous damage to heat-sensitive components caused by traditional constant-temperature, long-duration high-temperature steaming. Combined with microwave-hot-air coupled drying, the heat treatment time is significantly shortened, resulting in a vitamin C retention rate of 65%-75%, far exceeding the 30%-40% of traditional processes. The cyclic adenosine monophosphate (cAMP) content is 80%-85% of that in fresh dates, compared to only 50%-60% in traditional processes. The retention rates of total flavonoids and total polyphenols are increased by more than 40% and 35% respectively compared to traditional processes. Secondly, in terms of production efficiency, this invention replaces natural sun-drying with humidity-controlled tempering and microwave-hot-air coupled drying, drastically reducing the entire processing cycle from 15-30 days in traditional processes to 8-12 hours, increasing production efficiency by more than 30 times. Furthermore, it is not limited by weather conditions, enabling continuous industrial production throughout the year, and the overall energy consumption per unit product is reduced by more than 50% compared to traditional processes. Third, regarding product quality standardization, this invention establishes a complete intelligent control system for process parameters. The coefficients of variation for indicators such as moisture content, color, and texture of different batches of products are all less than 5%, far superior to the 15%-20% of traditional processes. This avoids problems such as "outer ripeness and inner stagnation" or surface hardening, resulting in a uniform and consistent product texture. Fourth, regarding the eating experience and digestibility, the synergistic effect of gradient temperature steaming and moisture-controlled slow tempering fully softens the cellulose structure of the jujube peel without causing it to fall off. The jujube peel's tearing force is reduced by 65%-75% compared to traditional dried jujubes and by 30%-40% compared to traditional three-steaming and three-drying jujubes. The incidence of adverse reactions such as bloating after consumption by those with weak spleen and stomach is reduced by more than 80%. The product is moderately soft and glutinous, with a unique caramel and fruity aroma, and its sensory score is significantly better than that of commercially available traditional products. Fifth, regarding microbial safety and storage stability, the thermal and non-thermal effects of microwaves effectively kill microorganisms. The total bacterial count of the product is <100 CFU / g, coliform bacteria <10 CFU / g, and molds and yeasts were not detected, meeting the food safety standards for ready-to-eat foods. With vacuum or nitrogen-filled packaging, the product can be stored at room temperature for more than 12 months, while products processed using traditional methods are prone to mold or spoilage after only 3-6 months at room temperature. Sixth, in terms of industrialization and economic benefits, the equipment used in this process is mature, easy to automate, and has low operational difficulty. Based on a production line with an annual output of 1000 tons, the estimated annual output value can reach over 50 million yuan, with an investment payback period of approximately 2-3 years. In summary, this invention has achieved significant technological progress in multiple dimensions, including nutrient retention, production efficiency, product quality, edible experience, safety, and industrialization, and has outstanding substantive features and significant advancements compared to existing technologies. Attached Figure Description

[0022] In the attached diagram: Figure 1 The flowchart of the processing technology for ready-to-eat jujubes that are steamed and dried three times is provided in Embodiment 1 of the present invention.

[0023] Figure 2This is a schematic diagram of the temperature control curve in the gradient temperature steaming process of Embodiment 1 of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, and not all of them. Unless otherwise specified, the embodiments and features described in this application can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] It should be noted that if the embodiments of the invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0026] Furthermore, "multiple" refers to two or more. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the invention.

[0027] Example 1: Processing of Xinjiang Grey Dates This embodiment provides a processing technology for ready-to-eat jujubes that are steamed and dried three times. The raw material is Xinjiang grey jujubes, and the target product has a moisture content of 18%-22%.

[0028] 1. Raw material pretreatment Select Xinjiang grey dates that are uniformly ripe and free from pests and diseases, and wash them with clean water to remove surface impurities. Use a pitting machine to remove the pits, keeping the date flesh intact. Grade the pitted dates according to size into three grades: large (≥15g), medium (10-15g), and small (<10g). This example uses the medium grade as an example.

