Anhydrous star anise pretreatment method

Abstract

The invention discloses an anhydrous star anise pretreatment method, and belongs to the technical field of food processing. Freezing treatment is an efficient basic pretreatment method, water resource consumption and pollution can be remarkably reduced, fixed asset investment of the seasonal star anise processing industry can be reduced, the processing period can be prolonged, and the method is suitable for large-scale industrial application. Freezing ultrahigh pressure treatment is used as a high-performance method, the color and flavor of the star anise are further optimized, active ingredients are reserved, and the method is suitable for deep processing of the star anise with higher quality requirements. The two methods can effectively destroy the cell structure of the star anise, improve the drying rate, promote the release of inclusions, remarkably improve the color stability of the dried star anise, avoid the problems that the quality of the star anise is destroyed by traditional hot water blanching and the energy consumption is too high, and improve the processing quality and additional value of the star anise. The method can be applied to processing and production of high-quality spices.

Description

Technical Field

[0001] The present invention relates to a method for pretreating star anise without water, belonging to the technical field of food processing. Background Art

[0002] As a spice crop with important economic value and broad application prospects, the processing quality of star anise has an important impact on the market competitiveness of products and directly affects the quality of the final products. In the processing of star anise, blanching is a crucial pretreatment process. The traditional hot water blanching method mainly inactivates the enzymes in star anise through short-time high-temperature treatment, while softening the tissue structure to facilitate subsequent drying or other processing. The traditional hot water blanching process has problems such as high energy consumption, serious nutrient loss, water pollution, and easy deterioration of color. Especially during the peak harvest season of star anise, the processing pressure is huge.

[0003] In order to improve the processing efficiency and product quality of star anise, developing a new pretreatment method that can effectively replace traditional hot water blanching has become a research hotspot.

[0004] Freezing can destroy the cell structure of star anise through the mechanical effect of low temperature and the crystallization of water, thereby enhancing the permeability of the cell wall. This process helps in the inactivation of enzymes and the extraction of active ingredients in subsequent processing steps, while maximizing the retention of its natural color and aroma. Ultra-high pressure treatment, by uniformly applying a pressure of up to 100 - 600 MPa, has a good protective effect on heat-sensitive substances such as volatile oils. In addition, ultra-high pressure can promote the uniform destruction of cell structure, improving the efficiency and uniformity of subsequent drying.

[0005] The combination of freezing and ultra-high pressure can not only further optimize the treatment effect of cell structure but also avoid the problem of quality deterioration caused by high-temperature treatment. For example, the combination of freezing and ultra-high pressure can significantly reduce the impact of blanching on the color of star anise, more effectively destroy the cell structure, improve the drying rate while maintaining its unique flavor components. Freezing treatment and freezing-ultra-high pressure treatment provide efficient and low-loss non-thermal blanching solutions, where freezing treatment is suitable for large-scale production, while freezing-ultra-high pressure treatment is suitable for the deep processing of high-value-added products.

[0006] Luo Yun (2024) et al. disclosed a device for removing green parts in star anise processing, specifically related to the field of star anise processing, including a blanching tank. A heating component is arranged inside the blanching tank to heat the clear water inside; a placement tray is arranged inside the blanching tank, and the outer diameter size of the placement tray is the same as the inner diameter size of the blanching tank. A lifting component is arranged at the center inside the blanching tank to lift and adjust the placement tray inside the blanching tank through the lifting component. In the present invention, by setting the placement tray, during the processing, the star anise is put into the placement tray, and the placement tray is put into the blanching tank through the lifting component, and steamed with the clear water inside. During the steaming process, the star anise can be stirred through the stirring component to ensure the steaming effect of the star anise. After steaming, the star anise is fished out completely through the placement tray, which is convenient and fast and easy to control the steaming time. However, this technology still relies on traditional hot water blanching, and its high-temperature treatment process is prone to cause the loss of thermosensitive components in star anise, such as the volatilization of volatile oils and aromatic substances, and at the same time, it will also cause quality deterioration problems such as dull color and loss of nutrients. In addition, the control of the steaming time is affected by the heat conduction efficiency and batch differences, it is difficult to achieve the consistency and standardization of quality, and the energy consumption is high, which is not conducive to the requirements of green and low-carbon processing. In order to improve the processing efficiency and product quality of star anise, developing a new pretreatment method that can effectively replace traditional hot water blanching has become a research hotspot. Summary of the Invention

[0007] Based on the simple and efficient freezing treatment and the high-performance characteristics of ultra-high pressure technology, the present invention proposes a flexible combined blanching method, which not only meets the needs of industrial production but also satisfies the deep processing requirements of high-quality star anise products. The freezing treatment destroys the cell walls of star anise by physical means, improving color stability; the freeze-ultra-high pressure treatment further optimizes the color, more thoroughly destroys the cell structure, and improves the drying rate. This technology not only provides an innovative idea for star anise processing but also provides a reference for the pretreatment of other thermosensitive plant raw materials, and is expected to be widely used in the future food processing industry.