[0029] 2. First loop processing (1) First gradient temperature segmented steaming: The graded red dates are laid out in a single layer on a steaming tray and placed in a gradient temperature steaming device. The steaming program is set as follows: Low-temperature preheating section: Heat to 55°C at a rate of 2°C / minute and hold for 10 minutes.

[0030] Medium-temperature permeation section: Heat to 75°C at a rate of 2°C / min and hold for 15 minutes.

[0031] High-temperature curing section: Heat to 92°C at a rate of 2°C / minute and hold for 8 minutes.

[0032] Maintain a relative humidity of over 95% during the steaming process.

[0033] (2) First moisture control and slow recovery: The steamed dates were quickly transferred to a humidity-controlled tempering room with the following parameters: temperature 25℃, relative humidity 70%, air velocity 0.5m / s, and tempering time 90 minutes. Dynamic humidity control was used: humidity was 75% for the first 30 minutes, then decreased to 70% for the middle 30 minutes, and finally decreased to 65% for the last 30 minutes.

[0034] (3) First microwave-hot air coupled drying: After the jujubes have softened, place them in a microwave-hot air coupled drying device. The parameters are set as follows: microwave power density 3W / g, hot air temperature 55℃, and air velocity 1.5m / s. Intermittent heating is used: heat for 2 minutes, pause for 30 seconds, for a total effective drying time of 25 minutes. Turn the jujubes over every 5 minutes. Dry until the moisture content of the jujubes drops to 35%-40%.

[0035] 3. Second loop processing (1) Second gradient temperature segmented steaming: The parameters were adjusted as follows: low temperature range 60℃ / 8 minutes, medium temperature range 78℃ / 12 minutes, high temperature range 90℃ / 6 minutes. The heating rate remained unchanged.

[0036] (2) Second moisture control and slow recovery: The parameters were adjusted to: temperature 25℃, relative humidity 65%, and time 60 minutes.

[0037] (3) Second microwave-hot air coupled drying: The parameters were adjusted as follows: microwave power density 2.5W / g, hot air temperature 50℃, intermittent heating (heating for 2 minutes / pausing for 30 seconds), total drying time 20 minutes. Dry until the moisture content is 25%-30%.

[0038] 4. Third loop processing (1) Third gradient temperature segmented steaming: The parameters were adjusted as follows: low temperature range 62℃ / 6 minutes, medium temperature range 80℃ / 10 minutes, and high temperature range 88℃ / 5 minutes.

[0039] (2) Third moisture control and slow recovery: The parameters were adjusted to: temperature 25℃, relative humidity 60%, and time 45 minutes.

[0040] (3) Third microwave-hot air coupled drying: The parameters were adjusted as follows: microwave power density 2W / g, hot air temperature 45℃, intermittent heating, and total drying time 15 minutes. The product was dried to a final moisture content of 18%-22%.

[0041] 5. Cooling packaging The dried red dates are placed in a cooling room and cooled to room temperature at 15℃ and 50% relative humidity. They are then vacuum-packed, with each bag containing 200g.

[0042] Example 2: Processing of Shandong Golden Silk Jujubes This embodiment provides another processing technology for ready-to-eat jujubes that are steamed and dried three times. The raw material is Shandong golden silk jujubes, and the target product has a moisture content of 15%-18%, which is suitable for long-term storage.

[0043] The process is basically the same as in Example 1, except that the process parameters are adjusted to suit the small size and dense flesh of the jujube, as follows: First cycle: Microwave drying time reduced to 20 minutes, drying to a moisture content of 30%-35%.

[0044] Second cycle: Steaming: Low temperature section 60℃ / 6 minutes, medium temperature section 78℃ / 10 minutes, high temperature section 90℃ / 5 minutes.

[0045] Slow recovery: Temperature 25℃, relative humidity 65%, air velocity increased to 0.8m / s, time 50 minutes.

[0046] Drying: Microwave power density 2.5W / g, hot air temperature 50℃, time 18 minutes, dry to moisture content 22%-25%.

[0047] Third cycle: Steaming: Low temperature section 62℃ / 5 minutes, medium temperature section 80℃ / 8 minutes, high temperature section 88℃ / 4 minutes.

[0048] Warming-up: Temperature 25℃, relative humidity 60%, time 40 minutes.

[0049] Drying: Microwave power density 2W / g, hot air temperature 45℃, time 12 minutes, dry to the final moisture content 15%-18%.

[0050] Microwave drying strategy: Use a lower microwave power density (1.8-2.2W / g) to avoid surface overheating.

[0051] Product performance testing The performance of the jujubes prepared in Example 1 (steamed and dried three times) was tested: Vitamin C retention rate: determined by 2,6-dichlorophenolindophenol titration, the result was 68.5%.

[0052] Cyclic adenosine monophosphate (cAMP) content: determined by high performance liquid chromatography (HPLC), the result was 82.3% of the content in fresh jujubes.

[0053] Jujube skin softening: The results of the puncture test using a texture analyzer showed that the jujube skin breaking force was reduced by 65% ​​compared with traditional dried jujubes.

[0054] Sensory evaluation: A blind test was conducted on 20 randomly selected consumers. The product was significantly better than commercially available traditional three-steamed and three-dried dates in terms of softness, sweetness, aroma and overall acceptability.

[0055] The ready-to-eat three-steamed and three-drying jujubes and their processing technology provided by this invention have clear steps, controllable parameters, and mature equipment, enabling large-scale, standardized, and highly efficient industrial production. The resulting product retains good nutrition, has a superior taste and flavor, and is convenient to eat and easily digestible, possessing extremely high market promotion value and economic benefits.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A ready-to-eat type of jujube that is steamed and dried three times, and its processing technology, characterized in that... Includes the following steps: (a) The pretreated jujubes are subjected to a gradient temperature segmented steaming process, which includes a low temperature preheating stage, a medium temperature penetration stage and a high temperature ripening stage in sequence. (b) After steaming, the red dates are subjected to moisture control and slow resting to redistribute the internal moisture and achieve homogenization; (c) The jujubes after the thawing process are dried by microwave-hot air coupling; (d) Repeat steps (a) to (c) at least once to obtain ready-to-eat three-steamed and three-dried jujubes.

2. The ready-to-eat three-steamed and three-dried jujube and its processing technology according to claim 1, characterized in that, In step (d), steps (a) to (c) are repeated twice, that is, three steamings, three temperings and three dryings are performed.

3. The ready-to-eat three-steamed and three-dried jujube and its processing technology according to claim 1, characterized in that, The parameters for the gradient temperature segmented steaming process are as follows: the temperature of the low-temperature preheating stage is 50-60℃, the temperature of the medium-temperature penetration stage is 70-80℃, and the temperature of the high-temperature cooking stage is 90-95℃, with each stage lasting 5-15 minutes.

4. The ready-to-eat three-steamed and three-dried jujube and its processing technology according to claim 1, characterized in that, The conditions for humidity control and slow recovery are: temperature 20-30℃, relative humidity 60%-75%, and time 30-90 minutes.

5. The ready-to-eat three-steamed and three-dried jujube and its processing technology according to claim 1, characterized in that, The parameters for microwave-hot air coupled drying are: microwave power density 1.5-3.5W / g, hot air temperature 40-60℃, and drying time 10-30 minutes.

6. The ready-to-eat three-steamed and three-dried jujube and its processing technology according to claim 1, characterized in that, The microwave-hot air coupled drying process uses intermittent microwave heating.

7. The ready-to-eat three-steamed and three-dried jujube and its processing technology according to claim 1, characterized in that, The pretreatment includes cleaning, depitting, and grading steps.

8. A ready-to-eat type of jujube that is steamed and dried three times, characterized in that... It is prepared using the process described in any one of claims 1-7.

9. A ready-to-eat jujube that has undergone three steaming and three drying processes according to claim 8, characterized in that, Its moisture content is 15%-22%, and its vitamin C retention rate is ≥60%.

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