[0008] A method for pretreating star anise without water includes the following steps:

[0009] (1) Freezing treatment: Place the fresh star anise in an environment of -18°C to -25°C for freezing treatment until it is completely frozen;

[0010] (2) Thawing: Thaw the star anise after freezing treatment;

[0011] (3) Ultra-high pressure treatment: Place the thawed star anise in a sealed ultra-high pressure device and apply a pressure of 200 - 600 MPa for ultra-high pressure treatment;

[0012] (4) Subsequent treatment: Drying.

[0013] Further, in the step (1), the freezing time is 4 - 12 hours.

[0014] Further, in the step (2), the thawing method is natural thawing or rapid thawing. The temperature for natural thawing is 20 - 25°C, and the temperature for rapid thawing is 40 - 50°C.

[0015] Further, in the step (3), the ultra-high pressure treatment time is 5 - 15 minutes, and the temperature for ultra-high pressure treatment is 15 - 30°C.

[0016] Further, in the step (4), the drying temperature is 55°C - 70°C, and the drying time is 12 - 16 hours.

[0017] Advantages of the present invention: The freezing treatment of the present invention can be used alone as a blanching process for the primary processing of star anise on an industrial scale, and is suitable for energy-saving and efficient mass production. The ultra-high pressure treatment of the present invention is preferably used in scenarios where high-quality star anise products are required, such as the production of high-end extracts and fine spices. During the ultra-high pressure treatment, the star anise is kept in a sealed state to prevent material loss, odor volatilization, and contamination. Description of the Drawings

[0018] Figure 1 It is a graph of the dry basis moisture content of fresh star anise, Example 1, Comparative Example 1, and Comparative Example 2 after drying.

[0019] Figure 2 It is a graph of the nuclear magnetic moisture change of fresh star anise, Example 1, Comparative Example 1, and Comparative Example 2 after drying.

[0020] Figure 3 It is a graph of the optical microscope and scanning electron microscope (SEM) of fresh star anise, Example 1, Comparative Example 1, and Comparative Example 2 after drying, where A is the optical microscope graph and B is the scanning electron microscope graph.

[0021] Figure 4 It is the change in the appearance color of fresh star anise, Example 1, Comparative Example 1, and Comparative Example 2 after drying.

[0022] Figure 5 It is the change in the appearance color of fresh star anise, Example 1, Comparative Example 1, and Comparative Example 2 after drying. Detailed Embodiments

[0023] The technical solutions of the present invention are further described below according to the embodiments and the drawings.

[0024] Example 1

[0025] The freshly harvested star anise is placed in a -20°C cold storage for 8 hours, and the frozen star anise is sealed for thawing. After natural thawing is completed, it is put into a sealed ultra-high pressure device and subjected to ultra-high pressure treatment under the conditions of 600 MPa, 25°C, and 10 min. Then it is put into a heat pump dryer and dried at 60°C for 12 hours, and the quality is measured before and after the two pretreatments and after drying respectively.

[0026] Comparative Example 1

[0027] The freshly harvested star anise is placed in a -20°C cold storage for 8 hours, and the frozen star anise is sealed for thawing. The thawed sample is directly put into a heat pump drying device without ultra-high pressure treatment and dried at 60°C for 12 hours.

[0028] Comparative Example 2

[0029] The freshly harvested star anise is first blanched in 90°C hot water for 6 minutes and then cooled to room temperature. The treated sample is placed in a heat pump drying device and dried at 60°C for 12 hours.

[0030] As Figure 1 shown, the drying rate of the freshly harvested star anise and the hot water blanching of Comparative Example 2 is slower, probably because the cell structure remains relatively intact and the resistance to water migration is greater. The freezing of Comparative Example 1 and the freezing combined with ultra-high pressure treatment of Example 1 significantly accelerate the drying rate of star anise, indicating that the freezing treatment destroys the cell wall structure and improves the water migration rate. Among them, the freezing combined with ultra-high pressure has a faster drying rate than the freezing treatment and the best effect, because the ultra-high pressure further destroys the cell structure and improves the internal water migration efficiency.

[0031] As Figure 2 shown, compared with the freshly harvested star anise, the free water content of the hot water blanching of Comparative Example 2 increases, and the influence on the water state is limited. It mainly reduces the free water, and the distribution change of the weakly bound water is not significant. The freezing treatment in Comparative Example 1 has a significant effect on the free water and the weakly bound water. It may be because the formation of ice crystals destroys the cell structure and releases more free water. In Example 1, the freezing combined with ultra-high pressure has the lowest peak value of free water, and the signal intensity of the weakly bound water is more concentrated, indicating that the water state is further changed and the cell wall and internal binding are more fragmented. The drying efficiency can be improved by freezing the drying water. The nuclear magnetic resonance data shows that the freezing treatment can effectively release free water and reduce the drying resistance.

[0032] As Figure 3As can be seen from Figure A in [reference], the cells of fresh star anise are intact with clear cell walls and numerous intact intercellular spaces. The cell contents are evenly distributed without being disturbed by external treatments. In Comparative Example 2, the cell walls after hot water blanching show a certain degree of collapse and the intercellular spaces are reduced. The hot water blanching causes partial damage to the cell walls, but the effect is limited, probably because the hot blanching fails to penetrate deep into the cells. The cell structure is significantly damaged, the cell walls collapse significantly, and the intercellular spaces increase. In Comparative Example 1, the ice crystals formed by freezing cause mechanical damage to the cell walls, promoting the release of cell contents. The degree of cell wall damage is further aggravated, and some cell walls are broken and collapsed. In Example 1, the combined action of freezing and ultra-high pressure significantly damages the cell wall structure, which is beneficial to subsequent water migration and the release of active ingredients.

[0033] As Figure 3 As can be seen from Figure B in [reference], the surface structure of fresh star anise is intact with fewer micropores and a dense structure. The cells are arranged regularly, indicating that water migration is relatively difficult. In Comparative Example 2, the micropore structure after hot water blanching increases to some extent, but the overall structure is still relatively dense. The effect of hot water treatment on the cell walls is relatively superficial and fails to cause deep damage. In Comparative Example 1, the freezing treatment significantly increases the number and size of micropores, and cell wall rupture is relatively common. The mechanical damage of ice crystals to the cells makes the internal structure more porous, which is beneficial to water diffusion. In Example 1, the number of micropores is the largest and the pore size is the largest after freezing combined with ultra-high pressure, and the cell wall damage is the most serious, showing a significant porous network structure. The ultra-high pressure treatment further enhances the damage effect of freezing, forming a more open internal channel to provide a pathway for water migration and the release of active ingredients. The degree of cell structure damage: freezing + ultra-high pressure treatment > freezing > hot water blanching > fresh star anise. Freezing + ultra-high pressure significantly damages the cell walls, forming a porous network structure, which is most beneficial to water migration and the release of active ingredients.

[0034] From Figure 4 it can be seen that the redness of star anise after hot water blanching in Comparative Example 2 decreases significantly, while the star anise after freezing in Comparative Example 1 appears redder to the naked eye. This shows that hot water blanching will damage the color quality of star anise. The star anise particles in Example 1 with freezing + ultra-high pressure are the plumpest, followed by those with freezing. The darker the color, the more the cell structure is damaged, and the more the total flavonoid content flows out, making the formation of brown polymers more obvious. The color difference measurement also corresponds well with the results. The a * value reflects the redness value, and the redness value is also the most important factor in evaluating the quality of star anise. As shown in the figure, the star anise after freezing and freezing combined with ultra-high pressure shows the best red color (the highest a * value) after drying, and the color difference (ΔE) of the star anise after freezing treatment and freezing + ultra-high pressure treatment is smaller, and the quality is better. While the star anise after hot water blanching is yellower (b *), with worse quality. Therefore, the star anise blanching technology can be replaced by freezing technology and freeze ultra-high pressure to achieve better star anise quality.

[0035] Example 2

[0036] The specific operation is the same as that of Example 1, except that the freezing time is changed from 8 hours to 4 hours, and the rest of the steps remain the same, to investigate the effect of shortening the freezing time on the quality of star anise.

[0037] Example 3

[0038] The specific operation is the same as that of Example 1, except that the freezing time is changed from 8 hours to 12 hours, and the rest of the steps remain the same, to investigate the effect of shortening the freezing time on the quality of star anise.

[0039] Example 4

[0040] The specific operation is the same as that of Example 1, except that the heat pump drying temperature is adjusted from 60 °C to 55 °C, and the drying time is correspondingly extended to 16 hours, to evaluate the effect of a lower drying temperature on quality retention.

Claims

1. A method for pretreating anhydrous star anise, characterized in that, It includes the following steps: (1) Freezing treatment: Place fresh star anises in an environment of -18°C to -25°C for freezing treatment until they are completely frozen; (2) Thawing: Hermetically thaw the star anises after freezing treatment; (3) Ultra-high pressure treatment: Place the thawed star anises in a sealed ultra-high pressure device and apply a pressure of 200 - 600 MPa for ultra-high pressure treatment; (4) Subsequent treatment: Drying or extraction.

2. The anhydrous star anise pretreatment method according to claim 1, wherein In the step (1), the freezing time is 4 - 12 hours.

3. A method for pre-treating anhydrous star anise according to claim 1, characterized in that, In the step (2), the thawing method is natural thawing or rapid thawing. The temperature for natural thawing is 20 - 25°C, and the temperature for rapid thawing is 40 - 50°C.

4. A method for pretreating anhydrous star anise according to claim 1, characterized in that, In the step (3), the ultra-high pressure treatment time is 5 - 15 minutes, and the temperature for ultra-high pressure treatment is 15 - 30°C.

5. A method for pretreating anhydrous star anise according to claim 1, characterized in that, In the step (4), the drying temperature is 55 - 70°C, and the drying time is 12 - 16 hours.

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